In this dissertation, several control problems are studied that arise when passive or dissipative systems are interconnected and controlled over a communication network. Since communication networks can impact the systems' stability and performance, there is a need to extend the results on control of passive or dissipative systems to networked configurations. We focus on addressing three problems in this thesis: the first problem is how to characterize the system's passive or dissipative properties quantitatively; the second problem is how to preserve the passive or dissipative properties of the interconnected systems over the communication network; the third problem is how to reduce the communication rates between the interconnected systems while stability and certain control objectives can still be achieved. The problems studied in this thesis consider complex but common situations in networked control systems and their solutions represent a practical benefit to the way we design and analyze the studied control systems. [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://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]