Backward Compatible Multi-Path Routing
Document typeMaster thesis
Rights accessOpen Access
This project studies the behaviour of multipath routing compared to single path routing in order to demonstrate the different benefits that multipath offers. For this purpose, it have been implemented routers that have 2 routing tables with the capability of storing in one these routing tables the primary next hop for a destination through the shortest path which is calculated by the Open Shortest Path First (OSPF) algorithm, as well as storing a secondary next hop calculated by the Ideal Multipath Routing Expedient (IMRE) algorithm in order to have different paths for the same destination. Besides matching on the destination address, the routers select between the primary and secondary tables based on the Time To Live (TTL) field of the IP header. The end-system can change the forwarding path immediately upon it senses the degradation of the current path by sending the packets with a different TTL value, without waiting for the slow convergence of OSPF to the changed topology. This multipath behaviour is measured for 3 different use cases. First use case measures the throughput and transmission time when transmitting a file in an ideal scenario where there are no other transmissions at the same time. Second use case performs the measurements for the same transmission as before but when there is a transmission that makes 2 links of the shortest path to be overloaded in order to check the load balancing capability of multipath routing. Finally, the third use case studies the behaviour of multipath routing when there is a failure in a link during the transmission and checks its failure resilience characteristic. Furthermore, I have studied the paths provided by the IMRE algorithm with a specific TTL match rule. I have demonstrated that in this architecture some TTLs might result in loops, hence, the set of available TTLs for the end-system has to be selected with care.