1. CoopNet: Cooperative Networking
Phil Chou, Venkat Padmanabhan, Helen Wang
September 17, 2002

2. Motivation “Flash crowd” can overwhelm server
often due to news event of widespread interest…
… but not always (e.g., Webcast of birthday party)
can affect relatively obscure sites (e.g., election.dos.state.fl.us, firestone.com, nbaa.org)
affects Web content as well as streaming content (live and on-demand)
infrastructure-based CDNs aren’t for everyone
Goal: solve the flash crowd problem!

3. Cooperative Networking
Client-server
Pure peer-to-peer
CoopNet
CoopNet complements client-server system
Client-server operation in normal times
P2P content distribution invoked on demand to alleviate server overload
Clients participate only while interested in the content
Server still plays a critical role
P2P comm central to the system
Us: no:
Addresses problem cases of client-server communication
Complements traditional client-server communications
Clients cooperate to improve performance only when needed
Clients may only be willing to cooperate for short periods
We study CoopNet in the context of the flash crowd problem
Selective use of p2p

4. Research Activities
Web flash crowd alleviation (with Kay Sripanidkulchai)
evaluation using Sep 11 traces from MSNBC
prototype implementation done
IPTPS ’02
MDC-based streaming media distribution
evaluation using Sep 11 traces from MSNBC, Akamai, Digital Island
implementation in progress
NOSSDAV ’02
patent process in progress
initial discussions with Digital Media Division

5. Research Activities (contd.)
PeerMetric (with Karthik Lakshminarayanan)
characterize broadband network performance
P2P as well as client-server performance
working with Xbox Online (Mark VanAntwerp)
deployment on ~25 distributed nodes underway
eventual deployment on ~300 Xbox Live beta users
Future directions
CoopNet in a Wireless Mesh Network
good synergy: saves Internet bandwidth, improves robustness

6. Robustness of Live Streaming
Peers are not dedicated servers  potential disruption due to:
node departures and failures
higher priority traffic
Traditional ALM is not sufficient

7. Traditional Application-level Multicast

8. CoopNet Approach to Robustness
Multiple description coding (MDC)
Multiple, diverse distribution trees

9. Multiple Description Coding
MDC
Layered coding
Unlike layered coding, there isn’t an ordering of the descriptions
Every subset of descriptions must be decodable
Modest penalty relative to layered coding

10. Multiple Description Coding
Simple MDC:
every Mth frame forms a description
More sophisticated MDC combines:
layered coding
Reed-Solomon coding
priority encoded transmission
optimized bit allocation

11. Multiple Distribution Trees

12. Tree Management Goals:
short and wide trees
efficiency
diversity
quick join and leave processing
scalability
CoopNet approach: centralized protocol anchored at the server

13. Centralized Tree Management
Basic protocol
nodes inform server of their arrival/departure
server tracks node capacity and tells new nodes where to join
each node monitors its packet loss rate and takes action when the loss rate becomes too high
simple, should scale to joins/leaves per sec.
Optimizations
delay coordinates to estimate node proximity (à la GeoPing)
achieving efficiency and diversity
migrate “stable” nodes to a higher level in the tree

14. Achieving Efficiency and Diversity
SEA NY S
Supernode SF

15. MDC versus SDC
Based on MSNBC traces from Sep 11

16. CoopNet Transport Architecture
Embedded Stream
ZSF
GOF
Parse
Packetize
Optimize
(M, p(m)) RD
Curve
Break Points
M descriptions
RS Encoder
Server
Internet
Depacketize
Embedded Stream (truncated)
Reformat
Decode
Render
GOF (quality depends on # descriptions received)
m≤ M descriptions
RS Decoder
Client

17. Summary Robustness is the key challenge
MDC with multiple distribution trees improves robustness in peer-to-peer media streaming
Centralized tree management is efficient and can scales

18. Current Activity CoopNet media streaming system is being built
Evaluation:
adaptability
server scalability
media stream quality
overhead in MDC and control protocol
Dealing with client heterogeneity
combine MDC with layering

19. Issues Firewall and NAT traversal Digital Right Management issues
ISP pricing policies
Enterprise scenarios

20. Quality During Multiple Failures

21. Quality During Single Failure