Preferred Link-Based Routing Protocol

PLBR

PLBR is a routing protocol with efficient flooding mechanisms. The main objective of PLBR is to find a single preferred link from the source to the destination node.
In PLBR each node owns a neighbor list (NL) which is updated with the neighbor beacons. This subset of nodes is also stored in a preferred list named PL. Now when a RouteRequest message is send out, only the nodes listed in the PL forward the message. Also neighbor's neighbor table (NNT) is used to maintain information of the neighbors and their neighbors. PLBR consists of 3 phases: Route Establishment, Route Selection and Route Maintenance.

In PLBR two different algorithms were proposed by Sisodia:

• Neighbor Degree-Based Preferred Link Algorithm (NDPL)
  This algorithm selects the path with the degree of a node which means the number of nodes. Nodes with a higher degree are preferred to node with a lower degree. All the nodes that have a higher degree have more nodes listed in their NNT and so fewer nodes can be selected.
• Weight-Based Preferred Link Algorithm (WBPL)
  Each node has its own weight. This weight is used to find stable links thought the network. WBPL considers the stability of the link between the nodes.

Example

In this example node 3 is the source (initiator) and node 8 is the destination (target). The source node 3 doesn't have the destination node in the NNT. Now NDPL is able to store the node that is usable to find the path in a preferred list table (PLT). In our case node 3 only sends the RouteRequest message to node 5. In WBPL the nodes 1, 2 and 4 are deleted from PLT because they are overlapping neighbors.
The RouteRequest packet is a unicast packet to avoid the flooding process. The destination node is present in the NNT of node 5 and can now be sent from here immediately to its destination.

Advantages

The main objective of PLBR is to find a route with an efficient flooding mechanism. Only a few numbers of packets are used for the path finding process.

Disadvantages

NDPL & WBPL are both computationally more complex than other RouteRequest forwarding schemes.

Reference

[Sisodia2002] Original paper and picture
[Sisodia2003]
[Murthy2004]

"Preferred Link-Based Routing Protocol" is mentioned on: Ad-Hoc Protocols (History) | Ad-Hoc Workshop Winter 04/05 (Termine) | Neighbor Degree-Based Preferred Link Algorithm | Weight-Based Preferred Link Algorithm