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Versions: (draft-romanow-clue-telepresence-requirements) 00 01 02 03 04 05 06 07 RFC 7262

CLUE WG                                                       A. Romanow
Internet-Draft                                             Cisco Systems
Intended status: Informational                                 S. Botzko
Expires: June 15, 2014                                         M. Barnes
                                                                 Polycom
                                                       December 12, 2013


              Requirements for Telepresence Multi-Streams
            draft-ietf-clue-telepresence-requirements-07.txt

Abstract

   This memo discusses the requirements for specifications, that enable
   telepresence interoperability by describing behaviors and protocols
   for Controlling Multiple Streams for Telepresence (CLUE).  In
   addition, the problem statement and related definitions are also
   covered herein.

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
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   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."

   This Internet-Draft will expire on June 15, 2014.

Copyright Notice

   Copyright (c) 2013 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
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of



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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  4
   3.  Definitions  . . . . . . . . . . . . . . . . . . . . . . . . .  4
   4.  Problem Statement  . . . . . . . . . . . . . . . . . . . . . .  5
   5.  Requirements . . . . . . . . . . . . . . . . . . . . . . . . .  7
   6.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 10
   7.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 10
   8.  Security Considerations  . . . . . . . . . . . . . . . . . . . 11
   9.  Informative References . . . . . . . . . . . . . . . . . . . . 11
   Appendix A.  Changes From Earlier Versions . . . . . . . . . . . . 12
     A.1.  Changes from draft -06 . . . . . . . . . . . . . . . . . . 12
     A.2.  Changes from draft -05 . . . . . . . . . . . . . . . . . . 12
     A.3.  Changes from draft -04 . . . . . . . . . . . . . . . . . . 13
     A.4.  Changes from draft -03 . . . . . . . . . . . . . . . . . . 13
     A.5.  Changes from draft -02 . . . . . . . . . . . . . . . . . . 13
     A.6.  Changes from draft -01 . . . . . . . . . . . . . . . . . . 13
     A.7.  Changes From Draft -00 . . . . . . . . . . . . . . . . . . 13
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 14



























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1.  Introduction

   Telepresence systems greatly improve collaboration.  In a
   telepresence conference (as used herein), the goal is to create an
   environment that gives the users a feeling of (co-located) presence -
   the feeling that a local user is in the same room with other local
   users and the remote parties.  Currently, systems from different
   vendors often do not interoperate because they do the same tasks
   differently, as discussed in the Problem Statement section below.

   The approach taken in this memo is to set requirements for a future
   specification(s) that, when fulfilled by an implementation of the
   specification(s), provide for interoperability between IETF protocol
   based telepresence systems.  It is anticipated that a solution for
   the requirements set out in this memo likely involves the exchange of
   adequate information about participating sites; information that is
   currently not standardized by the IETF.

   The purpose of this document is to describe the requirements for a
   specification that enables interworking between different SIP-based
   [RFC3261] telepresence systems, by exchanging and negotiating
   appropriate information.  In the context of the requirements in this
   document and related solution documents, this includes both point to
   point SIP sessions as well as SIP based conferences as described in
   the SIP conferencing framework [RFC4353] and the SIP based conference
   control [RFC4579] specifications.  Non IETF protocol based systems,
   such as those based on ITU-T Rec. H.323, are out of scope.  These
   requirements are for the specification, they are not requirements on
   the telepresence systems implementing the solution/protocol that will
   be specified.

   Telepresence systems of different vendors, today, can follow
   radically different architectural approaches while offering a similar
   user experience.  CLUE will not dictate telepresence architectural
   and implementation choices; however it will describe a protocol
   architecture for CLUE and how it relates to other protocols.  CLUE
   enables interoperability between telepresence systems by exchanging
   information about the systems' characteristics.  Systems can use this
   information to control their behavior to allow for interoperability
   between those systems.

   A telepresence session requires at least one sending and one
   receiving endpoint.  Multiparty telepresence sessions include more
   than two endpoints, and centralized infrastructure such as Multipoint
   Control Units (MCUs) or equivalent.  CLUE specifies the syntax,
   semantics, and control flow of information to enable the best
   possible user experience at those endpoints.




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   Sending endpoints, or MCUs, are not mandated to use any of the CLUE
   specifications that describe their capabilities, attributes, or
   behavior.  Similarly, it is not envisioned that endpoints or MCUs
   must ever take into account information received.  However, by making
   available as much information as possible, and by taking into account
   as much information as has been received or exchanged, MCUs and
   endpoints are expected to select operation modes that enable the best
   possible user experience under their constraints.

   The document structure is as follows: Definitions are set out,
   followed by a description of the problem of telepresence
   interoperability that led to this work.  Then the requirements to a
   specification addressing the current shortcomings are enumerated and
   discussed.


2.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119].


3.  Definitions

   The following terms are used throughout this document and serve as
   reference for other documents.

      Audio Mixing: refers to the accumulation of scaled audio signals
      to produce a single audio stream.  See RTP Topologies, [RFC5117].

      Conference: used as defined in [RFC4353], A Framework for
      Conferencing within the Session Initiation Protocol (SIP).

      Endpoint: The logical point of final termination through
      receiving, decoding and rendering, and/or initiation through
      capturing, encoding, and sending of media streams.  An endpoint
      consists of one or more physical devices which source and sink
      media streams, and exactly one [RFC4353] Participant (which, in
      turn, includes exactly one SIP User Agent).  In contrast to an
      endpoint, an MCU may also send and receive media streams, but it
      is not the initiator nor the final terminator in the sense that
      Media is Captured or Rendered.  Endpoints can be anything from
      multiscreen/multicamera rooms to handheld devices.







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      Endpoint Characteristics: include placement of Capture and
      Rendering Devices, capture/render angle, resolution of cameras and
      screens, spatial location and mixing parameters of microphones.
      Endpoint characteristics are not specific to individual media
      streams sent by the endpoint.

      Layout: How rendered media streams are spatially arranged with
      respect to each other on a single screen/mono audio telepresence
      endpoint, and how rendered media streams are arranged with respect
      to each other on a multiple screen/speaker telepresence endpoint.
      Note that audio as well as video is encompassed by the term
      layout--in other words, included is the placement of audio streams
      on speakers as well as video streams on video screens.

      Local: Sender and/or receiver physically co-located ("local") in
      the context of the discussion.

      MCU: Multipoint Control Unit (MCU) - a device that connects two or
      more endpoints together into one single multimedia conference
      [RFC5117].  An MCU may include a Mixer [RFC4353].

      Media: Any data that, after suitable encoding, can be conveyed
      over RTP, including audio, video or timed text.

      Model: a set of assumptions a telepresence system of a given
      vendor adheres to and expects the remote telepresence system(s)
      also to adhere to.

      Remote: Sender and/or receiver on the other side of the
      communication channel (depending on context); not Local.  A remote
      can be an Endpoint or an MCU.

      Render: the process of generating a representation from a media,
      such as displayed motion video or sound emitted from loudspeakers.

      Telepresence: an environment that gives non co-located users or
      user groups a feeling of (co-located) presence - the feeling that
      a Local user is in the same room with other Local users and the
      Remote parties.  The inclusion of Remote parties is achieved
      through multimedia communication including at least audio and
      video signals of high fidelity.


4.  Problem Statement

   In order to create a "being there" experience characteristic of
   telepresence, media inputs need to be transported, received, and
   coordinated between participating systems.  Different telepresence



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   systems take diverse approaches in crafting a solution, or, they
   implement similar solutions quite differently.

   They use disparate techniques, and they describe, control and
   negotiate media in dissimilar fashions.  Such diversity creates an
   interoperability problem.  The same issues are solved in different
   ways by different systems, so that they are not directly
   interoperable.  This makes interworking difficult at best and
   sometimes impossible.

   Worse, many telepresence systems use proprietary protocol extensions
   to solve telepresence-related problems, even if those extensions are
   based on common standards such as SIP.

   Some degree of interworking between systems from different vendors is
   possible through transcoding and translation.  This requires
   additional devices, which are expensive, often not entirely
   automatic, and they sometimes introduce unwelcome side effects, such
   as additional delay or degraded performance.  Specialized knowledge
   is currently required to operate a telepresence conference with
   endpoints from different vendors, for example to configure
   transcoding and translating devices.  Often such conferences do not
   start as planned, or are interrupted by difficulties that arise.

   The general problem that needs to be solved can be described as
   follows.  Today, each endpoint sends audio and video captures based
   upon an implicitly assumed model for rendering a realistic depiction
   based on this information.  If all endpoints are manufactured by the
   same vendor, they work with the same model and render the information
   according to the model implicitly assumed by the vendor.  However, if
   the devices are from different vendors, the models they each use for
   rendering presence can and usually do differ.  The result can be that
   the telepresence systems actually connect, but the user experience
   suffers, for example because one system assumes that the first video
   stream is captured from the right camera, whereas the other assumes
   the first video stream is captured from the left camera.

   If Alice and Bob are at different sites, Alice needs to tell Bob
   about the camera and sound equipment arrangement at her site so that
   Bob's receiver can create an accurate rendering of her site.  Alice
   and Bob need to agree on what the salient characteristics are as well
   as how to represent and communicate them.  Characteristics may
   include number, placement, capture/render angle, resolution of
   cameras and screens, spatial location and audio mixing parameters of
   microphones.

   The telepresence multi-stream work seeks to describe the sender
   situation in a way that allows the receiver to render it



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   realistically even though it may have a different rendering model
   than the sender.


5.  Requirements

   Although some aspects of these requirements can be met by existing
   technology, such as SDP, they are stated here to have a complete
   record of what the requirements for CLUE are, whether new work is
   needed or they can be met by existing technology.  Figuring this out
   will be part of the solution development, rather than part of the
   requirements.  Note, the term "solution" is used in these
   requirements to mean the protocol specifications, including
   extensions to existing protocols as well as any new protocols,
   developed to support the use cases.  The solution can introduce
   additional functionality that isn't mapped directly to these
   requirements - e.g., the detailed information carried in the
   signaling protocol(s).  In cases where the requirements are directly
   related to a specific use case, a reference to the use case is
   provided.

   REQMT-1:   The solution MUST support a description of the spatial
              arrangement of source video images sent in video streams
              which enables a satisfactory reproduction at the receiver
              of the original scene.  This applies to each site in a
              point to point or a multipoint meeting and refers to the
              spatial ordering within a site, not to the ordering of
              images between sites.

              Use case point to point symmetric, and all other use
              cases.

              REQMT-1a:  The solution MUST support a means of allowing
                         the preservation of the order of images in the
                         captured scene.  For example, if John is to
                         Susan's right in the image capture, John is
                         also to Susan's right in the rendered image.

              REQMT-1b:  The solution MUST support a means of allowing
                         the preservation of order of images in the
                         scene in two dimensions - horizontal and
                         vertical.

              REQMT-1c:  The solution MUST support a means to identify
                         the point of capture of individual video
                         captures in three dimensions.





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              REQMT-1d:  The solution MUST support a means to identify
                         the area of coverage of individual video
                         captures in three dimensions.

   REQMT-2:   The solution MUST support a description of the spatial
              arrangement of captured source audio sent in audio streams
              which enables a satisfactory reproduction at the receiver
              in a spatially correct manner.  This applies to each site
              in a point to point or a multipoint meeting and refers to
              the spatial ordering within a site, not the ordering of
              channels between sites.

              Use case point to point symmetric, and all use cases,
              especially heterogeneous.

              REQMT-2a:  The solution MUST support a means of preserving
                         the spatial order of audio in the captured
                         scene.  For example, if John sounds as if he is
                         at Susan's right in the captured audio, John
                         voice is also placed at Susan's right in the
                         rendered image.

              REQMT-2b:  The solution MUST support a means to identify
                         the number and spatial arrangement of audio
                         channels including monaural, stereophonic
                         (2.0), and 3.0 (left, center, right) audio
                         channels.

              REQMT-2c:  The solution MUST support a means to identify
                         the point of capture of individual audio
                         captures in three dimensions.

              REQMT-2d:  The solution MUST support a means to identify
                         the area of coverage of individual audio
                         captures in three dimensions.

   REQMT-3:   The solution MUST enable individual audio streams to be
              associated with one or more video image captures, and
              individual video image captures to be associated with one
              or more audio captures, for the purpose of rendering
              proper position.

              Use case is point to point symmetric, and all use cases.

   REQMT-4:   The solution MUST enable interoperability between
              endpoints that have a different number of similar devices.
              For example, one endpoint may have 1 screen, 1 speaker, 1
              camera, 1 mic, and another endpoint may have 3 screens, 2



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              speakers, 3 cameras and 2 microphones.  Or, in a multi-
              point conference, one endpoint may have one screen,
              another may have 2 screens and a third may have 3 screens.
              This includes endpoints where the number of devices of a
              given type is zero.

              Use case is asymmetric point to point and multipoint.

   REQMT-5:   The solution MUST support means of enabling
              interoperability between telepresence endpoints where
              cameras are of different picture aspect ratios.

   REQMT-6:   The solution MUST provide scaling information which
              enables rendering of a video image at the actual size of
              the captured scene.

   REQMT-7:   The solution MUST support means of enabling
              interoperability between telepresence endpoints where
              displays are of different resolutions.

   REQMT-8:   The solution MUST support methods for handling different
              bit rates in the same conference.

   REQMT-9:   The solution MUST support means of enabling
              interoperability between endpoints that send and receive
              different numbers of media streams.

              Use case heterogeneous and multipoint.

   REQMT-10:  The solution MUST ensure that endpoints that support
              telepresence extensions can establish a session with a SIP
              endpoint that does not support the telepresence
              extensions.  For example, in the case of a SIP endpoint
              that supports a single audio and a single video stream, an
              endpoint that supports the telepresence extensions would
              setup a session with a single audio and single video
              stream using existing SIP and SDP mechanisms.

   REQMT-11:  The solution MUST support a mechanism for determining
              whether or not an endpoint or MCU is capable of
              telepresence extensions.

   REQMT-12:  The solution MUST support a means to enable more than two
              endpoints to participate in a teleconference.

              Use case multipoint.





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   REQMT-13:  The solution MUST support both transcoding and switching
              approaches to providing multipoint conferences.

   REQMT-14:  The solution MUST support mechanisms to allow media from
              one source endpoint or/and multiple source endpoints to be
              sent to a remote endpoint at a particular point in time.
              Which media is sent at a point in time may be based on
              local policy.

   REQMT-15:  The solution MUST provide mechanisms to support the
              following:

              *  Presentations with different media sources

              *  Presentations for which the media streams are visible
                 to all endpoints

              *  Multiple, simultaneous presentation media streams,
                 including presentation media streams that are spatially
                 related to each other.

                 Use case is presentation.

   REQMT-16:  The specification of any new protocols for the solution
              MUST provide extensibility mechanisms.

   REQMT-17:  The solution MUST support a mechanism for allowing
              information about media captures to change during a
              conference.

   REQMT-18:  The solution MUST provide a mechanism for the secure
              exchange of information about the media captures.


6.  Acknowledgements

   This draft has benefitted from all the comments on the mailing list
   and a number of discussions.  So many people contributed that it is
   not possible to list them all.  However, the comments provided by
   Roberta Presta, Christian Groves and Paul Coverdale during WGLC were
   particularly helpful in completing the WG document.


7.  IANA Considerations

   There are no IANA considerations associated with this specification.





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8.  Security Considerations

   Requirement REQMT-18 identifies the need to securely transport the
   information about media captures.  It is important to note that
   session setup for a telepresence session will use SIP for basic
   session setup and either SIP or CCMP for a multi-party telepresence
   session.  Information carried in the SIP signaling can be secured by
   the SIP security mechanisms as defined in [RFC3261].  In the case of
   conference control using CCMP, the security model and mechanisms as
   defined in the XCON Framework [RFC5239] and CCMP [RFC6503] documents
   would meet the requirement.  Any additional signaling mechanism used
   to transport the information about media captures would need to
   define the mechanisms by the which the information is secure.  The
   details for the mechanisms needs to be defined and described in the
   CLUE framework document and related solution document(s).


9.  Informative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [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.

   [RFC4353]  Rosenberg, J., "A Framework for Conferencing with the
              Session Initiation Protocol (SIP)", RFC 4353,
              February 2006.

   [RFC4579]  Johnston, A. and O. Levin, "Session Initiation Protocol
              (SIP) Call Control - Conferencing for User Agents",
              BCP 119, RFC 4579, August 2006.

   [RFC5117]  Westerlund, M. and S. Wenger, "RTP Topologies", RFC 5117,
              January 2008.

   [RFC5239]  Barnes, M., Boulton, C., and O. Levin, "A Framework for
              Centralized Conferencing", RFC 5239, June 2008.

   [RFC6503]  Barnes, M., Boulton, C., Romano, S., and H. Schulzrinne,
              "Centralized Conferencing Manipulation Protocol",
              RFC 6503, March 2012.







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Appendix A.  Changes From Earlier Versions

   Note to the RFC-Editor: please remove this section prior to
   publication as an RFC.

A.1.  Changes from draft -06

   Addressing IETF LC comments/editorial nits resulting in the following
   changes:

   o  Included expansion of CLUE in the abstract.

   o  Deleted definitions for "Left" and "Right".

   o  Section 5 - clarified that solution = protocol specifications to
      support requirements.

   o  REQMT-1d, REQMT-2d: Changed term "extent" to "area of coverage"

   o  REQMT-10 - clarified requirement with regards to interworking with
      non-CLUE endpoints

   o  REQMT-15 - reworded to be more specific and normative

   o  REQMT-16 - expanded on what is meant by "extensibility"

A.2.  Changes from draft -05

   Addressing WGLC comments resulting in the following changes:

   o  REQMT-12: Changed term "site" to "endpoint"

   o  Intro: clarified that SIP based conferencing also is relevant to
      CLUE.

   o  Intro: clarified that while CLUE doesn't dictate implementation
      choices, it does describe a framework for the protocol solution.

   o  Clarified that mapping to use cases isn't comprehensive (i.e.,
      only done when there is a direct correlation).

   o  Added text that the requirements do not reflect all those required
      for the solution - i.e., the solution can provide more
      functionality as needed.

   o  Editorial nits and clarifications - changed lc "must" to UC
      (REQMT-17).




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A.3.  Changes from draft -04

   o  Removed REQMT-2c, related to issue #37 in the tracker.

   o  Deleted REQMT-3b.  Condensed REQMT-3 to subsume REQMT-3a.  This is
      related to Issue #38 in the tracker.

   o  Updated REQMT-14 based on (mailing list) resolution of Issue #39.

   o  Deleted OPEN issue section as those were transferred to the ID
      tracker and have been resolved either by changes to this document
      or to earlier versions of the document

A.4.  Changes from draft -03

   o  Added a tad more text to the security section Paragraph 18.

A.5.  Changes from draft -02

   o  Updated IANA section - i.e., no IANA registrations required.

   o  Added security requirement Paragraph 18.

   o  Added some initial text to the security section.

A.6.  Changes from draft -01

   o  Cleaned up the Problem Statement section, re-worded.

   o  Added Requirement Paragraph 17 in response to WG Issue #4 to make
      a requirement for dynamically changing information.  Approved by
      WG

   o  Added requirements #1.c and #1.d.  Approved by WG

   o  Added requirements #2.d and #2.e.  Approved by WG

A.7.  Changes From Draft -00

   o  Requirement #2, The solution MUST support a means to identify
      monaural, stereophonic (2.0), and 3.0 (left, center, right) audio
      channels.

       changed to


      The solution MUST support a means to identify the number and
      spatial arrangement of audio channels including monaural,



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      stereophonic (2.0), and 3.0 (left, center, right) audio channels.

   o  Added back references to the Use case document.

      *  Requirement #1 Use case point to point symmetric, and all other
         use cases.

      *  Requirement #2 Use case point to point symmetric, and all use
         cases, especially heterogeneous.

      *  Requirement #3 Use case point to point symmetric, and all use
         cases.

      *  Requirement #4 Use case is asymmetric point to point, and
         multipoint.

      *  Requirement #9 Use case heterogeneous and multipoint.

      *  Requirement #12 Use case multipoint.


Authors' Addresses

   Allyn Romanow
   Cisco Systems
   San Jose, CA  95134
   USA

   Email: allyn@cisco.com


   Stephen Botzko
   Polycom
   Andover, MA  01810
   US

   Email: stephen.botzko@polycom.com


   Mary Barnes
   Polycom

   Email: mary.ietf.barnes@gmail.com








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