What is BGP?

Border Gateway Protocol (BGP) is the postal service of the Internet. When someone drops a letter into a mailbox, the Postal Service processes that piece of mail and chooses a fast, efficient route to deliver that letter to its recipient. Similarly, when someone submits data via the Internet, BGP is responsible for looking at all of the available paths that data could travel and picking the best route, which usually means hopping between autonomous systems.

BGP is the protocol that makes the Internet work by enabling data routing. When a user in Singapore loads a website with origin servers in Argentina, BGP is the protocol that enables that communication to happen quickly and efficiently.

How Does BGP Work?

When you have a network router that connects to other networks, it does not know which network is the best one to send its data to. BGP takes into consideration all the different peering options a router has and chooses the one closest to where the router is. Each potential peer communicates the routing information it has and that gets stored within a routing information base (RIB). BGP can access this information and use it to choose the best peering option.

History of BGP

The Border Gateway Protocol was first described in 1989 in RFC 1105 and has been in use on the Internet since 1994.[4] IPv6 BGP was first defined in RFC 1654 in 1994, and it was improved to RFC 2283 in 1998.

The current version of BGP is version 4 (BGP4), which was published as RFC 4271 in 2006.[5] RFC 4271 corrected errors, clarified ambiguities and updated the specification with common industry practices. The major enhancement was the support for Classless Inter-Domain Routing (CIDR) and the use of route aggregation to decrease the size of routing tables. The new RFC allows BGP4 to carry a wide range of IPv4 and IPv6 “address families”. It is also called the Multiprotocol Extensions which is Multiprotocol BGP (MP-BGP).

Functions of Border Gateway Protocol (BGP)

Initial Peer Acquisition and Authentication

BGP allows the right peer to be identified, authenticated, and connected to, making the network run more efficiently.

Sending of Negative or Positive Reachability Information

BGP sends information regarding whether or not a peer is reachable. This saves time by eliminating errant connections.

Verification That the Peers and the Network Connection Between Them Are Functioning Correctly

Once a connection happens, BGP is able to verify the health of the communication. In this way, BGP facilitates more consistent, reliable connections.

Difference Between External BGP and Internal BGP

Internal BGP refers to a mechanism that gives information about the internal routers in a system. This is done using a mesh topology, which involves routes being received from internal BGP neighbors without them being advertised to other internal BGP neighbors. In this way, an internal BGP system avoids loops. Routing loops are more common in external BGP systems because they do not use a similar mesh topology.

Information Management Functions of BGP Route

Route Storage

With route storage, individual BGPs keep information regarding how to connect with networks within a set of databases. Databases are also used to store routing information that can be accessed by BGP.

Route Update

BGP delivers update messages to advertise pertinent routing information. These are stored in a routing table that becomes available after the system has started up.

Route Selection

The BGP speaker, which advertises routes, only conveys information about the best route to peers.

Route Advertisement

When there is more than one feasible route, BGP only advertises the best one to peers. This helps the network function more efficiently because only viable routes are advertised.

Characteristics of Border Gateway Protocol (BGP)

Inter-autonomous System Configuration

BGP’s inter-autonomous system configuration allows it to make two autonomous systems communicate with each other. Otherwise, they would not be able to connect and share information.

Supports Next-hop Paradigm

The next-hop paradigm dictates that a packet of data goes to the next or most optimal choice among all the potential routers it can be sent to. Because BGP supports next-hop, connections can be optimized for faster network performance, instead of having to navigate far, disparate routing BGP points, wasting valuable time.

Also, because of this support, administrators do not have to configure BGP for next-hop connections.

Coordination Among Multiple BGP Speakers Within an Autonomous System

BGP is able to scan all the available options before deciding which one is the best choice for the next stop of data. This requires its ability to coordinate among more than one BGP speaker at the same time.

Path Information

Within the BGP advertisement system is the path information that includes the next destination and which destinations are reachable.

Policy Support

An administrator can design and implement policies by programming them into the BGP system. This can be used, for example, to choose between routes that exist within the autonomous system and those that exist outside it.

Runs Over TCP

Because BGP runs over Transmission Control Protocol (TCP), it is compatible with the rest of the internet, which uses TCP for communications. TCP makes sure data packets get sent and delivered across networks. BGP also interfaces well with a secure sockets layer (SSL), a virtual private network (VPN), and transport layer security (TLS).

BGP Conserves Network Bandwidth

The conservation of network bandwidth allows an organization to get the most out of its network, and because BGP supports this, it can be used to facilitate efficient network transmissions.

BGP Supports CIDR

Classless Inter-Domain Routing (CIDR) refers to a way to allocate Internet Protocol (IP) addresses so they can be used for IP routing. Because BGP supports CIDR, it does not interfere with how IP addresses get assigned or managed.

BGP Also Supports Security

While BGP does not have any security features inherent to it, it supports the existing security tools and protocols that various networks use. This enables administrators to secure their networks and use BGP simultaneously.