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SDPng Requirements

SDPng Requirements. Dirk Kutscher dku@tzi.uni-bremen.de Jörg Ott jo@tzi.uni-bremen.de Carsten Bormann cabo@tzi.uni-bremen.de. draft-kutscher-mmusic-sdpng-req-00.txt. http://www.dmn.tzi.org/ietf/mmusic/sdp-ng/. Overview. Motivation (Terminology) General requirements

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SDPng Requirements

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  1. SDPng Requirements Dirk Kutscher dku@tzi.uni-bremen.de Jörg Ott jo@tzi.uni-bremen.de Carsten Bormann cabo@tzi.uni-bremen.de draft-kutscher-mmusic-sdpng-req-00.txt http://www.dmn.tzi.org/ietf/mmusic/sdp-ng/ 48. IETF, Pittsburgh Kutscher/Ott/Bormann

  2. Overview • Motivation • (Terminology) • General requirements • Session description requirements • Capability negotiation requirements • Next steps 48. IETF, Pittsburgh Kutscher/Ott/Bormann

  3. Motivation for SDPng • No negotiation mechanism in SDP (RFC2327) • Has not been designed for capability negotiation • SDP’s extension mechanism • Session and media attributes: a= • Provides free extension mechanism • Unknown attributes to be ignored • Which attributes are required for understanding a session description? • Smooth evolution is difficult when many extensions are developed • Limited expressiveness • Syntax, grouping, … 48. IETF, Pittsburgh Kutscher/Ott/Bormann

  4. General Requirements • Simplicity • easy to parse and implement • Extensibility • extensions mechanisms that allows to accommodate future applications without having to modify base spec. • "Firewall friendliness" • session descriptions should be efficiently parsable by network elements 48. IETF, Pittsburgh Kutscher/Ott/Bormann

  5. General Requirements • Security • Support for privacy and authentication services of transport and signaling protocols • Text encoding • concise text encoding for portability and simple implementations • SDP-mapping • translate SDPng to SDP • maybe not always possible 48. IETF, Pittsburgh Kutscher/Ott/Bormann

  6. Session Description Requirements • Media types • Must fit into RFC 1889/1890 model of standard and dynamic payload types • Re-use payload formats, format names, RTP-profiles, MIME-mapping • Media Stream Packetization • Support different variants: • Redundancy encoding scheme, FEC, stream repair etc. • Codec specification independent from packetization scheme • Extensible to other or non-standard schemes 48. IETF, Pittsburgh Kutscher/Ott/Bormann

  7. Requirements for Describing Transport Parameters • Transport • Support for different transport protocols and network architectures (IP, ATM etc.) • Different address formats, parameters • Different QoS models and parameters • Flexibility • More than 1 transport address per component • Layered encodings • Multi-/unicast address lists • More than 1 address per potential configuration set • Specialized media engines • Constraints like source filters etc. 48. IETF, Pittsburgh Kutscher/Ott/Bormann

  8. Session Description Requirements • Arbitrary other parameters • Extension mechanism required • Identify extensions • Distinguish mandatory and optional extensions • Asymmetric configurations • “Can send format A but want to receive format B” • Conciseness and structured extensibility requires • Grouping of definitions • Naming and referencing groups 48. IETF, Pittsburgh Kutscher/Ott/Bormann

  9. Elements ofCapability Negotiation • Model for specifying alternatives (potential configurations) • Negotiation model • Syntax and semantics • Obtain session description as negotiation result • Augment negotiation result with transport parameters and general session info 48. IETF, Pittsburgh Kutscher/Ott/Bormann

  10. Capability Negotiation Requirements I • Fit into SIP model (3-way handshake) • Semantics independent • Feature-unaware negotiation is key to extensibility and smooth future evolution • Grouping capabilities required for • Conciseness of exchanged negotiation • Referencing, combining capability sets • Structured extension mechanism 48. IETF, Pittsburgh Kutscher/Ott/Bormann

  11. Capability Negotiation Requirements II • Constraints • Simultaneous capabilities (in a simple way!) • “Up to 10 GSM or G.711 streams, but only one codec at a time.” • Processing rules • Point-to-point and multiparty • Different negotiation policies for different session types • “Implementation issues” • Re-use other IETF work, namely RFC 2533 48. IETF, Pittsburgh Kutscher/Ott/Bormann

  12. What next? • More requirements? • MEGACO • Specific link layers and protocols • Develop architecture • Session description • Capability negotiation • Decide on syntax 48. IETF, Pittsburgh Kutscher/Ott/Bormann

  13. http://www.dmn.tzi.org/ietf/mmusic/sdp-ng/ 48. IETF, Pittsburgh Kutscher/Ott/Bormann

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