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Efficient Detection and Utilization of Asymmetric Links in Scalable Source Routing (SSR)

Efficient Detection and Utilization of Asymmetric Links in Scalable Source Routing (SSR)
Subject:Peer-to-peer Computing
Type:Diploma Thesis

Prof. Dr. Frank Bellosa, Pengfei Di, Dr. Thomas Fuhrmann

Graduand:Pascal Birnstill


As several empirical studies pointed out that asymmetric links occur considerably frequently in wireless networks and that network layer routing performance could potentially be significantly improved by utilizing these asymmetric links, it seems to be a reasonable feature within the Scalable Source Routing (SSR) protocol to provide support for asymmetric links.

The proposed algorithm is based on the approach of exchanging partial topology information as an extension of regular HELLO messages. Considering the network topology as a directed graph, two given nodes will only be able to communicate with each other if the network graph provides a directed cycle containing both of them. Therefore the main idea of this thesis is to find such a directed cycle, which we denote as a loop path.

Detecting a loop path containing an asymmetric link implies that a reverse path to this asymmetric link is obtained, i.e. a (multihop) source route connecting both nodes that are adjacent to the asymmetric link in the reverse direction of this asymmetric link. By this means, upon initially assuming any link to be asymmetric, source routes resolving occurring asymmetric links are gradually discovered.

Since exchanging exhaustive topology information does not scale with regard to bandwidth consumption and local storage requirements, we deployed some strategies on prioritizing and selecting appropriate topology information to be sent within periodic HELLO messages.


  author = {Pascal Birnstill},
  title = {Efficient Detection and Utilization of Asymmetric Links in Scalable Source Routing (SSR)},
  type = {Diploma Thesis},
  address = {System Architecture Group, University of Karlsruhe, Germany},
  month = may # "~19",
  year = 2009,
  url = {http://i30www.ira.uka.de/teaching/theses/pasttheses/}