BGP (Border Gateway Protocol) PDF

Border Gateway Protocol It is an interdomain routing protocol, and it uses the path-vector routing. It is a gateway protocol that is used to exchange routing information among the autonomous system on the internet. As we know that Border Gateway Protocol works on different autonomous systems, so we...

Border Gateway Protocol It is an interdomain routing protocol, and it uses the path-vector routing. It is a gateway protocol that is used to exchange routing information among the autonomous system on the internet. As we know that Border Gateway Protocol works on different autonomous systems, so we should know the history of BGP, types of autonomous systems, etc. History of BGP The first network was ARPANET, which the department of defense developed, and the Advanced Research Project Agency designed it. In Arpanet, only one network exists, which was handled by the single administrator. All the routers were the part of the single network, and the routing was performed with the help of the GGP (Gateway to Gateway Routing Protocol). The GGP was the first protocol among all the routing protocols. The autonomous system numbers were not used in the GGP protocol. When the internet came into the market, then GGP started creating the problem. As the internet backbone became large due to which the routing table was also large, which led to the maintenance issue. To resolve this issue, the ARPANET was divided into multiple domains, known as autonomous systems. Each autonomous system can be handled individually, and each system has its own routing policy, and the autonomous system contains the small routing database. When the autonomous system concept was implemented, then the first routing protocol came known as RIP that runs on the single autonomous system. To connect the one autonomous system with another autonomous system, EGP (Exterior Gateway Protocol) protocol was developed. The EGP protocol was launched in 1984, defined in RFC 904. The EGP protocol was used for five years, but it had certain flaws due to which the new protocol known as Border Gateway Protocol (BGP) was developed in 1989, defined in RFC 1105. PlayNext Unmute Current Time 3:07 / Duration 18:10 Loaded: 22.75%   Fullscreen Backward Skip 10sPlay VideoForward Skip 10s There are many versions of BGP, such as: o BGP version 1: This version was released in 1989 and is defined in RFC 1105. o BGP version 2: It was defined in RFC 1163. o BGP version 3: It was defined in RFC 1267. o BGP version 4: It is the current version of BGP defined in RFC 1771. BGP Autonomous Systems An autonomous system is a collection of networks that comes under the single common administrative domain. Or we can say that it is a collection of routers under the single administrative domain. For example, an organization can contain multiple routers having different locations, but the single autonomous number system will recognize them. Within the same autonomous system or same organization, we generally use IGP (Interior Gateway Protocol) protocols like RIP, IGRP, EIGRP, OSPF. Suppose we want to communicate between two autonomous systems. In that case, we use EGP (Exterior Gateway Protocols). The protocol that is running on the internet or used to communicate between two different autonomous number systems is known as BGP (Border Gateway Protocol). The BGP is the only protocol that is running on the internet backbone or used to exchange the routes between two different autonomous number systems. Internet service providers use the BGP protocol to control all the routing information. BGP Features The following are the features of a BGP protocol: o Open standard It is a standard protocol which can run on any window device. o Exterior Gateway Protocol It is an exterior gateway protocol that is used to exchange the routing information between two or more autonomous system numbers. o InterAS-domain routing It is specially designed for inter-domain routing, where interAS-domain routing means exchanging the routing information between two or more autonomous number system. o Supports internet It is the only protocol that operates on the internet backbone. o Classless It is a classless protocol. o Incremental and trigger updates Like IGP, BGP also supports incremental and trigger updates. o Path vector protocol The BGP is a path vector protocol. Here, path vector is a method of sending the routes along with routing information. o Configure neighborhood relationship It sends updates to configure the neighborhood relationship manually. Suppose there are two routers R1 and R2. Then, R1 has to send the configure command saying that you are my neighbor. On the other side, R2 also has to send the configure command to R1, saying that R1 is a neighbor of R1. If both the configure commands match, then the neighborhood relationship will get developed between these two routers. o Application layer protocol It is an application layer protocol and uses TCP protocol for reliability. o Metric It has lots of attributes like weight attribute, origin, etc. BGP supports a very rich number of attributes that can affect the path manipulation process. o Administrative distance If the information is coming from the external autonomous system, then it uses 20 administrative distance. If the information is coming from the same autonomous system, then it uses 200 administrative distance.