draft-ietf-idr-best-external-00.txt   draft-ietf-idr-best-external-01.txt 
Network Working Group P. Marques Network Working Group P. Marques
Internet-Draft R. Fernando Internet-Draft R. Fernando
Intended status: Standards Track Juniper Networks Intended status: Standards Track E. Chen
Expires: November 15, 2009 E. Chen Expires: August 8, 2010 P. Mohapatra
P. Mohapatra
Cisco Systems Cisco Systems
May 14, 2009 February 4, 2010
Advertisement of the best external route in BGP Advertisement of the best external route in BGP
draft-ietf-idr-best-external-00.txt draft-ietf-idr-best-external-01.txt
Abstract
The base BGP specifications prevent a BGP speaker from advertising
any route that is not the best route for a BGP destination. This
document specifies a modification of this rule. Routes are divided
into two categories, "external" and "internal". A specification is
provided for choosing a "best external route" (for a particular value
of the Network Layer Reachability Information). A BGP speaker is
then allowed to advertise its "best external route" to its internal
BGP peers, even if that is not the best route for the destination.
The document explains why advertising the best external route can
improve convergence time without causing routing loops. Additional
benefits include reduction of inter-domain churn and avoidance of
permanent route oscillation. The document also generalizes the
notions of "internal" and "external" so that they can be applied to
Route Reflector Clusters and Autonomous System Confederations.
Status of this Memo Status of this Memo
This Internet-Draft is submitted to IETF in full conformance with the This Internet-Draft is submitted to IETF in full conformance with the
provisions of BCP 78 and BCP 79. This document may contain material provisions of BCP 78 and BCP 79.
from IETF Documents or IETF Contributions published or made publicly
available before November 10, 2008. The person(s) controlling the
copyright in some of this material may not have granted the IETF
Trust the right to allow modifications of such material outside the
IETF Standards Process. Without obtaining an adequate license from
the person(s) controlling the copyright in such materials, this
document may not be modified outside the IETF Standards Process, and
derivative works of it may not be created outside the IETF Standards
Process, except to format it for publication as an RFC or to
translate it into languages other than English.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet- other groups may also distribute working documents as Internet-
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The list of current Internet-Drafts can be accessed at The list of current Internet-Drafts can be accessed at
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This Internet-Draft will expire on November 15, 2009. This Internet-Draft will expire on August 8, 2010.
Copyright Notice Copyright Notice
Copyright (c) 2009 IETF Trust and the persons identified as the Copyright (c) 2010 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents in effect on the date of Provisions Relating to IETF Documents
publication of this document (http://trustee.ietf.org/license-info). (http://trustee.ietf.org/license-info) in effect on the date of
Please review these documents carefully, as they describe your rights publication of this document. Please review these documents
and restrictions with respect to this document. carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
Abstract include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the BSD License.
The base BGP specifications prevent a BGP speaker from advertising This document may contain material from IETF Documents or IETF
any route that is not the best route for a BGP destination. This Contributions published or made publicly available before November
document specifies a modification of this rule. Routes are divided 10, 2008. The person(s) controlling the copyright in some of this
into two categories, "external" and "internal". A specification is material may not have granted the IETF Trust the right to allow
provided for choosing a "best external route" (for a particular value modifications of such material outside the IETF Standards Process.
of the Network Layer Reachability Information). A BGP speaker is Without obtaining an adequate license from the person(s) controlling
then allowed to advertise its "best external route" to its internal the copyright in such materials, this document may not be modified
BGP peers, even if that is not the best route for the destination. outside the IETF Standards Process, and derivative works of it may
The document explains why advertising the best external route can not be created outside the IETF Standards Process, except to format
improve convergence time without causing routing loops. Additional it for publication as an RFC or to translate it into languages other
benefits include reduction of inter-domain churn and avoidance of than English.
permanent route oscillation. The document also generalizes the
notions of "internal" and "external" so that they can be applied to
Route Reflector Clusters and Autonomous System Confederations.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 5 1.1. Requirements Language . . . . . . . . . . . . . . . . . . . 4
2. Algorithm for selection of best external route . . . . . . . . 5 2. Algorithm for selection of best external route . . . . . . . . 4
3. Advertisement Rules . . . . . . . . . . . . . . . . . . . . . 6 3. Advertisement Rules . . . . . . . . . . . . . . . . . . . . . . 5
4. Consistency between routing and forwarding . . . . . . . . . . 6 4. Consistency between routing and forwarding . . . . . . . . . . 5
5. Applications . . . . . . . . . . . . . . . . . . . . . . . . . 8 5. Applications . . . . . . . . . . . . . . . . . . . . . . . . . 7
5.1. Fast Connectivity Restoration . . . . . . . . . . . . . . 8 5.1. Fast Connectivity Restoration . . . . . . . . . . . . . . . 7
5.2. Inter-Domain Churn Reduction . . . . . . . . . . . . . . . 9 5.2. Inter-Domain Churn Reduction . . . . . . . . . . . . . . . 8
5.3. Reducing Persistent IBGP oscillation . . . . . . . . . . . 9 5.3. Reducing Persistent IBGP oscillation . . . . . . . . . . . 8
6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 9 6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 8
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 8
8. Security Considerations . . . . . . . . . . . . . . . . . . . 9 8. Security Considerations . . . . . . . . . . . . . . . . . . . . 8
9. Normative References . . . . . . . . . . . . . . . . . . . . . 9 9. Normative References . . . . . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 10 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 9
1. Introduction 1. Introduction
The base BGP specifications prevent a BGP speaker from advertising The base BGP specifications prevent a BGP speaker from advertising
any route that is not the best route for a BGP destination. This any route that is not the best route for a BGP destination. This
document specifies a modification of this rule. Routes are divided document specifies a modification of this rule. Routes are divided
into two categories, "external" and "internal". A specification is into two categories, "external" and "internal". A specification is
provided for choosing a "best external route" (for a particular value provided for choosing a "best external route" (for a particular value
of the Network Layer Reachability Information). A BGP speaker is of the Network Layer Reachability Information). A BGP speaker is
then allowed to advertise its "best external route" to its internal then allowed to advertise its "best external route" to its internal
skipping to change at page 10, line 25 skipping to change at page 10, line 25
[RFC4456] Bates, T., Chen, E., and R. Chandra, "BGP Route [RFC4456] Bates, T., Chen, E., and R. Chandra, "BGP Route
Reflection: An Alternative to Full Mesh Internal BGP Reflection: An Alternative to Full Mesh Internal BGP
(IBGP)", RFC 4456, April 2006. (IBGP)", RFC 4456, April 2006.
[RFC5065] Traina, P., McPherson, D., and J. Scudder, "Autonomous [RFC5065] Traina, P., McPherson, D., and J. Scudder, "Autonomous
System Confederations for BGP", RFC 5065, August 2007. System Confederations for BGP", RFC 5065, August 2007.
Authors' Addresses Authors' Addresses
Pedro Marques Pedro Marques
Juniper Networks Cisco Systems
1194 N. Mathilda Ave 170 W. Tasman Drive
Sunnyvale, CA 94089 San Jose, CA 95134
USA USA
Phone: Phone:
Email: roque@juniper.net Email: roque@cisco.com
Rex Fernando Rex Fernando
Juniper Networks Cisco Systems
1194 N. Mathilda Ave 170 W. Tasman Drive
Sunnyvale, CA 94089 San Jose, CA 95134
USA USA
Phone: Phone:
Email: rex@juniper.net Email: rex@cisco.com
Enke Chen Enke Chen
Cisco Systems Cisco Systems
170 W. Tasman Drive 170 W. Tasman Drive
San Jose, CA 95134 San Jose, CA 95134
USA USA
Phone: Phone:
Email: enkechen@cisco.com Email: enkechen@cisco.com
Pradosh Mohapatra Pradosh Mohapatra
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