I need some clarification on Proxy Server. When you configure internet browser like IE or Firefox to use Proxy server for communication (for all the protocols includng HTTP/FTP/GOPHER etc) does it uses the same port for all the communication? If so is it possible to restrict network access at the proxy server? Lets say I want some users to have only web access and some FTP. Is it possible with this kind of setup?
All traffic between the clients >> proxy server in on the proxy server port. Then the Proxy server 'sources'/proxies a 'new' connection having its IP as the source and the ultimate destination. Of course there are different types of proxy servers also anonymous, transparent etc. but this is the normal behavior. But almost all proxy servers allow you to control which use can access which protocols e.g. MS ISA. This can be done on the basis of username/IP/Machine etc.