The Internet routing topology continually changes as new networks join and existing ones disappear. Keeping up with these changes is hard work for routers. They must store all the routes in their routing information bases (RIB), which consume lots of memory.
Routers also announce their routes to BGP peers. If these announcements get leaked to external peers, it can cause problems such as the 2017 Internet outage when social media apps went down in parts of the U.S.
It’s Like a GPS App
The Internet is broken up into many different networks called Autonomous Systems. Large organizations like ISPs, companies, government agencies, and universities run these routers. BGP is responsible for ensuring that these separate networks can connect.
Each network in an Autonomous System has its routing table. BGP combines information from these tables to determine the best route for each data packet. It also helps to prevent “looping,” where a package is sent back and forth between the same servers and routers, leading to latency issues. It’s essential to understand how does BGP work and how it gives additional security. A key aspect of BGP is that it’s highly resilient. BGP will look for other backup routes if one connection between two Autonomous Systems goes down. This allows the Internet to work well, even with massive network connections.
It’s Like a Map
BGP is a routing protocol that allows routers to quickly determine the best path to a destination on the Internet. It is used in large networks, including ISPs, wide area networks and infrastructure-as-a-service environments. It also helps provide redundancy by allowing routers to switch to an alternative connection if one goes down easily. It is a common tool for managing network connectivity, but it can be challenging to configure correctly.
It has been likened to GPS applications on mobile phones, as it provides a continuously updated map from which routers choose the most efficient route. However, the best way is only sometimes the shortest, and other factors can influence the decision. For example, a network may want to avoid routing traffic through another provider in case of an outage or because they are overpaying for bandwidth.
The information BGP shares with other routers is stored in a routing table called the Routing Information Base (RIB). It contains both routes directly connected to the router and those learned from its peers. The RIB is constantly updated as new information is added or removed from the routing topology.
A routing problem in a single router can have widespread consequences. This is especially true when a router has multiple interfaces that can communicate with each other. If a router is configured to share its best routes with all of its peers, for instance, it could cause requests to websites such as Twitter and Facebook to go down in many parts of the world.
It’s Like a Database
BGP is the protocol to direct Internet traffic by exchanging routing information between edge routers. Each autonomous system (AS) shares routes with its neighboring AS peers by announcing network prefixes. The AS peer then decides how to forward the packet based on several factors. It may choose the shortest path, the lowest cost, or other criteria.
Every router maintains a local database of all the network prefixes it receives from its peers. This database is called a routing table. Each router also applies standards and vendor-specific metrics to select which routes to advertise. These criteria can include MED, weight, and origin/AS-path. Routers can use additional attributes such as dmzlink-bw to configure bandwidth ratios to route traffic across multiple links.
Each router has a limited processing capacity to process updates. When this capacity is exceeded, the router will begin to lag. This can lead to out-of-sync routes and even affect other routers.
The BGP protocol has a feature that allows each AS to control the time it takes to transmit routing information to its neighbors. This feature is called local preference. It enables the AS to set a preferred route different from the best path in the BGP routing table. This preferred route is based on the router’s path attribute values and internal routing policy.
It’s Like a Router
As the Internet continues to grow, routing information must be updated. The BGP protocol facilitates this by requiring routers to exchange routing information with neighbor interfaces called peers. However, it could be more foolproof. Information can fail to be transmitted or can be incorrectly formatted. As a result, routers can get out of sync with their peers. This can cause route flaps that disrupt traffic flow.
BGP routers collect routing information from their connected peer networks and then advertise it internally to other BGP routers in their autonomous system. These routes are then used to route traffic to other networks on the Internet. For example, your home computer might be part of an AS managed by your ISP. Your ISP might then use BGP to connect your home computer to a website outside its network.
Each BGP router maintains a conceptual adjacent routing information base, Adj-RIB-In, and a local routing information base, Loc-RIB. The router applies various standard and implementation-dependent metrics to determine if a new route should be installed in the Adj-RIB-In, or if a current way should be withdrawn from the Loc-RIB.
BGP has been compared to the Postal Service of the Internet in that it connects networks like towns bordering one another.Â
