BGP4: Inter-Domain Routing in the Internet, 1st edition

  • John W. Stewart

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BGP4 (Border Gateway Protocol version 4) is the de facto standard inter-domain routing protocol deployed in the Internet today. As the means by which Internet destinations are communicated between subscribers and service providers, BGP4 provides a critical function for Internet operations. Whether you are associated with an Internet service provider or are a system administrator at an organization whose business depends heavily on the Internet, a background in BGP4 is essential.

BGP4: Inter-Domain Routing in the Internet provides a practical introduction to the TCP/IP protocol suite and to routing in general. This concise guide describes the BGP protocol in clear terms and explains messages and rules for processing information through the protocol. In addition to illustrating low-level details of the protocol, the author examines the conceptual way that BGP works in practical networks, the way that BGP4 interacts with other parts of a network, and other details important to its operation. This book also covers the many extensions that have been made to the original specification to increase the protocols' usability and scope of operation.

Specifically, you will find coverage of such key topics as:

  • IP base protocol, including the packet formats, addressing and routing, and other protocol rules
  • Autonomous systems and the distinction between IGPs and EGPs
  • Distance Vector versus Link State Routing Protocols
  • CIDR and how it relates to BGP4
  • Operational details essential to using BGP
  • BGP message types, path attributes, and the route selection process
  • Singly homed and multihomed subscribers
  • BGP interaction with IGP
  • Internal BGP scaling
  • TCP MD5 authentication
  • Other extensions to the protocol

In addition, this book offers a revealing look into how large ISPs work with BGP4, including a discussion on aggregation, filtering transit customers, and public interconnect points. Numerous real-world examples throughout the book demonstrate concepts and implementation techniques.


Table of contents


1. Introduction.

A Brief IP Primer.

Notes on Terminology.

IP Addressing and the Need for Routing.

Autonomous Systems and the Distinction Between IGPs and EGPs.

Distance Vector Versus Link State Routing Protocols.

Distance Vector Protocols.

Link State Protocols.

Classless Inter-Domain Routing.

Setting the Tone for Understanding BGP.

2. The BGP Protocol.

Bringing Up a BGP Session.

The BGP Message Types.

Common Header.





Conceptual Model of Operation.

Base Standard Path Attributes.








Internal Versus External BGP.

BGP Route Selection Process.

3. BGP Operations.

IGP Interaction.

Routing Policy and Transit Versus Nontransit.

Notes About Practice.

A Singly Homed Subscriber.

A Multihomed Subscriber.

Multihoming to a Single Provider.

Multihoming to More Than One Provider.

A View into Providers' Use of BGP.


Filtering Transit Customers.

Public Interconnect Points.

4. BGP Extensions.

Internal BGP Scaling.

Route Reflection.

AS Confederations.

Route Flap Dampening.

BGP Communities.

Protocol Details of the Community Attribute.

Example Use of the Community Attribute: Enforcing Transit Policy.

Well-Known Community Values.

Example Use of the Community Attribute: Automatic Backup Routes.

TCP MD5 Authentication.




Capabilities Negotiation.

Appendix A: Resources.

Internet Standards Process and Documents.


General Routing.



Index. 0201379511T04062001

Published by Addison-Wesley Professional (December 14th 1998) - Copyright © 1999