1. Multicast routing issues in ad hoc networks Katia Obraczka Gene Tsudik

2. Introduction A typical inter-network of the future will consist of a wired backbone and a collection of fixed infrastructure mobile and ad hoc networks. Multicast routing and packet forwarding protocols in ad hoc networks (AHN) must emphasize: Robustness versus efficiency. Active adaptability. Unlimited mobility. Integrated multicast.

3. Ad Hoc Network switch Base station Wired link Mobile host Wireless link Members of multicast group Fixed Network Ad Hoc Network Mobile Networks Inter-network of the future

4. Mobile networks and mobility patterns Mobile networks with fixed infrastructure. Ad hoc networks. Inter-networking comprising wired fixed infrastructure and ad hoc networks.

5. Issues in multicast routing in AHNs Fixed network multicast routing is based on state in routers; it is unsuitable for an AHN environment. Host behavior completely independent of other hosts. No limit on host speed. No constraints on direction of movement. High probability of frequent, temporary network partitions. Storage capacity and power are severely limited. Robustness and high quantity of service.

6. Hyper flooding: a potential approach Maximum network diameter is assumed to be known. Maximum TTL (time-to-time) for a packet is known. Multicast packets carry hop counts as well as origination time stamps. Each host only keeps its own multicast group membership information.

7. Hyper flooding: a potential approach (continued) Every multicast packet is assigned a unique ID. Each host maintains a cache of IDs. A packet is re-forwarded by the host only on new neighbors. A packet is not forwarded if there are no new neighbors.

8. Pruning unnecessary broadcasts ID=x 1 2 3 4 5 1 2 3 4 5 6 Time T1Time T2

9. 7 Incomplete coverage ID=x 1 2 3 4 5 1 2 3 4 5 6 Time T1Time T2

10. Accommodating different AHNs Large, widely distributed AHN The AHN is partitioned in to clusters. Each cluster is assigned a cluster head. Intra-cluster multicast is performed with hyper flooding. Inter-cluster multicast is by traditional multicasting.

11. Design of mobile wired multicast gateway. Design of Ad-hoc wired multicast gateway. Mechanisms for active switching among different multicast routing mechanism. Integration

12. Exploration of the design space of multicast routing algorithms suitable for AHNs. Development of multicast gateway. Prototyping and trial deployment. Summary