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Peter Parnes, CDT1/22 Media Scaling of IP-Multicast Streams in Heterogeneous Networks Peter Parnes LTU-CDT/Marratech Roxy Workshop 980921-23 Media Scaling of IP-Multicast Streams in Heterogeneous Networks Peter Parnes LTU-CDT/Marratech Roxy Workshop 980921-23
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Peter Parnes, CDT2/22 Overview Background Current Problem Proposed Solutions mStar Current Status in the Internet Summary Background Current Problem Proposed Solutions mStar Current Status in the Internet Summary
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Peter Parnes, CDT3/22 Background “Broadcasts” of real-time media on the Internet is becoming more and more important. It is very central to the Roxy project. If the used system shall scale, IP- multicast HAS to be used! “Broadcasts” of real-time media on the Internet is becoming more and more important. It is very central to the Roxy project. If the used system shall scale, IP- multicast HAS to be used!
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Peter Parnes, CDT4/22 Requirements and Restrictions Best-effort delivery Reliability not required Applications have to be adaptive, i.e. have to adapt to network congestion and be able to handle different configurations. Best-effort delivery Reliability not required Applications have to be adaptive, i.e. have to adapt to network congestion and be able to handle different configurations.
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Peter Parnes, CDT5/22 Which bandwidth should be used when transmitting a real-time media stream over heterogeneous networks? Internet Sender 100Mbps Local Receiver 100Mbps Internet Receiver 500Kbps ISDN Receiver 128Kbps
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Peter Parnes, CDT6/22 Proposed solutions Max/Min client bandwidth Simulcast Network transcoders Receiver driven Layered Multicast - RLM Bandwidth Guessing - TCP friendly Active Networks Active Services Max/Min client bandwidth Simulcast Network transcoders Receiver driven Layered Multicast - RLM Bandwidth Guessing - TCP friendly Active Networks Active Services
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Peter Parnes, CDT7/22 Max/Min client bandwidth Just ignore some set of receivers Send the stream with high bandwidth Ignore low bandwidth receivers Send the stream with low bandwidth Force high bandwidth receivers to use low quality Does not take congestion into account Just ignore some set of receivers Send the stream with high bandwidth Ignore low bandwidth receivers Send the stream with low bandwidth Force high bandwidth receivers to use low quality Does not take congestion into account
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Peter Parnes, CDT8/22 Simulcast Send the same stream with different encodings from the sender and let the receivers choose what they want to receive. Can be very expensive CPU wise Wastes bandwidth on shared links Does not take congestion into account in the way it is being used today. Used in mStar (more later) Send the same stream with different encodings from the sender and let the receivers choose what they want to receive. Can be very expensive CPU wise Wastes bandwidth on shared links Does not take congestion into account in the way it is being used today. Used in mStar (more later)
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Peter Parnes, CDT9/22 Network Transcoders A common approach is to deploy transcoders on the boundaries between different networks. Transcoding, mixing, downscaling E.g. transcode MJPEG to H.261 when the traffic leaves a campus (high bandwidth network). E.g. mStar mTunnel can transcode when tunnelling mcast data (more later). A common approach is to deploy transcoders on the boundaries between different networks. Transcoding, mixing, downscaling E.g. transcode MJPEG to H.261 when the traffic leaves a campus (high bandwidth network). E.g. mStar mTunnel can transcode when tunnelling mcast data (more later).
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Peter Parnes, CDT10/22 Receiver driven Layered Multicast - RLM Divide the stream into a hierarchy of exclusive additive layers Each layer is multicasted to a different group loop: if no_congestion then join next group to get higher layer else leave group to drop highest layer Divide the stream into a hierarchy of exclusive additive layers Each layer is multicasted to a different group loop: if no_congestion then join next group to get higher layer else leave group to drop highest layer
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Peter Parnes, CDT11/22 RLM Problems How to detect congestion caused by my tests or by others Shared learning proposed Does it scale? Today long timeout in mcast forwarding trees Might lead to false interpretation of the current situation Is not “nice” to TCP How to detect congestion caused by my tests or by others Shared learning proposed Does it scale? Today long timeout in mcast forwarding trees Might lead to false interpretation of the current situation Is not “nice” to TCP
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Peter Parnes, CDT12/22 Bandwidth Guessing In early 97 a proposal called “TCP- Friendly” was distributed. Describes a way of estimating the bandwidth between a sender and a receiver based on RTT and current packet drop. Takes TCP into account and will be a “nice” participant in the network In early 97 a proposal called “TCP- Friendly” was distributed. Describes a way of estimating the bandwidth between a sender and a receiver based on RTT and current packet drop. Takes TCP into account and will be a “nice” participant in the network
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Peter Parnes, CDT13/22 BW Guessing Problems Hard to calculate RTT accurately Works only for “broadcast” situations Not very tested yet Hard to calculate RTT accurately Works only for “broadcast” situations Not very tested yet
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Peter Parnes, CDT14/22 Active Networks The latest “buzzword” network research topic (since ATM is practically dead) Basic idea: Allow injection of small programs into network nodes Network nodes perform computations on user data The latest “buzzword” network research topic (since ATM is practically dead) Basic idea: Allow injection of small programs into network nodes Network nodes perform computations on user data
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Peter Parnes, CDT15/22 Active Networks... Two Different Approaches Code and control is handled out-of-band Each packet carries miniature programs (capsules) Allows networks to be modified “on- demand” Opens a completely new area for real- time media scaling Two Different Approaches Code and control is handled out-of-band Each packet carries miniature programs (capsules) Allows networks to be modified “on- demand” Opens a completely new area for real- time media scaling
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Peter Parnes, CDT16/22 Active Networks... Issues: Safety, fairness, appropriate architecture, common programming model, robustness Status: At the very beginning A very “political” problem “I dare You to run code in my router!” Steve Deering - Cisco (currently :-) Issues: Safety, fairness, appropriate architecture, common programming model, robustness Status: At the very beginning A very “political” problem “I dare You to run code in my router!” Steve Deering - Cisco (currently :-)
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Peter Parnes, CDT17/22 Active Services Deploy user controllable programs-pads in the network. Users can deploy their own transcoding programs and can easily up-grade these when needed A system for this is currently being deployed and tested on Berkeley Campus Deploy user controllable programs-pads in the network. Users can deploy their own transcoding programs and can easily up-grade these when needed A system for this is currently being deployed and tested on Berkeley Campus
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Peter Parnes, CDT18/22 mStar mTunnel contains support for media- aware rescaling, transcoding, mixing and switching of audio and video. Could be easily be extended for general transcoding between different mcast groups. Simulcast is currently being used in mStar Pro for the electronic corridor. BW Guessing and RLM based approaches should be further investigated. mTunnel contains support for media- aware rescaling, transcoding, mixing and switching of audio and video. Could be easily be extended for general transcoding between different mcast groups. Simulcast is currently being used in mStar Pro for the electronic corridor. BW Guessing and RLM based approaches should be further investigated.
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Peter Parnes, CDT19/22 Status in Internet Almost all traffic is still sent using Unicast - transcoding at the server Network transcoders probably most common Simulcast less common than one could imagine (lack of good support in today’s applications). Almost all traffic is still sent using Unicast - transcoding at the server Network transcoders probably most common Simulcast less common than one could imagine (lack of good support in today’s applications).
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Peter Parnes, CDT20/22 Summary A number of more or less proposed solutions: Max/Min client bandwidth Simulcast Network transcoders Receiver driven Layered Multicast - RLM Bandwidth Guessing - TCP friendly Active Networks Active Services Still a lot of research needed A number of more or less proposed solutions: Max/Min client bandwidth Simulcast Network transcoders Receiver driven Layered Multicast - RLM Bandwidth Guessing - TCP friendly Active Networks Active Services Still a lot of research needed
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Peter Parnes, CDT21/22 Questions? peppar@cdt.luth.se http://www.cdt.luth.se/~peppar/ http://www.cdt.luth.se/mStar/ http://www.marratech.com/ peppar@cdt.luth.se http://www.cdt.luth.se/~peppar/ http://www.cdt.luth.se/mStar/ http://www.marratech.com/
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Peter Parnes, CDT22/22 Multicast vs. Unicast
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