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MMUSIC

MMUSIC. RTSP Caching Mark Green markg@entera.com. IETF Draft. Caching Support in RTSP/RTP Servers draft-periyannan-rtsp-caching-01.txt Authors: Ron Frederick Jay Geagan Mike Kellner Alagu Periyannan Entera. Dynamic replication of streaming media Bring content closer to users

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MMUSIC

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  1. MMUSIC RTSP Caching Mark Green markg@entera.com

  2. IETF Draft Caching Support in RTSP/RTP Servers draft-periyannan-rtsp-caching-01.txt Authors: Ron Frederick Jay Geagan Mike Kellner Alagu Periyannan Entera

  3. Dynamic replication of streaming media Bring content closer to users On-demand Stored Movies Replicate into cache Playback from cache Streaming Media Caching

  4. Streaming Caching Issues • Issues to be resolved • Transfer Loss • Transformation Loss • Cache Coherency • Access Accounting • Authorization • Copy Protection • Varied levels of solutions • Cache / Origin Server under common administrative control • Owned by separate entities

  5. Transfer/Transformation Loss • Transfer Loss • UDP packet loss • Harder to create a perfect copy • HTTP does not have this problem • Transformation Loss • Important information in original media file is lost • Some information harder to parse from packets than from file • HTTP servers usually do not transform data

  6. Cache Coherency and Access Logging • Cache Coherency • Users must get the latest copy of media • Overhead for coherency not as high as in HTTP caching • Access Logging • Content owners want accurate hit counts • HTTP does not attempt to solve this problem

  7. Authentication and Copy Protection • Authentication • Caches should not serve restricted streams without authenticatiing with the origin server • An airtight solution can be very complex • Copy Protection • Streaming content is perceived to have more value than web content • Open specifications can lead to the development of rogue caches • An airtight solution can be very complex

  8. Packet Recording Approach • Record RTP/UDP packets by acting as a client to the origin server • Replay packets when real clients request the stream • Benefits: • No changes to origin servers • Problems: • Packet loss during recording • Not enough information in packets as in original file

  9. File Transfer Approach • Use the RTSP/TCP connection to transfer original file • Serve the file from cache as if it were an origin server • Benefits: • Perfect copy created at caches • Problems: • Caches need to know about many different file formats • Hard to solve copy protection issues

  10. Streaming Caching Proposal • Hybrid approach: • File Transfer + Packet Recording = Packet Transfer • Use RTSP/TCP connection to transfer RTP packets • Use a special “metachannel” within the RTSP connection to transfer additional information • Transmission timestamp, I, B, P frame, etc.

  11. Packet Transfer Approach • Benefits: • Provides a loss-less copy of content at the cache • Avoids transformation loss • File format independent • RTP payload format independent • Problems: • Requires special support at origin servers • Copy protection, authentication and access logging

  12. Open Issues • Copy protection • Rogue caches can create illegal copies • Packet transfer is not much worse than packet recording (which one can do today with currently deployed servers) • Enforcement of authentication and access logging • Rogue caches can choose not to participate in the logging and authentication scheme

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