GLS is a distributed location service that tracks mobile node locations and enables geographic ad hoc routing. It is decentralized and runs on mobile nodes, requiring no fixed infrastructure. Each mobile node periodically updates a small set of other nodes (its location servers) with its current location. A node sends its position updates to its location servers without knowing their actual identities, assisted by a predefined ordering of node identifiers and a predefined geographic hierarchy. Queries for a mobile node's location also use the predefined identifier ordering and spatial hierarchy to find a location server for that node. Experiments using the ns simulator for up to 600 mobile nodes show that the storage and bandwidth requirements of GLS grow slowly with the size of the network. Furthermore, GLS tolerates node failures well: each failure has only a limited effect and query performance degrades gracefully as nodes fail and restart. The query performance of GLS is also relatively insensitive to node speeds. Simple geographic forwarding combined with GLS compares favorably with Dynamic Source Routing (DSR): in larger networks (over 200 nodes) our approach delivers more packets, but consumes fewer network resources. GLS is based on the idea that a node maintains its current location in a number of location servers distributed throughout the network. These location servers are not specially designated; each node acts as a location server on behalf of some other nodes. The location servers for a node are relatively dense near the node but sparse farther from node; this ensures that anyone near a destination can use a nearby location server to find the destination, while also limiting the number of location servers for each node. On the other hand, long distance queries are not disproportionately penalized: query path lengths are proportional to data path lengths. GLS balances the location server work evenly across all the nodes if there is a random distribution of node IDs across the network. GLS ensures that nodes are allocated unique, random IDs by using a strong hash function to obtain an ID from a node's unique name. The name could be any uniquely allocated name, such as Internet host names, IP addresses, or MAC addresses. For purposes of discussing the GLS, a node's ID is more interesting than its original name, therefore when we refer to a node A, we are referring to the node whose name hashes to A. GLS provides for distributed location lookups by replicating the knowledge of a node's current location at a small subset of the network's nodes. This set of nodes is referred to as the node's location servers. A node A hoping to contact node B can query one of a number of other nodes that know B's location. Of course, A must be able to contact the nodes that know B's location. This means that A's search for B's location servers and B's original recruitment of location servers ought to lead to the same servers. When B recruits location servers it uses the same information that A will have when searching for B's location servers: B'sGLS is a distributed location service that tracks mobile node locations and enables geographic ad hoc routing. It is decentralized and runs on mobile nodes, requiring no fixed infrastructure. Each mobile node periodically updates a small set of other nodes (its location servers) with its current location. A node sends its position updates to its location servers without knowing their actual identities, assisted by a predefined ordering of node identifiers and a predefined geographic hierarchy. Queries for a mobile node's location also use the predefined identifier ordering and spatial hierarchy to find a location server for that node. Experiments using the ns simulator for up to 600 mobile nodes show that the storage and bandwidth requirements of GLS grow slowly with the size of the network. Furthermore, GLS tolerates node failures well: each failure has only a limited effect and query performance degrades gracefully as nodes fail and restart. The query performance of GLS is also relatively insensitive to node speeds. Simple geographic forwarding combined with GLS compares favorably with Dynamic Source Routing (DSR): in larger networks (over 200 nodes) our approach delivers more packets, but consumes fewer network resources. GLS is based on the idea that a node maintains its current location in a number of location servers distributed throughout the network. These location servers are not specially designated; each node acts as a location server on behalf of some other nodes. The location servers for a node are relatively dense near the node but sparse farther from node; this ensures that anyone near a destination can use a nearby location server to find the destination, while also limiting the number of location servers for each node. On the other hand, long distance queries are not disproportionately penalized: query path lengths are proportional to data path lengths. GLS balances the location server work evenly across all the nodes if there is a random distribution of node IDs across the network. GLS ensures that nodes are allocated unique, random IDs by using a strong hash function to obtain an ID from a node's unique name. The name could be any uniquely allocated name, such as Internet host names, IP addresses, or MAC addresses. For purposes of discussing the GLS, a node's ID is more interesting than its original name, therefore when we refer to a node A, we are referring to the node whose name hashes to A. GLS provides for distributed location lookups by replicating the knowledge of a node's current location at a small subset of the network's nodes. This set of nodes is referred to as the node's location servers. A node A hoping to contact node B can query one of a number of other nodes that know B's location. Of course, A must be able to contact the nodes that know B's location. This means that A's search for B's location servers and B's original recruitment of location servers ought to lead to the same servers. When B recruits location servers it uses the same information that A will have when searching for B's location servers: B's