OSI Model

http://home.earthlink.net/~tt4titans/id13.html
http://www.cse.iitk.ac.in/users/dheeraj/cs425/lec01.html
http://www.roseindia.net/technology/networking/osi.shtml

How to turn on Telnet client on your machine?

Here are the steps by which you can turn on the telnet client:
Goto Control panel ->     Programs and features ->      Turn Windows feature ON or OFF ->                                            Check Telnet Client ->     OK

HTTP Protocol

Nice tutorial on HTTP protocol:

Read here..