In the first part of this dissertation, we study the competition among network service providers in a parallel-link network with the presence of elastic user demand that diminishes both with higher prices and congestion. First we analyze a game where providers strategically price their service for single class of traffic. Later we analyze a game where we consider two types of traffic differing in their sensitivity to delay, and service providers choose a rate to offer traffic of each type. We compare the situation in which a priority queue is provided by each provider for the delay sensitive traffic, to another situation in which each provider treats traffic of both types the same way. In these games, we measure the performance degradation of equilibrium relative to social optimum. Finally we study the value of service providers committing to offering a quantity of bandwidth to a market versus having the amount of bandwidth offered be conditional on the prices that the market settles upon. In Part II, we study strategic upgrade decisions of multiple interconnected agents in a network. The key feature is that an agent's revenue depends not only on its upgrade decision, but also on the upgrade decisions of others. We investigate the effect of lack of information about other agents incentives and the effect of the option to form coalitions. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]