Reliability and Performance of Multi-Level Loop Computer Networks

Single-loop networks tend to become unreliable and tardy when the number of nodes in the network becomes large. Fault tolerance and performance can be improved using double-loops. Because of different hop distances and cross-connections within one network highly reliable double-loop topologies are hardly extendable and adaptable to localities like buildings and floors. Another inconvenience is the modest performance improvement over single-loops. This paper presents an improved network architecture which incorporates high reliability, high performance and optimal accommodation to environmental topologies. The investigated network is tree-shaped where the leaves represent host computers or loop subnetworks and the vertices are ring adapters attaching hosts or bridges interconnecting subnetworks. For ease of modeling only balanced and homogeneous structures are considered where loop subnetworks have the same topology. Multi-level hierarchical loop networks have minimal diameter when the number of nodes in the subnetworks is proportional to the root of the number of all attached stations. In this case the diameter grows only with the logarithm of the number of stations. This implies that network reliability and performance are significantly improved using the proposed multi-level hierarchical architecture based on loop subnetworks. Our performance analysis assumes the protocol of buffer insertion.