DT-Chord: implementing chord over delay tolerant network

Abstract

Delay Tolerant Networks (DTNs) are a class of networks designed to address several challenging connectivity issues such as sparse connectivity, long or variable delay, intermittent connectivity, asymmetric data rate, high latency, high error rates and even no end-to-end connectivity. The DTN architecture adopts a store-and-forward paradigm and a common bundle layer located on the top of region-specific network protocols in order to provide interoperability of heterogeneous networks (regions). In this type of network, a source node originates a message (bundle) that is forwarded to an intermediate node (fixed or mobile) thought to be more close to the destination node. The intermediate node stores the message and carries it while a contact is not available. Then the process is repeated, so the message will be relayed hop by hop until reaching its destination. A fundamental problem that confronts future applications of DTN is how to efficiently locate the DTN node that stores a particular data item. In this case, flooding search seems to be the only method. However, this usually results in so-called broadcast storm problem, which leads to significant performance degradation in DTN. Distributed hash table (DHT) based protocols provide near-optimum data lookup time for resolving queries made on large P2P network. Lookup latency is important to applications that use DHTs to locate data. In order to achieve low latency lookups, each node needs to consume bandwidth to keep its routing tables up to date under churn. This thesis presents DT-Chord- a DHT based application protocol for Delay Tolerant Network that minimizes delay while locating data in DTN. This thesis also shows performance comparisons between base Chord and DT-Chord protocols over Delay Tolerant Network. Finally, we provide a methodology to determine the relative importance of tuning application protocol parameters under different workloads and network conditions.