Border Gateway Protocol Complexity

What is BGP Protocol in Networking

Border Gateway Protocol Complexity


What is BGP Protocol in Networking

In the vast interconnected network of the internet, Border Gateway Protocol (BGP) plays a crucial role in ensuring efficient and reliable routing. As the primary protocol for exchanging routing information between internet service providers (ISPs) and networks, BGP serves as the backbone of the internet. In this blog post, we will delve into BGP’s functionalities, benefits, and challenges, shedding light on its significance in today’s digital landscape.

Border Gateway Protocol, commonly known as BGP, is an exterior gateway protocol that facilitates the exchange of routing information between different autonomous systems (AS). An autonomous system represents a collection of networks under a single administrative domain. BGP is responsible for determining the best path for data packets to traverse between ASes, allowing efficient communication across the internet.


Highlights: BGP Protocol in Networking

  • Decrease Complexity

When considering what is BGP protocol in networking, we must first highlight a common misconception that Border Gateway Protocol ( BGP ) is used solely for network scalability, replacing Interior Gateway Protocol ( IGP ) once a specific prefix or router count has been reached. Although BGP does form the base for large networks, an adequately designed IGP can scale tens of thousands of routers.BGP is not just used for scalability; it is used to decrease the complexity of networking rather than size.

  • Split into smaller pieces.

The key to efficient routing protocol design is to start with business design principles and break failure domains into small pieces. Keeping things simple with BGP is critical to stabilizing large networks. What usually begins as a single network quickly becomes multiple networks as the business grows. Easier to split networks into small pieces and to “aggregate” the information as much as possible. Aggregating routing information hides parts of the network and speeds up link/node failure convergence.


You may find the following posts useful for pre-information:

  1. Port 179
  2. SDN Traffic Optimizations
  3. What does SDN mean? This post uses a BGP SDN approach to networking.
  4. BGP SDN
  5. Segment routing
  6. Merchant Silicon


What is BGP Protocol in Networking

Key What is BGP Discussion Points:

  • Introduction to BGP protocol and what is involved.

  • Highlighting the details on BGP scalability.

  • Critical points on BGP protocol and the use of policy.

  • Technical details on traffic engineering with BGP.

  • A final note on IGPs.


Back to basics with BGP

BGP is mature and powers the internet. Many mature implementations of BGP exist, including in the open-source networking world. A considerable benefit to BGP is that it is less chatty than its link state and supports multi protocols (i.e., it supports advertising IPv4, IPv6, Multiprotocol Label Switching (MPLS), and VPNs natively). Remember that BGP has been understood for decades for helping internet-connected systems find one another. However, it is helpful within a single data center, as well. In addition, BGP is standards-based and supported by many free and open-source software packages.

How does BGP work?

BGP operates on a distributed architecture, where routers exchange routing information using rules and policies. It uses a path-vector algorithm to select the best path based on various attributes, such as the number of AS hops and the quality of the network links. BGP relies on the concept of peering, where routers establish connections with each other to exchange routing updates.

  • A key point: Lab on BGP Dampening

In the following sample, we have two routers with BGP configured. Each BGP peer is in its own AS, and BGP dampening is configured on R2 only. Notice the output of the debug ip bgp dampening on R2 once the loopback on R1 is shut down.

The concept behind BGP dampening is relatively simple. When a router detects a route flapping, it assigns a penalty to that route. The penalty is based on the number of consecutive flaps and the configured dampening parameters. As the penalty accumulates, the route’s desirability decreases, making it less likely to be advertised to other routers.

The purpose of BGP dampening is to discourage the propagation of unstable routes and prevent them from spreading throughout the network. By penalizing flapping routes, BGP dampening helps to stabilize the network by reducing the number of updates sent and minimizing the impact of routing instability.

BGP dampening
Diagram: BGP Dampening

The Significance of BGP:

Scalability: BGP’s hierarchical structure enables it to handle the massive scale of the global internet. By dividing the internet into smaller autonomous systems, BGP efficiently manages routing information, reducing the burden on individual routers and improving scalability.

Path Selection: BGP allows network administrators to define policies for path selection, giving them control over traffic flow. This flexibility enables organizations to optimize network performance, direct traffic through preferred paths, and ensure efficient resource utilization.

Internet Resilience: BGP’s ability to dynamically adapt to changes in network topology is crucial for ensuring internet resilience. If a network or path becomes unavailable, BGP can quickly reroute traffic through alternative paths, minimizing disruptions and maintaining connectivity.

Challenges and Security Concerns:

BGP Hijacking: BGP’s reliance on trust-based peering relationships makes it susceptible to hijacking. Malicious actors can attempt to divert traffic by announcing false routing information, potentially leading to traffic interception or disruption. Initiatives like Resource Public Key Infrastructure (RPKI) aim to mitigate these risks by introducing cryptographic validation mechanisms.

Route Flapping: Unstable network connections or misconfigurations can cause routes to appear and disappear, causing route flapping frequently. This can lead to increased network congestion, suboptimal routing, and unnecessary router strain. Network administrators need to monitor and address route flapping issues carefully.


Policy-oriented control plane reduces network complexity.

BGP is a policy-oriented control plane-routing protocol used to create islands of networks that match business requirements to administrative domains. When multiple business units present unique needs, designing all those special requirements using a single set of routing policies is hard. BGP can decrease policy complexity and divide the complexity into a manageable aggregation of policies.

When considering what is BGP protocol in networking
Diagram: When considering what is BGP protocol in networking


Two business units, for example, HR, represented by a router on the left, and the Sales department, represented by a router on the right. The middle networks form a private WAN, used simply as transit. However, the business has decided that these networks should be treated differently and have different traffic paths. For example, HR must pass through the top section of routers, and Sales must pass through the bottom half of routers. With an Interior Gateway Protocol ( IGP ), such as OSPF, traffic engineering can be accomplished by manipulating the cost of the links to influence the traffic path.

However, the metrics on the links must be managed on a per-destination basis. If you have to configure individual links per destination, it will become almost impossible to do with a link-state IGP. If BGP is used, this logic can be encoded using Local Preference or Multiple Exit Discriminator. Local preference is used for a single AS design, and MED is used for multiple AS. Local preference is local and does not traverse multiple AS.


  • A final note: When considering what is BGP protocol in networking

Networks grow and should be allowed to grow organically. Each business unit may require several different topologies and design patterns. Trying to design all these additional requirements would increase network complexity. In the context of a single IGP, it may add too many layers of complexity. BGP provides a manageable approach to policy abstraction by controlling specific network traffic patterns within and between Autonomous Systems.



Border Gateway Protocol (BGP) plays a vital role in ensuring the smooth functioning of the internet by facilitating efficient routing between autonomous systems. Its scalability, flexibility in path selection, and ability to adapt to network changes contribute to the overall resilience and reliability of the internet. However, challenges such as BGP hijacking and route flapping require ongoing attention and mitigation efforts to maintain the security and stability of BGP-based networks. By understanding the intricacies of BGP, network administrators can effectively manage their networks and contribute to a robust and interconnected internet ecosystem.


Border Gateway Protocol Complexity


Matt Conran
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