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Straw Status Pages

Sip Traversal Required for Applications to Work (Concluded WG)
Art Area: Francesca Palombini, Murray Kucherawy | 2012-Jun-04 — 2017-Mar-17 

2016-04-07 charter

Sip Traversal Required for Applications to Work (straw)


 Current Status: Active

     Christer Holmberg <christer.holmberg@ericsson.com>
     Victor Pascual <victor.pascual.avila@gmail.com>

 Applications and Real-Time Area Directors:
     Ben Campbell <ben@nostrum.com>
     Alissa Cooper <alissa@cooperw.in>
     Alexey Melnikov <aamelnikov@fastmail.fm>

 Applications and Real-Time Area Advisor:
     Ben Campbell <ben@nostrum.com>

 Mailing Lists:
     General Discussion: straw@ietf.org
     To Subscribe:       https://www.ietf.org/mailman/listinfo/straw
     Archive:            https://mailarchive.ietf.org/arch/browse/straw/

Description of Working Group:

  Problem Statement:

  Within the context of the SIP protocol and architecture, a
  Back-to-Back User Agent (B2BUA) is any SIP device in the logical path
  between two User Agents performing a role beyond that of a Proxy as
  defined in RFC 3261.  The B2BUA may be as simple as a session-stateful
  Proxy becoming a B2BUA in order to terminate dead sessions by
  generating BYEs; or it may be a 3PCC-style agent only modifying SDP;
  or it may be a Session Border Controller performing such functions as
  in RFC 5853; or it may be an Enterprise PBX terminating REFERs and
  such; or it may be a complete UAS and UAC implementation with a PRI
  (Primary Rate Interface) loopback in-between.

  In its most extreme form, the scope of the SIP protocol ends at the
  UAS of the B2BUA, and a new SIP protocol scope begins on its UAC side.
  In practice, however, users expect some SIP protocol aspects to go
  beyond the scope of the B2BUA's UAS side, and be traversed onto its
  UAC side, as if the B2BUA was not an end unto itself; this is similar
  to the expectation that emails work when they cross from POP and IMAP
  to/from SMTP.

  It is impossible to normatively define all the behaviors of B2BUAs in
  general, or even subsets of them such as SBCs (Session Border
  Controlers)or PBXs (Private Branch Exchanges). Unlike consumer NATs,
  B2BUAs perform widely varying functions for purposes which may be
  unique to their environment, unique to their architecture, or unique
  to the wishes of their administrator.  Instead of defining all things
  a given type of B2BUA must do, a more practical objective would be to
  define what very few things any B2BUA must do to make a specific SIP
  mechanism work, and let the market decide whether to do those things.

  The name of this working group reflects that practical objective: if
  there were a thin straw between the SIP UAS and UAC of a B2BUA, what
  must be passed through that straw and used on each side.  Or viewed
  another way, if a B2BUA were in fact a UAS and UAC connected with a
  PRI loopback circuit, and if we could extend ISDN, what information
  would we carry in ISDN across the PRI for a specific SIP mechanism to
  work end-to-end.

  For example, the WG could produce a document which specifies that the
  Max-Forwards header field value should be copied and decremented
  across the B2BUA, if the B2BUA wishes to prevent infinite
  loops. Administrators could then tell their B2BUA vendors to comply
  with the document, if the administrator so wishes.


  The objectives of the STRAW Working Group are to publish normative
  documents which define which SIP header fields, parameters, MIME
  bodies, body content fields/information, or media-plane
  characteristics are required to traverse between the User Agent
  "sides" of a B2BUA for specific functions to work.

  The specific functions covered are expected to relate to
  already-published RFCs or existing RAI area work, as opposed to all
  future IETF work.  In other words, the Working Group is not meant to
  be a never-ending source for B2BUA requirements in the RAI area.

  Deliverables would indicate which types of B2BUAs would apply or not.
  For example, a document defining the requirements for end-to-end
  DTLS-SRTP would not apply to B2BUAs which terminate media, such as
  transcoders or recorders.

Goals and Milestones:
  Dec 2012 - A taxonomy document defining role-types of B2BUAs, as a reference for other deliverables submitted to the IESG as Informational
  Apr 2013 - A document defining the requirements for B2BUAs with respect to loop detection/prevention submitted to the IESG as PS
  Aug 2013 - A document defining the requirements for B2BUAs to support end-to-end and hop-by-hop media-loopback test calls submitted to the IESG as PS
  Dec 2013 - A document defining the requirements for B2BUAs to support DTLS-SRTP (RFC 5764) end-to-end submitted to the IESG as PS
  Dec 2013 - A document defining the requirements for B2BUAs to support STUN message transactions end-to-end submitted to the IESG as PS
  Dec 2013 - A document defining the requirements for B2BUAs to support RTCP end-to-end submitted to the IESG as PS

All charter page changes, including changes to draft-list, rfc-list and milestones:

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