Introduction to the BGP Protocol


Volker D. Pallas


Introduction to the BGP Protocol

Hey there, fellow network engineers! Today, we’re diving into the intriguing world of the Border Gateway Protocol (BGP). Whether you’ve been routing packets for years or are just curious about how the internet stitches together its vast network tapestry, BGP is a topic worth exploring.

Our journey will cover the who, when, where, what, and why of BGP, ensuring that by the end, you’ll have a solid understanding of this fundamental protocol.

What is BGP?

At its core, BGP is the postal service of the internet, responsible for delivering data packets from one destination to another, spanning across the globe.

It’s a path vector protocol that manages how packets are routed through the internet by enabling data routing decisions based on paths, network policies, or rule-sets configured by network administrators.

BGP is unique because it’s the protocol that makes the internet work, connecting different autonomous systems (AS) – essentially, the large collections of IP networks and routers under the control of a single entity, like an ISP or a large organization.

Who Uses BGP?

BGP is used by network administrators and engineers who manage the networks of Internet Service Providers (ISPs), large enterprises, and even some smaller organizations that require control over their routing policies.

It’s essential for those who need to ensure data packets travel in the most efficient and secure manner possible across the internet or within large private networks.

When Was BGP Developed?

BGP was first introduced in 1989, in RFC 1105, to replace the Exterior Gateway Protocol (EGP). The need for BGP arose from the internet’s expansion, necessitating a more scalable and flexible approach to routing.

Since its inception, BGP has evolved through various versions, with BGP-4, defined in RFC 4271, being the current standard that supports CIDR (Classless Inter-Domain Routing) and has been the backbone of the internet’s routing infrastructure for decades.

Where is BGP Used?

BGP is used everywhere on the internet. It operates between different autonomous systems, making it an Exterior Gateway Protocol (EGP). This global use is what allows you to access websites, stream videos, or send emails across the world.

It’s also used within large organizations to manage traffic within their networks, known as Internal BGP (iBGP).

Why is BGP Important?

BGP’s importance can’t be overstated. It’s the protocol that keeps the internet connected, enabling the exchange of routing information between different networks.

Without BGP, the internet would be a series of isolated networks, unable to communicate with each other. It also allows for route optimization and the implementation of routing policies that can affect performance, reliability, and security.

Understanding BGP Routing

BGP makes decisions based on paths, network policies, or rule-sets. It uses a variety of attributes, like AS_PATH, NEXT_HOP, and ORIGIN, to determine the best path for data to travel. This decision-making process is what enables BGP to route data efficiently across the complex topology of the internet.

BGP and Network Security

While BGP is incredibly powerful, it’s not without its vulnerabilities. Incorrect configurations or malicious attacks, like BGP hijacking, can lead to traffic being misrouted, causing outages or security breaches.

This highlights the need for robust security practices, such as route filtering and the implementation of the Resource Public Key Infrastructure (RPKI) to validate route announcements.

For more on BGP security practices, the NSA (yes!) offers an excellent resource on BGP Best Common Practices, which is worth checking out.

BGP in the Real World

BGP’s application in the real world is vast and varied. It’s used not only to route internet traffic but also to manage the flow of data within large private networks. For instance, content delivery networks (CDNs) rely on BGP to ensure content is delivered from the closest server to the user, optimizing speed and efficiency.

The Future of BGP

As the internet continues to grow and evolve, so too does BGP. With the advent of new technologies and the ever-increasing demand for more efficient and secure routing, BGP is constantly being updated and refined.

The development of protocols like BGPsec aims to address some of the security vulnerabilities inherent in BGP, promising a more secure future for internet routing.

For those looking to dive deeper into BGP and its future, The Internet Engineering Task Force (IETF) is an invaluable resource, offering detailed documentation and discussions on BGP and other internet protocols.