While the product set has changed dramatically since I first began testing internetworking gear in the 1980s, the goals of product designers seem to remain constant. From the earliest two-port bridges to the latest high-density Layer "X" switches, vendors largely follow an unwritten but consistent development course as products move through their life cycles.
Extrapolating from the hundreds of tests The Tolly Group has conducted over the years, I can identify at least three areas of "absolutes" that are targets for design engineers.
-- Wire-speed throughput
Whether relevant to an actual customer environment or not, wire speed has long been the most fundamental engineering imperative for designers of bridges, routers and switches. Thus, implementing functions in silicon and optimising software components are typically the first actions taken as a product begins its life cycle. As speeds increase - from 10M to 100M to 1000Mbits per second - the challenge to achieve wire-speed throughput is revisited.
-- Infinite capacity
Once wire-speed performance is commonplace, it is time to raise the bar. The question then becomes one of load or capacity. If two devices boast wire-speed throughput, one that supports this load for 50 simultaneous data streams is better than one that can do that for only 25 data streams.
Thus, we see test beds growing larger and larger. Where tests of a few dozen ports were commonplace just a few years ago, today it is not uncommon to test configurations involving over one hundred switch ports. The ideal product, of course, can handle an infinite load.
As with the engineering absolute of wire speed, the target of handling an infinite load typically serves engineering interests more than customer interests. Who designs, say, a 100-port switch to operate at full load on every port all the time?
-- Maximum function
Once the practical limits of raw power have been reached, vendors turn to function. Early products achieved wire speed with virtually every value-add component - even essential ones such as spanning tree - shut off. Realising that network managers need functions such as network management, high-density, wire-speed switch vendors have started to add back functionality. The critical aspect to note is that this added functionality does not degrade performance. Thus, you'll find testing that shows wire-speed performance both before and after resource-intensive functions such as RMON have been enabled.
Vendors need to do all of this and drive down the cost to build these devices until it is as close to zero as possible. Good value to the customer with good margins for the vendor makes everyone happy.