1.7 Ethernet Network Performance

Just how fast can frames flow on an Ethernet network? While the preceding question might appear to be taken from a technically oriented game show, in actuality the answer to this question has a considerable bearing on the performance level of bridges and routers prior to those devices becoming possible network bottlenecks.

Chapter 7 focuses attention on the Carrier Sense Multiple Access with Collision Detection (CSMA/CD) network access protocol. By closely examining this protocol, we can determine the maximum frame rate that can be supported on a 10 Mbps, 100 Mbps, and even 1 Gbps Ethernet networks based upon different frame lengths. This, in turn , provides us with the ability to determine if the performance level of a bridge or router listed by a manufacturer is an appropriate decision criterion for equipment acquisition. That is, if the performance level of a device is greater than a certain frame forwarding rate, which represents the maximum frame rate that can be supported on an Ethernet network, the ability of a bridge, switch, or router to transfer frames beyond that rate is superfluous if the device only supports one communications circuit. Thus, the ability of one vendor's bridge or router to forward frames at a faster rate than another vendor's product may not be applicable to consider when evaluating competitive products.

Once the Ethernet frame rate is determined, Chapter 7 then presents an easy-to-use method to predict throughput between interconnected networks. This method permits you to estimate the best-case transfer time to upload or download files across connected networks, as well as to project the average time required to perform those activities.