German DIY Community Releases New Mesh Routing Daemon  [Add to Bookmarks]
Dec 18, 2006 By Indrajit Basu
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Elektra- B.A.T.M.A.N's inventor.

The self-proclaimed largest do-it-yourself wireless community network, Freifunk in Germany, has developed a new algorithm that the developers claim would revolutionize adhoc networking or mobile mesh routing to make all current mesh routing protocols and algorithms obsolete.

Called B.A.T.M.A.N-III 0.1-rc1, this new software is a "much improved" version of B.A.T.M.A.N, an ad-hoc mesh-networking algorithm that first appeared as a trial version in March this year in Berlin.

"We have improved the algorithm and implemented B.A.T.M.A.N-III in the Freifunk community," said Juergen Neumann, the founder of Freifunk, whose developers developed this software, "and we are confident that the new algorithm works better than any other protocols we have seen so far."

"It is a revolutionary software" added Neumann, "which makes it possible to run ad-hoc routing protocol on almost any device no matter how little the CPU power is." This therefore, not only improves the efficiency of a self-organizing network, but it also dramatically reduces the cost of setting up a network by reducing the CPU and bandwidth costs.

First developed by a German software professional, Elektra, B.A.T.M.A.N. is an abbreviation for Better Approach To Mobile Adhoc Networking, a routing protocol enhancing connections in mesh networks. An ad-hoc network is a local area network or other small network, especially one with wireless or temporary plug-in connections, in which some of the network devices are part of the network only for the duration of a communications session or, in the case of mobile or portable devices, while in some close proximity to the rest of the network.

Mesh networking - a networking technique that allows peer network nodes to supply back haul services to other nodes in the same network - is a way to route data, voice and instructions between nodes. It allows for continuous connections and reconfiguration around broken or blocked paths by "hopping" from node to node until the destination is reached. Mesh networks are self-healing, which means that the network can still operate even when a node breaks down or a connection goes bad. This concept is applicable to wireless networks, wired networks, and software interaction.

Mesh networks differ from other networks in that the component parts can all connected to each other via multiple hops, and they generally are not mobile. Thus, it effectively extends a network by sharing access to higher cost network infrastructure.

"B.A.T.M.A.N-III has the power to replace the Optimized Link State Routing (OLSR) protocol that is currently being used in many wireless mesh networks around the world," says Neumann.

According to Neumann, OLSR developed by Andreas Tonnesen at UniK - University Graduate Center - and currently the most popularly used mesh networking protocol for wireless community projects around the world, suffers from a major flaw. It operates as a table driven, proactive protocol, i.e., exchanges topology information with other nodes of the network. Each node selects a set of its neighbor nodes as "multipoint relays" (MPR), and only those nodes selected as MPRs, are responsible for forwarding traffic intended into the entire network. "OLSR therefore has to continuously calculate different gateways from time to time, and each time the gateway changes, the connection breaks down," says Neumann. This is why it only makes sense in a small, all-wireless LAN or as a temporary fallback mechanism when a normally available infrastructure mode gear (access points or routers) stop functioning.

Whereas B.A.T.M.A.N-III uses the tunneling technology to connect to the gateways that ensures that the traffic does not slip while searching for nodes," say the developers. But this technology has other advantages as well. Since it connects to gateways via IP-tunnels, it enables gateway clients to select their gateways according to their speed and availability. Moreover, unlike OLSR (which considers different gateways from time to time), BATMAN-III remains with the selected gateway as long as it is available thereby ensuring far stable connections. "Consequently services like VOIP (internet telephony) and chat sessions become far more pleasurable," says Neumann.

According to him this new software, which builds routes much faster compared to OLSRD and responds to changes quicker as well all of which has a direct impact on reducing the cost of building a network, "is ideal for community wireless networks, which are typically, operate on tight budgets."

Freifunk claims that it has already implemented this software on part of its network "very successfully" and will eventually move over completely. Besides, Freifunk will also implement B.A.T.M.A.N-III in its firmware soon. The community provides it's own firmware for the Linksys WRT54GL Accesspoint and compatible models to turn them into meshing devices.

Why B.A.T.M.A.N is superior to OLSR.

- it doesn't calculate gigantic topology-graphs
- it doesn't need to synchronize topology information
- it doesn't populate routing tables with unreachable stations
- - routing loops are theoretically impossible
- - routing tables contain proactively all stations that are reachable, while reactive protocols don't - a single, central server collects topology information from al nodes for 2D or 3D topology visualization software.

Indrajit Basu is Digital Communities international correspondent.

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