Explaining Structured Errors in Gigabit Ethernet
A physical layer coding scheme is designed to make optimal use of the available physical link, providing functionality to higher components in the network stack. This paper presents results of an exploration of the errors observed when an optical Gigabit Ethernet link is subject to attenuation. In the unexpected results, highlighted by some data payloads suffering from far higher probability of error than others, an analysis of the coding scheme combined with an analysis of the physical light path leads us to conclude that the cause is an interaction between the physical layer and the 8B/10B block coding scheme. We consider the physics of a common type of laser used in optical communications, and how the frequency characteristics of data may affect performance. A conjecture is made that there is a need to build converged systems, with the combinations of physical, data-link, and network layers optimised to interact correctly. In the mean time, what will become increasingly necessary is both an identification of the potential for failure and the need to plan around it. Topic