Border Gateway Protocol, Border Gateway Protocol, referred to as BGP, mainly used for the interconnection between the Internet AS (Autonomous System).
Linux kernel natively supported, specifically used in large-scale data center maintenance route between different "autonomous systems" information, without a central routing protocol ..
For example:
AS1 and AS2 are independent autonomous systems, all of an organization to all IP networks and routers under its jurisdiction (imagine all hosts and routers into a small company)
if AS1, AS2 access to the 172.17.0.3 10.10.0.2 then, according to the routing rules, IP packet sent must Router1, sent to the port by C Router2 gateway (router on AS),
but conversely, if you want to access the host 172.17.0.3 10.10.0.2, after Router2 arrive, do not know where to go, because there is no corresponding routing rules, this time, the network administrator should also add a route to Router2 rule, such as IP packet 10.10.0.2, it should be through the C interface Router2, sent to Router1
Router2 such as routers Router1 and the various autonomous systems connected together, called: border gateway, its routing table has a host of other autonomous system routing information
if the network topology is very complex, it must rely on artificial border gateways to route table configure and maintain, unrealistic, so BGP came out.
After using BGP, the Border Gateway are each running a small program that will own routing table information, TCP data transmission through to the other border gateways, and other border gateways of this small program, you will receive analysis and then add the required information to their own routing table.
Therefore, BGP is to implement a protocol node routing information sharing in large-scale networks.