Convergence issues in inter-domain routing and connectivity modeling of ad hoc networks

Abstract: This thesis addresses two topics in computer networking: inter-domain routing and modeling intermittently connected networks (ICNs). The standard inter-domain routing protocol used in the Internet today is the Border Gateway Protocol version 4 (BGP). BGP applies send-rate constraints to routing messages in order to limit its convergence complexity. We implement a simulator to study how the send-rate constraints affect BGP's convergence properties and compare the results with a theoretical convergence model. Routing policies are used to control BGP's path selection, which can give rise to routing divergence. We evaluate a path-history algorithm that can detect routing divergence, and show that the algorithm gives false positives under send-rate constraints. We use our simulator to show how likely it is that false positives occur in certain network configurations. Two solutions to solve this problem are proposed. Unlike the Internet, ICNs are networks in which connected end-to-end paths rarely exist. Device mobility, devices shutting down to conserve energy, and environmental constraints are common causes of intermittent connectivity. To develop routing algorithms for these networks, it is essential to first understand the patterns of connectivity between network devices. We propose a temporal connection model that captures connectivity patterns in ICNs. A tool for exploring topological and temporal properties of ICNs is developed and the connectivity behaviors of two real ICNs are analyzed.