draft-ietf-idr-route-oscillation-stop-01.txt   draft-ietf-idr-route-oscillation-stop-02.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 9, 2016 E. Chen Expires: October 13, 2016 E. Chen
Cisco Systems, Inc. Cisco Systems, Inc.
J. Scudder J. Scudder
Juniper Networks Juniper Networks
October 7, 2015 April 11, 2016
BGP Persistent Route Oscillation Solutions BGP Persistent Route Oscillation Solutions
draft-ietf-idr-route-oscillation-stop-01 draft-ietf-idr-route-oscillation-stop-02
Abstract Abstract
In this document we present two sets of paths for an address prefix This document presents two sets of paths for an address prefix that
that can be advertised by a BGP route reflector or confederation ASBR can be advertised by a BGP route reflector or confederation ASBR to
to eliminate the MED-induced route oscillations in a network. The eliminate the MED-induced route oscillations in a network. The first
first set involves all the available paths, and would achieve the set involves all the available paths, and would achieve the same
same routing consistency as the full IBGP mesh. The second set, routing consistency as the full IBGP mesh. The second set, which is
which is a subset of the first one, involves the neighbor-AS based a subset of the first one, involves the neighbor-AS based Group Best
Group Best Paths, and would be sufficient to eliminate the MED- Paths, and would be sufficient to eliminate the MED-induced route
induced route oscillations (subject to certain commonly adopted oscillations (subject to certain commonly adopted topological
topological constrains). constrains).
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 9, 2016. This Internet-Draft will expire on October 13, 2016.
Copyright Notice Copyright Notice
Copyright (c) 2015 IETF Trust and the persons identified as the Copyright (c) 2016 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
carefully, as they describe your rights and restrictions with respect carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
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should be limited to those prefixes which are affected by MED-induced should be limited to those prefixes which are affected by MED-induced
route oscillation in a network carrying a large number of alternate route oscillation in a network carrying a large number of alternate
paths. A detailed description of how these oscillations can occur paths. A detailed description of how these oscillations can occur
can be found in [RFC3345]; the description of how a node would can be found in [RFC3345]; the description of how a node would
locally detect such condition is outside the scope of this document. locally detect such condition is outside the scope of this document.
4. Advertise the Group Best Paths 4. Advertise the Group Best Paths
The term neighbor-AS for a route refers to the neighboring AS from The term neighbor-AS for a route refers to the neighboring AS from
which the route was received. The calculation of the neighbor-AS is which the route was received. The calculation of the neighbor-AS is
specified in Sect. 9.1.2.2 of [RFC4271], and Section 7.2 of specified in Section 9.1.2.2 of [RFC4271], and Section 7.2 of
[RFC5065]. By definition the MED is comparable only among routes [RFC5065]. By definition the MED is comparable only among routes
with the same neighbor-AS. Thus the route selection procedures with the same neighbor-AS. Thus the route selection procedures
specified in [RFC4271] would conceptually involve two steps: first specified in [RFC4271] would conceptually involve two steps: first
organize the paths for an address prefix into groups according to organize the paths for an address prefix into groups according to
their respective neighbor-AS's, and calculate the most preferred one their respective neighbor-AS's, and calculate the most preferred one
(termed "Group Best Path") for each of the groups; Then calculate the (termed "Group Best Path") for each of the groups; Then calculate the
overall best path among all the Group Best Paths. overall best path among all the Group Best Paths.
As a generally recommended ([RFC4456], [RFC5065]) and widely adopted As a generally recommended ([RFC4456], [RFC5065]) and widely adopted
practice, a route reflection cluster or a confederation sub-AS should practice, a route reflection cluster or a confederation sub-AS should
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To allow a route reflector or a confederation ASBR to advertise To allow a route reflector or a confederation ASBR to advertise
either the Available Paths or Group Best Paths using the mechanism either the Available Paths or Group Best Paths using the mechanism
described in ADD-PATH [I-D.ietf-idr-add-paths], the following described in ADD-PATH [I-D.ietf-idr-add-paths], the following
revisions are proposed for BGP route reflection and BGP revisions are proposed for BGP route reflection and BGP
Confederation. Confederation.
5.1. Route Reflection 5.1. Route Reflection
Depending on the configuration, for a particular <AFI, SAFI> a route Depending on the configuration, for a particular <AFI, SAFI> a route
reflector SHOULD include the <AFI, SAFI> with the "Send/Receive" reflector SHOULD include the <AFI, SAFI> with the "Send/Receive"
field set to 2 or 3 in the ADD-PATH Capability field set to 2 (send multiple paths) or 3 (send/receive multiple
[I-D.ietf-idr-add-paths] advertised to an IBGP peer. When the ADD- paths) in the ADD-PATH Capability [I-D.ietf-idr-add-paths] advertised
PATH Capability is also received from the IBGP peer with the "Send/ to an IBGP peer. When the ADD-PATH Capability is also received from
Receive" field set to 1 or 3 for the same <AFI, SAFI>, then the the IBGP peer with the "Send/Receive" field set to 1 (receive
following procedures shall be followed: multiple paths) or 3 (send/receive multiple paths) for the same <AFI,
SAFI>, then the following procedures shall be followed:
If the peer is a route reflection client, the route reflector SHOULD If the peer is a route reflection client, the route reflector SHOULD
advertise to the peer the Group Best Paths (or the Available Paths) advertise to the peer the Group Best Paths (or the Available Paths)
received from its non-client IBGP peers. Depending on the received from its non-client IBGP peers. Depending on the
configuration, the route reflector MAY also advertise to the peer the configuration, the route reflector MAY also advertise to the peer the
Group Best Paths (or the Available Paths) received from its clients. Group Best Paths (or the Available Paths) received from its clients.
If the peer is a non-client, the route reflector SHOULD advertise to If the peer is a non-client, the route reflector SHOULD advertise to
the peer the Group Best Paths (or the Available Paths) received from the peer the Group Best Paths (or the Available Paths) received from
its clients. its clients.
5.2. Confederation 5.2. Confederation
Depending on the configuration, for a particular <AFI, SAFI> a Depending on the configuration, for a particular <AFI, SAFI> a
confederation ASBR SHOULD include the <AFI, SAFI> with the "Send/ confederation ASBR SHOULD include the <AFI, SAFI> with the "Send/
Receive" field set to 2 or 3 in the ADD-PATH Capability Receive" field set to 2 (send multiple paths) or 3 (send/receive
[I-D.ietf-idr-add-paths] advertised to an IBGP peer, and to a multiple paths) in the ADD-PATH Capability [I-D.ietf-idr-add-paths]
confederation external peer. When the ADD-PATH Capability is also advertised to an IBGP peer, and to a confederation external peer.
received from the IBGP peer or the confederation external peer with When the ADD-PATH Capability is also received from the IBGP peer or
the "Send/Receive" field set to 1 or 3 for the same <AFI, SAFI>, then the confederation external peer with the "Send/Receive" field set to
the following procedures shall be followed: 1 (receive multiple paths) or 3 (send/receive multiple paths) for the
same <AFI, SAFI>, then the following procedures shall be followed:
If the peer is internal, the confederation ASBR SHOULD advertise to If the peer is internal, the confederation ASBR SHOULD advertise to
the peer the Group Best Paths (or the Available Paths) received from the peer the Group Best Paths (or the Available Paths) received from
its confederation external peers. its confederation external peers.
If the peer is confederation external, the confederation ASBR SHOULD If the peer is confederation external, the confederation ASBR SHOULD
advertise to the peer the Group Best Paths (or the Available Paths) advertise to the peer the Group Best Paths (or the Available Paths)
received from its IBGP peers. received from its IBGP peers.
6. Deployment Considerations 6. Deployment Considerations
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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 solutions. contributions to the design and development of the solutions.
10. References 10. References
10.1. Normative References 10.1. Normative References
[I-D.ietf-idr-add-paths] [I-D.ietf-idr-add-paths]
Walton, D., Retana, A., Chen, E., and J. Scudder, Walton, D., Retana, A., Chen, E., and J. Scudder,
"Advertisement of Multiple Paths in BGP", draft-ietf-idr- "Advertisement of Multiple Paths in BGP", draft-ietf-idr-
add-paths-10 (work in progress), October 2014. add-paths-13 (work in progress), December 2015.
[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, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>. <http://www.rfc-editor.org/info/rfc2119>.
[RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A [RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A
Border Gateway Protocol 4 (BGP-4)", RFC 4271, Border Gateway Protocol 4 (BGP-4)", RFC 4271,
DOI 10.17487/RFC4271, January 2006, DOI 10.17487/RFC4271, January 2006,
<http://www.rfc-editor.org/info/rfc4271>. <http://www.rfc-editor.org/info/rfc4271>.
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