peter parnes, cdt1/22 media scaling of ip-multicast streams in heterogeneous networks peter parnes...
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Peter Parnes, CDT 1/22
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
Peter Parnes, CDT 2/22
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
Peter Parnes, CDT 3/22
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!
Peter Parnes, CDT 4/22
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.
Peter Parnes, CDT 5/22
Which bandwidth should be used when transmitting a real-time media stream over heterogeneous networks?
Which bandwidth should be used when transmitting a real-time media stream over heterogeneous networks?
Internet
Sender
100Mbps
LocalReceiver
100Mbps
InternetReceiver
500Kbps
ISDNReceiver
128Kbps
Peter Parnes, CDT 6/22
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
Peter Parnes, CDT 7/22
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
Peter Parnes, CDT 8/22
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)
Peter Parnes, CDT 9/22
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).
Peter Parnes, CDT 10/22
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
Peter Parnes, CDT 11/22
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
Peter Parnes, CDT 12/22
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
Peter Parnes, CDT 13/22
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
Peter Parnes, CDT 14/22
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
Peter Parnes, CDT 15/22
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
Peter Parnes, CDT 16/22
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 :-)
Peter Parnes, CDT 17/22
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
Peter Parnes, CDT 18/22
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.
Peter Parnes, CDT 19/22
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).
Peter Parnes, CDT 20/22
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
Peter Parnes, CDT 21/22
Questions?
http://www.cdt.luth.se/~peppar/
http://www.cdt.luth.se/mStar/
http://www.marratech.com/
http://www.cdt.luth.se/~peppar/
http://www.cdt.luth.se/mStar/
http://www.marratech.com/