The Ad Hoc On Demand Distance Vector (AODV) routing algorithm is a routing protocol designed for mobile ad hoc networks. AODV is capable of performing both unicast and multicast routing. It is an on-demand algorithm, meaning it creates paths between nodes only as desired by the source nodes. It maintains these paths as long as they are needed by the sources. Furthermore, AODV forms trees that connect members of the multicast group. Trees are composed of group members and the nodes needed to connect members. AODV uses sequence numbers to ensure the freshness of the paths. It is loop-free, starts automatically, and scales to a large number of mobile nodes. AODV creates routes using a route request/route response query cycle. When a source node wants a route to a destination to which it does not already have a route, it transmits a route request (RREQ) packet across the network. Nodes receiving this packet update their information for the source node and set back pointers to the source node in the routing tables. In addition to the source node's IP address, current sequence number, and broadcast ID, RREQ also contains the most recent sequence number for the destination that the source node is aware of. A node receiving the RREQ can send a route reply (RREP) if it is the destination or has a route to the destination with a matching sequence number greater than or equal to that contained in the RREQ. In this case, it unicasts a RREP to the origin. Otherwise it retransmits the RREQ. Nodes keep track of the source IP address and RREQ broadcast ID. If they receive an RREQ that they have already processed, they discard the RREQ and do not forward it. As the RREP propagates back to the source, the nodes set up... in the center of the paper... a tree for the life of the multicast group. Since network nodes are mobile, there are likely to be many link breaks along a route during the life of that route. The documents listed below describe how link breaks are handled. The WMCSA document describes AODV without multicast but includes detailed simulation results for networks of up to 1000 nodes. The Mobicom document describes the multicast operation of AODV and detailed simulations showing its correct operation. The Internet drafts include descriptions of both unicast and multicast path discovery, as well as mentioning how QoS and subnet aggregation can be used with AODV. Finally, the IEEE Personal Communications paper and the Infocom paper detail an in-depth study of simulations comparing AODV to the Dynamic Source Routing (DSR) protocol and examines the respective strengths and weaknesses of each protocol.