< draft-ietf-pana-pana-01.txt   draft-ietf-pana-pana-02.txt >
PANA Working Group PANA Working Group D. Forsberg
Internet Draft D. Forsberg Internet-Draft Nokia
Nokia Expires: April 23, 2004 Y. Ohba
Y. Ohba
Toshiba Toshiba
B. Patil B. Patil
Nokia Nokia
H. Tschofenig H. Tschofenig
Siemens Siemens
A. Yegin A. Yegin
DoCoMo USA Labs DoCoMo USA Labs
Document: draft-ietf-pana-pana-01.txt October 24, 2003
Expires: December 2003 June 2003
Protocol for Carrying Authentication for Network Access (PANA) Protocol for Carrying Authentication for Network Access (PANA)
<draft-ietf-pana-pana-01.txt> draft-ietf-pana-pana-02
Status of this Memo Status of this Memo
This document is an Internet-Draft and is subject to all provisions This document is an Internet-Draft and is in full conformance with
of Section 10 of RFC2026. all provisions of Section 10 of RFC2026.
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Copyright Notice
Copyright (C) The Internet Society (2003). All Rights Reserved.
Abstract Abstract
This document defines the Protocol for Carrying Authentication for This document defines the Protocol for Carrying Authentication for
Network Access (PANA), a link-layer agnostic transport for Network Access (PANA), a link-layer agnostic transport for Extensible
Extensible Authentication Protocol (EAP) to enable network access Authentication Protocol (EAP) to enable network access authentication
authentication between clients and access networks. PANA can carry between clients and access networks. PANA can carry any
any authentication method that can be specified as an EAP method, authentication method that can be specified as an EAP method, and can
and can be used on any link that can carry IP. PANA covers the be used on any link that can carry IP. PANA covers the
client-to-network access authentication part of an overall secure client-to-network access authentication part of an overall secure
network access framework, which additionally includes other network access framework, which additionally includes other protocols
protocols and mechanisms for service provisioning, access control as and mechanisms for service provisioning, access control as a result
a result of initial authentication, and accounting. of initial authentication, and accounting.
Table of Contents Table of Contents
1 Introduction..................................................3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . 4
2 Terminology...................................................4 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 5
3 Protocol Overview.............................................5 3. Protocol Overview . . . . . . . . . . . . . . . . . . . . 6
4 Protocol Details..............................................6 4. Protocol Details . . . . . . . . . . . . . . . . . . . . . 8
4.1 Common Processing Rules.................................6 4.1 Common Processing Rules . . . . . . . . . . . . . . . . . 8
4.2 Discovery and Initial Handshake Phase..................10 4.1.1 Payload Encoding . . . . . . . . . . . . . . . . . . . . . 8
4.3 Authentication Phase...................................12 4.1.2 Transport Layer Protocol . . . . . . . . . . . . . . . . . 8
4.4 Re-authentication......................................14 4.1.3 Fragmentation . . . . . . . . . . . . . . . . . . . . . . 9
4.5 Termination Phase......................................16 4.1.4 Sequence Number and Retransmission . . . . . . . . . . . . 9
4.6 Illustration of a Complete Message Sequence............16 4.1.5 PANA Security Association . . . . . . . . . . . . . . . . 10
4.7 Device ID choice.......................................18 4.1.6 Message Authentication Code . . . . . . . . . . . . . . . 11
4.8 Refresh Interval Negotiation...........................18 4.1.7 Message Validity Check . . . . . . . . . . . . . . . . . . 11
4.9 Mobility Handling......................................19 4.1.8 Error Handling . . . . . . . . . . . . . . . . . . . . . . 12
4.10 Event Notification...................................19 4.2 Discovery and Initial Handshake Phase . . . . . . . . . . 12
4.11 PaC Implications.....................................20 4.3 Authentication Phase when PANA-PAA-Discover is sent by
4.12 PAA Implications.....................................20 EP . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
5 PANA Security Association Establishment......................20 4.4 Re-authentication . . . . . . . . . . . . . . . . . . . . 17
6 Authentication Method Choice.................................21 4.5 Termination Phase . . . . . . . . . . . . . . . . . . . . 18
7 Filter Rule Installation.....................................21 4.6 Illustration of a Complete Message Sequence . . . . . . . 18
8 Data Traffic Protection......................................22 4.7 Device ID Choice . . . . . . . . . . . . . . . . . . . . . 20
9 Message Formats..............................................23 4.8 Session Lifetime . . . . . . . . . . . . . . . . . . . . . 20
9.1 PANA Header............................................23 4.9 Mobility Handling . . . . . . . . . . . . . . . . . . . . 21
9.2 AVP Header.............................................24 4.10 Event Notification . . . . . . . . . . . . . . . . . . . . 22
9.3 PANA Messages..........................................26 4.11 PaC Implications . . . . . . . . . . . . . . . . . . . . . 22
9.4 AVPs in PANA...........................................29 4.12 PAA Implications . . . . . . . . . . . . . . . . . . . . . 22
9.5 AVP Occurrence Table...................................32 5. PANA Security Association Establishment . . . . . . . . . 23
10 Security Considerations...................................33 6. Authentication Method Choice . . . . . . . . . . . . . . . 24
11 Open Issues...............................................39 7. Filter Rule Installation . . . . . . . . . . . . . . . . . 25
12 Acknowledgments...........................................39 8. Data Traffic Protection . . . . . . . . . . . . . . . . . 26
13 References................................................39 9. Message Formats . . . . . . . . . . . . . . . . . . . . . 27
Change History..................................................42 9.1 PANA Header . . . . . . . . . . . . . . . . . . . . . . . 27
Appendix A. Adding sequence number to PANA for carrying EAP....43 9.2 AVP Header . . . . . . . . . . . . . . . . . . . . . . . . 28
Full Copyright Statement........................................52 9.3 PANA Messages . . . . . . . . . . . . . . . . . . . . . . 30
9.3.1 Message Specifications . . . . . . . . . . . . . . . . . . 31
9.3.2 PANA-PAA-Discover (PDI) . . . . . . . . . . . . . . . . . 31
9.3.3 PANA-Start-Request (PSR) . . . . . . . . . . . . . . . . . 31
9.3.4 PANA-Start-Answer (PSA) . . . . . . . . . . . . . . . . . 31
9.3.5 PANA-Auth-Request (PAR) . . . . . . . . . . . . . . . . . 32
9.3.6 PANA-Auth-Answer (PAN) . . . . . . . . . . . . . . . . . . 32
9.3.7 PANA-Bind-Request (PBR) . . . . . . . . . . . . . . . . . 32
9.3.8 PANA-Bind-Answer (PBA) . . . . . . . . . . . . . . . . . . 33
9.3.9 PANA-Reauth-Request (PRAR) . . . . . . . . . . . . . . . . 33
9.3.10 PANA-Reauth-Answer (PRAA) . . . . . . . . . . . . . . . . 33
9.3.11 PANA-Termination-Request (PTR) . . . . . . . . . . . . . . 33
9.3.12 PANA-Termination-Answer (PTA) . . . . . . . . . . . . . . 34
9.3.13 PANA-Error (PER) . . . . . . . . . . . . . . . . . . . . . 34
9.4 AVPs in PANA . . . . . . . . . . . . . . . . . . . . . . . 34
9.4.1 MAC AVP . . . . . . . . . . . . . . . . . . . . . . . . . 34
9.4.2 Device-Id AVP . . . . . . . . . . . . . . . . . . . . . . 35
9.4.3 Session-Id AVP . . . . . . . . . . . . . . . . . . . . . . 35
9.4.4 Cookie AVP . . . . . . . . . . . . . . . . . . . . . . . . 35
9.4.5 Protection-Capability AVP . . . . . . . . . . . . . . . . 36
9.4.6 Termination-Cause AVP . . . . . . . . . . . . . . . . . . 36
9.4.7 Result-Code AVP . . . . . . . . . . . . . . . . . . . . . 36
9.4.8 EAP-Payload AVP . . . . . . . . . . . . . . . . . . . . . 39
9.4.9 Session-Lifetime AVP . . . . . . . . . . . . . . . . . . . 39
9.4.10 Failed-AVP AVP . . . . . . . . . . . . . . . . . . . . . . 39
9.4.11 NAP-Information AVP . . . . . . . . . . . . . . . . . . . 40
9.4.12 ISP-Information AVP . . . . . . . . . . . . . . . . . . . 40
9.4.13 Provider-Identifier AVP . . . . . . . . . . . . . . . . . 40
9.4.14 Provider-Name AVP . . . . . . . . . . . . . . . . . . . . 40
9.5 AVP Occurrence Table . . . . . . . . . . . . . . . . . . . 40
10. PANA Protocol Message Retransmissions . . . . . . . . . . 43
10.1 Transmission and Retransmission Parameters . . . . . . . . 45
11. Security Considerations . . . . . . . . . . . . . . . . . 46
12. Open Issues . . . . . . . . . . . . . . . . . . . . . . . 52
13. Change History . . . . . . . . . . . . . . . . . . . . . . 53
14. Acknowledgments . . . . . . . . . . . . . . . . . . . . . 54
Normative References . . . . . . . . . . . . . . . . . . . 55
Informative References . . . . . . . . . . . . . . . . . . 58
Authors' Addresses . . . . . . . . . . . . . . . . . . . . 59
A. Adding sequence number to PANA for carrying EAP . . . . . 61
A.1 Why is sequence number needed for PANA to carry EAP? . . . 61
A.2 Single sequence number approach . . . . . . . . . . . . . 62
A.2.1 Single sequence number with EAP retransmission method . . 62
A.2.2 Single sequence number with PANA-layer retransmission
method . . . . . . . . . . . . . . . . . . . . . . . . . . 63
A.3 Dual sequence number approach . . . . . . . . . . . . . . 66
A.3.1 Dual sequence number with orderly-delivery method . . . . 66
A.3.2 Dual sequence number with reliable-delivery method . . . . 68
A.3.3 Comparison of the dual sequence number methods . . . . . . 69
A.4 Consensus . . . . . . . . . . . . . . . . . . . . . . . . 69
Intellectual Property and Copyright Statements . . . . . . 70
1 Introduction 1. Introduction
Providing secure network access service requires access control Providing secure network access service requires access control based
based on the authentication and authorization of the clients and the on the authentication and authorization of the clients and the access
access networks. Initial and subsequent client-to-network networks. Initial and subsequent client-to-network authentication
authentication provides parameters that are needed to police the provides parameters that are needed to police the traffic flow
traffic flow through the enforcement points. A protocol is needed to through the enforcement points. A protocol is needed to carry
carry authentication methods between the client and the access authentication methods between the client and the access network.
network. IETF PANA Working Group has been chartered with the goal
of designing a network-layer access authentication protocol.
Link-layer authentication mechanisms are used as enablers of secure Currently there is no standard network-layer solution for
network access. A higher-layer authentication is deemed necessary authenticating clients for network access.
when link-layer authentication mechanisms are either not available [I-D.ietf-pana-usage-scenarios] describes the problem statement that
for lack of technology or deployment difficulties, or not able to led to the development of PANA.
meet the overall requirements, or when multi-layer (e.g., link-layer
and network-layer) authentication is needed. Currently there is no
standard network-layer solution for authenticating clients for
network access. In the absence of such a solution, some inadequate
standards-based solutions are deployed or non-standard ad-hoc
solutions are invented. [USAGE] describes the problem statement in
detail.
Scope of this working group is identified as designing a link-layer Scope of this working group is identified as designing a link-layer
agnostic transport for network access authentication methods. PANA agnostic transport for network access authentication methods. PANA
Working Group has identified EAP [RFC2284] as the payload for this Working Group has identified EAP [RFC2284] as the payload for this
protocol and carrier for authentication methods. In other words, protocol and carrier for authentication methods. In other words, PANA
PANA will carry EAP which can carry various authentication methods. will carry EAP which can carry various authentication methods. By
By the virtue of enabling transport of EAP above IP, any the virtue of enabling transport of EAP above IP, any authentication
authentication method that can be carried as an EAP method is method that can be carried as an EAP method is made available to PANA
made available to PANA and hence to any link-layer technology. There and hence to any link-layer technology. There is a clear division of
is a clear division of labor between PANA, EAP and EAP methods. labor between PANA, EAP and EAP methods.
Defining new authentication methods, or deriving/distributing keys
is outside the scope of PANA. Providing a secure channel that
protects EAP and EAP methods against eavesdropping and spoofing is
not an objective of the PANA design.
While PANA is a fundamental part of a complete secure network access
solution, its responsibility is limited to authentication and
authorization of the client and the network. Providing access
control is outside the scope of PANA. A separate provisioning
protocol is needed for passing filtering information to access
control nodes in the network. Additionally, mechanisms to provide
data traffic protection in terms of authentication, integrity and
replay protection, and encryption are outside the scope as well.
Various environments and usage models for PANA are identified in the Various environments and usage models for PANA are identified in the
[USAGE] Internet-Draft. Potential security threats for network-layer [I-D.ietf-pana-usage-scenarios] Internet-Draft. Potential security
access authentication protocol is discussed in [THREATS] draft. threats for network-layer access authentication protocol is discussed
in [I-D.ietf-pana-threats-eval] draft. These two drafts have been
These two drafts have been essential in defining the requirements essential in defining the requirements [I-D.ietf-pana-requirements]
[PY+02] on the PANA protocol. Note that some of these requirements on the PANA protocol. Note that some of these requirements are
are imposed by the chosen payload, EAP [RFC2284]. imposed by the chosen payload, EAP [RFC2284].
This Internet-Draft makes an attempt for defining the PANA protocol This Internet-Draft makes an attempt for defining the PANA protocol
based on the other drafts discussed above. Special care has been based on the other drafts discussed above. Special care has been
given to ensure the currently stated scope is observed and to keep given to ensure the currently stated scope is observed and to keep
the protocol as simple as possible. The current state of this draft the protocol as simple as possible. The current state of this draft
is not complete, but it should be regarded as a work in progress. is not complete, but it should be regarded as a work in progress.
The authors made effort to capture the common understanding The authors made effort to capture the common understanding developed
developed within the working group as much as possible. The design within the working group as much as possible. The design choices
choices being made in this draft should not be considered as cast in being made in this draft should not be considered as cast in stone.
stone.
2 Terminology 2. Terminology
This section describes some terms introduced in this document: This section describes some terms introduced in this document:
PANA Session: PANA Session:
PANA session is defined as the exchange of messages between the PANA session is defined as the exchange of messages between the
PANA Client (PaC) and the PANA Authentication Agent (PAA) to PANA Client (PaC) and the PANA Authentication Agent (PAA) to
authenticate a user (PaC) for network access. If the authenticate a user (PaC) for network access. If the
authentication is unsuccessful, the session is terminated. The authentication is unsuccessful, the session is terminated. The
session is considered as active until there is a disconnect session is considered as active until there is a disconnect
indication by the PaC or the PAA terminates it. indication by the PaC or the PAA terminates it.
Session Identifier: Session Identifier:
This identifier is used to uniquely identify a PANA session on This identifier is used to uniquely identify a PANA session on the
the PAA and PaC. It is included in PANA messages to bind the PAA and PaC. It is included in PANA messages to bind the message
message to a specific PANA session. to a specific PANA session.
PANA Disconnect Indication:
PANA session termination with explicit notification from a PaC
sent to the PAA. The PDI also includes the session identifier.
PANA Session Revocation:
PANA session termination with explicit notification sent from
the PAA to the PaC. The PSR includes the session identifier.
PANA Security Association: PANA Security Association:
The representation of the trust relation between the PaC and The representation of the trust relation between the PaC and the
the PAA that is created at the end of the authentication phase PAA that is created at the end of the authentication phase. This
(PH2). This security association includes the device identifier security association includes the device identifier of the peer,
of the peer, and a shared key when available. and a shared key when available.
The definition of the terms PANA Client (PaC), PANA Authentication The definition of the terms PANA Client (PaC), PANA Authentication
Agent (PAA), Enforcement Point (EP) and Device Identifier (DI) can Agent (PAA), Enforcement Point (EP) and Device Identifier (DI) can be
be found in [PY+02]. found in [I-D.ietf-pana-requirements].
3 Protocol Overview 3. Protocol Overview
The PANA protocol involves two functional entities namely the PaC The PANA protocol involves two functional entities namely the PaC and
and the PAA. The EP, mentioned in the context with PANA, is a the PAA. The EP, mentioned in the context with PANA, is a logical
logical entity. There is, however, the option that the EP is not entity. There is, however, the option that the EP is not physically
physically co-located with the PAA. In case that the PAA and the EP co-located with the PAA. In case that the PAA and the EP are
are co-located only an API is required instead of a separate co-located only an API is required for intercommunication instead of
protocol. In the case where the PAA is separated from the EP, a a separate protocol. In the case where the PAA is separated from the
separate protocol will be used between the PAA and the EP for EP, a separate protocol will be used between the PAA and the EP for
managing access control. The protocol and messaging between the PAA managing access control. The protocol and messaging between the PAA
and EP for access authorization is outside the scope of this draft and EP for access authorization is outside the scope of this draft
and will be dealt separately. and will be dealt separately.
The PANA protocol (PaC<->PAA) resides above the transport layer and The PANA protocol (PaC<->PAA) resides above the transport layer and
the details are explained in Section 4.2. Although this document the details are explained in Section 4. Although this document
describes the interaction with a number of entities and with other describes the interaction with a number of entities and with other
protocol which enable network access authentication; the PANA protocol which enable network access authentication; the PANA
protocol itself is executed between the PaC and the PAA. protocol itself is executed between the PaC and the PAA.
The protocol has three primary functions: The placement of the entities used in PANA largely depends on a
1. The PaC discovering the address of the PAA
2. The transport of EAP payloads between the PaC and the PAA
3. Access authorization by the PAA to the EP [Note that this aspect
is outside the scope of the PANA protocol.]
The placement of the entities used in PANA largely depend on a
certain architecture. The PAA may optionally interact with a AAA certain architecture. The PAA may optionally interact with a AAA
backend to authenticate the user (PaC). And in the case where the backend to authenticate the user (PaC). And in the case where the PAA
PAA and EP are co-located, step 3 mentioned above may not require a and EP are co-located, the intercommunication may not require a
separate protocol. Figure 1 illustrates the interactions in a separate protocol. Figure 1 illustrates the interactions in a
simplified manner: simplified manner:
PaC EP PAA AAA PaC EP PAA AAA
--- --- --- --- --- --- --- ---
PAA Discovery PAA Discovery
<---------------------o-----------------> (1) <---------------------o------------> (1)
| PANA_REQUEST PANA Authentication AAA interaction
| ----------------------------------------> <----------------------------------><------------> (2)
| AAA interaction
|(2) ----------->
| <-----------
| PANA_RESPONSE
| <---------------------------------------
|
Authorization
<----------------- (3)
Figure 1: PANA Protocol Authorization
<------------- (3)
The details of each of these aspects of the protocol are described Figure 1: PANA Framework
in section 4 of this document. PANA supports authentication of a PaC
The details of each of these aspects of the protocol are described in
Section 4 of this document. PANA supports authentication of a PaC
using various EAP methods. The EAP method used depends on the level using various EAP methods. The EAP method used depends on the level
of security required for the EAP messaging itself. PANA does not of security required for the EAP messaging itself. PANA does not
secure the data traffic itself. However, EAP methods that enable key secure the data traffic itself. However, EAP methods that enable key
exchange may allow other protocols to be bootstrapped for securing exchange may allow other protocols to be bootstrapped for securing
the data traffic. the data traffic [I-D.ietf-pana-ipsec].
From a state machine aspect, PANA protocol consists of three phases From a state machine aspect, PANA protocol consists of three phases
1. Discovery and initial handshake phase
1. Discovery and initial handshake phase 2. Authentication phase
2. Authentication phase
3. Termination phase 3. Termination phase
In the first phase, an IP address of PAA is discovered and a PANA In the first phase, an IP address of PAA is discovered and a PANA
session is established between PaC and PAA. EAP messages are session is established between PaC and PAA. EAP messages are
exchanged and a PANA SA is established in the second phase. The exchanged and a PANA SA is established in the second phase. The
established PANA session as well as a PANA SA is deleted in the established PANA session as well as a PANA SA is deleted in the third
third phase. phase.
4 Protocol Details 4. Protocol Details
4.1 Common Processing Rules 4.1 Common Processing Rules
4.1.1 Payload Encoding 4.1.1 Payload Encoding
The payload of any PANA message consists of zero or more AVPs The payload of any PANA message consists of zero or more AVPs
(Attribute Value Pairs). A brief description of the AVPs defined in (Attribute Value Pairs). A brief description of the AVPs defined in
this document is listed below: this document is listed below:
- Cookie AVP: contains a random value that is used for making o Cookie AVP: contains a random value that is used for making
initial handshake robust against blind resource consumption DoS initial handshake robust against blind resource consumption DoS
attacks. attacks.
- Protection-Cap. AVP: contains information which protection should o Protection-Capability AVP: contains information which protection
be initiated after the PANA exchange (e.g. link-layer or network should be initiated after the PANA exchange (e.g. link-layer or
layer protection). network layer protection).
- Device-Id AVP: contains a device identifier of the sender of the
message. A device identifier is represented as a pair of device
identifier type and device identifier value. Either a layer-2
address or an IP address is used for the device identifier value.
- EAP AVP: contains an EAP PDU. o Device-Id AVP: contains a device identifier of the sender of the
message. A device identifier is represented as a pair of device
identifier type and device identifier value. Either a layer-2
address or an IP address is used for the device identifier value.
- MAC AVP: contains a Message Authentication Code that protects a o EAP AVP: contains an EAP PDU.
PANA message PDU.
- Termination-Cause AVP: contains the reason of session termination. o MAC AVP: contains a Message Authentication Code that protects a
PANA message PDU.
- Result-Code AVP: contains information about the protocol execution o Termination-Cause AVP: contains the reason of session termination.
results.
- Session-Id AVP: contains the session identifier value. o Result-Code AVP: contains information about the protocol execution
results.
o Session-Id AVP: contains the session identifier value.
o Session-Lifetime AVP: contains the duration of authorized access.
o Failed-AVP: contains the offending AVP that caused a failure.
o NAP-Information AVP, ISP-Information AVP: contains the information
on a NAP and an ISP, respectively.
4.1.2 Transport Layer Protocol 4.1.2 Transport Layer Protocol
PANA uses UDP as its transport layer protocol. The UDP port number PANA uses UDP as its transport layer protocol. The UDP port number
is TBD. All messages except for PANA-PAA-Discover are always is TBD. All messages except for PANA-PAA-Discover are always
unicast. PaC MAY use unspecified IP address for communicating with unicast. PaC MAY use unspecified IP address for communicating with
PAA. PAA.
4.1.3 Fragmentation 4.1.3 Fragmentation
PANA does not provide fragmentation of PANA messages. Instead, it PANA does not provide fragmentation of PANA messages. Instead, it
relies on fragmentation provided by EAP methods and IP layer when relies on fragmentation provided by EAP methods and IP layer when
needed. needed.
4.1.4 Sequence Number and Retransmission 4.1.4 Sequence Number and Retransmission
PANA uses sequence numbers to provide ordered delivery of EAP PANA uses sequence numbers to provide ordered delivery of EAP
messages. The design involves use of two sequence numbers to prevent messages. The design involves use of two sequence numbers to prevent
some of the DoS attacks on the sequencing scheme. Every PANA packet some of the DoS attacks on the sequencing scheme. Every PANA packet
include one transmitted sequence number (tseq) and one received include one transmitted sequence number (tseq) and one received
sequence number (rseq) in the PANA header. See Appendix for sequence number (rseq) in the PANA header. See Appendix A for
detailed explanation on why two sequence numbers are needed. detailed explanation on why two sequence numbers are needed.
The two sequence number fields have the same length of N (TBD: The two sequence number fields have the same length of 32 bits and
possibly 32) bits and appear in PANA header. tseq starts from appear in PANA header. tseq starts from initial sequence number
initial sequence number (ISN) and is monotonically increased by 1. (ISN) and is monotonically increased by 1. The serial number
The serial number arithmetic defined in [RFC1982] is used for arithmetic defined in [RFC1982] is used for sequence number
sequence number operation. The ISNs are exchanged between PaC and operation. The ISNs are exchanged between PaC and PAA during the
PAA during the discovery and initial handshake phase (see section discovery and initial handshake phase (see Section 4.2). The rules
"Discovery and Initial Handshake Phase"). The rules that govern the that govern the sequence numbers in other phases are described as
sequence numbers in other phases are described as follows. follows.
o When a message is sent, a new sequence number is placed on the o When a message is sent, a new sequence number is placed on the
tseq field of message regardless of whether it is sent as a result tseq field of message regardless of whether it is sent as a result
of retransmission or not. When a message is sent, rseq is copied of retransmission or not. When a message is sent, rseq is copied
from the tseq field of the last accepted message. from the tseq field of the last accepted message.
o When a message is received, it is considered as valid in terms of o When a message is received, it is considered valid in terms of
sequence numbers if and only if (i) its tseq is greater than the sequence numbers if and only if (i) its tseq is greater than the
tseq of the last accepted message and (ii) its rseq falls in the tseq of the last accepted message and (ii) its rseq falls in the
range between the tseq of the last acknowledged message + 1 and the range between the tseq of the last acknowledged message + 1 and
tseq of the last transmitted message. the tseq of the last transmitted message.
PANA relies on EAP-layer retransmission for retransmitting EAP PANA relies on EAP-layer retransmissions, or for example NAS
Request based on timer. Other PANA layer messages that require a functionality [I-D.ietf-aaa-eap], for retransmitting EAP Requests
response from the communicating peer are retransmitted based on based on timer. Other PANA layer messages that require a response
timer at PANA-layer until a response is received (in which case the from the communicating peer are retransmitted based on timer at
PANA-layer until a response is received (in which case the
retransmission timer is stopped) or the number of retransmission retransmission timer is stopped) or the number of retransmission
reaches the maximum value (in which case the PANA session MUST be reaches the maximum value (in which case the PANA session MUST be
deleted immediately). For PANA-layer retransmission, the deleted immediately). For PANA-layer retransmission, the
retransmission timer SHOULD be calculated as described in [RFC2988] retransmission timer SHOULD be calculated as described in [RFC2988]
to provide congestion control (TBD: default timer and maximum to provide congestion control. See Section 10 for default timer and
retransmission count suggestions). maximum retransmission count parameters.
4.1.5 PANA Security Association 4.1.5 PANA Security Association
A PANA SA is created as an attribute of a PANA session when EAP A PANA SA is created as an attribute of a PANA session when EAP
authentication succeeds with a creation of a Master Session Key authentication succeeds with a creation of a Master Session Key (MSK)
(MSK) [RFC2284bis]. A PANA SA is not created when the PANA [I-D.ietf-eap-rfc2284bis]. A PANA SA is not created when the PANA
authentication fails or no MSK is produced by any EAP authentication authentication fails or no MSK is produced by any EAP authentication
method. In the case where two EAP authentications are performed in a method. In the case where two EAP authentications are performed in a
sequence in a single PANA authentication, it is possible that two sequence in a single PANA authentication, it is possible that two
MSKs are derived. If this happens, the PANA SA MUST be bound to the MSKs are derived. If this happens, the PANA SA MUST be bound to the
MSK derived from the first EAP authentication. When a new MSK is MSK derived from the first EAP authentication. When a new MSK is
derived as a result of EAP-based re-authentication, any key derived derived as a result of EAP-based re-authentication, any key derived
from the old MSK MUST be updated to a new one that is derived from from the old MSK MUST be updated to a new one that is derived from
the new MSK. the new MSK.
The created PANA SA is deleted when the corresponding PANA session The created PANA SA is deleted when the corresponding PANA session is
is deleted. The lifetime of the PANA SA is the same as the lifetime deleted. The lifetime of the PANA SA is the same as the lifetime of
of the PANA session for simplicity. the PANA session for simplicity.
PANA SA attributes as well as PANA session attributes are listed PANA SA attributes as well as PANA session attributes are listed
below: below:
PANA Session attributes: PANA Session attributes:
- Session-Id
- Device-Id of PaC * Session-Id
- Device-Id of PAA
- Initial tseq of PaC (ISN_pac) * Device-Id of PaC
- Initial tseq of PAA (ISN_paa)
- Last transmitted tseq value * Device-Id of PAA
- Last received rseq value
- Last transmitted message payload * Initial tseq of PaC (ISN_pac)
- Retransmission interval
- Session lifetime * Initial tseq of PAA (ISN_paa)
- Protection-Capability
- PANA SA attributes: * Last transmitted tseq value
+ MSK
+ PANA_MAC_Key * Last received rseq value
* Last transmitted message payload
* Retransmission interval
* Session lifetime
* Protection-Capability
* PANA SA attributes:
+ MSK
+ PANA_MAC_Key
The PANA_MAC_Key is used to integrity protect PANA messages and The PANA_MAC_Key is used to integrity protect PANA messages and
derived from the MSK in the following way: derived from the MSK in the following way:
PANA_MAC_KEY = The first N-bit of PANA_MAC_KEY = The first N-bit of
HMAC_SHA1(MSK, ISN_pac | ISN_paa | Session-ID) HMAC_SHA1(MSK, ISN_pac | ISN_paa | Session-ID)
where the value of N depends on the integrity protection algorithm
in use, i.e., N=128 for HMAC-MD5 and N=160 for HMAC-SHA1.
The length of MSK MUST be N-bit or longer. See section 4.1.6 for where the value of N depends on the integrity protection algorithm in
the detailed usage of the PANA_MAC_Key. use, i.e., N=128 for HMAC-MD5 and N=160 for HMAC-SHA1.
The length of MSK MUST be N-bit or longer. See Section 4.1.6 for the
detailed usage of the PANA_MAC_Key.
4.1.6 Message Authentication Code 4.1.6 Message Authentication Code
A PANA message can contain a MAC (Message Authentication Code) AVP A PANA message can contain a MAC (Message Authentication Code) AVP
for cryptographically protecting the message. for cryptographically protecting the message.
When a MAC AVP is included in a PANA message, the value field of the When a MAC AVP is included in a PANA message, the value field of the
MAC AVP is calculated by using the PANA_MAC_Key in the following MAC AVP is calculated by using the PANA_MAC_Key in the following way:
way:
MAC AVP value = HMAC_SHA1(PANA_MAC_Key, PANA_PDU) MAC AVP value = HMAC_SHA1(PANA_MAC_Key, PANA_PDU)
where PANA_PDU is the PANA message including the PANA header, with where PANA_PDU is the PANA message including the PANA header, with
the MAC AVP value field first initialized to 0. the MAC AVP value field first initialized to 0.
4.1.7 Message Validity Check 4.1.7 Message Validity Check
When a PANA message is received, the message is considered to be When a PANA message is received, the message is considered to be
invalid at least when one of the following conditions are not met: invalid at least when one of the following conditions are not met:
o Each field in the message header contains a valid value including o Each field in the message header contains a valid value including
sequence number, message length, message type, version number, sequence number, message length, message type, version number,
flags, etc. flags, etc.
o When a device identifier of the communication peer is bound to the o When a device identifier of the communication peer is bound to the
PANA session, it matches the device identifier carried in MAC and/or PANA session, it matches the device identifier carried in MAC and/
IP header(s). or IP header(s).
o The message type is one of the expected types in the current o The message type is one of the expected types in the current
state. state.
o The message payload contains a valid set of AVPs allowed for the o The message payload contains a valid set of AVPs allowed for the
message type and there is no missing AVP that needs to be included message type and there is no missing AVP that needs to be included
in the payload. in the payload.
o Each AVP is decoded correctly. o Each AVP is decoded correctly.
o When a MAC AVP is included, the AVP value matches the MAC value o When a MAC AVP is included, the AVP value matches the MAC value
computed against the received message. computed against the received message.
o When a Device-Id AVP is included, the AVP is valid if the device o When a Device-Id AVP is included, the AVP is valid if the device
identifier type contained in the AVP matches the expected one (this identifier type contained in the AVP is supported (this check is
check is for PAA only) and the device identifier value contained in for both PaC and PAA) and is the requested one (this check is for
the AVP matches the value extracted from the lower-layer PAA only) and the device identifier value contained in the AVP
encapsulation header corresponding to the device identifier type matches the value extracted from the lower-layer encapsulation
contained in the AVP. header corresponding to the device identifier type contained in
the AVP. Note that a Device-Id AVP carries the PaC's device
identifier in messages from PaC to PAA and PAA's device identifier
in messages from PAA to PaC.
Invalid messages MUST be discarded in order to provide robustness Invalid messages MUST be discarded in order to provide robustness
against DoS attacks and an unprotected. (TBD: in addition, a against DoS attacks and an unprotected. In addition, a
non-acknowledged error notification message MAY be returned to the non-acknowledged error notification message MAY be returned to the
sender.) sender. See Section 4.1.8 for details.
4.1.8 Error Handling
PANA-Error message MAY be sent by either PaC or PAA when a badly
formed PANA message is received or in case of other errors. If the
cause of this error message was a request message (e.g.,
PANA-PAA-Discover or *-Request), then the request MAY be
retransmitted immediately without waiting for its retransmission
timer to go off. If the cause of the error was a response message,
the receiver of the PANA-Error message SHOULD NOT resend the same
response until it receives the next request.
To defend against DoS attacks a timer MAY be used. One (1) error
notification is sent to each different sender each N seconds. N is a
configurable parameter.
When an error message is sent unprotected with MAC AVP and the
lower-layer is insecure, the error message is treated as an
informational message. The receiver of such an error message MUST
NOT change its state unless the error persists and the PANA session
is not making any progress.
4.2 Discovery and Initial Handshake Phase 4.2 Discovery and Initial Handshake Phase
When a PaC attaches to a network, and knows that it has to discover When a PaC attaches to a network, and knows that it has to discover
PAA for PANA, it can send a PANA-PAA-Discover message to a well- PAA for PANA, it SHOULD send a PANA-PAA-Discover message to a well-
known link local multicast address (TBD) and UDP port (TBD). The known link local multicast address (TBD) and UDP port (TBD). The
source address is set to the unspecified IP address if the PaC has source address is set to the unspecified IP address if the PaC has
not configured an address yet. PANA PAA discovery assumes that PaC not configured an address yet. PANA PAA discovery assumes that PaC
and PAA are one hop away from each other. If PaC knows the IP and PAA are one hop away from each other. If PaC knows the IP address
address of the PAA (some pre-configuration), it can unicast the PANA of the PAA (some pre-configuration), it MAY unicast the PANA
discovery message to that address. PAA answers to the PANA-PAA- discovery message to that address. PAA SHOULD answer to the
Discover message with a PANA-Start-Request message. PANA-PAA-Discover message with a PANA-Start-Request message.
When the PAA receives such a request, or upon receiving some lower When the PAA receives such a request, or upon receiving some lower
layer indications of a new PaC, PAA can unicast a PANA-Start-Request layer indications of a new PaC, PAA SHOULD unicast a
message. The destination address may be unspecified IP address, but PANA-Start-Request message. The destination address may be
the L2 destination would be a unicast address (something for the unspecified IP address, but the L2 destination would be a unicast
implementations to deal with). address (something for the implementations to deal with).
There can be multiple PAAs on the link. The result does not depend There can be multiple PAAs on the link. The authentication and
on which PAA PaC chooses. By default PaC chooses the PAA that sent authorization result does not depend on which PAA is chosen by the
PaC. By default the PaC MAY choose the PAA that sent the that sent
the first response. the first response.
PaC may also choose to start sending packets before getting PaC may also choose to start sending packets before getting
authenticated. In that case, the network should detect this and send authenticated. In that case, the network should detect this and send
an unsolicited PANA-Start-Request message to PaC. EP is the node an unsolicited PANA-Start-Request message to PaC. EP is the node that
that can detect such activity. If EP and PAA are co-located, then an can detect such activity. If EP and PAA are co-located, then an
internal mechanism (e.g. API) between the EP module and the PAA internal mechanism (e.g. API) between the EP module and the PAA
module on the same host can prompt PAA to start PANA. In case they module on the same host can prompt PAA to start PANA. In case they
are separate, there needs to an explicit message to prompt PAA. Upon are separate, there needs to be an explicit message to prompt PAA.
detecting the need to authenticate a client, EP can send a PANA-PAA- Upon detecting the need to authenticate a client, EP can send a
Discover message to the PAA on behalf of the PaC. This message PANA-PAA-Discover message to the PAA on behalf of the PaC. This
carries a device identifier of the PaC in a Device-ID AVP. So that, message carries a device identifier of the PaC in a Device-ID AVP. So
the PAA can send the unsolicited PANA-Start-Request message directly that, the PAA can send the unsolicited PANA-Start-Request message
to the PaC. If the link between the EP and PAA is not secure, the directly to the PaC. If the link between the EP and PAA is not
PANA-PAA-Discover message sent from the EP to the PAA MUST be secure, the PANA-PAA-Discover message sent from the EP to the PAA
protected by using. MUST be protected by using, e.g., IPsec.
A PANA-Start-Request message contains a cookie carried in a Cookie A PANA-Start-Request message contains a cookie carried in a Cookie
AVP in the payload, respectively. The rseq field of the header is AVP in the payload, respectively. The rseq field of the header is
set to zero (0). The tseq field of the header contains the initial set to zero (0). The tseq field of the header contains the initial
sequence number. The cookie is used for preventing the PAA from sequence number. The cookie is used for preventing the PAA from
resource consumption DoS attacks by blind attackers. The cookie is resource consumption DoS attacks by blind attackers. The cookie is
computed in such a way as not to require any saved per-session state computed in such a way that it does not require any per-session state
to recognize its valid cookie when a particular message sent by the maintenance on the PAA in order to verify the cookie returned in a
PaC in response to the PANA-Start-Request message arrives. The PANA-Start-Answer message. The exact algorithms and syntax used for
exact algorithms and syntax used for generating cookies does not generating cookies does not affect interoperability and hence is not
affect interoperability and hence is not specified here. An example specified here. An example algorithm is described below.
algorithm is described below.
Cookie = Cookie =
<secret-version> | HMAC_SHA1( <Device-Id of PaC> | <secret> ) <secret-version> | HMAC_SHA1( <Device-Id of PaC> | <secret> )
where <secret> is a randomly generated secret known only to the where <secret> is a randomly generated secret known only to the PAA,
PAA, <secret-version> is an index used for choosing the secret for <secret-version> is an index used for choosing the secret for
generating the cookie and '|' indicates concatenation. The secret- generating the cookie and '|' indicates concatenation. The secret-
version should be changed frequently enough to prevent replay version should be changed frequently enough to prevent replay
attacks. The secret key is locally known to the PAA only and valid attacks. The secret key is locally known to the PAA only and valid
for a certain time frame. for a certain time frame.
When a PaC receives the PANA-Start-Request message in response to PAA MAY enable NAP-ISP authentication separation by setting the
the PANA-PAA-Discover message, it responds with a PANA-Start-Answer S-flag of the message header of the PANA-Start-Request. Also, the
message. The PANA-Start-Answer message contains the initial sequence PANA-Start-Request MAY contain zero or one NAP-Information AVP and
numbers in the tseq and rseq fields of the PANA header, a copy of zero or more ISP-Information AVPs to advertise the information on the
the received Cookie as the PANA payload. NAP and/or ISPs.
When the PAA receives the PANA-Start-Request message from the PaC, When a PaC receives the PANA-Start-Request message in response to the
it verifies the cookie. The cookie is considered as valid if the PANA-PAA-Discover message, it responds with a PANA-Start-Answer
message if it wishes to enter the authentication phase. The
PANA-Start-Answer message contains the initial sequence numbers in
the tseq and rseq fields of the PANA header, a copy of the received
Cookie (if any) as the PANA payload.
If the S-flag of the received PANA-Start-Request message is not set,
PaC MUST NOT set the S-flag in the PANA-Start-Answer message sent
back to the PAA. In this case, PaC can indicate its choice of ISP by
including its ISP-Information AVP in the PANA-Start-Answer message.
AAA routing will be based on the ISP choice if an ISP-Information AVP
is specified in the PANA-Start-Answer message, otherwise it will be
based on EAP identifier.
If the S-flag of the received PANA-Start-Request message is set, PaC
can indicate its desire to perform separate EAP authentication for
NAP and ISP by setting the S-flag in the PANA-Start-Answer message.
In this case, PaC can also indicate its choice of ISP by including
its ISP-Information AVP in the PANA-Start-Answer message. AAA
routing for NAP authentication will be based on the NAP. AAA routing
for ISP authentication will be based on the ISP choice if an
ISP-Information AVP is specified in the PANA-Start-Answer message,
otherwise it will be based on EAP identifier."
When the PAA receives the PANA-Start-Answer message from the PaC, it
verifies the cookie. The cookie is considered as valid if the
received cookie has the expected value. If the computed cookie is received cookie has the expected value. If the computed cookie is
valid, the protocol enters the authentication phase. Otherwise, it valid, the protocol enters the authentication phase. Otherwise, it
MUST silently discard the received message. MUST silently discard the received message.
The PANA-Start-Request/Answer exchange is needed before entering The PANA-Start-Request/Answer exchange is needed before entering
authentication phase even when the PaC is pre-configured with PAAs authentication phase even when the PaC is pre-configured with PAAs IP
IP address and the PANA-PAA-Discover message is unicast. address and the PANA-PAA-Discover message is unicast.
A PANA-Start-Request message is never retransmitted. A PANA-Start- A PANA-Start-Request message is never retransmitted. A
Answer message is retransmitted based on timer in the same manner as PANA-Start-Answer message is retransmitted based on timer in the same
other messages retransmitted at PANA-layer. manner as other messages retransmitted at PANA-layer.
PaC PAA Message PaC PAA Message
------------------------------------------------------ ------------------------------------------------------
-----> PANA-PAA-Discover(0,0) -----> PANA-PAA-Discover(0,0)
<----- PANA-Start-Request(x,0)[Cookie] <----- PANA-Start-Request(x,0)[Cookie]
-----> PANA-Start-Answer(x,y)[ Cookie] -----> PANA-Start-Answer(x,y)[Cookie]
(continued to authentication phase) (continued to authentication phase)
(PANA-PAA-Discover sent by PaC) Figure 2: Example Sequence for Discovery and Initial Handshake Phase
Figure 2: Example Sequence for Discovery and Initial Handshake Phase
PaC EP PAA Message PaC EP PAA Message
------------------------------------------------------ ------------------------------------------------------
---->o (Data packet arrival or L2 trigger) ---->o (Data packet arrival or L2 trigger)
------> PANA-PAA-Discover(0,0)[Device-Id] ------> PANA-PAA-Discover(0,0)[Device-Id]
<------------ PANA-Start-Request(x,0)[ Cookie] <------------ PANA-Start-Request(x,0)[ Cookie]
------------> PANA-Start-Answer(y,x)[ Cookie] ------------> PANA-Start-Answer(y,x)[ Cookie]
(continued to authentication phase) (continued to authentication phase)
(PANA-PAA-Discover sent by EP) Figure 3: Example Sequence for Discovery and Initial Handshake Phase
Figure 3: Example Sequence for Discovery and Initial Handshake Phase when PANA-PAA-Discover is sent by PaC
4.3 Authentication Phase 4.3 Authentication Phase when PANA-PAA-Discover is sent by EP
The main task in authentication phase is to carry EAP messages The main task in authentication phase is to carry EAP messages
between PaC and PAA. All EAP messages except for EAP Success/Failure between PaC and PAA. All EAP messages except for EAP Success/Failure
messages are carried in the PANA-Auth-Request/PANA-Auth-Answer messages are carried in the PANA-Auth-Request/PANA-Auth-Answer
messages. When an EAP Success/Failure message is sent from a PAA, messages. When an EAP Success/Failure message is sent from a PAA,
the message is carried in the PANA-Bind-Request message. The PANA- the message is carried in the PANA-Bind-Request message. The PANA-
Bind-Request message is acknowledged with a PANA-Bind-Answer. It is Bind-Request message is acknowledged with a PANA-Bind-Answer. It is
possible to carry multiple EAP sequences in a single PANA sequence. possible to carry multiple EAP sequences in a single PANA session.
A single PANA session can enable more than one EAP authentication. When PaC and PAA negotiated during the discovery and initial
This is used to satisfy the separate NAP and ISP authentications handshake phase to perform separate NAP and ISP authentications in a
scenario. Each EAP authentication is delineated from the subsequent single PANA session, the PAA determines the execution order of NAP
one. The F-flag in the PANA header indicates if this was the final authentication and ISP authentication. In this case, the PAA can
authentication from sender's perspective. If the PAA enables two indicate which EAP authentication is currently occurring by including
separate authentication, it should not set the F-flag in after the a NAP-Information or an ISP-Information AVP of the corresponding EAP
first EAP method. This indicates PAA's willingness to offer another authentication in the first PANA-Auth-Request message sent to the
authentication method for NAP-ISP separation. PaC can respond with PaC. In the case where the PaC agreed to perform separate
the F-flag unset, indicating PaC's willingness to go through a authentications but did not specify its ISP choice in
second authentication method. The PaC can optionally decline by PANA-Start-Answer message, the PAA MUST include its NAP-Information
setting the F-flag, and this concludes the PANA authentication. If AVP in PANA-Auth-Request message when it performs NAP authentication
the PAA does not offer two levels of authentication, then it sets and MUST NOT include any service provider information AVP when it
the F-flag even at the end of first EAP exchange. In that case the performs ISP authentication so that the PaC can always distinguish
PaC has no other option but to set the F-flag to mark the end of ISP authentication from NAP authentication. The PAA SHOULD stop
PANA authentication. including a NAP-Information or an ISP-Information AVP once it
receives the first PANA-Auth-Answer message of the current EAP
authentication.
Currently, use of multiple EAP methods in PANA is designed only for Currently, use of multiple EAP methods in PANA is designed only for
NAP-ISP authentication separation. It is not for arbitrary EAP NAP-ISP authentication separation. It is not for arbitrary EAP
method sequencing, or giving the PaC another chance when an method sequencing, or giving the PaC another chance when an
authentication method fails. The NAP and ISP authentication are authentication method fails. The NAP and ISP authentication are
considered completely independent. Presence or success of one considered completely independent. Presence or success of one should
should not effect the other. Making a decision based on the success not effect the other. Making an authentication decision based on the
or failure of each authentication is a network policy issue. PANA success or failure of each authentication is a network policy issue.
signals only the result of the immediately preceding EAP PANA signals only the result of the immediately preceding EAP
authentication method. authentication method in PANA-Bind-Request messages.
When an EAP method that is capable of deriving keys is used during When an EAP method that is capable of deriving keys is used during
the authentication phase and the keys are successfully derived all the authentication phase and the keys are successfully derived the
subsequent PANA messages MUST contain a MAC AVP. The PANA-Bind- PANA-Bind-Request and PANA-Bind-Answer messages and all subsequent
Request and the PANA-Bind-Answer message exchange is also used for PANA messages MUST contain a MAC AVP. The PANA-Bind-Request and the
binding device identifiers of the PaC and the PAA to the PANA SA. PANA-Bind-Answer message exchange is also used for binding device
To achieve this, the PANA-Bind-Request and the PANA-Bind-Answer identifiers of the PaC and the PAA to the PANA SA. To achieve this,
SHOULD contain a device identifier of the PAA and the PaC, the PANA-Bind-Request and the PANA-Bind-Answer SHOULD contain a
respectively, in a Device-Id AVP. The PaC MUST use the same type of device identifier of the PAA and the PaC, respectively, in a
device identifier as contained in the PANA-Bind-Request message. Device-Id AVP. The PaC MUST use the same type of device identifier
The PANA-Bind-Request message MAY also contain a Protection-Capability as contained in the PANA-Bind-Request message. The PANA-Bind-Request
AVP to indicate if link-layer or network-layer ciphering should be message MAY also contain a Protection-Capability AVP to indicate if
initiated after PANA. No link layer or network layer specific link-layer or network-layer ciphering should be initiated after PANA.
information is included in the Protection-Capability AVP. When the No link layer or network layer specific information is included in
information is preconfigured on the PaC and the PAA this AVP can be the Protection-Capability AVP. When the information is preconfigured
omitted. It is assumed that at least PAA is aware of the security on the PaC and the PAA this AVP can be omitted. It is assumed that at
capabilities of the access network. The PANA protocol does not least PAA is aware of the security capabilities of the access
specify how the PANA SA and the Protection-Capability AVP will be network. The PANA protocol does not specify how the PANA SA and the
used to provide per-packet protection for data traffic. Protection-Capability AVP will be used to provide per-packet
protection for data traffic.
PANA-Bind-Request and PANA-Bind-Answer messages MUST be PANA-Bind-Request and PANA-Bind-Answer messages MUST be retransmitted
retransmitted based on the retransmission rule described in Appendix based on the retransmission rule described in Appendix A.
A.
PaC PAA Message(tseq,rseq)[AVPs] PaC PAA Message(tseq,rseq)[AVPs]
------------------------------------------------- -------------------------------------------------
(continued from discovery and initial handshake phase) (continued from discovery and initial handshake phase)
<----- PANA-Auth-Request(x+1,y)[EAP{Request}] <----- PANA-Auth-Request(x+1,y)[EAP{Request}]
-----> PANA-Auth-Answer(y+1,x+1)[EAP{Response}] ----->> PANA-Auth-Answer(y+1,x+1)[EAP{Response}]
. .
. .
<----- PANA-Auth-Request (x+2,y+1)[EAP{Request}] <----- PANA-Auth-Request (x+2,y+1)[EAP{Request}]
-----> PANA-Auth-Answer (y+2,x+2)[EAP{Response}] -----> PANA-Auth-Answer (y+2,x+2)[EAP{Response}]
<----- PANA-Bind-Request(x+3,y+2) // F-flag <----- PANA-Bind-Request(x+3,y+2)
set [EAP{Success}, Device-Id, Lifetime, Protection-Cap., MAC]
[EAP{Success}, Device-Id, Protection-Cap., MAC]
-----> PANA-Bind-Answer(y+3,x+3)
[Device-Id, Protection-Cap., MAC] // F-flag set
Figure 4: Example Sequence in Authentication Phase -----> PANA-Bind-Answer(y+3,x+3)
[Device-Id, Protection-Cap., MAC]
Figure 4: Example Sequence in Authentication Phase
4.4 Re-authentication 4.4 Re-authentication
There are two types of re-authentication supported by PANA. There are two types of re-authentication supported by PANA.
The first type of re-authentication is based on EAP by entering an The first type of re-authentication is based on EAP by entering an
authentication phase. In this case, some or all message exchanges authentication phase. In this case, some or all message exchanges
for discovery and initial handshake phase MAY be omitted in the for discovery and initial handshake phase MAY be omitted in the
following way. When a PaC initiates EAP-based re-authentication, it following way. When a PaC wants to initiate EAP-based
sends a PANA-PAA-Discovery message to the PAA. If the PAA already re-authentication, it sends a unicast PANA-PAA-Discovery message to
has an established PANA session for the PaC with a device identifier the PAA. This message MUST contain a Session-Id AVP which is used
that matches the one extracted from the MAC header and/or IP header for identifying the PANA session on the PAA. If the PAA already has
of the PANA-PAA-Discover message, it sends a PANA-Auth-Request an established PANA session for the PaC with the matching identifier,
message with the session identifier for that PANA session to start it sends a PANA-Auth-Request message containing the same identifier
an authentication phase. When the PAA initiates EAP-based re- to start an authentication phase. If the PAA can not recognize the
authentication, it sends a PANA-Auth-Request message with the session identifier, it proceeds with regular authentication by
session identifier for the PaC to enter an authentication phase. In sending back PANA-Start-Request. When the PAA initiates EAP-based
both cases, the tseq and rseq values are inheritated from the re-authentication, it sends a PANA-Auth-Request message containing
previous (re-)authentication. For any EAP-based re-authentication, the session identifier for the PaC to enter an authentication phase.
if there is an established PANA SA, PANA-Auth-Request and PANA-Auth- PAA SHOULD initiate EAP authentication before the current session
Answer messages MAY be protected by adding a MAC AVP to each lifetime expires. In both cases, the tseq and rseq values are
message. inherited from the previous (re-)authentication. For any EAP-based
re-authentication, if there is an established PANA SA,
PANA-Auth-Request and PANA-Auth-Answer messages SHOULD be protected
by adding a MAC AVP to each message.
The second type of re-authentication is based on a single protected The second type of re-authentication is based on a single protected
message exchange without entering the authentication phase. message exchange without entering the authentication phase.
PANA-Reauth-Request and PANA-Reauth-Answer messages are used for PANA-Reauth-Request and PANA-Reauth-Answer messages are used for this
this purpose. If there is an established PANA SA, both the PaC and purpose. If there is an established PANA SA, both the PaC and the
the PAA are allowed to send a PANA-Reauth-Request message to the PAA are allowed to send a PANA-Reauth-Request message to the
communicating peer whenever it needs to make sure the availability communicating peer whenever it needs to make sure the availability of
of the PANA SA on the peer and expect the peer to return a PANA- the PANA SA on the peer and expect the peer to return a PANA-
Reauth-Answer message. Both PANA-Reauth-Request/ PANA-Reauth-Answer Reauth-Answer message. Both PANA-Reauth-Request/ PANA-Reauth-Answer
messages MUST be protected with a MAC AVP. messages MUST be protected with a MAC AVP.
Implementations MUST limit the rate of performing re-authentication Implementations MUST limit the rate of performing re-authentication
for both types of re-authentication. for both types of re-authentication.
PaC PAA Message(tseq,rseq)[AVPs] PaC PAA Message(tseq,rseq)[AVPs]
------------------------------------------------------ ------------------------------------------------------
-----> PANA-Reauth-Request(q,p)[MAC] -----> PANA-Reauth-Request(q,p)[MAC]
<----- PANA-Reauth-Answer(p+1,q)[MAC] <----- PANA-Reauth-Answer(p+1,q)[MAC]
Figure 5: Example Sequence for PaC-initiated Re-authentication Figure 5: Example Sequence for PaC-initiated second type
Re-authentication
PaC PAA Message(tseq,rseq)[AVPs] PaC PAA Message(tseq,rseq)[AVPs]
------------------------------------------------------ ------------------------------------------------------
<----- PANA-Reauth-Request(p,q)[MAC] <----- PANA-Reauth-Request(p,q)[MAC]
-----> PANA-Reauth-Answer(q+1,p)[MAC] -----> PANA-Reauth-Answer(q+1,p)[MAC]
Figure 6: Example Sequence for PAA-initiated Re-authentication Figure 6: Example Sequence for PAA-initiated second type
Re-authentication
4.5 Termination Phase 4.5 Termination Phase
A procedure for explicitly terminating a PANA session can be A procedure for explicitly terminating a PANA session can be
initiated either from PaC (i.e., disconnect indication) or from PAA initiated either from PaC (i.e., disconnect indication) or from PAA
(i.e., session revocation). The PANA-Termination-Request and the (i.e., session revocation). The PANA-Termination-Request and the
PANA-Termination-Answer message exchanges are used for PANA-Termination-Answer message exchanges are used for disconnect
disconnect indication and session revocation procedures. indication and session revocation procedures.
The reason for termination is indicated in the Termination-Cause The reason for termination is indicated in the Termination-Cause AVP.
AVP. When there is an established PANA SA established between the When there is an established PANA SA established between the PaC and
PaC and the PAA, all messages exchanged during the termination phase the PAA, all messages exchanged during the termination phase MUST be
MUST be protected with a MAC AVP. When the sender of the PANA- protected with a MAC AVP. When the sender of the PANA-
Termination-Request receives a valid acknowledgment, all states Termination-Request receives a valid acknowledgment, all states
maintained for the PANA session MUST be deleted immediately. maintained for the PANA session MUST be deleted immediately.
PaC PAA Message(tseq,rseq)[AVPs] PaC PAA Message(tseq,rseq)[AVPs]
------------------------------------------------------ ------------------------------------------------------
-----> PANA-Termination-Request(q,p)[MAC] -----> PANA-Termination-Request(q,p)[MAC]
<----- PANA-Termination-Answer(p+1,q)[MAC] <----- PANA-Termination-Answer(p+1,q)[MAC]
Figure 7: Example Sequence for Session Termination Figure 7: Example Sequence for Session Termination
4.6 Illustration of a Complete Message Sequence 4.6 Illustration of a Complete Message Sequence
A complete PANA message sequence is illustrated in Figure 8. The A complete PANA message sequence is illustrated in Figure 8. The
example assumes the following scenario: example assumes the following scenario:
- PaC multicasts PANA-PAA-Discover message o PaC multicasts PANA-PAA-Discover message
- The ISNs used by the PAA and the PaC are x and y, respectively.
- A single EAP sequence is used in authentication phase.
- An EAP authentication method with a single round trip is used in
the EAP sequence.
- The EAP authentication method derives keys. The PANA SA is o The ISNs used by the PAA and the PaC are x and y, respectively.
established based on the unique and fresh session key provided by
the EAP method.
- After PANA SA is established, all messages are integrity and o A single EAP sequence is used in authentication phase.
replay protected with the MAC AVP.
- Re-authentication based on the PANA-Reauth-Request/ PANA-Reauth- o An EAP authentication method with a single round trip is used in
Answer exchange is performed. the EAP sequence.
- The PANA session is terminated as a result of the PANA- o The EAP authentication method derives keys. The PANA SA is
Termination-Request indication from the PaC. established based on the unique and fresh session key provided by
the EAP method.
PaC PAA Message(tseq,rseq)[AVPs] o After PANA SA is established, all messages are integrity and
----------------------------------------------------- replay protected with the MAC AVP.
// Discovery and initial handshake phase
-----> PANA-PAA-Discover (0,0)
<----- PANA-Start-Request (x,0)[Cookie]
-----> PANA-Start-Request-Answer (y,x)[Cookie]
// Authentication phase o Re-authentication based on the PANA-Reauth-Request/ PANA-Reauth-
<----- PANA-Auth-Request(x+1,y)[EAP] Answer exchange is performed.
-----> PANA-Auth-Answer(y+1,x+1)[EAP]
<----- PANA-Auth-Request(x+2,y+1)[EAP]
-----> PANA-Auth-Answer(y+2,x+2)[EAP]
<----- PANA-Bind-Request(x+3,y+2) // F-flag set
[EAP, Device-Id, Data-Protection, MAC]
-----> PANA-Bind-Answer(y+3,x+3) // F-flag set o The PANA session is terminated as a result of the PANA-
[Device-Id, Data-Protection, MAC] Termination-Request indication from the PaC.
// Re-authentication PaC PAA Message(tseq,rseq)[AVPs]
<----- PANA-Reauth-Request (x+4,y+3)[MAC] -----------------------------------------------------
-----> PANA-Reauth-Answer (y+4,x+4)[MAC] // Discovery and initial handshake phase
-----> PANA-PAA-Discover (0,0)
<----- PANA-Start-Request (x,0)[Cookie]
-----> PANA-Start-Request-Answer (y,x)[Cookie]
// Termination phase // Authentication phase
-----> PANA-Termination-Request(y+5,x+4)[MAC] <----- PANA-Auth-Request(x+1,y)[EAP]
<----- PANA-Termination-Answer (x+5,y+5)[MAC] -----> PANA-Auth-Answer(y+1,x+1)[EAP]
<----- PANA-Auth-Request(x+2,y+1)[EAP]
-----> PANA-Auth-Answer(y+2,x+2)[EAP]
<----- PANA-Bind-Request(x+3,y+2)
[EAP{Success}, Device-Id, Lifetime, Protection-Cap., MAC]
-----> PANA-Bind-Answer(y+3,x+3)
[Device-Id, Protection-Cap., MAC]
Figure 8: A Complete Message Sequence // Re-authentication
<----- PANA-Reauth-Request (x+4,y+3)[MAC]
-----> PANA-Reauth-Answer (y+4,x+4)[MAC]
4.7 Device ID choice // Termination phase
-----> PANA-Termination-Request(y+5,x+4)[MAC]
<----- PANA-Termination-Answer (x+5,y+5)[MAC]
Figure 8: A Complete Message Sequence
PaC has to pick a device identifier to provide for PANA exchanges. 4.7 Device ID Choice
In this version of the specification, device ID is considered to be
fixed. Future versions might enable changing it during a PANA
session.
A PaC will configure an IP address before PANA if it can. It might A PaC SHOULD configure an IP address before PANA if it can. It might
either have a pre-configured IP address, or have to obtain one via either have a pre-configured IP address, or have to obtain one via
dynamic methods such as DHCP or stateless address autoconfiguration. dynamic methods such as DHCP or stateless address autoconfiguration.
Dynamic methods may or may not succeed depending on the local Dynamic methods may or may not succeed depending on the local
security policy. In networks where the PaCs need to use PANA prior security policy. In networks where clients have to be authorized
to address configuration, EPs will detect the PaCs attempt to get IP before they are allowed to obtain an IP address, EPs will detect the
address and help PAA to initiate authentication. associated activity and PANA protocol will be engaged before the
clients can configure a valid IP address.
Either an IP address or link-layer address should be used as device Either an IP address or a link-layer address SHOULD be used as device
DI at any time. The only case an IP address should be used as ID at any time. It is assumed that PAA knows the security mechanisms
device ID is when IPsec will be used for protecting data traffic being provided or required on the access network (e.g., based on
after initial authentication. Any other time a link-layer address physical security, link-layer ciphers enabled before or after PANA,
can be used by both PAA and PaC as device ID. It is assumed that PAA or IPsec). When IPsec-based mechanism [I-D.ietf-pana-ipsec] is the
knows the security mechanisms being provided or required on the choice of access control, PAA SHOULD provide its IP address as device
access network (e.g., physical security, link-layer ciphers prior to ID, and expect the PaC to provide its IP address in return. In all
PANA, link-layer ciphers enabled after PANA, IPsec). When IPsec is other cases, link-layer addresses can be provided from both sides.
the choice of data ciphering, PAA should provide its IP address as
device ID, and expect the PaC to provide its IP address if it has
one. In all other cases, link-layer addresses can be provided from
both sides.
When IPsec ciphering is used but the PaC uses an unspecified IP When IPsec-based access control is used but the PaC is using an
address in the authentication phase, it MUST use its MAC address for unspecified IP address in the authentication phase, the device ID
the device identifier until the PaC is configured with a specified reported by the PaC MUST be either 0.0.0.0 or 0::0. This device ID
IP address that is used for IPsec ciphering. Once such a specified MUST be recorded as a temporary one by the PAA until the PaC obtains
IP address is configured, the PaC MUST update the device identifier a valid one and informs the PAA. Eventually PaC MUST obtain an IP
registered on the PAA from the MAC address to the IP address by address, possibly by relying on the newly-created PANA session
initiating a PANA-Reauth-Request/PANA-Reauth-Answer exchange in [I-D.tschofenig-pana-bootstrap-rfc3118], in order to gain full access
which the IP address of the PaC is contained in the Device-Id AVP to the network. PaC MUST update the device identifier registered on
contained in the PANA-Reauth-Request message sent from the PaC. the PAA from unspecified to the valid IP address by initiating a
PANA-Reauth-Request/PANA-Reauth-Answer exchange in which the IP
address of the PaC is contained in the Device-Id AVP.
4.8 Refresh Interval Negotiation 4.8 Session Lifetime
The authentication phase also determines the PANA session lifetime The authentication phase determines the PANA session lifetime when
when authorization succeeds. The Session-Lifetime AVP (to be the network access authorization succeeds. The Session-Lifetime AVP
defined, Code XXX) is used to determine the valid lifetime of PANA MAY be optionally included in the PANA-Bind-Request message to inform
session. This AVP MUST NOT be included in any message other than the PaC about the valid lifetime of the PANA session. It MUST be ignored
PANA-Bind-Request and PANA-Bind-Anser message. It MUST be ignored when included in other PANA messages. When there are multiple EAP
when received in other messages or the authorization result is a authentication taking place, this AVP SHOULD be included after the
failure. final authentication.
This AVP carries the maximum session lifetime offered by the network The lifetime is a non-negotiable parameter that can be used by PaC to
when included in the PANA-Bind-Request sent by the PAA. If it is manage PANA-related state. PaC does not have to perform any actions
omitted, or contains the value 0xFFFFFFFF, this means the session when the lifetime expires, other than optionally purging local state.
lifetime is infinity. This AVP carries the requested session
lifetime when it is sent by the PaC. If requested session lifetime PAA SHOULD initiate EAP authentication before the current session
is greater than the offered lifetime, then it is ignored and the lifetime expires.
offered lifetime becomes the session lifetime. The requested
lifetime becomes the session lifetime if it is less than or equal to PaC and PAA MAY optionally rely on lower-layer indications to
the offered lifetime. The PaC MUST perform a PANA authentication (by expedite the detection of a disconnected peer. Availability and
sending a PANA-Auth-Request andnot a PANA-Reauth-Request) before the reliability of such indications depend on the specific access
session lifetime expires. Failure to do so yields in PaC losing technologies. PANA peer can use PANA-Reauth-Request message to verify
network access. the disconnection before taking an action.
The session lifetime parameter is not related to the transmission of
PANA-Reauth-Request messages. These messages can be used for
asynchronously verifying the liveness of the peer and enabling
mobility optimizations. The decision to send PANA-Reauth-Request
message is taken locally and does not require coordination between
the peers.
4.9 Mobility Handling 4.9 Mobility Handling
If PaC wants to resume an ongoing PANA session after connecting to When a PaC wants to resume an ongoing PANA session after connecting
another link in the same access network, it can send the unexpired to another link in the same access network, it MAY send the unexpired
PANA session id in its PANA-Start-Request message. In the absence of PANA session identifier in its PANA-Start-Answer message. In the
session id AVP in this message, PAA can assume this is a fresh absence of a Session-Id AVP in this message, PAA MUST assume this is
session and assigns a new session ID in the first PANA-Auth-Request a fresh session and continue its normal execution.
message.
If PAA receives a session id in the PANA-Start-Request message, and If PAA receives a session identifier in the PANA-Start-Answer
it is configured to enable fast re-authentication, it SHOULD message, and it is configured to enable fast re-authentication, it
retrieve the PANA SA from the previous PAA of the PaC. Determining SHOULD retrieve the PANA session attributes from the previous PAA of
the previous PAA of the PaC by using the PANA session id is outside the PaC. The mechanism required to determine the previous PAA of the
the scope of this protocol. A possible solution is to embed thePAA PaC by relying on the PANA session identifier is outside the scope of
identifier into the message. Furthermore, the mechanism required to PANA protocol. A possible solution is to embed the PAA identifier in
retrieve the PANA SA from the previous PAA is outside the scope of the PANA session identifier. Furthermore, the mechanism required to
PANA protocol. Seamoby Context Transfer Protocol [CTP] might be retrieve the session attributes from the previous PAA is outside the
useful here. scope of this protocol. Seamoby Context Transfer Protocol
[I-D.ietf-seamoby-ctp] might be useful for this purpose.
If the PAA is not configured to enable fast re-authentication, or When the PAA is not configured to enable fast re-authentication, or
can not retrieve the PANA SA, or the PANA SA has expired, the PAA can not retrieve the PANA session attributes, or the PANA session has
MUST send the PANA-Start-Request message with a new session id and already expired (i.e., session lifetime is zero), the PAA MUST send
let the PANA exchange take its usual course. Otherwise, PAA MUST the PANA-Auth-Request message with the new session identifier and let
continue the PANA session with a PANA_Reauth exchange (rather than the PANA exchange take its usual course. This action will engage EAP
PANA_Auth exchange which, in most of the times, means full authentication and create a fresh PANA session from scratch.
authentication). Device ID AVPs MUST be included in this exchange to
bind the new DIs to the PANA SA.
TBD: This is a proposal and requires further thoughts. In case the new PAA retrieves the on-going PANA session attributes
from the previous PAA, the PANA session continues with a PANA-Reauth
exchange. The MAC AVP contained in the PANA-Reauth messages MUST be
generated and verified by using the retrieved PANA SA attributes.
This exchange MUST also include Session-Id AVP that contains the
newly assigned session identifier, and Device-Id AVP. A new PANA
session is created upon successful completion of this exchange. This
session inherits only the session lifetime, protection capability,
and MSK attributes from the previous session. Other attributes are
generated based on the PANA exchanges on the new link. While MSK
stays the same, a new PANA_MAC_Key is computed using the new
parameters. Subsequent MAC-AVPs are processed using this new PANA SA.
4.10 Event Notification 4.10 Event Notification
Upon detecting the need to authenticate a client, EP can send a Upon detecting the need to authenticate a client, EP can send a
trigger message to the PAA on behalf of the PaC. This can be one of trigger message to the PAA on behalf of the PaC. This can be one of
the messages provided by the PAA-to-EP protocol, or, in the absence the messages provided by the PAA-to-EP protocol, or, in the absence
of such a facility, PANA-PAA_Discover can be used as well. This of such a facility, PANA-PAA_Discover can be used as well. This
message MUST carry the device identifier of the PaC. So that, the message MUST carry the device identifier of the PaC. So that, the PAA
PAA can send the unsolicited PANA-Start-Request message directly to can send the unsolicited PANA-Start-Request message directly to the
the PaC. If the link between the EP and PAA is not physically PaC. If the link between the EP and PAA is not physically secured,
secured, this message sent from EP to PAA MUST be cryptographically this message sent from EP to PAA MUST be cryptographically protected
protected (e.g., by using IPsec). (e.g., by using IPsec).
4.11 PaC Implications 4.11 PaC Implications
- PaC state machine. [TBD] o PaC state machine. [TBD]
4.12 PAA Implications 4.12 PAA Implications
- PAA state machine. [TBD] o PAA state machine. [TBD]
5 PANA Security Association Establishment 5. PANA Security Association Establishment
When PANA is used over an already established secure channel, such When PANA is used over an already established secure channel, such as
as physically secured wires or ciphered link-layers, we can physically secured wires or ciphered link-layers, we can reasonably
reasonably assume that man-in-the-middle attack or service theft is assume that man-in-the-middle attack or service theft is not possible
not possible [THREATS]. [I-D.ietf-pana-threats-eval].
Anywhere else where there is no secure channel prior to PANA, the Anywhere else where there is no secure channel prior to PANA, the
protocol needs to protect itself against such attacks. The device protocol needs to protect itself against such attacks. The device
identifier that is used during the authentication needs to be identifier that is used during the authentication needs to be
verified at the end of the authentication to prevent service theft verified at the end of the authentication to prevent service theft
and DoS attacks. Additionally, a free loader should be prevented and DoS attacks. Additionally, a free loader should be prevented from
from spoofing data packets by using the device identifier of an spoofing data packets by using the device identifier of an already
already authorized legitimate client. Both of these requirements authorized legitimate client. Both of these requirements necessitate
necessitate generation of a security association between the generation of a security association between the PaC and the PAA at
PaC and the PAA at the end of the authentication. This can only be the end of the authentication. This can only be done when the
done when the authentication method used can generate cryptographic authentication method used can generate cryptographic keys. Use of
keys. Use of secret keys can prevent attacks which would otherwise secret keys can prevent attacks which would otherwise be very easy to
be very easy to launch by eavesdropping on and spoofing traffic over launch by eavesdropping on and spoofing traffic over an insecure
an insecure link. link.
PANA relies on EAP and the EAP methods to provide a session key in PANA relies on EAP and the EAP methods to provide a session key in
order to establish a PANA security association. An example of such a order to establish a PANA security association. An example of such a
method is EAP-TLS [EAPTLS], whereas EAP-MD5 [RFC2284] is an example method is EAP-TLS [RFC2716], whereas EAP-MD5 [RFC2284] is an example
of a method that cannot create such keying material. The choice of of a method that cannot create such keying material. The choice of
EAP method becomes important, as already discussed in the next EAP method becomes important, as already discussed in the next
section. section.
This keying material is already used within PANA during the final This keying material is already used within PANA during the final
handshake. This handshake ensures that the device identifier that is handshake. This handshake ensures that the device identifier that is
bound to the PaC at the end of the authentication process is not bound to the PaC at the end of the authentication process is not
coming from a man-in-the-middle, but from the legitimate PaC. coming from a man-in-the-middle, but from the legitimate PaC.
Knowledge of the same keying material on both PaC and the PAA helps Knowledge of the same keying material on both PaC and the PAA helps
prove this. The other use of the keying material will be discussed prove this. The other use of the keying material will be discussed in
in sections 7 and 8. Section 7 and Section 8.
6 Authentication Method Choice 6. Authentication Method Choice
Authentication methods' capabilities and therefore applicability to Authentication methods' capabilities and therefore applicability to
various environments differ among them. Not all methods provide various environments differ among them. Not all methods provide
support for mutual authentication, key derivation or distribution, support for mutual authentication, key derivation or distribution,
and DoS attack resiliency that are necessary for operating in and DoS attack resiliency that are necessary for operating in
insecure networks. Such networks might be susceptible to insecure networks. Such networks might be susceptible to
eavesdropping and spoofing, therefore a stronger authentication eavesdropping and spoofing, therefore a stronger authentication
method needs to be used to prevent attacks on the client and method needs to be used to prevent attacks on the client and the
the network. network.
The authentication method choice is a function of the underlying The authentication method choice is a function of the underlying
security of the network (e.g., physically secured, shared link, security of the network (e.g., physically secured, shared link,
etc.). It is the responsibility of the user and the network operator etc.). It is the responsibility of the user and the network operator
to pick the right method for authentication. PANA carries EAP to pick the right method for authentication. PANA carries EAP
regardless of the EAP method used. It is outside the scope of PANA regardless of the EAP method used. It is outside the scope of PANA to
to mandate, recommend, or limit use of any authentication methods. mandate, recommend, or limit use of any authentication methods. PANA
PANA cannot increase the strength of a weak authentication method to cannot increase the strength of a weak authentication method to make
make it suitable for an insecure environment. There are some EAP- it suitable for an insecure environment. There are some EAP- based
based approaches to achieve this goal (see [PEAP],[TTLS],[EAP- approaches to achieve this goal (see
IKEv2]). PANA can carry these EAP encapsulating methods but it does [I-D.josefsson-pppext-eap-tls-eap],[I-D.ietf-pppext-eap-ttls],[I-D.tschofenig-eap-ikev2]
not concern itself with how they achieve protection for the weak ). PANA can carry these EAP encapsulating methods but it does not
methods (i.e., their EAP method payloads). concern itself with how they achieve protection for the weak methods
(i.e., their EAP method payloads).
7 Filter Rule Installation 7. Filter Rule Installation
PANA protocol provides client authentication and authorization PANA protocol provides client authentication and authorization
functionality for securing network access. The other component of a functionality for securing network access. The other component of a
complete solution is the access control which ensures that only complete solution is the access control which ensures that only
authenticated and authorized clients can gain access to the network. authenticated and authorized clients can gain access to the network.
PANA enables access control by identifying legitimate clients and PANA enables access control by identifying legitimate clients and
generating filtering information for access control mechanisms. generating filtering information for access control mechanisms.
Getting this filtering information to the EPs (Enforcement Points) Getting this filtering information to the EPs (Enforcement Points)
and performing filtering are outside the scope of PANA. and performing filtering are outside the scope of PANA.
Access control can be achieved by placing EPs in the network for Access control can be achieved by placing EPs in the network for
policing the traffic flow. EPs should prevent data traffic from and policing the traffic flow. EPs should prevent data traffic from and
to any unauthorized client unless it's PANA traffic. When a client to any unauthorized client unless it's PANA traffic. When a client is
is authenticated and authorized, PAA should notify EP(s) and ask for authenticated and authorized, PAA should notify EP(s) and ask for
changing filtering rules to allow traffic for a recently authorized changing filtering rules to allow traffic for a recently authorized
client. There needs to be a protocol between PAA and EP(s) when client. There needs to be a protocol between PAA and EP(s) when these
these entities are not co-located. PANA Working Group will not be entities are not co-located. PANA Working Group will not be defining
defining a new protocol for this interaction. Instead, it will a new protocol for this interaction. Instead, it will (preferably)
(preferably) identify one of the existing protocols that can fit the identify one of the existing protocols that can fit the requirements.
requirements. Possible candidates include but not limited to COPS, Possible candidates include but not limited to COPS, SNMP, DIAMETER.
SNMP, DIAMETER. This task is similar to what MIDCOM Working Group is This task is similar to what MIDCOM Working Group is trying to
trying to achieve, therefore some of the MIDCOM's output might be achieve, therefore some of the MIDCOM's output might be useful here.
useful here.
EPs location in the network topology should be appropriate for EPs' location in the network topology should be appropriate for
performing access control functionality. The closest IP-capable performing access control functionality. The closest IP-capable
access device to the client devices is the logical choice. PAA and access device to the client devices is the logical choice. PAA and
EPs on an access network should be aware of each other as this is EPs on an access network should be aware of each other as this is
necessary for access control. Generally this can be achieved by necessary for access control. Generally this can be achieved by
manual configuration. Dynamic discovery is another possibility, but manual configuration. Dynamic discovery is another possibility, but
this is clearly outside the scope of PANA. this is clearly outside the scope of PANA.
Filtering rules generally include device identifiers for a client, Filtering rules generally include device identifiers for a client,
and also cryptographic keying material when needed. Such keys are and also cryptographic keying material when needed. Such keys are
needed when attackers can eavesdrop and spoof on the device needed when attackers can eavesdrop and spoof on the device
identifiers easily. They are used with link-layer or network-layer identifiers easily. They are used with link-layer or network-layer
ciphering to provide additional protection. For issues regarding ciphering to provide additional protection. For issues regarding
data-origin authentication see Section 8. data-origin authentication see Section 8.
8 Data Traffic Protection 8. Data Traffic Protection
Protecting data traffic of authenticated and authorized clients from Protecting data traffic of authenticated and authorized clients from
others is another component of providing a complete secure network others is another component of providing a complete secure network
access solution. Authentication, integrity and replay protection of access solution. Authentication, integrity and replay protection of
data packets are needed to prevent spoofing when the underlying data packets are needed to prevent spoofing when the underlying
network is not physically secured. Encryption is needed when network is not physically secured. Encryption is needed when
eavesdropping is a concern in the network. eavesdropping is a concern in the network.
When the network is physically secured, or the link-layer ciphering When the network is physically secured, or the link-layer ciphering
is already enabled prior to PANA, data traffic protection is already is already enabled prior to PANA, data traffic protection is already
in place. In other cases, enabling link-layer ciphering or network- in place. In other cases, enabling link-layer ciphering or network-
layer ciphering might rely on PANA authentication. The user and layer ciphering might rely on PANA authentication. The user and
network have to make sure an appropriate EAP method that can network have to make sure an appropriate EAP method that can generate
generate required keying materials is used. Once the keying material required keying materials is used. Once the keying material is
is available, it needs to be provided to the EP(s) for use with available, it needs to be provided to the EP(s) for use with
ciphering. ciphering.
Network-layer ciphering, i.e., IPsec, can be used when data traffic Network-layer ciphering, i.e., IPsec, can be used when data traffic
protection is required but link-layer ciphering capability is not protection is required but link-layer ciphering capability is not
available. Note that a simple shared secret generated by an EAP available. Note that a simple shared secret generated by an EAP
method is not readily usable by IPsec for authentication and method is not readily usable by IPsec for authentication and
encryption of IP packets. Fresh and unique session key derived from encryption of IP packets. Fresh and unique session key derived from
the EAP method is still insufficient to produce an IPsec SA since the EAP method is still insufficient to produce an IPsec SA since
both traffic selectors and other IPsec SA parameters are missing. both traffic selectors and other IPsec SA parameters are missing.
The shared secret can be used in conjunction with a key management The shared secret can be used in conjunction with a key management
protocol like IKE [RFC2409] to turn a simple shared secret into the protocol like IKE [RFC2409] to turn a simple shared secret into the
required IPsec SA. The details of this mechanism is outside the required IPsec SA. The details of this mechanism is outside the scope
scope of PANA protocol, and it can be outlined in a separate of PANA protocol [I-D.ietf-pana-ipsec], PANA provides bootstrapping
Internet-Draft. PANA provides bootstrapping functionality for such a functionality for such a mechanism by carrying EAP methods that can
mechanism by carrying EAP methods that can generate initial keying generate initial keying material.
material.
Using network-layer ciphers should be regarded as a substitute for Using network-layer ciphers should be regarded as a substitute for
link-layer ciphers when the latter is not available. IKE involves link-layer ciphers when the latter is not available. IKE involves
several message exchanges which can incur additional delay in several message exchanges which can incur additional delay in getting
getting basic IP connectivity for a mobile device. Such a latency is basic IP connectivity for a mobile device. Such a latency is
inevitable when there is no other alternative and this level of inevitable when there is no other alternative and this level of
protection is required. Network-layer ciphering can also be used in protection is required. Network-layer ciphering can also be used in
addition to link-layer ciphering if the added benefits outweigh its addition to link-layer ciphering if the added benefits outweigh its
cost to the user and the network. cost to the user and the network.
9 Message Formats 9. Message Formats
This section defines message formats for PANA protocol. This section defines message formats for PANA protocol.
9.1 PANA Header 9.1 PANA Header
A summary of the PANA header format is shown below. The fields are A summary of the PANA header format is shown below. The fields are
transmitted in network byte order. transmitted in network byte order.
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
skipping to change at page 23, line 39 skipping to change at page 27, line 30
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Transmitted Sequence Number | | Transmitted Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Received Sequence Number | | Received Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AVPs ... | AVPs ...
+-+-+-+-+-+-+-+-+-+-+-+-+- +-+-+-+-+-+-+-+-+-+-+-+-+-
Version Version
This Version field MUST be set to 1 to indicate PANA Version 1. This Version field MUST be set to 1 to indicate PANA Version 1.
Message Length Message Length
The Message Length field is three octets and indicates the The Message Length field is three octets and indicates the length
length of the PANA message including the header fields. of the PANA message including the header fields.
Flags Flags
The Flags field is eight bits. The following bits are assigned: The Flags field is eight bits. The following bits are assigned:
0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
|R r r r F r r r| |R r r r S r r r|
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
R(equest)
- If set, the message is a request. If cleared, R(equest)
the message is an answer.
F(inish) If set, the message is a request. If cleared, the message is an
- F-flag in the PANA header indicates if this was answer.
the final authentication from sender's
perspective. If PAA enables two separate
authentication, it should not set F-flag in the
PANA-Bind-Request message after the first EAP
method.
r(eserved) S(eparate)
- these flag bits are reserved for future use, When the S-flag is set in a PANA-Start-Request message it
and MUST be set to zero, and ignored by the indicates that PAA is willing to offer separate EAP
receiver. authentication for NAP and ISP. When the S-flag is set in a
PANA-Start-Answer message it indicates that PaC accepts on
performing separate EAP authentication for NAP and ISP."
r(eserved)
these flag bits are reserved for future use, and MUST be set to
zero, and ignored by the receiver.
Message Type Message Type
The Message Type field is three octets, and is used in order to The Message Type field is three octets, and is used in order to
communicate the message type with the message. The 24-bit communicate the message type with the message. The 24-bit address
address space is managed by IANA [IANAWEB]. space is managed by IANA [ianaweb]. PANA uses its own address
space for this field.
Transmitted Sequence Number Transmitted Sequence Number
The Transmitted Sequence Number field contains the monotonically The Transmitted Sequence Number field contains the monotonically
increasing 32 bit sequence number that the message sender increasing 32 bit sequence number that the message sender
increments every time a new packet is sent. increments every time a new PANA message is sent.
Received Sequence Number Received Sequence Number
The Received Sequence Number field contains the 32 bit The Received Sequence Number field contains the 32 bit transmitted
transmitted sequence number that the peer has last received. sequence number that the message sender has last received from its
peer.
AVPs AVPs
AVPs are a method of encapsulating information relevant to the AVPs are a method of encapsulating information relevant to the
PANA message. See section 9.2 for more information on AVPs. PANA message. See section Section 9.2 for more information on
AVPs.
9.2 AVP Header 9.2 AVP Header
Each AVP of type OctetString MUST be padded to align on a 32-bit
boundary, while other AVP types align naturally. A number of
zero-valued bytes are added to the end of the AVP Data field till a
word boundary is reached. The length of the padding is not reflected
in the AVP Length field [RFC3588].
The fields in the AVP header MUST be sent in network byte order. The
format of the header is:
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AVP Code | | AVP Code |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AVP Flags | AVP Length | | AVP Flags | AVP Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Vendor-Id (opt) | | Vendor-Id (opt) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Data ... | Data ...
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
AVP Code AVP Code
The AVP Code, combined with the Vendor-Id field, identifies the The AVP Code, combined with the Vendor-Id field, identifies the
attribute uniquely. AVP numbers are allocated by IANA [IANAWEB]. attribute uniquely. AVP numbers are allocated by IANA [ianaweb].
PANA uses its own address space for this field although some of
the AVP formats are borrowed from Diameter protocol [RFC3588].
AVP Flags AVP Flags
The AVP Flags field is eight bits. The following bits are The AVP Flags field is eight bits. The following bits are
assigned: assigned:
0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
|V M r r r r r r| |V M r r r r r r|
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
M(andatory) M(andatory)
- The 'M' Bit, known as the Mandatory bit, The 'M' Bit, known as the Mandatory bit, indicates whether
indicates whether support of the AVP is support of the AVP is required.
required.
V(endor) V(endor)
- The 'V' bit, known as the Vendor-Specific bit, The 'V' bit, known as the Vendor-Specific bit, indicates
indicates whether the optional Vendor-Id field whether the optional Vendor-Id field is present in the AVP
is present in the AVP header. header.
r(eserved) r(eserved)
- these flag bits are reserved for future use, these flag bits are reserved for future use, and MUST be set to
and MUST be set to zero, and ignored by the zero, and ignored by the receiver.
receiver.
AVP Length AVP Length
The AVP Length field is three octets, and indicates the number The AVP Length field is three octets, and indicates the number of
of octets in this AVP including the AVP Code, AVP Length, AVP octets in this AVP including the AVP Code, AVP Length, AVP Flags,
Flags, and the AVP data. and the AVP data
Vendor-Id Vendor-Id
The Vendor-Id field is present if the 'V' bit is set in the AVP The Vendor-Id field is present if the 'V' bit is set in the AVP
Flags field. The optional four-octet Vendor-Id field contains Flags field. The optional four-octet Vendor-Id field contains the
the uniquely assigned id value, encoded in network byte order. uniquely assigned id value, encoded in network byte order. Any
Any vendor wishing to implement a vendor-specific PANA AVP MUST vendor wishing to implement a vendor-specific PANA AVP MUST use
use their own Vendor-Id along with their privately managed AVP their own Vendor-Id along with their privately managed AVP address
address space, guaranteeing that they will not collide with any space, guaranteeing that they will not collide with any other
other vendor's vendor-specific AVP(s), nor with future IETF vendor's vendor-specific AVP(s), nor with future IETF
applications. applications.
Data Data
The Data field is zero or more octets and contains information The Data field is zero or more octets and contains information
specific to the Attribute. The format and length of the Data specific to the Attribute. The format and length of the Data field
field is determined by the AVP Code and AVP Length fields. is determined by the AVP Code and AVP Length fields.
9.3 PANA Messages 9.3 PANA Messages
Figure 9lists all PANA messages defined in this document Figure 9 lists all PANA messages defined in this document
Message Direction: PaC---PAA
----------------------------------
PANA-PAA-Discover -------->
PANA-Start-Request <-------- Message Direction: PaC---PAA
PANA-Start-Answer --------> ----------------------------------
PANA-PAA-Discover -------->
PANA-Auth-Request <-------- PANA-Start-Request <--------
PANA-Auth-Answer --------> PANA-Start-Answer -------->
PANA-Bind-Request <-------- PANA-Auth-Request <--------
PANA-Bind-Answer --------> PANA-Auth-Answer -------->
PANA-Reauth-Request <-------> PANA-Bind-Request <--------
PANA-Reauth-Answer <-------> PANA-Bind-Answer -------->
PANA-Termination-Request <-------> PANA-Reauth-Request <------->
PANA-Termination-Answer <-------> PANA-Reauth-Answer <------->
PANA-Error <-------> PANA-Termination-Request <------->
PANA-Termination-Answer <------->
Figure 9: PANA Message Overview PANA-Error <------->
Figure 9: PANA Message Overview
Additionally the EP can also send a PANA-PAA-Discover message to the Additionally the EP can also send a PANA-PAA-Discover message to the
PAA. PAA.
9.3.1 Message specifications 9.3.1 Message Specifications
Every PANA message MUST include a corresponding ABNF Every PANA message MUST include a corresponding ABNF [RFC2234]
[RFC2234] specification found in [DIAMETER]. Note that PANA specification found in [RFC3588]. Note that PANA messages have a
messages have a different header format compared to Diameter. different header format compared to Diameter.
Example: Example:
message ::= < PANA-Header: <Message type>, message ::= < PANA-Header: <Message type>, [REQ] [SEP] >
[REQ], [FIN] * [ AVP ]
* [ AVP ]
9.3.2 PANA-PAA-Discover (PDI) 9.3.2 PANA-PAA-Discover (PDI)
The PANA-PAA-Discover (PDI) message is used to discover the address The PANA-PAA-Discover (PDI) message is used to discover the address
of PAA(s). Both sequence numbers in this message are set to zero of PAA(s). Both sequence numbers in this message are set to zero (0).
(0). If the EP detects a new PaC and sends the PANA-PAA-Discover to If the EP detects a new PaC and sends the PANA-PAA-Discover to the
the PAA, it MUST include the Device-Id of the PaC. PAA, it MUST include the Device-Id of the PaC.
PANA-PAA-Discover ::= < PANA-Header: 1 > PANA-PAA-Discover ::= < PANA-Header: 1 >
0*1 < Device-Id > 0*1 < Device-Id >
* [ AVP ] * [ AVP ]
9.3.3 PANA-Start-Request (PSR) 9.3.3 PANA-Start-Request (PSR)
PANA-Start-Request (PSR) is sent by the PAA to the PaC. The PAA sets PANA-Start-Request (PSR) is sent by the PAA to the PaC. The PAA sets
the transmission sequence number to an initial random value. The the transmission sequence number to an initial random value. The
received sequence number is set to zero (0). received sequence number is set to zero (0).
PANA-Start-Request ::= < PANA-Header: 2, REQ > PANA-Start-Request ::= < PANA-Header: 2, REQ [SEP] >
[ Cookie ] [ Cookie ]
* [ AVP ] [ NAP-Information ]
* [ ISP-Information ]
* [ AVP ]
9.3.4 PANA-Start-Answer (PSA) 9.3.4 PANA-Start-Answer (PSA)
PANA-Start-Answer (PSA) is sent by the PaC to the PAA in response to PANA-Start-Answer (PSA) is sent by the PaC to the PAA in response to
a PANA-Start-Request message. The PANA_start message transmission a PANA-Start-Request message. The PANA_start message transmission
sequence number field is copied to the received sequence number sequence number field is copied to the received sequence number
field. The field. The transmission sequence number is set to initial random
transmission sequence number is set to initial random value. value.
PANA-Start-Answer ::= < PANA-Header: 3 > PANA-Start-Answer ::= < PANA-Header: 2 [SEP] >
[ Cookie ] [ Cookie ]
* [ AVP ] [ ISP-Information ]
* [ AVP ]
9.3.5 PANA-Auth-Request (PAR) 9.3.5 PANA-Auth-Request (PAR)
PANA-Auth-Request (PAR) is sent by the PAA to the PaC. PANA-Auth-Request (PAR) is sent by the PAA to the PaC.
PANA-Auth-Request ::= < PANA-Header: 4, REQ > PANA-Auth-Request ::= < PANA-Header: 3, REQ >
< Session-Id > < Session-Id >
< EAP-Payload > < EAP-Payload >
* [ AVP ] 0*1 [ NAP-Information ]
0*1 < MAC > 0*1 [ ISP-Information ]
* [ AVP ]
0*1 < MAC >
(Both NAP-Information and ISP-Information MUST NOT be included at the
same time)"
9.3.6 PANA-Auth-Answer (PAN) 9.3.6 PANA-Auth-Answer (PAN)
PANA-Auth-Answer (PAN) is sent by the PaC to the PAA in response to PANA-Auth-Answer (PAN) is sent by the PaC to the PAA in response to a
a PANA-Auth-Request message. PANA-Auth-Request message.
PANA-Auth-Answer ::= < PANA-Header: 5 > PANA-Auth-Answer ::= < PANA-Header: 3 >
< Session-Id > < Session-Id >
< EAP-Payload > < EAP-Payload >
* [ AVP ] * [ AVP ]
0*1 < MAC > 0*1 < MAC >
9.3.7 PANA-Bind-Request (PBR) 9.3.7 PANA-Bind-Request (PBR)
PANA-Bind-Request (PBR) is sent by the PAA to the PaC. PANA-Bind-Request (PBR) is sent by the PAA to the PaC.
PANA-Bind-Request ::= < PANA-Header: 6, REQ, [FIN] > PANA-Bind-Request ::= < PANA-Header: 4, REQ >
< Session-Id > < Session-Id >
< Device-Id > < Device-Id >
{ EAP-Payload } { EAP-Payload }
{ Result-Code } { Result-Code }
[ Protection-Capability ] [ Session-Lifetime ]
* [ AVP ] [ Protection-Capability ]
0*1 < MAC > * [ AVP ]
0*1 < MAC >
9.3.8 PANA-Bind-Answer (PBA) 9.3.8 PANA-Bind-Answer (PBA)
PANA-Bind-Answer (PBA) is sent by the PaC to the PAA in response to PANA-Bind-Answer (PBA) is sent by the PaC to the PAA in response to a
a PANA-Result-Request message. PANA-Result-Request message.
PANA-Bind-Answer ::= < PANA-Header: 7, [FIN] > PANA-Bind-Answer ::= < PANA-Header: 4 >
< Session-Id > < Session-Id >
< Device-Id > < Device-Id >
* [ AVP ] * [ AVP ]
0*1 < MAC > 0*1 < MAC >
9.3.9 PANA-Reauth-Request (PRAR) 9.3.9 PANA-Reauth-Request (PRAR)
PANA-Reauth-Request (PRAR) is either sent by the PaC or the PAA. PANA-Reauth-Request (PRAR) is either sent by the PaC or the PAA.
PANA-Reauth-Request ::= < PANA-Header: 8, REQ > PANA-Reauth-Request ::= < PANA-Header: 5, REQ >
< Session-Id > < Session-Id >
< Device-Id > < Device-Id >
* [ AVP ] * [ AVP ]
0*1 < MAC >
0*1 < MAC >
9.3.10 PANA-Reauth-Answer (PRAA) 9.3.10 PANA-Reauth-Answer (PRAA)
PANA-Reauth-Answer (PRAA) is sent in response to a PANA-Reauth-Answer (PRAA) is sent in response to a
PANA-Reauth-Request. PANA-Reauth-Request.
PANA-Reauth-Answer ::= < PANA-Header: 9 > PANA-Reauth-Answer ::= < PANA-Header: 5 >
< Session-Id > < Session-Id >
< Device-Id > < Device-Id >
* [ AVP ] * [ AVP ]
0*1 < MAC > 0*1 < MAC >
9.3.11 PANA-Termination-Request (PTR) 9.3.11 PANA-Termination-Request (PTR)
PANA-Termination-Request (PTR) is sent either by the PaC or the PAA. PANA-Termination-Request (PTR) is sent either by the PaC or the PAA.
PANA-Termination-Request ::= < PANA-Header: 10, REQ > PANA-Termination-Request ::= < PANA-Header: 6, REQ >
< Session-Id > < Session-Id >
< Termination-Cause > < Termination-Cause >
* [ AVP ] * [ AVP ]
0*1 < MAC > 0*1 < MAC >
9.3.12 PANA-Termination-Answer (PTA) 9.3.12 PANA-Termination-Answer (PTA)
PANA-Termination-Answer (PTA) is sent either by the PaC or the PAA PANA-Termination-Answer (PTA) is sent either by the PaC or the PAA in
in response to PANA-Termination-Request. response to PANA-Termination-Request.
PANA-Termination-Answer ::= < PANA-Header: 11 > PANA-Termination-Answer ::= < PANA-Header: 6 >
< Session-Id > < Session-Id >
* [ AVP ] * [ AVP ]
0*1 < MAC > 0*1 < MAC >
9.3.13 PANA-Error 9.3.13 PANA-Error (PER)
PANA-Error is sent either by the PaC or the PAA. PANA-Error is sent either by the PaC or the PAA.
TBD PANA-Error ::= < PANA-Header: 7 >
< Session-Id >
< Result-Code >
{ Failed-AVP }
* [ AVP ]
0*1 < MAC >
9.4 AVPs in PANA 9.4 AVPs in PANA
Some of the used AVPs are defined in this document and some of them Some of the used AVPs are defined in this document and some of them
are defined in other documents like [DIAMETER]. PANA proposes to are defined in other documents like [RFC3588]. PANA proposes to use
use the same name space with the Diameter spec. For temporary the same name space with the Diameter spec. For temporary allocation,
allocation, PANA uses AVP type numbers starting from 1024. PANA uses AVP type numbers starting from 1024.
9.4.1 MAC AVP 9.4.1 MAC AVP
The first octet (8 bits) of the MAC (Code 1024) AVP data contains The first octet (8 bits) of the MAC (Code 1024) AVP data contains the
the MAC algorithm type. Rest of the AVP data payload contains the MAC algorithm type. Rest of the AVP data payload contains the MAC
MAC encoded in network byte order. The Algorithm 8 bit name space encoded in network byte order. The Algorithm 8 bit name space is
is managed by IANA [IANAWEB]. The AVP length varies depending on managed by IANA [ianaweb]. The AVP length varies depending on the
the used algorithm. used algorithm.
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Algorithm | MAC... | Algorithm | MAC...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Algorithm Algorithm
1 HMAC-MD5 (16 bytes) 1 HMAC-MD5 (16 bytes)
2 HMAC-SHA1 (20 bytes) 2 HMAC-SHA1 (20 bytes)
MAC MAC
The Message Authentication Code is encoded in network byte The Message Authentication Code is encoded in network byte order.
order.
9.4.2 Device-Id AVP 9.4.2 Device-Id AVP
The first octet (8 bits) of the Device-Id (Code 1025) AVP data The first octet (8 bits) of the Device-Id (Code 1025) AVP data
contains the device type. Rest of the AVP data payload contains contains the device type. Rest of the AVP data payload contains the
the device data. The content and format of data (including byte device data. The content and format of data (including byte and bit
and bit ordering) is expected to be specified in specific ordering) for L2_ADDRESS is expected to be specified in specific
documents. For instance, [IPv6-ETHER]. documents that describe how IP operates over different link-layers.
For instance, [RFC2464].
UNKNOWN 0 RESERVED 0
IPV4_ADDRESS 1 IPV4_ADDRESS 1
IPV6_ADDRESS 2 IPV6_ADDRESS 2
L2_ADDRESS 3 L2_ADDRESS 3
For type 1 (IPv4 address), data size is 32 bits and for type 2 For type 1 (IPv4 address), data size is 32 bits and for type 2 (IPv6
(IPv6 address), data size is 128 bits. address), data size is 128 bits.
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Data... | | Type | Data... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
9.4.3 Session-Id AVP 9.4.3 Session-Id AVP
Session-Id AVP (Code 1026) has an opaque data field, which is Session-Id AVP (Code 1026) has an opaque data field, which is
assigned by the PAA. All messages pertaining to a specific PANA assigned by the PAA. All messages pertaining to a specific PANA
Session MUST include only one Session-Id AVP and the same value Session MUST include only one Session-Id AVP and the same value MUST
MUST be used throughout the lifetime of a session. When present, be used throughout the lifetime of a session. When present, the
the Session-Id SHOULD appear immediately following the PANA header. Session-Id SHOULD appear immediately following the PANA header.
The Session-Id MUST be globally and eternally unique, as it is The Session-Id MUST be globally and eternally unique, as it is meant
meant to identify a PANA Session without reference to any to identify a PANA Session without reference to any other
other information, and may be needed to correlate historical information, and may be needed to correlate historical authentication
authentication information with accounting information. information with accounting information.
The Session-Id AVP MAY use Diameter [DIAMETER] message The Session-Id AVP MAY use Diameter [RFC3588] message formatting. In
formatting. In this case the AVP code is 263. this case the AVP code is 263.
9.4.4 Cookie AVP 9.4.4 Cookie AVP
The Cookie AVP (Code 1027) is of type OctetString. The data is The Cookie AVP (Code 1027) is of type OctetString. The data is opaque
opaque and the exact content is outside the scope of this protocol. and the exact content is outside the scope of this protocol.
9.4.5 Protection-Capability AVP 9.4.5 Protection-Capability AVP
The Protection-Capability AVP (Code 1028) is of type Unsigned32. The Protection-Capability AVP (Code 1028) is of type Unsigned32. The
The AVP data is used as a collection of flags for different data AVP data is used as a collection of flags for different data
protection capability indications. Below is a list of specified protection capability indications. Below is a list of specified data
data protection capabilities: protection capabilities:
0 UNKNOWN 0 UNKNOWN
1 L2_PROTECTION 1 L2_PROTECTION
2 IPSEC_PROTECTION 2 IPSEC_PROTECTION
9.4.6 Termination-Cause AVP 9.4.6 Termination-Cause AVP
The Termination-Cause AVP is defined in [DIAMETER]. The Termination-Cause AVP (Code 1029) is of type of type Enumerated,
and is used to indicate the reason why a session was terminated on
the access device. The AVP data is used as a collection of flags The
following Termination-Cause AVP defined in [RFC3588] are used for
PANA.
LOGOUT 1 (PaC -> PAA) LOGOUT 1 (PaC -> PAA)
The user initiated a disconnect
(SERVICE_NOT_PROVIDED 2 (PAA -> PaC)) The client initiated a disconnect
This value is used when the user disconnected
prior to the receipt of the authorization answer
message.
BAD_ANSWER 3 (PaC -> PAA) ADMINISTRATIVE 4 (PAA -> Pac)
This value indicates that the authorization answer
received by the access device was not processed
successfully.
ADMINISTRATIVE 4 (PAA -> Pac) The client was not granted access, or was disconnected, due to
The user was not granted access, or was administrative reasons, such as the receipt of a
disconnected, due to administrative reasons, Abort-Session-Request message.
such as the receipt of a Abort-Session-Request
message.
(LINK_BROKEN 5) SESSION_TIMEOUT 8 (PAA -> PaC)
The communication to the user was abruptly
disconnected.
AUTH_EXPIRED 6 (PAA -> PaC) The session has timed out, and service has been terminated.
The user's access was terminated since its
authorized session time has expired.
(USER_MOVED 7) (PaC -> PAA) 9.4.7 Result-Code AVP
The user is receiving services from another
access device. (See issue16).
SESSION_TIMEOUT 8 (PAA -> PaC) The Result-Code AVP (AVP Code 1030) is of type Unsigned32 and
The user's session has timed out, and service indicates whether an EAP authentication was completed successfully or
has been terminated. whether an error occurred. Here are Result-Code AVP values taken
from [RFC3588] and adapted for PANA.
9.4.7 Result-Code AVP 9.4.7.1 Authentication Results Codes
The Result-Code AVP is defined in [DIAMETER]. These result code values inform the PaC about the EAP authentication
method success or failure.
SUCCESS 2001 PANA_SUCCESS 2001
COMMAND_UNSUPPORTED 3001
UNABLE_TO_DELIVER 3002 The EAP method authentication was successful (EAP-Success).
REALM_NOT_SERVED 3003
TOO_BUSY 3004 PANA_AUTHENTICATION_REJECTED 4001
INVALID_HDR_BITS 3008
INVALID_AVP_BITS 3009 The authentication process for the client failed (EAP-Failure).
AUTHENTICATION_REJECTED 4001
AVP_UNSUPPORTED 5001 PANA_AUTHORIZATION_REJECTED 5003
UNKNOWN_SESSION_ID 5002
AUTHORIZATION_REJECTED 5003 A request was received for which the client could not be
INVALID_AVP_VALUE 5004 authorized. This error could occur if the service requested is
MISSING_AVP 5005 not permitted to the client.
RESOURCES_EXCEEDED 5006
AVP_OCCURS_TOO_MANY_TIMES 5009 9.4.7.2 Protocol Error Result Codes
UNSUPPORTED_VERSION 5011
INVALID_AVP_LENGTH 5014 Protocol error result code values.
INVALID_MESSAGE_LENGTH 5015
PANA_MESSAGE_UNSUPPORTED 3001
Error code from PAA to PaC or from PaC to PAA. Message type not
recognized or supported.
PANA_UNABLE_TO_DELIVER 3002
Error code from PAA to PaC. PAA was unable to deliver the EAP
payload to the authentication server.
PANA_INVALID_HDR_BITS 3008
Error code from PAA to PaC or from PaC to PAA. A message was
received whose bits in the PANA header were either set to an
invalid combination, or to a value that is inconsistent with the
message type's definition.
PANA_INVALID_AVP_BITS 3009
Error code from PAA to PaC or from PaC to PAA. A message was
received that included an AVP whose flag bits are set to an
unrecognized value, or that is inconsistent with the AVP's
definition.
PANA_AVP_UNSUPPORTED 5001
Error code from PAA to PaC or from PaC to PAA. The received
message contained an AVP that is not recognized or supported and
was marked with the Mandatory bit. A PANA message with this error
MUST contain one or more Failed-AVP AVP containing the AVPs that
caused the failure.
PANA_UNKNOWN_SESSION_ID 5002
Error code from PAA to PaC or from PaC to PAA. The message
contained an unknown Session-Id. PAA MUST NOT send this error
result code value to PaC if PaC sent an unknown Session-Id in the
PANA-Start-Answer message (session resumption).
PANA_INVALID_AVP_VALUE 5004
Error code from PAA to PaC or from PaC to PAA. The message
contained an AVP with an invalid value in its data portion. A
PANA message indicating this error MUST include the offending AVPs
within a Failed-AVP AVP.
PANA_MISSING_AVP 5005
Error code from PAA to PaC or from PaC to PAA. The message did
not contain an AVP that is required by the message type
definition. If this value is sent in the Result-Code AVP, a
Failed-AVP AVP SHOULD be included in the message. The Failed-AVP
AVP MUST contain an example of the missing AVP complete with the
Vendor-Id if applicable. The value field of the missing AVP
should be of correct minimum length and contain zeroes.
PANA_RESOURCES_EXCEEDED 5006
Error code from PAA to PaC. A message was received that cannot be
authorized because the client has already expended allowed
resources. An example of this error condition is a client that is
restricted to one PANA session and attempts to establish a second
session.
PANA_CONTRADICTING_AVPS 5007
Error code from PAA to PaC. The PAA has detected AVPs in the
message that contradicted each other, and is not willing to
provide service to the client. One or more Failed-AVP AVPs MUST be
present, containing the AVPs that contradicted each other.
PANA_AVP_NOT_ALLOWED 5008
Error code from PAA to PaC or from PaC to PAA. A message was
received with an AVP that MUST NOT be present. The Failed-AVP AVP
MUST be included and contain a copy of the offending AVP.
PANA_AVP_OCCURS_TOO_MANY_TIMES 5009
Error code from PAA to PaC or from PaC to PAA. A message was
received that included an AVP that appeared more often than
permitted in the message definition. The Failed-AVP AVP MUST be
included and contain a copy of the first instance of the offending
AVP that exceeded the maximum number of occurrences.
PANA_UNSUPPORTED_VERSION 5011
Error code from PAA to PaC or from PaC to PAA. This error is
returned when a message was received, whose version number is
unsupported.
PANA_INVALID_AVP_LENGTH 5014
Error code from PAA to PaC or from PaC to PAA. The message
contained an AVP with an invalid length. The PANA-Error message
indicating this error MUST include the offending AVPs within a
Failed-AVP AVP.
PANA_INVALID_MESSAGE_LENGTH 5015
Error code from PAA to PaC or from PaC to PAA. This error is
returned when a message is received with an invalid message
length.
9.4.8 EAP-Payload AVP 9.4.8 EAP-Payload AVP
The EAP-Payload AVP is defined in [DIAMETER-EAP]. The EAP-Payload AVP (AVP Code 1031) is of type OctetString and is
used to encapsulate the actual EAP packet that is being exchanged
between the EAP peer and the EAP authenticator.
9.4.9 Session-Lifetime AVP
The Session-Lifetime AVP (Code 1032) data is of type Unsigned32. It
contains the number of seconds remaining before the current session
is considered expired.
9.4.10 Failed-AVP AVP
The Failed-AVP AVP (AVP Code 1033) is of type Grouped and provides
debugging information in cases where a request is rejected or not
fully processed due to erroneous information in a specific AVP. The
format of the Failed-AVP AVP is defined in [RFC3588].
9.4.11 NAP-Information AVP
The NAP-Information AVP (AVP Code: 1034) is of type Grouped, and
contains zero or one Provider-Identifier AVP which carries the
identifier of the NAP and one Provider-Name AVP which carries the
name of the NAP. Its Data field has the following ABNF grammar:
NAP-Information ::= < AVP Header: 1034 >
0*1 { Provider-Identifier }
{ Provider-Name }
* [ AVP ]
9.4.12 ISP-Information AVP
The ISP-Information AVP (AVP Code: 1035) is of type Grouped, and
contains zero or one Provider-Identifier AVP which carries the
identifier of the ISP and one Provider-Name AVP which carries the
name of the ISP. Its Data field has the following ABNF grammar:
ISP-Information ::= < AVP Header: 1035 >
0*1 { Provider-Identifier }
{ Provider-Name }
* [ AVP ]
9.4.13 Provider-Identifier AVP
The Provider-Identifier AVP (AVP Code: 1036) is of type Unsigned32,
and contains an IANA assigned "SMI Network Management Private
Enterprise Codes" [ianaweb] value, encoded in network byte order.
9.4.14 Provider-Name AVP
The Provider-Name AVP (AVP Code: 1037) is of type UTF8String, and
contains the UTF8-encoded name of the provider.
9.5 AVP Occurrence Table 9.5 AVP Occurrence Table
The following tables lists the AVPs used in this document, and The following tables lists the AVPs used in this document, and
specifies in which PANA messages they MAY, or MAY NOT be present. specifies in which PANA messages they MAY, or MAY NOT be present.
The table uses the following symbols: The table uses the following symbols:
0 The AVP MUST NOT be present in the message. 0 The AVP MUST NOT be present in the message.
0+ Zero or more instances of the AVP MAY be present in the
message.
0-1 Zero or one instance of the AVP MAY be present in the
message. It is considered an error if there are more than
one instance of the AVP.
1 One instance of the AVP MUST be present in the message.
1+ At least one instance of the AVP MUST be present in the
message.
+-----------------------------------------+ 0+ Zero or more instances of the AVP MAY be present in the
| Message | message.
| Type |
+-----+-----+-----+-----+-----+-----+-----+
Attribute Name | PSR | PSA | PAR | PAN | PBR | PBA | PDI |
--------------------+-----+-----+-----+-----+-----+-----+-----+
Result-Code | 0 | 0 | 0 | 0 | 1 | 0 | 0 |
Session-Id | 0 | 0 | 1 | 1 | 1 | 1 | 0 |
Termination-Cause | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
EAP-Payload | 0 | 0 | 1 | 1 | 1 | 0 | 0 |
MAC | 0 | 0 | 0-1 | 0-1 | 0-1 | 0-1 | 0 |
Device-Id | 0 | 0 | 0 | 0 | 1+ | 1+ | 0-1 |
Cookie | 0-1 | 0-1 | 0 | 0 | 0 | 0 | 0 |
Protection-Cap. | 0 | 0 | 0 | 0 | 0-1 | 0 | 0 |
--------------------+-----+-----+-----+-----+-----+-----+-----+
+-------------------------+ 0-1 Zero or one instance of the AVP MAY be present in the message.
| Message | It is considered an error if there are more than one instance
| Type | of the AVP.
+------+------+-----+-----+
Attribute Name | PRAR | PRAA | PTR | PTA |
--------------------+------+------+-----+-----+
Result-Code | 0 | 0 | 0 | 0 |
Session-Id | 1 | 1 | 1 | 1 |
Termination-Cause | 0 | 0 | 1 | 0 |
EAP-Payload | 0-1 | 0-1 | 0 | 0 |
MAC | 0-1 | 0-1 | 0-1 | 0-1 |
Device-Id | 1+ | 1+ | 0 | 0 |
Cookie | 0 | 0 | 0 | 0 |
Protection-Cap. | 0 | 0 | 0 | 0 |
--------------------+------+------+-----+-----+
Figure 10: AVP Occurrence Table 1 One instance of the AVP MUST be present in the message.
10 Security Considerations 1+ At least one instance of the AVP MUST be present in the
The PANA protocol provides ordered delivery for EAP messages. If an message.
+-----------------------------------------+
| Message |
| Type |
+-----+-----+-----+-----+-----+-----+-----+
Attribute Name | PSR | PSA | PAR | PAN | PBR | PBA | PDI |
--------------------+-----+-----+-----+-----+-----+-----+-----+
Result-Code | 0 | 0 | 0 | 0 | 1 | 0 | 0 |
Session-Id | 0 | 0 | 1 | 1 | 1 | 1 | 0 |
Termination-Cause | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
EAP-Payload | 0 | 0 | 1 | 1 | 1 | 0 | 0 |
MAC | 0 | 0 | 0-1 | 0-1 | 0-1 | 0-1 | 0 |
Device-Id | 0 | 0 | 0 | 0 | 1+ | 1+ | 0-1 |
Cookie | 0-1 | 0-1 | 0 | 0 | 0 | 0 | 0 |
Protection-Cap. | 0 | 0 | 0 | 0 | 0-1 | 0 | 0 |
Session-Lifetime | 0 | 0 | 0 | 0 | 0-1 | 0 | 0 |
Failed-AVP | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
ISP-Information | 0+ | 0-1 | 0-1 | 0 | 0 | 0 | 0 |
NAP-Information | 0-1 | 0 | 0-1 | 0 | 0 | 0 | 0 |
--------------------+-----+-----+-----+-----+-----+-----+-----+
+-------------------------------+
| Message |
| Type |
+------+------+-----+-----+-----+
Attribute Name | PRAR | PRAA | PTR | PTA | PER |
--------------------+------+------+-----+-----+-----+
Result-Code | 0 | 0 | 0 | 0 | 1 |
Session-Id | 1 | 1 | 1 | 1 | 1 |
Termination-Cause | 0 | 0 | 1 | 0 | 0 |
EAP-Payload | 0-1 | 0-1 | 0 | 0 | 0 |
MAC | 0-1 | 0-1 | 0-1 | 0-1 | 0-1 |
Device-Id | 1+ | 1+ | 0 | 0 | 0 |
Cookie | 0 | 0 | 0 | 0 | 0 |
Protection-Cap. | 0 | 0 | 0 | 0 | 0 |
Session-Lifetime | 0 | 0 | 0 | 0 | 0 |
Failed-AVP | 0 | 0 | 0 | 0 | 1 |
ISP-Information | 0 | 0 | 0 | 0 | 0 |
NAP-Information | 0 | 0 | 0 | 0 | 0 |
--------------------+------+------+-----+-----+-----+
Figure 10: AVP Occurrence Table
10. PANA Protocol Message Retransmissions
The PANA protocol provides retransmissions for all the message
exchanges except PANA-Auth-Request/Answer. PANA-Auth-Request messages
carry EAP requests which are retransmitted by the EAP protocol
entities when needed. The messages that need PANA-level
retransmissions are listed below:
PANA-PAA-Discover (PDI)
PANA-Start-Answer (PSA)
PANA-Bind-Request (PBR)
PANA-Reauth-Request (PRAR)
PANA-Termination-Request (PTR)
The PDI and PSA messages are always sent by the PaC. PBR is sent by
PAA. The last two messages, PRAR and PTR are sent either by PaC or
PAA.
The rule is that the sender of the request message retransmits the
request if the corresponding answer is not received in time. Answer
messages are sent as answers to the request messages, not based on a
timer. Exception to this rule is the PSA message. Because of the
stateless nature of the PAA in the beginning PaC provides
retransmission also for the PSA message. PANA-Error messages MUST
not be retransmitted. See Section 4.1.8 for more details of PANA
error handling.
PANA retransmission timers are based on the model used in DHCPv6
[RFC3315]. Variables used here are also borrowed from this
specification. PANA is a request response like protocol. The
message exchange terminates when either the request sender
successfully receives the appropriate answer, or when the message
exchange is considered to have failed according to the retransmission
mechanism described below.
The retransmission behavior is controlled and described by the
following variables:
RT Retransmission timeout
IRT Initial retransmission time
MRC Maximum retransmission count
MRT Maximum retransmission time
MRD Maximum retransmission duration
RAND Randomization factor
With each message transmission or retransmission, the sender sets RT
according to the rules given below. If RT expires before the message
exchange terminates, the sender recomputes RT and retransmits the
message.
Each of the computations of a new RT include a randomization factor
(RAND), which is a random number chosen with a uniform distribution
between -0.1 and +0.1. The randomization factor is included to
minimize synchronization of messages.
The algorithm for choosing a random number does not need to be
cryptographically sound. The algorithm SHOULD produce a different
sequence of random numbers from each invocation.
RT for the first message transmission is based on IRT:
RT = IRT + RAND*IRT
RT for each subsequent message transmission is based on the previous
value of RT:
RT = 2*RTprev + RAND*RTprev
MRT specifies an upper bound on the value of RT (disregarding the
randomization added by the use of RAND). If MRT has a value of 0,
there is no upper limit on the value of RT. Otherwise:
if (RT > MRT)
RT = MRT + RAND*MRT
MRC specifies an upper bound on the number of times a sender may
retransmit a message. Unless MRC is zero, the message exchange fails
once the sender has transmitted the message MRC times.
MRD specifies an upper bound on the length of time a sender may
retransmit a message. Unless MRD is zero, the message exchange fails
once MRD seconds have elapsed since the client first transmitted the
message.
If both MRC and MRD are non-zero, the message exchange fails whenever
either of the conditions specified in the previous two paragraphs are
met.
If both MRC and MRD are zero, the client continues to transmit the
message until it receives a response.
10.1 Transmission and Retransmission Parameters
This section presents a table of values used to describe the message
retransmission behavior of request and PANA-Start-Answer messages
marked with REQ_*. PANA-PAA-Discover message retransmission values
are marked with PDI_*. The table shows default values.
Parameter Default Description
------------------------------------------------
PDI_IRT 1 sec Initial PDI timeout.
PDI_MRT 120 secs Max PDI timeout value.
PDI_MRC 0 Configurable.
PDI_MRD 0 Configurable.
REQ_IRT 1 sec Initial Request timeout.
REQ_MRT 30 secs Max Request timeout value.
REQ_MRC 10 Max Request retry attempts.
REQ_MRD 0 Configurable.
So for example the first RT for the PBR message is calculated using
REQ_IRT as the IRT:
RT = REQ_IRT + RAND*REQ_IRT
11. Security Considerations
The PANA protocol provides ordered delivery for EAP messages. If an
EAP method that provides session keys is used, a PANA SA is created. EAP method that provides session keys is used, a PANA SA is created.
The EAP Success/Failure message is one of the signaling messages The EAP Success/Failure message is one of the signaling messages
which is integrity protected with this PANA SA. The PANA protocol which is integrity protected with this PANA SA. The PANA protocol
does not provide security protection for the initial EAP message does not provide security protection for the initial EAP message
exchange. Integrity protection can only be provided after the PANA exchange. Integrity protection can only be provided after the PANA SA
SA has been established. Thus, PANA re-authentication, revocation has been established. Thus, PANA re-authentication, revocation and
and disconnect notifications can be authenticated, integrity and disconnect notifications can be authenticated, integrity and replay
replay protected. In certain environments (e.g. on a shared link) protected. In certain environments (e.g. on a shared link) the EAP
the EAP method selection is an important issue. method selection is an important issue.
The PANA framework described in this document covers the discussion The PANA framework described in this document covers the discussion
of different protocols which are of interest for a protocol between of different protocols which are of interest for a protocol between
the PaC and the PAA (typically referred as the PANA protocol). the PaC and the PAA (typically referred as the PANA protocol).
The PANA itself consists of a sequence of steps which are executed The PANA itself consists of a sequence of steps which are executed to
to complete the network access authentication procedure. Some of complete the network access authentication procedure. Some of these
these steps are optional. steps are optional.
The following execution steps have been identified as being relevant The following execution steps have been identified as being relevant
for PANA. They security considerations will be discussed in detail for PANA. They security considerations will be discussed in detail
subsequently. subsequently.
a) Discovery message exchange a) Discovery message exchange
In general it is difficult to prevent a vulnerabilities of the In general it is difficult to prevent a vulnerabilities of the
discovery protocol since the initial discovery are unsecured. To discovery protocol since the initial discovery are unsecured. To
prevent very basic attacks an adversary should not be able to cause prevent very basic attacks an adversary should not be able to cause
state creation with discovery messages at the PAA. This is prevented state creation with discovery messages at the PAA. This is prevented
by re-using a cookie concept (see [RFC2522]) which allows the by re-using a cookie concept (see [RFC2522] which allows the
responder to be stateless in the first message exchange. Because of responder to be stateless in the first message exchange. Because of
the architectural assumptions made in PANA (i.e. the PAA is the on the architectural assumptions made in PANA (i.e. the PAA is the on
the same link as the PaC) the return-routability concept does not the same link as the PaC) the return-routability concept does not
provide additional protection. Hence it is difficult to prevent this provide additional protection. Hence it is difficult to prevent this
threat entirely. Furthermore it is not possible to shift heavy threat entirely. Furthermore it is not possible to shift heavy
cryptographic operations to the PaC at the first few messages since cryptographic operations to the PaC at the first few messages since
the computational effort depends on the EAP method. The usage of the computational effort depends on the EAP method. The usage of
client-puzzles as introduced by [JB99] is under investigation. client-puzzles as introduced by [jb99] is under investigation.
Resistance against blind DoS attacks (i.e. attacks by off-path Resistance against blind DoS attacks (i.e. attacks by off-path
adversaries) is achieved with sequence numbers and cookies. adversaries) is achieved with sequence numbers and cookies.
Since PAA and PaC are one IP hop away from each other, PANA messages Since PAA and PaC are supposed to be one IP hop away, a simple TTL
can be filtered whenever messages arrive at interfaces where they check can prevent off-link attacks. Furthermore, additional filtering
are not expected. can be enabled on the EPs. An EP may be able to filter unauthorized
PAA advertisements when they are received on the access side of the
network where only PaCs are connected.
b) EAP over PANA message exchange b) EAP over PANA message exchange
The EAP derived session key is used to create a PANA security The EAP derived session key is used to create a PANA security
association. Since the execution of an EAP method might require a association. Since the execution of an EAP method might require a
large number of roundtrips and no other session key is available it large number of roundtrips and no other session key is available it
is not possible to secure the EAP message exchange itself. Hence an is not possible to secure the EAP message exchange itself. Hence an
adversary can both eavesdrop the EAP messages and is also able to adversary can both eavesdrop the EAP messages and is also able to
inject arbitrary messages which might confuse both the PaC and the inject arbitrary messages which might confuse both the EAP peer on
PAA. The threats caused by this ability heavily depend on the EAP PaC and the EAP authenticator or authentication server on the PAA.
state machine. Since especially the PAA is not allowed to discard The threats caused by this ability heavily depend on the EAP state
packets and packets have to be stored or forwarded to an AAA machine. Since especially the PAA is not allowed to discard packets
infrastructure some risk of DoS attacks exists. and packets have to be stored or forwarded to an AAA infrastructure
some risk of DoS attacks exists.
Eavesdropping EAP packets might cause problems when (a) the EAP Eavesdropping EAP packets might cause problems when (a) the EAP
method is weak and enables dictionary or replay attacks or even method is weak and enables dictionary or replay attacks or even
allows an adversary to learn the long-term password directly. allows an adversary to learn the long-term password directly.
Furthermore, if the optional EAP Identity payload is used then it Furthermore, if the optional EAP Identity payload is used then it
allows the adversary to learn the identity of the PaC. In such a allows the adversary to learn the identity of the PaC. In such a case
case a privacy problem is prevalent. a privacy problem is prevalent.
To prevent these threats Section 6 suggests using proper EAP methods To prevent these threats Section 6 suggests using proper EAP methods
for particular environments. Depending on the usage environment an for particular environments. Depending on the usage environment an
EAP authentication has to be used for example which supports user EAP authentication has to be used for example which supports user
identity confidentiality, protection against dictionary attacks and identity confidentiality, protection against dictionary attacks and
session key establishment. It is therefore the responsibility of the session key establishment. It is therefore the responsibility of the
network operators and end users to choose the proper EAP method. network operators and end users to choose the proper EAP method.
PANA does not protect the EAP method exchange, but provides ordered PANA does not protect the EAP method exchange, but provides ordered
delivery with sequence numbers. Sequence numbers and cookies delivery with sequence numbers. Sequence numbers and cookies provide
provide resistance against blind DoS attacks. resistance against blind DoS attacks.
c) PANA SA establishment c) PANA SA establishment
Once the EAP message authentication is finished a fresh and unique Once the EAP message authentication is finished a fresh and unique
session key is available to the PaC and the PAA. This assumes that session key is available to the PaC and the PAA. This assumes that
the EAP method allows session key derivation and that the generated the EAP method allows session key derivation and that the generated
session key has a good quality. For further discussion about the session key has a good quality. For further discussion about the
importance of the session key generation refer to the next importance of the session key generation refer to the next subsection
subsection (c) about compound authentication. The session key (d) about compound authentication. The session key available for the
available for the PaC is established as part of the authentication PaC is established as part of the authentication and key exchange
and key exchange procedure of the selected EAP method. The PAA procedure of the selected EAP method. The PAA obtains the session key
obtains the session key via the AAA infrastructure (if used). Draft via the AAA infrastructure (if used). Draft
[CFB02] describes how a session key is securely carried (i.e. CMS [I-D.ietf-aaa-diameter-cms-sec] describes how a session key is
protected) between AAA servers. Security issues raised with this securely carried (i.e. CMS protected) between AAA servers. Security
session key transport are described in [WHC02]. issues raised with this session key transport are described in
[I-D.walker-aaa-key-distribution].
The establishment of a PANA SA is required in environments where no The establishment of a PANA SA is required in environments where no
physical or link layer security is available. The PANA SA allows physical or link layer security is available. The PANA SA allows
subsequently exchanged messages to experience cryptographic subsequently exchanged messages to experience cryptographic
protection. For the current version of the document an Integrity protection. For the current version of the document an integrity
object is defined which is based on Diameter objects. The Integrity object (MAC AVP) is defined which supports data-origin
Object supports data-origin authentication, replay protection based authentication, replay protection based on sequence numbers and
on sequence numbers and integrity protection based on a keyed integrity protection based on a keyed message digest. Confidentiality
message digest. Confidentiality protection is not provided. The protection is not provided. The session keys used for this object
session keys (one for each direction) used for this object has to be have to be provided by the EAP method. For this version of the
provided by the EAP method. For this version of the document it is document it is assumed that no negotiation of algorithms and
assumed that no negotiation of algorithms and parameters takes parameters takes place. Instead HMAC-SHA1 is used by default. A
place. Instead HMAC-SHA1 is used per-default. A different algorithm different algorithm such as HMAC-MD5 might be used as an option. The
such as HMAC-MD5 might be used as an option. The used algorithm is used algorithm is indicated in the header of the Integrity object. To
indicated in the header of the Integrity object. To select the select the security association for signaling message protection the
security association for signaling message protection the Session Session ID is conveyed. The keyed message digest included in the
ID. The keyed message digest included in the Integrity object will Integrity object will include all fields of the PANA signaling
include all fields of the PANA signaling message including the message including the sequence number field of the packet.
sequence number field of the packet.
The protection of subsequent signaling messages prevents an The protection of subsequent signaling messages prevents an adversary
adversary from acting as a man-in-the-middle adversary, from from acting as a man-in-the-middle adversary, from injecting packets,
injecting packets, from replaying messages and from modifying the from replaying messages and from modifying the content of the
content of the exchanged packets. This prevents subsequently exchanged packets. This prevents subsequently described threats.
described threats.
If an entity (PAA or PaC) looses its state (especially the current If an entity (PAA or PaC) loses its state (especially the current
sequence number) then the entire PANA protocol has to be restarted. sequence number) then the entire PANA protocol has to be restarted.
No re-synchronization procedure is provided. No re-synchronization procedure is provided.
The lifetime of the PANA SA has to be bound to the refresh interval The lifetime of the PANA SA has to be bound to the AAA-authorized
with an additional tolerance period. To provide fast re- session lifetime with an additional tolerance period. Unless PANA
authentication a separate security association (e.g. one stored at state is updated by executing another EAP authentication, PANA SA is
the local AAA server) should be used. By fast re-authentication we removed when the current session expires. The lifetime of the PANA SA
mean a new PANA protocol execution which does not involve the entire has to be bound to the AAA-authorized session lifetime with an
AAA communication. The ability to trigger such a protocol execution additional tolerance period. Unless PANA state is updated by
depends on the given EAP method and on the policy of the local executing another EAP authentication, PANA SA is removed when the
network requesting authentication. current session expires.
d) Enabling weak legacy authentication methods in insecure networks d) Enabling weak legacy authentication methods in insecure networks
Some of the authentication methods are not strong enough to be used Some of the authentication methods are not strong enough to be used
in insecure networks where attackers can easily eavesdrop and spoof in insecure networks where attackers can easily eavesdrop and spoof
on the link. They may not be able to produce much needed keying on the link. They may not be able to produce much needed keying
material either. An example would be using EAP-MD5 over wireless material either. An example would be using EAP-MD5 over wireless
links. Use of such legacy methods can be enabled by carrying them links. Use of such legacy methods can be enabled by carrying them
over a secure channel. There are EAP methods which are specifically over a secure channel. There are EAP methods which are specifically
designed for this purpose, such as EAP-TTLS [TTLS],PEAP [PEAP] or designed for this purpose, such as EAP-TTLS
EAP-IKEv2 [EAP-IKEv2]. PANA can carry these EAP tunneling methods [I-D.ietf-pppext-eap-ttls],PEAP [I-D.josefsson-pppext-eap-tls-eap] or
which can carry the legacy methods. PANA does not do anything EAP-IKEv2 [I-D.tschofenig-eap-ikev2]. PANA can carry these EAP
special for this case. The EAP tunneling method will have to produce tunneling methods which can carry the legacy methods. PANA does not
keying material for PANA SA when needed. There are certain MitM do anything special for this case. The EAP tunneling method will have
vulnerabilities with tunneling EAP methods [MITM]. Solving these to produce keying material for PANA SA when needed. There are certain
MitM vulnerabilities with tunneling EAP methods [mitm]. Solving these
problems is outside the scope of PANA. The compound authentication problems is outside the scope of PANA. The compound authentication
problem described in [PL+03] is likely to be solved in EAP itself problem described in [I-D.puthenkulam-eap-binding] is likely to be
rather than in PANA. solved in EAP itself rather than in PANA.
e) Preventing downgrading attacks e) Preventing downgrading attacks
EAP supports a number of different EAP methods for authentication EAP supports a number of different EAP methods for authentication and
and therefore it might be required to agree on a specific mechanism. therefore it might be required to agree on a specific mechanism. An
An unprotected negotiation mechanism is supported in EAP and a unprotected negotiation mechanism is supported in EAP and a secure
secure negotiation procedure for the GSS-API methods. The support of negotiation procedure for the GSS-API methods. The support of the
the GSS-API as an EAP method is described in [AS02]. A protected GSS-API as an EAP method is described in [I-D.aboba-pppext-eapgss]. A
negotiation is supported by the GSS-API with RFC 2478 [RFC2478]. If protected negotiation is supported by the GSS-API with RFC 2478
desired, such a protection can also be offered by PANA by repeating [RFC2478]. If desired, such a protection can also be offered by PANA
the list of supported EAP methods protected with the PANA SA. This by repeating the list of supported EAP methods protected with the
type of protection is similar to the protected negotiation described PANA SA. This type of protection is similar to the protected
in [RFC3329]. negotiation described in [RFC3329].
This issue requires further investigation especially since the EAP This issue requires further investigation especially since the EAP
protocol is executed between different endpoints than the PANA protocol is executed between different endpoints than the PANA
protocol. protocol.
f) Device Identifier exchange f) Device Identifier exchange
As part of the authorization procedure a Device Identifier has to be As part of the authorization procedure a Device Identifier has to be
installed at the EP by the PAA. The PaC provides the Device installed at the EP by the PAA. The PaC provides the Device
Identifier information to the PAA secured with the PANA SA. Section Identifier information to the PAA secured with the PANA SA. Section
6.2.4 of [THREATS] describes a threat where an adversary modifies 6.2.4 of [I-D.ietf-pana-threats-eval] describes a threat where an
the Device Identifier to gain unauthorized access to the network. adversary modifies the Device Identifier to gain unauthorized access
to the network.
The installation of the Device Identifier at the EP (independently The installation of the Device Identifier at the EP (independently
whether the EP is co-located with the PAA or not) has to be whether the EP is co-located with the PAA or not) has to be
accomplished in a secure manner. These threats are, however, not accomplished in a secure manner. These threats are, however, not part
part of the PANA protocol itself since the protocol is not PANA of the PANA protocol itself since the protocol is not PANA specific.
specific.
g) Triggering a data protection protocol g) Triggering a data protection protocol
Recent activities in the EAP working group try to create a common Recent activities in the EAP working group try to create a common
framework for key derivation which is described in [Ab02]. This framework for key derivation which is described in
framework is also relevant for PANA in various ways. First, a PANA [I-D.aboba-pppext-key-problem]. This framework is also relevant for
security association needs to be created. Additionally it might be PANA in various ways. First, a PANA security association needs to be
necessary to trigger a protocol which allows link layer and network created. Additionally it might be necessary to trigger a protocol
layer data protection to be established. As an example see Section 1 which allows link layer and network layer data protection to be
of [Ab02] with [802.11i] and [802.11] as an example. Furthermore, a established. As an example see Section 1 of
derived session key might help to create the pre-requisites for [I-D.aboba-pppext-key-problem] with [802.11i] and [802.11] as an
network layer protection (for example IPsec). example. Furthermore, a derived session key might help to create the
pre-requisites for network-layer protection (for example IPsec
[I-D.ietf-pana-ipsec]).
As motivated in Section 6.4 of [THREATS] it might be necessary to As motivated in Section 6.4 of [I-D.ietf-pana-threats-eval] it might
establish either a link layer or a network layer protection to be necessary to establish either a link layer or a network layer
prevent certain thefts in certain scenarios. protection to prevent certain thefts in certain scenarios.
Threats specific to the establishment of a link layer or a network Threats specific to the establishment of a link layer or a network
layer security association are outside the scope of PANA. The layer security association are outside the scope of PANA. The
interested reader should refer to the relevant working groups such interested reader should refer to the relevant working groups such as
as IPsec or Midcom. IPsec or Midcom.
h) Periodic refresh messages h) Liveness test
Network access authentication is done for a very specific purpose Network access authentication is done for a very specific purpose and
and often charging procedures are involved which allow restricting often charging procedures are involved which allow restricting
network resource usage based on some policies. In mobility network resource usage based on some policies. In mobility
environments it is always possible that an end host suddenly environments it is always possible that an end host suddenly
disconnects without transmitting a disconnect message. If network disconnects without transmitting a disconnect message. Operators are
access authentication as part of PANA is executed only at the generally motivated to detect a disconnected end host as soon as
beginning then an adversary can gain advantage of the installed possible in order to release resources (i.e., garbage collection).
packet filters to submit and receive data packets. The PAA can remove per-session state information including installed
security association, packet filters, etc.
Also for the network operator it might be desirable to enforce a
disconnect based on some external events (e.g. because of
insufficient funds, etc.).
An additional motivation for detecting a disconnected end host is
the ability to release resources (i.e. garbage collection). The PAA
can remove per-session state information including installed
security association, packet filters etc.
Different procedures can be used for disconnect indication. PANA Different procedures can be used for disconnect indication. PANA
cannot assume link layer disconnect indication. Hence this cannot assume link-layer disconnect indication. Hence this
functionality has to be provided at a higher layer. With this functionality has to be provided at a higher layer. With this version
version of the draft we suggest to apply the soft-state principle of the draft we suggest to apply the soft-state principle found at
found at other protocols (such as RSVP). Soft-state means that other protocols (such as RSVP). Soft-state means that session state
session state is kept alive as long as refresh messages refresh the is kept alive as long as refresh messages refresh the state. If no
state. If no new refresh messages are provided then the state new refresh messages are provided then the state automatically times
automatically times out and resources are released. This process out and resources are released. This process includes stopping
includes stopping accounting procedures. accounting procedures.
Based on the different environments where PANA could be used it is
difficult to fix a refresh interval. Hence a default refresh
interval of 30 seconds is suggested. Additionally there is the
possibility to negotiation this interval once the PANA security
association is established. A policy at the PAA and the PaC would
ensure that the refresh interval is selected with a value which is
either too high or too low. There is certainly a tradeoff between
the refresh interval and the bandwidth consumption. To reduce the
bandwidth consumption a small PANA message consisting only of a
session identifier and the Integrity object is used. The session
identifier refers to the state that has to be refreshed. Some
environments do not need PANA refresh messages to detect orphan
states. For these environments the refresh interval should be set to
zero which effectively disables the usage of refresh messages. In
case of IPsec protection a dead-peer mechanism can be used to detect
inactivity (see [HBR03]).
Refresh messages are sent from the PaC to the PAA.
From a security point of view an adversary must not be able to A PANA session is associated with a session lifetime. The session is
inject, modify or replay refresh messages nor must he be able to terminated unless it is refreshed by a new round of EAP
change the refresh interval (e.g. setting it to zero) without authentication before it expires. Therefore, at the latest a
detection. Hence these messages experience cryptographic protection. disconnected client can be detected when its lifetime expires. A
disconnect may also be detected earlier by using PANA
reauthentication messages. A request message can be generated by
either PaC or PAA at any time and the peer must respond with an
answer message. A successful round-trip of this exchange is a simple
verification that the peer is alive. This test can be engaged when
there is a possibility that the peer might have disconnected (e.g.,
after discontinuation of data traffic). Periodic use of this exchange
as a keep-alive requires additional care as it might result in
congestion and hence false alarms. This exchange is cryptographically
protected when PANA SA is available in order to prevent threats
associated with the abuse of this functionality.
i) Tear-Down message i) Tear-Down message
The PANA protocol supports the ability for both the PaC and the PAA The PANA protocol supports the ability for both the PaC and the PAA
to transmit a tear-down message. This message causes state removal, to transmit a tear-down message. This message causes state removal, a
a stop of the accounting procedure and removes the installed packet stop of the accounting procedure and removes the installed packet
filters. filters.
It is obvious that such a message must be protected to prevent an It is obvious that such a message must be protected to prevent an
adversary from deleting state information and thereby causing denial adversary from deleting state information and thereby causing denial
of service attacks. of service attacks.
11 Open Issues 12. Open Issues
A list of open issues is maintained at A list of open issues is maintained at [1].
http://danforsberg.info:8080/pana-issues/.
12 Acknowledgments The remaining issues for -01 version of draft are: None.
The remaining issues for -xx version of draft are: 2, 12, 16, 28, 29,
34, 35, 36 and 37.
13. Change History
Issues incorporated in PANA-01 June 2003: 1, 3, 10, 5, 6, 7 and 11.
Issues incorporated in PANA-02 October 2003: 8, 17, 18, 19, 20, 21,
22, 23, 24, 25, 26, 30, 31, 32 and 33.
14. Acknowledgments
We would like to thank all members of the PANA working group for We would like to thank all members of the PANA working group for
their comments to this document. their comments to this document.
13 References Normative References
[802.11] I. S. 802.11-1997, "Information technology - [I-D.ietf-pana-usage-scenarios]
telecommunications and information exchange between systems - local Ohba, Y., "Problem Statement and Usage Scenarios for
and metropolitan area networks - specific requirements part 11: PANA", draft-ietf-pana-usage-scenarios-06 (work in
Wireless lan medium access control (mac) and physical layer (phy) progress), April 2003.
specifications," tech. rep., 1997.
[RFC2522] P. Karn and W. Simpson, "Photuris: Session-key management [RFC2284] Blunk, L. and J. Vollbrecht, "PPP Extensible
protocol," RFC 2522, March 1999. Authentication Protocol (EAP)", RFC 2284, March 1998.
[Ab02] B. Aboba and D. Simon: "EAP Keying Framework", Internet [I-D.ietf-pana-threats-eval]
Draft, Internet Engineering Task Force, March, 2003, Work in Parthasarathy, M., "PANA Threat Analysis and security
progress. requirements", draft-ietf-pana-threats-eval-04 (work in
progress), May 2003.
[802.11i] I. D. 802.11i/D2, "Draft supplement to standard for [I-D.ietf-pana-requirements]
telecommunications and information exchange between systems - Yegin, A. and Y. Ohba, "Protocol for Carrying
lan/man specific requirements - part 11: Wireless medium access Authentication for Network Access (PANA)Requirements",
control (mac) and physical layer (phy) specifications: Specification draft-ietf-pana-requirements-07 (work in progress), June
for enhanced security," tech. rep., 2001. 2003.
[AS02] Aboba, B., Simon, D.: "EAP GSS Authentication Protocol", [RFC1982] Elz, R. and R. Bush, "Serial Number Arithmetic", RFC 1982,
Internet Draft, Internet Engineering Task Force, April, 2002, Work August 1996.
in progress.
[CFB02] P. Calhoun, S. Farrell, and W. Bulley: "Diameter CMS [RFC2988] Paxson, V. and M. Allman, "Computing TCP's Retransmission
Security Application," Internet Draft, Internet Engineering Task Timer", RFC 2988, November 2000.
Force, Mar. 2002, Work in progress.
[RFC2284] Blunk, L. and J. Vollbrecht, "PPP Extensible [I-D.ietf-eap-rfc2284bis]
Authentication Protocol (EAP)", RFC 2284, March 1998. Blunk, L., "Extensible Authentication Protocol (EAP)",
draft-ietf-eap-rfc2284bis-06 (work in progress), September
2003.
[HBR03] G. Huang, S. Beaulieu, and D. Rochefort, "A traffic-based [I-D.ietf-pana-ipsec]
method of detecting dead ike peers", Internet Draft, Internet Parthasarathy, M., "PANA enabling IPsec based Access
Engineering Task Force, 2003, Work in progress. Control", draft-ietf-pana-ipsec-00 (work in progress),
October 2003.
[RFC2409] Harkins, D. and D. Carrel, "The Internet Key Exchange [I-D.tschofenig-pana-bootstrap-rfc3118]
(IKE)", RFC 2409, November 1998. Tschofenig, H., "Bootstrapping RFC3118 Delayed
authentication using PANA",
draft-tschofenig-pana-bootstrap-rfc3118-00 (work in
progress), June 2003.
[MITM] N. Asokan, V. Niemi, and K. Nyberg: "Man-in-the-middle in [I-D.ietf-seamoby-ctp]
tunnelled authentication", In the Proceedings of the 11th Loughney, J., "Context Transfer Protocol",
International Workshop on Security Protocols, Cambridge, UK, April draft-ietf-seamoby-ctp-04 (work in progress), October
2003. To be published in the Springer-Verlag LNCS series. 2003.
[PEAP] A. Palekar, D. Simon, G. Zorn and S. Josefsson: "Protected [RFC2716] Aboba, B. and D. Simon, "PPP EAP TLS Authentication
EAP Protocol (PEAP)", Internet Draft, Internet Engineering Task Protocol", RFC 2716, October 1999.
Force, March 2003, Work in progress.
[PL+03] J. Puthenkulam, V. Lortz, A. Palekar, D. Simon, and B. [I-D.josefsson-pppext-eap-tls-eap]
Aboba, "The compound authentication binding problem," internet Josefsson, S., Palekar, A., Simon, D. and G. Zorn,
draft, Internet Engineering Task Force, 2003. Work in progress. "Protected EAP Protocol (PEAP)",
draft-josefsson-pppext-eap-tls-eap-06 (work in progress),
March 2003.
[PY+02] R. Penno, A. Yegin, Y. Ohba, G. Tsirtsis, and C. Wang: [I-D.ietf-pppext-eap-ttls]
"Protocol for Carrying Authentication for Network Access (PANA) Funk, P. and S. Blake-Wilson, "EAP Tunneled TLS
Requirements and Terminology", Internet Draft, Internet Engineering Authentication Protocol (EAP-TTLS)",
Task Force, June 2003, Work in progress. draft-ietf-pppext-eap-ttls-03 (work in progress), August
2003.
[RFC2284bis] L. Blunk, J. Vollbrecht, B. Aboba, J. Carlson: [I-D.tschofenig-eap-ikev2]
"Extensible Authentication Protocol (EAP)", Internet Draft, Internet Tschofenig, H. and D. Kroeselberg, "EAP IKEv2 Method
Engineering Task Force, January 2003, Work in progress. (EAP-IKEv2)", draft-tschofenig-eap-ikev2-01 (work in
progress), July 2003.
[RFC1982] Elz, R., Bush, R.: "Serial Number Arithmetic", RFC 1982, [RFC2409] Harkins, D. and D. Carrel, "The Internet Key Exchange
August 1996. (IKE)", RFC 2409, November 1998.
[RFC2478] E. Baize and D. Pinkas, "The simple and protected GSS-API [RFC2234] Crocker, D. and P. Overell, "Augmented BNF for Syntax
negotiation mechanism," RFC 2478, Internet Engineering Task Force, Specifications: ABNF", RFC 2234, November 1997.
Dec. 1998.
[RFC2988] V. Paxson, and M. Allman: "Computing TCP's Retransmission [RFC3588] Calhoun, P., Loughney, J., Guttman, E., Zorn, G. and J.
Timer", RFC 2988, November, 2000. Arkko, "Diameter Base Protocol", RFC 3588, September 2003.
[RFC3329] J. Arkko, V. Torvinen, G. Camarillo, A. Niemi, and T. [RFC2464] Crawford, M., "Transmission of IPv6 Packets over Ethernet
Haukka: "Security Mechanism Agreement for the Session Initiation Networks", RFC 2464, December 1998.
Protocol (SIP)", RFC 3329, January, 2003.
[THREATS] M. Parthasarathy: "PANA Threat Analysis and security [I-D.ietf-aaa-eap]
requirements", Internet Draft, Internet Engineering Task Force, May Eronen, P., Hiller, T. and G. Zorn, "Diameter Extensible
2003, Work in progress. Authentication Protocol (EAP) Application",
draft-ietf-aaa-eap-02 (work in progress), July 2003.
[TTLS] P. Funk and S. Blake-Wilson: "EAP tunneled TLS authentication [RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C. and
protocol (EAP-TTLS)," Internet Draft, Internet Engineering Task M. Carney, "Dynamic Host Configuration Protocol for IPv6
Force, November 2002. Work in progress. (DHCPv6)", RFC 3315, July 2003.
[USAGE] Y. Ohba, S. Das, B. Patil, H. Soliman, A. Yegin, A.: [RFC2522] Karn, P. and W. Simpson, "Photuris: Session-Key Management
"Problem Statement and Usage Scenarios for PANA", Internet Draft, Protocol", RFC 2522, March 1999.
Internet Engineering Task Force, April 2003, Work in progress.
[EAP-IKEv2] H. Tschofenig and D. Kroeselberg: "EAP IKEv2 Method [I-D.ietf-aaa-diameter-cms-sec]
(EAP-IKEv2)", Internet Draft, Internet Engineering Task Force, June Calhoun, P., Farrell, S. and W. Bulley, "Diameter CMS
2003, Work in progress. Security Application", draft-ietf-aaa-diameter-cms-sec-04
(work in progress), March 2002.
[WHC02] J. Walker, R. Housley, and N. Cam-Winget: "AAA key [I-D.walker-aaa-key-distribution]
distribution," Internet Draft, Internet Engineering Task Force, Apr. Housley, R., Walker, J. and N. Cam-Winget, "AAA Key
2002, Expired. Distribution", draft-walker-aaa-key-distribution-00 (work
in progress), April 2002.
[DIAMETER-EAP] T. Hiller and G. Zorn: "Diameter Extensible [I-D.puthenkulam-eap-binding]
Authentication Protocol (EAP) Application", Internet Draft, Internet Puthenkulam, J., "The Compound Authentication Binding
Engineering Task Force, March 2003, Work in progress. Problem", draft-puthenkulam-eap-binding-03 (work in
progress), July 2003.
[DIAMETER] P. Calhoun, J. Loughney, E. Guttman, G. Zorn and J. [I-D.aboba-pppext-eapgss]
Arkko: "Diameter Base Protocol", Internet Draft, Internet Aboba, B. and D. Simon, "EAP GSS Authentication Protocol",
Engineering Task Force, December 2002, Work in progress. draft-aboba-pppext-eapgss-12 (work in progress), April
2002.
[IANAWEB] IANA, "Number assignment", http://www.iana.org [RFC2478] Baize, E. and D. Pinkas, "The Simple and Protected GSS-API
Negotiation Mechanism", RFC 2478, December 1998.
[CTP] J. Loughney, M. Nakhjiri, C. Perkins and R. Koodli: [RFC3329] Arkko, J., Torvinen, V., Camarillo, G., Niemi, A. and T.
"Context Transfer Protocol", Internet Draft, Internet Engineering Haukka, "Security Mechanism Agreement for the Session
Task Force, June 2003, Work in progress. Initiation Protocol (SIP)", RFC 3329, January 2003.
[JB99] A. Juels and J. Brainard: "Client Puzzles: A Cryptographic [I-D.aboba-pppext-key-problem]
Defense Against Connection Depletion Attacks", In S. Kent, editor, Aboba, B. and D. Simon, "EAP Key Management Framework",
Proceedings of NDSS '99 (Networks and Distributed Security draft-aboba-pppext-key-problem-07 (work in progress),
Systems), pages 151-165, 1999. August 2003.
Change History Informative References
Changes from PANA-00 to PANA-01 June 2003 [ianaweb] IANA, "Number assignment", http://www.iana.org.
- The names for the PANA messages have been changed. Hence it was [jb99] Juels, A. and J. Brainard, "Client Puzzles: A
necessary to reflect the new terminology in other parts of the Cryptographic Defense Against Connection Depletion
draft. Attacks", Proceedings of NDSS '99 (Networks and
Distributed Security Systems), pages 151-165, 1999.
- New text has been added to the following sections: [mitm] Asokan, N., Niemi, V. and K. Nyberg, "Man-in-the-middle in
tunnelled authentication", In the Proceedings of the 11th
International Workshop on Security Protocols, Cambridge,
UK, April 2003.
* Terminology [802.11i] Institute of Electrical and Electronics Engineers, "Draft
* PANA Security Association supplement to standard for telecommunications and
* Message Authentication Code information exchange between systems - lan/man specific
* Refresh Interval Negotiation requirements - part 11: Wireless medium access control
* Mobility Handling (mac) and physical layer (phy) specifications:
* Event Notification Specification for enhanced security", IEEE 802.11i/D6.0,
* Message Formats 2003.
- The details on message formats add more details to several parts [802.11] Institute of Electrical and Electronics Engineers,
of the draft. The AVP format is based on Diameter/ "Information technology - telecommunications and
information exchange between systems - local and
metropolitan area networks - specific requirements part
11: Wireless lan medium access control (mac) and physical
layer (phy) specifications", IEEE Standard 802.11, 1997.
- The open issue list has been replaced by a reference to the web URIs
page containing the open issues.
Author's Addresses [1] <http://danforsberg.info:8080/pana-issues/>
Basavaraj Patil Authors' Addresses
Nokia
6000 Connection Dr.
Irving, TX. 75039
USA
Phone: +1 972-894-6709
Email: Basavaraj.Patil@nokia.com
Dan Forsberg Dan Forsberg
Nokia Research Center Nokia Research Center
P.O. Box 407 P.O. Box 407
FIN-00045 NOKIA GROUP, Finland FIN-00045 NOKIA GROUP
Finland
Phone: +358 50 4839470 Phone: +358 50 4839470
EMail: dan.forsberg@nokia.com EMail: dan.forsberg@nokia.com
Alper E. Yegin
DoCoMo USA Labs
181 Metro Drive, Suite 300
San Jose, CA, 95110
USA
Phone: +1 408 451 4743
Email: alper@docomolabs-usa.com
Yoshihiro Ohba Yoshihiro Ohba
Toshiba America Research, Inc. Toshiba America Information Systems, Inc.
P.O. Box 136 9740 Irvine Blvd.
Convent Station, NJ, 07961-0136 Irvine, CA 92619-1697
USA USA
Phone: +1 973 829 5174 Phone: +1 973 829 5174
Email: yohba@tari.toshiba.com EMail: yohba@tari.toshiba.com
Basavaraj Patil
Nokia
6000 Connection Dr.
Irving, TX 75039
USA
Phone: +1 972-894-6709
EMail: Basavaraj.Patil@nokia.com
Hannes Tschofenig Hannes Tschofenig
Siemens Corporate Technology Siemens Corporate Technology
Otto-Hahn-Ring 6 Otto-Hahn-Ring 6
81739 Munich 81739 Munich
Germany Germany
Email: Hannes.Tschofenig@siemens.com
Appendix A. Adding sequence number to PANA for carrying EAP EMail: Hannes.Tschofenig@siemens.com
Alper E. Yegin
DoCoMo USA Labs
181 Metro Drive, Suite 300
San Jose, CA 95110
USA
A.1. Why is sequence number needed for PANA to carry EAP? Phone: +1 408 451 4743
EMail: alper@docomolabs-usa.com
EAP [RFC2284bis] requires underlying transports to provide Appendix A. Adding sequence number to PANA for carrying EAP
ordered-delivery of messages. If an underlying transport does not
satisfy the ordering requirement, the following situation could
happen:
EAP Peer EAP Authenticator Appendix A.1 Why is sequence number needed for PANA to carry EAP?
--------------------------------------------
1. (got req 1) <------- Request ID=1
2. Response ID=1 ---+
| (timeout)
3. | +-- Request ID=1
| |
+-|--> (got resp 1)
4. (got req 2) <----|-- Request ID=2
|
5. Response ID=2 -----|--> (got resp 2)
|
6. (got req 1) <----+
7. Response ID=1 --------> [discarded due to unexpected ID]
Figure A.1 Undesirable scenario EAP [I-D.ietf-eap-rfc2284bis] requires underlying transports to
provide ordered-delivery of messages. If an underlying transport
does not satisfy the ordering requirement, the following situation
could happen:
In Figure A.1, the second EAP Request message with Identifier=1 EAP Peer EAP Authenticator
--------------------------------------------
1. (got req 1) <------- Request ID=1
2. Response ID=1 ---+
| (timeout)
3. | +-- Request ID=1
| |
+-|--> (got resp 1)
4. (got req 2) <----|-- Request ID=2
|
5. Response ID=2 -----|--> (got resp 2)
|
6. (got req 1) <----+
7. Response ID=1 --------> [discarded due to unexpected ID]
Figure 11: Undesirable scenario
In Figure 11, the second EAP Request message with Identifier=1
arrives at the EAP peer after the third EAP Request message with arrives at the EAP peer after the third EAP Request message with
Identifier=2. As a result, the EAP peer accepts the second EAP Identifier=2. As a result, the EAP peer accepts the second EAP
Request as a new EAP Request while it is just an old EAP Request Request as a new EAP Request while it is just an old EAP Request that
that was already responded and the authentication might be totally was already responded and the authentication might be totally messed
messed up. up.
This problem occurs due to the fact that EAP doesn't recognize This problem occurs due to the fact that EAP doesn't recognize
duplicate packets in the scope of one EAP protocol run, but only in duplicate packets in the scope of one EAP protocol run, but only in
the scope of current and previous packet (i.e., request and response the scope of current and previous packet (i.e., request and response
message matching). When EAP is running over PPP or IEEE 802 links, message matching). When EAP is running over PPP or IEEE 802 links,
this is not a problem, because those link-layers have the ordering this is not a problem, because those link-layers have the ordering
invariant characteristic. invariant characteristic.
On the other hand, the PANA design has chosen UDP as its transport. On the other hand, the PANA design has chosen UDP as its transport.
Given that UDP does not provide ordered delivery of packets and PANA Given that UDP does not provide ordered delivery of packets and PANA
does not assume any specific link-layer technology to carry EAP, does not assume any specific link-layer technology to carry EAP, PANA
PANA messages need to have a sequence number. messages need to have a sequence number.
In the following text we describe two possible approaches for In the following text we describe two possible approaches for
sequence number handling in PANA. The first one makes use of a sequence number handling in PANA. The first one makes use of a
single sequence number whereas the latter utilizes two. Finally a single sequence number whereas the latter utilizes two. Finally a
comparison between the two approaches is provided. The method comparison between the two approaches is provided. The method
described in Section A.3.1. (i.e., the dual sequence number with described in Appendix A.3.1 (i.e., the dual sequence number with
orderly-delivery method) is suggested as the preferred method for orderly-delivery method) is suggested as the preferred method for
PANA transport. PANA transport.
A.2. Single sequence number approach Appendix A.2 Single sequence number approach
This section discusses several methods based on using a single This section discusses several methods based on using a single
sequence number for providing orderly message delivery. Sequence sequence number for providing orderly message delivery. Sequence
number handling for all methods discussed in Section A.2 must comply number handling for all methods discussed in Appendix A.2 must comply
to the following rules: to the following rules:
Rule 1: The sequence number starts from initial sequence number Rule 1: The sequence number starts from initial sequence number (ISN)
(ISN)
and is monotonically increased by 1. The arithmetic defined and is monotonically increased by 1. The arithmetic defined
in [RFC1982] is used for sequence number operation. in [RFC1982] is used for sequence number operation.
Rule 2: When a PAA sends an EAP message passed from EAP layer to a Rule 2: When a PAA sends an EAP message passed from EAP layer to a
PaC, a new sequence number is placed in the message, PaC, a new sequence number is placed in the message,
regardless of whether it is sent as a result of a regardless of whether it is sent as a result of a
retransmission at the EAP layer or not. retransmission at the EAP layer or not.
Note: It might be possible to define other mechanisms for sequence Note: It might be possible to define other mechanisms for sequence
number handling if it can be assumed that a PAA detects EAP number handling if it can be assumed that a PAA detects EAP
retransmissions. However, such an assumption heavily depends on EAP retransmissions. However, such an assumption heavily depends on EAP
implementation details in particular on EAP APIs, thus it was implementation details in particular on EAP APIs, thus it was decided
decided not to use such an assumption. not to use such an assumption.
Appendix A.2.1 Single sequence number with EAP retransmission method
A.2.1. Single sequence number with EAP retransmission method
Again, the following rules must hold: Again, the following rules must hold:
Rule 3: Use EAP layer retransmission for retransmitting EAP messages Rule 3: Use EAP layer retransmission for retransmitting EAP messages
(based on a timer expiration). (based on a timer expiration).
Rule 4: When the PaC receives a message from the PAA, it checks the Rule 4: When the PaC receives a message from the PAA, it checks the
sequence number and discards the message if the sequence sequence number and discards the message if the sequence
number is not greater than that of the last accepted number is not greater than that of the last accepted message.
message.
Rule 5: When the PAA receives a message from the PaC, it checks the Rule 5: When the PAA receives a message from the PaC, it checks the
sequence number and discards the message if the sequence sequence number and discards the message if the sequence
number does not match a pending request message. number does not match a pending request message.
PaC PAA Seq# Message PaC PAA Seq# Message
-------------------------------------------- --------------------------------------------
1. <------- (x) PANA-Auth-Request[EAP Req ID=1] 1. <------- (x) PANA-Auth-Request[EAP Req ID=1]
2. ---+ (x) PANA-Auth-Answer[EAP Res ID=1] 2. ---+ (x) PANA-Auth-Answer[EAP Res ID=1]
| (retransmission timeout at EAP-layer) | (retransmission timeout at EAP-layer)
3. | +-- (x+1) PANA-Auth-Request[EAP Req ID=1] 3. | +-- (x+1) PANA-Auth-Request[EAP Req ID=1]
| | | |
+-|--> (discarded due to Rule 5) +-|--> (discarded due to Rule 5)
| (retransmission timeout at EAP-layer) | (retransmission timeout at EAP-layer)
4. <----|-- (x+2) PANA-Auth-Request[EAP Req ID=1] 4. <----|-- (x+2) PANA-Auth-Request[EAP Req ID=1]
| |
5. -----|--> (x+2) PANA-Auth-Answer[EAP Res ID=1] 5. -----|--> (x+2) PANA-Auth-Answer[EAP Res ID=1]
| |
6. <----+ (discarded due to Rule 4) 6. <----+ (discarded due to Rule 4)
7. <------- (x+3) PANA-Auth-Request[EAP Req ID=2] 7. <------- (x+3) PANA-Auth-Request[EAP Req ID=2]
. .
. .
Figure 1: Example for Single sequence number with EAP retransmission Figure 12: Example for Single sequence number with EAP retransmission
method
This method is vulnerable to a blind DoS attack on the sequence This method is vulnerable to a blind DoS attack on the sequence
number since the PaC will accept quite a wide range of sequence number since the PaC will accept quite a wide range of sequence
numbers. For example, if an attacker blindly sends a bogus message numbers. For example, if an attacker blindly sends a bogus message
to a legitimate PaC with a randomly chosen sequence number, it will to a legitimate PaC with a randomly chosen sequence number, it will
be accepted by the PaC with 50% probability, and once this happens, be accepted by the PaC with 50% probability, and once this happens,
all messages sent from the communicating PAA will be discarded as all messages sent from the communicating PAA will be discarded as
long as they have a sequence number smaller than the accepted value. long as they have a sequence number smaller than the accepted value.
The problem of this method leads to a requirement for PaC to have a The problem of this method leads to a requirement for PaC to have a
narrow range of acceptable sequence numbers to make the blind DoS narrow range of acceptable sequence numbers to make the blind DoS
attack difficult. Note that the DoS attack cannot be prevented if attack difficult. Note that the DoS attack cannot be prevented if the
the attacker is on the same IP link as PaC and able to eavesdrop the attacker is on the same IP link as PaC and able to eavesdrop the PANA
PANA conversation. However, the attacker needs to put itself in conversation. However, the attacker needs to put itself in
promiscuous mode and thus spend more resources to eavesdrop and promiscuous mode and thus spend more resources to eavesdrop and
launch the attack (in other words, non-blind DoS attack is still launch the attack (in other words, non-blind DoS attack is still
possible as long as sequence numbers are unprotected.) possible as long as sequence numbers are unprotected.)
A.2.2. Single sequence number with PANA-layer retransmission method Appendix A.2.2 Single sequence number with PANA-layer retransmission
method
The next method is still based on using a single sequence number but The next method is still based on using a single sequence number but
the PANA-layer takes the responsibility of retransmission. The the PANA-layer takes the responsibility of retransmission. The
method uses the following rules in addition to the common rules method uses the following rules in addition to the common rules
described in section A.2. described in Appendix A.2.
Rule 3: Use PANA-layer retransmission for retransmitting both EAP Rule 3: Use PANA-layer retransmission for retransmitting both EAP and
and non-EAP messages (based on a timer expiration). EAP layer
non-EAP messages (based on a timer expiration). EAP layer
retransmission is turned off. Retransmission based on timer retransmission is turned off. Retransmission based on timer
occurs both on PaC and PAA side, but not on both sides occurs both on PaC and PAA side, but not on both sides
simultaneously. PAA does retransmission at least for simultaneously. PAA does retransmission at least for
PANA_Termination and PANA_Reauth messages, otherwise PaC PANA_Termination and PANA_Reauth messages, otherwise PaC
takes care of retransmission. takes care of retransmission.
Rule 4: When the PaC receives a message from the PAA, it accepts the Rule 4: When the PaC receives a message from the PAA, it accepts the
message if the sequence number is equal to that of the last message if the sequence number is equal to that of the last
accepted message + 1. If the sequence number is equal to accepted message + 1. If the sequence number is equal to
that of the last accepted message, the PaC retransmits the that of the last accepted message, the PaC retransmits the
skipping to change at page 46, line 38 skipping to change at page 49, line 496
the message. the message.
Rule 5: When the PAA receives a message from the PaC, it accepts the Rule 5: When the PAA receives a message from the PaC, it accepts the
message if the sequence number is equal to that of the last message if the sequence number is equal to that of the last
transmitted message. If the receiving sequence number is transmitted message. If the receiving sequence number is
equal to that of the last transmitted message - 1, the PAA equal to that of the last transmitted message - 1, the PAA
retransmits the last transmitted message and discard the retransmits the last transmitted message and discard the
received message. Otherwise, it silently discards the received message. Otherwise, it silently discards the
message. message.
Rule 6: The PaC retransmits the last transmitted EAP Response until Rule 6: The PaC retransmits the last transmitted EAP Response until a
a new EAP Request message or an EAP Success/Failure message new EAP Request message or an EAP Success/Failure message is
is received and accepted. received and accepted.
Rule 7: PAA must keep the copy of the last transmitted message and Rule 7: PAA must keep the copy of the last transmitted message and
must be able to retransmit it until either a valid message must be able to retransmit it until either a valid message is
is received and accepted by the PAA or a timer expires. The received and accepted by the PAA or a timer expires. The
timer is used if no new message will be sent from the PaC. timer is used if no new message will be sent from the PaC.
PaC PAA Seq# Message PaC PAA Seq# Message
-------------------------------------------- --------------------------------------------
1. <-------- (x) PANA-Auth-Request[EAP Req ID=1] 1. <-------- (x) PANA-Auth-Request[EAP Req ID=1]
2. ---+ (x) PANA-Auth-Answer[EAP Resp ID=1] 2. ---+ (x) PANA-Auth-Answer[EAP Resp ID=1]
| (retransmission timeout at PaC) | (retransmission timeout at PaC)
3. ---|----> (x) PANA-Auth-Answer[EAP Resp ID=1] 3. ---|----> (x) PANA-Auth-Answer[EAP Resp ID=1]
4. | +--- (x+1) PANA-Auth-Request[EAP Req ID=2] 4. | +--- (x+1) PANA-Auth-Request[EAP Req ID=2]
| | | |
+-|--> (duplicate detected) +-|--> (duplicate detected)
5. <----|--- (x+1) PANA-Auth-Request[EAP Req ID=2] 5. <----|--- (x+1) PANA-Auth-Request[EAP Req ID=2]
| |
6. -----|--> (x+1) PANA-Auth-Answer[EAP Resp ID=2] 6. -----|--> (x+1) PANA-Auth-Answer[EAP Resp ID=2]
| |
<----|--- (x+2) PANA-Auth-Request[EAP Req ID=3] <----|--- (x+2) PANA-Auth-Request[EAP Req ID=3]
7. -----|--> (x+2) PANA-Auth-Answer[EAP Resp ID=3] 7. -----|--> (x+2) PANA-Auth-Answer[EAP Resp ID=3]
<----+ (discarded by PaC) <----+ (discarded by PaC)
(retransmission timeout at PaC) (retransmission timeout at PaC)
8. --------> (x+2) PANA-Auth-Answer[EAP Resp ID=3] 8. --------> (x+2) PANA-Auth-Answer[EAP Resp ID=3]
9. lost<---- (x+3) PANA-Auth-Request[EAP Succ ID=3] 9. lost<---- (x+3) PANA-Auth-Request[EAP Succ ID=3]
(retransmission timeout at PaC) (retransmission timeout at PaC)
10.---->lost (x+2) PANA-Auth-Answer[EAP Resp ID=3] 10.---->lost (x+2) PANA-Auth-Answer[EAP Resp ID=3]
(retransmission timeout at PaC) (retransmission timeout at PaC)
11.--------> (x+2) PANA-Auth-Answer[EAP Resp ID=3] 11.--------> (x+2) PANA-Auth-Answer[EAP Resp ID=3]
12.<-------- (x+3) PANA-Bind-Request[EAP Succ ID=3] 12.<-------- (x+3) PANA-Bind-Request[EAP Succ ID=3]
(retransmission timer stopped at PaC) (retransmission timer stopped at PaC)
(deletion timeout at PAA) (deletion timeout at PAA)
(message (x+3) deleted at PAA) (message (x+3) deleted at PAA)
13.lost<---- (x+4) PANA-Termination-Request 13.lost<---- (x+4) PANA-Termination-Request
(retransmission timeout at PAA) (retransmission timeout at PAA)
14.<-------- (x+4) PANA-Termination-Request 14.<-------- (x+4) PANA-Termination-Request
15.---->lost (x+4) PANA-Termination-Answer 15.---->lost (x+4) PANA-Termination-Answer
(retransmission timeout at PAA) (retransmission timeout at PAA)
16.<-------- (x+4) PANA-Termination-Request 16.<-------- (x+4) PANA-Termination-Request
17.--------> (x+4) PANA-Termination-Answer 17.--------> (x+4) PANA-Termination-Answer
(retransmission timer stopped at PAA) (retransmission timer stopped at PAA)
Figure 2: Example for Single sequence number with PANA-layer Figure 13: Example for Single sequence number with PANA-layer
retransmission method retransmission
This method has an advantage of eliminating EAP layer retransmission This method has an advantage of eliminating EAP layer retransmission
by providing reliability at the PANA layer. Retransmission at the by providing reliability at the PANA layer. Retransmission at the EAP
EAP layer has a problem with determining an appropriate layer has a problem with determining an appropriate retransmission
retransmission timer value, which occurs when the lower-layer is timer value, which occurs when the lower-layer is unreliable. In
unreliable. In this case an EAP authenticator cannot distinguish this case an EAP authenticator cannot distinguish between (i) EAP
between (i) EAP Request or EAP Response message loss (in this case Request or EAP Response message loss (in this case the retransmission
the retransmission timer should be calculated based on network timer should be calculated based on network characteristics) and (ii)
characteristics) and (ii) long latency for EAP Response generation long latency for EAP Response generation due to e.g., user input etc.
due to e.g., user input etc. (in this case the retransmission timer (in this case the retransmission timer should be calculated based on
should be calculated based on user or application characteristics). user or application characteristics). In general, the retransmission
In general, the retransmission timer for case (ii) is longer than timer for case (ii) is longer than that for case (i). If case (i)
that for case (i). If case (i) happens while the retransmission happens while the retransmission timer is calculated based on user or
timer is calculated based on user or application characteristics, application characteristics, then it might frustrate an end user
then it might frustrate an end user since the completion of the since the completion of the authentication procedure takes
authentication procedure takes unnecessarily long. If case (ii) unnecessarily long. If case (ii) happens while the retransmission
happens while the retransmission timer is calculated based on timer is calculated based on network characteristics (i.e., RTT),
network characteristics (i.e., RTT), then unnecessarily traffic is then unnecessarily traffic is generated by retransmission. Note that
generated by retransmission. Note that in this method a PaC still in this method a PaC still cannot distinguish case (i) and case (iii)
cannot distinguish case (i) and case (iii) the EAP authenticator or the EAP authenticator or a backend authentication server is taking
a backend authentication server is taking time to generate an EAP time to generate an EAP Request.
Request.
A problem of this method is that it is based on the assumption that A problem of this method is that it is based on the assumption that
EAP authenticator does not send a new EAP message until an EAP EAP authenticator does not send a new EAP message until an EAP
Response to the outstanding EAP Request is received. However, this Response to the outstanding EAP Request is received. However, this
assumption does not hold at least EAP Success/Failure message which assumption does not hold at least EAP Success/Failure message which
does not need the outstanding EAP Request to be responded before does not need the outstanding EAP Request to be responded before
sending the EAP Success/Failure message. This would require sending the EAP Success/Failure message. This would require
timer-based retransmission not only at PaC side but also at PAA timer-based retransmission not only at PaC side but also at PAA side.
side.
Another problem occurs when a new EAP message overrides the Another problem occurs when a new EAP message overrides the
outstanding EAP Request, the PaC cannot assume any more that the outstanding EAP Request, the PaC cannot assume any more that the
sequence number of the next message to be accepted is the last sequence number of the next message to be accepted is the last
accepted message + 1. So the PaC needs to accept a range of accepted message + 1. So the PaC needs to accept a range of sequence
sequence numbers, instead of a single sequence number. These two numbers, instead of a single sequence number. These two additional
additional things would increase the complexity of this method. things would increase the complexity of this method.
A.3. Dual sequence number approach Appendix A.3 Dual sequence number approach
Based on the analysis of previous schemes, it is recognized that two Based on the analysis of previous schemes, it is recognized that two
sequence numbers are needed anyway, one for each direction. Two sequence numbers are needed anyway, one for each direction. Two
different methods are proposed based on this approach. Both methods different methods are proposed based on this approach. Both methods
have the following rules in common. have the following rules in common.
Rule 1: A PANA packet carries two sequence numbers: transmitted Rule 1: A PANA packet carries two sequence numbers: transmitted
sequence number (tseq) and received sequence number (rseq). sequence number (tseq) and received sequence number (rseq).
tseq starts from initial sequence number (ISN) and is tseq starts from initial sequence number (ISN) and is
monotonically increased by 1. The arithmetic defined in monotonically increased by 1. The arithmetic defined in
[RFC1982] is used for sequence number operation. It is [RFC1982] is used for sequence number operation. It is
assumed that the two sequence numbers have the same length assumed that the two sequence numbers have the same length
for simplicity. for simplicity.
Rule 2: When PAA or PAC sends a new message, a new sequence number Rule 2: When PAA or PAC sends a new message, a new sequence number is
is placed on the tseq field of message. Every transmitted placed on the tseq field of message. Every transmitted
message is given a new sequence number. message is given a new sequence number.
Rule 3: When a message is sent from PaC or PAA, rseq is copied from Rule 3: When a message is sent from PaC or PAA, rseq is copied from
the tseq field of the last accepted message. the tseq field of the last accepted message.
Rule 4: For messages which experience a PANA layer retransmission, Rule 4: For messages which experience a PANA layer retransmission,
the retransmission timer is stopped when the message is the retransmission timer is stopped when the message is
acknowledged. acknowledged.
It is possible to carry multiple EAP sequences in a single PANA It is possible to carry multiple EAP sequences in a single PANA
sequence, with using EAP Success/Failure message as a delimiter of sequence, with using EAP Success/Failure message as a delimiter of
each EAP sequence. In this case, EAP Success/Failure message needs each EAP sequence. In this case, EAP Success/Failure message needs
to be reliably delivered. to be reliably delivered.
A.3.1. Dual sequence number with orderly-delivery method Appendix A.3.1 Dual sequence number with orderly-delivery method
This method relies on EAP layer retransmission for EAP messages. This method relies on EAP layer retransmission for EAP messages.
This method is referred to as orderly-delivery method. The This method is referred to as orderly-delivery method. The following
following rules are used in addition to the common rules. rules are used in addition to the common rules.
Rule 5: Use the EAP-layer retransmission for retransmitting EAP Rule 5: Use the EAP-layer retransmission for retransmitting EAP
Requests (based on a timer expiration). For other PANA Requests (based on a timer expiration). For other PANA layer
layer messages that require a response from the peer, PANA messages that require a response from the peer, PANA layer
layer has its own mechanism to retransmit the request until has its own mechanism to retransmit the request until it gets
it gets a response or gives up. A new tseq value is always a response or gives up. A new tseq value is always used when
used when sending any message even when it is retransmitted sending any message even when it is retransmitted at PANA
at PANA layer. layer.
Rule 6: When a message is received, it is accepted if (i) the tseq Rule 6: When a message is received, it is accepted if (i) the tseq
value is greater than the tseq of the last accepted message value is greater than the tseq of the last accepted message
and (ii) the rseq falls in the range between the tseq of the and (ii) the rseq falls in the range between the tseq of the
last acknowledged message + 1 and the tseq of the last last acknowledged message + 1 and the tseq of the last
transmitted message. Otherwise, the received message is transmitted message. Otherwise, the received message is
discarded. discarded.
PaC PAA (tseq,rseq) Message PaC PAA (tseq,rseq) Message
-------------------------------------------------- --------------------------------------------------
1. <------- (x,y) PANA-Auth-Request[EAP Req, ID=1] 1. <------- (x,y) PANA-Auth-Request[EAP Req, ID=1]
2. -------> (y+1,x) PANA-Auth-Answer[EAP Resp, ID=1] 2. -------> (y+1,x) PANA-Auth-Answer[EAP Resp, ID=1]
3. <------- (x+1,y+1) PANA-Auth-Request[EAP Req, ID=2] 3. <------- (x+1,y+1) PANA-Auth-Request[EAP Req, ID=2]
4. --->lost (y+2,x+1) PANA-Auth-Answer[EAP Resp, ID=2] 4. --->lost (y+2,x+1) PANA-Auth-Answer[EAP Resp, ID=2]
(retransmission timeout at EAP layer) (retransmission timeout at EAP layer)
5. <------- (x+2,y+1) PANA-Auth-Request [EAP Req, ID=2] 5. <------- (x+2,y+1) PANA-Auth-Request [EAP Req, ID=2]
6. -------> (y+3,x+2) PANA-Auth-Answer[EAP Resp, ID=2] 6. -------> (y+3,x+2) PANA-Auth-Answer[EAP Resp, ID=2]
7. lost<--- (x+3,y+3) PANA-Auth-Request[EAP Req, ID=3] 7. lost<--- (x+3,y+3) PANA-Auth-Request[EAP Req, ID=3]
(retransmission timeout at EAP layer) (retransmission timeout at EAP layer)
8. +---- (x+4,y+3) PANA-Auth-Answer[EAP Req, ID=3] 8. +---- (x+4,y+3) PANA-Auth-Answer[EAP Req, ID=3]
| (retransmission timeout at EAP layer) | (retransmission timeout at EAP layer)
9. <--|---- (x+5,y+3) PANA-Auth-Request[EAP Req, ID=3] 9. <--|---- (x+5,y+3) PANA-Auth-Request[EAP Req, ID=3]
10.---|---> (y+4,x+5) PANA-Auth-Answer[EAP Resp, ID=3] 10.---|---> (y+4,x+5) PANA-Auth-Answer[EAP Resp, ID=3]
| |
<--+ (out of order. discarded) <--+ (out of order. discarded)
11.lost<--- (x+6,y+4) PANA-Bind-Request[EAP Succ, ID=3] 11.lost<--- (x+6,y+4) PANA-Bind-Request[EAP Succ, ID=3]
(retransmission timeout at PAA) (retransmission timeout at PAA)
12.<------- (x+7,y+4) PANA-Bind-Request[EAP Succ, ID=3] 12.<------- (x+7,y+4) PANA-Bind-Request[EAP Succ, ID=3]
13.--->lost (y+5,x+7) PANA-Bind-Answer 13.--->lost (y+5,x+7) PANA-Bind-Answer
(retransmission timeout at PAA) (retransmission timeout at PAA)
14.<------- (x+8,y+4) PANA-Bind-Request[EAP Succ, ID=3] 14.<------- (x+8,y+4) PANA-Bind-Request[EAP Succ, ID=3]
(dupicate detected by PaC) (duplicate detected by PaC)
15.-------> (y+6,x+8) PANA-Bind-Answer 15.-------> (y+6,x+8) PANA-Bind-Answer
Figure 3: Example for Dual sequence number with orderly-delivery Figure 14: Example for Dual sequence number with orderly-delivery
method
A.3.2. Dual sequence number with reliable-delivery method Appendix A.3.2 Dual sequence number with reliable-delivery method
This method relies solely on PANA layer retransmission for all This method relies solely on PANA layer retransmission for all
messages. This method is referred to as reliable-delivery method. messages. This method is referred to as reliable-delivery method.
The following additional rules are applied in addition to the common The following additional rules are applied in addition to the common
rules. rules.
Rule 5: Use the PANA layer retransmission for retransmitting all Rule 5: Use the PANA layer retransmission for retransmitting all
messages (based on a timer expiration). EAP retransmission messages (based on a timer expiration). EAP retransmission
is turned off. is turned off.
skipping to change at page 51, line 5 skipping to change at page 68, line 36
and (ii) the rseq falls in the range between the tseq of the and (ii) the rseq falls in the range between the tseq of the
last acknowledged message and the tseq of the last last acknowledged message and the tseq of the last
transmitted message. Otherwise, the received message is transmitted message. Otherwise, the received message is
discarded. discarded.
Rule 8: When a duplicate message is received, the last transmitted Rule 8: When a duplicate message is received, the last transmitted
message is retransmitted if the received message is not an message is retransmitted if the received message is not an
ACK. A message is considered as duplicate if its tseq value ACK. A message is considered as duplicate if its tseq value
is equal to the tseq of the last accepted message. is equal to the tseq of the last accepted message.
PaC PAA (tseq,rseq) Message PaC PAA (tseq,rseq) Message
-------------------------------------------------- --------------------------------------------------
1. <------- (x,y) PANA-Auth-Request[EAP Req, ID=1] 1. <------- (x,y) PANA-Auth-Request[EAP Req, ID=1]
(user input ongoing) (user input ongoing)
2. -------> (y+1,x) PANA-Auth-Answer 2. -------> (y+1,x) PANA-Auth-Answer
(user input completed) (user input completed)
3. -------> (y+2,x) PANA-Auth-Answer[EAP Resp, ID=1] 3. -------> (y+2,x) PANA-Auth-Answer[EAP Resp, ID=1]
4. <------- (x+1,y+2) PANA-Auth-Request [EAP Req, ID=2] 4. <------- (x+1,y+2) PANA-Auth-Request [EAP Req, ID=2]
5. --->lost (y+3,x+1) PANA-Auth-Answer[EAP Resp, ID=2] 5. --->lost (y+3,x+1) PANA-Auth-Answer[EAP Resp, ID=2]
(retransmission timeout at PAA) (retransmission timeout at PAA)
6. <------- (x+1,y+2) PANA-Auth-Request [EAP Req, ID=2] 6. <------- (x+1,y+2) PANA-Auth-Request [EAP Req, ID=2]
(duplicate detected by PaC) (duplicate detected by PaC)
7. -------> (y+3,x+1) PANA-Auth-Answer[EAP Resp, ID=2] 7. -------> (y+3,x+1) PANA-Auth-Answer[EAP Resp, ID=2]
8. lost<--- (x+2,y+3) PANA-Auth-Request [EAP Req, ID=3] 8. lost<--- (x+2,y+3) PANA-Auth-Request [EAP Req, ID=3]
(retransmission timeout at PaC) (retransmission timeout at PaC)
9. -------> (y+3,x+1) PANA-Auth-Answer[EAP Resp, ID=2]
(duplicate detected at PAA)
10.<------- (x+2,y+3) PANA-Auth-Request [EAP Req, ID=3]
11.---+ (y+4,x+2) PANA-Auth-Answer[EAP Resp, ID=3]
| (retransmission timeout at PAA)
12.<--|---- (x+2,y+3) PANA-Auth-Request [EAP Req, ID=3]
| (duplicate detected at PaC)
13.---|---> (y+4,x+2) PANA-Auth-Answer[EAP Resp, ID=3]
14.<--|---- (x+3,y+4) PANA-Bind-Request[EAP Succ, ID=3]
15.---|---> (y+5,x+3) PANA-Bind-Answer
+---> (out of order. discarded)
Figure 4: Example for Dual sequence number with reliable-delivery 9. -------> (y+3,x+1) PANA-Auth-Answer[EAP Resp, ID=2]
method (duplicate detected at PAA)
10.<------- (x+2,y+3) PANA-Auth-Request [EAP Req, ID=3]
11.---+ (y+4,x+2) PANA-Auth-Answer[EAP Resp, ID=3]
| (retransmission timeout at PAA)
12.<--|---- (x+2,y+3) PANA-Auth-Request [EAP Req, ID=3]
| (duplicate detected at PaC)
13.---|---> (y+4,x+2) PANA-Auth-Answer[EAP Resp, ID=3]
14.<--|---- (x+3,y+4) PANA-Bind-Request[EAP Succ, ID=3]
15.---|---> (y+5,x+3) PANA-Bind-Answer
+---> (out of order. discarded)
A.3.3 Comparison of the dual sequence number methods Figure 15: Example for Dual sequence number with reliable-delivery
method
Appendix A.3.3 Comparison of the dual sequence number methods
The orderly-delivery method is simpler than the reliable-delivery The orderly-delivery method is simpler than the reliable-delivery
method in that the former does not allow sending a separate ACK method in that the former does not allow sending a separate ACK while
while the latter does. the latter does.
In terms of authentication performance, the reliable-delivery method In terms of authentication performance, the reliable-delivery method
is better than the orderly-delivery method in that the former gives is better than the orderly-delivery method in that the former gives
more detailed status of the link than the latter, e.g., an entity more detailed status of the link than the latter, e.g., an entity can
can know whether a request has reached the communicating peer know whether a request has reached the communicating peer without
without before receiving a response. The reliable-delivery can before receiving a response. The reliable-delivery can reduce
reduce retransmission traffic and communication delay that would retransmission traffic and communication delay that would occur if
occur if there is no reliability, as described in section A.2.2. there is no reliability, as described in section Appendix A.2.2
Appendix A.4 Consensus
A.4 Consensus
Although it is recognizable that the reliable-delivery method would Although it is recognizable that the reliable-delivery method would
be important in terms of improvement of overall authentication be important in terms of improvement of overall authentication
latency, we believe that this is a performance problem of EAP and latency, we believe that this is a performance problem of EAP and not
not a problem of PANA. It is agreed that solving the EAP problem is a problem of PANA. It is agreed that solving the EAP problem is not
not the scope of PANA and simplicity is more important factor in the the scope of PANA and simplicity is more important factor in the PANA
PANA design. design.
As a consequence, the orderly-delivery method is chosen as the As a consequence, the orderly-delivery method is chosen as the
message transport part of PANA. message transport part of PANA.
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