Gateway

gateway is a special router which is able to interpret inter/intra AS protocols at same time. It's a node that connects different AS.

Intra-AS Routing

• RIP:Routing infimation protocol :distance vector protocol
• OSPF:open shortest path first :link state protocol

inter-AS router

BGP:border gateway protocol

• iBGP:internal BGP
• eBGP:external BGP

Difference

• inter-AS can foucs on performance
• intra-AS may consider policies,politicals etc.