[c-nsp] shutdown process on interfaces in cisco routers

[m s]

Hi 

In cisco routers when we shutdown an interface how other routers understand this?
My aim is that when tow routers are connected to each other and their interfaces are on the "protocol" parameter in "show ip interface brief" command is on and after one of interfaces be shutdown this parameter become off,I want to know that how this happen? Does any packets exchange? what packets? for example arp or cdp packets?
Thanks