Private Extensions to the Session Initiation Protocol (SIP) for Asserted Identity within Trusted Networks
RFC 3325

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Network Working Group                                        C. Jennings
Request for Comments: 3325                                 Cisco Systems
Category: Informational                                      J. Peterson
                                                           NeuStar, Inc.
                                                               M. Watson
                                                         Nortel Networks
                                                           November 2002

    Private Extensions to the Session Initiation Protocol (SIP) for
               Asserted Identity within Trusted Networks

Status of this Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2002).  All Rights Reserved.

Abstract

   This document describes private extensions to the Session Initiation
   Protocol (SIP) that enable a network of trusted SIP servers to assert
   the identity of authenticated users, and the application of existing
   privacy mechanisms to the identity problem.  The use of these
   extensions is only applicable inside an administrative domain with
   previously agreed-upon policies for generation, transport and usage
   of such information.  This document does NOT offer a general privacy
   or identity model suitable for use between different trust domains,
   or use in the Internet at large.

Table of Contents

   1.   Applicability Statement  . . . . . . . . . . . . . . . . . .   2
   2.   Conventions  . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.   Introduction . . . . . . . . . . . . . . . . . . . . . . . .   4
   4.   Overview . . . . . . . . . . . . . . . . . . . . . . . . . .   5
   5.   Proxy Behavior . . . . . . . . . . . . . . . . . . . . . . .   5
   6.   Hints for Multiple Identities  . . . . . . . . . . . . . . .   6
   7.   Requesting Privacy . . . . . . . . . . . . . . . . . . . . .   6
   8.   User Agent Server Behavior . . . . . . . . . . . . . . . . .   7
   9.   Formal Syntax  . . . . . . . . . . . . . . . . . . . . . . .   7
        9.1  The P-Asserted-Identity Header  . . . . . . . . . . . .   8
        9.2  The P-Preferred-Identity Header . . . . . . . . . . . .   8
        9.3  The "id" Privacy Type . . . . . . . . . . . . . . . . .   9

Jennings, et. al.            Informational                      [Page 1]
RFC 3325                 SIP Asserted Identity             November 2002

   10.  Examples . . . . . . . . . . . . . . . . . . . . . . . . . .   9
        10.1 Network Asserted Identity passed to trusted gateway . .   9
        10.2 Network Asserted Identity Withheld  . . . . . . . . . .  11
   11.  Example of Spec(T) . . . . . . . . . . . . . . . . . . . . .  13
   12.  Security Considerations  . . . . . . . . . . . . . . . . . .  14
   13.  IANA Considerations  . . . . . . . . . . . . . . . . . . . .  14
        13.1 Registration of new SIP header fields . . . . . . . . .  14
        13.2 Registration of "id" privacy type for SIP Privacy header 15
   14.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . .  15
        Normative References . . . . . . . . . . . . . . . . . . . .  15
        Informational References . . . . . . . . . . . . . . . . . .  16
        Authors' Addresses . . . . . . . . . . . . . . . . . . . . .  17
        Full Copyright Statement . . . . . . . . . . . . . . . . . .  18

1. Applicability Statement

   This document describes private extensions to SIP [1] that enable a
   network of trusted SIP servers to assert the identity of end users or
   end systems, and to convey indications of end-user requested privacy.
   The use of these extensions is only applicable inside a 'Trust
   Domain' as defined in Short term requirements for Network Asserted
   Identity [5].  Nodes in such a Trust Domain are explicitly trusted by
   its users and end-systems to publicly assert the identity of each
   party, and to be responsible for withholding that identity outside of
   the Trust Domain when privacy is requested.  The means by which the
   network determines the identity to assert is outside the scope of
   this document (though it commonly entails some form of
   authentication).

   A key requirement of [5] is that the behavior of all nodes within a
   given Trust Domain 'T' is known to comply to a certain set of
   specifications known as 'Spec(T)'.  Spec(T) MUST specify behavior for
   the following:

   1. The manner in which users are authenticated

   2. The mechanisms used to secure the communication among nodes within
      the Trust Domain

   3. The mechanisms used to secure the communication between UAs and
      nodes within the Trust Domain

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RFC 3325                 SIP Asserted Identity             November 2002

   4. The manner used to determine which hosts are part of the Trust