Performance analysis of computer networks employing linked-cluster topology with single-wavelength and WDM optical backbones

Abstract

The present work deals with the analysis of linked-cluster networks with single-wavelength and wavelength-division multiplexed (WDM) optical backbones, providing interconnection between several clusters, wherein each cluster represents a local area network (LAN) with coaxial (coax) cable as the transmission medium. The proposed topology employs 1-persistant CSMA/CD-based media access control (MAC) protocol for coax LANs, and slotted-ALOHA as MAC protocol for single-wavelength optical backbone. In the case of WDM optical backbone slotted-ALOHA and ALOHA are considered as MAC protocols for control and data channels respectively. A novel iterative analytical technique is presented to evaluate the throughputs of individual coax LANs and optical backbone, as well as the end-to-end throughput of entire network. The analysis takes into account the impact of the relevant network parameters, viz. probability of intercluster communication, number of coax LANs, and the coax LAN parameters governing CSMA/CD protocol. The iterative evaluation of throughput is carried out to take into account the effect of the excess traffic in each coax LAN resulting from the intercluster communication. The analysis reveals that the probability of intercluster communications has significant impact on the backbone throughput as well as on the end-to-end throughput of the entire network. For a given coax LAN load, the end-to-end network throughput is found to decrease significantly when the probabilities of intercluster communication in coax LANs exceeds 50%. Further, the analysis shows that one can achieve considerable improvement in backbone throughput when WDM is employed in optical backbone instead of single-wavelength transmission.