Wireless Community Weekend Graz 07 (SOTF:HU1)

Metadata

Station:

Freies Radio Salzkammergut

Series:

Funkfeuer

Title:

Wireless Community Weekend Graz 07

Alternative title:

B.A.T.M.A.N. - better approach to mobile ad-hoc networking - Axel Neumann vom Entwicklerteam

Language:

German, English

Abstract:

Axel Neumann stellt die Idee und aktuellen Code zum B.A.T.M.A.N. routing protocoll vor. --- The problem with classical routing protocols is that they are typically not well suited for wireless ad-hoc networks. This is because such networks are unstructured, dynamically change their topology, and are based on an inherently unreliable medium. OLSR, the currently most employed protocol for such scenarios, has undergone a number of changes from its original specification in order to deal with the challenges imposed by city-wide wireless mesh networks. While some of its components proved to be unsuitable in practice (like MPR and Hysterese) new mechanisms have been added (like Fish-eye and ETX). However, due to the constant growth of existing community mesh networks and because of the inherent requirement of a link-state algorithm to recalculate the whole topology-graph (a particularly challenging task for the limited capabilities of embedded router HW), the limits of this algorithm have become a challenge. Recalculating the whole topology graph once in an actual mesh with 450 nodes takes several seconds on a small embedded CPU. The approach of the B.A.T.M.A.N algorithm is to divide the knowledge about the best end-to-end paths between nodes in the mesh to all participating nodes. Each node perceives and maintains only the information about the best next hop towards all other nodes. Thereby the need for a global knowledge about local topology changes becomes unnecessary. Additionally, an event-based but timelessfootnote{timeless in the sense that B.A.T.M.A.N never schedules nor timeouts topology information for optimising it's routing decisions} flooding mechanism prevents the accruement of contradicting topology information (the usual reason for the existence of routing loops) and limits the amount of topology messages flooding the mesh (thus avoiding overly overhead of control-traffic). The algorithm is designed to deal with networks that are based on unreliable links.

Keywords:

routing batman olsr freifunk funkfeuer mesh linux gpl

Topics:

Sciences and Technologies / Communications, telecommuncation and Internet

Production date:

2007-09-17

Entry date:

2007-09-17

Last modification:

2007-09-17

Contributors

Designer