< draft-ietf-dots-multihoming-09.txt		draft-ietf-dots-multihoming-10.txt >
	Network Working Group M. Boucadair		Network Working Group M. Boucadair
	Internet-Draft Orange		Internet-Draft Orange
	Intended status: Informational T. Reddy		Intended status: Informational T. Reddy
	Expires: 5 June 2022 McAfee		Expires: 8 July 2022 McAfee
	W. Pan		W. Pan
	Huawei Technologies		Huawei Technologies
	2 December 2021		4 January 2022
	Multi-homing Deployment Considerations for Distributed-Denial-of-Service		Multi-homing Deployment Considerations for Distributed-Denial-of-Service
	Open Threat Signaling (DOTS)		Open Threat Signaling (DOTS)
	draft-ietf-dots-multihoming-09		draft-ietf-dots-multihoming-10
	Abstract		Abstract
	This document discusses multi-homing considerations for Distributed-		This document discusses multi-homing considerations for Distributed-
	Denial-of-Service Open Threat Signaling (DOTS). The goal is to		Denial-of-Service Open Threat Signaling (DOTS). The goal is to
	provide some guidance for DOTS clients/gateways when multihomed.		provide some guidance for DOTS clients and client-domain DOTS
			gateways when multihomed.
	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 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 5 June 2022.		This Internet-Draft will expire on 8 July 2022.
	Copyright Notice		Copyright Notice
	Copyright (c) 2021 IETF Trust and the persons identified as the		Copyright (c) 2022 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 (https://trustee.ietf.org/		Provisions Relating to IETF Documents (https://trustee.ietf.org/
	license-info) in effect on the date of publication of this document.		license-info) in effect on the date of publication of this document.
	Please review these documents carefully, as they describe your rights		Please review these documents carefully, as they describe your rights
	and restrictions with respect to this document. Code Components		and restrictions with respect to this document. Code Components
	extracted from this document must include Revised BSD License text as		extracted from this document must include Revised BSD License text as
	described in Section 4.e of the Trust Legal Provisions and are		described in Section 4.e of the Trust Legal Provisions and are
	provided without warranty as described in the Revised BSD License.		provided without warranty as described in the Revised BSD License.
	skipping to change at page 4, line 25 ¶		skipping to change at page 4, line 25 ¶
	* Augment the description with multi-homing technicalities, e.g.,		* Augment the description with multi-homing technicalities, e.g.,
	- One vs. multiple upstream network providers		- One vs. multiple upstream network providers
	- One vs. multiple interconnect routers		- One vs. multiple interconnect routers
	- Provider-Independent (PI) vs. Provider-Aggregatable (PA) IP		- Provider-Independent (PI) vs. Provider-Aggregatable (PA) IP
	addresses		addresses
	* Describe the recommended behavior of DOTS clients and gateways for		* Describe the recommended behavior of DOTS clients and client-
	each case.		domain DOTS gateways for each case.
	Multi-homed DOTS agents are assumed to make use of the protocols		Multi-homed DOTS agents are assumed to make use of the protocols
	defined in [RFC9132] and [RFC8783]; no specific extension is required		defined in [RFC9132] and [RFC8783]; no specific extension is required
	to the base DOTS protocols for deploying DOTS in a multi-homed		to the base DOTS protocols for deploying DOTS in a multi-homed
	context.		context.
	2. Requirements Language		2. 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", "NOT RECOMMENDED", "MAY", and		"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
	skipping to change at page 8, line 11 ¶		skipping to change at page 8, line 11 ¶
	This scenario is a variant of Section 4.2 and Section 4.3 in which		This scenario is a variant of Section 4.2 and Section 4.3 in which
	multi-homing is supported by the same ISP (i.e., same provisioning		multi-homing is supported by the same ISP (i.e., same provisioning
	domain).		domain).
	5. DOTS Multi-homing Deployment Considerations		5. DOTS Multi-homing Deployment Considerations
	Table 1 provides some sample, non-exhaustive, deployment schemes to		Table 1 provides some sample, non-exhaustive, deployment schemes to
	illustrate how DOTS agents may be deployed for each of the scenarios		illustrate how DOTS agents may be deployed for each of the scenarios
	introduced in Section 4.		introduced in Section 4.
	+============================+=======================+==============+		+=========================+=======================+===============+
	| Scenario | DOTS client | DOTS |		| Scenario | DOTS client | Client-domain |
	| | | gateway |		| | | DOTS gateway |
	+============================+=======================+==============+		+=========================+=======================+===============+
	| Residential CPE | CPE | N/A |		| Residential CPE | CPE | N/A |
	+----------------------------+-----------------------+--------------+		+-------------------------+-----------------------+---------------+
	| Single CPE, Multiple | Internal hosts or CPE | CPE |		| Single CPE, Multiple | Internal hosts or CPE | CPE |
	| provisioning domains | | |		| provisioning domains | | |
	+----------------------------+-----------------------+--------------+		+-------------------------+-----------------------+---------------+
	| Multiple CPEs, Multiple | Internal hosts or all | CPEs (rtr1 |		| Multiple CPEs, Multiple | Internal hosts or all | CPEs (rtr1 |
	| provisioning domains | CPEs (rtr1 and rtr2) | and rtr2) |		| provisioning domains | CPEs (rtr1 and rtr2) | and rtr2) |
	+----------------------------+-----------------------+--------------+		+-------------------------+-----------------------+---------------+
	| Multi-homed enterprise, | Internal hosts or all | CPEs (rtr1 |		| Multi-homed enterprise, | Internal hosts or all | CPEs (rtr1 |
	| Single provisioning domain | CPEs (rtr1 and rtr2) | and rtr2) |		| Single provisioning | CPEs (rtr1 and rtr2) | and rtr2) |
	+----------------------------+-----------------------+--------------+		| domain | | |
			+-------------------------+-----------------------+---------------+
	Table 1: Sample Deployment Cases		Table 1: Sample Deployment Cases
	These deployment schemes are further discussed in the following		These deployment schemes are further discussed in the following
	subsections.		subsections.
	5.1. Residential CPE		5.1. Residential CPE
	Figure 5 depicts DOTS sessions that need to be established between a		Figure 5 depicts DOTS sessions that need to be established between a
	DOTS client (C) and two DOTS servers (S1, S2) within the context of		DOTS client (C) and two DOTS servers (S1, S2) within the context of
	skipping to change at page 10, line 7 ¶		skipping to change at page 10, line 7 ¶
	\		\
	\ +--+		\ +--+
	----------|S2|		----------|S2|
	+--+		+--+
	DOTS Server Domain #2		DOTS Server Domain #2
	Figure 5: DOTS Associations for a Multihomed Residential CPE		Figure 5: DOTS Associations for a Multihomed Residential CPE
	5.2. Multi-Homed Enterprise: Single CPE, Multiple Upstream ISPs		5.2. Multi-Homed Enterprise: Single CPE, Multiple Upstream ISPs
	Figure 6 illustrates a first set of DOTS associations that can be		Figure 6 illustrates a first set of DOTS sessions that can be
	established with a DOTS gateway, which is enabled within the context		established with a client-domain DOTS gateway, which is enabled
	of the scenario described in Section 4.2. This deployment is		within the context of the scenario described in Section 4.2. This
	characterized as follows:		deployment is characterized as follows:
	* One of more DOTS clients are enabled in hosts located in the		* One of more DOTS clients are enabled in hosts located in the
	internal network.		internal network.
	* A DOTS gateway is enabled to aggregate and then relay the requests		* A client-domain DOTS gateway is enabled to aggregate and then
	towards upstream DOTS servers.		relay the requests towards upstream DOTS servers.
	+--+		+--+
	----------|S1|		----------|S1|
	+---+ / +--+		+---+ / +--+
	| C1|----+ / DOTS Server Domain #1		| C1|----+ / DOTS Server Domain #1
	+---+ | /		+---+ | /
	+---+ +-+-+/		+---+ +-+-+/
	| C3|------| G |		| C3|------| G |
	+---+ +-+-+\		+---+ +-+-+\
	+---+ | \		+---+ | \
	| C2|----+ \		| C2|----+ \
	+---+ \ +--+		+---+ \ +--+
	----------|S2|		----------|S2|
	+--+		+--+
	DOTS Server Domain #2		DOTS Server Domain #2
	Figure 6: Multiple DOTS Clients, Single DOTS Gateway, Multiple		Figure 6: Multiple DOTS Clients, Single DOTS Gateway, Multiple
	DOTS Servers		DOTS Servers
	When PA addresses/prefixes are in use, the same considerations		When PA addresses/prefixes are in use, the same considerations
	discussed in Section 5.1 need to be followed by the DOTS gateway to		discussed in Section 5.1 need to be followed by the client-domain
	contact its DOTS server(s). The DOTS gateways can be reachable from		DOTS gateway to contact its DOTS server(s). The client-domain DOTS
	DOTS clients by using an unicast address or an anycast address.		gateways can be reachable from DOTS clients by using an unicast
			address or an anycast address (Section 3.2.4 of [RFC8811]).
	Nevertheless, when PI addresses/prefixes are assigned, the DOTS		Nevertheless, when PI addresses/prefixes are assigned and absent any
	gateway MUST send mitigation requests to all its DOTS servers.		policy, the client-domain DOTS gateway MUST send mitigation requests
	Otherwise, the attack traffic may still be delivered via the ISP		to all its DOTS servers. Otherwise, the attack traffic may still be
	which hasn't received the mitigation request.		delivered via the ISP which hasn't received the mitigation request.
	An alternate deployment model is depicted in Figure 7. This		An alternate deployment model is depicted in Figure 7. This
	deployment assumes that:		deployment assumes that:
	* One or more DOTS clients are enabled in hosts located in the		* One or more DOTS clients are enabled in hosts located in the
	internal network. These DOTS clients may use [RFC8973] to		internal network. These DOTS clients may use [RFC8973] to
	discover their DOTS server(s).		discover their DOTS server(s).
	* These DOTS clients communicate directly with upstream DOTS		* These DOTS clients communicate directly with upstream DOTS
	servers.		servers.
	skipping to change at page 11, line 28 ¶		skipping to change at page 11, line 28 ¶
	+--------|C2|--------+		+--------|C2|--------+
	. +--+ .		. +--+ .
	..........		..........
	DOTS Client		DOTS Client
	Domain		Domain
	Figure 7: Multiple DOTS Clients, Multiple DOTS Servers		Figure 7: Multiple DOTS Clients, Multiple DOTS Servers
	If PI addresses/prefixes are in use, the DOTS client MUST send a		If PI addresses/prefixes are in use, the DOTS client MUST send a
	mitigation request to all the DOTS servers. The use of anycast		mitigation request to all the DOTS servers. The use of anycast
	addresses to reach the DOTS servers is NOT RECOMMENDED. If anycast		addresses to reach these DOTS servers is NOT RECOMMENDED. If a well-
	addresses are used to reach multiple DOTS servers, the CPE may not be		known anycast address is used to reach multiple DOTS servers, the CPE
	able to select the appropriate provisioning domain to which the		may not be able to select the appropriate provisioning domain to
	mitigation request should be forwarded. As a consequence, the		which the mitigation request should be forwarded. As a consequence,
	request may not be forwarded to the appropriate DOTS server.		the request may not be forwarded to the appropriate DOTS server.
	If PA addresses/prefixes are used, the same considerations discussed		If PA addresses/prefixes are used, the same considerations discussed
	in Section 5.1 need to be followed by the DOTS clients. Because DOTS		in Section 5.1 need to be followed by the DOTS clients. Because DOTS
	clients are not embedded in the CPE and multiple addreses/prefixes		clients are not embedded in the CPE and multiple addreses/prefixes
	may not be assigned to the DOTS client (typically in an IPv4		may not be assigned to the DOTS client (typically in an IPv4
	context), some issues may arise in how to steer traffic towards the		context), some issues may arise in how to steer traffic towards the
	appropriate DOTS server by using the appropriate source IP address.		appropriate DOTS server by using the appropriate source IP address.
	These complications discussed in [RFC4116] are not specific to DOTS.		These complications discussed in [RFC4116] are not specific to DOTS.
	Another deployment approach is to enable many DOTS clients; each of		Another deployment approach is to enable many DOTS clients; each of
	skipping to change at page 12, line 38 ¶		skipping to change at page 12, line 38 ¶
	The deployments depicted in Figures 7 and 8 also apply to the		The deployments depicted in Figures 7 and 8 also apply to the
	scenario described in Section 4.3. One specific problem for this		scenario described in Section 4.3. One specific problem for this
	scenario is to select the appropriate exit router when contacting a		scenario is to select the appropriate exit router when contacting a
	given DOTS server.		given DOTS server.
	An alternative deployment scheme is shown in Figure 9:		An alternative deployment scheme is shown in Figure 9:
	* DOTS clients are enabled in hosts located in the internal network.		* DOTS clients are enabled in hosts located in the internal network.
	* A DOTS gateway is enabled in each CPE (rtr1, rtr2).		* A client-domain DOTS gateway is enabled in each CPE (rtr1, rtr2).
	* Each of these DOTS gateways communicates with the DOTS server of		* Each of these client-domain DOTS gateways communicates with the
	the provisioning domain.		DOTS server of the provisioning domain.
	+---+		+---+
	+------------| C1|----+		+------------| C1|----+
	| +---+ |		| +---+ |
	+--+ +-+-+ +---+ +-+-+ +--+		+--+ +-+-+ +---+ +-+-+ +--+
	|S2|------|G2 |------| C3|------|G1 |------|S1|		|S2|------|G2 |------| C3|------|G1 |------|S1|
	+--+ +-+-+ +---+ +-+-+ +--+		+--+ +-+-+ +---+ +-+-+ +--+
	| +---+ |		| +---+ |
	+------------| C2|----+		+------------| C2|----+
	+---+		+---+
	Figure 9: Multiple DOTS Clients, Multiple DOTS Gateways, Multiple		Figure 9: Multiple DOTS Clients, Multiple DOTS Gateways, Multiple
	DOTS Servers		DOTS Servers
	When PI addresses/prefixes are used, DOTS clients MUST contact all		When PI addresses/prefixes are used, DOTS clients MUST contact all
	the DOTS gateways to send a DOTS message. DOTS gateways will then		the client-domain DOTS gateways to send a DOTS message. Client-
	relay the request to the DOTS servers. Note that anycast addresses		domain DOTS gateways will then relay the request to the DOTS servers
	cannot be used to establish DOTS sessions between DOTS clients and		as a function of local policy. Note that anycast addresses cannot be
	DOTS gateways because only one DOTS gateway will receive the		used to establish DOTS sessions between DOTS clients and client-
			domain DOTS gateways because only one DOTS gateway will receive the
	mitigation request.		mitigation request.
	When PA addresses/prefixes are used, but no filter rules are provided		When PA addresses/prefixes are used, but no filter rules are provided
	to DOTS clients, the latter MUST contact all DOTS gateways		to DOTS clients, the latter MUST contact all client-domain DOTS
	simultaneously to send a DOTS message. Upon receipt of a request by		gateways simultaneously to send a DOTS message. Upon receipt of a
	a DOTS gateway, it MUST check whether the request is to be forwarded		request by a client-domain DOTS gateway, it MUST check whether the
	upstream (if the target IP prefix is managed by the upstream server)		request is to be forwarded upstream (if the target IP prefix is
	or rejected.		managed by the upstream server) or rejected.
	When PA addresses/prefixes are used, but specific filter rules are		When PA addresses/prefixes are used, but specific filter rules are
	provided to DOTS clients using some means that are out of scope of		provided to DOTS clients using some means that are out of scope of
	this document, the clients MUST select the appropriate DOTS gateway		this document, the clients MUST select the appropriate client-domain
	to reach. The use of anycast addresses is NOT RECOMMENDED to reach		DOTS gateway to reach. The use of anycast addresses is NOT
	DOTS gateways.		RECOMMENDED to reach client-domain DOTS gateways.
	5.4. Multi-Homed Enterprise: Single ISP		5.4. Multi-Homed Enterprise: Single ISP
	The key difference of the scenario described in Section 4.4 compared		The key difference of the scenario described in Section 4.4 compared
	to the other scenarios is that multi-homing is provided by the same		to the other scenarios is that multi-homing is provided by the same
	ISP. Concretely, that ISP can decide to provision the enterprise		ISP. Concretely, that ISP can decide to provision the enterprise
	network with:		network with:
	* The same DOTS server for all network attachments.		* The same DOTS server for all network attachments.
	skipping to change at page 14, line 7 ¶		skipping to change at page 14, line 7 ¶
	decide to select one or all network attachments to send DOTS		decide to select one or all network attachments to send DOTS
	mitigation requests.		mitigation requests.
	6. Security Considerations		6. Security Considerations
	DOTS-related security considerations are discussed in Section 4 of		DOTS-related security considerations are discussed in Section 4 of
	[RFC8811].		[RFC8811].
	DOTS clients should control the information that they share with peer		DOTS clients should control the information that they share with peer
	DOTS servers. In particular, if a DOTS client maintains DOTS		DOTS servers. In particular, if a DOTS client maintains DOTS
	associations with specific DOTS servers per interconnection link, the		sessions with specific DOTS servers per interconnection link, the
	DOTS client SHOULD NOT leak information specific to a given link to		DOTS client SHOULD NOT leak information specific to a given link to
	DOTS servers on different interconnection links that are not		DOTS servers on different interconnection links that are not
	authorized to mitigate attacks for that given link. Whether this		authorized to mitigate attacks for that given link. Whether this
	constraint is relaxed is deployment-specific and must be subject to		constraint is relaxed is deployment-specific and must be subject to
	explicit consent from the DOTS client domain administrator. How to		explicit consent from the DOTS client domain administrator. How to
	seek for such consent is implementation- and deployment-specific.		seek for such consent is implementation- and deployment-specific.
	7. IANA Considerations		7. IANA Considerations
	This document does not require any action from IANA.		This document does not require any action from IANA.
	8. Acknowledgements		8. Acknowledgements
	Thanks to Roland Dobbins, Nik Teague, Jon Shallow, Dan Wing, and		Thanks to Roland Dobbins, Nik Teague, Jon Shallow, Dan Wing, and
	Christian Jacquenet for sharing their comments on the mailing list.		Christian Jacquenet for sharing their comments on the mailing list.
	Thanks to Kirill Kasavchenko for the comments.		Thanks to Kirill Kasavchenko for the comments.
			Thanks to Kathleen Moriarty for the secdir review and Joel Jaeggli
			for the opsdir review.
	9. References		9. References
	9.1. Normative References		9.1. 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,		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>.
	[RFC6724] Thaler, D., Ed., Draves, R., Matsumoto, A., and T. Chown,		[RFC6724] Thaler, D., Ed., Draves, R., Matsumoto, A., and T. Chown,
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