TCP/IP Guide

Theoretical and Real-World Throughput, and Factors Affecting Network Performance

When assessing the performance of networks, keep in mind that there is always a difference between theoretical speed ratings and real-world throughput. If your network is set up well, this difference is relatively small but still significant. Otherwise, the difference can be extremely large. (Notice that the difference between theoretical and practical performance can never be negligible.)

There are many reasons for the difference between what a network or communications method is supposed to be able to do and what it actually can do. The reasons generally fall into three categories: normal network overhead, external performance limiters, and network configuration ...