Mobile routing protocol advances

PHILADELPHIA'A network may be difficult to maintain if its routers come and go at random intervals. Most IP routing techniques rely on relatively static router configurations, a stability not likely to be encountered by mobile devices being used in combat or other highly dynamic scenarios. To this end, Naval Research Laboratory researchers are helping develop a set of routing protocols for setting up mobile ad-hoc networks (MANETs).

This week, the Internet Engineering Task Force's MANET working group has posted three Internet Drafts, as well as published a new request for comments this week, all of which advance standards work in the area. The group met this week at IETF's 71st meeting, held in Philadelphia.

NRL researcher Joseph Macker, who started work on MANET almost two decades ago, co-chairs group, which includes engineers from Motorola, Juniper, Cisco, Johns Hopkins University's Applied Physics Laboratory and other research institutions.

According to the Working Group charter, the MANET protocols will be used for lightweight mobile devices involved in mesh, wireless or other networks with dynamic topologies. It is tailored for devices with limited memory and computational power. It assumes that nodes will drop in and out of the network in a varying state.

According to Macker, the MANET architecture involves building a routing table in which each node not only knows its neighbors one hop away, but the nodes next to these neighbors as well. Together, all the nodes can work together to generate routing tables that can efficiently send packets through the topology.

A MANET network can work in reactive mode, in which the route is not determined until the network must convey a packet, or in proactive mode, in which the nodes confer with each other to build routing tables regardless of traffic. Proactive networks can convey traffic more quickly, though involve more processing and bandwidth overhead.

Of the three new Internet Drafts, one is on a neighborhood discovery protocol that allows nodes to discover and work with nodes one and two hops away. A second one is about how to build a packet format capable of carrying multiple messages. A third one, about the Management Information Base, describes a set of tools for configuring and managing routers on a mobile network.

In addition, IETF approved "Jitter Considerations in Mobile ad-Hoc Networks" as a Request for Comment (RFC 5148). This work suggests ways to randomly vary packet transmission times in order to avoid packet collision. Internet Drafts are submitted to IETF for consideration as standards. Once approved, they become RFCs.

Researchers at the Working Group meeting also unveiled some MANET test cases and prototype implementations. NRL has developed a C++ library that will allow developers to package and unbundle MANET packets. The library works with standard networking interfaces such as sockets, timers and routing tables.

In addition, other researchers described implementations of MANET's Optimized Link State Routing, a protocol for building link tables for ad-hoc networks, including those built at France's Laboratoire d'Informatique de l'Ecole Polytechnique and Japan's Niigata University.

About the Author

Joab Jackson is the senior technology editor for Government Computer News.

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