Internet DRAFT - draft-garcia-sipping-etsi-ngn-p-headers
draft-garcia-sipping-etsi-ngn-p-headers
Network Working Group M. Garcia-Martin
Internet-Draft Nokia
Expires: January 2, 2006 July 1, 2005
Private Header (P-Header) Extensions to the Session Initiation Protocol
(SIP) in support of the European Telecommunications Standards Institute
(ETSI) Next Generation Networks (NGN)
draft-garcia-sipping-etsi-ngn-p-headers-00
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Copyright Notice
Copyright (C) The Internet Society (2005).
Abstract
This document describes a private SIP header field (P-header) used by
the European Telecommunications Standards Institte (ETSI) in Next
Generation Networks (NGN). The P-header is used for triggering
services.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Overall Applicability . . . . . . . . . . . . . . . . . . . . 3
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. SIP Private Headers . . . . . . . . . . . . . . . . . . . . . 3
4.1 The SIP P-AoC header field . . . . . . . . . . . . . . . . 3
4.1.1 Applicability statement of the P-AoC header field . . 4
4.1.2 Usage of the SIP P-AoC header field . . . . . . . . . 4
4.1.3 Syntax of the P-AoC header field . . . . . . . . . . . 5
4.1.4 Table of methods . . . . . . . . . . . . . . . . . . . 6
4.2 Security Considerations . . . . . . . . . . . . . . . . . 6
4.3 IANA Considerations . . . . . . . . . . . . . . . . . . . 6
4.4 Acknowledgements . . . . . . . . . . . . . . . . . . . . . 7
5. References . . . . . . . . . . . . . . . . . . . . . . . . . . 7
5.1 Normative References . . . . . . . . . . . . . . . . . . . 7
5.2 Informative References . . . . . . . . . . . . . . . . . . 7
Author's Address . . . . . . . . . . . . . . . . . . . . . . . 8
Intellectual Property and Copyright Statements . . . . . . . . 9
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1. Introduction
The European Telecommunication Standards Institute (ETSI) is
defininig a Next Generation Network (NGN) where a substantial part of
it is based on the IP Multimedia Subsystem (IMS) defined by the
Third-Generation Partnership Project (3GPP). IMS is largely based on
the Session Initiation Protocol [RFC3261].
ETSI has developed a number of requirements [I-D.jesske-sipping-
tispan-requirements] to support the usage of SIP in Next Generation
Networks that interoperate, at the service level, with the Public
Switched Telephone Network (PSTN), the Integrated Services Digital
Network (ISDN), the 3GPP IP Multimedia Subsystem (IMS), and SIP
networks and terminals that implement the service logic.
In order to provide full support in SIP of existing services,
extensions to SIP are needed. This document defines a number of
Private headers (P- headers) to support those services.
2. Overall Applicability
The SIP extensions specified in this document make certain
assumptions regarding network topology, linkage between SIP and lower
layers, and the availability of transitive trust. These assumptions
are generally NOT APPLICABLE in the Internet as a whole. The
mechanisms specified here were designed to satisfy the requirements
specified by ETSI NGN [I-D.jesske-sipping-tispan-requirements] for
which either no general-purpose solution was planned, where
insufficient operational experience was available to understand if a
general solution is needed, or where a more general solution is not
yet mature. An analysis of these requirements is documented in the
ETSI NGN Analysis ID [I-D.jesske-sipping-tispan-analysis]. For more
details about the assumptions made about these extensions, consult
the Applicability subsection for each extension.
3. Terminology
The keywords MUST, MUST NOT, REQUIRED, SHALL, SHALL NOT, SHOULD,
SHOULD NOT, RECOMMENDED, MAY, and OPTIONAL, when they appear in this
document, are to be interpreted as described in RFC 2119 [RFC2119].
4. SIP Private Headers
4.1 The SIP P-AoC header field
This extension allows a User Agent Client (UAC) to request, at the
time of sending a request, that an Application Server provides
charging information related to the request where the header field is
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included. The actual information to be delivered to the UAC is
outside the scope of this specification, but in general, it is
supposed to contain detailed information related to the session,
subscription, messaging or any other SIP request that may incur
charges to the user.
The scope of this document is limited to defining the header field
that provides a hint to an application server that the user is
willing to receive advice of charge information. The actual
mechanism and the contents of the advice of charging information
delivered to the user are outside the scope of this document, but as
an example, the application sender can send an instant message with
the advice of charge information, or the instant message can contain
a link to a web page that contains more detailed and accurate data.
The actual information to be delivered to the UAC is supposed to
contain detailed information related to the session, subscription,
messaging or any other SIP request that may incur charges to the
user, but once more, its acquisition and formatting is outside the
scope of this document.
The mechanism assumes that a SIP proxy is forwarding SIP requests
that contain the P-AoC header field to an application server that is
delivering the service. The application sever receives the request,
analyzes and process it, and based on the available information
produces the appropriate content and sends it in a separate request
to the user. The application server also forwards the request to its
destination.
4.1.1 Applicability statement of the P-AoC header field
This mechanism is appropriate in environments where a service
provider is collecting charging events related to the establishment
of SIP sessions, subscriptions, messages, and other related SIP
activities. Since SIP systems available in the public Internet will
typically not be subjected to this type of charging, this SIP
extension is not deemed to be of general interest.
4.1.2 Usage of the SIP P-AoC header field
When a User Agent (UA) generates a non-mid dialog request, and the
user wants to receive information about the potential charges
incurred by the SIP event, the UAC inserts a P-AoC header field in
the SIP request with the value set to 'inform'. The presence of this
header field in the request allows the network SIP proxies to route
the SIP request through an application server that can be analyzing
the request, collecting charging information, and generating some
sort of feedback to the user.
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4.1.2.1 Procedures at the UA
A UAC that supports this extension and is willing to receive advice
of charge information related to the request MAY insert a P-AoC
header in a non mid-dialog request (e.g., initial INVITE, initial
SUBSCRIBE, MESSAGE outside a dialog, etc.). The presence of this
header is a request to the network to provide charging information,
if available, although there is not guarantee that the network nodes
are able or willing to honor the request for this information.
In general a User Agent Server (UAS) will not receive requests
containing a P-AoC header field. However, if the service is not
supported by the caller's network, then it is possible that the UAS
receives a SIP request containing a P-AoC header filed. User Agent
Servers that support this extension and receive a request that
contains a P-AoC header field SHOULD ignore the header field.
4.1.2.2 Procedures at a SIP proxy
Generally speaking, SIP proxies that receive a request containing a
P-AoC header field should include the header when the request is
forwarded downstream. Note that this is also the default proxy
behaviour for unknown header fields.
A SIP proxy that receives a request that includes a P-AoC header
field can route the request to an application server for further
analysis and generation of advice of charging information. Besides
that, SIP proxies do not do any other action on the header field.
4.1.2.3 Procedures at an application server
An application server that receives a SIP request that contains a
P-AoC header field MAY analyze the SIP request for the purpose of
collecting charging data. If the service is provided, the
application server SHOULD remove the P-AoC header field from the
request before forwarding downstream. But no matter whether the
service is provided or not the application server MUST forward the
request downstream.
Additionally, the application server can deliver the charging
information to the user, however, the nature and procedures of this
information is outside the scope of this memo.
4.1.3 Syntax of the P-AoC header field
The syntax of the P-AoC header field is described according to the
Augmented Backus-Naur Form (BNF) defined in RFC 2234 [RFC2234] and
extended by RFC 3261 [RFC3261].
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P-Advice-of-Charge = "P-AoC" HCOLON p-aoc-spec *(COMMA p-aoc-spec)
p-aoc-spec = "inform" / token *(SEMI aoc-param)
aoc-param = generic-param
The 'inform' value requests an application server to deliver
information of the potential charges associated with the request, and
at the same time request the application server to proceed processing
the request downstream. Other values or parameters can be added in
the future as needed.
4.1.4 Table of methods
Table 1 shows the occurance of the P-AoC header field in different
SIP methods.
Header field where proxy ACK BYE CAN INV OPT REG
___________________________________________________________
P-AoC R dr - - - o o o
Header field SUB NOT PRA INF UPD MSG REF
___________________________________________________________
P-AoC R o - - - - o o
Table 1: Summary of methods
4.2 Security Considerations
The presence of the P-AoC header in a request does not affect the
treatment of the request, and thus, the actions of rogue proxies that
deliberately insert or remove this header in SIP requests do not have
an action on the session, subscription, message, etc. itself.
4.3 IANA Considerations
This memo requests IANA to include a new P-AoC header field in the
Header Fields subregistry of the Session Initiation Protocol (SIP)
Parameters registry, as follows:
Header Name compact Reference
----------------- ------- ---------
P-AoC [RFCXXXX]
Note to IANA and the RFC Editor: Please replace RFCXXXX with the RFC
number of this memo.
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4.4 Acknowledgements
The author would like to thank the members of the ETSI TISPAN WG3 for
their comments to this memo.
5. References
5.1 Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", RFC 2234, November 1997.
[RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
A., Peterson, J., Sparks, R., Handley, M., and E.
Schooler, "SIP: Session Initiation Protocol", RFC 3261,
June 2002.
5.2 Informative References
[I-D.jesske-sipping-tispan-requirements]
Jesske, R., "Input Requirements for the Session Initiation
Protocol (SIP) in support for the European
Telecommunications Standards Institute (ETSI) Next
Generation Network (NGN) simulation services",
draft-jesske-sipping-tispan-requirements-01 (work in
progress), June 2005.
[I-D.jesske-sipping-tispan-analysis]
Jesske, R., "Analysis of the Input Requirements for the
Session Initiation Protocol (SIP) in support for the
European Telecommunications Standards Institute (ETSI)
Next Generation Networks (NGN) simulation service",
draft-jesske-sipping-tispan-analysis-00 (work in
progress), June 2005.
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Author's Address
Miguel A. Garcia-Martin
Nokia
P.O. Box 407
NOKIA GROUP, FIN 00045
Finland
Phone: +358 50 480 4586
Email: miguel.an.garcia@nokia.com
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