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TOMA: A Viable Solution for Large-Scale Multicast Service
SupportLi Lao, Jun-Hong Cui, and Mario GerlaUCLA and University of Connecticut
Networking 2005
Presented by Kyungmin Cho2005/10/19
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 hostst
0
g0
g0g1
g3
g3
Member proxy
Member proxy
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
g3
g1
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
g0
g1
g0
g3
g3
IP addresses ofmember 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(g
1)
O-JOIN-ACK(g1, t0)
O-GRAFT(t
0)
g3
Group-tree matchingg1
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
g0g1
g3
g3
Tree Groups
t1 g3
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 c
an share one tree
• Dynamic Group-Tree Matching Algorithm– average percentage bandwidth overhead for tree t
– bth 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 bth 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 to 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 lo
w 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 router
s• 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 wi, end hosts are attached with a pr
obability proportional to wi
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