BGP4 Optimizations

BGP peers use a TCP connection to get connected. Afterwards, they exchange their full routing table only once, and from then on only send route update messages (with new/modified/deleted routes).

IP prefixes may be aggregated along the path. I.e. if a router sees that the paths towards several networks goes via the same router, and these networks belong to one less specific IP prefix, it may choose to advertise a single route for these networks, and mark the route as aggregated. This saves bandwidth, as well as decreases the routing tables sizes for remote routers.