Climber extension with Multiple Description Coding (MDC)

Kunwoo ParkSeoul National University, Korea

Live Streaming Services

• MSN broadcast– http://liveearth.msn.com

2/12

Outline

• Live Streaming Services• Climber• MDC• Climber + MDC

3/12

Live Streaming Services• Cost

– Building a CDN costs too much– Encourage peers to contribute to the system

• Resilience– Live Earth concert in July 2007 rated 237,000

simultaneous viewers at the peak– A system should work in the presence of high

churn• Delay

– Live streaming is not like that of file downloading service

– Packets should be delivered in time

4/12

Climber

• An Incentive-based Resilient P2P System for Live Streaming Services

• A hybrid of a tree and a mesh– Tree - main structure, forward streaming– Mesh - enhance resilience by redundant

edges• Random Edge

• Design concepts– Incentive– Resilience

5/12

Random Edge?

• A directed edge to a random peer– Only the sequence

number of the stream is sent along a random edge

• For each available outdegree, a node makes a random edge with low probability

6/12

0

1

3

2

4

5Randomedge

7/12

A node climbs a tree by a Random Edge

3

congested/failed node

random edge

Node 7 climbs the tree by being a child of node 2

• Climber greatly simplifies the recovery procedure caused by node failures

• Actually, Climber does not distinguish node failure from node congestion

Multiple Description Coding

• A coding technique – fragments a stream into k sub

streams (k>=2)

• The more sub streams received, the higher the quality– roughly proportional to # of sub

streams– any subset of these sub streams

can be decoded8/12

Climber + MDC

• In Climber, only header information are sent via random edges

• Climber’s multipath delivery concept naturally fits with MDC

• What if we send a sub stream as a random edge– Improved resilience with much more

bandwidth consumption

9/12

Need a prediction mechanism

10/12

123

12

I am receiving 1, 2, 3. If I send only 1, 2, will my descendants receive 3 through random edges?

134

4 3

sub stream 1, 2, 3, 4

1,2,3,4

11/12

Summary

• Climber– The 7th International Workshop on

Peer-to-Peer Systems (IPTPS '08)

• MDC• Climber + MDC

• Ongoing work

Thank you• Any questions?

12/12