What is Exterior Gateway Protocol (EGP)?

The Exterior Gateway Protocol (EGP) stands as a pivotal technology in the realm of computer networking, orchestrating how different networks communicate across the vast expanse of the internet. Originating from an era where the internet’s architecture was taking shape, EGP facilitated the exchange of routing information between distinct autonomous systems, ensuring data packets found their way across complex, interconnected networks. This article embarks on a comprehensive journey through the intricacies of EGP, shedding light on its mechanisms, historical significance, and the role it plays in the grand tapestry of network communication. As we unravel the layers of EGP, we aim to provide a thorough understanding of its operations, contributions to the internet’s development, and its eventual succession by more advanced protocols.

What is Exterior Gateway Protocol (EGP)?

Exterior Gateway Protocol (EGP) is an obsolete routing protocol that was used for data exchange between neighboring gateway hosts in autonomous systems. EGP was frequently used by research institutes, universities, government agencies, and private organizations, but was replaced by the Border Gateway Protocol (BGP).

EGP is based on periodic message exchange polling for neighbor reachability and poll commands to request update responses. EGP is documented in RFC 904, which was published in April of 1984. The Exterior Gateway Protocol is also known as the External Gateway Protocol.

How does it work?

EGP was originally designed to communicate reachability to and from the Advanced Research Projects Agency Network (ARPANET) core routers. Information was passed from individual source nodes in distinct Internet administrative domains called autonomous systems (ASs) up to the core routers, which passed the information through the backbone until it could be passed down to the destination network within another AS.

Unlike most other protocols, EGP is focused on network reachability and does not consider any metrics to calculate the best path. EGP has three major functions:

• Establish a set of neighbors
• Check the status of neighbors (if they are alive/reachable)
• Inform neighbors of the networks that are reachable within their ASs

Importance of Exterior Gateway Protocol

The term Exterior Gateway Protocol (EGP) is important in technology because it plays a crucial role in the exchange of routing information between different autonomous systems on the internet.

EGP is designed to connect large networks operated by separate entities such as Internet Service Providers (ISPs) and large enterprises, facilitating communication and ensuring seamless data transfer between these networks.

As part of the overall routing process, EGP aids in handling traffic flow, fault tolerance, and load balancing on the global internet infrastructure.

By providing a standardized method of sharing routing information, it enables routers to make informed decisions about the best path for data packets to travel, ultimately leading to an efficient and reliable internet experience for end-users.

Benefits of Exterior Gateway Protocol

EGP offers several key benefits:

• Scalability: EGP enables networks to scale efficiently by providing a standardized method for routing data between autonomous systems. This scalability is crucial as the internet continues to grow and evolve.
• Fault Tolerance: By allowing routers to dynamically adapt to changes in network topology, EGP helps ensure that data can still be routed even in the event of network failures or outages.
• Security: EGP supports authentication mechanisms that help verify the legitimacy of routing updates, reducing the risk of malicious attacks or unauthorized access to network infrastructure.
• Performance Optimization: By selecting the most efficient paths for data transmission, EGP helps minimize latency and optimize network performance, resulting in faster and more reliable communication.

Exterior Gateway Protocol vs. Interior Gateway Protocol

Exterior Gateway Protocol (EGP) and Interior Gateway Protocol (IGP) serve distinct purposes in network routing.

• Scope: EGP operates between different autonomous systems, while IGP functions within a single autonomous system.
• Examples: EGP includes protocols like Border Gateway Protocol (BGP), whereas IGP encompasses protocols such as Open Shortest Path First (OSPF) and Routing Information Protocol (RIP).

Challenges and Limitations of EGP

The Exterior Gateway Protocol (EGP), while innovative for its time, faced several challenges and limitations that ultimately led to its replacement by more capable protocols. These limitations highlight the evolutionary path of Internet routing technologies and the continuous effort to optimize network communication.

Limited Path Information

EGP was designed to exchange basic reachability information between autonomous systems, without the ability to convey the path that data should take. This limitation hindered its effectiveness in managing complex routing scenarios and made it impossible to implement policies based on path attributes or to perform load balancing.

Scalability Issues

As the Internet grew, EGP’s scalability limitations became increasingly apparent. The protocol was not designed to handle the vast number of networks and the intricate web of connections that characterize the modern Internet. Its inability to manage multiple routes to the same destination or adapt to rapid changes in network topology limited its utility in a rapidly expanding global network.

Lack of Policy-Based Control

EGP did not support policy-based routing decisions, a critical feature for managing the flow of traffic across diverse and independently operated networks. This limitation restricted network administrators’ ability to tailor routing to meet specific needs, such as security requirements, cost considerations, or traffic load balancing.

Transition to BGP

The challenges and limitations of EGP underscored the need for a more advanced and flexible routing protocol, leading to the development and adoption of BGP. BGP addressed the shortcomings of EGP by introducing capabilities such as path vector routing, policy-based decision-making, and enhanced scalability and flexibility. This transition marked a significant advancement in the Internet’s routing infrastructure, enabling it to support the complex, dynamic nature of today’s networked world.