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>
