| TOC |
|
By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79.
Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as “work in progress.”
The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html.
This Internet-Draft will expire on July 13, 2008.
Copyright © The IETF Trust (2008).
The current "request URI rewriting" technique of routing SIP requests makes support of several desired uses of SIP problematic. This document is to discuss these problems and suggest a direction in which to proceed toward solutions.
1.
Introduction
2.
Problem Use Cases
2.1.
"Where did this come from?"
2.2.
Subaddressing
2.3.
Emergency Services
3.
Security Considerations
4.
Revision History
4.1.
draft-worley-address-route-00
5.
Informative References
§
Author's Address
§
Intellectual Property and Copyright Statements
| TOC |
The problems surrounding "request URI rewriting" are common and are likely to become more intense. In the PSTN, there are a small number of fairly well-controlled ways that calls can be forwarded, routed, and redirected. SIP is more flexible, allowing nearly arbitrary address manipulation by all SIP agents. Quite a number of different rewriting operations are present in the small-to-medium organization PBX system that the author's company produces, and we can expect that as people become more familiar with the possibilities, rewriting will become as routinely complex as e-mail forwarding is now. For example, a recent message to the IETF SIP mailing list contained the following Received headers:
Received: from localhost (dragon.ariadne.com [127.0.0.1])
by dragon.ariadne.com (8.12.8/8.12.8) with ESMTP id m0AFA507018184
for <worley@localhost>; Thu, 10 Jan 2008 10:10:05 -0500
Received: from mail.g.comcast.net [216.148.227.80]
by localhost with POP3 (fetchmail-6.2.0)
for worley@localhost (single-drop); Thu, 10 Jan 2008 10:10:05 -0500 (EST)
Received: from imta21.emeryville.ca.mail.comcast.net ([76.96.30.31])
by sccrmxc16.comcast.net (sccrmxc16) with ESMTP
id <20080110150359s1600jigc6e>; Thu, 10 Jan 2008 15:03:59 +0000
Received: from megatron.ietf.org ([156.154.16.145])
by IMTA21.emeryville.ca.mail.comcast.net with comcast
id bT3y1Y00d37nXEc0M00000; Thu, 10 Jan 2008 15:03:59 +0000
Received: from [127.0.0.1] (helo=stiedprmman1.va.neustar.com)
by megatron.ietf.org with esmtp (Exim 4.43)
id 1JCywW-0008B8-3E; Thu, 10 Jan 2008 10:03:40 -0500
Received: from sip by megatron.ietf.org with local (Exim 4.43)
id 1JCywV-0008B1-40
for sip-confirm+ok@megatron.ietf.org; Thu, 10 Jan 2008 10:03:39 -0500
Received: from [10.91.34.44] (helo=ietf-mx.ietf.org)
by megatron.ietf.org with esmtp (Exim 4.43) id 1JCywU-0008As-QR
for sip@ietf.org; Thu, 10 Jan 2008 10:03:38 -0500
Received: from rtp-iport-2.cisco.com ([64.102.122.149])
by ietf-mx.ietf.org with esmtp (Exim 4.43) id 1JCywT-0000Gu-Vl
for sip@ietf.org; Thu, 10 Jan 2008 10:03:38 -0500
Received: from rtp-dkim-1.cisco.com ([64.102.121.158])
by rtp-iport-2.cisco.com with ESMTP; 10 Jan 2008 10:03:38 -0500
Received: from rtp-core-2.cisco.com (rtp-core-2.cisco.com [64.102.124.13])
by rtp-dkim-1.cisco.com (8.12.11/8.12.11) with ESMTP id m0AF3bXs026778;
Thu, 10 Jan 2008 10:03:37 -0500
Received: from xbh-rtp-211.amer.cisco.com (xbh-rtp-211.cisco.com
[64.102.31.102])
by rtp-core-2.cisco.com (8.12.10/8.12.6) with ESMTP id m0AF3apm000195;
Thu, 10 Jan 2008 15:03:37 GMT
Received: from xfe-rtp-202.amer.cisco.com ([64.102.31.21]) by
xbh-rtp-211.amer.cisco.com with Microsoft SMTPSVC(6.0.3790.1830);
Thu, 10 Jan 2008 10:03:31 -0500
Received: from [161.44.174.128] ([161.44.174.128]) by
xfe-rtp-202.amer.cisco.com with Microsoft SMTPSVC(6.0.3790.1830);
Thu, 10 Jan 2008 10:03:31 -0500
That is 13 routing decisions that were considered important enough by the SMTP agent to log it.
| TOC |
Jonathan's "UA Loose Routing I-D[1] (Rosenberg, J., “Applying Loose Routing to Session Initiation Protocol (SIP) User Agents (A),” June 2007.) provides a number of use cases or problems to be solved. Many of these cases are fundamentally the same, so we here divide them into groups.
| TOC |
In a number of situations, the UA that receives a request requires more information about how the request was addressed to itself than is provided by the request-URI. (Or more than can be easily represented in the request-URI by present techniques.)
| TOC |
A number of situations are forms of subaddressing, where an "authority" issues an AOR to a user or user agent, which in turn wants to create a series of "subaddresses". The subaddresses are required to all route to the user agent, but the user agent desires to be able to determine which subaddress was used in the original request.
(We assume that the authority prescribes the method by which the subaddresses are constructed from the AOR, but that the authority has no knowledge of which specific subaddresses have been constructed prior to their appearance in a request to be routed.)
| TOC |
To quote from [1] (Rosenberg, J., “Applying Loose Routing to Session Initiation Protocol (SIP) User Agents (A),” June 2007.):
A key requirement of systems supporting emergency calling is that the SIP INVITE request for an emergency call be 'marked' in some way that makes it clear that it is an emergency call, so that it can receive priority treatment [7]. However, such a marking needs to be done in a way that it cannot be abused by attackers seeking to get special treatment for non- emergency calls. The solution for this is that the marking needs to be the target address of the request itself, which would unambiguously identify an emergency services call taker as the target.
| TOC |
Security issues have not been considered.
| TOC |
| TOC |
First version.
| TOC |
| [1] | Rosenberg, J., “Applying Loose Routing to Session Initiation Protocol (SIP) User Agents (A),” I-D draft-rosenberg-sip-ua-loose-route-01, June 2007. |
| TOC |
| Dale R. Worley | |
| Pingtel Corp. | |
| 10 North Ave. | |
| Burlington, MA 01803 | |
| US | |
| Phone: | +1 781 229 0533 x173 |
| Email: | dworley@pingtel.com |
| URI: | http://www.pingtel.com |
| TOC |
The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79.
Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr.
The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf-ipr@ietf.org.
This document and the information contained herein are provided on an “AS IS” basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Copyright © The IETF Trust (2008). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights.
Funding for the RFC Editor function is currently provided by the Internet Society.