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AD HOC WIRELESS MUTICAST ROUTING

AD HOC WIRELESS MUTICAST ROUTING. Multicasting in wired networks. In wired networks changes in network topology is rare But for mobile ad hoc networks changes are frequent. Multicasting in wired networks.

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AD HOC WIRELESS MUTICAST ROUTING

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  1. AD HOC WIRELESSMUTICAST ROUTING

  2. Multicasting in wired networks • In wired networks changes in network topology is rare • But for mobile ad hoc networks changes are frequent

  3. Multicasting in wired networks • If two communications nodes are within radio range of each other these connections can be direct connections • Otherwise, use multi-hop connections

  4. Multicasting in wired networks • Because every mobile node can move, changes in network topology are frequent. • The bandwidth of wireless links is an order of magnitude lower than that of wired links.

  5. Multicasting in wired networks • New routing protocols for both unicast and multicast communications are required. • Highly adaptive to be able to cope with highly dynamic network conditions. • Low control overhead and power consumption.

  6. Multicasting in wired networks • IP multicast architecture • MBone[60]

  7. IP multicast architecture • In 1989, Deering[61] proposed. • Enable point to multipoint communications in TCP/IP networks. • Multicast group is identified by a single IP address.

  8. IP multicast architecture • Receiver needs to join and become a member of a particular multicast group. But sender doesn’t need. • Deliveries of multicast packets from multicast senders to all intended multicast members are handled by network, with help from multicast routing protocol.

  9. IP multicast architecture • All routers in the network are required to support multicast routing. • the fact that multicast senders have no control over the multicast delivery process can make administrative and security policies cumbersome.

  10. Multicast Tunnels and MBone • The requirement that every router in the network must be multicast-enabled has prohibited large-scale multicast deployment in the internet. • Multicast traffic is encapsulated in unicast packets and transmitted from one multicast network to another network, where it is decapsulated and process as multicast packets.

  11. Multicast Tunnels and MBone • The connection through which the encapsulated packets are transmitted is called the multicast tunnel, or mtunnel. • Shown in figure 10.1

  12. Multicast Tunnels and MBone

  13. Multicast routing algorithms • Source-base shortest-path multicast tree • Broadcast-and-prune technique • RPF (reverse path forwarding) mechanism

  14. Reverse path forwarding

  15. Multicast routing algorithms • Single shared tree per multicast group • CBT( Cored Based Trees) • PIM-SM( Protocol Independent Multicast Sparse Mode)

  16. Multicast routing in mobile ad hoc networks • Based on multicast delivery structure • flooding • Sourced-Based Multicast Tree • Core-Based Multicast Tree(CBT) • Multicast Mesh • Group-Based Multicast Forwarding

  17. Flooding • Multicast packet is globally flooded to all nodes in network. • Well suited to networks with high mobility. • Bandwidth is wasted and unnecessary forwarding of duplicate data.

  18. Source-Based Multicast Tree(SBT) • Multicast tree is established for each multicast source node. • Each multicast packet is forwarded along the most efficient path from the source to each member. • A lot of overhead is incurred in establishing multicast tree.

  19. Source-Based Multicast Tree • DVMRP • MOSPF • PIM-DM

  20. Core-Based Multicast Tree(CBT) • A single shared tree is used to connect all multicast group members. • A special node is designated as the cored node. • The tree can be either unidirectional or bidirectional.

  21. Core-Based Multicast Tree(cont.) • In unidirectional shared tree, multicast packets must be unicast to the core node. • In bidirectional shared tree,multicast packets can enter the tree at any point.

  22. Core-Based Multicast Tree(cont.) • More efficient in communication performance and forwarding overhead. • Result in high tendency for congestion at the shared links. • CBT, PIM-SM, AmRoute[71], AMRIS, and AODV[26].

  23. Multicast Mesh • Establish a mesh for each multicast group. • A mesh is different from a tree since each node can have multiple parents. • Provide multiple redundant path, avoiding frequent mesh reconfigurations. • Unnecessary forwarding of multicast packets.

  24. Group-Based Multicast Forwarding • A group of nodes acts as multicast forwarding nodes for each multicast group. • A group of nodes is maintained instead of the links that constitute the tree or mesh.

  25. Group-Based Multicast Forwarding • Multicast packets are forwarded only by forwarding nodes. • All received multicast packets that are not duplicated are rebroadcast by the forwarding nodes to their neighbors.

  26. Group-Based Multicast Forwarding • Few states are kept at each intermediate node and redundant paths are available. • ODMRP(On Demand Multicast Routing Protocol).

  27. Ad hoc multicast routing protocol

  28. DVMRP with Wireless Extension • To function more efficient in a mobile ad hoc environment. • These extensions are: • leaf-node detection • Dynamic grafting/pruning • The use of packet duplication

  29. DVMRP with Wireless Extension • Flooding the whole network with the multicast traffic. • The leaf node which is not interest in that particular multicast group will send prune message upstream.

  30. DVMRP with Wireless Extension • The intermediate node receiving this prune message will mark that particular link as “pruned-off” and will not forward any subsequent multicast packets of the corresponding session onto that link.

  31. DVMRP with Wireless Extension • Once this prune message is completed, the optimal source-base tree is established.

  32. Join/leave operation • Periodically , the timer on the pruned branch will expire and the multicast traffic will be flooded again. • This mechanism incurs latency when new members wish to join the group since a new member has to wait until the next flooding period.

  33. Grafting /pruning • Dynamic grafting is provided to allow a member to quickly join the multicast group. • In dynamic grafting/pruning, when a node detects that the shortest path back to the multicast source node has changed, it will send a prune message to the current upstream node and a graft message to the new upstream node.

  34. ODMRP • Flooding-based multicast routing protocol for mobile ad hoc network. • Data is flooded only throughout the forwarding group. • Forwarding group is a set of ad hoc nodes specially chosen to forward multicast traffic for a particular multicast group.

  35. ODMRP • ODMRP depends on the following operations: • multicast sender advertisement • JOIN-TABLE broadcast by multicast receivers.

  36. ODMRP • When a multicast sender has data to send , it starts the periodic broadcast of JOIN-REQUEST message. • Each node , upon receiving the JOIN-REQUEST message, will update routing table with the address of the node from which the JOIN-REQUEST message is received.

  37. ODMRP • When a multicast receiver receives the JOIN-REQUEST message , it will update its member table with of the multicast sender and periodically broadcast JOIN-TABLE message. • Only the node listed as the next-hop in the JOIN-TABLE message will process the JOIN-TABLE message.

  38. ODMRP

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