ben, will try my best to help.    what is your question?

We have lots of network plug on the wall in here.  If someone just plug in a network cabel with their laptop, then they can get on internet through the DHCP.

right..

Is there any way to have authenticate dhcp?  I mean are there any options to use a password to get dhcp credentials?

networking.. not really my area.. hehe.. but do you mean securing the dhcp so users must enter a password for DHCP to assign an IP?

Hmm...yes...that's my idea.  You plug in the network cable to wall....then start your browser, then it will ask your to enter password to get an DHCP's IP address.

I have never heard people doing that.  Normally they still assign an IP to the computer, but the computer will go through a proxy server to get out, and it is up to the proxy whether to authenticate?  That's my guess

cuz imagine this, once you plug in the cable, the operating system and the network adapter will try to establish the connection.  That's prior to launching the browser

hmm....you are right....so your guess is....if I want to setup something like this...then I should pin-point on the proxy setting?

yeah.  but I am sure there are other ways.. do you know if your company have a proxy server at all?