The explosive growth of the Internet over the last decade has lead to a multitude of challenges brought forth by the scale of the system. The size of the global routing table has increased rapidly and several methods have been devised to ensure the routing scalability issue.
Inter-Domain Routing allows the exchange of data between peers along the best path. Each peer is an Autonomous System (AS) which connects a group of IP prefixes. The Border Gatweay Protocol (BGP) exchanges network reachability information with other BGP systems.
Routing information exchanged via BGP is based on reachability advertisements where each AS announces what it considers the best path and each domain define its own routing policy (costumer-provider peering or shared-cost peering). BGP Routing Information and BGP Forwarding Information are stored in BGP Routing Tables. The decission process consists on selecting the preferred routes or selecting the shortest AS path rules. Moreover, an AS can use two transit providers to connect to the Internet, wich is known as multihoming.
Limitations of current Internet (IP) architecture
Routers need to store information about all the destinations, which leads problems to manage the prefixes and to perform ingress traffic engineering. There are many prefixes and their count is growing too fast, which carries memory and CPU limitations. Moreover, currently simultaneous IPv4 and IPv6 address are used, which means that storing two routing tables worsens the prefix count growth.