Decentralized Modular Router Architectures

Abstract: The Internet grows extremely fast in terms of number of users and traffic volume, as well as in the number of services that must be supported. This development results in new requirements on routers—the main building blocks of the Internet. Existing router designs suffer from architectural limitations that make it difficult to meet future requirements, and the purpose of this thesis is to explore new ways of building routers.We take the approach to investigate distributed and modular router designs, where routers are composed of multiple modules that can be mapped onto different processing elements. The modules communicate through open well-defined interfaces over an internal network. Our overall hypothesis is that such a combination of modularization and decentralization is a promising way to improve scalability, flexibility, and robustness of Internet routers—properties that will be critical for new generations of routers.Our research methodology is based on design, implementation, and experimental verification. The design work has two main results: an overall system design and a distributed router control plane. The system design consists of interfaces, protocols, and internal mechanisms for physically separation of different components of a router. The distributed control plane is a decomposition of control software into independent modules mapped onto multiple distributed processing elements. Our design is evaluated and verified through the implementation of a prototype system.The experimental part of the work deals with two key issues. First, transport mechanisms for communication of internal control information between processing elements are evaluated. In particular, we investigate the use of reliable multicast protocols in this context. Results regarding communication overhead as well as overall performance of routing table dissemination and installation are presented. The results show that even though there are certain costs associated with using reliable multicast, there are large performance gains to be made when the number of processing elements increases. Second, we present performance results of processing routing information in a distributed control plane. These results show that the processing time can be significantly reduced by distributing the workload over multiple processing elements. This indicates that considerable performance improvements can be made through the use of the distributed control plane architecture proposed in this thesis.