Requirements for Multiple Address of Record (AOR) Reachability Information in the Session Initiation Protocol (SIP)
RFC 5947
Internet Engineering Task Force (IETF) J. Elwell
Request for Comments: 5947 Siemens Enterprise Communications
Category: Informational H. Kaplan
ISSN: 2070-1721 Acme Packet
September 2010
Requirements for Multiple Address of Record (AOR) Reachability
Information in the Session Initiation Protocol (SIP)
Abstract
This document states requirements for a standardized SIP registration
mechanism for multiple addresses of record (AORs), the mechanism
being suitable for deployment by SIP service providers on a large
scale in support of small to medium sized Private Branch Exchanges
(PBXs). The requirements are for a solution that can, as a minimum,
support AORs based on E.164 numbers.
Status of This Memo
This document is not an Internet Standards Track specification; it is
published for informational purposes.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Not all documents
approved by the IESG are a candidate for any level of Internet
Standard; see Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc5947.
Elwell & Kaplan Informational [Page 1]
RFC 5947 Multiple AOR reachability in SIP September 2010
Copyright Notice
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Table of Contents
1. Introduction ....................................................3
2. Terminology .....................................................3
3. Problem Statement ...............................................4
3.1. Issues with the REGISTER Transaction .......................5
3.1.1. Mishandling by SIP-Aware Middleboxes ................5
3.1.2. REGISTER Response Growth ............................6
3.1.3. Illegal "Wildcard" Syntax ...........................6
3.2. Issues with Routing Inbound Requests to the SIP-PBX ........6
3.2.1. Loss of Target Information ..........................6
3.2.2. Inconsistent Placement of Target URI
Information in Inbound Requests .....................6
3.2.3. Request-URI Misrouting ..............................7
3.3. Policy-Related Issues ......................................7
3.3.1. Authorization Policy Mismatches .....................7
3.3.2. PAI or PPI URI Mismatches ...........................7
4. Requirements ....................................................8
5. Desirables .....................................................10
6. Non-Requirements ...............................................11
7. Security considerations ........................................11
8. Acknowledgements ...............................................12
9. References .....................................................12
9.1. Normative References ......................................12
9.2. Informative References ....................................12
Elwell & Kaplan Informational [Page 2]
RFC 5947 Multiple AOR reachability in SIP September 2010
1. Introduction
The Session Initiation Protocol (SIP) [RFC3261], together with its
extensions, supports multiple means of obtaining the connection
information necessary to deliver out-of-dialog SIP requests to their
intended targets. When a SIP proxy needs to send a request to a
target address of record (AOR) within its domain, it can use a
location service to obtain the registered Contact Universal Resource
Identifiers (URIs), together with any associated path information
[RFC3327], and build a route set to reach each target user agent
(UA). The SIP REGISTER method can be used to register Contact URIs
and path information. SIP-outbound [RFC5626] enhances this mechanism
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