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CLUE PowerPoint Presentation

CLUE

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CLUE

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  1. CLUE Signaling Requirements for implementing the Framework CLUE interim Feb 15, 16, 2012 Allyn Romanow (allyn@cisco.com) Stephen Botzko (stephen.botzko@gmail.com) Robert Hansen (rohanse2@cisco.com)

  2. Data Flow Provider Consumer Consumer capabilities Advertisement-- Captures and Potential Streams Selection Media …

  3. Parameters • Capture attributes – spatial relations, purpose, switched/composed, layout/policies, audio channel, encoding group id • Encoding attributes – max width, max height, max FPS, max macroblocks per second, max bitrate

  4. Dynamic messages • Advertisement and selection happen throughout call

  5. Using SDP for signaling CLUE- for discussion • SDP for what? • Session-level and media-level media parameters • CLUE encodings, encoding groups • CLUE capture attributes • CLUE selection • Latency requirements? • if too stringent SDP would not work •   What do intermediaries need to know about CLUE info?  • SDP would be an advantageous way to carry that subset of the information.

  6. SDP questions • Is there a concern about SDP bloat and the need to preserve backward capability – large number of advertisements and selections • CLUE doesn’t fit within offer/answer.. So if we’re using SDP, it will be interesting

  7. Goal We need to agree on the requirements for signaling protocols to implement the framework

  8. Requirements for each • Consumer advertisements - skip for now • Capture advertisements • Encoding advertisements • Selection • Media

  9. Timing Requirements -advertisements of capture attributes • Switched/composed – changes are frequent • Spatial attributes change as current participant changes, speaker changes • Need spatial info before media is received in order to render (Need to sync with media) • Advertisement needs to be fast. On par with the speed of the media. Order of 100s ms to 300ms • A slow signaling channel wouldn’t work • Want delivery status to be known by provider, to manage latency - reliability

  10. Requirements for capture attribs advertisement continued • Advertisements also change when new sites join - less frequently than speaker changes. • Advertisements might change in response to network conditions • In these cases advertisement can be slower. Latencies on the order of 1-2 seconds seem acceptable

  11. Timing Requirements –Advertisements of encodings & encoding groups • Media parameters (bandwidth, resolution, etc) are maximums • No need to change with voice switching • Hence more static than spatial • Scale of 1-2 seconds • Encodings and the enc group might change due to network conditions, local resources usage. Infrequent and longer time scale.

  12. Timing Requirements for consumer selection • Consumer selection often automatic • done by machine agents per policy • Latency requirements might need more analysis • User selection will be included in most UIs • Needs to be responsive to human speed • Latency of 1-2 seconds seems sufficient

  13. Signalling bandwidth • Requires investigation

  14. Requirements for media • Multiplex RTP streams on single session • Hard limit on the number of streams • How to do mapping of source to output is the issue • Different approaches: • draft-lennox-clue-rtp-usage-02 - RTP extension • draft-westerlund-clue-multistream-conference-00 - SSRC

  15. Requirements for intermediaries • Intermediaries need to know (and change) some parameters so they can enforce administrator policies • Bandwidths (overall, per stream) • Security • Other media encoding parameters • In SIP calls this is traditionally solved by intermediaries monitoring/rewriting SDPs

  16. Use of SDP • SDP is the primary location for media parameters – seems a good fit for encoding group parameters • Allows policy monitoring by intermediary devices • Can be used to negotiate a CLUE protocol for fast end-to-end messages

  17. SDP Challenges • Latency bounds and media synchronization requirements for some messaging not met by SIP/SDP • Encoding Group advertisement challenging to fit into SDP • Don’t know how to use offer without answer for the encoding advertisement • Two one-way communications – not the O/A model • Potential interop issues if SDP size is significantly expanded