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Exterior Gateway Protocol formal specification (RFC0904)

IP.com Disclosure Number: IPCOM000003954D
Original Publication Date: 1984-Apr-01
Included in the Prior Art Database: 2000-Sep-13
Document File: 24 page(s) / 64K

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

D.L. Mills: AUTHOR

Abstract

This document is a formal specification of the Exterior Gateway Protocol (EGP), which is used to exchange net-reachability information between Internet gateways belonging to the same or different autonomous systems. The specification is intended as a reference guide for implementation, testing and verification and includes suggested algorithmic parameters suitable for operation over a wide set of configurations, including the ARPANET and many local-network technologies now part of the Internet system.

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Network Working Group D.L. Mills

Request for Comments: 904 April 1984

Exterior Gateway Protocol Formal Specification

0. Status of this Memo

This RFC is the specification of the Exterior Gateway Protocol

(EGP). This document updates RFCs 827 and 888. This RFC specifies a

standard for the DARPA community. Interactions between gateways of

different autonomous systems in the ARPA-Internet must follow this

protocol.

1. Introduction

This document is a formal specification of the Exterior Gateway

Protocol (EGP), which is used to exchange net-reachability information

between Internet gateways belonging to the same or different autonomous

systems. The specification is intended as a reference guide for

implementation, testing and verification and includes suggested

algorithmic parameters suitable for operation over a wide set of

configurations, including the ARPANET and many local-network

technologies now part of the Internet system.

Specifically excluded in this document is discussion on the

background, application and limitations of EGP, which have been

discussed elsewhere (RFC-827, RFC-888). If, as expected, EGP evolves to

include topologies not restricted to tree-structures and to incorporate

full routing capabilities, this specification will be amended or

obsoleted accordingly. However, it is expected that, as new features

are added to EGP, the basic protocol mechanisms described here will

remain substantially unchanged, with only the format and interpretation

of the Update message (see below) changed.

Section 2 of this document describes the nomenclature used, while

Section 3 describes the state-machine model, including events, actions,

parameters and state transitions. Section 4 contains a functional

description of the operation of the machine, together with specific

procedures and algorithms. Appendix A describes the EGP message

formats, while Appendix B contains a summary of the minor differences

between these and the formats described in RFC-888. Appendix C presents

a reachability analysis including a table of composite state transitions

for a system of two communicating EGP gateways.

1.1. Summary and Overview

EGP exists in order to convey net-reachability information between

neighboring gateways, possibly in different autonomous systems. The

protocol includes mechanisms to acquire neighbors, monitor neighbor

reachability and exchange net-reachability information in the form of

Update messages. The protocol is based on periodic polling using

Hello/I-Heard-You (I-H-U) message exchanges to monitor neighbor

reachability and Poll commands to ...