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What Is Border Gateway Protocol (BGP)?

What is BGP? Border Gateway Protocol (BGP) refers to a gateway protocol that enables the internet to exchange routing information between autonomous systems (AS). As networks interact with each other, they need a way to communicate. This is accomplished through peering. BGP makes peering possible. Without it, networks would not be able to send and receive information with each other.

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.

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 secure socket 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.

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.

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.

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.

What Are Autonomous Systems and Who Operates BGP Autonomous Systems?

An autonomous system, also known as a routing domain, consists of a collection of networks that use the same BGP protocols. They are operated by a single administrator or entity. This may be an enterprise, university, or another entity that utilizes a select set of routing protocols.

How Fortinet Can Help

FortiDDoS incorporates BGP Flowspec, which is used to automate how network traffic filtering gets coordinated. This BGP routing enables service providers to drop bad traffic when the BGP network is under a distributed denial-of-service (DDoS) attack. This can prevent a data breach by allowing a site’s security tools to hone in on legitimate exfiltration attacks instead of focusing on false requests. 

Because Fortinet DDoS supports BGP, administrators can more easily safeguard their networks from DDoS attacks.

FAQs

What is Border Gateway Protocol (BGP)?

Border Gateway Protocol (BGP) refers to a gateway protocol that enables the internet to exchange routing information between autonomous systems (AS).

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 that is closest to where the router is.

What are the characteristics of Border Gateway Protocol (BGP)?

The characteristics of BGP include inter-autonomous system configuration, next-hop support, coordination among multiple BGP speakers within an autonomous system, path information, policy support, running over Transmission Control Protocol (TCP), conserving network bandwidth, supporting Classless Inter-Domain Routing (CIDR), and supporting security.

What are the functions of Border Gateway Protocol (BGP)?

The functions of BGP include the sending of negative or positive reachability information and verification that the peers and the network connection between them are functioning correctly.

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.

What are the autonomous systems and who operates BGP autonomous systems?

An autonomous system, also known as a routing domain, consists of a collection of networks that use the same BGP protocols. They are operated by a single administrator or entity. This may be an enterprise, university, or another entity that utilizes a select set of routing protocols.