Transparent (cut-through) bridging of CSMA/CD networks: performance analysis and implementation

The increasing popularity of local area networks (LANs) and the limitations of a single LAN (on its geographical coverage, information-carrying capacity, and number of stations) have triggered tremendous interest in the study and implementation of interconnected LANs. The authors address the problem of interconnecting the widely deployed CSMA/CD LANs (or LAN segments) via a transparent bridge. A transparent bridge is so called because it “learns” about the network structure and organization during its operation, i.e., it learns about the location of the network stations relative to the bridge in order to do the forwarding of frames selectively; also, the stations need not be aware of the presence of the bridge. The authors make two important contributions. First, they present an approximate analytical model of a transparent CSMA/CD bridge which can be either of the normal store-and-forward type or of the novel cut-through variety (introduced by Kwok and Mukherjee). Using the analytical model, which is also verified via simulation, the performance of the cut-through bridge is compared with (and found to be superior than) that of the normal bridge. Secondly they present the design of a cut-through bridge which can be easily implemented using off-the-shelf components