I am learning active directory service For example, I have one windows server 2008 domain located in New York and one windows server 2008 located in Chicago. I want to know the way we connect the WAN link of my servers. We connect to the internet or we connect by using the personal cable that we rent from ISP?

you will actually have to create sites using Active directory sites and services and put each server in there own subnets you should start reading it from here http://technet.microsoft.com/en-us/library/cc732887(WS.10).aspx you should use your ISP to connected your both the sides using Leased lines, MPLS,T1 or vpn connections http://www.virmansec.com/blogs/skhairuddin

Hi ! Yes you will need to create sites using AD DS, must be in own subnets, also you must read some technet articles and book about this and my recommendation is to going to Microsoft course. Also you must use yours local ISP providers to be connected both sides over internet or VPN. This connection must be like T1 lines.

Hi I am not good at English. I have read again and a gain but i still don't understand so i finally post my wonders in the forum. Do you mean we can connect the severs that is assignted the private IP by using its own subnets over the internet.

Yes you are right you can use the Private IPs using there own subnets but over a national link which is T1. You dont have to worry about it ask your ISP that you need a T1 link which should connect the 2 offices with routing the traffic to internet.http://www.virmansec.com/blogs/skhairuddin