AD HOC WIRELESS MUTICAST ROUTING

AD HOC WIRELESSAD HOC WIRELESSMUTICAST ROUTINGMUTICAST ROUTING

Multicasting in wired networksMulticasting in wired networks

In wired networks changes in In wired networks changes in network topology is rarenetwork topology is rare

But for mobile ad hoc networks But for mobile ad hoc networks changes are frequentchanges are frequent


If two communications nodes are If two communications nodes are within radio range of each other within radio range of each other these connections can be direct these connections can be direct connectionsconnections

Otherwise, use multi-hop connectionsOtherwise, use multi-hop connections


Because every mobile node can Because every mobile node can move, changes in network topology move, changes in network topology are frequent.are frequent.

The bandwidth of wireless links is an The bandwidth of wireless links is an order of magnitude lower than that order of magnitude lower than that of wired links.of wired links.


New routing protocols for both unicast aNew routing protocols for both unicast and multicast communications are requirnd multicast communications are required.ed.

Highly adaptive to be able to cope with Highly adaptive to be able to cope with highly dynamic network conditions.highly dynamic network conditions.

Low control overhead and power consuLow control overhead and power consumption.mption.


IP multicast architecture IP multicast architecture MBone[60]MBone[60]

IP multicast architectureIP multicast architecture

In 1989, Deering[61] proposed.In 1989, Deering[61] proposed. Enable point to multipoint Enable point to multipoint

communications in TCP/IP networks.communications in TCP/IP networks. Multicast group is identified by a Multicast group is identified by a

single IP address.single IP address.


Receiver needs to join and become a Receiver needs to join and become a member of a particular multicast member of a particular multicast group. But sender doesn’t need.group. But sender doesn’t need.

Deliveries of multicast packets from Deliveries of multicast packets from multicast senders to all intended multicast senders to all intended multicast members are handled by multicast members are handled by network, with help from multicast network, with help from multicast routing protocol.routing protocol.


All routers in the network are All routers in the network are required to support multicast routing.required to support multicast routing.

the fact that multicast senders have the fact that multicast senders have no control over the multicast delivery no control over the multicast delivery process can make administrative and process can make administrative and security policies cumbersome.security policies cumbersome.

Multicast Tunnels and MBoneMulticast Tunnels and MBone

The requirement that every router in the The requirement that every router in the network must be multicast-enabled has network must be multicast-enabled has prohibited large-scale multicast deployprohibited large-scale multicast deployment in the internet.ment in the internet.

Multicast traffic is encapsulated in unicaMulticast traffic is encapsulated in unicast packets and transmitted from one must packets and transmitted from one multicast network to another network, whelticast network to another network, where it is decapsulated and process as multre it is decapsulated and process as multicast packets.icast packets.


The connection through which the encaThe connection through which the encapsulated packets are transmitted is callepsulated packets are transmitted is called the multicast tunnel, or mtunnel.d the multicast tunnel, or mtunnel.

Shown in figure 10.1Shown in figure 10.1

Multicast routing algorithmsMulticast routing algorithms

Source-base shortest-path multicast Source-base shortest-path multicast treetree• Broadcast-and-prune techniqueBroadcast-and-prune technique• RPF (reverse path forwarding) RPF (reverse path forwarding)

mechanismmechanism

Reverse path forwarding Reverse path forwarding

Multicast routing algorithmsMulticast routing algorithms

Single shared tree per multicast Single shared tree per multicast groupgroup• CBT( Cored Based Trees) CBT( Cored Based Trees) • PIM-SM( Protocol Independent Multicast PIM-SM( Protocol Independent Multicast

Sparse Mode)Sparse Mode)

Multicast routing in mobile ad hoc Multicast routing in mobile ad hoc networksnetworks

Based on multicast delivery structure Based on multicast delivery structure floodingflooding Sourced-Based Multicast TreeSourced-Based Multicast Tree Core-Based Multicast Tree(CBT)Core-Based Multicast Tree(CBT) Multicast Mesh Multicast Mesh Group-Based Multicast Forwarding Group-Based Multicast Forwarding

FloodingFlooding

Multicast packet is globally flooded Multicast packet is globally flooded to all nodes in network.to all nodes in network.

Well suited to networks with high Well suited to networks with high mobility.mobility.

Bandwidth is wasted and Bandwidth is wasted and unnecessary forwarding of duplicate unnecessary forwarding of duplicate data.data.

Source-Based Multicast Tree(SBT)Source-Based Multicast Tree(SBT)

Multicast tree is established for each Multicast tree is established for each multicast source node.multicast source node.

Each multicast packet is forwarded Each multicast packet is forwarded along the most efficient path from along the most efficient path from the source to each member.the source to each member.

A lot of overhead is incurred in A lot of overhead is incurred in establishing multicast tree.establishing multicast tree.

Source-Based Multicast TreeSource-Based Multicast Tree

DVMRPDVMRP MOSPFMOSPF PIM-DMPIM-DM

Core-Based Multicast Tree(CBCore-Based Multicast Tree(CBT)T)

A single shared tree is used to A single shared tree is used to connect all multicast group connect all multicast group members.members.

A special node is designated as the A special node is designated as the cored node.cored node.

The tree can be either unidirectional The tree can be either unidirectional or bidirectional.or bidirectional.

Core-Based Multicast Tree(cont.)Core-Based Multicast Tree(cont.)

In unidirectional shared tree, multicast In unidirectional shared tree, multicast packets must be unicast to the core nodpackets must be unicast to the core node.e.

In bidirectional shared tree,multicast paIn bidirectional shared tree,multicast packets can enter the tree at any point.ckets can enter the tree at any point.

Core-Based Multicast Tree(cont.)Core-Based Multicast Tree(cont.)

More efficient in communication More efficient in communication performance and forwarding performance and forwarding overhead.overhead.

Result in high tendency for Result in high tendency for congestion at the shared links.congestion at the shared links.

CBT, PIM-SM, AmRoute[71], AMRIS, CBT, PIM-SM, AmRoute[71], AMRIS, and AODV[26].and AODV[26].

Multicast MeshMulticast Mesh

Establish a mesh for each multicast Establish a mesh for each multicast group.group.

A mesh is different from a tree since A mesh is different from a tree since each node can have multiple parents.each node can have multiple parents.

Provide multiple redundant path, Provide multiple redundant path, avoiding frequent mesh avoiding frequent mesh reconfigurations.reconfigurations.

Unnecessary forwarding of multicast Unnecessary forwarding of multicast packets.packets.

Group-Based Multicast ForwardingGroup-Based Multicast Forwarding

A group of nodes acts as multicast forwaA group of nodes acts as multicast forwarding nodes for each multicast group.rding nodes for each multicast group.

A group of nodes is maintained instead A group of nodes is maintained instead of the links that constitute the tree or mof the links that constitute the tree or mesh.esh.


Multicast packets are forwarded only Multicast packets are forwarded only by forwarding nodes.by forwarding nodes.

All received multicast packets that All received multicast packets that are not duplicated are rebroadcast are not duplicated are rebroadcast by the forwarding nodes to their by the forwarding nodes to their neighbors.neighbors.


Few states are kept at each intermediatFew states are kept at each intermediate node and redundant paths are available node and redundant paths are available.e.

ODMRP(On Demand Multicast Routing PODMRP(On Demand Multicast Routing Protocol).rotocol).

Ad hoc multicast routing protocolAd hoc multicast routing protocol

DVMRP with Wireless ExtensionDVMRP with Wireless Extension

To function more efficient in a To function more efficient in a mobile ad hoc environment.mobile ad hoc environment.

These extensions are:These extensions are:a.a. leaf-node detectionleaf-node detection

b.b. Dynamic grafting/pruningDynamic grafting/pruning

c.c. The use of packet duplication The use of packet duplication


Flooding the whole network with the Flooding the whole network with the multicast traffic.multicast traffic.

The leaf node which is not interest in The leaf node which is not interest in that particular multicast group will that particular multicast group will send prune message upstream.send prune message upstream.


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


Once this prune message is Once this prune message is completed, the optimal source-base completed, the optimal source-base tree is established.tree is established.

Join/leave operationJoin/leave operation

Periodically , the timer on the pruned Periodically , the timer on the pruned branch will expire and the multicast branch will expire and the multicast traffic will be flooded again.traffic will be flooded again.

This mechanism incurs latency when This mechanism incurs latency when new members wish to join the group new members wish to join the group since a new member has to wait until since a new member has to wait until the next flooding period.the next flooding period.

Grafting /pruningGrafting /pruning

Dynamic grafting is provided to allow a Dynamic grafting is provided to allow a member to quickly join the multicast member to quickly join the multicast group.group.

In dynamic grafting/pruning, when a node In dynamic grafting/pruning, when a node detects that the shortest path back to the detects that the shortest path back to the multicast source node has changed, it will multicast source node has changed, it will send a prune message to the current send a prune message to the current upstream node and a graft message to the upstream node and a graft message to the new upstream node.new upstream node.

ODMRPODMRP

Flooding-based multicast routing Flooding-based multicast routing protocol for mobile ad hoc network.protocol for mobile ad hoc network.

Data is flooded only throughout the Data is flooded only throughout the forwarding group.forwarding group.

Forwarding group is a set of ad hoc Forwarding group is a set of ad hoc nodes specially chosen to forward nodes specially chosen to forward multicast traffic for a particular multicast traffic for a particular multicast group.multicast group.

ODMRPODMRP

ODMRP depends on the following ODMRP depends on the following operations:operations:

a)a) multicast sender advertisementmulticast sender advertisement

b)b) JOIN-TABLE broadcast by multicast JOIN-TABLE broadcast by multicast receivers.receivers.

ODMRPODMRP

When a multicast sender has data to When a multicast sender has data to send , it starts the periodic broadcast send , it starts the periodic broadcast of JOIN-REQUEST message.of JOIN-REQUEST message.

Each node , upon receiving the JOIN-Each node , upon receiving the JOIN-REQUEST message, will update REQUEST message, will update routing table with the address of the routing table with the address of the node from which the JOIN-REQUEST node from which the JOIN-REQUEST message is received.message is received.

ODMRPODMRP

When a multicast receiver receives When a multicast receiver receives the JOIN-REQUEST message , it will the JOIN-REQUEST message , it will update its member table with of the update its member table with of the multicast sender and periodically multicast sender and periodically broadcast JOIN-TABLE message.broadcast JOIN-TABLE message.

Only the node listed as the next-hop Only the node listed as the next-hop in the JOIN-TABLE message will in the JOIN-TABLE message will process the JOIN-TABLE message.process the JOIN-TABLE message.

ODMRPODMRP

AD HOC WIRELESS MUTICAST ROUTING

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