Hybrids - ZRP

Figure: A ZRP scenario showing the zones of node A and node J using a r value of 2. Within the zones a pro-active routing protocol is used while a re-active protocol is used between zones.

Hybrid protocols seek to combine the proactive and reactive approaches. An example of such a protocol is the Zone Routing Protocol(ZRP)[39]. ZRP divides the topology into zones and seek to utilize different routing protocols within and between the zones based on the weaknesses and strengths of these protocols. ZRP is totally modular, meaning that any routing protocol can be used within and between zones. The size of the zones is defined by a parameter r describing the radius in hops. Figure 2.4 illustrates a ZRP scenario with r set to 1. Intra-zone routing is done by a proactive protocol since these protocols keep an up to date view of the zone topology, which results in no initial delay when communicating with nodes within the zone. Inter-zone routing is done by a reactive protocol. This eliminates the need for nodes to keep a proactive fresh state of the entire network.

ZRP defines a technique called the Bordercast Resolution Protocol (BRP) to control traffic between zones. If a node has no route to a destination provided by the proactive inter-zone routing, BRP is used to spread the reactive route request. Figure 2.5 illustrates the different components of ZRP.

Figure: The different components of the Zone Routing Protocol.