A Case for End System Multicast Yang-hua Chu, Sanjay G. Rao, Srinivasan Seshan and Hui Zhang Presentation by Warren Cheung Some Slides from ar/2000/%EC%9D%B4%EB%AF%BC%ED% 98%B8/5

Multicast  Unicast: – Point to Point delivery – One Host to One Client  Multicast: – Deliver to multiple destinations – One Host to Many Clients

IP vs. End System Multicast  IP multicast – Implemented at Internetworking layer  Routers and switches  End System multicast – Implemented in the hosts and clients

Examples

Examples – IP Multicast

Examples – naive Unicast

Examples – End System Multicast

Considerations  Transmission Redundancy of Data – Unicast: many copies per link – IP Multicast: one copy per link – End System Multicast:  slightly more inefficient than IP Multicast  Delay – Unicast same as IP Multicast – End System Multicast incurs penalty

IP multicast  Pros – Possibly large performance benefits  Cons – Needs to maintain “group state” – Infrastructure level changes are slow to deploy

End System Multicast  Pros – Can be implemented now  Hosts (Peer-to-Peer)  Proxy  Cons – Performance degradation

Narada Protocol  Self-Organising – Constructs Overlay – Adapt to Network/Group Dynamics  Efficient – Latency vs. Bandwidth – Self-improving

Group Management  Everyone keeps the member list – Target Medium-Sized Groups – Everyone periodically exchanges group information with neighbours (refresh)  Join – Bootstrapping  Leave – Partition repair

Mesh Performance  Mesh may be suboptimal due to: – Network conditions – Group dynamics  Adding random neighbours  Dropping low “cost” links

Open Issues  Group size on Average overlay hops  Short-term Effects of events on Performance  Overlay construction/maintenance costs when group sizes get very large

Related Work on Overlays  Mesh-based  Tree-based overlays  Delaunay Triangulations – Map addresses to coordinate space – Find closest neighbours  Hierarchies of Clusters

Related Works  End System Multicast, Narada, Video Streaming –  Comparison of some Application Layer Multicast solutions – mparative.html

Not-So-Closely Related Works  BitTorrent (File Swarming) –  Herbivore (Anonymity/Security) – ore.html

Discussion  IP Multicast – Basically a failure – deployment issues – Any fundamental/low level changes to Internet infrastructure unlikely to succeed  End System Multicast – Overhead/performance impact no longer looks as disadvantageous as it originally appeared

Discussion(2)  Applications – Limitations to video-conferencing more due to limitation on the number of people you can communicate with simultaneously – For large number of clients, more likely to be a broadcast  Narada – Implemented and used – Broadcasts the annual SIG networking conference