Routing protocol used to connect to an independent system on the Internet

The Border Gateway Protocol, also known as BGP, is mainly used to connect to the routing protocol of independent systems on the Internet, it is an enhanced, comprehensive, and scalable protocol developed by the Internet Engineering Task Group.

1. routes include two basic actions: determining the optimal path and transmitting information groups (usually called groups) over the network. The Network Transmission Group is relatively simple, and the path determination is complex. BGP is a protocol for Path Selection in today's networks. The following describes the basic operations of BGP and describes its Protocol components.

2. BGP implements Inter-Domain Routing in TCP/IP networks. BGP is an external Gateway Protocol (EGP) that performs routing between multiple autonomous systems or domains, and exchanges routing and accessibility information with other BGP systems, BGP is designed to replace its predecessor (no longer used) External Gateway Protocol (EGP) as the standard external Gateway Routing Protocol for the global Internet.

BGP solves serious problems of EGP and can better adapt to the rapid development of the Internet. BGP stipulates in multiple RFC that RFC1771 describes BGP4, the current version of BGP. RFC1654-describes the first BGP4 specification. RFC1105, RFC1163, and RFC1267-Describe the BGP version before BGP4.

3. routes between AS instances occur between two or more BGP routers of different AS instances. Peer routers of these systems use BGP to maintain a consistent network topology view, the BGP peers for AS communication must be in the same physical network.

The Internet is an instance that uses this route, because it consists of multiple AS (or management domain), many of which constitute the Internet's research institutions, companies, and entities. BGP is often used for routing selection to provide the optimal path for the Internet.

4. AS internal routes occur between two or more BGP routers in the same AS. Peer routers in the same AS use BGP to maintain a consistent system topology view. BGP is also used to determine which router acts AS the external AS connection point.

I reiterate that the Internet provides AS-based routing instances. An organization, such AS a university, can use BGP to provide optimal routing in its own management domain (or. The BGP protocol can provide both AS and AS internal routes.

5. pass-through (bgp) AS routing occurs between two or more BGP peer routers that exchange data through the AS without running BGP. In the AS environment, BGP communication does not come from nodes in the AS and the target nodes are not in the, BGP must interact with the routing protocol used in the AS to successfully transmit BGP communication through the AS, AS shown in the AS environment:

6. Like other routing protocols, BGP maintains the route table, sends route update information, and determines the route based on the routing metric. The main function of the BGP system is to exchange network accessibility information of other BGP systems, including the list of AS paths. This information can be used to establish an AS system connection diagram to eliminate routing loops, and execute the AS policy to determine, each BGP router maintains a route table consisting of all available paths to a specific network, but it does not clear the route table, it maintains the route information received from the peer router until it receives value-added (incremental) updates.

VII. BGP devices exchange route information after initial data exchange and value-added updates. When the router is connected to the network for the first time, the BGP router switches their entire BGP Route table. Similarly, when the route table changes, the router sends the changed part in the route table.

BGP routers do not send route updates cyclically, and BGP Route updates only include the optimal path to a network. BGP uses a single route metric to determine the optimal path to a given network. This metric contains any unit value that specifies the link priority. The BGP metric is usually assigned to each link by the network administrator. The value assigned to a link can be based on any number of scales, including the number of AS passing through, stability, speed, latency, or cost.

Although the BGP protocol is designed for routing between autonomous systems, it can also be used inside autonomous systems and is a type of Dual Routing Protocol. Two BGP adjacent nodes that can communicate between autonomous systems must exist on the same physical link.

BGP routers in the same autonomous system can communicate with each other to ensure that they share the same information for the entire autonomous system. After information exchange, they will determine which BGP router in the autonomous system is used as the connection point to receive information from outside the autonomous system.