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draft-allen-sipping-poc-p-answer-state-header

draft-allen-sipping-poc-p-answer-state-header

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draft-allen-sipping-poc-p-answer-state-header

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  1. draft-allen-sipping-poc-p-answer-state-header Andrew Allen: Research In Motion aallen@rim.com Tom Hallin: Motorola Jan Holm: Ericsson

  2. P-Answer-State draft overview • The draft is split out from draft-allen-sipping-poc-pheaders-01, renamed and reset to -00 version • Allows a PTT Server to indicate in a response whether the session is established end-to-end or only as far as an intermediate node (PTT Server) • Needed to enable media buffering prior to called party answer (early right to speak indication) • Needed to provide and indication to the caller that early right to speak buffering is taking place

  3. P-Answer-State Header • Values • Confirmed • Unconfirmed • May be included in Responses • 1xx (typical 183 Session Progress) • 200 OK • May be included in a sipfrag or included directly in a NOTIFY • NOTIFY sent as a result of the subscription established by REFER • Security Assumptions • Trusted PTT Server exists that has knowledge of currently selected Answer Mode of the terminating UA (PTT Client) • Trusted PTT Server that originating UA (PTT Client) trusts to accept and buffer media

  4. Changes(from draft-allen-sipping-poc-pheaders-01) • P-Alerting-Mode header definition has been removed • This extension is progressed separately as standards track (draft-willis-sip-answeralert) • Security considerations improved. • PUBLISH method has been added to usage table. • The procedures at the UA text has been split into UA-terminal and UA- intermediate-node for better clarity. • A session flow example section added. • Various nits and editorial corrections.

  5. PTT Server X PTT Server B UA B PTT Server A UA A Distributed Scenario (PES) Refer 200 OK INVITE INVITE Answer mode Authorization 183 Session Progress (P-Answer-State: Unconfirmed) INVITE NOTIFY (SIPFRAG 200 OK P-Answer-State: Unconfirmed) 200 OK (P-Answer-State: Unconfirmed) UA Auto Answers 200 OK Media Media Buffering 200 OK 200 OK (P-Answer-State: Confirmed) Media

  6. PTT Server AXB UA B UA A Consolidated Scenario (PES) Refer 200 OK Answer mode Authorization INVITE NOTIFY (P-Answer-State: Unconfirmed) UA Auto Answers 200 OK Media Media Buffering 200 OK Media

  7. Open Issues • Generalize to “contains an answer” instead of “contains a SDP answer” • Accepted • Delivering P-Answer-State header to originating UA in Consolidated Pre-established Session (PES) scenario • Problem when there is no response containing P-Answer-State header to include in the sipfrag • Include as a header of the initial NOTIFY? • Include as a header in a “dummy” 100 TRYING sipfrag in the initial NOTIFY? • Include in the 2xx response to the REFER? • Something else? • What to call the “Intermediate Node” (B2BUA or Proxy) • PTT Server? • PoC-Intermediate? • How much to say or define about the general “Intermediate Node” behavior in the draft

  8. Questions

  9. Backup Slides

  10. PoC Session Concepts • On-Demand Session • Conventional end-to-end INVITE initiated PoC session establishment at Push-to-Talk time • Pre-established Session • Pre-established codec negotiation between PoC Client and Participating PoC Function using INVITE prior to Push-to-Talk time • Semi-permanent Pre-established INVITE dialogue with Participating PoC Function maintained • Refer within the INVITE dialogue used to initiate POC session establishment at Push-to-Talk time

  11. PoC Concepts and Challenges • PoC (Push to Talk over Cellular) Concepts • Sessions established using Push To Talk button • Right to Speak Indication (e.g Audible tone) • Half Duplex media • Talk Burst Control • 1-1 and Group Calls • Manual and Auto-Answering terminal • Manual Answer Override (MAO) for dispatch • PoC Session establishment latency challenge • Highly bandwidth constrained cellular networks • Push-to-talk to Right-to-speak indication latency requirement in order of a second

  12. OMA PoC Architecture

  13. PoC Server Functions • Participating PoC Function • Provides policy enforcement for incoming PoC Session (e.g. Access Control, Incoming PoC Session Barring, availability status, etc) • Stores the current Answer Mode, Incoming PoC Session Barring and Incoming Instant Personal Barring preferences of the PoC Client. • Controlling PoC Function • Acts as the Focus for the PoC Session • May act as an exploder • Provides the centralized media distribution • Provides the centralized Talk Burst Control functionality

  14. PTT Server X PTT Server B UA B PTT Server A UA A On-Demand Scenario INVITE INVITE INVITE Answer mode Authorization 183 Session Progress (P-Answer-State: Unconfirmed) INVITE 200 OK (P-Answer-State: Unconfirmed) 200 OK (P-Answer-State: Unconfirmed) PoC Client Auto Answers Media Media Buffering 200 OK 200 OK (P-Answer-State: Confirmed) Media