John Davidson 
Introduction to TCP/IP [PDF ebook] 

TCP/IP is currently the most important emerging protocol suite in the computer networking field. The need for connecting computers and other electronic devices together will grow exponentially, in industry as well as in academic and research environments. An introduction to TCP/IP describes the protocol suite according to the International Organization for Standards'(ISO) seven-level (OSI) reference model. It is a unique and valuable source of information for everybody interested or involved in local or wide-area computer networking projects. It is written by Dr. John Davidson at Ungermann/Bass, the world’s largest manufacturer of local area networks.