draft-ietf-idr-add-paths-12.txt   draft-ietf-idr-add-paths-13.txt 
Network Working Group D. Walton Network Working Group D. Walton
Internet-Draft Cumulus Networks Internet-Draft Cumulus Networks
Intended status: Standards Track A. Retana Intended status: Standards Track A. Retana
Expires: May 7, 2016 E. Chen Expires: June 13, 2016 E. Chen
Cisco Systems, Inc. Cisco Systems, Inc.
J. Scudder J. Scudder
Juniper Networks Juniper Networks
November 4, 2015 December 11, 2015
Advertisement of Multiple Paths in BGP Advertisement of Multiple Paths in BGP
draft-ietf-idr-add-paths-12 draft-ietf-idr-add-paths-13
Abstract Abstract
This document defines a BGP extension that allows the advertisement This document defines a BGP extension that allows the advertisement
of multiple paths for the same address prefix without the new paths of multiple paths for the same address prefix without the new paths
implicitly replacing any previous ones. The essence of the extension implicitly replacing any previous ones. The essence of the extension
is that each path is identified by a path identifier in addition to is that each path is identified by a path identifier in addition to
the address prefix. the address prefix.
Status of This Memo Status of This Memo
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on May 7, 2016. This Internet-Draft will expire on June 13, 2016.
Copyright Notice Copyright Notice
Copyright (c) 2015 IETF Trust and the persons identified as the Copyright (c) 2015 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 Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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4. ADD-PATH Capability . . . . . . . . . . . . . . . . . . . . . 3 4. ADD-PATH Capability . . . . . . . . . . . . . . . . . . . . . 3
5. Operation . . . . . . . . . . . . . . . . . . . . . . . . . . 4 5. Operation . . . . . . . . . . . . . . . . . . . . . . . . . . 4
6. Applications . . . . . . . . . . . . . . . . . . . . . . . . 5 6. Applications . . . . . . . . . . . . . . . . . . . . . . . . 5
7. Deployment Considerations . . . . . . . . . . . . . . . . . . 5 7. Deployment Considerations . . . . . . . . . . . . . . . . . . 5
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
9. Security Considerations . . . . . . . . . . . . . . . . . . . 6 9. Security Considerations . . . . . . . . . . . . . . . . . . . 6
10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 6 10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 6
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 6 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
11.1. Normative References . . . . . . . . . . . . . . . . . . 6 11.1. Normative References . . . . . . . . . . . . . . . . . . 6
11.2. Informative References . . . . . . . . . . . . . . . . . 7 11.2. Informative References . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8
1. Introduction 1. Introduction
The BGP specification [RFC4271] defines an Update-Send Process to The BGP specification [RFC4271] defines an Update-Send Process to
advertise the routes chosen by the Decision Process to other BGP advertise the routes chosen by the Decision Process to other BGP
speakers. No provisions are made to allow the advertisement of speakers. No provisions are made to allow the advertisement of
multiple paths for the same address prefix, or Network Layer multiple paths for the same address prefix, or Network Layer
Reachability Information (NLRI). In fact, a route with the same NLRI Reachability Information (NLRI). In fact, a route with the same NLRI
as a previously advertised route implicitly replaces the previous as a previously advertised route implicitly replaces the previous
advertisement. advertisement.
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Send/Receive: Send/Receive:
This field indicates whether the sender is (a) able to receive This field indicates whether the sender is (a) able to receive
multiple paths from its peer (value 1), (b) able to send multiple paths from its peer (value 1), (b) able to send
multiple paths to its peer (value 2), or (c) both (value 3) for multiple paths to its peer (value 2), or (c) both (value 3) for
the <AFI, SAFI>. the <AFI, SAFI>.
If any other value is received, then the capability SHOULD be If any other value is received, then the capability SHOULD be
treated as not understood and ignored [RFC5492]. treated as not understood and ignored [RFC5492].
A BGP speaker that wishes to indicate support for multiple AFI/SAFI
MUST do so by including the information in a single instance of the
ADD-PATH Capability.
5. Operation 5. Operation
The Path Identifier specified in the previous section can be used to The Path Identifier specified in the previous section can be used to
advertise multiple paths for the same address prefix without advertise multiple paths for the same address prefix without
subsequent advertisements replacing the previous ones. Apart from subsequent advertisements replacing the previous ones. Apart from
the fact that this is now possible, the route advertisement rules of the fact that this is now possible, the route advertisement rules of
[RFC4271] are not changed. In particular, a new advertisement for a [RFC4271] are not changed. In particular, a new advertisement for a
given address prefix and a given path identifier replaces a previous given address prefix and a given path identifier replaces a previous
advertisement for the same address prefix and path identifier. If a advertisement for the same address prefix and path identifier. If a
BGP speaker receives a message to withdraw a prefix with a path BGP speaker receives a message to withdraw a prefix with a path
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This document defines a BGP extension that allows the advertisement This document defines a BGP extension that allows the advertisement
of multiple paths for the same address prefix without the new paths of multiple paths for the same address prefix without the new paths
implicitly replacing any previous ones. As a result, multiple paths implicitly replacing any previous ones. As a result, multiple paths
for a large number of prefixes may be received by a BGP speaker for a large number of prefixes may be received by a BGP speaker
potentially depleting memory resources or even causing network-wide potentially depleting memory resources or even causing network-wide
instability. The use of the ADD-PATH Capability is intended to instability. The use of the ADD-PATH Capability is intended to
address specific needs related to, for example, eliminating the MED- address specific needs related to, for example, eliminating the MED-
induced route oscillations in a network induced route oscillations in a network
[I-D.ietf-idr-route-oscillation-stop]. While the applications for [I-D.ietf-idr-route-oscillation-stop]. While the applications for
the ADD-PATH Capability are outside the scope of this document, the the ADD-PATH Capability are outside the scope of this document, the
users are enouraged to exhamine their behavior and potential impact users are encouraged to examine their behavior and potential impact
by studying the best practices described in by studying the best practices described in
[I-D.ietf-idr-add-paths-guidelines]. [I-D.ietf-idr-add-paths-guidelines].
This document introduces no new security concerns in the base This document introduces no new security concerns in the base
operation of BGP [RFC4271]. operation of BGP [RFC4271].
10. Acknowledgments 10. Acknowledgments
We would like to thank David Cook and Naiming Shen for their We would like to thank David Cook and Naiming Shen for their
contributions to the design and development of the extension. contributions to the design and development of the extension.
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