Data Communications and Networking
4th Edition 
Behrouz A. Forouzan
Mc Graw-Hill

Data Communications and Networking
7th Edition 
William Stallings
Prentice-Hall

Introduction to Data Communications and Networking
Wayne Tomasi
Prentice-Hall  

Computer Networking: A Top–Down Approach Featuring the Internet3rd Edition 
James F. Kurose, Keith W. Ross
Addison Wesley