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EGP and policy based routing in the new NSFNET backbone (RFC1092)

IP.com Disclosure Number: IPCOM000001901D
Original Publication Date: 1989-Feb-01
Included in the Prior Art Database: 2000-Sep-12
Document File: 5 page(s) / 11K

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

J. Rekhter: AUTHOR

Abstract

The NSFNET backbone routes packets between the Regionals Networks to which it is connected, (i.e., the packets arriving at a backbone entry node are routed to an exit node). How they travel through the network is determined by two components:

This text was extracted from a ASCII Text document.
This is the abbreviated version, containing approximately 27% of the total text.

Network Working Group J. Rekhter

Request for Comments: 1092 T. J. Watson Research Center

February 1989

EGP and Policy Based Routing in the New NSFNET Backbone

Status of this Memo

This memo discusses implementation decisions for routing issues in

the NSFNET, especially in the NSFNET Backbone. Of special concern is

the restriction of routing information to advertize the best route as

established by a policy decision. Distribution of this memo is

unlimited.

Introduction

The NSFNET backbone routes packets between the Regionals Networks to

which it is connected, (i.e., the packets arriving at a backbone

entry node are routed to an exit node). How they travel through the

network is determined by two components:

the NSFNET backbone routing protocol/algorithm, and

additional information about the externally connected networks.

This paper is concerned with how reachability information between the

external networks and the NSFNET backbone is exchanged so that

packets can be routed to the correct destination by using a

reasonable path.

EGP as reachability protocol

The EGP (Exterior Gateway Protocol) routing method will be used to

exchange reachability information between the NSFNET backbone and the

regional networks.

There are several problems with using EGP as a reachability protocol

for routing in a meshed environment. Some EGP components require

further definitions for the NSFNET backbone - regional network

interactions. It should be noted that the use of EGP is only viewed

as an interim measure until better inter autonomous system protocols

are defined and widely deployed for gateways used by regional

networks.

The following is a list of some EGP problems and issues:

The EGP model assumes an engineered spanning tree topology,

however, the NSFNET (due to the presence of backdoor routes) does

not fit into this model. In the NSFNET the same network may be

advertized as reachable by more than one regional network.

Besides the fact that the overall NSFNET does not fit into a

spanning tree model there are serious concerns with the concept

of the "core" (central to the EGP) and its obvious deficiencies.

While EGP is going to isolate intra-Regional routing from the

intra-NSFNET-Backbone routing, it does not address the issue of

false information which may be supplied by regional networks.

EGP by itself does not protect a particular network from unwanted

and unsolicited representation by some regional network. As an

example, if network N1 is reachable through regional network R1

as well as through regional network R2, EGP has no provisions to

specify one of these paths as a primary and one as a secondary,

since there is not generally accepted interpretation of EGP

metrics today. Also, there is nothin...