It's worth noting that the IEEE 802.3 standards are legally freely available, if you want to go for the definitive reference: http://ieeexplore.ieee.org/browse/

It's worth noting that the IEEE 802.3 standards are legally freely available, if you want to go for the definitive reference: http://ieeexplore.ieee.org/browse/standards/get-program/page/series?id=68 http://ieeexplore.ieee.org/browse/standards/get-program/page... Once you get over the copious standardese, and the fact that the standards describe some things that seem like a good idea yet have never been implemented (e.g. 100BASE-T2), they are a good source of very detailed and authoritative information.