The Internet has become an integral part of our lives that it’s hard to imagine living without it. However, what many of us don’t realize is the complexity that goes into making sure the Internet runs smoothly. At the heart of the Internet are the routing protocols – IGP and BGP. In this article, we will break down the two protocols, what they do, and how they work together to keep the wheels of the Internet turning.
What is IGP?
IGP stands for Interior Gateway Protocol. It is a type of routing protocol that is used to exchange information between routers within an Autonomous System (AS). An AS is a network that is under the control of one organization or entity. The purpose of an IGP is to allow routers within the same AS to communicate with each other, establish the shortest path between them, and forward traffic efficiently.
There are several types of IGPs, including OSPF (Open Shortest Path First), IS-IS (Intermediate System to Intermediate System), and EIGRP (Enhanced Interior Gateway Routing Protocol). OSPF and IS-IS are link-state protocols, which means that routers exchange information about the state of the links and nodes in the network. EIGRP is a hybrid protocol that uses both distance-vector and link-state elements.
What is BGP?
BGP stands for Border Gateway Protocol. It is a type of routing protocol that is used to exchange information between routers in different ASes. The purpose of BGP is to allow routers to communicate with routers in other ASes, establish the shortest path between them, and forward traffic efficiently.
BGP is considerably more complex than IGP because it takes into account factors that are specific to inter-AS routing. These might include the policies of different ISPs and network administrators, the availability of specific paths, and the economic relationships between different ASes. BGP takes all of these factors into account to establish the best path for a given piece of traffic.
How do IGP and BGP work together?
IGP and BGP are complementary protocols, and they work together to ensure that traffic is forwarded efficiently across the Internet. When a router receives a data packet, it first checks its local routing table to see if it has a specific route for that packet. If it doesn’t have one, the router sends the packet to its default gateway. If the gateway is located within the same AS, an IGP is used to forward the packet to the next hop along the shortest path to the destination.
If the gateway is located in a different AS, BGP is used to exchange routing information between the two ASes. BGP uses a variety of metrics, policies, and attributes to determine the best path for the packet. Once the path is established, BGP updates the routing table on the router and forwards the packet to the next hop along the path.
In summary, IGP and BGP are two critical routing protocols that work together to establish and maintain the paths that traffic takes across the Internet. IGPs are used within an AS, while BGP is used between ASes to connect the Internet together. Understanding these protocols and how they work together is essential for anyone who wants to have a basic understanding of how the Internet functions.