3. Reagent protocols

A reactive protocol does not compute topology information until it is required by an application's request to route a packet to a destination. The protocol only attempts to discover a route at the request of an application wishing to send a packet to a destination, by broadcasting a request throughout the network. The response to this broadcast request enables the source to obtain topological information about the route. During this route-finding phase, the IP packet is put on hold until a route is available.