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.
	skipping to change at page 1, line 49 ¶		skipping to change at page 1, line 49 ¶
	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
	skipping to change at page 3, line 42 ¶		skipping to change at page 3, line 42 ¶
	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 |
	skipping to change at page 5, line 10 ¶		skipping to change at page 5, line 10 ¶
	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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