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BGP
What is BGP?
BGP is mainly used for the interconnection between the Internet AS (Autonomous System), BGP is the most important function is to control the spread of routes and choose the best route. China Unicom, China Telecom, China Railcom and some large private IDC operators all have AS numbers, and most major network operators across the country implement multi-line interconnection with their own AS numbers through the BGP protocol. To use this solution to realize multi-line interconnection, IDC needs to apply for its own IP address segment and AS number at CNNIC (China Internet Information Center) or APNIC (Asia-Pacific Network Information Center), and then broadcast this IP address to others through the BGP protocol In the network of the network operator. After using the BGP protocol to interconnect, all backbone routing equipment of the network operator will determine the best route to the IP segment of the IDC computer room to ensure high-speed access for users of different network operators.
BGP is divided into dynamic and static. At present, most of the market is static BGP. If it is dynamic, only Xiaoniao Cloud Computing has opened the South China BGP computer room and Hong Kong BGP computer room. The dynamic BGP line adopted perfectly solves the problem of cross-networking. The problem of high latency of visits and inter-connection between North and South. With the rapid development of the cloud computing industry, BGP lines will become standard in the public cloud computing industry.
What does BGP mean?
BGP is called Border Gateway Protocol, which is a routing protocol that manages routes between AS. It is also the only inter-AS routing protocol.
BGP cannot generate routes, mainly through some attributes and policies to control routing
Overview of BGP Principle The
BGP protocol is a distance vector routing protocol, but compared to typical distance vector protocols such as RIP, it has many enhanced performance. BGP uses TCP as the transport protocol and port number 179. During communication, a TCP session must be established first, so that the reliability of data transmission is guaranteed by the TCP protocol, and the error control and retransmission mechanism is no longer used in the BGP protocol, thus simplifying the degree of complexity. In addition, BGP uses incremental and triggered routing updates instead of periodic updates of the entire routing table of the general distance vector protocol, which saves the bandwidth occupied by the update. BGP also uses "Keepalive" signals to monitor the connection of TCP sessions. Moreover, BGP also has a variety of metrics for measuring routing paths (called routing attributes), which can more accurately determine the optimal path.
BGP uses TCP as its bearer protocol to establish connections. Therefore, unlike IGP hop-by-hop routers establishing neighbors, BGP can establish neighbor relationships across multi-hop routers.
BGP speakers and BGP
peers The routers running the BGP protocol are called BGP speakers. BGP speakers receive or generate routing information, and advertise the routing information
to other BGP speakers.
BGP speakers that have TCP connections between each other and exchange routing information are BGP peers. According to the
AS where the peer is located , the peers are divided into the following types:
1. IBGP peer: The peer and the local router are located in the same AS.
2. EBGP peer: The peer and the local router are located in different ASs.
BGP message types
BGP defines the following message types:
1. Open: The first message sent after a TCP connection is established, used to establish a session between BGP peers.
2. Update: used to exchange routing information between peers. An Update message can advertise multiple
reachable routes with the same path attributes , or cancel multiple unreachable routes at the same time.
3. Keepalive: BGP periodically sends Keepalive messages to peers to maintain the validity of the session.
4. Route-refresh: used to request the peer to resend the routing information of the specified address family.
5. Notification: When BGP detects an error state, it sends a Notification message to the peer, and then the BGP session
is immediately interrupted.
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