Please find the following links related to some of the popular books on networking.

1. Data communications and Networking - Behrouz Forouzan

http://kat.ph/data-communications-and-networking-behrouz-a-forouzan-pdf-t6531499.html

2. Unix Network Programming - Richard Stevens

http://kat.ph/unix-network-programming-volume-1-2nd-edition-richard-stevens-pdf-t6166399.html

3. TCP/IP Protocol Suite - Forouzan

http://kat.ph/tcp-ip-protocol-suite-4th-edition-bbs-t5884951.html