"I knew how to create a ppp connect for gsm modem"

Is that just a typo, or have you forgotten?

"I don't understand how to implement tcp/ip protocol"

TCP/IP is independent of whether you're talking over PPP, SLIP, Ethernet, or whatever.

Go up to the top left corner of this page; there is a box marked 'Search'
Type "TCP/IP" into it, then press the grey button labelled 'Search!'
That will give you a wealth of info & links for implementing TCP/IP

If you also look a bit further down the sidebar, you will see that there's a TCP/IP link under 'Projects Online'

"(e,g http, ftp, sql, etc)"

HTTP (HyperText Transfer Protocol) and FTP (File Transfer Protocol) both use TCP/IP, but they are quite distinct from TCP/IP; if you want these protocols, you will have to implement them in addition to the TCP/IP stack.

SQL (Structured Query Language) has nothing whatsoever to do with TCP/IP!

Are you sure that you are equipped to implement your own TCP/IP stack? It is a non-trivial excercise!

TCP/IP will consume a considerable amount of the 8051's resources - athough it certainly can be done, you should carefully consider whether you really want/need to do it, and whether the 8051 is the best target for you!