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The Italian CONTENT Local Industry Workshop
Napoli, 29th May 2009
A Standard Framework for Content Adaptation: MediaCtrl
Lorenzo Miniero (CINI-UoN)
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Overview
• Issues– Heterogeneous Networks– Heterogeneous Devices– Encoding/Decoding/Bandwidth
• Protocol Requirements– Signaling of Media Session– Media Delivery– Control and Interactivity
• Standardization efforts– Third Generation Parthership Project (3GPP)– Internet Engineering Task Force (IETF)
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Issues
• Heterogeneous networks and devices– Bandwidth fluctuates– Not the same bandwidth anywhere– Even if it is, devices may have different capabilities
• Dynamic behaviour– Different codecs/resolutions/etc.– Content adaptation– QoS feedback mechanisms
• New Trends– Distributed content– Need for interactivity
• Choosing content• Controlling media• ...
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Signaling
• Session Initiation Protocol (SIP)– IETF RFC 3261 (http://www.ietf.org/rfc/rfc3261.txt)– Negotiates media sessions
• Originally conceived for VoIP only• Subsequently extended to implement any kind of multimedia application
– Has ways to dinamically update sessions
• Session Description Protocol (SDP)– IETF RFC 3264 (http://www.ietf.org/rfc/rfc3264.txt)– Conveyed in SIP payloads– Provides details about media sessions to negotiate
• Transport addresses• Encoding/direction of media streams
• SIP/SDP base protocol for IMS– IP Multimedia Subsystem (3GPP)– Unified access to services from heterogeneous networks
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Media Delivery
• Real-Time Transport Protocol (RTP)– IETF RFC 3550 (http://www.ietf.org/rfc/rfc3550.txt)– Transports media frames in real-time– Opaque to the encoding– Negotiated in SIP/SDP messages
• Real-Time Transport Control Protocol (RTCP)– “Sister” protocol of RTP– Provides feedback on delivery of streams
• Base for QoS mechanisms
• RTP Payload for DTMF Digits– IETF RFC 2833 (http://www.ietf.org/rfc/rfc2833.txt)– Further means for interactivity
• DTMF digits can be associated with actions
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Convergent Applications
• SIP/SDP and RTP/RTCP provide means for end-to-end communication– Need for an additional control layer with business logic– Several protocols can be involved
• SIP, RTP, HTTP, ???
• Separation of responsibilities– Application Server (Business Logic)– Media Server (Content Manipulation and Delivery)– AS and MS need a way to interact
• Media Server Control (IETF MediaCtrl)– Standard Framework for Content Adaptation– Describes architecture and protocols for [UAs-]AS-MS interaction– CINI/UoN deeply involved in standardization process
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Media Server Control (MediaCtrl)
• Functionality– Media Processing– Mixing/Transcoding– Playing/Recording– Storing/Retrieving– Detecting Tones (DTMF)– Interactive Voice Response (IVR)/VoiceXML– Text-to-Speech/Speech Recognition– RTP Streams Manipulation– Monitoring and Auditing– Event Notification (subscription mechanism)
• MRFC/MRFP (interface/container) in IMS– May wrap different specification (e.g. H.248)
Client B
SIP SIP
ApplicationServer
MediaServer
SIP Control
Channel RTPRTP
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Why MediaCtrl?
• Several extant protocols...– ITU H.248.19 (MeGaCo)– RFC 4240– MSCML (Media Server Control Markup Language)– VoiceXML/CCXML– ...
• ... a SIP-aware standard was needed– Completely SIP-based– Specific requirements (e.g. MRF...)– Simpler to work with
• JSR 309 and SIP Servlets
• Media Server Control (MEDIACTRL)– BOF (Birds of a Feather) in November 2006– Work almost completed
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Overview
• Charter– http://www.ietf.org/html.charters/mediactrl-charter.html
• Advanced services– Content Delivery– Interactive Voice Response (IVR)– Mixing/Bridging (Conferencing)
• Several topologies: 1:1 → m:n– Media Resource Broker
• Modular approach– Opaque payloads– Control packages– Transactions
as “bricks”
Header Payload
Header Payload
Control Package 2
Control Package 1
Control Package 3
Protocol Messages
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Architecture (1)
ApplicationApplicationServerServer
MediaMediaServerServer
UserUserAgentAgent
UserSignaling(e.g. SIP) SIP
(MediaDialog)
RTP/SRTP
TCP/TLS(ControlChannel)
SIP(ControlDialog)
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Architecture (2)
• AS uses SIP to establish TCP/TLS connection to MS– SIP dialog called Control Dialog– TCP/TLS connection called Control Channel
• Channel setup: SIP with COMEDIA negotiation• Authentication: SYNC message
• Application Server– Frontend for UA signalling
• SIP 3rd Party Call Control (Media Dialog towards MS)
– Handles business logic and control layer (e.g. HTTP)
• Media Server– Termination of Media Channels– Enforces directives coming from AS and notifies about events– AS and RTCP as QoS mechanisms
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Interactive Content Delivery
• Passive streaming– Playout of pre-recorded multimedia files– Playout of live multimedia streams (e.g. RTSP)– Optional VCR controls (rw, ffw, play, pause, volume, etc.)
• Interactivity
• Active Streaming – Use of hidden conferences to broadcast source– Storing of multimedia contents for future use
• Voice mail• Video messages• Tutorials
• Optimized Delivery– MS can fetch content to delivery from any source– MS in use can be changed dynamically
• Media Resource Brokering (MRB)
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Media Resource Brokering (MRB)
• Generic topology is m:n– Several Application Servers (m) and a pool of Media Servers (n)
• Media Resource Broker– Allows AS to audit pool of MS for capabilities/resources– MS themselves provide MRB with information– MRB tells AS which MS is best according to requirements
• Required functionality• Required encodings• Geographic locations• ...
– UAs can be moved dynamically from a MS to another
• Two different interfaces– Publisher Interface (MS→MRB)
– Consumer Interface (MRB→AS)
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CINI-UoN involvement in MediaCtrl
• draft-ietf-mediactrl-architecture-04– Design Team
• draft-ietf-mediactrl-ivr-control-package-06– Design Team
• draft-ietf-mediactrl-ivr-control-package-06– Design Team
• draft-ietf-mediactrl-call-flows-00– A. Amirante, T. Castaldi, L. Miniero, S.P.Romano
• draft-ietf-mediactrl-mrb-00– C. Boulton, L. Miniero
• Open source prototype implementation– http://mediactrl.sf.net ‒ http://www.comics.unina.it