I highly suggest reading at least one book on Computer Networking and my recommendation is for An Engineering Approach to Computer Networking: ATM Networks, the

I highly suggest reading at least one book on Computer Networking and my recommendation is for An Engineering Approach to Computer Networking: ATM Networks, the Internet, and the Telephone Network. You get a detailed overview of all the important network technologies. Next for TCP/IP; i suggest The TCP/IP Guide: A Comprehensive, Illustrated Internet Protocols Reference followed by the Stevens' books already mentioned by others. Finally to understand the interaction between HTTP application protocol and the underlying TCP/IP suite i suggest Web Protocols and Practice: Http/1.1, Networking Protocols, Caching, and Traffic Measurement. Only after you have some idea of the above should you look at the Linux specific implementation for which Understanding Linux Network Internals: Guided Tour to Networking on Linux is a good reference.