Impact of Topology on Overlay Multicast

1. Impact of Topology on Overlay Multicast Suat Mercan

2. Outline • Multicast IP Multicast Overlay Multicast • Performance Metrics • Simulator • Topology Generator

3. One to many communication • Multiple Unicast • Multicast R R S S R R R R

4. Why Multicast • Better bandwidth utilization (eliminates traffic redundancy) For the equivalent amount of multicast traffic, the sender needs much less processing power and bandwidth • Less host/router processing (reduces server and network load) Multicast packets do not impose as high a rate of bandwidth utilization as unicast packets, so there is a greater possibility that they will arrive almost simultaneously at the receivers

5. IP Multicast • Rely on network layer to replicate and deliver data packets to receivers

6. IP Multicast • Advantage:efficient data distribution • Difficulties: Limited router support Per-group/source state in routers Reliability difficulties Congestion-control difficulties Undefined pricing model • Alternative:application layer multicast, to control and maintain an efficient overlay for data transmission

7. Multicast Topology: Overlay A virtual network

8. Multicast Topology: Overlay Flexible Easy to implement Not as efficient as IP Multicast Mesh-based, tree-based

9. Mesh-based multiple paths exist between any sender and receiver pair Quick reconfigurable and robust Excessive message overhead

10. Tree-based Shared Multicast Tree Less control overhead Vulnerable to node failure

11. Overlay techniques

12. Overlay techniques Narada Yoid HostCast Directional Multicast

13. Factors that affect choice of multicast technique • Scalability • Fault tolerance • Performance • Quality of service • Security

14. Performance • Quality of data path Stress Stretch • Recovery from failure • Control traffic overhead

15. Performance • Stress Number of identical packets sent by the protocol over the same link. For IP Multicast there is no redundant packet replication • Stretch Resource usage • Control Overhead Each member on the overlay exchanges refresh messages with all its peers.

16. Simulation • P2P Sim • OverSim • PlanetSim • GPS • NS2

17. NS2 • Academic project over 10 years old freely distributed, open source • Based on C++ and TCL • Discrete event simulator • NAM, the Network AniMator • pre-processing: traffic and topology generators • post-processing: simple trace analysis

18. NS2

19. Topology Generation • BRITE • PLRG • INET • GT-ITM

20. GT-ITM • Georgia Tech Internet Topology Models • A collection of routines to generate and analyze graphs using a wide variety of models for internetwork topology • Waxman method, Transit-Stub method • Included as part of NS-2

21. GT-ITM

22. Our Project • Implement ‘Directional Multicast’ in NS-2 • Generate different topologies • Measure performance metrics under different topologies • Analyze how underlying topology affects performance

23. Thank You!