draft-kyzivat-clue-telemedical-callflow-01
slides-interim-2012-clue-3-7-1

Meeting Slides ControLling mUltiple streams for tElepresence (clue) WG
Title draft-kyzivat-clue-telemedical-callflow-01
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Last updated 2012-09-20

Meeting Slides
slides-interim-2012-clue-3-7

   


CLUE                                                          P. Kyzivat
Internet-Draft                                        September 20, 2012
Intended status: Informational
Expires: March 24, 2013


                   CLUE Telemedical Use Case Callflow
               draft-kyzivat-clue-telemedical-callflow-01

Abstract

   This is the beginning of an example call flow for an instantiation of
   the use case described in the telemedical use case
   [I-D.xiao-clue-telemedical-use-case].  More detail will be added
   later.

Status of this Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
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   Internet-Drafts are draft documents valid for a maximum of six months
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   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on March 24, 2013.

Copyright Notice

   Copyright (c) 2012 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.




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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
   2.  Scenario being illustrated  . . . . . . . . . . . . . . . . . . 3
   3.  Proposed Relationship of O/A to CLUE messages . . . . . . . . . 3
   4.  Ladder Diagram  . . . . . . . . . . . . . . . . . . . . . . . . 4
     4.1.  Comments  . . . . . . . . . . . . . . . . . . . . . . . . . 8
   5.  Message Bodies  . . . . . . . . . . . . . . . . . . . . . . . . 8
   6.  TO-DO list  . . . . . . . . . . . . . . . . . . . . . . . . . . 8
   7.  Change Log  . . . . . . . . . . . . . . . . . . . . . . . . . . 9
   8.  Security Considerations . . . . . . . . . . . . . . . . . . . . 9
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 9
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . . . 9
     10.1. Normative References  . . . . . . . . . . . . . . . . . . . 9
     10.2. Informative References  . . . . . . . . . . . . . . . . . . 9
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . . . 9



































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1.  Introduction

   This is a first cut at the call flow.  So far it only includes the
   ladder diagram showing the exchange of SIP and CLUE messages.  The
   content of those messages will be added later.  Before doing that it
   will be useful to agree on at least one acceptable sequence of
   messages to realize this use case.


2.  Scenario being illustrated

   The case considered here consists of one surgery room, one remote
   expert, and one remote classroom, connected by an MCU.  The classroom
   connects first and waits until the surgery begins.  The surgery room
   connects second.  At that point the classroom and surgery are joined
   by the MCU.  The expert joins last.


3.  Proposed Relationship of O/A to CLUE messages

   The call flow is constructted in accord with this proposed approach
   for ordering messages.
   o  What media is sent at any time is determined by the most recently
      received valid config message, constrained by most recent O/A.
      *  When constraint is bandwidth, sender decides what to drop.
      *  A new O/A can make it possible to send more (or less) of the
         current config.
   o  An O/A should be consistent with the most recent advertisement in
      each direction.
      *  This gives context to understand why to accept what is offered.
         (The answerer has no motivation to accept things that aren't.)
   o  A config message always explicitly refers to an advertisement.
      *  It is invalid, and will be rejected, if it doesn't refer to the
         most recently sent advertisement.  (This implies there is a
         message to NACK a config msg.)
   o  Typically the endpoint that sends the config message makes an
      offer to enable it.
      *  This end is the first to know what is needed to support the
         config.
      *  It is also the end that cares.
      *  Can be before or after the config, or both.
      *  Must accommodate the most recent config received from the other
         side.
      *  But either side may send an O/A at any time for whatever
         reason, or may send an offerless INVITE to solicit an offer.
         (This is basic SIP.)





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   o  Require a config message in response to each advertisement.
      *  Ensures no need for continued support of old advertisement.
      *  Until a new config is received, sender of the advertisement may
         cease sending media that aren't consistent with the new
         advertisement.
   o  During call major changes requiring O/A will typically happen
      independently at each endpoint.
      *  But at start of call there will be an exchange of
         advertisements and configs.
      *  We want to avoid unnecessary O/As in this case.
   o  If receive an advertisement after sending one, before receiving a
      config:
      *  Should send config before initiating O/A.
      *  If receive offer before sending one, it will typically be
         sufficient to accommodate your config.
      *  If so, won't need to initiate another O/A.
      *  There may still be glare at SIP level.  Use standard SIP
         remedies for that.
      *  If so, the O/A that glared may not need to be retried.
   o  First O/A of session occurs before any advertisements or
      configurations.
      *  Must include the CLUE channel.
      *  Everything else is speculative until advertisements are
         exchanged.
      *  May be best guess at what is needed, or placeholder intended to
         maximize interop with arbitrary devices.
      *  Before the first config is received, there should be at most a
         single capture, chosen by sender, per RTP session.


4.  Ladder Diagram

          Surgery          MCU          Expert        Classroom
             |              |              |              |
             |              |              |              |
             |              |              |              |
             |              |              |              |(1)
             |              |              |              |
             |INVITE        |              |              |
             |(offer basic  |              |              |
             | audio&video&clue channels)  |              |
             |------------->|              |              |
             |              |              |              |
             |200 OK        |              |              |
             |<-------------|              |              |
             |              |              |              |
             |basic audio   |              |              |
             |..............|              |              |



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             |              |              |              |
             |basic video   |              |              |
             |..............|              |              |
             |              |              |              |
             |CLUE channel  |              |              |
             |..............|              |              |
             |              |              |              |
             |Advertisement |              |              |
             |------------->|              |              |
             |Advertisement |              |              |
             |(Startup capture)            |              |
             |<-------------|              |              |
             |Configure     |              |              |
             |("empty" - request nothing)  |              |
             |<-------------|              |              |
             |              |              |              |
             |Configure     |              |              |
             |------------->|              |              |
             |INVITE        |              |              |
             |(to cover both configurations)              |
             |------------->|              |              |
             |              |              |              |
             |200 OK        |              |              |
             |<-------------|              |              |
             |              |              |              |
             |startup audio |              |              |
             |..............|              |              |
             |              |              |              |
             |startup video |              |              |
             |..............|              |              |
             |              |              |              |
             |CLUE channel  |              |              |
             |..............|              |              |
             |              |              |              |
             |              |              |              |(2)
             |              |              |              |
             |              |INVITE        |              |
             |              |(offer basic  |              |
             |              | audio&video&clue channels)  |
             |              |<-------------|              |
             |              |              |              |
             |              |200 OK        |              |
             |              |------------->|              |
             |              |              |              |
             |              |basic audio   |              |
             |              |..............|              |
             |              |              |              |
             |              |basic video   |              |



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             |              |..............|              |
             |              |              |              |
             |              |CLUE channel  |              |
             |              |..............|              |
             |              |              |              |
             |              |Advertisement |              |
             |              |<-------------|              |
             |Advertisement |              |              |
             |(from expert) |              |              |
             |<-------------|              |              |
             |              |Advertisement |              |
             |              |(from surgery)|              |
             |              |------------->|              |
             |INVITE        |              |              |
             |(prep for config)            |              |
             |------------->|              |              |
             |              |INVITE        |              |
             |              |(prep for config)            |
             |              |<-------------|              |
             |              |              |              |
             |200 OK        |              |              |
             |<-------------|              |              |
             |              |              |              |
             |              |200 OK        |              |
             |              |------------->|              |
             |Configure     |              |              |
             |(accept       |              |              |
             | expert input)|              |              |
             |------------->|              |              |
             |              |Configure     |              |
             |              |(accept input |              |
             |              | from surgery)|              |
             |              |<-------------|              |
             |              |              |              |
             |video from expert            |              |
             |..............|              |              |
             |              |              |              |
             |audio from expert            |              |
             |..............|              |              |
             |              |              |              |
             |              |video from surgery           |
             |              |..............|              |
             |              |              |              |
             |              |audio from surgery           |
             |              |..............|              |
             |(with luck maybe we don't need              |
             | another OA for the reverse flow)           |
             |              |              |              |



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             |              |Configure     |              |
             |              |(from surgery)|              |
             |              |------------->|              |
             |Configure     |              |              |
             |(from expert) |              |              |
             |<-------------|              |              |
             |              |              |              |
             |2-way video   |              |              |
             |..............|              |              |
             |              |              |              |
             |2-way audio   |              |              |
             |..............|              |              |
             |              |              |              |
             |              |2-way video   |              |
             |              |..............|              |
             |              |              |              |
             |              |2-way audio   |              |
             |              |..............|              |
             |              |              |              |
             |              |              |              |(3)
             |              |              |              |
             |              |INVITE        |              |
             |              |(offer basic  |              |
             |              | audio&video&clue channels)  |
             |              |<----------------------------|
             |              |              |              |
             |              |200 OK        |              |
             |              |---------------------------->|
             |              |              |              |
             |              |basic audio   |              |
             |              |.............................|
             |              |              |              |
             |              |basic video   |              |
             |              |.............................|
             |              |              |              |
             |              |CLUE channel  |              |
             |              |.............................|
             |              |              |              |
             |              |Advertisement |              |
             |              |<----------------------------|
             |              |Advertisement |              |
             |              |(surgery+expert)             |
             |              |---------------------------->|
             |              |Configure     |              |
             |              |("empty" - request nothing)  |
             |              |---------------------------->|
             |              |INVITE        |              |
             |              |(prep for config)            |



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             |              |<----------------------------|
             |              |              |              |
             |              |200 OK        |              |
             |              |---------------------------->|
             |              |Configure     |              |
             |              |(accept surgery+expert)      |
             |              |<----------------------------|
             |              |              |              |
             |              |video from surgery & expert  |
             |              |.............................|
             |              |              |              |
             |              |audio from surgery & expert  |
             |              |.............................|
             |              |              |              |
             |              |              |              |(4)
             |              |              |              |
             |Surgery & expert don't see classroom        |
             |for now assume MCU enforces this by         |
             |not advertising classroom to them.          |
             |              |              |              |
             |              |              |              |
             |              |              |              |
             |              |              |              |

4.1.  Comments

   There are some issues with the ladder diagram above due to the tool
   I've used to generate it.  The CLUE messages are shown with "--->"
   rather than "...>" because the tool can't do the latter.


5.  Message Bodies


6.  TO-DO list
   o  Reference [I-D.westerlund-avtcore-max-ssrc] in the initial offer
      proposing how many RTP streams can be sent and received
      simultaneously in the offered RTP session.

      For example the offerer can send up to 6 RTP streams and receive
      up to 4.  This will help with providing a better advertisements
      from both sides:

        m=video 49200 RTP/AVP 99
        a=rtpmap:99 H264/90000
        a=max-send-ssrc:{*:6}
        a=max-recv-ssrc:{*:4}




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7.  Change Log
   1.  Captured suggestion from Roni in a TODO list for later.  And made
       a number of adjustments/cleanups to the diagram.  Incorporated a
       comment from Espen for the MCU to send "empty" configuration
       initially, and about a missing config message.

       Reworked to incorporate and follow the approach I proposed on the
       first day of the interim.


8.  Security Considerations

   TBS


9.  IANA Considerations

   This specification ha no IANA considerations


10.  References

10.1.  Normative References

   [RFC3261]  Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
              A., Peterson, J., Sparks, R., Handley, M., and E.
              Schooler, "SIP: Session Initiation Protocol", RFC 3261,
              June 2002.

   [I-D.xiao-clue-telemedical-use-case]
              Xiao, L. and R. Even, "Use Case for Telemedical with
              Multi-streams", draft-xiao-clue-telemedical-use-case-00
              (work in progress), July 2012.

   [I-D.westerlund-avtcore-max-ssrc]
              Westerlund, M., Burman, B., and F. Jansson, "Multiple
              Synchronization sources (SSRC) in RTP Session Signaling",
              draft-westerlund-avtcore-max-ssrc-02 (work in progress),
              July 2012.

10.2.  Informative References










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Author's Address

   Paul H. Kyzivat

   Email: pkyzivat@alum.mit.edu














































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