Hey all, today let us get connected with BGP. BGP stands for Border Gateway Protocol and it is a routing protocol just like. RIP, OSPF, EIGRP. It is inter-Autonomous System routing protocol. Firstly, let us see what Autonomous System (AS) means in the world of BGP.
Let us consider a scenario where you and your friends want to plan a journey to Goa. Now you have two options, you can either go by bus or by own car. If you decide to go by Bus, then you must agree to their policies like the cost of travel, the number of halts, the route to destination etc. And if you decide to go by your vehicle, you can define your own policies, to make the journey memorable. The following image shows the scenario you have imagined:
As you can see above, Bus and Car owners (administrator) have defined their own policies. You can consider Bus and Car as two Autonomous Systems, having their own policies, terms of administration and any customer who agrees to these policies become part of that AS. Thus, an Autonomous System is a collection of devices who are under a common administrative authority. As you might have guessed, in the Internet, such authorities are Internet Service Providers (ISP). So, customers under one ISP make an AS.
Now, suppose one of your friend decides to take the bus and join you guys after two halts. In that case, you must be aware of the path taken by the bus, time of the third halt, duration of the halt, so that you can pick your friend, which requires you to interact with your friend who is part of Bus AS. Here comes inter-AS communication.
BGP will help you connect with your friend, as you can see above. Your friend here has utilized advantages of policies defined by you and the bus. Smart hmm 🙂
Well, you might have now understood, that BGP is inter-AS protocol. IGP protocols are used within an AS. Unlike, IGP routing protocols, BGP does not provide routes on metrics or link states, but it selects a path which requires less number of AS traveling. We all know, the Internet is all about ISPs, BGP creates a connection between these ISPs, thus, BGP is the Internet protocol. Also, route selection can be controlled using BGP, based on the policies of AS.
After this newbie introduction of BGP, you must be interested to know more about it. Stay tuned then..!!
Happy networking with BGP..!!!