wdiff draft-ietf-dime-group-signaling-02.txt draft-ietf-dime-group-signaling-03.txt

Diameter Maintenance and M. Jones
Extensions (DIME) M. Liebsch
Internet-Draft L. Morand
Intended status: Standards Track October 21, 2013 February 15, 2014
Expires: April 24, August 19, 2014

Diameter Group Signaling
draft-ietf-dime-group-signaling-02.txt
draft-ietf-dime-group-signaling-03.txt

Abstract

In large network deployments, a single Diameter peer can support over
a million concurrent Diameter sessions. Recent use cases have
revealed the need for Diameter peers to apply the same operation to a
large group of Diameter sessions concurrently. The Diameter base
protocol commands operate on a single session so these use cases
could result in many thousands of command exchanges to enforce the
same operation on each session in the group. In order to reduce
signaling, it would be desirable to enable bulk operations on all (or
part of) the sessions managed by a Diameter peer using a single or a
few command exchanges. This document specifies the Diameter protocol
extensions to achieve this signaling optimization.

Status of this Memo

This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.

Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
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This Internet-Draft will expire on April 24, August 19, 2014.

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Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 5
3. Use Cases . . . . Protocol Overview . . . . . . . . . . . . . . . . . . . . . . 5 6
3.1. Building and Modifying Session Groups . . . . . . . . . . 5 6
3.2. Issuing Group Commands . . . . . . . . . . . . . . . . . . 5
4. Grouping User Sessions 6
3.3. Permission Model . . . . . . . . . . . . . . . . . . . . 6
4.1. Group assignment at session initiation . 7
4. Protocol Description . . . . . . . . . 6
4.2. Mid-session group assignment modifications . . . . . . . . 6
4.2.1. Client-initiated group assignment changes . . . . 8
4.1. Session Grouping . . 7
4.2.2. Server-initiated group assignment changes . . . . . . 7
5. Protocol Description . . . . . . . . . . . . . 8
4.1.1. Group assignment at session initiation . . . . . . . . 8
5.1. Session Grouping
4.1.2. Removing a session from a session group . . . . . . . 10
4.1.3. Mid-session group assignment modifications . . . . . . 11
4.2. Session Grouping Capability Discovery . . . . . . . . . . 8
5.2. Session Grouping 12
4.2.1. Implicit Capability Discovery . . . . . . . . . . 9
5.2.1. Implicit . . 12
4.2.2. Explicit Capability Discovery . . . . . . . . . . . . 9
5.2.2. Explicit Capability Discovery . 12
4.3. Releasing a Session Group Identifier . . . . . . . . . . . 9
5.3. 12
4.4. Performing Group Operations . . . . . . . . . . . . . . . 10
5.3.1. 13
4.4.1. Sending Group Commands . . . . . . . . . . . . . . . . 10
5.3.2. 13
4.4.2. Receiving Group Commands . . . . . . . . . . . . . . . 10
5.3.3. Single-Session Fallback 13
4.4.3. Error Handling for Group Commands . . . . . . . . . . 14
4.4.4. Single-Session Fallback . . . . . 11
5.4. Session Management . . . . . . . . . . 14
5. Operation with Proxies Agents . . . . . . . . . . 11
5.4.1. Authorization Session State Machine . . . . . . . . . 11 15
6. Commands Formatting . . . . . . . . . . . . . . . . . . . . . 15 16
6.1. Formatting Example: Group Re-Auth-Request . . . . . . . . . . . . . . . . . . 15 16
7. Attribute-Value-Pairs (AVP) . . . . . . . . . . . . . . . . . 16 17
7.1. Session-Group-Info AVP . . . . . . . . . . . . . . . . . . 16 17
7.2. Session-Group-Feature-Vector AVP . . . . . . . . . . . . . 16 17
7.3. Session-Group-Id AVP . . . . . . . . . . . . . . . . . . . 16 18
7.4. Session-Group-Action AVP . . . . . . . . . . . . . . . . . 17 18
8. Result-Code AVP Values . . . . . . . . . . . . . . . . . . . . 18 19
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19 20
9.1. AVP Codes . . . . . . . . . . . . . . . . . . . . . . . . 19 20
10. Security Considerations . . . . . . . . . . . . . . . . . . . 20 21
11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 21 22
12. Normative References . . . . . . . . . . . . . . . . . . . . . 22 23
Appendix A. Session Management -- Exemplary Session State
Machines . . . . . . . . . . . . . . . . . . . . . . 24
A.1. Authorization Session State Machine . . . . . . . . . . . 24

Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 23 28

1. Introduction

In large network deployments, a single Diameter peer can support over
a million concurrent Diameter sessions. Recent use cases have
revealed the need for Diameter peers to apply the same operation to a
large group of Diameter sessions concurrently. For example, a policy
decision point may need to modify the authorized quality of service
for all active users having the same type of subscription. The
Diameter base protocol commands operate on a single session so these
use cases could result in many thousands of command exchanges to
enforce the same operation on each session in the group. In order to
reduce signaling, it would be desirable to enable bulk operations on
all (or part of) the sessions managed by a Diameter peer using a
single or a few command exchanges.

This document describes mechanisms for grouping Diameter sessions and
applying Diameter commands, such as performing re-authentication, re-
authorization, termination and abortion of sessions to a group of
sessions. This document does not define a new Diameter application.
Instead it defines mechanisms, commands and AVPs that may be used by
any Diameter application that requires management of groups of
sessions.

These mechanisms take the following design goals and features into
account:

o Minimal impact to existing applications

o Extension of existing commands' CCF with optional AVPs to enable
grouping and group operations

o Fallback to single session operation

o Implicit discovery of capability to support grouping and group
operations

2. Terminology

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].

This document uses terminology defined [RFC3588]. [RFC6733].

3. Use Cases Protocol Overview

3.1. Building and Modifying Session Groups

Client and Server can add a new Diameter session to a group, e.g. in
case the subscription profile of the associated user has similar
characteristics as the profile of other users whose Diameter session
has been added to one or multiple groups. Such similarities can be
for example maximum bandwidth bounds of each user in the a group.
These users may share resources of, e.g., an access multiplexer,
together with other users. Runtime adjustments in the granted
bandwidth bounds or other Quality of Service related attributes can
be accomplished for the whole group by identifying the group in the
Diameter group command.

In case a user's subscription profile changes during runtime, either
node, a Diameter Server or Diameter client, may decide to remove this
user's Diameter session from the session group. The user's Diameter
session can be assigned to a different group, whose adjusted profile
matches the one of the different group. Both groups, the user's
previous group and its new group, will be modified mid-session.

In case of mobile users, a change in the node implementing the
Diameter client can happen, which has impact to a group of sessions a
particular pair of Diameter client and server has in common. Due to
mobility, the mobile user's session may get transferred to a new
Diameter client during runtime without mandating from-scratch
authorization. Such scenario necessitates mid-session modification.

3.2. Issuing Group Commands

A policy decision point may decide to terminate a group of sessions,
e.g. based on previous agreement for temporary authorization to
access a system. All Diameter sessions of associated users with such
temporarily granted access will be added to a single Diameter session
group. After the time limit for the temporary authorization has been
reached, the policy decision point can issue a single Session
Termination Request (STR) to the policy enforcement point. The STR
command identifies the group of Diameter sessions which are to be
terminated. The policy enforcement point treats the STR as group
command and initiates termination of all sessions in the group.
Subsequently, the policy enforcement point confirms successful
termination of these sessions to the policy decision point by sending
a single Session Termination Answer (STA) command which includes the
identifier of the group.

4. Grouping User Sessions

Either

3.3. Permission Model

A permission model in the context of this draft defines the
permission of Diameter peer may assign a nodes to build new session groups, to add/
remove a group. Diameter AAA
applications typically assign client and server roles to the Diameter
peers.

4.1. Group assignment at session initiation

Assignment of to/from a new session to a group is accomplished by the
Diameter server when requested by and to delete an existing
session group.

This specification follows the most flexible model where both, a
Diameter client. Without being
explicitly requested by the client, the client and a Diameter server can assign build a new session to a server-assigned group based on its own decision.
When and
assign a new session is to be assigned identifier to a group by the Diameter
server, the server assigns a new that session to at least one server-
assigned group. To complement server-assigned grouping, When a Diameter
client can assign a session node
decides to issue a client-assigned group.

To assign a new session group, e.g. to a group at all sessions
which share certain characteristics, the node must identify itself in
the DiameterIdentity element of the session initiation, a Diameter
client sends a service specific request, e.g. NASREQ AAR [RFC4005],
containing one or more group identifiers. identifier
(Section 7.3) as owner of the group. The Diameter client can
assign permission model as per
this specification solely constrains the session permission to close a client-assigned
session group and identify release the associated identifier to the group with an appended client-assigned group identifier.
The client can append multiple client-assigned group identifiers if
owner.

Irrespective of the client assigns group ownership, as per this specification any
Diameter node has the new session permission to more than one add/remove a session to/from an
existing session group. If Also the
Diameter client does not send modification of groups in terms of
moving a client-assigned group identifier, the
client may receive session from one or multiple server-assigned session group identifiers
in the server's response, which identify the server-assigned groups to which the new a different session has been assigned. The Diameter client can
explicitly request the Diameter server group
is permitted to perform grouping of the new
session.

Assuming the user has been successfully authenticated and/or
authorized, the any Diameter server responds with service-specific auth
response, e.g. NASREQ AAA [RFC4005], containing both the client-
assigned group identifiers (if sent with the request) and one or node. The enforcement of a more
server-assigned group identifiers.

Both peers, the Diameter client and
constrained model is left to the Diameter server, must keep a
list of all group identifiers which identify all client- application and server-
assigned groups to implementation,
which the session has been assigned.

4.2. Mid-session group assignment modifications

Either must then ensure that relevant Diameter peer may modify nodes have the group membership same
view of an active
Diameter session. A Diameter client MAY remove the group(s) assigned
to the active session by the Diameter server and vice versa.

This document does not define permission model, either through administrative
configuration or protocol-based capability discovery. Details about
enforcing a more constraint permission model that limits removal are out of scope of a session from a group by the same peer that added the session to
the group. However, applications which re-use the commands and
methods defined in this document may impose their own permission
model.
specification. For example, an application a more constrained model could require
that the server a client MUST NOT remove a session from a group assigned by the client.

4.2.1. Client-initiated group assignment changes

To update the assigned groups mid-session, a Diameter client sends a
service specific re-authorization request containing the updated list
of group identifiers. Assuming the user which is successfully
authenticated and/or authorized, the Diameter server responds with a
service-specific auth response containing the updated list of group
identifiers received in the request.

4.2.2. Server-initiated group assignment changes

To update the assigned groups mid-session, a Diameter server sends a
Re-authorization Request (RAR) message requesting re-authorization
and the client responds with a Re-authorization Answer (RAA) message.
The Diameter client sends a service specific re-authorization request
containing the current list of group identifiers and the Diameter
server responds with a service-specific auth response containing owned
by the
updated list of group identifiers.

5. server.

4. Protocol Description

5.1.

4.1. Session Grouping

Either Diameter peer, a Diameter client or server, peer can initiate assigning a session to a single or
multiple session groups according
to the procedure described in Section 4. groups. Modification of a group by removing or
adding a single or multiple user sessions can be initiated and
performed at runtime by either Diameter peer. Diameter AAA
applications typically assign client and server roles to the Diameter
peers, which are referred to as relevant Diameter peers to utilize
session grouping and issue group commands. Section 5 describes
particularities about session grouping and performing group commands
when relay agents or proxies are deployed.

Diameter peers, which are group-aware, must store and maintain a list
of all session groups to which at least one session, for which the
peer holds a state, is assigned. Along with the group's Session-Id,
a list of Diameter sessions, which are assigned to the group, must be
stored. This specification assumes that a session group is built and
handled between pairs of Diameter nodes. Clients and servers MUST
maintain Diameter state of individual sessions grouped in a session
group.

4.1.1. Group assignment at session initiation

To assign a session to a group at session initiation, a Diameter
client sends a service specific request, e.g. NASREQ AAR [RFC4005],
containing one or more group identifiers. A Diameter client as
sender of a command for session initiation can determine one or
multiple groups to which the new session should be assigned. Each of
these groups need to be identified by a unique Session-Group-Id
contained in a separate Session-Group-Info AVP as specified in
Section 7.

In each appended Session-Group-Info AVP which carries

The client may choose one or multiple sessions from a list of
existing session groups, irrespective of the group
identifier, ownership.
Alternatively, the SESSION_GROUP_ALLOCATION_MODE flag client may decide to create a new group and
identify itself in the DiameterIdentity element of the Session-
Group-Feature-Vector
Group-Session-Id AVP as per Section 7.3

The client MUST be:

o set (1) the SESSION_GROUP_ALLOCATION_ACTION of the
Session-Group-Feature-Vector AVP in each appended Session-Group-Info
AVP to indicate that the carried group identifier is a server-
assigned group;

o cleared (0) identified session should be added to indicate that the carried group identifier is a
client-assigned
identified session group.

A Diameter client can explicitly request

If the Diameter server as
recipient receives a command request from a Diameter
client and the command comprises at least one Session-Group-Info AVP
having the SESSION_GROUP_ALLOCATION_ACTION flag of the message to assign Session-Group-
Feature-Vector AVP set, the server must add the new session to each
of the one or multiple identified session groups. In case one or
multiple
server-assigned identified session groups by appending a Session-Group-Info AVP with no
Session-Group-Id AVP and the Session-Group-Feature-Vector AVP with are not know to the SESSION_GROUP_ALLOCATION_MODE flag set (1).

If server, the Diameter
server receives must add the one or multiple new groups to its locally
maintained list of session groups. When sending the response to the
client, e.g. a service-specific auth response as per NASREQ AAA
[RFC4005], the server must include all Session-Group-Info AVP with no
Session-Group-Id AVP and AVPs as
received in the Session-Group-Feature-Vector AVP with client's request.

In addition to the SESSION_GROUP_ALLOCATION_MODE flag set (1), one or multiple session groups identified in the
client's request, the Diameter server
SHOULD assign may decide to add the new session to one
or multiple server-assigned additional groups. The Diameter In such case, the server identifies each of these server-assigned
groups in a Session-Group-Id AVP contained in a Session-Group-Info
AVP, which are appended add to the
response additional Session-Group-Info AVPs, each identifying a
session group, to which the received command. server has assigned the new session.
Each of these the Session-Group-Info AVPs must have AVP added by the
SESSION_GROUP_ALLOCATION_MODE server, the
SESSION_GROUP_ALLOCATION_ACTION flag of the Session-Group-Feature-
Vector AVP set to indicate that the carried identifier is a server-
assigned group identifier. must be set.

If the Diameter server receives a Session-Group-Info AVP with command for session initiation from
a
Session-Group-Id AVP Diameter client and the Session-Group-Feature-Vector AVP with
the SESSION_GROUP_ALLOCATION_MODE flag cleared (0), the server must
store command comprises at least one Session-
Group-Info AVP, but the one or multiple Session-Group-Info AVP do not
identify any session group identifiers and associate to which the new session with these client-assigned groups. The Diameter should be assigned,
the server may
still assign the new session to one or multiple server-assigned session
groups. The Diameter Each session group, to which the server identifies each of these server-assigned
groups in a Session-Group-Id AVP contained assigns the new
session, must be identified in a separate Session-Group-Info
AVP, which are appended to AVP
having the response to SESSION_GROUP_ALLOCATION_ACTION flag of the received command, in
addition to associated
Session-Group-Vector AVP set.

If the those related Diameter client receives a response to its previously issued
request from the client-assigned groups received
in server and the request. Each of these response comprises at least one
Session-Group-Info AVPs must have AVP having the
SESSION_GROUP_ALLOCATION_MODE SESSION_GROUP_ALLOCATION_ACTION
flag of the Session-Group-Feature-
Vector associated Session-Group-Feature-Vector AVP set set, the
client must add the new session to indicate that this carried identifier is a server-
assigned group identifier. all session groups as identified
in the one or multiple Session-Group-Info AVPs.

A Diameter server receiving a command for session initiation which
includes at least one Session-Group-Info AVP but the server does not
understand the semantics of this optional AVP because it does not
support group operations according to the specification in this
document, MUST ignore the optional group operations specific AVPs and
proceed with processing the command for a single session.

A Diameter client, which sent a request for session initiation to a
Diameter server and appended a single or multiple Session-Group-Id
AVPs but cannot find any Session-Group-Info AVP in the associated
response from the Diameter server proceeds with processing the
command for a single session. Furthermore, the client keeps a log to
remember that the server is not able to perform group operations.

5.2.

4.1.2. Removing a session from a session group

When a Diameter client decides to remove a session from a particular
session group, the client sends a service-specific re-authorization
request to the server and adds one Session-Group-Info AVP to the
request for each session group, from which the client wants to remove
the session. The session, which is to be removed from a group, is
identified in the Session-Id AVP of the command request. The
SESSION_GROUP_ALLOCATION_ACTION flag of the Session-Group-Feature-
Vector AVP in each Session-Group-Info AVP must be cleared to indicate
removal of the session from the session group identified in the
associated Session-Group-id AVP.

When a Diameter client decides to remove a session from all session
groups, to which the session has been previously assigned, the client
sends a service-specific re-authorization request to the server and
adds a single Session-Group-Info AVP to the request which has the
SESSION_GROUP_ALLOCATION_ACTION flag cleared and the Session-Group-Id
AVP omitted. The session, which is to be removed from all groups, to
which the session has been previously assigned, is identified in the
Session-Id AVP of the command request.

If the Diameter server receives a request from the client which has
at least one Session-Group-Info AVP appended with the
SESSION_GROUP_ALLOCATION_ACTION flag cleared, the server must remove
the session from the session group identified in the associated
Session-Group-Id AVP. If the request comprises at least one Session-
Group-info AVP with the SESSION_GROUP_ALLOCATION_ACTION flag cleared
and no Session-Id AVP present, the server must remove the session
from all session groups to which the session has been previously
assigned. The server must include in its response to the requesting
client all Session-Group-Id AVPs as received in the request.

When the Diameter server decides to remove a session from one or
multiple particular session groups or from all session groups to
which the session has been assigned beforehand, the server sends a
Re-Authorization Request (RAR) to the client, indicating the session
in the requests Session-Id AVP. The client sends a Re-Authorization
Answer (RAA) to respond to the server's request. The client
subsequently sends service-specific re-authorization request
containing one or multiple Session-Group-Info AVPs, each indicating a
session group, to which the session had been previously assigned. To
indicate removal of the indicated session from one or multiple
session groups, the server sends a service-specific auth response to
the client, containing a list of Session-Group-Info AVPs with the
SESSION_GROUP_ALLOCATION_ACTION flag cleared and the Session-Group-Id
AVP identifying the session group, from which the session should be
removed. The server MAY include to the service-specific auth
response a list of Session-Group-Info AVPs with the
SESSION_GROUP_ALLOCATION_ACTION flag set and the Session-Group-Id AVP
identifying session groups to which the session remains subscribed.
In case the server decides to remove the identified session from all
session groups, to which the session has been previously assigned,
the server includes in the service-specific auth response at least
one Session-Group-Info AVP with the SESSION_GROUP_ALLOCATION_ACTION
flag cleared and Session-Group-Info AVP absent.

4.1.3. Mid-session group assignment modifications

Either Diameter peer can modify the group membership of an active
Diameter session, irrespective of the group ownership.

To update an assigned group mid-session, a Diameter client sends a
service-specific re-authorization request to the server, containing
one or multiple Session-Group-Info AVPs with the
SESSION_GROUP_ALLOCATION_ACTION flag set and the Session-Group-Id AVP
present, identifying the session group to which the session should be
added. With the same message, the client may send one or multiple
Session-Group-Info AVP with the SESSION_GROUP_ALLOCATION_ACTION flag
cleared and the Session-Group-Id AVP identifying the session group
from which the identified session is to be removed. To remove the
session from all previously assigned session groups, the client
includes at least one Session-Group-Info AVP with the
SESSION_GROUP_ALLOCATION_ACTION flag cleared and no Session-Group-Id
AVP present. When the server received the service-specific re-
authorization request, it must update its locally maintained view of
the session groups for the identified session according to the
appended Session-Group-Info AVPs. The server sends a service-
specific auth response to the client containing one or multiple
Session-Group-Info AVPs with the SESSION_GROUP_ALLOCATION_ACTION flag
set and the Session-Group-Id AVP identifying the new session group to
which the identified session has been added.

When a Diameter server enforces an update to the assigned groups mid-
session, it sends a Re-Authorization Request (RAR) message to the
client identifying the session, for which the session group lists are
to be updated. The client responds with a Re-Authorization Answer
(RAA) message. The client subsequently sends service-specific re-
authorization request containing one or multiple Session-Group-Info
AVPs with the SESSION_GROUP_ALLOCATION_ACTION flag set and the
Session-Group-Id AVP identifying the session group to which the
session had been previously assigned. The server responds with a
service-specific auth response and includes one or multiple Session-
Group-Info AVP with the SESSION_GROUP_ALLOCATION_ACTION flag set and
the Session-Group-Id AVP identifying the session group, to which the
identified session is to be added. With the same response message,
the server may send one or multiple Session-Group-Info AVPs with the
SESSION_GROUP_ALLOCATION_ACTION flag cleared and the Session-Group-Id
AVP identifying the session groups from which the identified session
is to be removed. When server wants to remove the session from all
previously assigned session groups, it send at least on Session-
Group-Info AVP with the response having the
SESSION_GROUP_ALLOCATION_ACTION flag cleared and no Session-Group-Id
AVP present.

4.2. Session Grouping Capability Discovery

5.2.1.

4.2.1. Implicit Capability Discovery

By appending at least one Session-Group-Info AVP, the Diameter client
announces its capability to support group operations according to the
specification in this document to the addressed Diameter server. If
the Diameter client supports group operations, it MUST append at
least one Session-Group-Info AVP to announce its capability to
support group operations.

A session-group aware Diameter server receiving a command for session
initiation which includes at least one Session-Group-Info AVP learns
about the sender's capability to support group operations.

By appending at least one Session-Group-Id AVP, the Diameter server
announces its capability to support group operations according to the
specification in this document to the addressed Diameter client.

5.2.2.

4.2.2. Explicit Capability Discovery

New Diameter applications may consider support for Diameter session
grouping and for performing group commands during the standardization
process. Such applications provide intrinsic support for the support
of group commands and announce this capability through the assigned
application ID.

5.3.

4.3. Releasing a Session Group Identifier

To close a session group and release the associated Session-Group-Id
value, the owner of a session group appends a single Session-Group-
Info AVP having the SESSION_GROUP_STATUS_IND flag cleared and the
Session-Group-Id AVP identifying the session group, which is to be
closed. The SESSION_GROUP_ALLOCATION_ACTION flag of the associated
Session-Group-Feature-Vector AVP MUST be cleared.

4.4. Performing Group Operations

5.3.1.

4.4.1. Sending Group Commands

Either Diameter peer can request the recipient of a request to
process an associated command for all sessions being assigned to one
or multiple groups by identifying these groups in the request. The
sender of the request appends for each group, to which the command
applies, a Session-Group-Info AVP including the Session-Group-Id AVP
and indicates in
to identify the SESSION_GROUP_ALLOCATION_MODE flag of associated session group. Both, the
Session-Group-Feature-Vector AVP whether
SESSION_GROUP_ALLOCATION_ACTION flag as well as the identifier represents a
server- or a client-assigned group.
SESSION_GROUP_STATUS_IND flag must be set.

If the CCF of the request mandates a Session-Id AVP, the Session-Id
AVP MUST identify a single session which is assigned to at least one
of the groups being identified in the appended Session-Group-Id AVPs.

The sender of the request can indicate to the receiver how follow up
message exchanges should be performed by appending a Session-Group-
Action AVP. If the sender wants the receiver to perform follow up
exchanges with a single command for all impacted groups, the sender
sets the value of the Session-Group-Action AVP to ALL_GROUPS (1). If
follow up message exchanges should be performed on a per-group basis
in case multiple groups are identified in the group command, the
value of the Session-Group-Action AVP is set to PER_GROUP (2). A
value set to PER_SESSION (3) indicates to the receiver that all
follow up exchanges should be performed using a single message for
each impacted session.

If the sender wants the receiver of the request to process the
associated command solely for a single session does not append any
group identifier, but identifies the relevant session in the
Session-Id AVP.

5.3.2.

4.4.2. Receiving Group Commands

A Diameter peer receiving a request to process a command for a group
of sessions identifies the relevant groups according to the appended
Session-Group-Id AVP in the Session-Group-Info AVP. If the received
request identifies multiple groups in multiple appended Session-
Group-Id AVPs, the receiver should process the associated command for
each of these groups. if a session has been assigned to more than one
of the identified groups, the receiver must process the associated
command only once per session.

The Diameter peer receiving a request which requests performing the
command to at least on session group SHOULD perform follow up message
exchanges according to the value identified in the Session-Group-Info
AVP.

5.3.3.

4.4.3. Error Handling for Group Commands

When a Diameter peer receives a request to process a command for one
or more session groups and the result of processing the command is an
error that applies to all sessions in the identified groups, an
associated protocol error must be returned to the source of the
request. In such case, the sender of the request MUST fall back to
single-session processing and the session groups, which have been
identified in the group command, MUST be closed according to the
procedure described in Section 4.3.

When a Diameter peer receives a request to process a command for one
or more session groups and the result of processing the command
succeeds for some sessions identified in one or multiple session
groups, but fails for one or more sessions, the Result-Code AVP in
the response message SHOULD indicate DIAMETER_LIMITED_SUCCESS as per
Section 7.1.2 of [RFC6733]. In case of limited success, the
sessions, for which the processing of the group command failed, MUST
be identified using a Failed-AVP AVP as per Session 7.5 of [RFC6733].

4.4.4. Single-Session Fallback

Either Diameter peer, a Diameter client or a Diameter server, can
fall back to single session operation by ignoring and omitting the
optional group session-specific AVPs. Fallback to single-session
operation is performed by processing the Diameter command solely for
the session identified in the mandatory Session-Id AVP. The response
to the group command must not identify any group but identify solely
the single session for which the command has been processed.

5.4. Session Management

Editor's note:

5. Operation with Proxies Agents

This document revision adopts the WG's current view on
how Diameter commands can be formatted to enable group signaling.
The required change in the formatting and protocol operation has not
yet been considered specification assumes in this Section 5.4 , which still reflects the
formatting as per version 0 case of this specification. The described
session state machines still need revision to reflect the generalized
formatting and the adopted protocol operation.

5.4.1. Authorization Session State Machine

Section 8.1 in [RFC3588] defines a set of finite state machines,
representing the life cycle of present stateful Proxy Agent
between a Diameter sessions, client and which MUST be
observed by all a Diameter implementations server that make use of the
authentication and/or authorization portion Proxy Agent
is aware of a Diameter
application. This section defines session groups and session group handling. The Proxy
MUST reflect the additional state transitions
related to the processing of the new commands which may impact
multiple sessions.

The group membership is each session state and therefore only those state
machines from [RFC3588] in which the server is maintaining associated with a session
state are relevant in this document. As in [RFC3588], the term
Service-Specific below refers
group according to the result of a message defined in group command operated between a
Diameter
application (e.g., Mobile IPv4, NASREQ).

The following state machine is observed by a client when state is
maintained on the server. State transitions which are unmodified
from [RFC3588] are not repeated here.

CLIENT, STATEFUL
State Event Action New State
---------------------------------------------------------------
Idle Client or Device Requests Send Pending
access service
specific
auth req
optionally
including
groups

Open GASR received with Send GASA Discon
Session-Group-Action with
= ALL_GROUPS, Result-Code
session is assigned to = SUCCESS,
received group(s) and Send GSTR.
client will comply with
request to end the a server.

In case a Proxy Agent manipulates session

Open GASR received with Send GASA Discon
Session-Group-Action with
= PER_GROUPS, Result-Code groups, it MUST maintain
consistency of session is assigned to = SUCCESS,
received group(s) and Send GSTR groups between a client will comply with per group
request to end the session

Open GASR received with Send GASA Discon
Session-Group-Action with
= PER_SESSION, Result-Code
session is assigned to = SUCCESS,
received group(s) and Send STR
client will comply with per session
request a server. This
applies to end deployment where the Proxy Agent utilizes session

Open GASR received, Send GASA Open
client will not comply with with
request to end all session Result-Code
in received group(s) != SUCCESS

Discon GSTA Received Discon. Idle
user/device

Open GRAR received with Send GRAA, Pending
Session-Group-Action Send
= ALL_GROUPS, service
session is assigned to specific
received group(s) and group
client will perform re-auth req
subsequent re-auth

Open GRAR received with Send GRAA, Pending
Session-Group-Action Send
= PER_GROUP, service
session is assigned to specific
received group(s) grouping
and performing group commands with, for example, a Diameter server,
whereas the Diameter client will perform re-auth req
subsequent re-auth per group

Open GRAR received with Send GRAA, Pending
Session-Group-Action Send
= PER_SESSION, service
session is assigned not group-aware. The same applies to specific
received group(s) and re-auth req
deployment where all nodes, the Diameter client will perform per session
subsequent re-auth

Open GRAR received and client will Send GRAA Idle
not perform subsequent with
re-auth Result-Code
!= SUCCESS,
Discon.
user/device

Pending Successful service-specific Provide Open
group re-authorization answer service
received.

Pending Failed service-specific Discon. Idle
group re-authorization answer user/device
received.

The following state machine is observed by a server when it is
maintaining state for server, as well
as the session. State transitions which Proxy Agent are
unmodified from [RFC3588] are not repeated here.

SERVER, STATEFUL
State Event Action New State
---------------------------------------------------------------

Idle Service-specific authorization Send Open
request received, and user successful
is authorized service
specific
answer
optionally
including
groups

Open Server wants group-aware but the Proxy Agent manipulates
groups, e.g. to terminate Send GASR Discon
group(s)

Discon GASA received Cleanup Idle

Any GSTR received Send GSTA, Idle
Cleanup

Open Server wants adopt different administrative policies that apply to reauth Send GRAR Pending
group(s)

Pending GRAA received with Result-Code Update Open
= SUCCESS session(s)

Pending GRAA received with Result-Code Cleanup Idle
!= SUCCESS session(s)

Open Service-specific group Send Open
re-authoization request successful
received and user is service
authorized specific
group
re-auth
answer

Open Service-specific group Send Idle
re-authorization request failed
received
the client's domain and user is service
not authorized specific
group
re-auth
answer,
cleanup the server's domain.

6. Commands Formatting

This document does not specify new Diameter commands to enable group
operations, but relies on command extensibility capability provided
by the Diameter Base protocol. This section provides the guidelines
to extend the CCF of existing Diameter commands with optional AVPs to
enable the recipient of the command to perform the command to all
sessions associated with the identified group(s).

6.1. Formatting Example: Group Re-Auth-Request

A request that one or more groups of users are re-authentication is
issues
issued by appending one or multiple Session-Group-Id AVP(s) to the
Re-Auth-Request (RAR). The one or multiple Session-Group-Id AVP(s)
identify the associated group(s) for which the group re-
authentication has been requested. The recipient of the group
command initiates re-authentication for all users associated with the
identified group(s). Furthermore, the sender of the group re-
authentication request appends a Session-Group-Action AVP to provide
more information to the receiver of the command about how to
accomplish the group operation.

The value of the mandatory Session-Id AVP MUST identify a session
associated with a single user, which is assigned to at least one of
the groups being identified in the appended Session-Group-Id AVPs.

<RAR> ::= < Diameter Header: 258, REQ, PXY >
< Session-Id >
{ Origin-Host }
{ Origin-Realm }
{ Destination-Realm }
{ Destination-Host }
{ Auth-Application-Id }
{ Re-Auth-Request-Type }
[ User-Name ]
[ Origin-State-Id ]
* [ Proxy-Info ]
* [ Route-Record ]
* [ Session-Group-Id ]
[ Session-Group-Action ]
* [ AVP ]

7. Attribute-Value-Pairs (AVP)

+--------------------+
| AVP Flag rules |
+----+---+------+----+
AVP | | |SHOULD|MUST|
Attribute Name Code Value Type |MUST|MAY| NOT | NOT|
+-------------------------------------------------+----+---+------+----+
|Session-Group-Info TBD1 Grouped | | P | | V |
|Session-Group-Feature-Vector TBD2 Unsigned32 | | P | | V |
|Session-Group-Id TBD3 OctetString | | P | | V |
|Session-Group-Action TBD4 Unsigned32 | | P | | V |
+-------------------------------------------------+----+---+------+----+

AVPs for the Diameter Group Signaling

7.1. Session-Group-Info AVP

The Session-Group-Info AVP (AVP Code TBD1) is of type Grouped. It
contains the identifier of the session group as well as an indication
of the node responsible for session group identifier assignment.
Session-Group-Info ::= < AVP Header: TBD1 >
< Session-Group-Feature-Vector >
[ Session-Group-Id ]
* [ AVP ]

7.2. Session-Group-Feature-Vector AVP

The Session-Group-Feature-Vector AVP (AVP Code TBD2) is of type
Unsigned32 and and contains a 32-bit flags field of capabilities
supported by the session-group aware node.

The following capabilities are defined in this document:

SESSION_GROUP_ALLOCATION_MODE

SESSION_GROUP_ALLOCATION_ACTION (0x00000001)

This flag indicates the mode of allocation of session group
identifier. action to be performed for the identified
session. When this flag is set, it indicates that the identified
Diameter
server session is responsible for to be added to the allocation of session group as identified
by the Session-Group-Id AVP or the session's assignement to the
session group
identifier. identified in the Session-Group-Id AVP is still
valid. When this the flag is cleared, the identified Diameter session
is to be removed from at least one session group. When the flag
is cleared and the Session-Group-Info AVP identifies a particular
session group in the associated Session-Group-Id AVP, the session
is to be removed solely from the identified session group. When
the flag is cleared and the Session-Group-Info AVP does not set,
identify a particular session group (Session-Group-Id AVP is
absent), the identified Diameter session is to be removed from all
session groups, to which it has been previously assigned.

SESSION_GROUP_STATUS_IND (0x00000010)

This flag indicates that the status of the session group identifier identified in
the associated Session-Group-Id AVP. The flag is set when the
identified session group has just been created or is still active.
If the flag is cleared, the identified session group is closed and
the associated Session-Group-Id is released. If the Session-
Group-Info AVP does not comprise a Session-Group-Id AVP, this flag
is allocated meaningless and MUST be ignored by the client. receiver.

7.3. Session-Group-Id AVP

The Session-Group-Id AVP (AVP Code TBD3) is of type UTF8String and
identifies a group of Diameter sessions.

The Session-Group-Id MUST be globally and eternally unique, as it is
meant to uniquely identify a group of Diameter sessions without
reference to any other information.

Unless stated otherwise, the

The default format of the Session-Group-id
SHOULD MUST comply to the format
recommended for a Session-Id, as defined in the section 8.8 of the RFC6733
[RFC6733]. However, the exact
format The DiameterIdentity element of the Session-Group-Id MAY be specified by MUST
identify the Diameter
applications node, which make use of group signaling commands. owns the session group.

7.4. Session-Group-Action AVP

The Session-Group-Action AVP (AVP Code TBD4) is of type Unsigned32
and contains a 32-bit address space representing values indicating
how the peer SHOULD issue follow up exchanges in response to a
command which impacts mulitple sessions. The following values are
defined by this application:

ALL_GROUPS (1)
Follow up exchanges should be performed with a single message
exchange for all impacted groups.

PER_GROUP (2)
Follow up exchanges should be performed with a message exchange
for each impacted group.

PER_SESSION (3)
Follow up exchanges should be performed with a message exchange
for each impacted session.

8. Result-Code AVP Values

This document does not define new Result-Code [RFC3588] [RFC6733] values for
existing applications, which are extended to support group commands.
Specification documents of new applications, which will have
intrinsic support for group commands, may specify new Result-Codes.

9. IANA Considerations

This section contains the namespaces that have either been created in
this specification or had their values assigned to existing
namespaces managed by IANA.

9.1. AVP Codes

This specification requires IANA to register the following new AVPs
from the AVP Code namespace defined in [RFC3588]. [RFC6733].

o Session-Group-Info

o Session-Group-Feature-Vector

o Session-Group-Id

o Session-Group-Action

The AVPs are defined in Section 7.

10. Security Considerations

TODO

11. Acknowledgments

The authors of this document want to thank Ben Campbell and Eric
McMurry for their valuable comments to early versions of this draft.

12. Normative References

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.

[RFC3588] Calhoun, P., Loughney, J., Guttman, E., Zorn, G., and J.
Arkko, "Diameter Base Protocol", RFC 3588, September 2003.

[RFC4005] Calhoun, P., Zorn, G., Spence, D., and D. Mitton,
"Diameter Network Access Server Application", RFC 4005,
August 2005.

[RFC6733] Fajardo, V., Arkko, J., Loughney, J., and G. Zorn,
"Diameter Base Protocol", RFC 6733, October 2012.

Appendix A. Session Management -- Exemplary Session State Machines

A.1. Authorization Session State Machine

Section 8.1 in [RFC6733] defines a set of finite state machines,
representing the life cycle of Diameter sessions, and which MUST be
observed by all Diameter implementations that make use of the
authentication and/or authorization portion of a Diameter
application. This section defines the additional state transitions
related to the processing of the new commands which may impact
multiple sessions.

The group membership is session state and therefore only those state
machines from [RFC6733] in which the server is maintaining session
state are relevant in this document. As in [RFC6733], the term
Service-Specific below refers to a message defined in a Diameter
application (e.g., Mobile IPv4, NASREQ).

The following state machine is observed by a client when state is
maintained on the server. State transitions which are unmodified
from [RFC6733] are not repeated here.

A Diameter group command in the following tables is differentiated
from a single-session related command by a preceding 'G'. A Group
Re-Auth Request, which applies to one or multiple session groups, has
been exemplarily described in Section 6.1. Such Group RAR command is
denoted as 'GRAR' in the following table. The same notation applies
to other commands as per [RFC6733].

Open GASR received with Send GASA Discon
Session-Group-Action with
= PER_GROUPS, Result-Code
session is assigned to = SUCCESS,
received group(s) and Send GSTR
client will comply with per group
request to end the session
Open GASR received with Send GASA Discon
Session-Group-Action with
= PER_SESSION, Result-Code
session is assigned to = SUCCESS,
received group(s) and Send STR
client will comply with per session
request to end the session

Open GASR received, Send GASA Open
client will not comply with with
request to end all session Result-Code
in received group(s) != SUCCESS

Discon GSTA Received Discon. Idle
user/device

Open GRAR received with Send GRAA, Pending
Session-Group-Action Send
= PER_GROUP, service
session is assigned to specific
received group(s) and group
client will perform re-auth req
subsequent re-auth per group

Open GRAR received with Send GRAA, Pending
Session-Group-Action Send
= PER_SESSION, service
session is assigned to specific
received group(s) and re-auth req
client will perform per session
subsequent re-auth

Open GRAR received and client will Send GRAA Idle
not perform subsequent with
re-auth Result-Code
!= SUCCESS,
Discon.
user/device

Pending Successful service-specific Provide Open
group re-authorization answer service
received.

Pending Failed service-specific Discon. Idle
group re-authorization answer user/device
received.

The following state machine is observed by a server when it is
maintaining state for the session. State transitions which are
unmodified from [RFC6733] are not repeated here.

SERVER, STATEFUL
State Event Action New State
---------------------------------------------------------------

Idle Service-specific authorization Send Open
request received, and user successful
is authorized service
specific
answer
optionally
including
groups

Open Server wants to terminate Send GASR Discon
group(s)

Discon GASA received Cleanup Idle

Any GSTR received Send GSTA, Idle
Cleanup

Open Server wants to reauth Send GRAR Pending
group(s)

Pending GRAA received with Result-Code Update Open
= SUCCESS session(s)

Pending GRAA received with Result-Code Cleanup Idle
!= SUCCESS session(s)

Open Service-specific group Send Open
re-authoization request successful
received and user is service
authorized specific
group
re-auth
answer

Open Service-specific group Send Idle
re-authorization request failed
received and user is service
not authorized specific
group
re-auth
answer,
cleanup

Authors' Addresses

Mark Jones

Email: mark@azu.ca

Marco Liebsch

Email: marco.liebsch@neclab.eu

Lionel Morand

Email: lionel.morand@orange.com