1. APPLICATION LAYER MULTICASTINGBY
D.Jayasakthi

2. Content The Evolution of Multicast Applications of Multicast
IP Multicast
Application Layer Multicast
Application Layer Multicast Protocol Design
Conclusion

3. The Evolution of Multicast
Std IP Multicast Model
1988
1992
Multicast Backbone (MBone)
Intra-Domain Multicast
1994
1997
Inter-Domain Multicast

4. Applications of Multicast
Distance Learning
A scene from the famous network game “Shrine of the Ancient”
Multimedia conferencing

5. Data Delivery Unicast: Broadcast: Multicast:
One source to one destination
Broadcast:
One source to all destination
Multicast:
One source to many destinations(but not all)
Many source to many destinations

6. Multi- Unicast
Unicast
Source
Router
Receiver

7. IP Multicast
Distribute information to large audiences over an IP network

8. IP Multicast
Source
IP Multicast
Router
Receiver

9. Deployment Issues with IP Muticasting
IP Multicast-capable routers need to be installed at all levels of the network (from backbone to edge routers) for the multicasting service to work.
There also exist management and security issues related to the deployment of IP Multicast:
The ease of flooding attacks via multicasting
Unauthorized reception of data from a multicast session
Preventing allocation of same multicast address for two sessions
The difficulty of setting up firewalls while allowing multicasting.
The lack of network-level support for multicasting has thus led researchers and commercial entities to seek alternative ways of multicasting at the application layer.

10. Application Layer Multicasting(ALM)
IP Multicast is not globally deployed.
Application Layer/Level Multicast (or Overlay Multicast) is hence proposed.
Multicasting implemented at end hosts instead of network routers
Nodes form Unicast channels or tunnels between them S R1 R2 E1 E2 E3
Unicast

11. ALM Benefits Easy to deploy No change to network infrastructure
Programmable end-hosts
Overlay construction algorithms at end hosts can be easily applied
Easier maintenance.

12. IP Multicast vs. ALM

13. IP Multicast vs. ALM

14. APPLICATION LAYER MULTICAST PROTOCOL DESIGN
Application Domain
Deployment Level
Group Management
Routing Mechanism

15. Application Domain
Different classes of applications have different sets of requirements regarding Reliability, Latency, Bandwidth, and Scaling. Such requirements in turn determine the design choices of ALM protocol regarding the group management mechanism it deploys.
The application domain therefore influences the ALM protocol.

16. Deployment Level 2 levels of Deployment: Infrastructure Level
End System Level

17. Group Management
How to manage a group of nodes in a multicast session?
Basic group management:
How users find out about multicast sessions?
How they join a session?
How they leave?
Centralized or Distributed way
Mesh-first approach or a Tree-first approach
Source Specific Tree or Shared Tree
Whether the protocol will take advantage of existing IP Multicast islands?
Whether it is necessary to refine the multicast tree to improve performance?

18. Routing
Design of the routing mechanism typically involves a (heuristic) solution to a graph theory problem.
The most important is the routing mechanisms.
Some Common approaches to the routing mechanism are
1: Shortest Path
2: Minimum Spanning Tree
3: Clustering Structure
4: Peer-to-Peer Structure

19. Shortest Path
The aim is to construct degree constraint minimum diameter spanning tree
A Shortest Path Tree (SPT) constructs a minimum cost path from a source node to all its receivers.

20. Minimum Spanning Tree
Given a graph with a cost associated with each edge (usually delay), a Minimum Spanning Tree (MST) is a tree with minimum total cost spanning all the members 2

21. Clustering Structure
This group constructs a cluster of nodes that can be used to construct trees.

22. Clustering Structure
In order to better organize the overlay tree and reduce control message overhead, some ALM protocols such as ZIGZAG and NICE construct a hierarchical cluster of nodes.
The advantage of a hierarchical clustering approach to multicast tree routing is the reduction in control overhead and faster joining.

23. Peer-to-Peer Structure
In P2P structure, the routing is simply done through reverse- path forwarding or forward- path forwarding or in some cases a combination of both type.
The advantage of these approaches includes low control overhead and distributed management of the multicast tree but they do not restrict the degree of each node and are suboptimal.

24. Conclusion
Compared to IP multicasting, ALM has certain disadvantages such as longer delays and less efficient traffic generation.
However, due to its overwhelming advantages for certain applications, such as immediate deploy-ability and application- specific adaptation, it can be a practical solution to many of the existing problems in multi-user communications.
The fact that an ALM protocol can be developed and deployed on the Internet without the need to make any changes to the existing network infrastructure, and the ability to evolve and apply modifications to the protocol quickly and easily at the application layer has helped the ALM approach to have a quicker start compared to other multi-user communications solutions.

25. References
"A Survey of Application-Layer Multicast Protocols", Mojtaba Hosseini, Dewan Tanvir Ahmed, Shervin Shirmohammadi, Nicolas D. Georganas, IEEE Communications Surveys & Tutorials, Vol. 9, no. 3, July 2007, pp
S. Deering and D. Cheriton, “Multicast Routing in Datagram Internetworks and Extended LANS,” ACM Trans. Comp. Syst., vol. 8, no. 2, 1990, pp. 85– 111.
C. Diot et al., “Deployment Issues for the IP Multicast Service and Architecture,” IEEE Network Mag., vol. 14, no. 1, 2000, pp. 78–88.

26. Thank You