GPSR uses greedy forwarding to forward packets to nodes that are always progressively closer to the destination. In regions of the network where such a greedy path does not exist (i.e., the only path requires that one move temporarily farther away from the destination), GPSR recovers by forwarding in perimeter mode, in which a packet traverses successively closer faces of a planar subgraph of the full radio network connectivity graph, until reaching a node closer to the destination, where greedy forwarding resumes.
- Face routing, similar to greedy forwarding, is also stateless and nodes need to keep only information about their direct neighbors in order to forward a packet, thus combined geographic protocols of greedy and face routing are stateless.
- Greedy forwarding coupled with face routing is the common effcient approach of the currently proposed geographic protocol