draft-ietf-idr-add-paths-10.txt   draft-ietf-idr-add-paths-11.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: April 27, 2015 E. Chen Expires: April 9, 2016 E. Chen
Cisco Systems, Inc. Cisco Systems, Inc.
J. Scudder J. Scudder
Juniper Networks Juniper Networks
October 24, 2014 October 7, 2015
Advertisement of Multiple Paths in BGP Advertisement of Multiple Paths in BGP
draft-ietf-idr-add-paths-10 draft-ietf-idr-add-paths-11
Abstract Abstract
In this document we propose a BGP extension that allows the This document defines a BGP extension that allows the advertisement
advertisement of multiple paths for the same address prefix without of multiple paths for the same address prefix without the new paths
the new paths implicitly replacing any previous ones. The essence of implicitly replacing any previous ones. The essence of the extension
the extension is that each path is identified by a path identifier in is that each path is identified by a path identifier in addition to
addition to the address prefix. the address prefix.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
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 April 27, 2015. This Internet-Draft will expire on April 9, 2016.
Copyright Notice Copyright Notice
Copyright (c) 2014 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
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to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
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the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
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1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Specification of Requirements . . . . . . . . . . . . . . 2 1.1. Specification of Requirements . . . . . . . . . . . . . . 2
2. How to Identify a Path . . . . . . . . . . . . . . . . . . . 3 2. How to Identify a Path . . . . . . . . . . . . . . . . . . . 3
3. Extended NLRI Encodings . . . . . . . . . . . . . . . . . . . 3 3. Extended NLRI Encodings . . . . . . . . . . . . . . . . . . . 3
4. ADD-PATH Capability . . . . . . . . . . . . . . . . . . . . . 4 4. ADD-PATH Capability . . . . . . . . . . . . . . . . . . . . . 4
5. Operation . . . . . . . . . . . . . . . . . . . . . . . . . . 5 5. Operation . . . . . . . . . . . . . . . . . . . . . . . . . . 5
6. Applications . . . . . . . . . . . . . . . . . . . . . . . . 5 6. Applications . . . . . . . . . . . . . . . . . . . . . . . . 5
7. Deployment Considerations . . . . . . . . . . . . . . . . . . 6 7. Deployment Considerations . . . . . . . . . . . . . . . . . . 6
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
9. Security Considerations . . . . . . . . . . . . . . . . . . . 6 9. Security Considerations . . . . . . . . . . . . . . . . . . . 6
10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 6 10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 7
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 6 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
11.1. Normative References . . . . . . . . . . . . . . . . . . 6 11.1. Normative References . . . . . . . . . . . . . . . . . . 7
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.
In this document we propose a BGP extension that allows the This document defines a BGP extension that allows the advertisement
advertisement of multiple paths for the same address prefix without of multiple paths for the same address prefix without the new paths
the new paths implicitly replacing any previous ones. The essence of implicitly replacing any previous ones. The essence of the extension
the extension is that each path is identified by a path identifier in is that each path is identified by a path identifier in addition to
addition to the address prefix. the address prefix.
1.1. Specification of Requirements 1.1. Specification of Requirements
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119]. document are to be interpreted as described in [RFC2119].
2. How to Identify a Path 2. How to Identify a Path
As defined in [RFC4271], a path refers to the information reported in As defined in [RFC4271], a path refers to the information reported in
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This field is the same as the one used in [RFC4760]. This field is the same as the one used in [RFC4760].
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
treated as not understood and ignored [RFC5492].
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
identifier not seen before, it SHOULD silently ignore it. identifier not seen before, it SHOULD silently ignore it.
For a BGP speaker to be able to send multiple paths to its peer, that For a BGP speaker to be able to send multiple paths to its peer, that
BGP speaker MUST advertise the ADD-PATH capability with the Send/ BGP speaker MUST advertise the ADD-PATH capability with the Send/
Receive field set to either 2 or 3, and MUST receive from its peer Receive field set to either 2 or 3, and MUST receive from its peer
the ADD-PATH capability with the Send/Receive field set to either 1 the ADD-PATH capability with the Send/Receive field set to either 1
or 3, for the corresponding <AFI, SAFI>. or 3, for the corresponding <AFI, SAFI>.
A BGP speaker MUST follow the existing procedures in generating an A BGP speaker MUST follow the procedures defined in [RFC4271] when
UPDATE message for a particular <AFI, SAFI> to a peer unless the BGP generating an UPDATE message for a particular <AFI, SAFI> to a peer
speaker advertises the ADD-PATH Capability to the peer indicating its unless the BGP speaker advertises the ADD-PATH Capability to the peer
ability to send multiple paths for the <AFI, SAFI>, and also receives indicating its ability to send multiple paths for the <AFI, SAFI>,
the ADD-PATH Capability from the peer indicating its ability to and also receives the ADD-PATH Capability from the peer indicating
receive multiple paths for the <AFI, SAFI>, in which case the speaker its ability to receive multiple paths for the <AFI, SAFI>, in which
MUST generate a route update for the <AFI, SAFI> based on the case the speaker MUST generate a route update for the <AFI, SAFI>
combination of the address prefix and the Path Identifier, and use based on the combination of the address prefix and the Path
the extended NLRI encodings specified in this document. The peer Identifier, and use the extended NLRI encodings specified in this
SHALL act accordingly in processing an UPDATE message related to a document. The peer SHALL act accordingly in processing an UPDATE
particular <AFI, SAFI>. message related to a particular <AFI, SAFI>.
A BGP speaker SHOULD include the bestpath when more than one path are A BGP speaker SHOULD include the bestpath when more than one path are
advertised to a neighbor unless the bestpath is a path received from advertised to a neighbor unless the bestpath is a path received from
that neighbor. that neighbor.
As the Path Identifiers are locally assigned, and may or may not be As the Path Identifiers are locally assigned, and may or may not be
persistent across a control plane restart of a BGP speaker, an persistent across a control plane restart of a BGP speaker, an
implementation SHOULD take special care so that the underlying implementation SHOULD take special care so that the underlying
forwarding plane of a "Receiving Speaker" as described in [RFC4724] forwarding plane of a "Receiving Speaker" as described in [RFC4724]
is not affected during the graceful restart of a BGP session. is not affected during the graceful restart of a BGP session.
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of additional information is outside the scope of this document. of additional information is outside the scope of this document.
8. IANA Considerations 8. IANA Considerations
IANA has assigned capability number 69 for the ADD-PATH Capability IANA has assigned capability number 69 for the ADD-PATH Capability
described in this document. This registration is in the BGP described in this document. This registration is in the BGP
Capability Codes registry. Capability Codes registry.
9. Security Considerations 9. Security Considerations
This document introduces no new security concerns to BGP or other This document defines a BGP extension that allows the advertisement
specifications referenced in this document. of multiple paths for the same address prefix without the new paths
implicitly replacing any previous ones. As a result, multiple paths
for a large number of prefixes may be received by a BGP speaker
potentially depleting memory resources or even causing network-wide
instability. The use of the ADD-PATH Capability is intended to
address specific needs related to, for example, eliminating the MED-
induced route oscillations in a network
[I-D.ietf-idr-route-oscillation-stop]. While the applications for
the ADD-PATH Capability are outside the scope of this document, the
users are enouraged to exhamine their behavior and potential impact
by studying the best practices described in
[I-D.ietf-idr-add-paths-guidelines].
This document introduces no new security concerns in the base
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.
Many people have made valuable comments and suggestions, including Many people have made valuable comments and suggestions, including
Rex Fernando, Eugene Kim, Danny McPherson, Dave Meyer, Pradosh Rex Fernando, Eugene Kim, Danny McPherson, Dave Meyer, Pradosh
Mohapatra, Keyur Patel, Robert Raszuk, Eric Rosen, Srihari Sangli, Mohapatra, Keyur Patel, Robert Raszuk, Eric Rosen, Srihari Sangli,
Dan Tappan, Mark Turner, Jeff Haas and Jay Borkenhagen. Dan Tappan, Mark Turner, Jeff Haas, Jay Borkenhagen and Mach Chen.
11. References 11. References
11.1. Normative References 11.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC3107] Rekhter, Y. and E. Rosen, "Carrying Label Information in [RFC3107] Rekhter, Y. and E. Rosen, "Carrying Label Information in
BGP-4", RFC 3107, May 2001. BGP-4", RFC 3107, DOI 10.17487/RFC3107, May 2001,
<http://www.rfc-editor.org/info/rfc3107>.
[RFC4271] Rekhter, Y., Li, T., and S. Hares, "A Border Gateway [RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A
Protocol 4 (BGP-4)", RFC 4271, January 2006. Border Gateway Protocol 4 (BGP-4)", RFC 4271,
DOI 10.17487/RFC4271, January 2006,
<http://www.rfc-editor.org/info/rfc4271>.
[RFC4760] Bates, T., Chandra, R., Katz, D., and Y. Rekhter, [RFC4760] Bates, T., Chandra, R., Katz, D., and Y. Rekhter,
"Multiprotocol Extensions for BGP-4", RFC 4760, January "Multiprotocol Extensions for BGP-4", RFC 4760,
2007. DOI 10.17487/RFC4760, January 2007,
<http://www.rfc-editor.org/info/rfc4760>.
[RFC5492] Scudder, J. and R. Chandra, "Capabilities Advertisement [RFC5492] Scudder, J. and R. Chandra, "Capabilities Advertisement
with BGP-4", RFC 5492, February 2009. with BGP-4", RFC 5492, DOI 10.17487/RFC5492, February
2009, <http://www.rfc-editor.org/info/rfc5492>.
11.2. Informative References 11.2. Informative References
[I-D.ietf-idr-add-paths-guidelines]
Uttaro, J., Francois, P., Patel, K., Mohapatra, P., Haas,
J., Simpson, A., and R. Fragassi, "Best Practices for
Advertisement of Multiple Paths in IBGP", draft-ietf-idr-
add-paths-guidelines-07 (work in progress), December 2014.
[I-D.ietf-idr-route-oscillation-stop]
Walton, D., Retana, A., Chen, E., and J. Scudder, "BGP
Persistent Route Oscillation Solutions", draft-ietf-idr-
route-oscillation-stop-00 (work in progress), February
2015.
[I-D.pmohapat-idr-fast-conn-restore] [I-D.pmohapat-idr-fast-conn-restore]
Mohapatra, P., Fernando, R., Filsfils, C., and R. Raszuk, Mohapatra, P., Fernando, R., Filsfils, C., and R. Raszuk,
"Fast Connectivity Restoration Using BGP Add-path", draft- "Fast Connectivity Restoration Using BGP Add-path", draft-
pmohapat-idr-fast-conn-restore-03 (work in progress), pmohapat-idr-fast-conn-restore-03 (work in progress),
January 2013. January 2013.
[RFC3345] McPherson, D., Gill, V., Walton, D., and A. Retana, [RFC3345] McPherson, D., Gill, V., Walton, D., and A. Retana,
"Border Gateway Protocol (BGP) Persistent Route "Border Gateway Protocol (BGP) Persistent Route
Oscillation Condition", RFC 3345, August 2002. Oscillation Condition", RFC 3345, DOI 10.17487/RFC3345,
August 2002, <http://www.rfc-editor.org/info/rfc3345>.
[RFC4724] Sangli, S., Chen, E., Fernando, R., Scudder, J., and Y. [RFC4724] Sangli, S., Chen, E., Fernando, R., Scudder, J., and Y.
Rekhter, "Graceful Restart Mechanism for BGP", RFC 4724, Rekhter, "Graceful Restart Mechanism for BGP", RFC 4724,
January 2007. DOI 10.17487/RFC4724, January 2007,
<http://www.rfc-editor.org/info/rfc4724>.
Authors' Addresses Authors' Addresses
Daniel Walton Daniel Walton
Cumulus Networks Cumulus Networks
185 E. Dana Street 185 E. Dana Street
Mountain View, CA 94041 Mountain View, CA 94041
US US
Email: dwalton@cumulusnetworks.com Email: dwalton@cumulusnetworks.com
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