A Media-Based Traceroute Function for the Session Initiation Protocol (SIP)
draft-ietf-straw-sip-traceroute-03

Approval announcement
Draft of message to be sent after approval:

From: The IESG <iesg-secretary@ietf.org>
To: IETF-Announce <ietf-announce@ietf.org>
Cc: RFC Editor <rfc-editor@rfc-editor.org>,
    straw mailing list <straw@ietf.org>,
    straw chair <straw-chairs@tools.ietf.org>
Subject: Protocol Action: 'A Media-based Traceroute Function for the Session Initiation Protocol (SIP)' to Proposed Standard (draft-ietf-straw-sip-traceroute-03.txt)

The IESG has approved the following document:
- 'A Media-based Traceroute Function for the Session Initiation Protocol
   (SIP)'
  (draft-ietf-straw-sip-traceroute-03.txt) as Proposed Standard

This document is the product of the Sip Traversal Required for
Applications to Work Working Group.

The IESG contact persons are Richard Barnes and Alissa Cooper.

A URL of this Internet Draft is:
http://datatracker.ietf.org/doc/draft-ietf-straw-sip-traceroute/


Technical Summary:

Relevant content can frequently be found in the abstract and/or 
introduction of the document. If not, this may be an indication that 
there are deficiencies in the abstract or introduction.

 In many deployments, the media for SIP-created sessions does not
  flow directly from the originating user's UAC to the answering
  user's UAS.  Often, SIP B2BUAs in the SIP signaling path also insert
  themselves in the media plane path by manipulating SDP, either for
  injecting media such as rich-ringtones or music-on-hold, or for
  relaying media in order to provide functions such as transcoding,
  IPv4-IPv6 conversion, NAT traversal, SRTP termination, media
  steering, etc.

  As more and more SIP domains get deployed and interconnect, the odds
  of a SIP session crossing such media-plane B2BUAs increases, as well
  as the number of such B2BUAs any given SIP session may go through.
  In other words, any given SIP session may cross any number of
  B2BUA's both in the SIP signaling plane as well as media plane.

  If failures or degradation occur in the media plane, it is difficult
  to determine where in the media path they occur.  In order to aid
  managing and troubleshooting SIP-based sessions and media crossing
  such B2BUAs, it would be useful to be able to progressively test the
  media path as it reaches successive B2BUAs with a test controlled in
  a single-ended way from the source UA.  A mechanism to perform
  media-loopback test sessions has been defined in [RFC6849], but it
  cannot be used to directly to test B2BUAs because typically the
  B2BUAs do not have an Address of Record (AoR) to be targeted, nor is
  it known a priori which B2BUAs will be crossed for any given
  session.

  For example, suppose calls from Alice to Bob have media problems.
  Alice would like to test the media path to each B2BUA in the path to
  Bob separately, to determine which segment has the issues.  Alice
  cannot target the B2BUAs directly for each test call, because she
  doesn't know what URIs to use to target them; nor would using such
  URIs guarantee the same media path be used as a call to Bob.  A
  better solution would be to make a test call targeted to Bob, but
  with a SIP traceroute-type mechanism that makes the call terminate
  at the B2BUAs, such that she can perform test sessions to test the
  media path to each downstream B2BUA.

  This document defines how such a mechanism can be employed, using
  the [RFC6849] mechanism along with the Max-Forwards SIP header field
  such that a SIP User Agent can make multiple test calls, each
  reaching a B2BUA further downstream.  Each B2BUA in the path that
  supports the mechanism in [RFC6849] would answer the media-loopback
  call, and thus the originating SIP UA can test the media path up to
  that B2BUA.


Working Group Summary:

Was there anything in WG process that is worth noting? For example, was 
there controversy about particular points or were there decisions where 
the consensus was particularly rough?

  The WG path of this document was reasonably short and efficient.
  Several technical comments were made during reviews and all were 
  resolved with consensus.

  There is consensus in the STRAW WG to publish this document.


Document Quality:

Are there existing implementations of the protocol? Have a significant 
number of vendors indicated their plan to implement the specification?

Are there any reviewers that merit special mention as having done a 
thorough review, e.g., one that resulted in important changes or a 
conclusion that the document had no substantive issues? If there was a 
MIB Doctor, Media Type or other expert review, what was its course 
(briefly)? In the case of a Media Type review, on what date was the 
request posted?


  The guidelines and procedures in the document is based on input  and 
  experience from the implementer community.


Personnel:

Who is the Document Shepherd?

  Victor Pascual (victor.pascual.avila@gmail.com -- STRAW WG co-chair)

Who is the Responsible Area Director?

  Richard Barnes <rlb@ipv.sx>