In this section we'll try to answer the question of how much link bandwidth, router memory and router CPU cycles does the BGP protocol consume under normal conditions. We'll also address the scalability of BGP, and look at some of its limits.
BGP does not require all the routers within an autonomous system to participate in the BGP protocol. Only the border routers that provide connectivity between the local autonomous system and its adjacent autonomous systems participate in BGP. Constraining the set of participants is just one way of addressing the scaling issue.