< draft-ietf-dots-signal-channel-31.txt   draft-ietf-dots-signal-channel-32.txt >
DOTS T. Reddy, Ed. DOTS T. Reddy, Ed.
Internet-Draft McAfee Internet-Draft McAfee
Intended status: Standards Track M. Boucadair, Ed. Intended status: Standards Track M. Boucadair, Ed.
Expires: September 29, 2019 Orange Expires: November 10, 2019 Orange
P. Patil P. Patil
Cisco Cisco
A. Mortensen A. Mortensen
Arbor Networks, Inc. Arbor Networks, Inc.
N. Teague N. Teague
Verisign, Inc. Verisign, Inc.
March 28, 2019 May 9, 2019
Distributed Denial-of-Service Open Threat Signaling (DOTS) Signal Distributed Denial-of-Service Open Threat Signaling (DOTS) Signal
Channel Specification Channel Specification
draft-ietf-dots-signal-channel-31 draft-ietf-dots-signal-channel-32
Abstract Abstract
This document specifies the DOTS signal channel, a protocol for This document specifies the DOTS signal channel, a protocol for
signaling the need for protection against Distributed Denial-of- signaling the need for protection against Distributed Denial-of-
Service (DDoS) attacks to a server capable of enabling network Service (DDoS) attacks to a server capable of enabling network
traffic mitigation on behalf of the requesting client. traffic mitigation on behalf of the requesting client.
A companion document defines the DOTS data channel, a separate A companion document defines the DOTS data channel, a separate
reliable communication layer for DOTS management and configuration reliable communication layer for DOTS management and configuration
skipping to change at page 2, line 25 skipping to change at page 2, line 25
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/. Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on September 29, 2019. This Internet-Draft will expire on November 10, 2019.
Copyright Notice Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the Copyright (c) 2019 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of (https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
skipping to change at page 2, line 51 skipping to change at page 2, line 51
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 6 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 6
3. Design Overview . . . . . . . . . . . . . . . . . . . . . . . 6 3. Design Overview . . . . . . . . . . . . . . . . . . . . . . . 6
4. DOTS Signal Channel: Messages & Behaviors . . . . . . . . . . 9 4. DOTS Signal Channel: Messages & Behaviors . . . . . . . . . . 9
4.1. DOTS Server(s) Discovery . . . . . . . . . . . . . . . . 9 4.1. DOTS Server(s) Discovery . . . . . . . . . . . . . . . . 9
4.2. CoAP URIs . . . . . . . . . . . . . . . . . . . . . . . . 9 4.2. CoAP URIs . . . . . . . . . . . . . . . . . . . . . . . . 9
4.3. Happy Eyeballs for DOTS Signal Channel . . . . . . . . . 10 4.3. Happy Eyeballs for DOTS Signal Channel . . . . . . . . . 10
4.4. DOTS Mitigation Methods . . . . . . . . . . . . . . . . . 11 4.4. DOTS Mitigation Methods . . . . . . . . . . . . . . . . . 12
4.4.1. Request Mitigation . . . . . . . . . . . . . . . . . 12 4.4.1. Request Mitigation . . . . . . . . . . . . . . . . . 13
4.4.2. Retrieve Information Related to a Mitigation . . . . 27 4.4.2. Retrieve Information Related to a Mitigation . . . . 29
4.4.2.1. DOTS Servers Sending Mitigation Status . . . . . 32 4.4.2.1. DOTS Servers Sending Mitigation Status . . . . . 34
4.4.2.2. DOTS Clients Polling for Mitigation Status . . . 35 4.4.2.2. DOTS Clients Polling for Mitigation Status . . . 37
4.4.3. Efficacy Update from DOTS Clients . . . . . . . . . . 36 4.4.3. Efficacy Update from DOTS Clients . . . . . . . . . . 38
4.4.4. Withdraw a Mitigation . . . . . . . . . . . . . . . . 38 4.4.4. Withdraw a Mitigation . . . . . . . . . . . . . . . . 40
4.5. DOTS Signal Channel Session Configuration . . . . . . . . 39 4.5. DOTS Signal Channel Session Configuration . . . . . . . . 41
4.5.1. Discover Configuration Parameters . . . . . . . . . . 41 4.5.1. Discover Configuration Parameters . . . . . . . . . . 43
4.5.2. Convey DOTS Signal Channel Session Configuration . . 45 4.5.2. Convey DOTS Signal Channel Session Configuration . . 47
4.5.3. Configuration Freshness and Notifications . . . . . . 50 4.5.3. Configuration Freshness and Notifications . . . . . . 52
4.5.4. Delete DOTS Signal Channel Session Configuration . . 51 4.5.4. Delete DOTS Signal Channel Session Configuration . . 53
4.6. Redirected Signaling . . . . . . . . . . . . . . . . . . 52 4.6. Redirected Signaling . . . . . . . . . . . . . . . . . . 54
4.7. Heartbeat Mechanism . . . . . . . . . . . . . . . . . . . 54 4.7. Heartbeat Mechanism . . . . . . . . . . . . . . . . . . . 56
5. DOTS Signal Channel YANG Modules . . . . . . . . . . . . . . 55 5. DOTS Signal Channel YANG Modules . . . . . . . . . . . . . . 57
5.1. Tree Structure . . . . . . . . . . . . . . . . . . . . . 55 5.1. Tree Structure . . . . . . . . . . . . . . . . . . . . . 57
5.2. IANA DOTS Signal Channel YANG Module . . . . . . . . . . 57 5.2. IANA DOTS Signal Channel YANG Module . . . . . . . . . . 59
5.3. IETF DOTS Signal Channel YANG Module . . . . . . . . . . 61 5.3. IETF DOTS Signal Channel YANG Module . . . . . . . . . . 63
6. YANG/JSON Mapping Parameters to CBOR . . . . . . . . . . . . 71 6. YANG/JSON Mapping Parameters to CBOR . . . . . . . . . . . . 74
7. (D)TLS Protocol Profile and Performance Considerations . . . 74 7. (D)TLS Protocol Profile and Performance Considerations . . . 76
7.1. (D)TLS Protocol Profile . . . . . . . . . . . . . . . . . 74 7.1. (D)TLS Protocol Profile . . . . . . . . . . . . . . . . . 76
7.2. (D)TLS 1.3 Considerations . . . . . . . . . . . . . . . . 75 7.2. (D)TLS 1.3 Considerations . . . . . . . . . . . . . . . . 77
7.3. DTLS MTU and Fragmentation . . . . . . . . . . . . . . . 77 7.3. DTLS MTU and Fragmentation . . . . . . . . . . . . . . . 79
8. Mutual Authentication of DOTS Agents & Authorization of DOTS 8. Mutual Authentication of DOTS Agents & Authorization of DOTS
Clients . . . . . . . . . . . . . . . . . . . . . . . . . . . 78 Clients . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 79 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 82
9.1. DOTS Signal Channel UDP and TCP Port Number . . . . . . . 79 9.1. DOTS Signal Channel UDP and TCP Port Number . . . . . . . 82
9.2. Well-Known 'dots' URI . . . . . . . . . . . . . . . . . . 79 9.2. Well-Known 'dots' URI . . . . . . . . . . . . . . . . . . 82
9.3. Media Type Registration . . . . . . . . . . . . . . . . . 80 9.3. Media Type Registration . . . . . . . . . . . . . . . . . 82
9.4. CoAP Content-Formats Registration . . . . . . . . . . . . 80 9.4. CoAP Content-Formats Registration . . . . . . . . . . . . 83
9.5. CBOR Tag Registration . . . . . . . . . . . . . . . . . . 80 9.5. CBOR Tag Registration . . . . . . . . . . . . . . . . . . 83
9.6. DOTS Signal Channel Protocol Registry . . . . . . . . . . 81 9.6. DOTS Signal Channel Protocol Registry . . . . . . . . . . 84
9.6.1. DOTS Signal Channel CBOR Key Values Sub-Registry . . 81 9.6.1. DOTS Signal Channel CBOR Key Values Sub-Registry . . 84
9.6.1.1. Registration Template . . . . . . . . . . . . . . 81 9.6.1.1. Registration Template . . . . . . . . . . . . . . 84
9.6.1.2. Initial Sub-Registry Content . . . . . . . . . . 83 9.6.1.2. Initial Sub-Registry Content . . . . . . . . . . 85
9.6.2. Status Codes Sub-Registry . . . . . . . . . . . . . . 84 9.6.2. Status Codes Sub-Registry . . . . . . . . . . . . . . 87
9.6.3. Conflict Status Codes Sub-Registry . . . . . . . . . 86 9.6.3. Conflict Status Codes Sub-Registry . . . . . . . . . 88
9.6.4. Conflict Cause Codes Sub-Registry . . . . . . . . . . 88 9.6.4. Conflict Cause Codes Sub-Registry . . . . . . . . . . 90
9.6.5. Attack Status Codes Sub-Registry . . . . . . . . . . 88 9.6.5. Attack Status Codes Sub-Registry . . . . . . . . . . 90
9.7. DOTS Signal Channel YANG Modules . . . . . . . . . . . . 89 9.7. DOTS Signal Channel YANG Modules . . . . . . . . . . . . 91
10. Security Considerations . . . . . . . . . . . . . . . . . . . 90 10. Security Considerations . . . . . . . . . . . . . . . . . . . 92
11. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 92 11. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 94
12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 92 12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 95
13. References . . . . . . . . . . . . . . . . . . . . . . . . . 93 13. References . . . . . . . . . . . . . . . . . . . . . . . . . 95
13.1. Normative References . . . . . . . . . . . . . . . . . . 93 13.1. Normative References . . . . . . . . . . . . . . . . . . 95
13.2. Informative References . . . . . . . . . . . . . . . . . 95 13.2. Informative References . . . . . . . . . . . . . . . . . 98
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 100 Appendix A. CUID Generation . . . . . . . . . . . . . . . . . . 103
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 103
1. Introduction 1. Introduction
A distributed denial-of-service (DDoS) attack is a distributed A distributed denial-of-service (DDoS) attack is a distributed
attempt to make machines or network resources unavailable to their attempt to make machines or network resources unavailable to their
intended users. In most cases, sufficient scale for an effective intended users. In most cases, sufficient scale for an effective
attack can be achieved by compromising enough end-hosts and using attack can be achieved by compromising enough end-hosts and using
those infected hosts to perpetrate and amplify the attack. The those infected hosts to perpetrate and amplify the attack. The
victim in this attack can be an application server, a host, a router, victim in this attack can be an application server, a host, a router,
a firewall, or an entire network. a firewall, or an entire network.
skipping to change at page 7, line 5 skipping to change at page 7, line 5
| TLS | DTLS | | TLS | DTLS |
+----------+----------+ +----------+----------+
| TCP | UDP | | TCP | UDP |
+----------+----------+ +----------+----------+
| IP | | IP |
+---------------------+ +---------------------+
Figure 3: Abstract Layering of DOTS Signal Channel over CoAP over Figure 3: Abstract Layering of DOTS Signal Channel over CoAP over
(D)TLS (D)TLS
By default, a DOTS signal channel MUST run over port number TBD as In some cases, a DOTS client and server may have mutual agreement to
defined in Section 9.1, for both UDP and TCP, unless the DOTS server use a specific port number, such as by explicit configuration or
has a mutual agreement with its DOTS clients to use a different port dynamic discovery [I-D.ietf-dots-server-discovery]. Absent such
number. DOTS clients MAY alternatively support means to dynamically mutual agreement, the DOTS signal channel MUST run over port number
discover the ports used by their DOTS servers (e.g., TBD as defined in Section 9.1, for both UDP and TCP. In order to use
[I-D.boucadair-dots-server-discovery]). In order to use a distinct a distinct port number (as opposed to TBD), DOTS clients and servers
port number (as opposed to TBD), DOTS clients and servers SHOULD SHOULD support a configurable parameter to supply the port number to
support a configurable parameter to supply the port number to use. use. The rationale for not using the default port number 5684
The rationale for not using the default port number 5684 ((D)TLS ((D)TLS CoAP) is to allow for differentiated behaviors in
CoAP) is to allow for differentiated behaviors in environments where environments where both a DOTS gateway and an IoT gateway (e.g.,
both a DOTS gateway and an IoT gateway (e.g., Figure 3 of [RFC7452]) Figure 3 of [RFC7452]) are present.
are present.
The signal channel uses the "coaps" URI scheme defined in Section 6 The signal channel uses the "coaps" URI scheme defined in Section 6
of [RFC7252] and the "coaps+tcp" URI scheme defined in Section 8.2 of of [RFC7252] and the "coaps+tcp" URI scheme defined in Section 8.2 of
[RFC8323] to identify DOTS server resources accessible using CoAP [RFC8323] to identify DOTS server resources accessible using CoAP
over UDP secured with DTLS and CoAP over TCP secured with TLS, over UDP secured with DTLS and CoAP over TCP secured with TLS,
respectively. respectively.
The signal channel is initiated by the DOTS client (Section 4.4). The DOTS signal channel can be established between two DOTS agents
Once the signal channel is established, the DOTS agents periodically prior or during an attack. The DOTS signal channel is initiated by
send heartbeats to keep the channel active (Section 4.7). At any the DOTS client. The DOTS client can then negotiate, configure, and
time, the DOTS client may send a mitigation request message to a DOTS retrieve the DOTS signal channel session behavior with its DOTS peer
server over the active channel. While mitigation is active (because (Section 4.5). Once the signal channel is established, the DOTS
of the higher likelihood of packet loss during a DDoS attack), the agents periodically send heartbeats to keep the channel active
DOTS server periodically sends status messages to the client, (Section 4.7). At any time, the DOTS client may send a mitigation
including basic mitigation feedback details. Mitigation remains request message (Section 4.4) to a DOTS server over the active signal
active until the DOTS client explicitly terminates mitigation, or the channel. While mitigation is active (because of the higher
mitigation lifetime expires. likelihood of packet loss during a DDoS attack), the DOTS server
periodically sends status messages to the client, including basic
mitigation feedback details. Mitigation remains active until the
DOTS client explicitly terminates mitigation, or the mitigation
lifetime expires. Also, the DOTS server may rely on the signal
channel session loss to trigger mitigation for pre-configured
mitigation requests (if any).
DOTS signaling can happen with DTLS over UDP and TLS over TCP. DOTS signaling can happen with DTLS over UDP and TLS over TCP.
Likewise, DOTS requests may be sent using IPv4 or IPv6 transfer Likewise, DOTS requests may be sent using IPv4 or IPv6 transfer
capabilities. A Happy Eyeballs procedure for DOTS signal channel is capabilities. A Happy Eyeballs procedure for DOTS signal channel is
specified in Section 4.3. specified in Section 4.3.
A DOTS client is entitled to access only to resources it creates. In A DOTS client is entitled to access only to resources it creates. In
particular, a DOTS client can not retrieve data related to mitigation particular, a DOTS client can not retrieve data related to mitigation
requests created by other DOTS clients of the same DOTS client requests created by other DOTS clients of the same DOTS client
domain. domain.
skipping to change at page 8, line 7 skipping to change at page 8, line 11
Messages exchanged between DOTS agents are serialized using Concise Messages exchanged between DOTS agents are serialized using Concise
Binary Object Representation (CBOR) [RFC7049], a binary encoding Binary Object Representation (CBOR) [RFC7049], a binary encoding
scheme designed for small code and message size. CBOR-encoded scheme designed for small code and message size. CBOR-encoded
payloads are used to carry signal channel-specific payload messages payloads are used to carry signal channel-specific payload messages
which convey request parameters and response information such as which convey request parameters and response information such as
errors. In order to allow reusing data models across protocols, errors. In order to allow reusing data models across protocols,
[RFC7951] specifies the JavaScript Object Notation (JSON) encoding of [RFC7951] specifies the JavaScript Object Notation (JSON) encoding of
YANG-modeled data. A similar effort for CBOR is defined in YANG-modeled data. A similar effort for CBOR is defined in
[I-D.ietf-core-yang-cbor]. [I-D.ietf-core-yang-cbor].
DOTS agents primarily determine that a CBOR data structure is a DOTS DOTS agents determine that a CBOR data structure is a DOTS signal
signal channel object from the application context, such as from the channel object from the application context, such as from the port
port number assigned to the DOTS signal channel. The other method number assigned to the DOTS signal channel. The other method DOTS
DOTS agents use to indicate that a CBOR data structure is a DOTS agents use to indicate that a CBOR data structure is a DOTS signal
signal channel object is the use of the "application/dots+cbor" channel object is the use of the "application/dots+cbor" content type
content type (Section 9.3). (Section 9.3).
This document specifies a YANG module for representing DOTS This document specifies a YANG module for representing DOTS
mitigation scopes, DOTS signal channel session configuration data, mitigation scopes, DOTS signal channel session configuration data,
and DOTS redirected signalling (Section 5). Representing these data and DOTS redirected signaling (Section 5). All parameters in the
as CBOR data can either follow the rules in [I-D.ietf-core-yang-cbor] payload of the DOTS signal channel are mapped to CBOR types as
or those in [RFC7951] combined with JSON/CBOR conversion rules in specified in Table 4 (Section 6).
[RFC7049]; both approaches produce a valid encoding. All parameters
in the payload of the DOTS signal channel are mapped to CBOR types as
specified in Section 6.
In order to prevent fragmentation, DOTS agents must follow the In order to prevent fragmentation, DOTS agents must follow the
recommendations documented in Section 4.6 of [RFC7252]. Refer to recommendations documented in Section 4.6 of [RFC7252]. Refer to
Section 7.3 for more details. Section 7.3 for more details.
DOTS agents MUST support GET, PUT, and DELETE CoAP methods. The DOTS agents MUST support GET, PUT, and DELETE CoAP methods. The
payload included in CoAP responses with 2.xx Response Codes MUST be payload included in CoAP responses with 2.xx Response Codes MUST be
of content type "application/dots+cbor". CoAP responses with 4.xx of content type "application/dots+cbor". CoAP responses with 4.xx
and 5.xx error Response Codes MUST include a diagnostic payload and 5.xx error Response Codes MUST include a diagnostic payload
(Section 5.5.2 of [RFC7252]). The Diagnostic Payload may contain (Section 5.5.2 of [RFC7252]). The Diagnostic Payload may contain
skipping to change at page 9, line 25 skipping to change at page 9, line 26
gateway will need to update the DOTS messages, based upon the gateway will need to update the DOTS messages, based upon the
local translator's binding table. local translator's binding table.
4. DOTS Signal Channel: Messages & Behaviors 4. DOTS Signal Channel: Messages & Behaviors
4.1. DOTS Server(s) Discovery 4.1. DOTS Server(s) Discovery
This document assumes that DOTS clients are provisioned with the This document assumes that DOTS clients are provisioned with the
reachability information of their DOTS server(s) using any of a reachability information of their DOTS server(s) using any of a
variety of means (e.g., local configuration, or dynamic means such as variety of means (e.g., local configuration, or dynamic means such as
DHCP). The description of such means is out of scope of this DHCP [I-D.ietf-dots-server-discovery]). The description of such
document. means is out of scope of this document.
Likewise, it is out of scope of this document to specify the behavior Likewise, it is out of scope of this document to specify the behavior
to be followed by a DOTS client to send DOTS requests when multiple to be followed by a DOTS client to send DOTS requests when multiple
DOTS servers are provisioned (e.g., contact all DOTS servers, select DOTS servers are provisioned (e.g., contact all DOTS servers, select
one DOTS server among the list). one DOTS server among the list). Such behavior is specified in other
documents (e.g. [I-D.ietf-dots-multihoming]).
4.2. CoAP URIs 4.2. CoAP URIs
The DOTS server MUST support the use of the path-prefix of "/.well- The DOTS server MUST support the use of the path-prefix of "/.well-
known/" as defined in [RFC5785] and the registered name of "dots". known/" as defined in [RFC5785] and the registered name of "dots".
Each DOTS operation is indicated by a path-suffix that indicates the Each DOTS operation is indicated by a path-suffix that indicates the
intended operation. The operation path (Table 1) is appended to the intended operation. The operation path (Table 1) is appended to the
path-prefix to form the URI used with a CoAP request to perform the path-prefix to form the URI used with a CoAP request to perform the
desired DOTS operation. desired DOTS operation.
skipping to change at page 10, line 29 skipping to change at page 10, line 39
dual-stack DOTS client may experience a significant connection delay dual-stack DOTS client may experience a significant connection delay
compared to an IPv4-only DOTS client, in the same network conditions. compared to an IPv4-only DOTS client, in the same network conditions.
The other problem is that if a middlebox between the DOTS client and The other problem is that if a middlebox between the DOTS client and
DOTS server is configured to block UDP traffic, the DOTS client will DOTS server is configured to block UDP traffic, the DOTS client will
fail to establish a DTLS association with the DOTS server and, as a fail to establish a DTLS association with the DOTS server and, as a
consequence, will have to fall back to TLS over TCP, thereby consequence, will have to fall back to TLS over TCP, thereby
incurring significant connection delays. incurring significant connection delays.
To overcome these connection setup problems, the DOTS client attempts To overcome these connection setup problems, the DOTS client attempts
to connect to its DOTS server(s) using both IPv6 and IPv4, and tries to connect to its DOTS server(s) using both IPv6 and IPv4, and tries
both DTLS over UDP and TLS over TCP in a manner similar to the Happy both DTLS over UDP and TLS over TCP following a DOTS Happy Eyeballs
Eyeballs mechanism [RFC8305]. These connection attempts are approach. To some extent, this approach is similar to the Happy
Eyeballs mechanism defined in [RFC8305]. The connection attempts are
performed by the DOTS client when it initializes, or in general when performed by the DOTS client when it initializes, or in general when
it has to select an address family and transport to contact its DOTS it has to select an address family and transport to contact its DOTS
server. The results of the Happy Eyeballs procedure are used by the server. The results of the Happy Eyeballs procedure are used by the
DOTS client for sending its subsequent messages to the DOTS server. DOTS client for sending its subsequent messages to the DOTS server.
Note that the DOTS client after successfully establishing a The difference in behavior with respect to the Happy Eyeballs
connection MUST cache information regarding the outcome of each mechanism [RFC8305] are listed below:
connection attempt for a specific time period, and it uses that
information to avoid thrashing the network with subsequent attempts.
The order of preference of the DOTS signal channel address family and o The order of preference of the DOTS signal channel address family
transport protocol (most preferred first) is: UDP over IPv6, UDP over and transport protocol (most preferred first) is: UDP over IPv6,
IPv4, TCP over IPv6, and finally TCP over IPv4. This order adheres UDP over IPv4, TCP over IPv6, and finally TCP over IPv4. This
to the address preference order specified in [RFC6724] and the DOTS order adheres to the address preference order specified in
signal channel preference which privileges the use of UDP over TCP
(to avoid TCP's head of line blocking).
In reference to Figure 4, the DOTS client sends two TCP SYNs and two [RFC6724] and the DOTS signal channel preference which privileges
DTLS ClientHello messages at the same time over IPv6 and IPv4. In the use of UDP over TCP (to avoid TCP's head of line blocking).
this example, it is assumed that the IPv6 path is broken and UDP
traffic is dropped by a middlebox but has little impact to the DOTS
client because there is no long delay before using IPv4 and TCP. The
DOTS client periodically repeats the mechanism to discover whether
DOTS signal channel messages with DTLS over UDP becomes available
from the DOTS server, so the DOTS client can migrate the DOTS signal
channel from TCP to UDP. Such probing SHOULD NOT be done more
frequently than every 24 hours and MUST NOT be done more frequently
than every 5 minutes.
A single DOTS signal channel between DOTS agents can be used to o The DOTS client after successfully establishing a connection MUST
exchange multiple DOTS signal messages. To reduce DOTS client and cache information regarding the outcome of each connection attempt
DOTS server workload, DOTS clients SHOULD re-use the (D)TLS session. for a specific time period, and it uses that information to avoid
thrashing the network with subsequent attempts. The cached
information is flushed when its age exceeds a specific time period
on the order of few minutes (e.g., 10 mn). Typically, if the DOTS
client has to re-establish the connection with the same DOTS
server within few seconds after the Happy Eyeballs mechanism is
completed, caching avoids trashing the network especially in the
presence of DDoS attack traffic.
o If DOTS signal channel session is established with TLS (but DTLS
failed), the DOTS client periodically repeats the mechanism to
discover whether DOTS signal channel messages with DTLS over UDP
becomes available from the DOTS server, so the DOTS client can
migrate the DOTS signal channel from TCP to UDP. Such probing
SHOULD NOT be done more frequently than every 24 hours and MUST
NOT be done more frequently than every 5 minutes.
When connection attempts are made during an attack, the DOTS client
SHOULD use a "Connection Attempt Delay" [RFC8305] set to 100 ms.
In reference to Figure 4, the DOTS client proceeds with the
connection attempts following the rules in [RFC8305]. In this
example, it is assumed that the IPv6 path is broken and UDP traffic
is dropped by a middlebox but has little impact to the DOTS client
because there is no long delay before using IPv4 and TCP.
+-----------+ +-----------+ +-----------+ +-----------+
|DOTS client| |DOTS server| |DOTS client| |DOTS server|
+-----------+ +-----------+ +-----------+ +-----------+
| | | |
|--DTLS ClientHello, IPv6 ---->X | T0 |--DTLS ClientHello, IPv6 ---->X |
|--TCP SYN, IPv6-------------->X | T1 |--DTLS ClientHello, IPv4 ---->X |
|--DTLS ClientHello, IPv4 ---->X | T2 |--TCP SYN, IPv6-------------->X |
|--TCP SYN, IPv4--------------------------------------->| T3 |--TCP SYN, IPv4--------------------------------------->|
|--DTLS ClientHello, IPv6 ---->X |
|--TCP SYN, IPv6-------------->X |
|<-TCP SYNACK-------------------------------------------| |<-TCP SYNACK-------------------------------------------|
|--DTLS ClientHello, IPv4 ---->X |
|--TCP ACK--------------------------------------------->| |--TCP ACK--------------------------------------------->|
|<------------Establish TLS Session-------------------->| |<------------Establish TLS Session-------------------->|
|----------------DOTS signal--------------------------->| |----------------DOTS signal--------------------------->|
| | | |
Note:
* Retransmission messages are not shown.
* T1-T0=T2-T1=T3-T2= Connection Attempt Delay.
Figure 4: DOTS Happy Eyeballs (Sample Flow) Figure 4: DOTS Happy Eyeballs (Sample Flow)
A single DOTS signal channel between DOTS agents can be used to
exchange multiple DOTS signal messages. To reduce DOTS client and
DOTS server workload, DOTS clients SHOULD re-use the (D)TLS session.
4.4. DOTS Mitigation Methods 4.4. DOTS Mitigation Methods
The following methods are used by a DOTS client to request, withdraw, The following methods are used by a DOTS client to request, withdraw,
or retrieve the status of mitigation requests: or retrieve the status of mitigation requests:
PUT: DOTS clients use the PUT method to request mitigation from a PUT: DOTS clients use the PUT method to request mitigation from a
DOTS server (Section 4.4.1). During active mitigation, DOTS DOTS server (Section 4.4.1). During active mitigation, DOTS
clients may use PUT requests to carry mitigation efficacy clients may use PUT requests to carry mitigation efficacy
updates to the DOTS server (Section 4.4.3). updates to the DOTS server (Section 4.4.3).
GET: DOTS clients may use the GET method to subscribe to DOTS GET: DOTS clients may use the GET method to subscribe to DOTS
server status messages, or to retrieve the list of its server status messages, or to retrieve the list of its
mitigations maintained by a DOTS server (Section 4.4.2). mitigations maintained by a DOTS server (Section 4.4.2).
DELETE: DOTS clients use the DELETE method to withdraw a request for DELETE: DOTS clients use the DELETE method to withdraw a request for
mitigation from a DOTS server (Section 4.4.4). mitigation from a DOTS server (Section 4.4.4).
Mitigation request and response messages are marked as Non- Mitigation request and response messages are marked as Non-
confirmable messages (Section 2.2 of [RFC7252]). confirmable messages (Section 2.2 of [RFC7252]).
DOTS agents SHOULD follow the data transmission guidelines discussed DOTS agents MUST follow the data transmission guidelines discussed in
in Section 3.1.3 of [RFC8085] and control transmission behavior by Section 3.1.3 of [RFC8085] and control transmission behavior by not
not sending more than one UDP datagram per round-trip time (RTT) to sending more than one UDP datagram per round-trip time (RTT) to the
the peer DOTS agent on average. peer DOTS agent on average.
Requests marked by the DOTS client as Non-confirmable messages are Requests marked by the DOTS client as Non-confirmable messages are
sent at regular intervals until a response is received from the DOTS sent at regular intervals until a response is received from the DOTS
server. If the DOTS client cannot maintain an RTT estimate, it server. If the DOTS client cannot maintain an RTT estimate, it MUST
SHOULD NOT send more than one Non-confirmable request every 3 NOT send more than one Non-confirmable request every 3 seconds, and
seconds, and SHOULD use an even less aggressive rate whenever SHOULD use an even less aggressive rate whenever possible (case 2 in
possible (case 2 in Section 3.1.3 of [RFC8085]). Section 3.1.3 of [RFC8085]).
JSON diagnostic notation is used to illustrate the various methods JSON encoding is used to illustrate the various methods defined in
defined in the following sub-sections. Also, the examples use the the following sub-sections. Also, the examples use the Labels
Labels defined in Sections 9.6.2, 9.6.3, 9.6.4, and 9.6.5. defined in Sections 9.6.2, 9.6.3, 9.6.4, and 9.6.5.
4.4.1. Request Mitigation 4.4.1. Request Mitigation
When a DOTS client requires mitigation for some reason, the DOTS When a DOTS client requires mitigation for some reason, the DOTS
client uses the CoAP PUT method to send a mitigation request to its client uses the CoAP PUT method to send a mitigation request to its
DOTS server(s) (Figures 5 and 6). DOTS server(s) (Figures 5 and 6).
If a DOTS client is entitled to solicit the DOTS service, the DOTS If a DOTS client is entitled to solicit the DOTS service, the DOTS
server enables mitigation on behalf of the DOTS client by server enables mitigation on behalf of the DOTS client by
communicating the DOTS client's request to a mitigator (which may be communicating the DOTS client's request to a mitigator (which may be
colocated with the DOTS server) and relaying the feedback of the co-located with the DOTS server) and relaying the feedback of the
thus-selected mitigator to the requesting DOTS client. thus-selected mitigator to the requesting DOTS client.
Header: PUT (Code=0.03) Header: PUT (Code=0.03)
Uri-Path: ".well-known" Uri-Path: ".well-known"
Uri-Path: "dots" Uri-Path: "dots"
Uri-Path: "mitigate" Uri-Path: "mitigate"
Uri-Path: "cuid=dz6pHjaADkaFTbjr0JGBpw" Uri-Path: "cuid=dz6pHjaADkaFTbjr0JGBpw"
Uri-Path: "mid=123" Uri-Path: "mid=123"
Content-Format: "application/dots+cbor" Content-Format: "application/dots+cbor"
{ {
... ...
} }
Figure 5: PUT to Convey DOTS Mitigation Requests Figure 5: PUT to Convey DOTS Mitigation Requests
The order of the Uri-Path options is important as it defines the CoAP The order of the Uri-Path options is important as it defines the CoAP
resource. In particular, 'mid' MUST follow 'cuid'. resource. In particular, 'mid' MUST follow 'cuid'.
The additional Uri-Path parameters to those defined in Section 4.2 The additional Uri-Path parameters to those defined in Section 4.2
are as follows: are as follows:
cuid: Stands for Client Unique Identifier. A globally unique cuid: Stands for Client Unique Identifier. A globally unique
identifier that is meant to prevent collisions among DOTS clients, identifier that is meant to prevent collisions among DOTS clients,
especially those from the same domain. It MUST be generated by especially those from the same domain. It MUST be generated by
DOTS clients. DOTS clients.
Implementations SHOULD set 'cuid' to the output of a cryptographic For the reasons discussed in Appendix A, implementations SHOULD
hash algorithm whose input is the Distinguished Encoding Rules set 'cuid' to the output of a cryptographic hash algorithm whose
(DER)-encoded Abstract Syntax Notation One (ASN.1) representation input is the Distinguished Encoding Rules (DER)-encoded Abstract
of the Subject Public Key Info (SPKI) of the DOTS client X.509 Syntax Notation One (ASN.1) representation of the Subject Public
certificate [RFC5280], the DOTS client raw public key [RFC7250], Key Info (SPKI) of the DOTS client X.509 certificate [RFC5280],
or the "Pre-Shared Key (PSK) identity" used by the DOTS client in the DOTS client raw public key [RFC7250], or the "Pre-Shared Key
the TLS ClientKeyExchange message. In this version of the (PSK) identity" used by the DOTS client in the TLS
specification, the cryptographic hash algorithm used is SHA-256 ClientKeyExchange message. In this version of the specification,
[RFC6234]. The output of the cryptographic hash algorithm is the cryptographic hash algorithm used is SHA-256 [RFC6234]. The
truncated to 16 bytes; truncation is done by stripping off the output of the cryptographic hash algorithm is truncated to 16
final 16 bytes. The truncated output is base64url encoded. bytes; truncation is done by stripping off the final 16 bytes.
The truncated output is base64url encoded (Section 5 of [RFC4648])
with the trailing "=" removed from the encoding.
The 'cuid' is intended to be stable when communicating with a The 'cuid' is intended to be stable when communicating with a
given DOTS server, i.e., the 'cuid' used by a DOTS client SHOULD given DOTS server, i.e., the 'cuid' used by a DOTS client SHOULD
NOT change over time. Distinct 'cuid' values MAY be used by a NOT change over time. Distinct 'cuid' values MAY be used by a
single DOTS client per DOTS server. single DOTS client per DOTS server.
If a DOTS client has to change its 'cuid' for some reason, it MUST If a DOTS client has to change its 'cuid' for some reason, it MUST
NOT do so when mitigations are still active for the old 'cuid'. NOT do so when mitigations are still active for the old 'cuid'.
The 'cuid' SHOULD be 22 characters to avoid DOTS signal message The 'cuid' SHOULD be 22 characters to avoid DOTS signal message
fragmentation over UDP. Furthermore, if that DOTS client created fragmentation over UDP. Furthermore, if that DOTS client created
skipping to change at page 14, line 22 skipping to change at page 15, line 19
3221225471) and no attack is detected, the DOTS client MUST reset 3221225471) and no attack is detected, the DOTS client MUST reset
'mid' to 0 to handle 'mid' rollover. If the DOTS client maintains 'mid' to 0 to handle 'mid' rollover. If the DOTS client maintains
mitigation requests with pre-configured scopes, it MUST re-create mitigation requests with pre-configured scopes, it MUST re-create
them with the 'mid' restarting at 0. them with the 'mid' restarting at 0.
This identifier MUST be generated by the DOTS client. This identifier MUST be generated by the DOTS client.
This is a mandatory Uri-Path parameter. This is a mandatory Uri-Path parameter.
'cuid' and 'mid' MUST NOT appear in the PUT request message body 'cuid' and 'mid' MUST NOT appear in the PUT request message body
(Figure 6). (Figure 6). The schema in Figure 6 uses the types defined in
Section 6. Note that this figure (and other similar figures
depicting a schema) are non-normative sketches of the structure of
the message.
Content-Format: "application/dots+cbor"
{ {
"ietf-dots-signal-channel:mitigation-scope": { "ietf-dots-signal-channel:mitigation-scope": {
"scope": [ "scope": [
{ {
"target-prefix": [ "target-prefix": [
"string" "string"
], ],
"target-port-range": [ "target-port-range": [
{ {
"lower-port": number, "lower-port": number,
skipping to change at page 15, line 48 skipping to change at page 16, line 47
Figure 6: PUT to Convey DOTS Mitigation Requests (Message Body Figure 6: PUT to Convey DOTS Mitigation Requests (Message Body
Schema) Schema)
The parameters in the CBOR body (Figure 6) of the PUT request are The parameters in the CBOR body (Figure 6) of the PUT request are
described below: described below:
target-prefix: A list of prefixes identifying resources under target-prefix: A list of prefixes identifying resources under
attack. Prefixes are represented using Classless Inter-Domain attack. Prefixes are represented using Classless Inter-Domain
Routing (CIDR) notation [RFC4632]. Routing (CIDR) notation [RFC4632].
As a reminder, the prefix length must be less than or equal to 32 As a reminder, the prefix length must be less than or equal to 32
(resp. 128) for IPv4 (resp. IPv6). (or 128) for IPv4 (or IPv6).
The prefix list MUST NOT include broadcast, loopback, or multicast The prefix list MUST NOT include broadcast, loopback, or multicast
addresses. These addresses are considered as invalid values. In addresses. These addresses are considered as invalid values. In
addition, the DOTS server MUST validate that target prefixes are addition, the DOTS server MUST validate that target prefixes are
within the scope of the DOTS client domain. Other validation within the scope of the DOTS client domain. Other validation
checks may be supported by DOTS servers. checks may be supported by DOTS servers.
This is an optional attribute. This is an optional attribute.
target-port-range: A list of port numbers bound to resources under target-port-range: A list of port numbers bound to resources under
skipping to change at page 18, line 13 skipping to change at page 19, line 13
lost. lost.
The default value of the parameter is 'true' (that is, the The default value of the parameter is 'true' (that is, the
mitigation starts immediately). If 'trigger-mitigation' is not mitigation starts immediately). If 'trigger-mitigation' is not
present in a request, this is equivalent to receiving a request present in a request, this is equivalent to receiving a request
with 'trigger-mitigation' set to 'true'. with 'trigger-mitigation' set to 'true'.
This is an optional attribute. This is an optional attribute.
In deployments where server-domain DOTS gateways are enabled, In deployments where server-domain DOTS gateways are enabled,
identity information about the origin source client domain SHOULD be identity information about the origin source client domain ('cdid')
propagated to the DOTS server. That information is meant to assist SHOULD be propagated to the DOTS server. That information is meant
the DOTS server to enforce some policies such as grouping DOTS to assist the DOTS server to enforce some policies such as grouping
clients that belong to the same DOTS domain, limiting the number of DOTS clients that belong to the same DOTS domain, limiting the number
DOTS requests, and identifying the mitigation scope. These policies of DOTS requests, and identifying the mitigation scope. These
can be enforced per-client, per-client domain, or both. Also, the policies can be enforced per-client, per-client domain, or both.
identity information may be used for auditing and debugging purposes. Also, the identity information may be used for auditing and debugging
purposes.
Figure 7 shows an example of a request relayed by a server-domain Figure 7 shows an example of a request relayed by a server-domain
DOTS gateway. DOTS gateway.
Header: PUT (Code=0.03) Header: PUT (Code=0.03)
Uri-Path: ".well-known" Uri-Path: ".well-known"
Uri-Path: "dots" Uri-Path: "dots"
Uri-Path: "mitigate" Uri-Path: "mitigate"
Uri-Path: "cdid=7eeaf349529eb55ed50113" Uri-Path: "cdid=7eeaf349529eb55ed50113"
Uri-Path: "cuid=dz6pHjaADkaFTbjr0JGBpw" Uri-Path: "cuid=dz6pHjaADkaFTbjr0JGBpw"
skipping to change at page 20, line 7 skipping to change at page 21, line 9
[I-D.ietf-core-hop-limit]. [I-D.ietf-core-hop-limit].
Because of the complexity to handle partial failure cases, this Because of the complexity to handle partial failure cases, this
specification does not allow for including multiple mitigation specification does not allow for including multiple mitigation
requests in the same PUT request. Concretely, a DOTS client MUST NOT requests in the same PUT request. Concretely, a DOTS client MUST NOT
include multiple entries in the 'scope' array of the same PUT include multiple entries in the 'scope' array of the same PUT
request. request.
FQDN and URI mitigation scopes may be thought of as a form of scope FQDN and URI mitigation scopes may be thought of as a form of scope
alias, in which the addresses associated with the domain name or URI alias, in which the addresses associated with the domain name or URI
(as resolved by the DOTS server) represent the full scope of the (as resolved by the DOTS server) represent the scope of the
mitigation. mitigation. Particularly, the IP addresses to which the host
subcomponent of authority component of an URI resolves represent the
'target-prefix', the URI scheme represents the 'target-protocol', the
port subcomponent of authority component of an URI represents the
'target-port-range'. If the optional port information is not present
in the authority component, the default port defined for the URI
scheme represents the 'target-port'.
In the PUT request at least one of the attributes 'target-prefix', In the PUT request at least one of the attributes 'target-prefix',
'target-fqdn','target-uri', or 'alias-name' MUST be present. 'target-fqdn','target-uri', or 'alias-name' MUST be present.
Attributes and Uri-Path parameters with empty values MUST NOT be Attributes and Uri-Path parameters with empty values MUST NOT be
present in a request and render the entire request invalid. present in a request and render the entire request invalid.
Figure 8 shows a PUT request example to signal that TCP port numbers Figure 8 shows a PUT request example to signal that TCP port numbers
80, 8080, and 443 used by 2001:db8:6401::1 and 2001:db8:6401::2 80, 8080, and 443 used by 2001:db8:6401::1 and 2001:db8:6401::2
servers are under attack (illustrated in JSON diagnostic notation). servers are under attack. The presence of 'cdid' indicates that a
The presence of 'cdid' indicates that a server-domain DOTS gateway server-domain DOTS gateway has modified the initial PUT request sent
has modified the initial PUT request sent by the DOTS client. Note by the DOTS client. Note that 'cdid' MUST NOT appear in the PUT
that 'cdid' MUST NOT appear in the PUT request message body. request message body.
Header: PUT (Code=0.03) Header: PUT (Code=0.03)
Uri-Path: ".well-known" Uri-Path: ".well-known"
Uri-Path: "dots" Uri-Path: "dots"
Uri-Path: "mitigate" Uri-Path: "mitigate"
Uri-Path: "cdid=7eeaf349529eb55ed50113" Uri-Path: "cdid=7eeaf349529eb55ed50113"
Uri-Path: "cuid=dz6pHjaADkaFTbjr0JGBpw" Uri-Path: "cuid=dz6pHjaADkaFTbjr0JGBpw"
Uri-Path: "mid=123" Uri-Path: "mid=123"
Content-Format: "application/dots+cbor" Content-Format: "application/dots+cbor"
{ {
"ietf-dots-signal-channel:mitigation-scope": { "ietf-dots-signal-channel:mitigation-scope": {
"scope": [ "scope": [
{ {
"target-prefix": [ "target-prefix": [
"2001:db8:6401::1/128", "2001:db8:6401::1/128",
"2001:db8:6401::2/128" "2001:db8:6401::2/128"
], ],
"target-port-range": [ "target-port-range": [
{ {
skipping to change at page 23, line 41 skipping to change at page 24, line 41
] ]
} }
} }
Figure 10: 2.xx Response Body Figure 10: 2.xx Response Body
If the request is missing a mandatory attribute, does not include If the request is missing a mandatory attribute, does not include
'cuid' or 'mid' Uri-Path options, includes multiple 'scope' 'cuid' or 'mid' Uri-Path options, includes multiple 'scope'
parameters, or contains invalid or unknown parameters, the DOTS parameters, or contains invalid or unknown parameters, the DOTS
server MUST reply with 4.00 (Bad Request). DOTS agents can safely server MUST reply with 4.00 (Bad Request). DOTS agents can safely
ignore comprehension-optional parameters they don't understand. ignore comprehension-optional parameters they don't understand
(Section 9.6.1.1).
A DOTS server that receives a mitigation request with a lifetime set A DOTS server that receives a mitigation request with a lifetime set
to '0' MUST reply with a 4.00 (Bad Request). to '0' MUST reply with a 4.00 (Bad Request).
If the DOTS server does not find the 'mid' parameter value conveyed If the DOTS server does not find the 'mid' parameter value conveyed
in the PUT request in its configuration data, it MAY accept the in the PUT request in its configuration data, it MAY accept the
mitigation request by sending back a 2.01 (Created) response to the mitigation request by sending back a 2.01 (Created) response to the
DOTS client; the DOTS server will consequently try to mitigate the DOTS client; the DOTS server will consequently try to mitigate the
attack. A DOTS server could reject mitigation requests when it is attack. A DOTS server could reject mitigation requests when it is
near capacity or needs to rate-limit a particular client, for near capacity or needs to rate-limit a particular client, for
example. example.
If the DOTS server finds the 'mid' parameter value conveyed in the
PUT request in its configuration data bound to that DOTS client, it
MAY update the mitigation request, and a 2.04 (Changed) response is
returned to indicate a successful update of the mitigation request.
The relative order of two mitigation requests, having the same The relative order of two mitigation requests, having the same
'trigger-mitigation' type, from a DOTS client is determined by 'trigger-mitigation' type, from a DOTS client is determined by
comparing their respective 'mid' values. If two mitigation requests comparing their respective 'mid' values. If two mitigation requests
with the same 'trigger-mitigation' type have overlapping mitigation with the same 'trigger-mitigation' type have overlapping mitigation
scopes, the mitigation request with the highest numeric 'mid' value scopes, the mitigation request with the highest numeric 'mid' value
will override the other mitigation request. Two mitigation requests will override the other mitigation request. Two mitigation requests
from a DOTS client have overlapping scopes if there is a common IP from a DOTS client have overlapping scopes if there is a common IP
address, IP prefix, FQDN, URI, or alias-name. To avoid maintaining a address, IP prefix, FQDN, URI, or alias-name. To avoid maintaining a
long list of overlapping mitigation requests (i.e., requests with the long list of overlapping mitigation requests (i.e., requests with the
same 'trigger-mitigation' type and overlapping scopes) from a DOTS same 'trigger-mitigation' type and overlapping scopes) from a DOTS
skipping to change at page 24, line 50 skipping to change at page 25, line 45
1: Overlapping targets. 'conflict-scope' provides more details 1: Overlapping targets. 'conflict-scope' provides more details
about the conflicting target clauses. about the conflicting target clauses.
conflict-scope: Characterizes the exact conflict scope. It may conflict-scope: Characterizes the exact conflict scope. It may
include a list of IP addresses, a list of prefixes, a list of include a list of IP addresses, a list of prefixes, a list of
port numbers, a list of target protocols, a list of FQDNs, a port numbers, a list of target protocols, a list of FQDNs, a
list of URIs, a list of alias-names, or a 'mid'. list of URIs, a list of alias-names, or a 'mid'.
If the DOTS server receives a mitigation request which overlaps with If the DOTS server receives a mitigation request which overlaps with
an active mitigation request, but both having distinct 'trigger- an active mitigation request, but both having distinct 'trigger-
mitigation' types, the DOTS server MUST deactivate (absent explicit mitigation' types, the DOTS server SHOULD deactivate (absent explicit
policy/configuration otherwise) the mitigation request with 'trigger- policy/configuration otherwise) the mitigation request with 'trigger-
mitigation' set to false. Particularly, if the mitigation request mitigation' set to false. Particularly, if the mitigation request
with 'trigger-mitigation' set to false is active, the DOTS server with 'trigger-mitigation' set to false is active, the DOTS server
withdraws the mitigation request (i.e., status code is set to '7' as withdraws the mitigation request (i.e., status code is set to '7' as
defined in Table 2) and transitions the status of the mitigation defined in Table 2) and transitions the status of the mitigation
request to '8'. request to '8'.
Upon DOTS signal channel session loss with a peer DOTS client, the Upon DOTS signal channel session loss with a peer DOTS client, the
DOTS server MUST withdraw (absent explicit policy/configuration DOTS server MUST withdraw (absent explicit policy/configuration
otherwise) any active mitigation requests overlapping with mitigation otherwise) any active mitigation requests overlapping with mitigation
skipping to change at page 26, line 49 skipping to change at page 27, line 45
retry-timer: Indicates, in seconds, the time after which the DOTS retry-timer: Indicates, in seconds, the time after which the DOTS
client may re-issue the same request. The DOTS server returns client may re-issue the same request. The DOTS server returns
'retry-timer' only to DOTS client(s) for which a mitigation 'retry-timer' only to DOTS client(s) for which a mitigation
request is deactivated. Any retransmission of the same request is deactivated. Any retransmission of the same
mitigation request before the expiry of this timer is likely to mitigation request before the expiry of this timer is likely to
be rejected by the DOTS server for the same reasons. be rejected by the DOTS server for the same reasons.
The retry-timer SHOULD be equal to the lifetime of the active The retry-timer SHOULD be equal to the lifetime of the active
mitigation request resulting in the deactivation of the mitigation request resulting in the deactivation of the
conflicting mitigation request. The lifetime of the conflicting mitigation request.
deactivated mitigation request will be updated to (retry-timer
+ 45 seconds), so the DOTS client can refresh the deactivated If the DOTS server decides to maintain a state for the
mitigation request after retry-timer seconds before expiry of deactivated mitigation request, the DOTS server updates the
lifetime and check if the conflict is resolved. lifetime of the deactivated mitigation request to (retry-timer
+ 45 seconds), so that the DOTS client can refresh the
deactivated mitigation request after 'retry-timer' seconds, but
before the expiry of the lifetime, and check if the conflict is
resolved.
Header: PUT (Code=0.03) Header: PUT (Code=0.03)
Uri-Path: ".well-known" Uri-Path: ".well-known"
Uri-Path: "dots" Uri-Path: "dots"
Uri-Path: "mitigate" Uri-Path: "mitigate"
Uri-Path: "cuid=7eeaf349529eb55ed50113" Uri-Path: "cuid=7eeaf349529eb55ed50113"
Uri-Path: "mid=12" Uri-Path: "mid=12"
(1) Request with a conflicting 'cuid' (1) Request with a conflicting 'cuid'
{
"ietf-dots-signal-channel:mitigation-scope": {
"scope": [
{
"conflict-information": {
"conflict-cause": "cuid-collision"
}
}
]
}
}
(2) Message body of the 4.09 (Conflict) response
from the DOTS server
Header: PUT (Code=0.03) Header: PUT (Code=0.03)
Uri-Path: ".well-known" Uri-Path: ".well-known"
Uri-Path: "dots" Uri-Path: "dots"
Uri-Path: "mitigate" Uri-Path: "mitigate"
Uri-Path: "cuid=f30d281ce6b64fc5a0b91e" Uri-Path: "cuid=f30d281ce6b64fc5a0b91e"
Uri-Path: "mid=12" Uri-Path: "mid=12"
(2) Request with a new 'cuid' (3) Request with a new 'cuid'
Figure 11: Example of Generating a New 'cuid' Figure 11: Example of Generating a New 'cuid'
As an active attack evolves, DOTS clients can adjust the scope of As an active attack evolves, DOTS clients can adjust the scope of
requested mitigation as necessary, by refining the scope of resources requested mitigation as necessary, by refining the scope of resources
requiring mitigation. This can be achieved by sending a PUT request requiring mitigation. This can be achieved by sending a PUT request
with a new 'mid' value that will override the existing one with with a new 'mid' value that will override the existing one with
overlapping mitigation scopes. overlapping mitigation scopes.
For a mitigation request to continue beyond the initial negotiated For a mitigation request to continue beyond the initial negotiated
lifetime, the DOTS client has to refresh the current mitigation lifetime, the DOTS client has to refresh the current mitigation
request by sending a new PUT request. This PUT request MUST use the request by sending a new PUT request. This PUT request MUST use the
same 'mid' value, and MUST repeat all the other parameters as sent in same 'mid' value, and MUST repeat all the other parameters as sent in
the original mitigation request apart from a possible change to the the original mitigation request apart from a possible change to the
lifetime parameter value. lifetime parameter value. In such case, the DOTS server MAY update
the mitigation request, and a 2.04 (Changed) response is returned to
indicate a successful update of the mitigation request. If this is
not the case, the DOTS server MUST reject the request with a 4.00
(Bad Request).
4.4.2. Retrieve Information Related to a Mitigation 4.4.2. Retrieve Information Related to a Mitigation
A GET request is used by a DOTS client to retrieve information A GET request is used by a DOTS client to retrieve information
(including status) of DOTS mitigations from a DOTS server. (including status) of DOTS mitigations from a DOTS server.
'cuid' is a mandatory Uri-Path parameter for GET requests. 'cuid' is a mandatory Uri-Path parameter for GET requests.
Uri-Path parameters with empty values MUST NOT be present in a Uri-Path parameters with empty values MUST NOT be present in a
request. request.
The same considerations for manipulating 'cdid' parameter by server- The same considerations for manipulating 'cdid' parameter by server-
domain DOTS gateways specified in Section 4.4.1 MUST be followed for domain DOTS gateways specified in Section 4.4.1 MUST be followed for
GET requests. GET requests.
The 'c' (content) parameter and its permitted values defined in The 'c' Uri-Query option is used to control selection of
[I-D.ietf-core-comi] can be used to retrieve non-configuration data configuration and non-configuration data nodes. Concretely, the 'c'
(attack mitigation status), configuration data, or both. The DOTS (content) parameter and its permitted values defined in the following
server MAY support this optional filtering capability. It can safely table [I-D.ietf-core-comi] can be used to retrieve non-configuration
ignore it if not supported. If the DOTS client supports the optional data (attack mitigation status), configuration data, or both. The
filtering capability, it SHOULD use "c=n" query (to get back only the DOTS server MAY support this optional filtering capability. It can
dynamically changing data) or "c=c" query (to get back the static safely ignore it if not supported. If the DOTS client supports the
configuration values) when the DDoS attack is active to limit the optional filtering capability, it SHOULD use "c=n" query (to get back
size of the response. only the dynamically changing data) or "c=c" query (to get back the
static configuration values) when the DDoS attack is active to limit
the size of the response.
+-------+-----------------------------------------------------+
| Value | Description |
+-------+-----------------------------------------------------+
| c | Return only configuration descendant data nodes |
| n | Return only non-configuration descendant data nodes |
| a | Return all descendant data nodes |
+-------+-----------------------------------------------------+
The DOTS client can use Block-wise transfer [RFC7959] to get the list The DOTS client can use Block-wise transfer [RFC7959] to get the list
of all its mitigations maintained by a DOTS server, it can send of all its mitigations maintained by a DOTS server, it can send
Block2 Option in a GET request with NUM = 0 to aid in limiting the Block2 Option in a GET request with NUM = 0 to aid in limiting the
size of the response. If the representation of all the active size of the response. If the representation of all the active
mitigation requests associated with the DOTS client does not fit mitigation requests associated with the DOTS client does not fit
within a single datagram, the DOTS server MUST use the Block2 Option within a single datagram, the DOTS server MUST use the Block2 Option
with NUM = 0 in the GET response. The Size2 Option may be conveyed with NUM = 0 in the GET response. The Size2 Option may be conveyed
in the response to indicate the total size of the resource in the response to indicate the total size of the resource
representation. The DOTS client retrieves the rest of the representation. The DOTS client retrieves the rest of the
skipping to change at page 31, line 30 skipping to change at page 33, line 30
This is a mandatory attribute. This is a mandatory attribute.
bytes-dropped: The total dropped byte count for the mitigation bytes-dropped: The total dropped byte count for the mitigation
request since the attack mitigation is triggered. The count wraps request since the attack mitigation is triggered. The count wraps
around when it reaches the maximum value of unsigned integer64. around when it reaches the maximum value of unsigned integer64.
This is an optional attribute. This is an optional attribute.
bps-dropped: The average number of dropped bytes per second for the bps-dropped: The average number of dropped bytes per second for the
mitigation request since the attack mitigation is triggered. This mitigation request since the attack mitigation is triggered. This
average SHOULD be over five-minute intervals. average SHOULD be over five-minute intervals (that is, measuring
bytes into five-minute buckets and then averaging these buckets
over the time since the mitigation was triggered).
This is an optional attribute. This is an optional attribute.
pkts-dropped: The total number of dropped packet count for the pkts-dropped: The total number of dropped packet count for the
mitigation request since the attack mitigation is triggered. The mitigation request since the attack mitigation is triggered. The
count wraps around when it reaches the maximum value of unsigned count wraps around when it reaches the maximum value of unsigned
integer64. integer64.
This is an optional attribute. This is an optional attribute.
pps-dropped: The average number of dropped packets per second for pps-dropped: The average number of dropped packets per second for
the mitigation request since the attack mitigation is triggered. the mitigation request since the attack mitigation is triggered.
This average SHOULD be over five-minute intervals. This average SHOULD be over five-minute intervals (that is,
measuring packets into five-minute buckets and then averaging
these buckets over the time since the mitigation was triggered).
This is an optional attribute. This is an optional attribute.
+-----------+-------------------------------------------------------+ +-----------+-------------------------------------------------------+
| Parameter | Description | | Parameter | Description |
| Value | | | Value | |
+-----------+-------------------------------------------------------+ +-----------+-------------------------------------------------------+
| 1 | Attack mitigation setup is in progress (e.g., | | 1 | Attack mitigation setup is in progress (e.g., |
| | changing the network path to redirect the inbound | | | changing the network path to redirect the inbound |
| | traffic to a DOTS mitigator). | | | traffic to a DOTS mitigator). |
skipping to change at page 33, line 17 skipping to change at page 35, line 17
'config' (Section 4.2). 'config' (Section 4.2).
A DOTS client conveys the Observe Option set to '0' in the GET A DOTS client conveys the Observe Option set to '0' in the GET
request to receive asynchronous notifications of attack mitigation request to receive asynchronous notifications of attack mitigation
status from the DOTS server. status from the DOTS server.
Unidirectional mitigation notifications within the bidirectional Unidirectional mitigation notifications within the bidirectional
signal channel enables asynchronous notifications between the agents. signal channel enables asynchronous notifications between the agents.
[RFC7641] indicates that (1) a notification can be sent in a [RFC7641] indicates that (1) a notification can be sent in a
Confirmable or a Non-confirmable message, and (2) the message type Confirmable or a Non-confirmable message, and (2) the message type
used is typically application dependent and may be determined by the used is typically application-dependent and may be determined by the
server for each notification individually. For DOTS server server for each notification individually. For DOTS server
application, the message type MUST always be set to Non-confirmable application, the message type MUST always be set to Non-confirmable
even if the underlying COAP library elects a notification to be sent even if the underlying COAP library elects a notification to be sent
in a Confirmable message. in a Confirmable message.
Due to the higher likelihood of packet loss during a DDoS attack, the Due to the higher likelihood of packet loss during a DDoS attack, the
DOTS server periodically sends attack mitigation status to the DOTS DOTS server periodically sends attack mitigation status to the DOTS
client and also notifies the DOTS client whenever the status of the client and also notifies the DOTS client whenever the status of the
attack mitigation changes. If the DOTS server cannot maintain an RTT attack mitigation changes. If the DOTS server cannot maintain an RTT
estimate, it SHOULD NOT send more than one asynchronous notification estimate, it MUST NOT send more than one asynchronous notification
every 3 seconds, and SHOULD use an even less aggressive rate whenever every 3 seconds, and SHOULD use an even less aggressive rate whenever
possible (case 2 in Section 3.1.3 of [RFC8085]). possible (case 2 in Section 3.1.3 of [RFC8085]).
When conflicting requests are detected, the DOTS server enforces the When conflicting requests are detected, the DOTS server enforces the
corresponding policy (e.g., accept all requests, reject all requests, corresponding policy (e.g., accept all requests, reject all requests,
accept only one request but reject all the others, ...). It is accept only one request but reject all the others, ...). It is
assumed that this policy is supplied by the DOTS server administrator assumed that this policy is supplied by the DOTS server administrator
or it is a default behavior of the DOTS server implementation. Then, or it is a default behavior of the DOTS server implementation. Then,
the DOTS server sends notification message(s) to the DOTS client(s) the DOTS server sends notification message(s) to the DOTS client(s)
at the origin of the conflict (refer to the conflict parameters at the origin of the conflict (refer to the conflict parameters
skipping to change at page 35, line 41 skipping to change at page 37, line 41
| | | |
... ...
Figure 15: Notifications of Attack Mitigation Status Figure 15: Notifications of Attack Mitigation Status
4.4.2.2. DOTS Clients Polling for Mitigation Status 4.4.2.2. DOTS Clients Polling for Mitigation Status
The DOTS client can send the GET request at frequent intervals The DOTS client can send the GET request at frequent intervals
without the Observe Option to retrieve the configuration data of the without the Observe Option to retrieve the configuration data of the
mitigation request and non-configuration data (i.e., the attack mitigation request and non-configuration data (i.e., the attack
status). The frequency of polling the DOTS server to get the status). DOTS clients MAY be configured with a policy indicating the
mitigation status SHOULD follow the transmission guidelines in frequency of polling DOTS servers to get the mitigation status.
Absent such policy, the frequency of polling the DOTS server to get
the mitigation status SHOULD follow the transmission guidelines in
Section 3.1.3 of [RFC8085]. Section 3.1.3 of [RFC8085].
If the DOTS server has been able to mitigate the attack and the If the DOTS server has been able to mitigate the attack and the
attack has stopped, the DOTS server indicates as such in the status. attack has stopped, the DOTS server indicates as such in the status.
In such case, the DOTS client recalls the mitigation request by In such case, the DOTS client recalls the mitigation request by
issuing a DELETE request for this mitigation request (Section 4.4.4). issuing a DELETE request for this mitigation request (Section 4.4.4).
A DOTS client SHOULD react to the status of the attack as per the A DOTS client SHOULD react to the status of the attack as per the
information sent by the DOTS server rather than performing its own information sent by the DOTS server rather than performing its own
detection that the attack has been mitigated. This ensures that the detection that the attack has been mitigated. This ensures that the
skipping to change at page 37, line 11 skipping to change at page 39, line 11
An example of an efficacy update message, which includes an If-Match An example of an efficacy update message, which includes an If-Match
Option with an empty value, is depicted in Figure 16. Option with an empty value, is depicted in Figure 16.
Header: PUT (Code=0.03) Header: PUT (Code=0.03)
Uri-Path: ".well-known" Uri-Path: ".well-known"
Uri-Path: "dots" Uri-Path: "dots"
Uri-Path: "mitigate" Uri-Path: "mitigate"
Uri-Path: "cuid=dz6pHjaADkaFTbjr0JGBpw" Uri-Path: "cuid=dz6pHjaADkaFTbjr0JGBpw"
Uri-Path: "mid=123" Uri-Path: "mid=123"
Content-Format: "application/dots+cbor"
If-Match: If-Match:
Content-Format: "application/dots+cbor"
{ {
"ietf-dots-signal-channel:mitigation-scope": { "ietf-dots-signal-channel:mitigation-scope": {
"scope": [ "scope": [
{ {
"target-prefix": [ "target-prefix": [
"2001:db8:6401::1/128", "2001:db8:6401::1/128",
"2001:db8:6401::2/128" "2001:db8:6401::2/128"
], ],
"target-port-range": [ "target-port-range": [
{ {
skipping to change at page 39, line 32 skipping to change at page 41, line 32
The initial active-but-terminating period SHOULD be sufficiently long The initial active-but-terminating period SHOULD be sufficiently long
to absorb latency incurred by route propagation. The active-but- to absorb latency incurred by route propagation. The active-but-
terminating period SHOULD be set by default to 120 seconds. If the terminating period SHOULD be set by default to 120 seconds. If the
client requests mitigation again before the initial active-but- client requests mitigation again before the initial active-but-
terminating period elapses, the DOTS server MAY exponentially terminating period elapses, the DOTS server MAY exponentially
increase (the base of the exponent is 2) the active-but-terminating increase (the base of the exponent is 2) the active-but-terminating
period up to a maximum of 300 seconds (5 minutes). period up to a maximum of 300 seconds (5 minutes).
Once the active-but-terminating period elapses, the DOTS server MUST Once the active-but-terminating period elapses, the DOTS server MUST
treat the mitigation as terminated, as the DOTS client is no longer treat the mitigation as terminated, as the DOTS client is no longer
responsible for the mitigation. For example, if there is a financial responsible for the mitigation.
relationship between the DOTS client and server domains, the DOTS
client stops incurring cost at this point.
If a mitigation is triggered due to a signal channel loss, the DOTS If a mitigation is triggered due to a signal channel loss, the DOTS
server relies upon normal triggers to stop that mitigation server relies upon normal triggers to stop that mitigation
(typically, receipt of a valid DELETE request, expiry of the (typically, receipt of a valid DELETE request, expiry of the
mitigation lifetime, or scrubbing the traffic to the attack target). mitigation lifetime, or scrubbing the traffic to the attack target).
In particular, the DOTS server MUST NOT consider the signal channel In particular, the DOTS server MUST NOT consider the signal channel
recovery as a trigger to stop the mitigation. recovery as a trigger to stop the mitigation.
4.5. DOTS Signal Channel Session Configuration 4.5. DOTS Signal Channel Session Configuration
A DOTS client can negotiate, configure, and retrieve the DOTS signal A DOTS client can negotiate, configure, and retrieve the DOTS signal
channel session behavior with its DOTS peers. The DOTS signal channel session behavior with its DOTS peers. The DOTS signal
channel can be used, for example, to configure the following: channel can be used, for example, to configure the following:
a. Heartbeat interval (heartbeat-interval): DOTS agents regularly a. Heartbeat interval (heartbeat-interval): DOTS agents regularly
send heartbeats (CoAP Ping/Pong) to each other after mutual send heartbeats to each other after mutual authentication is
authentication is successfully completed in order to keep the successfully completed in order to keep the DOTS signal channel
DOTS signal channel open. Heartbeat messages are exchanged open. Heartbeat messages are exchanged between DOTS agents every
between DOTS agents every 'heartbeat-interval' seconds to detect 'heartbeat-interval' seconds to detect the current status of the
the current status of the DOTS signal channel session. DOTS signal channel session.
b. Missing heartbeats allowed (missing-hb-allowed): This variable b. Missing heartbeats allowed (missing-hb-allowed): This variable
indicates the maximum number of consecutive heartbeat messages indicates the maximum number of consecutive heartbeat messages
for which a DOTS agent did not receive a response before for which a DOTS agent did not receive a response before
concluding that the session is disconnected or defunct. concluding that the session is disconnected or defunct.
c. Acceptable signal loss ratio: Maximum retransmissions, c. Acceptable signal loss ratio: Maximum retransmissions,
retransmission timeout value, and other message transmission retransmission timeout value, and other message transmission
parameters for the DOTS signal channel. parameters for the DOTS signal channel.
skipping to change at page 41, line 38 skipping to change at page 43, line 35
Uri-Path: ".well-known" Uri-Path: ".well-known"
Uri-Path: "dots" Uri-Path: "dots"
Uri-Path: "config" Uri-Path: "config"
Figure 18: GET to Retrieve Configuration Figure 18: GET to Retrieve Configuration
The DOTS server in the 2.05 (Content) response conveys the current, The DOTS server in the 2.05 (Content) response conveys the current,
minimum, and maximum attribute values acceptable by the DOTS server minimum, and maximum attribute values acceptable by the DOTS server
(Figure 19). (Figure 19).
Content-Format: "application/dots+cbor"
{ {
"ietf-dots-signal-channel:signal-config": { "ietf-dots-signal-channel:signal-config": {
"mitigating-config": { "mitigating-config": {
"heartbeat-interval": { "heartbeat-interval": {
"max-value": number, "max-value": number,
"min-value": number, "min-value": number,
"current-value": number "current-value": number
}, },
"missing-hb-allowed": { "missing-hb-allowed": {
"max-value": number, "max-value": number,
skipping to change at page 43, line 47 skipping to change at page 45, line 44
idle-config: Set of configuration parameters to use when no idle-config: Set of configuration parameters to use when no
mitigation is active. This attribute has the same structure as mitigation is active. This attribute has the same structure as
'mitigating-config'. 'mitigating-config'.
Figure 20 shows an example of acceptable and current configuration Figure 20 shows an example of acceptable and current configuration
parameters on a DOTS server for DOTS signal channel session parameters on a DOTS server for DOTS signal channel session
configuration. The same acceptable configuration is used during configuration. The same acceptable configuration is used during
mitigation and idle times. mitigation and idle times.
Content-Format: "application/dots+cbor"
{ {
"ietf-dots-signal-channel:signal-config": { "ietf-dots-signal-channel:signal-config": {
"mitigating-config": { "mitigating-config": {
"heartbeat-interval": { "heartbeat-interval": {
"max-value": 240, "max-value": 240,
"min-value": 15, "min-value": 15,
"current-value": 30 "current-value": 30
}, },
"missing-hb-allowed": { "missing-hb-allowed": {
"max-value": 9, "max-value": 9,
skipping to change at page 45, line 33 skipping to change at page 47, line 30
Note: heartbeat-interval should be tweaked to also assist DOTS Note: heartbeat-interval should be tweaked to also assist DOTS
messages for NAT traversal (SIG-011 of messages for NAT traversal (SIG-011 of
[I-D.ietf-dots-requirements]). According to [RFC8085], keepalive [I-D.ietf-dots-requirements]). According to [RFC8085], keepalive
messages must not be sent more frequently than once every 15 messages must not be sent more frequently than once every 15
seconds and should use longer intervals when possible. seconds and should use longer intervals when possible.
Furthermore, [RFC4787] recommends NATs to use a state timeout of 2 Furthermore, [RFC4787] recommends NATs to use a state timeout of 2
minutes or longer, but experience shows that sending packets every minutes or longer, but experience shows that sending packets every
15 to 30 seconds is necessary to prevent the majority of 15 to 30 seconds is necessary to prevent the majority of
middleboxes from losing state for UDP flows. From that middleboxes from losing state for UDP flows. From that
standpoint, this specification recommends a minimum heartbeat- standpoint, the RECOMMENDED minimum heartbeat-interval is 15
interval of 15 seconds and a maximum heartbeat-interval of 240 seconds and the RECOMMENDED maximum heartbeat-interval is 240
seconds. The recommended value of 30 seconds is selected to seconds. The recommended value of 30 seconds is selected to
anticipate the expiry of NAT state. anticipate the expiry of NAT state.
A heartbeat-interval of 30 seconds may be considered as too chatty A heartbeat-interval of 30 seconds may be considered as too chatty
in some deployments. For such deployments, DOTS agents may in some deployments. For such deployments, DOTS agents may
negotiate longer heartbeat-interval values to prevent any network negotiate longer heartbeat-interval values to prevent any network
overload with too frequent keepalives. overload with too frequent keepalives.
Different heartbeat intervals can be defined for 'mitigating- Different heartbeat intervals can be defined for 'mitigating-
config' and 'idle-config' to reduce being too chatty during idle config' and 'idle-config' to reduce being too chatty during idle
times. If there is an on-path translator between the DOTS client times. If there is an on-path translator between the DOTS client
(standalone or part of a DOTS gateway) and the DOTS server, the (standalone or part of a DOTS gateway) and the DOTS server, the
'mitigating-config' heartbeat-interval has to be smaller than the 'mitigating-config' heartbeat-interval has to be smaller than the
translator session timeout. It is recommended that the 'idle- translator session timeout. It is recommended that the 'idle-
config' heartbeat-interval is also smaller than the translator config' heartbeat-interval is also smaller than the translator
session timeout to prevent translator traversal issues, or session timeout to prevent translator traversal issues, or
disabled entirely. Means to discover the lifetime assigned by a disabled entirely. Means to discover the lifetime assigned by a
translator are out of scope. translator are out of scope.
Section 4.2 of [RFC7252] defines a "CoAP Ping" mechanism.
Concretely, the DOTS agent sends an Empty Confirmable message and the
peer DOTS agent will respond by sending a Reset message.
When a Confirmable "CoAP Ping" is sent, and if there is no response, When a Confirmable "CoAP Ping" is sent, and if there is no response,
the "CoAP Ping" is retransmitted max-retransmit number of times by the "CoAP Ping" is retransmitted max-retransmit number of times by
the CoAP layer using an initial timeout set to a random duration the CoAP layer using an initial timeout set to a random duration
between ack-timeout and (ack-timeout*ack-random-factor) and between ack-timeout and (ack-timeout*ack-random-factor) and
exponential back-off between retransmissions. By choosing the exponential back-off between retransmissions. By choosing the
recommended transmission parameters, the "CoAP Ping" will timeout recommended transmission parameters, the "CoAP Ping" will timeout
after 45 seconds. If the DOTS agent does not receive any response after 45 seconds. If the DOTS agent does not receive any response
from the peer DOTS agent for 'missing-hb-allowed' number of from the peer DOTS agent for 'missing-hb-allowed' number of
consecutive "CoAP Ping" Confirmable messages, it concludes that the consecutive "CoAP Ping" Confirmable messages, it concludes that the
DOTS signal channel session is disconnected. A DOTS client MUST NOT DOTS signal channel session is disconnected. A DOTS client MUST NOT
skipping to change at page 46, line 36 skipping to change at page 48, line 38
The signal channel session configuration is applicable to a single The signal channel session configuration is applicable to a single
DOTS signal channel session between DOTS agents, so the 'cuid' Uri- DOTS signal channel session between DOTS agents, so the 'cuid' Uri-
Path MUST NOT be used. Path MUST NOT be used.
Header: PUT (Code=0.03) Header: PUT (Code=0.03)
Uri-Path: ".well-known" Uri-Path: ".well-known"
Uri-Path: "dots" Uri-Path: "dots"
Uri-Path: "config" Uri-Path: "config"
Uri-Path: "sid=123" Uri-Path: "sid=123"
Content-Format: "application/dots+cbor" Content-Format: "application/dots+cbor"
{ {
... ...
} }
Figure 21: PUT to Convey the DOTS Signal Channel Session Figure 21: PUT to Convey the DOTS Signal Channel Session
Configuration Data Configuration Data
The additional Uri-Path parameter to those defined in Table 1 is as The additional Uri-Path parameter to those defined in Table 1 is as
follows: follows:
sid: Session Identifier is an identifier for the DOTS signal channel sid: Session Identifier is an identifier for the DOTS signal channel
session configuration data represented as an integer. This session configuration data represented as an integer. This
identifier MUST be generated by DOTS clients. 'sid' values MUST identifier MUST be generated by DOTS clients. 'sid' values MUST
increase monotonically (when a new PUT is generated by a DOTS increase monotonically (when a new PUT is generated by a DOTS
client to convey the configuration parameters for the signal client to convey the configuration parameters for the signal
channel). channel).
This is a mandatory attribute. This is a mandatory attribute.
Content-Format: "application/dots+cbor"
{ {
"ietf-dots-signal-channel:signal-config": { "ietf-dots-signal-channel:signal-config": {
"mitigating-config": { "mitigating-config": {
"heartbeat-interval": { "heartbeat-interval": {
"current-value": number "current-value": number
}, },
"missing-hb-allowed": { "missing-hb-allowed": {
"current-value": number "current-value": number
}, },
"max-retransmit": { "max-retransmit": {
skipping to change at page 54, line 4 skipping to change at page 55, line 52
information. The DOTS client can then try to establish a UDP or a information. The DOTS client can then try to establish a UDP or a
TCP session with the alternate DOTS server. The DOTS client MAY TCP session with the alternate DOTS server. The DOTS client MAY
implement a method to construct IPv4-embedded IPv6 addresses implement a method to construct IPv4-embedded IPv6 addresses
[RFC6052]; this is required to handle the scenario where an IPv6-only [RFC6052]; this is required to handle the scenario where an IPv6-only
DOTS client communicates with an IPv4-only alternate DOTS server. DOTS client communicates with an IPv4-only alternate DOTS server.
If the DOTS client has been redirected to a DOTS server to which it If the DOTS client has been redirected to a DOTS server to which it
has already communicated with within the last five (5) minutes, it has already communicated with within the last five (5) minutes, it
MUST ignore the redirection and try to contact other DOTS servers MUST ignore the redirection and try to contact other DOTS servers
listed in the local configuration or discovered using dynamic means listed in the local configuration or discovered using dynamic means
such as DHCP or SRV procedures. It is RECOMMENDED that DOTS clients such as DHCP or SRV procedures [I-D.ietf-dots-server-discovery]. It
support means to alert administrators about redirect loops. is RECOMMENDED that DOTS clients support means to alert
administrators about redirect loops.
4.7. Heartbeat Mechanism 4.7. Heartbeat Mechanism
To provide an indication of signal health and distinguish an 'idle' To provide an indication of signal health and distinguish an 'idle'
signal channel from a 'disconnected' or 'defunct' session, the DOTS signal channel from a 'disconnected' or 'defunct' session, the DOTS
agent sends a heartbeat over the signal channel to maintain its half agent sends a heartbeat over the signal channel to maintain its half
of the channel. The DOTS agent similarly expects a heartbeat from of the channel. The DOTS agent similarly expects a heartbeat from
its peer DOTS agent, and may consider a session terminated in the its peer DOTS agent, and may consider a session terminated in the
prolonged absence of a peer agent heartbeat. Concretely, while the prolonged absence of a peer agent heartbeat. Concretely, while the
communication between the DOTS agents is otherwise quiescent, the communication between the DOTS agents is otherwise quiescent, the
skipping to change at page 55, line 18 skipping to change at page 57, line 18
resumption or if (D)TLS session resumption is successful then resumption or if (D)TLS session resumption is successful then
disconnect the current DOTS signal channel session. disconnect the current DOTS signal channel session.
o If the DOTS server does not receive any traffic from the peer DOTS o If the DOTS server does not receive any traffic from the peer DOTS
client, then the DOTS server sends heartbeat requests to the DOTS client, then the DOTS server sends heartbeat requests to the DOTS
client and after maximum 'missing-hb-allowed' threshold is client and after maximum 'missing-hb-allowed' threshold is
reached, the DOTS server concludes the session is disconnected. reached, the DOTS server concludes the session is disconnected.
In DOTS over UDP, heartbeat messages MUST be exchanged between the In DOTS over UDP, heartbeat messages MUST be exchanged between the
DOTS agents using the "CoAP Ping" mechanism defined in Section 4.2 of DOTS agents using the "CoAP Ping" mechanism defined in Section 4.2 of
[RFC7252]. Concretely, the DOTS agent sends an Empty Confirmable [RFC7252].
message and the peer DOTS agent will respond by sending a Reset
message.
In DOTS over TCP, heartbeat messages MUST be exchanged between the In DOTS over TCP, heartbeat messages MUST be exchanged between the
DOTS agents using the Ping and Pong messages specified in Section 5.4 DOTS agents using the Ping and Pong messages specified in Section 5.4
of [RFC8323]. That is, the DOTS agent sends a Ping message and the of [RFC8323]. That is, the DOTS agent sends a Ping message and the
peer DOTS agent would respond by sending a single Pong message. peer DOTS agent would respond by sending a single Pong message.
5. DOTS Signal Channel YANG Modules 5. DOTS Signal Channel YANG Modules
This document defines a YANG [RFC7950] module for DOTS mitigation This document defines a YANG [RFC7950] module for DOTS mitigation
scope, DOTS signal channel session configuration data, and DOTS scope, DOTS signal channel session configuration data, and DOTS
redirection signalling. redirection signaling.
This YANG module (ietf-dots-signal-channel) defines the DOTS client This YANG module (ietf-dots-signal-channel) defines the DOTS client
interaction with the DOTS server as seen by the DOTS client. A DOTS interaction with the DOTS server as seen by the DOTS client. A DOTS
server is allowed to update the non-configurable 'ro' entities in the server is allowed to update the non-configurable 'ro' entities in the
responses. This YANG module is not intended to be used via NETCONF/ responses. This YANG module is not intended to be used via NETCONF/
RESTCONF for DOTS server management purposes; such module is out of RESTCONF for DOTS server management purposes; such module is out of
the scope of this document. It serves only to provide a data model the scope of this document. It serves only to provide a data model
and encoding, but not a management data model. and encoding, but not a management data model.
A companion YANG module is defined to include a collection of types A companion YANG module is defined to include a collection of types
defined by IANA: "iana-dots-signal-channel" (Section 5.2). defined by IANA: "iana-dots-signal-channel" (Section 5.2).
5.1. Tree Structure 5.1. Tree Structure
This document defines the YANG module "ietf-dots-signal-channel" This document defines the YANG module "ietf-dots-signal-channel"
(Section 5.3), which has the following tree structure. A DOTS signal (Section 5.3), which has the following tree structure. A DOTS signal
message can either be a mitigation or a configuration message. message can be a mitigation, a configuration, or a redirect message.
module: ietf-dots-signal-channel module: ietf-dots-signal-channel
+--rw dots-signal +--rw dots-signal
+--rw (message-type)? +--rw (message-type)?
+--:(mitigation-scope) +--:(mitigation-scope)
| +--rw scope* [cuid mid] | +--rw scope* [cuid mid]
| +--rw cdid? string | +--rw cdid? string
| +--rw cuid string | +--rw cuid string
| +--rw mid uint32 | +--rw mid uint32
| +--rw target-prefix* inet:ip-prefix | +--rw target-prefix* inet:ip-prefix
skipping to change at page 56, line 43 skipping to change at page 58, line 41
| | +--ro alias-name* string | | +--ro alias-name* string
| | +--ro acl-list* [acl-name] | | +--ro acl-list* [acl-name]
| | | +--ro acl-name | | | +--ro acl-name
| | | | -> /ietf-data:dots-data/dots-client/acls/ | | | | -> /ietf-data:dots-data/dots-client/acls/
| | | | acl/name | | | | acl/name
| | | +--ro acl-type? | | | +--ro acl-type?
| | | -> /ietf-data:dots-data/dots-client/acls/ | | | -> /ietf-data:dots-data/dots-client/acls/
| | | acl/type | | | acl/type
| | +--ro mid? -> ../../../mid | | +--ro mid? -> ../../../mid
| +--ro bytes-dropped? yang:zero-based-counter64 | +--ro bytes-dropped? yang:zero-based-counter64
| +--ro bps-dropped? yang:zero-based-counter64 | +--ro bps-dropped? yang:gauge64
| +--ro pkts-dropped? yang:zero-based-counter64 | +--ro pkts-dropped? yang:zero-based-counter64
| +--ro pps-dropped? yang:zero-based-counter64 | +--ro pps-dropped? yang:gauge64
| +--rw attack-status? iana-signal:attack-status | +--rw attack-status? iana-signal:attack-status
+--:(signal-config) +--:(signal-config)
| +--rw sid uint32 | +--rw sid uint32
| +--rw mitigating-config | +--rw mitigating-config
| | +--rw heartbeat-interval | | +--rw heartbeat-interval
| | | +--ro max-value? uint16 | | | +--ro max-value? uint16
| | | +--ro min-value? uint16 | | | +--ro min-value? uint16
| | | +--rw current-value? uint16 | | | +--rw current-value? uint16
| | +--rw missing-hb-allowed | | +--rw missing-hb-allowed
| | | +--ro max-value? uint16 | | | +--ro max-value? uint16
skipping to change at page 66, line 35 skipping to change at page 68, line 33
type yang:zero-based-counter64; type yang:zero-based-counter64;
units "bytes"; units "bytes";
config false; config false;
description description
"The total dropped byte count for the mitigation "The total dropped byte count for the mitigation
request since the attack mitigation is triggered. request since the attack mitigation is triggered.
The count wraps around when it reaches the maximum value The count wraps around when it reaches the maximum value
of counter64 for dropped bytes."; of counter64 for dropped bytes.";
} }
leaf bps-dropped { leaf bps-dropped {
type yang:zero-based-counter64; type yang:gauge64;
config false; config false;
description description
"The average number of dropped bits per second for "The average number of dropped bits per second for
the mitigation request since the attack the mitigation request since the attack
mitigation is triggered. This should be a mitigation is triggered. This should be over
five-minute average."; five-minute intervals (that is, measuring bytes
into five-minute buckets and then averaging these
buckets over the time since the mitigation was
triggered).";
} }
leaf pkts-dropped { leaf pkts-dropped {
type yang:zero-based-counter64; type yang:zero-based-counter64;
config false; config false;
description description
"The total number of dropped packet count for the "The total number of dropped packet count for the
mitigation request since the attack mitigation is mitigation request since the attack mitigation is
triggered. The count wraps around when it reaches triggered. The count wraps around when it reaches
the maximum value of counter64 for dropped packets."; the maximum value of counter64 for dropped packets.";
} }
leaf pps-dropped { leaf pps-dropped {
type yang:zero-based-counter64; type yang:gauge64;
config false; config false;
description description
"The average number of dropped packets per second "The average number of dropped packets per second
for the mitigation request since the attack for the mitigation request since the attack
mitigation is triggered. This should be a mitigation is triggered. This should be over
five-minute average."; five-minute intervals (that is, measuring packets
into five-minute buckets and then averaging these
buckets over the time since the mitigation was
triggered).";
} }
leaf attack-status { leaf attack-status {
type iana-signal:attack-status; type iana-signal:attack-status;
description description
"Indicates the status of an attack as seen by the "Indicates the status of an attack as seen by the
DOTS client."; DOTS client.";
} }
} }
} }
skipping to change at page 71, line 50 skipping to change at page 74, line 9
} }
} }
} }
} }
<CODE ENDS> <CODE ENDS>
6. YANG/JSON Mapping Parameters to CBOR 6. YANG/JSON Mapping Parameters to CBOR
All parameters in the payload of the DOTS signal channel MUST be All parameters in the payload of the DOTS signal channel MUST be
mapped to CBOR types as shown in Table 4 and are assigned an integer mapped to CBOR types as shown in Table 4 and are assigned an integer
key to save space. The CBOR key values are divided into two types: key to save space.
comprehension-required and comprehension-optional. DOTS agents can
safely ignore comprehension-optional values they don't understand, o Note: Implementers must check that the mapping output provided by
but cannot successfully process a request if it contains their YANG-to-CBOR encoding schemes is aligned with the content of
comprehension-required values that are not understood. The 4.00 Table 4.
response SHOULD include a diagnostic payload describing the unknown
comprehension-required CBOR key values. The initial set of CBOR key The CBOR key values are divided into two types: comprehension-
values defined in this specification are of type comprehension- required and comprehension-optional. DOTS agents can safely ignore
required. comprehension-optional values they don't understand, but cannot
successfully process a request if it contains comprehension-required
values that are not understood. The 4.00 response SHOULD include a
diagnostic payload describing the unknown comprehension-required CBOR
key values. The initial set of CBOR key values defined in this
specification are of type comprehension-required.
+----------------------+-------------+-----+---------------+--------+ +----------------------+-------------+-----+---------------+--------+
| Parameter Name | YANG | CBOR| CBOR Major | JSON | | Parameter Name | YANG | CBOR| CBOR Major | JSON |
| | Type | Key | Type & | Type | | | Type | Key | Type & | Type |
| | | | Information | | | | | | Information | |
+----------------------+-------------+-----+---------------+--------+ +----------------------+-------------+-----+---------------+--------+
| ietf-dots-signal-cha | | | | | | ietf-dots-signal-cha | | | | |
| nnel:mitigation-scope| container | 1 | 5 map | Object | | nnel:mitigation-scope| container | 1 | 5 map | Object |
| scope | list | 2 | 4 array | Array | | scope | list | 2 | 4 array | Array |
| cdid | string | 3 | 3 text string | String | | cdid | string | 3 | 3 text string | String |
skipping to change at page 73, line 7 skipping to change at page 75, line 18
| conflict-status | enumeration | 18 | 0 unsigned | String | | conflict-status | enumeration | 18 | 0 unsigned | String |
| conflict-cause | enumeration | 19 | 0 unsigned | String | | conflict-cause | enumeration | 19 | 0 unsigned | String |
| retry-timer | uint32 | 20 | 0 unsigned | Number | | retry-timer | uint32 | 20 | 0 unsigned | Number |
| conflict-scope | container | 21 | 5 map | Object | | conflict-scope | container | 21 | 5 map | Object |
| acl-list | list | 22 | 4 array | Array | | acl-list | list | 22 | 4 array | Array |
| acl-name | leafref | 23 | 3 text string | String | | acl-name | leafref | 23 | 3 text string | String |
| acl-type | leafref | 24 | 3 text string | String | | acl-type | leafref | 24 | 3 text string | String |
| bytes-dropped | yang:zero- | | | | | bytes-dropped | yang:zero- | | | |
| | based- | | | | | | based- | | | |
| | counter64 | 25 | 0 unsigned | String | | | counter64 | 25 | 0 unsigned | String |
| bps-dropped | yang:zero- | | | | | bps-dropped | yang:gauge64| 26 | 0 unsigned | String |
| | based- | | | |
| | counter64 | 26 | 0 unsigned | String |
| pkts-dropped | yang:zero- | | | | | pkts-dropped | yang:zero- | | | |
| | based- | | | | | | based- | | | |
| | counter64 | 27 | 0 unsigned | String | | | counter64 | 27 | 0 unsigned | String |
| pps-dropped | yang:zero- | | | | | pps-dropped | yang:gauge64| 28 | 0 unsigned | String |
| | based- | | | |
| | counter64 | 28 | 0 unsigned | String |
| attack-status | enumeration | 29 | 0 unsigned | String | | attack-status | enumeration | 29 | 0 unsigned | String |
| ietf-dots-signal- | | | | | | ietf-dots-signal- | | | | |
| channel:signal-config| container | 30 | 5 map | Object | | channel:signal-config| container | 30 | 5 map | Object |
| sid | uint32 | 31 | 0 unsigned | Number | | sid | uint32 | 31 | 0 unsigned | Number |
| mitigating-config | container | 32 | 5 map | Object | | mitigating-config | container | 32 | 5 map | Object |
| heartbeat-interval | container | 33 | 5 map | Object | | heartbeat-interval | container | 33 | 5 map | Object |
| max-value | uint16 | 34 | 0 unsigned | Number | | max-value | uint16 | 34 | 0 unsigned | Number |
| min-value | uint16 | 35 | 0 unsigned | Number | | min-value | uint16 | 35 | 0 unsigned | Number |
| current-value | uint16 | 36 | 0 unsigned | Number | | current-value | uint16 | 36 | 0 unsigned | Number |
| missing-hb-allowed | container | 37 | 5 map | Object | | missing-hb-allowed | container | 37 | 5 map | Object |
skipping to change at page 74, line 26 skipping to change at page 76, line 28
MUST adhere to the (D)TLS implementation recommendations and security MUST adhere to the (D)TLS implementation recommendations and security
considerations of [RFC7525] except with respect to (D)TLS version. considerations of [RFC7525] except with respect to (D)TLS version.
Since DOTS signal channel encryption relying upon (D)TLS is virtually Since DOTS signal channel encryption relying upon (D)TLS is virtually
a green-field deployment, DOTS agents MUST implement only (D)TLS 1.2 a green-field deployment, DOTS agents MUST implement only (D)TLS 1.2
or later. or later.
When a DOTS client is configured with a domain name of the DOTS When a DOTS client is configured with a domain name of the DOTS
server, and connects to its configured DOTS server, the server may server, and connects to its configured DOTS server, the server may
present it with a PKIX certificate. In order to ensure proper present it with a PKIX certificate. In order to ensure proper
authentication, a DOTS client MUST verify the entire certification authentication, a DOTS client MUST verify the entire certification
path per [RFC5280]. The DOTS client additionally uses [RFC6125] path per [RFC5280]. Additionally, the DOTS client MUST use [RFC6125]
validation techniques to compare the domain name with the certificate validation techniques to compare the domain name with the certificate
provided. provided. Certification authorities that issue DOTS server
certificates SHOULD support the DNS-ID and SRV-ID identifier types.
DOTS server SHOULD prefer the use of DNS-ID and SRV-ID over CN-ID
identifier types in certificate requests (as described in Section 2.3
of [RFC6125]) and the wildcard character '*' SHOULD NOT be included
in the presented identifier. DOTS doesn't use URI-IDs for server
identity verification.
A key challenge to deploying DOTS is the provisioning of DOTS A key challenge to deploying DOTS is the provisioning of DOTS
clients, including the distribution of keying material to DOTS clients, including the distribution of keying material to DOTS
clients to enable the required mutual authentication of DOTS agents. clients to enable the required mutual authentication of DOTS agents.
Enrollment over Secure Transport (EST) [RFC7030] defines a method of Enrollment over Secure Transport (EST) [RFC7030] defines a method of
certificate enrollment by which domains operating DOTS servers may certificate enrollment by which domains operating DOTS servers may
provide DOTS clients with all the necessary cryptographic keying provide DOTS clients with all the necessary cryptographic keying
material, including a private key and a certificate to authenticate material, including a private key and a certificate to authenticate
themselves. One deployment option is DOTS clients behave as EST themselves. One deployment option is DOTS clients behave as EST
clients for certificate enrollment from an EST server provisioned by clients for certificate enrollment from an EST server provisioned by
skipping to change at page 77, line 29 skipping to change at page 79, line 39
() Indicates messages protected 0-RTT keys () Indicates messages protected 0-RTT keys
{} Indicates messages protected using handshake keys {} Indicates messages protected using handshake keys
[] Indicates messages protected using 1-RTT keys [] Indicates messages protected using 1-RTT keys
Figure 27: A Simplified TLS 1.3 Handshake with 0-RTT Figure 27: A Simplified TLS 1.3 Handshake with 0-RTT
7.3. DTLS MTU and Fragmentation 7.3. DTLS MTU and Fragmentation
To avoid DOTS signal message fragmentation and the subsequent To avoid DOTS signal message fragmentation and the subsequent
decreased probability of message delivery, DOTS agents MUST ensure decreased probability of message delivery, DOTS agents MUST ensure
that the DTLS record MUST fit within a single datagram. If the path that the DTLS record fit within a single datagram. If the PMTU
MTU is not known to the DOTS server, an IP MTU of 1280 bytes SHOULD cannot be discovered, DOTS agents MUST assume a PMTU of 1280 bytes,
be assumed. The DOTS client must consider the amount of record as IPv6 requires that every link in the Internet have an MTU of 1280
expansion expected by the DTLS processing when calculating the size octets or greater as specified in [RFC8200]. If IPv4 support on
of CoAP message that fits within the path MTU. Path MTU MUST be legacy or otherwise unusual networks is a consideration and the PMTU
greater than or equal to [CoAP message size + DTLS 1.2 overhead of 13 is unknown, DOTS implementations MAY assume on a PMTU of 576 bytes
octets + authentication overhead of the negotiated DTLS cipher suite for IPv4 datagrams, as every IPv4 host must be capable of receiving a
+ block padding] (Section 4.1.1.1 of [RFC6347]). If the total packet whose length is equal to 576 bytes as discussed in [RFC0791]
request size exceeds the path MTU then the DOTS client MUST split the and [RFC1122].
DOTS signal into separate messages; for example, the list of
addresses in the 'target-prefix' parameter could be split into The DOTS client must consider the amount of record expansion expected
multiple lists and each list conveyed in a new PUT request. by the DTLS processing when calculating the size of CoAP message that
fits within the path MTU. Path MTU MUST be greater than or equal to
[CoAP message size + DTLS 1.2 overhead of 13 octets + authentication
overhead of the negotiated DTLS cipher suite + block padding]
(Section 4.1.1.1 of [RFC6347]). If the total request size exceeds
the path MTU then the DOTS client MUST split the DOTS signal into
separate messages; for example, the list of addresses in the 'target-
prefix' parameter could be split into multiple lists and each list
conveyed in a new PUT request.
Implementation Note: DOTS choice of message size parameters works Implementation Note: DOTS choice of message size parameters works
well with IPv6 and with most of today's IPv4 paths. However, with well with IPv6 and with most of today's IPv4 paths. However, with
IPv4, it is harder to safely make sure that there is no IP IPv4, it is harder to safely make sure that there is no IP
fragmentation. If the IPv4 path MTU is unknown, implementations may fragmentation. If the IPv4 path MTU is unknown, implementations may
want to limit themselves to more conservative IPv4 datagram sizes want to limit themselves to more conservative IPv4 datagram sizes
such as 576 bytes, as per [RFC0791]. IP packets whose size does not such as 576 bytes, as per [RFC0791].
exceed 576 bytes should never need to be fragmented: therefore,
sending a maximum of 500 bytes of DOTS signal over a UDP datagram
will generally avoid IP fragmentation.
8. Mutual Authentication of DOTS Agents & Authorization of DOTS Clients 8. Mutual Authentication of DOTS Agents & Authorization of DOTS Clients
(D)TLS based upon client certificate can be used for mutual (D)TLS based upon client certificate can be used for mutual
authentication between DOTS agents. If, for example, a DOTS gateway authentication between DOTS agents. If, for example, a DOTS gateway
is involved, DOTS clients and DOTS gateways must perform mutual is involved, DOTS clients and DOTS gateways must perform mutual
authentication; only authorized DOTS clients are allowed to send DOTS authentication; only authorized DOTS clients are allowed to send DOTS
signals to a DOTS gateway. The DOTS gateway and the DOTS server must signals to a DOTS gateway. The DOTS gateway and the DOTS server must
perform mutual authentication; a DOTS server only allows DOTS signal perform mutual authentication; a DOTS server only allows DOTS signal
channel messages from an authorized DOTS gateway, thereby creating a channel messages from an authorized DOTS gateway, thereby creating a
skipping to change at page 91, line 13 skipping to change at page 93, line 13
(TLS) with a cipher suite offering confidentiality protection, and (TLS) with a cipher suite offering confidentiality protection, and
the guidance given in [RFC7525] MUST be followed to avoid attacks on the guidance given in [RFC7525] MUST be followed to avoid attacks on
(D)TLS. The (D)TLS protocol profile used for the DOTS signal channel (D)TLS. The (D)TLS protocol profile used for the DOTS signal channel
is specified in Section 7. is specified in Section 7.
If TCP is used between DOTS agents, an attacker may be able to inject If TCP is used between DOTS agents, an attacker may be able to inject
RST packets, bogus application segments, etc., regardless of whether RST packets, bogus application segments, etc., regardless of whether
TLS authentication is used. Because the application data is TLS TLS authentication is used. Because the application data is TLS
protected, this will not result in the application receiving bogus protected, this will not result in the application receiving bogus
data, but it will constitute a DoS on the connection. This attack data, but it will constitute a DoS on the connection. This attack
can be countered by using TCP-AO [RFC5925]. If TCP-AO is used, then can be countered by using TCP-AO [RFC5925]. Although not widely
any bogus packets injected by an attacker will be rejected by the adopted, if TCP-AO is used, then any bogus packets injected by an
TCP-AO integrity check and therefore will never reach the TLS layer. attacker will be rejected by the TCP-AO integrity check and therefore
will never reach the TLS layer.
An attack vector that can be achieved if the 'cuid' is guessable is a An attack vector that can be achieved if the 'cuid' is guessable is a
misbehaving DOTS client from within the client's domain which uses misbehaving DOTS client from within the client's domain which uses
the 'cuid' of another DOTS client of the domain to delete or alter the 'cuid' of another DOTS client of the domain to delete or alter
active mitigations. For this attack vector to happen, the active mitigations. For this attack vector to happen, the
misbehaving client needs to pass the security validation checks by misbehaving client needs to pass the security validation checks by
the DOTS server, and eventually the checks of a client-domain DOTS the DOTS server, and eventually the checks of a client-domain DOTS
gateway. gateway.
A similar attack can be achieved by a compromised DOTS client which A similar attack can be achieved by a compromised DOTS client which
can sniff the TLS 1.2 handshake, use the client certificate to can sniff the TLS 1.2 handshake, use the client certificate to
identify the 'cuid' used by another DOTS client. This attack is not identify the 'cuid' used by another DOTS client. This attack is not
possible if algorithms such as [RFC4122] are used to generate the possible if algorithms such as version 4 Universally Unique
'cuid'. Likewise, this attack is not possible with TLS 1.3 because IDentifiers (UUIDs) in Section 4.4 of [RFC4122] are used to generate
most of the TLS handshake is encrypted and the client certificate is the 'cuid' because such UUIDs are not a deterministic function of the
not visible to eavesdroppers. client certificate. Likewise, this attack is not possible with TLS
1.3 because most of the TLS handshake is encrypted and the client
certificate is not visible to eavesdroppers.
A compromised DOTS client can collude with a DDoS attacker to send
mitigation request for a target resource, gets the mitigation
efficacy from the DOTS server, and conveys the mitigation efficacy to
the DDoS attacker to possibly change the DDoS attack strategy.
Obviously, signaling an attack by the compromised DOTS client to the
DOTS server will trigger attack mitigation. This attack can be
prevented by monitoring and auditing DOTS clients to detect
misbehavior and to deter misuse, and by only authorizing the DOTS
client to request mitigation for specific target resources (e.g., an
application server is authorized to request mitigation for its IP
addresses but a DDoS mitigator can request mitigation for any target
resource in the network). Furthermore, DOTS clients are typically
co-located on network security services (e.g., firewall) and a
compromised security service potentially can do a lot more damage to
the network.
Rate-limiting DOTS requests, including those with new 'cuid' values, Rate-limiting DOTS requests, including those with new 'cuid' values,
from the same DOTS client defends against DoS attacks that would from the same DOTS client defends against DoS attacks that would
result in varying the 'cuid' to exhaust DOTS server resources. Rate- result in varying the 'cuid' to exhaust DOTS server resources. Rate-
limit policies SHOULD be enforced on DOTS gateways (if deployed) and limit policies SHOULD be enforced on DOTS gateways (if deployed) and
DOTS servers. DOTS servers.
In order to prevent leaking internal information outside a client- In order to prevent leaking internal information outside a client-
domain, DOTS gateways located in the client-domain SHOULD NOT reveal domain, DOTS gateways located in the client-domain SHOULD NOT reveal
the identification information that pertains to internal DOTS clients the identification information that pertains to internal DOTS clients
skipping to change at page 92, line 10 skipping to change at page 94, line 29
resources that belong to the DOTS client' domain MUST be authorized resources that belong to the DOTS client' domain MUST be authorized
by a DOTS server. The exact mechanism for the DOTS servers to by a DOTS server. The exact mechanism for the DOTS servers to
validate that the target prefixes are within the scope of the DOTS validate that the target prefixes are within the scope of the DOTS
client domain is deployment-specific. client domain is deployment-specific.
The presence of DOTS gateways may lead to infinite forwarding loops, The presence of DOTS gateways may lead to infinite forwarding loops,
which is undesirable. To prevent and detect such loops, this which is undesirable. To prevent and detect such loops, this
document uses the Hop-Limit Option. document uses the Hop-Limit Option.
When FQDNs are used as targets, the DOTS server MUST rely upon DNS When FQDNs are used as targets, the DOTS server MUST rely upon DNS
privacy enabling protocols (e.g., DNS over TLS [RFC7858], DoH privacy enabling protocols (e.g., DNS over TLS [RFC7858] or DoH
[RFC8484]) to prevent eavesdroppers from possibly identifying the [RFC8484]) to prevent eavesdroppers from possibly identifying the
target resources protected by the DDoS mitigation service and means target resources protected by the DDoS mitigation service, and means
to ensure the target FQDN resolution is authentic (e.g., DNSSEC to ensure the target FQDN resolution is authentic (e.g., DNSSEC
[RFC4034]). [RFC4034]).
CoAP-specific security considerations are discussed in Section 11 of CoAP-specific security considerations are discussed in Section 11 of
[RFC7252], while CBOR-related security considerations are discussed [RFC7252], while CBOR-related security considerations are discussed
in Section 8 of [RFC7049]. in Section 8 of [RFC7049].
11. Contributors 11. Contributors
The following individuals have contributed to this document: The following individuals have contributed to this document:
skipping to change at page 92, line 36 skipping to change at page 95, line 7
o Mike Geller, Cisco Systems, Inc. 3250 Florida 33309 USA, Email: o Mike Geller, Cisco Systems, Inc. 3250 Florida 33309 USA, Email:
mgeller@cisco.com mgeller@cisco.com
o Robert Moskowitz, HTT Consulting Oak Park, MI 42837 United States, o Robert Moskowitz, HTT Consulting Oak Park, MI 42837 United States,
Email: rgm@htt-consult.com Email: rgm@htt-consult.com
o Dan Wing, Email: dwing-ietf@fuggles.com o Dan Wing, Email: dwing-ietf@fuggles.com
12. Acknowledgements 12. Acknowledgements
Thanks to Christian Jacquenet, Roland Dobbins, Roman D. Danyliw, Thanks to Christian Jacquenet, Roland Dobbins, Roman Danyliw, Michael
Michael Richardson, Ehud Doron, Kaname Nishizuka, Dave Dolson, Liang Richardson, Ehud Doron, Kaname Nishizuka, Dave Dolson, Liang Xia,
Xia, Gilbert Clark, Xialiang Frank, Jim Schaad, Klaus Hartke, Gilbert Clark, Xialiang Frank, Jim Schaad, Klaus Hartke, Nesredien
Nesredien Suleiman, and Stephen Farrell for the discussion and Suleiman, Stephen Farrell, and Yoshifumi Nishida for the discussion
comments. and comments.
The authors would like to give special thanks to Kaname Nishizuka and The authors would like to give special thanks to Kaname Nishizuka and
Jon Shallow for their efforts in implementing the protocol and Jon Shallow for their efforts in implementing the protocol and
performing interop testing at IETF Hackathons. performing interop testing at IETF Hackathons.
Thanks to the core WG for the recommendations on Hop-Limit and Thanks to the core WG for the recommendations on Hop-Limit and
redirect signaling. redirect signaling.
Special thanks to Benjamin Kaduk for the detailed AD review. Special thanks to Benjamin Kaduk for the detailed AD review.
Thanks to Alexey Melnikov, Adam Roach, Suresh Krishnan, Mirja
Kuehlewind, and Alissa Cooper for the review.
13. References 13. References
13.1. Normative References 13.1. Normative References
[I-D.ietf-core-hop-limit]
Boucadair, M., K, R., and J. Shallow, "Constrained
Application Protocol (CoAP) Hop Limit Option", draft-ietf-
core-hop-limit-03 (work in progress), February 2019.
[RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791,
DOI 10.17487/RFC0791, September 1981,
<https://www.rfc-editor.org/info/rfc791>.
[RFC1122] Braden, R., Ed., "Requirements for Internet Hosts -
Communication Layers", STD 3, RFC 1122,
DOI 10.17487/RFC1122, October 1989,
<https://www.rfc-editor.org/info/rfc1122>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688, [RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
DOI 10.17487/RFC3688, January 2004, DOI 10.17487/RFC3688, January 2004,
<https://www.rfc-editor.org/info/rfc3688>. <https://www.rfc-editor.org/info/rfc3688>.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, DOI 10.17487/RFC3986, January 2005,
<https://www.rfc-editor.org/info/rfc3986>.
[RFC4279] Eronen, P., Ed. and H. Tschofenig, Ed., "Pre-Shared Key [RFC4279] Eronen, P., Ed. and H. Tschofenig, Ed., "Pre-Shared Key
Ciphersuites for Transport Layer Security (TLS)", Ciphersuites for Transport Layer Security (TLS)",
RFC 4279, DOI 10.17487/RFC4279, December 2005, RFC 4279, DOI 10.17487/RFC4279, December 2005,
<https://www.rfc-editor.org/info/rfc4279>. <https://www.rfc-editor.org/info/rfc4279>.
[RFC4632] Fuller, V. and T. Li, "Classless Inter-domain Routing [RFC4632] Fuller, V. and T. Li, "Classless Inter-domain Routing
(CIDR): The Internet Address Assignment and Aggregation (CIDR): The Internet Address Assignment and Aggregation
Plan", BCP 122, RFC 4632, DOI 10.17487/RFC4632, August Plan", BCP 122, RFC 4632, DOI 10.17487/RFC4632, August
2006, <https://www.rfc-editor.org/info/rfc4632>. 2006, <https://www.rfc-editor.org/info/rfc4632>.
[RFC4648] Josefsson, S., "The Base16, Base32, and Base64 Data
Encodings", RFC 4648, DOI 10.17487/RFC4648, October 2006,
<https://www.rfc-editor.org/info/rfc4648>.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246, (TLS) Protocol Version 1.2", RFC 5246,
DOI 10.17487/RFC5246, August 2008, DOI 10.17487/RFC5246, August 2008,
<https://www.rfc-editor.org/info/rfc5246>. <https://www.rfc-editor.org/info/rfc5246>.
[RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S., [RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
Housley, R., and W. Polk, "Internet X.509 Public Key Housley, R., and W. Polk, "Internet X.509 Public Key
Infrastructure Certificate and Certificate Revocation List Infrastructure Certificate and Certificate Revocation List
(CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008, (CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008,
<https://www.rfc-editor.org/info/rfc5280>. <https://www.rfc-editor.org/info/rfc5280>.
skipping to change at page 95, line 36 skipping to change at page 98, line 27
[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26, Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017, RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/info/rfc8126>. <https://www.rfc-editor.org/info/rfc8126>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>. May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", STD 86, RFC 8200,
DOI 10.17487/RFC8200, July 2017,
<https://www.rfc-editor.org/info/rfc8200>.
[RFC8323] Bormann, C., Lemay, S., Tschofenig, H., Hartke, K., [RFC8323] Bormann, C., Lemay, S., Tschofenig, H., Hartke, K.,
Silverajan, B., and B. Raymor, Ed., "CoAP (Constrained Silverajan, B., and B. Raymor, Ed., "CoAP (Constrained
Application Protocol) over TCP, TLS, and WebSockets", Application Protocol) over TCP, TLS, and WebSockets",
RFC 8323, DOI 10.17487/RFC8323, February 2018, RFC 8323, DOI 10.17487/RFC8323, February 2018,
<https://www.rfc-editor.org/info/rfc8323>. <https://www.rfc-editor.org/info/rfc8323>.
[RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol [RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol
Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018, Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
<https://www.rfc-editor.org/info/rfc8446>. <https://www.rfc-editor.org/info/rfc8446>.
13.2. Informative References 13.2. Informative References
[I-D.boucadair-dots-earlydata] [I-D.boucadair-dots-earlydata]
Boucadair, M. and R. K, "Using Early Data in DOTS", draft- Boucadair, M. and R. K, "Using Early Data in DOTS", draft-
boucadair-dots-earlydata-00 (work in progress), January boucadair-dots-earlydata-00 (work in progress), January
2019. 2019.
[I-D.boucadair-dots-server-discovery]
Boucadair, M., K, R., and P. Patil, "Distributed-Denial-
of-Service Open Threat Signaling (DOTS) Server Discovery",
draft-boucadair-dots-server-discovery-05 (work in
progress), October 2018.
[I-D.ietf-core-comi] [I-D.ietf-core-comi]
Veillette, M., Stok, P., Pelov, A., and A. Bierman, "CoAP Veillette, M., Stok, P., Pelov, A., and A. Bierman, "CoAP
Management Interface", draft-ietf-core-comi-04 (work in Management Interface", draft-ietf-core-comi-04 (work in
progress), November 2018. progress), November 2018.
[I-D.ietf-core-hop-limit]
Boucadair, M., K, R., and J. Shallow, "Constrained
Application Protocol (CoAP) Hop Limit Option", draft-ietf-
core-hop-limit-03 (work in progress), February 2019.
[I-D.ietf-core-yang-cbor] [I-D.ietf-core-yang-cbor]
Veillette, M., Pelov, A., Somaraju, A., Turner, R., and A. Veillette, M., Petrov, I., and A. Pelov, "CBOR Encoding of
Minaburo, "CBOR Encoding of Data Modeled with YANG", Data Modeled with YANG", draft-ietf-core-yang-cbor-10
draft-ietf-core-yang-cbor-07 (work in progress), September (work in progress), April 2019.
2018.
[I-D.ietf-dots-architecture] [I-D.ietf-dots-architecture]
Mortensen, A., Andreasen, F., K, R., Teague, N., Compton, Mortensen, A., K, R., Andreasen, F., Teague, N., and R.
R., and c. christopher_gray3@cable.comcast.com, Compton, "Distributed-Denial-of-Service Open Threat
"Distributed-Denial-of-Service Open Threat Signaling Signaling (DOTS) Architecture", draft-ietf-dots-
(DOTS) Architecture", draft-ietf-dots-architecture-12 architecture-13 (work in progress), April 2019.
(work in progress), February 2019.
[I-D.ietf-dots-data-channel] [I-D.ietf-dots-data-channel]
Boucadair, M. and R. K, "Distributed Denial-of-Service Boucadair, M. and R. K, "Distributed Denial-of-Service
Open Threat Signaling (DOTS) Data Channel Specification", Open Threat Signaling (DOTS) Data Channel Specification",
draft-ietf-dots-data-channel-27 (work in progress), draft-ietf-dots-data-channel-28 (work in progress), March
February 2019. 2019.
[I-D.ietf-dots-multihoming]
Boucadair, M. and R. K, "Multi-homing Deployment
Considerations for Distributed-Denial-of-Service Open
Threat Signaling (DOTS)", draft-ietf-dots-multihoming-01
(work in progress), January 2019.
[I-D.ietf-dots-requirements] [I-D.ietf-dots-requirements]
Mortensen, A., K, R., and R. Moskowitz, "Distributed Mortensen, A., K, R., and R. Moskowitz, "Distributed
Denial of Service (DDoS) Open Threat Signaling Denial of Service (DDoS) Open Threat Signaling
Requirements", draft-ietf-dots-requirements-22 (work in Requirements", draft-ietf-dots-requirements-22 (work in
progress), March 2019. progress), March 2019.
[I-D.ietf-dots-server-discovery]
Boucadair, M., K, R., and P. Patil, "Distributed-Denial-
of-Service Open Threat Signaling (DOTS) Server Discovery",
draft-ietf-dots-server-discovery-02 (work in progress),
May 2019.
[I-D.ietf-dots-use-cases] [I-D.ietf-dots-use-cases]
Dobbins, R., Migault, D., Fouant, S., Moskowitz, R., Dobbins, R., Migault, D., Fouant, S., Moskowitz, R.,
Teague, N., Xia, L., and K. Nishizuka, "Use cases for DDoS Teague, N., Xia, L., and K. Nishizuka, "Use cases for DDoS
Open Threat Signaling", draft-ietf-dots-use-cases-17 (work Open Threat Signaling", draft-ietf-dots-use-cases-17 (work
in progress), January 2019. in progress), January 2019.
[I-D.ietf-tls-dtls13] [I-D.ietf-tls-dtls13]
Rescorla, E., Tschofenig, H., and N. Modadugu, "The Rescorla, E., Tschofenig, H., and N. Modadugu, "The
Datagram Transport Layer Security (DTLS) Protocol Version Datagram Transport Layer Security (DTLS) Protocol Version
1.3", draft-ietf-tls-dtls13-31 (work in progress), March 1.3", draft-ietf-tls-dtls13-31 (work in progress), March
skipping to change at page 97, line 29 skipping to change at page 100, line 23
core-parameters.xhtml#content-formats>. core-parameters.xhtml#content-formats>.
[IANA.MediaTypes] [IANA.MediaTypes]
IANA, "Media Types", IANA, "Media Types",
<http://www.iana.org/assignments/media-types>. <http://www.iana.org/assignments/media-types>.
[proto_numbers] [proto_numbers]
"IANA, "Protocol Numbers"", 2011, "IANA, "Protocol Numbers"", 2011,
<http://www.iana.org/assignments/protocol-numbers>. <http://www.iana.org/assignments/protocol-numbers>.
[RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791,
DOI 10.17487/RFC0791, September 1981,
<https://www.rfc-editor.org/info/rfc791>.
[RFC3022] Srisuresh, P. and K. Egevang, "Traditional IP Network [RFC3022] Srisuresh, P. and K. Egevang, "Traditional IP Network
Address Translator (Traditional NAT)", RFC 3022, Address Translator (Traditional NAT)", RFC 3022,
DOI 10.17487/RFC3022, January 2001, DOI 10.17487/RFC3022, January 2001,
<https://www.rfc-editor.org/info/rfc3022>. <https://www.rfc-editor.org/info/rfc3022>.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, DOI 10.17487/RFC3986, January 2005,
<https://www.rfc-editor.org/info/rfc3986>.
[RFC4034] Arends, R., Austein, R., Larson, M., Massey, D., and S. [RFC4034] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "Resource Records for the DNS Security Extensions", Rose, "Resource Records for the DNS Security Extensions",
RFC 4034, DOI 10.17487/RFC4034, March 2005, RFC 4034, DOI 10.17487/RFC4034, March 2005,
<https://www.rfc-editor.org/info/rfc4034>. <https://www.rfc-editor.org/info/rfc4034>.
[RFC4122] Leach, P., Mealling, M., and R. Salz, "A Universally [RFC4122] Leach, P., Mealling, M., and R. Salz, "A Universally
Unique IDentifier (UUID) URN Namespace", RFC 4122, Unique IDentifier (UUID) URN Namespace", RFC 4122,
DOI 10.17487/RFC4122, July 2005, DOI 10.17487/RFC4122, July 2005,
<https://www.rfc-editor.org/info/rfc4122>. <https://www.rfc-editor.org/info/rfc4122>.
skipping to change at page 100, line 22 skipping to change at page 103, line 9
<https://www.rfc-editor.org/info/rfc8340>. <https://www.rfc-editor.org/info/rfc8340>.
[RFC8484] Hoffman, P. and P. McManus, "DNS Queries over HTTPS [RFC8484] Hoffman, P. and P. McManus, "DNS Queries over HTTPS
(DoH)", RFC 8484, DOI 10.17487/RFC8484, October 2018, (DoH)", RFC 8484, DOI 10.17487/RFC8484, October 2018,
<https://www.rfc-editor.org/info/rfc8484>. <https://www.rfc-editor.org/info/rfc8484>.
[RFC8499] Hoffman, P., Sullivan, A., and K. Fujiwara, "DNS [RFC8499] Hoffman, P., Sullivan, A., and K. Fujiwara, "DNS
Terminology", BCP 219, RFC 8499, DOI 10.17487/RFC8499, Terminology", BCP 219, RFC 8499, DOI 10.17487/RFC8499,
January 2019, <https://www.rfc-editor.org/info/rfc8499>. January 2019, <https://www.rfc-editor.org/info/rfc8499>.
Appendix A. CUID Generation
The document recommends the use of SPKI to generate the 'cuid'. This
design choice is motivated by the following reasons:
o SPKI is globally unique.
o It is deterministic.
o It allows to avoid extra cycles that may be induced by 'cuid'
collision.
o DOTS clients do not need to store the 'cuid' in a persistent
storage.
o It allows to detect compromised DOTS clients that do not adhere to
the 'cuid' generation algorithm.
Authors' Addresses Authors' Addresses
Tirumaleswar Reddy (editor) Tirumaleswar Reddy (editor)
McAfee, Inc. McAfee, Inc.
Embassy Golf Link Business Park Embassy Golf Link Business Park
Bangalore, Karnataka 560071 Bangalore, Karnataka 560071
India India
Email: kondtir@gmail.com Email: kondtir@gmail.com
 End of changes. 93 change blocks. 
295 lines changed or deleted 441 lines changed or added

This html diff was produced by rfcdiff 1.48. The latest version is available from http://tools.ietf.org/tools/rfcdiff/