IERP
The Interzone Routing Protocol short IERP is needed for some routing protocols like ZRP (Zone Routing Protocol or ZHLS (Zone Hierarchical Link State Protocol). IERP is a reactive routing protocol and takes only the advantages from reactiv routing. It is responsible for the communication between the different zones. Route queries within a zone, which means between different zones, are issued on demand. That is only when a request for a route is made. The delay caused by the route discovery is minimized through the use of bordercasting. (
Broadcast Resolution Protocol (BRP)) Bordercast Routing Protocol does not submit the query to all local nodes, but only to its peripheral nodes.
If a node S would like to send a packet to node D, he is going to ask his bordernodes if node D is in his zone.
If yes: the IARP (Intrazone Routing Protocol) starts
If no: The Bordernodes starts a Route Discovery. His Bordernodes send the packet with the route request to their bordernodes.The bordernodes append their IP-address along with metrics for the link on which the packet was received. Then they check in their routing table for a valid route to node Z. (Intrazone Routing Protocol IARP). They send the route request forward to other bordernodes, identified by the bordercast service (BRP), if the specific node Z isn't in their zone. But if the node knows a valid route to the destination node the route is appended to the route request accumulated route. The route request is copied to a route reply packet. This Packet is forwarded back to node S by IERP along the reverse accumulated route. But when a node IARP detects that a node has changed his position in its routing zone, the IERP is notified. For each IERP route, the node identifies an alternate route through its routing zone. That minimizes the distance to the destination and serves to bypass failed links.
References
[
Haas2001a] Original Internet Draft
[
Haas2002d]
