how can we refresh the internet connection?

[Answers R Us]

Your talking about dropping your IP address and getting a new one, each IP address has a lease time with it.
If you get to command prompt and type IPCONFIG /RELEASE it will release your IP.
If your connected via a router then you need to log into your router and locate the command section in there that will do the same command.
You would then issue an IPCONFIG /RENEW command to generate a new IP.

To be fair I dont see why you would need to do this unless you have been doing things and are worried someone might try and track you, they will anyway - when you connect to the Internet your lease records your unique Mac address and this will be totally traceable to your unique network connection.