What is Gateway-to-Gateway protocol?
GGP is a “min-hop” algorithm, i.e., its length measure is simply the number of network hops between gateway pairs. It implements a distributed shortest-path algorithm, which requires global convergence of the routing tables after a change in topology or connectivity. Each gateway sends a GGP routing update only to its neighbors, but each update includes an entry for every known network, where each entry contains the hop count from the gateway sending the update.