30-06-2012, 11:55 AM
Mobile and Wireless Computing
[attachment=26240]
Ad Hoc On-Demand Distance-Vector Protocol
Unicasting
The routing we have discussed so far is mainly point-to-point routing.
A source node wants to send a message to a destination node.
Multicasting
However, in many situations a node wants to send a message to a group of nodes in the network.
This is called multicasting and the group is called a multicast group.
Broadcasting
Broadcasting is a special case of multicasting when all the nodes in the network is in the multicast group.
Multicasting Support
DSDV and DSR mainly support unicast routing.
If multicasting is required, a node must establish unicast routes to each node in the multicast group.
A more efficient approach will maintain multicast routing trees for each multicast group.
Non-uniform Packet Size in DSR
Though DSR is a reactive or on-demand routing protocol, a major problem with DSR is its non-uniform packet size.
When a source node S sends a packet to a destination node D, S should send the entire route to D along with the packet.
This is necessary for the intermediate nodes to forward the packet.
Problem with Non-uniform Packet Size
Usually all media support packets of uniform size. If a packet is large, it has to be split into smaller packets.
This may cause problems in the wireless medium as packets that are split into smaller parts may not arrive in correct order.
Intermediate nodes may not be able to forward packets correctly.
[attachment=26240]
Ad Hoc On-Demand Distance-Vector Protocol
Unicasting
The routing we have discussed so far is mainly point-to-point routing.
A source node wants to send a message to a destination node.
Multicasting
However, in many situations a node wants to send a message to a group of nodes in the network.
This is called multicasting and the group is called a multicast group.
Broadcasting
Broadcasting is a special case of multicasting when all the nodes in the network is in the multicast group.
Multicasting Support
DSDV and DSR mainly support unicast routing.
If multicasting is required, a node must establish unicast routes to each node in the multicast group.
A more efficient approach will maintain multicast routing trees for each multicast group.
Non-uniform Packet Size in DSR
Though DSR is a reactive or on-demand routing protocol, a major problem with DSR is its non-uniform packet size.
When a source node S sends a packet to a destination node D, S should send the entire route to D along with the packet.
This is necessary for the intermediate nodes to forward the packet.
Problem with Non-uniform Packet Size
Usually all media support packets of uniform size. If a packet is large, it has to be split into smaller packets.
This may cause problems in the wireless medium as packets that are split into smaller parts may not arrive in correct order.
Intermediate nodes may not be able to forward packets correctly.