Editing Zone Routing Protocol (section)

==Details==
What is called the Intra-zone Routing Protocol (IARP), or a [[List of ad hoc routing protocols#Pro-active .28table-driven.29 routing|proactive routing protocol]], is used inside routing zones. What is called the Inter-zone Routing Protocol (IERP), or a [[List of ad hoc routing protocols#Reactive .28on-demand.29 routing|reactive routing protocol]], is used between routing zones. IARP uses a routing table. Since this table is already stored, this is considered a proactive protocol. IERP uses a reactive protocol.

Any route to a destination that is within the same local zone is quickly established from the source's proactively cached routing table by IARP. Therefore, if the source and destination of a packet are in the same zone, the packet can be delivered immediately.

Most existing proactive routing algorithms can be used as the IARP for ZRP.

In ZRP a zone is defined around each node, called the node's ''k-neighborhood'', which consists of all nodes within ''k'' hops of the node. ''Border nodes'' are nodes which are exactly ''k'' hops away from a source node.

For routes beyond the local zone, route discovery happens reactively. The source node sends a route request to the border nodes of its zone, containing its own address, the destination address and a unique sequence number.  Each border node checks its local zone for the destination. If the destination is not a member of this local zone, the border node adds its own address to the route request packet and forwards the packet to its own border nodes. If the destination is a member of the local zone, it sends a route reply on the reverse path back to the source. The source node uses the path saved in the route reply packet to send data packets to the destination.