How restart network in terminal and change configuration networkin in file?

Hello...
I need help, and more instructions, please.
I change often my network configuration in my macbook, and I had a problem some time, I think in restart network also /etc/init.d/networking restart in Debian, but how I can do it in MacOSX, I try ifconfig restart, netstat restart.
Then how I can restart my network config?

One more question: How I change ip number, mask, gateway and DNS in file of confg? What file there this configuration number?
Thanks all

Sorry my english writer