Study of the Relationship between Peer-to-Peer Systems and IP Multicasting T. Oh-ishi, K. Sakai, K. Kikuma, and A. Kurokawa NTT Network Service Systems Laboratories, NTT Corporation IEEE Communications Magazine, vol41(1), Jan Presented by Ho Tsz Kin 28/01/2004

Agenda Introduction Features of P2P Systems IP Multicasting over P2P Systems Routing Protocol Evaluation Conclusion

Introduction Peer-to-peer (P2P) systems Involve a number of directly connected “ peers ” exchanging various types of information among themselves Problems of P2P systems Not specific application Generate a lot of network traffic Require the resources of every peer (e.g. CPU, memory, and bandwidth)

Introduction IP multicasting Is mainly for live streaming services Can solve problems of P2P systems Applying IP multicasting to P2P systems Is it applicable? Is it worth? What is the suitable routing protocol? What happen when part of the network does not support IP multicasting?

Features of P2P Systems Current P2P systems Send broadcast packets or a series of identical unicast packets to peers Two types Hybrid P2P Pure P2P Two phases

Features of P2P systems Discovery phase Heavier traffic in Pure P2P system Delivery phase No differences between Pure and Hybrid P2P systems All peers must have the same messages. When new messages arrive, they should be passed on to all the other peers

Features of P2P systems P2P systems essentially require a broadcast mechanism use a series of unicast or broadcast packets Continuous unicast packets Need substantial CPU power and bandwidth of peers and all of the network resources Broadcast packets wasting various resources Security problem IP multicasting Solution for broadcast mechanism in P2P systems

IP multicasting over P2P Systems Almost all P2P application produce heavy traffic Reduction of such traffic using IP multicasting seems to be effective

IP multicasting over P2P Systems Comparison between live streaming and P2P systems Live StreamingP2P Systems Contents senderCan only be streaming servers All peers can be senders Opportunities to update member list Updating when content receivers joins/leaves Updating when content senders and receivers joins/leaves Types of traffic flowVideo streamsFew packets per event Range of propagation Intra-ISP or inter-ISP Number of content senders Smaller than the number of content receiver Same as the number of content receivers Join/leave of contents sender StaticallyDynamically

Routing Protocol PIM The protocols compose multicast trees using routing tables made by an arbitrary unicast routing protocol Protocol Independent Multicast-Sparse Mode (PIM-SM) Peers send IGMP join message to rendezvous point (RP) The multicast tree is originating from the RP When a peer sends multicast content, the packets is encapsulated by the closest edge router, and sent to RP

Routing Protocol PIM-Source Specific Multicast (PIM-SSM) Source-specific protocol The contents receiver can specify the addresses of desired sources in the IGMP join message When the closest edge router receives an IGMP join, it configures the shortest path between the receiver and the sender

Sequence for joining groups PIM-SM One IGMP join/leave to RP PIM-SSM Joining Send IGMP join to all senders Get all other peers to send it an IGMP join Leaving Send IGMP leave to all senders

Comparison of PIM-SM and PIM-SSM Conclude that PIM-SM is better for P2P systems PIM-SMPIM-SSM Load balancing By distributing RPsBy using a unicast routing protocol Router complexity Slightly more complex procedures Simpler Group- joining procedure simplerMore complex

Evaluation Simulation Model Members exchange information across two ISPs ISP-A does not support IP multicasting ISP-B support IP multicasting Only one router in each ISP All peers belong to a virtual group

Evaluation Simulation #1 Peers of ISP-A use unicast to all other peers Peers of ISP-B use unicast to peers of ISP-A and multicast to peers of ISP-B Simulation #2 Peers of ISP-A use unicast to peers of ISP-A, and send multicast packets to ISP-B ’ s RPs Peers of ISP-B use unicast to peers of ISP-A and multicast to peers of ISP-B

Conclusion Analyze features of P2P systems Suitable routing protocol is discussed IP multicasting is the solution for heavy traffic generated in P2P systems Future Works Sequence for joining/leaving groups Effect of RP ’ s location on traffic characteristics Multicast address allocation and traffic control methods for the entire network

Discussion Combining Peer-to-Peer and IP Multicasting The simulation details are not mentioned, e.g. traffic characteristics, duration, application Benefits of using IP multicasting over P2P systems