draft-ietf-grow-wkc-behavior-01.txt   draft-ietf-grow-wkc-behavior-02.txt 
Network Working Group J. Borkenhagen Network Working Group J. Borkenhagen
Internet-Draft AT&T Internet-Draft AT&T
Intended status: Standards Track R. Bush Intended status: Standards Track R. Bush
Expires: July 11, 2019 Internet Initiative Japan Expires: July 26, 2019 Internet Initiative Japan
R. Bonica R. Bonica
Juniper Networks Juniper Networks
S. Bayraktar S. Bayraktar
Cisco Systems Cisco Systems
January 7, 2019 January 22, 2019
Well-Known Community Policy Behavior Well-Known Community Policy Behavior
draft-ietf-grow-wkc-behavior-01 draft-ietf-grow-wkc-behavior-02
Abstract Abstract
Well-Known BGP Communities are manipulated inconsistently by current Well-Known BGP Communities are manipulated inconsistently by current
implementations. This results in difficulties for operators. implementations. This results in difficulties for operators.
Network operators are encouraged to deploy consistent community Network operators are encouraged to deploy consistent community
handling across their networks, taking the inconsistent behaviors handling across their networks, taking the inconsistent behaviors
from the various bgp implementations they operate into consideration. from the various bgp implementations they operate into consideration.
Also, bgp implementors are expected to not create any further Also, bgp implementors are expected to not create any further
inconsistencies from this point forward. inconsistencies from this point forward.
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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 https://datatracker.ietf.org/drafts/current/. Drafts is at https://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 July 11, 2019. This Internet-Draft will expire on July 26, 2019.
Copyright Notice Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the Copyright (c) 2019 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
(https://trustee.ietf.org/license-info) in effect on the date of (https://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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communities when modified using the syntax to "set" the community. communities when modified using the syntax to "set" the community.
Some replace all communities including the Well-Known ones with the Some replace all communities including the Well-Known ones with the
new set, while others replace all non-Well-Known Communities but do new set, while others replace all non-Well-Known Communities but do
not modify any Well-Known Communities that are present. not modify any Well-Known Communities that are present.
These differences result in what would appear to be identical policy These differences result in what would appear to be identical policy
configurations having very different results on different platforms. configurations having very different results on different platforms.
4. Documentation of Vendor Implementations 4. Documentation of Vendor Implementations
In this section we document the syntax and observed behavior of the
"set" directive in several popular bgp implementations.
In Juniper Networks' JunOS, "community set" removes all received In Juniper Networks' JunOS, "community set" removes all received
communities, Well-Known or otherwise. communities, Well-Known or otherwise.
In Cisco Systems' IOS-XR, "set community" removes all received In Cisco Systems' IOS-XR, "set community" removes all received
communities except for the following: communities except for the following:
+-------------+-----------------------------------+ +-------------+-----------------------------------+
| Numeric | Common Name | | Numeric | Common Name |
+-------------+-----------------------------------+ +-------------+-----------------------------------+
| 0:0 | internet | | 0:0 | internet |
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Care should be taken when establishing new [RFC1997]-like attributes Care should be taken when establishing new [RFC1997]-like attributes
(large communities, wide communities, etc) to avoid repeating this (large communities, wide communities, etc) to avoid repeating this
mistake. mistake.
6. Action Items 6. Action Items
Unfortunately, it would be operationally disruptive for vendors to Unfortunately, it would be operationally disruptive for vendors to
change their current implementations. change their current implementations.
Vendors SHOULD share the behavior of their implementations for Vendors SHOULD clearly document the behavior of "set" directive in
inclusion in this document, especially if their behavior differs from their implementations.
the examples described.
Vendors MUST ensure that any well-known communities specified after Vendors MUST ensure that any Well-Known Communities specified after
this document's publication are removed by the "community set" this document's publication are removed by their "set" directive.
action.
Given the implementation inconsistencies described in this document, Given the implementation inconsistencies described in this document,
network operators are urged never to rely on any implicit network operators are urged never to rely on any implicit
understanding of a neighbor ASN's bgp community handling. I.e., understanding of a neighbor ASN's bgp community handling. I.e.,
before announcing prefixes with NO_EXPORT or any other community to a before announcing prefixes with NO_EXPORT or any other community to a
neighbor ASN, the operator should confirm with that neighbor how the neighbor ASN, the operator should confirm with that neighbor how the
community will be treated. community will be treated.
Network operators are encouraged to limit their use of the "set"
directive (within reason), to improve the readability of their
configurations and hopefully to achieve behavioral consistency across
platforms.
7. Security Considerations 7. Security Considerations
Surprising defaults and/or undocumented behaviors are not good for Surprising defaults and/or undocumented behaviors are not good for
security. This document attempts to remedy that. security. This document attempts to remedy that.
8. IANA Considerations 8. IANA Considerations
This document has no IANA Considerations other than to be aware that This document has no IANA Considerations other than to be aware that
any future Well-Known Communities will be subject to the policy any future Well-Known Communities will be subject to the policy
treatment described here. treatment described here.
9. Acknowledgements 9. Acknowledgements
The authors thank Martijn Schmidt for his contribution, Qin Wu for The authors thank Martijn Schmidt, Qin Wu for the Huawei data point,
the Huawei data point. Job Snijders, David Farmer,John Heasley, and Jakob Heitz.
10. Normative References 10. Normative References
[IANA-WKS] [IANA-WKS]
"IANA Well-Known Comunities", "IANA Well-Known Comunities",
<https://www.iana.org/assignments/bgp-well-known- <https://www.iana.org/assignments/bgp-well-known-
communities/bgp-well-known-communities.xhtml>. communities/bgp-well-known-communities.xhtml>.
[RFC1997] Chandra, R., Traina, P., and T. Li, "BGP Communities [RFC1997] Chandra, R., Traina, P., and T. Li, "BGP Communities
Attribute", RFC 1997, DOI 10.17487/RFC1997, August 1996, Attribute", RFC 1997, DOI 10.17487/RFC1997, August 1996,
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