draft-ietf-idr-bgp-flowspec-oid-10.txt		draft-ietf-idr-bgp-flowspec-oid-11.txt
	Network Working Group J. Uttaro		Network Working Group J. Uttaro
	Internet-Draft AT&T		Internet-Draft AT&T
	Updates: 5575bis (if approved) J. Alcaide		Updates: 5575bis (if approved) J. Alcaide
	Intended status: Standards Track C. Filsfils		Intended status: Standards Track C. Filsfils
	Expires: February 9, 2020 D. Smith		Expires: September 9, 2020 D. Smith
	Cisco		Cisco
	P. Mohapatra		P. Mohapatra
	Sproute Networks		Sproute Networks
	August 8, 2019		March 8, 2020
	Revised Validation Procedure for BGP Flow Specifications		Revised Validation Procedure for BGP Flow Specifications
	draft-ietf-idr-bgp-flowspec-oid-10		draft-ietf-idr-bgp-flowspec-oid-11
	Abstract		Abstract
	This document describes a modification to the validation procedure		This document describes a modification to the validation procedure
	defined in [RFC5575bis] for the dissemination of BGP Flow		defined in [RFC5575bis] for the dissemination of BGP Flow
	Specifications. [RFC5575bis] requires that the originator of the		Specifications. [RFC5575bis] requires that the originator of the
	Flow Specification matches the originator of the best-match unicast		Flow Specification matches the originator of the best-match unicast
	route for the destination prefix embedded in the Flow Specification.		route for the destination prefix embedded in the Flow Specification.
	This allows only BGP speakers within the data forwarding path (such		This allows only BGP speakers within the data forwarding path (such
	as autonomous system border routers) to originate BGP Flow		as autonomous system border routers) to originate BGP Flow
	skipping to change at page 1, line 47 ¶		skipping to change at page 1, line 47 ¶
	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 February 9, 2020.		This Internet-Draft will expire on September 9, 2020.
	Copyright Notice		Copyright Notice
	Copyright (c) 2019 IETF Trust and the persons identified as the		Copyright (c) 2020 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
	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
	skipping to change at page 2, line 32 ¶		skipping to change at page 2, line 32 ¶
	1. Requirements Language . . . . . . . . . . . . . . . . . . . . 2		1. Requirements Language . . . . . . . . . . . . . . . . . . . . 2
	2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2		2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
	3. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . 3		3. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . 3
	4. Revised Validation Procedure . . . . . . . . . . . . . . . . 5		4. Revised Validation Procedure . . . . . . . . . . . . . . . . 5
	4.1. Revision of Route Feasibility . . . . . . . . . . . . . . 5		4.1. Revision of Route Feasibility . . . . . . . . . . . . . . 5
	4.2. Revision of AS_PATH Validation . . . . . . . . . . . . . 6		4.2. Revision of AS_PATH Validation . . . . . . . . . . . . . 6
	5. Other RFC5575bis Considerations . . . . . . . . . . . . . . . 7		5. Other RFC5575bis Considerations . . . . . . . . . . . . . . . 7
	6. Topology Considerations . . . . . . . . . . . . . . . . . . . 8		6. Topology Considerations . . . . . . . . . . . . . . . . . . . 8
	7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9		7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
	8. Security Considerations . . . . . . . . . . . . . . . . . . . 9		8. Security Considerations . . . . . . . . . . . . . . . . . . . 9
	9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 10		9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9
	10. Normative References . . . . . . . . . . . . . . . . . . . . 10		10. Normative References . . . . . . . . . . . . . . . . . . . . 9
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11		Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
	1. Requirements Language		1. Requirements Language
	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 RFC 2119 [RFC2119].		document are to be interpreted as described in RFC 2119 [RFC2119].
	2. Introduction		2. Introduction
	[RFC5575bis] defined a new BGP [RFC4271] capability that can be used		[RFC5575bis] defined a new BGP [RFC4271] capability that can be used
	skipping to change at page 3, line 33 ¶		skipping to change at page 3, line 33 ¶
	modification cannot be used for inter-domain coordination of traffic		modification cannot be used for inter-domain coordination of traffic
	filtering, it greatly simplifies distribution of intra-domain traffic		filtering, it greatly simplifies distribution of intra-domain traffic
	filtering policies within an autonomous system which has a large		filtering policies within an autonomous system which has a large
	number of border routers having complex BGP policies. By relaxing		number of border routers having complex BGP policies. By relaxing
	the validation procedure for iBGP, the proposed modification allows		the validation procedure for iBGP, the proposed modification allows
	Flow Specifications to be distributed in a standard and scalable		Flow Specifications to be distributed in a standard and scalable
	manner throughout an autonomous system.		manner throughout an autonomous system.
	3. Motivation		3. Motivation
	Step (a) of the validation procedure in [RFC5575bis], section 6 is		Step (b) of the validation procedure in [RFC5575bis], section 6 is
	defined with the underlying assumption that the Flow Specification		defined with the underlying assumption that the Flow Specification
	NLRI traverses the same path, in the inter-domain and intra-domain		NLRI traverses the same path, in the inter-domain and intra-domain
	route distribution graph, as that of the longest-match unicast route		route distribution graph, as that of the longest-match unicast route
	for the destination prefix embedded in the Flow Specification.		for the destination prefix embedded in the Flow Specification.
	In the case of inter-domain traffic filtering, the Flow Specification		In the case of inter-domain traffic filtering, the Flow Specification
	originator at the egress border routers of an AS (e.g. RTR-D and		originator at the egress border routers of an AS (e.g. RTR-D and
	RTR-E of ASN1 in figure 1) matches the eBGP neighbor that advertised		RTR-E of ASN1 in figure 1) matches the eBGP neighbor that advertised
	the longest match destination prefix (see RTR-F and RTR-G		the longest match destination prefix (see RTR-F and RTR-G
	respectively in figure 1). Similarly, at the ingress border routers		respectively in figure 1). Similarly, at the ingress border routers
	skipping to change at page 5, line 16 ¶		skipping to change at page 5, line 16 ¶
	plane. In this way, operators can direct border routers within their		plane. In this way, operators can direct border routers within their
	ASN with specific attack mitigation actions (drop the traffic,		ASN with specific attack mitigation actions (drop the traffic,
	forward to a clean-pipe center, etc.).		forward to a clean-pipe center, etc.).
	To originate a Flow Specification NLRI, a central BGP route		To originate a Flow Specification NLRI, a central BGP route
	controller must set itself as the originator in the Flow		controller must set itself as the originator in the Flow
	Specification NLRI. This is necessary given the route controller is		Specification NLRI. This is necessary given the route controller is
	originating the Flow Specification rather than reflecting it, and to		originating the Flow Specification rather than reflecting it, and to
	avoid the complexity of having to determine the egress border router		avoid the complexity of having to determine the egress border router
	whose path was chosen as the best in each of the ingress border		whose path was chosen as the best in each of the ingress border
	routers. Thus, it is necessary to modify step (a) of the		routers. Thus, it is necessary to modify step (b) of the
	[RFC5575bis] validation procedure such that an iBGP peer that is not		[RFC5575bis] validation procedure such that an iBGP peer that is not
	within the data forwarding plane may originate Flow Specification		within the data forwarding plane may originate Flow Specification
	NLRIs.		NLRIs.
	4. Revised Validation Procedure		4. Revised Validation Procedure
	4.1. Revision of Route Feasibility		4.1. Revision of Route Feasibility
	Step (a) of the validation procedure specified in [RFC5575bis],		Step (b) of the validation procedure specified in [RFC5575bis],
	section 6 is redefined as follows:		section 6 is redefined as follows:
	a. One of the following conditions MUST hold true.		a. One of the following conditions MUST hold true:
	1. The originator of the Flow Specification matches the		1. The originator of the Flow Specification matches the
	originator of the best-match unicast route for the		originator of the best-match unicast route for the
	destination prefix embedded in the Flow Specification.		destination prefix embedded in the Flow Specification (this
			is the unicast route with the longest possible prefix length
			covering the destination prefix embedded in the Flow
			Specification).
	2. The AS_PATH attribute of the Flow Specification does not		2. The AS_PATH attribute of the Flow Specification does not
	contain AS_SET and/or AS_SEQUENCE segments.		contain AS_SET and/or AS_SEQUENCE segments.
	1. This condition SHOULD be enabled by default. This		1. This condition SHOULD be enabled by default. This
	default behavior should validate an empty AS_PATH.		default behavior should validate an empty AS_PATH.
	2. This condition MAY be disabled by configuration on a BGP		2. This condition MAY be disabled by configuration on a BGP
	speaker.		speaker.
	skipping to change at page 6, line 4 ¶		skipping to change at page 6, line 9 ¶
	3. As an exception to this rule, a given AS_PATH with AS_SET		3. As an exception to this rule, a given AS_PATH with AS_SET
	and/or AS_SEQUENCE segments MAY be validated by policy.		and/or AS_SEQUENCE segments MAY be validated by policy.
	Explanation:		Explanation:
	In this context, an empty AS_PATH means that it does not have		In this context, an empty AS_PATH means that it does not have
	AS_SET and/or AS_SEQUENCE segments, and local domain means the		AS_SET and/or AS_SEQUENCE segments, and local domain means the
	local AS [RFC4271] or the local confederation of ASes (in the case		local AS [RFC4271] or the local confederation of ASes (in the case
	that the local AS belongs to a confederation of ASes [RFC5065]).		that the local AS belongs to a confederation of ASes [RFC5065]).
	Thus, receiving a Flow Specification with an empty AS_PATH		Thus, receiving a Flow Specification with an empty AS_PATH
	indicates that the Flow Specification was originated inside the		indicates that the Flow Specification was originated inside the
	local domain.		local domain.
	With the above modification to the [RFC5575bis] validation		With the above modification to the [RFC5575bis] validation
	procedure, a BGP peer within the local domain that is not within		procedure, a BGP peer within the local domain that is not within
	the data forwarding path can originate a Flow Specification.		the data forwarding path can originate a Flow Specification.
	Disabling the new condition above (a.2.2) may be a good practice		Disabling the new condition above (b.2.2) may be a good practice
	when the operator knows with certainty that there is not a Flow		when the operator knows with certainty that there is not a Flow
	Specification originated inside the local domain.		Specification originated inside the local domain.
	Also, policy may be useful to validate a specific set of non-empty		Also, policy may be useful to validate a specific set of non-empty
	AS_PATHs (a.2.3). For example, it could validate a Flow		AS_PATHs (b.2.3). For example, it could validate a Flow
	Specification whose AS_PATH contains only an AS_SEQUENCE with ASes		Specification whose AS_PATH contains only an AS_SEQUENCE with ASes
	that are all known to belong to the same administrative domain.		that are all known to belong to the same administrative domain.
	4.2. Revision of AS_PATH Validation		4.2. Revision of AS_PATH Validation
	[RFC5575bis] states:		[RFC5575bis] states:
	o BGP implementations MUST also enforce that the AS_PATH attribute		o BGP implementations MUST also enforce that the AS_PATH attribute
	of a route received via the External Border Gateway Protocol		of a route received via the External Border Gateway Protocol
	(eBGP) contains the neighboring AS in the left-most position of		(eBGP) contains the neighboring AS in the left-most position of
	skipping to change at page 7, line 38 ¶		skipping to change at page 7, line 43 ¶
	from an External Border Gateway Protocol (eBGP) peer belonging to		from an External Border Gateway Protocol (eBGP) peer belonging to
	the same local domain (in the case that the local AS belongs to a		the same local domain (in the case that the local AS belongs to a
	confederation of ASes) is out of the scope of this document. Note		confederation of ASes) is out of the scope of this document. Note
	that although it's possible, its utility is dubious.		that although it's possible, its utility is dubious.
	5. Other RFC5575bis Considerations		5. Other RFC5575bis Considerations
	This section clarifies some of the terminology and rules referenced		This section clarifies some of the terminology and rules referenced
	in [RFC5575bis]. Namely:		in [RFC5575bis]. Namely:
	o [RFC5575bis] references "the best-match unicast route for the
	destination prefix embedded in the Flow Specification". For
	clarity, this route is defined hereby as the best path of the
	unicast network with the longer prefix-length that covers the
	destination prefix embedded in the Flow Specification.
	Explanation:
	We consider only the best-match network and we do not consider
	unicast non-best paths (even if it is received from the same peer
	as the Flow Specification).
	o If a BGP Flow Specification does not embed a destination prefix
	component, then the default behavior SHOULD be not to perform the
	validation procedures.
	Explanation:
	The reason for this is because the best-match unicast route is not
	defined in this case.
	o In the context of this document and [RFC5575bis], AS_PATH		o In the context of this document and [RFC5575bis], AS_PATH
	attribute is defined as the reconstructed AS path information (by		attribute is defined as the reconstructed AS path information (by
	combining AS_PATH and AS4_PATH attributes, if the BGP speaker is a		combining AS_PATH and AS4_PATH attributes, if the BGP speaker is a
	NEW speaker and receives the route from an OLD speaker), according		NEW speaker and receives the route from an OLD speaker), according
	to section 4.2.3 of [RFC6793].		to section 4.2.3 of [RFC6793].
	o Support for two-octet AS only implementations is out of the scope		o Support for two-octet AS only implementations is out of the scope
	of this document (i.e. it's assumed that the BGP speaker supports		of this document (i.e. it's assumed that the BGP speaker supports
	[RFC6793]).		[RFC6793]).
	6. Topology Considerations		6. Topology Considerations
	[RFC5575bis] indicates that the originator may refer to the		[RFC5575bis] indicates that the originator may refer to the
	originator path attribute (ORIGINATOR_ID) or (if the attribute is not		originator path attribute (ORIGINATOR_ID) or (if the attribute is not
	present) the transport address of the peer from which we received the		present) the transport address of the peer from which we received the
	update. If the latter applies, a network should be designed so it		update. If the latter applies, a network should be designed so it
	has a congruent topology.		has a congruent topology.
	With the additional second condition (a.2) in the validation		With the additional second condition (b.2) in the validation
	procedure, non-congruent topologies are supported within the local		procedure, non-congruent topologies are supported within the local
	domain if the Flow Specification is originated within the local		domain if the Flow Specification is originated within the local
	domain.		domain.
	Explanation:		Explanation:
	Consider the following scenarios without the second condition		Consider the following scenarios without the second condition
	(a.2) being added to the validation procedure:		(b.2) being added to the validation procedure:
	1. Consider a topology with two BGP speakers with two peering		1. Consider a topology with two BGP speakers with two peering
	sessions between them, one for unicast and one for Flow		sessions between them, one for unicast and one for Flow
	Specification. This is a non-congruent topology. Let's		Specification. This is a non-congruent topology. Let's
	assume that the ORIGINATOR_ID attribute was not received (e.g.		assume that the ORIGINATOR_ID attribute was not received (e.g.
	a route reflector receiving routes from its clients). In this		a route reflector receiving routes from its clients). In this
	case, the Flow Specification validation procedure will fail		case, the Flow Specification validation procedure will fail
	because of the first condition (a.1).		because of the first condition (b.1).
	2. Consider a topology with a BGP speaker within a confederation		2. Consider a topology with a BGP speaker within a confederation
	of ASes, inside local AS X. ORIGINATOR_ID attribute is not		of ASes, inside local AS X. ORIGINATOR_ID attribute is not
	advertised within the local domain. Let's assume the Flow		advertised within the local domain. Let's assume the Flow
	Specification route is received from peer A and the best-match		Specification route is received from peer A and the best-match
	unicast route is received from peer B. Both peers belong in		unicast route is received from peer B. Both peers belong in
	local AS Y. Both AS X and AS Y belong to the same local		local AS Y. Both AS X and AS Y belong to the same local
	domain. The Flow Specification validation procedure will also		domain. The Flow Specification validation procedure will also
	fail because of the first condition (a.1).		fail because of the first condition (b.1).
	In the examples above, if Flow Specifications are originated in		In the examples above, if Flow Specifications are originated in
	the same local domain, AS_PATH will not contain AS_SET and/or		the same local domain, AS_PATH will not contain AS_SET and/or
	AS_SEQUENCE segments. When the second condition (a.2) in the		AS_SEQUENCE segments. When the second condition (b.2) in the
	validation procedure is used, the validation procedure will pass.		validation procedure is used, the validation procedure will pass.
	Thus, non-congruent topologies are supported if the Flow		Thus, non-congruent topologies are supported if the Flow
	Specification is originated in the same local domain.		Specification is originated in the same local domain.
	Even when the second condition (a.2) is used in the validation		Even when the second condition (b.2) is used in the validation
	procedure, a Flow Specification originated in a different local		procedure, a Flow Specification originated in a different local
	domain needs a congruent topology. AS_SEQUENCE is not empty and		domain needs a congruent topology. AS_SEQUENCE is not empty and
	the first condition (a.1) in the validation procedure needs to be		the first condition (b.1) in the validation procedure needs to be
	evaluated. Because transport addresses for Flow Specification and		evaluated. Because transport addresses for Flow Specification and
	unicast routes are different, the validation procedure will fail.		unicast routes are different, the validation procedure will fail.
	This is true both across domains and within domains. Consider		This is true both across domains and within domains. Consider
	both cases:		both cases:
	* Consider the first example. If the Flow Specification route is		* Consider the first example. If the Flow Specification route is
	originated in another AS, the validation procedure will fail		originated in another AS, the validation procedure will fail
	because the topology is non-congruent within the domain.		because the topology is non-congruent within the domain.
	* Consider the second example and modify it so AS X and AS Y		* Consider the second example and modify it so AS X and AS Y
	belong to different local domains (no confederation of ASes		belong to different local domains (no confederation of ASes
	exists). The validation procedure will fail because the		exists). The validation procedure will fail because the
	skipping to change at page 10, line 20 ¶		skipping to change at page 10, line 6 ¶
	9. Acknowledgements		9. Acknowledgements
	The authors would like to thank Han Nguyen for his direction on this		The authors would like to thank Han Nguyen for his direction on this
	work as well as Waqas Alam, Keyur Patel, Robert Raszuk, Eric Rosen		work as well as Waqas Alam, Keyur Patel, Robert Raszuk, Eric Rosen
	and Shyam Sethuram for their review comments.		and Shyam Sethuram for their review comments.
	10. Normative References		10. Normative References
	[I-D.ietf-idr-rfc5575bis]		[I-D.ietf-idr-rfc5575bis]
	Hares, S., Loibl, C., Raszuk, R., McPherson, D., and M.		Loibl, C., Hares, S., Raszuk, R., McPherson, D., and M.
	Bacher, "Dissemination of Flow Specification Rules",		Bacher, "Dissemination of Flow Specification Rules",
	draft-ietf-idr-rfc5575bis-14 (work in progress), April		draft-ietf-idr-rfc5575bis-19 (work in progress), January
	2019.		2020.
	[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,
	<https://www.rfc-editor.org/info/rfc2119>.		<https://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,
	<https://www.rfc-editor.org/info/rfc4271>.		<https://www.rfc-editor.org/info/rfc4271>.
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