Gateway: A Abstractly, each router has a BGP routing table in the form of: \[(\text{prefix in another AS},\ \text{best ngh (next gateway hop) to reach prefix})\] First we will go over eBGP. We know BGP uses TCP to send messages and eBGP is no exception. The TCP connection exists between: each two gateways in the same AS, and each two ‘‘adjacent’’ gateways in different ASes. These gateway pairs sent \[(prefix,\ AS\text{-}path,\ next\text{-}hop)\] The BGP next-hop attribute is the next hop IP address that is going to be used to reach a certain destination.