Tools and methods for evaluation of overlay networks

Overlay networks is a popular method to deploy new functionality which does not currently exist in the Internet. Such networks often use the peer-to-peer principle where users are both servers as well as clients at the same time. We evaluate how overlay networks performs in a mix of strong and weak peers. The overlay system of study in this thesis is Bamboo, which is based on a distributed hash table (DHT). For the performance evaluation we use both simulations in NS-2 and emulations in the testbed PlanetLab. One of our contributions is an NS-2 implementation of the Bamboo DHT. To simulate nodes joining and leaving, NS-2 is modified to be aware of the identity of overlay nodes. To control experiments on PlanetLab we designed Vendetta. Vendetta is both a tool to visualize network events and a tool to control the individual peer-to-peer nodes on the physical machines. PlanetLab does not support bandwidth limitations which is needed to emulate weak nodes. Therefore we designed a lightweight connectivity tool called Dtour. Both the NS-2 and PlanetLab experiments indicate that a system like Bamboo can handle as much as 50% weak nodes and still serve requests. Although, the lookup latency and the number of successful lookups suffer with the increased network dynamics