1. Multicasting in Mobile Ad hoc Networks By XIE Jiawei

2. What is Multicast in MANET (1) Multicasting is the transmission of datagrams to a group of mobile hosts identified by a single multicast destination address and hence is intended for group-oriented computing. In our research, IP multicast is used, i.e., each multicast group is associated with a unique IP multicast address (class D)

3. What is Multicast in MANET (2) Multicast route Wireless link Wirelesslink Mobile nodes that can be reached via wireless link Mobile nodes that cannot be reached via wireless link due to mobility Multicast receiver Multicast sender

4. Why Multicast in MANET There are applications such military battlefields, emergency search and rescue sites, classrooms, and conventions where participants share information dynamically using their mobile devices that lend themselves well to multicast operations Multicasting can improve the efficiency of the wireless links, when sending multiple copies of messages, by exploiting the inherent broadcast property of the wireless medium when multiple mobile nodes are located within the transmission range of a node. Improved transmission efficiency can reduce energy consumption, which is a important consideration in MANETs

5. Specific Challenges in designing a Multicast Protocol How to cope with unconstrained (high) mobility How to manage membership How to reduce transmission redundancy How to reduce control overhead How to guarantee reliable delivery

6. Multicast Topology: Group- Shared Tree (1) Group-shared tree Constructs one single tree for a multicast group even if there are more than one source Uses less memory Gets possibly sub-optimal paths from a source to receivers Introduces possibly extra delay

7. Multicast Topology: Source- Based Tree Source-based tree Constructs an individual tree for each sender in a multicast group Gets optimal paths from a source to receivers Minimizes delay Uses more memory

8. Multicast Topology: Comment on Tree Advantages: Less overhead when delivering data packets Lower probability for congestions, collisions in a network with a medium contention feature Disadvantage: Vulnerability to mobility, resulting in higher control overhead and unreliability

9. Multicast Topology: Mesh (1) Mesh: multiple paths exist between any sender and receiver pair One possible way to implement mesh is using the concept of forwarding group: only a subset of nodes forward multicast packets

10. Multicast Topology: Comment on Mesh Advantages Robust Simple Disadvantage Enormous redundant packet deliveries: congestions, collisions, etc. Performance goes down drastically when there are more than 1 source

11. Research direction Objective: Design a multicast protocol for MANET with following improvements Less redundancy in packet delivery Enhanced performance when multiple sources exist (reliability) Adaptivity to failure, mobility, partitions, etc.