This is a Routing Protocol that uses a Hierarchical Routing Algorithm
- BGP is a path-vector protocol. (We’re not going into much detail about that.)
- The gateway routers send path-vector messages to advertise the reachability of networks.
- Each router that receives a path vector message must verify the advertised path according to its policy.
- If the message is compliant, the router modifies its routing table and the message before sending the message to the next neighbor.
- It modifies the routing table to maintain the autonomous systems that are traversed in order to reach the destination system.
- It modifies the message to add its AS number and to replace the next router entry with its identification.