Alternate routing protocols for bridged networks

Local area networks (LANs) are limited in size, geographically distance covered, and bandwidth. To extend a LAN, interconnecting devices called bridges are used to connect multiple LANs together to form extended LANs or bridged networks. In the IEEE 802.1D standard for bridges, a spanning tree is built among bridges for loop-free frame forwarding. Although this approach is simple, it does not support all-pair shortest paths. To provide quality-of-service (QoS) in LANs, the IEEE 802.1p standard specifies priority queuing in bridges. However, no existing bridge protocol supports path differentiation for frames of different priorities.; The work in this dissertation aims at enhancing the provision of QoS in bridged networks by introducing two alternate routing protocols. We design a novel bridge protocol that can forward frames on paths that are provably shorter than the paths that the standard provides. This protocol is called the Spanning Tree Alternate Routing (STAR) Bridge Protocol. STAR bridge protocol is backward compatible, which means that bridges in a bridged network can be incrementally upgraded instead of being replaced all at once. The complexity of the STAR protocol is comparable to existing mechanisms. To allow a system administrator to identify where to upgrade legacy bridges to be STAR bridges, we devise a placement strategy for STAR bridges. We formulate the performance gain and devise an algorithm that computes the locations for legacy bridges replacement that maximizes performance gain. To provide path differentiation in a bridged network, we devise a protocol called the Prioritized Enhanced Alternate Routing Load-balancing (PEARL) Protocol. The PEARL protocol can work with any bridge protocol that provides shorter path information to forward frames according to their priorities. We introduce a flexible and adjustable function for making forwarding decisions. We identify the properties of the function that are necessary to ensure frames of higher priority will never be forwarded on a path which is longer than a frame of lower priority will be forwarded on. As the function is simple, our PEARL protocol does not increase the computation, storage requirement, and storage overhead of the standard protocol.