BGP message types
BGP uses the following message types:
Open—After establishing a TCP connection, BGP sends an Open message to establish a session to the peer.
Update—BGP sends update messages to exchange routing information between peers. Each update message can advertise a group of feasible routes with identical attributes and multiple withdrawn routes.
Keepalive—BGP sends Keepalive messages between peers to maintain connectivity.
Route-refresh—BGP sends a Route-refresh message to request the routing information for a specific address family from a peer.
Notification—BGP sends a Notification message upon detecting an error and immediately closes the connection.