TOMA: A Viable Solution for Large- Scale Multicast Service Support Li Lao, Jun-Hong Cui, and Mario Gerla UCLA and University of Connecticut Networking 2005 Presented by Kyungmin Cho 2005/10/19

Korea Advanced Institute of Science and Technology Network Computing Laboratory 2/21 Contents One Line Comment Motivation Problem Solution Approach Experiments Conclusion Critique

Korea Advanced Institute of Science and Technology Network Computing Laboratory 3/21 One Line Comment This paper presents Two-tier Overlay Multicast Architecture (TOMA) to provide scalable and efficient multicast support for various group communication applications

Korea Advanced Institute of Science and Technology Network Computing Laboratory 4/21 Motivation(1/2) IP multicast –the lack of a scalable inter-domain routing protocol –the state scalability issue with a large number of groups –the lack of support in access control –the requirement of global deployment of multicast-capable IP routers –the lack of appropriate pricing models Application-layer multicast –generally not scalable to support large multicast groups relatively low bandwidth efficiency heavy control overhead –hard to have an effective service model for ISP difficult to have efficient member access control not easy to obtain the knowledge of the group bandwidth usage

Korea Advanced Institute of Science and Technology Network Computing Laboratory 5/21 Motivation (2/2) Who care about a practical solution for large- scale multicast support? –Network service providers (or higher-tier ISPs) ? –Internet Service Providers (or lower-tier ISPs) ? –End users? ISPs in the middle want to use limited bandwidth purchased from network service providers to support as many users as possible

Korea Advanced Institute of Science and Technology Network Computing Laboratory 6/21 Problem How to provide scalable, efficient, and practical multicast support for various group communication applications

Korea Advanced Institute of Science and Technology Network Computing Laboratory 7/21 Solution Approach Two-tier Overlay Multicast Architecture (TOMA) –MSON (Multicast Service Overlay Network) node is deployed by MSON provider (ISP) –end hosts (group members) subscribe to MSON by transparently connecting to some special proxies MSON Node End hosts t0 g0 g1 g3 Member proxy g1 g0 g1 g0

Korea Advanced Institute of Science and Technology Network Computing Laboratory 8/21 Issues Efficient management of MSON –How does an MSON provider efficiently establish and manage numerous multicast trees? Cluster formation outside MSON –How should members select and subscribe to appropriate member proxies? –How are efficient clusters formed among end users? MSON dimensioning –Where should the overlay proxies be placed? –How much bandwidth should be reserved on each link? Pricing –How to charge the users of MSON?

Korea Advanced Institute of Science and Technology Network Computing Laboratory 9/21 OLAMP for Efficient MSON Management Aggregated Tree MSON Node End hosts DNS Server (Group Registry Server) t0 (g0, g1) t1 (g3) Host Proxy of g0 Host Proxy of g3 g0 g3 g1 g0 g1 g0

Korea Advanced Institute of Science and Technology Network Computing Laboratory 10/21 OLAMP for Efficient MSON Management Member Join; Before selecting a member proxy MSON Node End hosts DNS Server (Group Registry Server) TOMA://groupname.xyzmson.com/ t0 (g0, g1) t1 (g3) Host Proxy of g0 Host Proxy of g3 g1 g0 g1 g0 g3 IP addresses of member proxies g1

Korea Advanced Institute of Science and Technology Network Computing Laboratory 11/21 OLAMP for Efficient MSON Management Member Join; After selecting a member proxy host proxy End hosts t0 (g0, g1) t1 (g3) t0 t1 g0 g1 g3 O-JOIN(g1) O-JOIN-ACK(g1, t0) O-GRAFT(t0) g3 Group-tree matching g1 g0 g1 g0

Korea Advanced Institute of Science and Technology Network Computing Laboratory 12/21 Member Leave host proxy End hosts t0 (g0, g1) t1 (g3) t0 t1 g0 g1 g3 TreeGroups t1g3 Group-Tree Matching Table O-LEAVE(g3) X O-LEAVE-ACK(t1) O-PRUNE(t1) Leave OLAMP for Efficient MSON Management g1 g0 g1 g0

Korea Advanced Institute of Science and Technology Network Computing Laboratory 13/21 A trade-off between bandwidth waste and aggregation –the more bandwidth we are willing to sacrifice, the more groups can share one tree Dynamic Group-Tree Matching Algorithm –average percentage bandwidth overhead for tree t –b th is a bandwidth overhead threshold –Algorithm if g is not new and the current tree t for group g is still appropriate (t can cover g, enough bandwidth, and b th is OK), t is used for g else, check if any existing tree is appropriate for g –If so, the one with the minimum cost is selected (O-SWITCH(g, t, t’)) –else, the native tree t o is used to cover g OLAMP for Efficient MSON Management

Korea Advanced Institute of Science and Technology Network Computing Laboratory 14/21 Cluster Formation Outside MSON Member Proxy Selection –An end user selects one proxy based on the criteria of low latency and low workload –measure the RTT by sending ping requests –In the reply, the proxy piggybacks its workload information the total number of end users the total amount of access bandwidth in use P2P Multicast in Access Networks –the member proxy stores the group membership information end users monitor its peers (delay, available bandwidth) and reports this information to its member proxy –the member proxy computes P2P multicast delivery trees and disseminates the (parent, children) entries to the members –end users connect with their children and transmit data packets via unicast

Korea Advanced Institute of Science and Technology Network Computing Laboratory 15/21 Experiments Experiments in NS-2 compare TOMA with –(1) NICE, (2) IP multicast, and (3) unicast Simulation Settings –Transit-Stub topologies 50 transit domain routers and 500-2,000 stub domain routers End hosts are attached to stub routers uniformly at random –topology abstracted from real network topology, AT&T backbone 54 routers each router has a weight w i, end hosts are attached with a probability proportional to w i

Korea Advanced Institute of Science and Technology Network Computing Laboratory 16/21 Experiments Multicast Tree Performance –total number of links in a multicast tree

Korea Advanced Institute of Science and Technology Network Computing Laboratory 17/21 Experiments Multicast Tree Performance –average link stress, average path length

Korea Advanced Institute of Science and Technology Network Computing Laboratory 18/21 Experiments Control Overhead

Korea Advanced Institute of Science and Technology Network Computing Laboratory 19/21 Experiments Effectiveness of MSON Management Protocol

Korea Advanced Institute of Science and Technology Network Computing Laboratory 20/21 Conclusion A Two-tier Overlay Multicast Architecture (TOMA) –group communication applications –infrastructure-supported overlays facilitate the deployment of multicast server –MSON as the backbone service domain and P2P multicast in the access domains efficient resource utilization with reduced control overhead –OLAMP for MSON management the control overhead for establishing and maintaining multicast tress are significantly reduced far less forwarding state

Korea Advanced Institute of Science and Technology Network Computing Laboratory 21/21 Critiques Strong Points –address the issue of who is responsible for deploying multicast service –supporting numerous groups having a large number of members –Dynamic group tree matching algorithm Weak Points –messages which is required for a subset of members are also delivered to all members through network fine grained-filtering should be performed at end hosts