why BGP protocol have more scalability then other routing protocol? what BGP have that makes it more scalable then other routing protocols?

Question

what BGP have that makes it more scalable then other routing protocols

Answer 1

BGP works on the principle of inter-domain routing whereas the other protocols like RIP(Routing Information Protocol) & OSPF(Open Shortest Path First) are supposed to work only in an intra-domain routing!

This benefits BGP to handle routing between several autonomous-systems over the Internet which implement path-vector routing to get its work done. A unique ASN is allocated to each AS for use in BGP routing. AS numbers are important because the ASN uniquely identifies each network on the Internet.

An autonomous system is like a master router which stores information of all the routers' routing-table and acts as the master-router in that intra-domain routing area. Several intra-domain routing areas combine to form a inter-domain routing area where BGP can be used to exchange routing and reachability information between autonomous systems (AS) on the Internet.

Answer 2

BGP was designed to deal with large size of network like the Internet. It can carry 200K-500K of prefixes without burdening a router with heavy calculation due to dynamic change of link states. In the Internet, link down or flapping could happen very often. Link state routing protocol (i.e. OSPF) is not suitable to handle this situation because it will try to always keep up with the change and update its routing table. It will eventually do nothing else but routing update. This is why policy-based routing like BGP is needed.