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What is BGP?

Border Gateway Protocol (BGP) functions as an Exterior Gateway Protocol (EGP) that routes data between different autonomous systems on the internet. RFC 4271 specifies BGP, highlighting its crucial role in maintaining the global internet’s vast, interconnected landscape.

Imagine BGP as the internet’s diplomatic mediator, managing how different countries (or autonomous systems) interact to route data. It doesn’t just find the shortest path; it chooses the best route based on a set of agreed-upon rules.

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How is BGP Different from Other Routing Protocols?

BGP distinguishes itself from other routing protocols with its operational scope and unique features:

Scope of Application:

Unlike Interior Gateway Protocols (IGPs) that manage routing within a single autonomous system, BGP handles routing between autonomous systems, managing how data traverses the entire internet.

Policy-Based Routing:

BGP supports policy-based routing, enabling network administrators to configure routing decisions based on predefined policies rather than solely on path metrics. This feature is crucial for managing complex network relationships and agreements across various networks.

Path Vector Protocol:

BGP uses different path attributes to decide the best paths, so it is considered as a path vector protocol. The methods used by BGP protocol ensures a clear and loop-free path for data packets, providing more precise route control and enhanced data transmission reliability.

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Features of BGP Protocol:

BGP demonstrates its pivotal role in internet infrastructure through several key features:

Robustness and Stability:

BGP withstands route changes and network disruptions, ensuring consistent internet connectivity.

Configurability and Flexibility:

With its policy-based routing, BGP adjusts finely to suit various network scenarios and requirements, making it exceptionally adaptable.

Efficient Communication:

BGP increases communication efficiency by transmitting only updates to routing tables, rather than the full tables, thus conserving bandwidth for routing information.

Security Features:

With advancements like BGPsec, BGP enhances its security measures, providing mechanisms for authenticating and verifying the integrity of routing information to defend against routing attacks.

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BGP Packet Types:

Border Gateway Protocol (BGP) utilizes four distinct types of packets to manage and maintain routing information between autonomous systems, which is essential for the seamless operation of the internet.

1. OPEN Packet:

The OPEN packet kicks off the conversation between two BGP routers, setting the stage for a fruitful exchange. It’s like introducing yourself at a meeting, stating your name (BGP router identifier), where you come from (autonomous system number), and how long you intend to stay in the discussion (hold time). The negotiation of session parameters like BGP version and hold time is critical because it sets the rules of the engagement, ensuring both parties are on the same page and the connection remains active as needed.

2. UPDATE Packet:

UPDATE packets are the workhorses of BGP, carrying the bulk of routing information. They announce new routes to add to the network’s map or old routes that need to be erased, similar to updating a travel itinerary with new destinations or removing canceled flights. By communicating these updates, the UPDATE packet ensures that all routers have the most current map of the network, facilitating efficient and effective routing decisions.

3. KEEPALIVE Packet:

Sent regularly, KEEPALIVE packets act as a pulse check between BGP peers. They’re like periodic nods in a conversation, signaling, “I’m still here, and I’m listening. These packets are crucial for maintaining the session, ensuring that the connection doesn’t drop if there’s a lull in the conversation. They help prevent the premature termination of a session due to timeouts.

4. NOTIFICATION Packet:

When something goes wrong in the BGP dialogue, a NOTIFICATION packet is sent out, akin to sounding an alarm during an emergency. This packet immediately ends the session and alerts the other router to the issue. These packets are essential for quick communication about errors like protocol violations or hold timer expirations. They prompt a reset of the session, which helps in troubleshooting and maintaining network stability.

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Next >>> How BGP Works?

Previous >>> Understanding IGP and EGP

Further Reading : RFC 4271