B.A.T.M.A.N.

B.A.T.M.A.N. ( Abbreviation for Better Approach To Mobile Adhoc Networking) is a routing protocol that is currently being developed by the free radio community.

Problem and solution approach

Classical routing protocols are only suitable for mobile ad -hoc networks, since these are unstructured, spontaneous growing or shrinking and inherently unreliable. The most promising approach so far, OLSR, had to be significantly modified from its original design before the protocol was to meet the challenges citywide Meshnetze. Some of its core components were found to be impractical, such as hysteresis or Multipoint Relay, or they limit the mesh net to a maximum size, eg, by sending to large amounts of data and the constant by computing the entire network topology. Despite these adjustments quickly revealed the limitations of OLSR, due to the continued growth of the free radio networks. The developers decided to learn from previous ideas and experiences with OLSR and implement these findings in a separate protocol.

The central idea in B.A.T.M.A.N. is to spread the knowledge of the best routes between all BATMAN node to the whole network. This eliminates the need to inform all Batman node of any changes in the mesh net. The individual nodes remember only the direction from which they have received data from their communication partners, and send their data back accordingly. On the way to the destination, the data is passed in this way from neighbor to neighbor. Scientifically speaking, this approach is similar to the pathfinding of ants using pheromones. Thus, a network of collective intelligence.

Operation

Batman's primary role is that of a classical routing protocol: It tracks other BATMAN nodes and determines the best path ( route ) to that node. In addition, it informs its neighbors about this new node and the way there. In static networks define network administrators or technicians which computer on which cable or which way ( eg radio ) is achievable. Since the signal strength in wireless networks but are highly volatile and low barriers to entry are a key requirement for open wireless networks, this task must be automated as far as possible:

Each node periodically informs all its neighbors, by means of a so-called broadcasts ( general message to all ) of its existence. This in turn repeat his existence message, which experienced the neighbors of the neighbors of this node. Thus, the information about each node in the whole network is distributed. In order to find the best way to all other neighbors, BATMAN counts each received Orginatornachricht in and remembers that this neighbor has sent him. In contrast to previous approaches, the protocol does not attempt to establish the full path to every other node, but uses the collected Orginatornachrichten to determine the first step in the right direction. The data is passed to the best neighbor for this direction which then applies the same principle. This process is repeated until the data has arrived at the recipient.

B.A.T.M.A.N. is generically designed so that it is not only in the field of wireless networks application, but also through traditional cable connections (such as Ethernet, Token Ring) can be used.

History

There should be a protocol be developed, which is simple, small and fast as possible. It seemed logical, therefore, that the development should take place in several stages, with more complex functions held only gradually appear:

Version 1

Initially, only the routing algorithm was implemented and tested for practicality. For the receiving and sending of Originatornachrichten ( existence of information ) of the UDP port was elected in 1966.

Version 2

The previous algorithm makes an implicit assumption: When a node receives data existence of another node, it assumes that it can send back data as well. In radio networks, but can be frequently observed that the communication is working in one direction only. To take this into account, the protocol was extended by a mechanism which the detection of bidirectional neighbors ( the communication works in both directions) allows. With version 2, only neighbors are taken into account, with which bidirectional communication is successful.

Version 3

The biggest innovation is the support of multiple network interfaces. Now you can B.A.T.M.A.N. to a central point ( the church tower, high roof, etc.), which is connected to multiple antennas or cables, do it's job. Also, some special cases have been considered in finding the way through the network, so that no circular routes (where the data never reach their destination ) can occur. Each node can now publish it in the network that it provides access to the Internet. Other users are thus able to recognize that there is an internet access in their area and how much bandwidth is available. You can opt for a special gateway or BATMAN ( based on criteria such as fast internet access ) leave the decision. There is also the possibility to announce devices in a BATMAN network, even if they no BATMAN Insert. Usually, home networks are involved in Meshnetzwerke in this way. There is an antenna installed on the roof, which via BATMAN communicates with the rest of the network, the rest of the building is only announced and thus accessible.