OSI explained Book

This is a book to be welcomed with relief, providing a refreshingly clear sighted and amused approach to a subject....recommended both as an introduction to the standards themselves and as a basis from which to look at the direction they are taking. If you are looking for more detailed information about the OSI upper layers in a comprehensible form, this is the book for you. It covers the transport, session, and presentation layers in their entirety, and parts of the applications layer, notably FTAM and MOTIS. The style is highly readable and numerous explanatory figures are provided.