< draft-ietf-dots-multihoming-05.txt		draft-ietf-dots-multihoming-06.txt >
	Network Working Group M. Boucadair		Network Working Group M. Boucadair
	Internet-Draft Orange		Internet-Draft Orange
	Intended status: Standards Track T. Reddy		Intended status: Standards Track T. Reddy
	Expires: May 27, 2021 McAfee		Expires: November 26, 2021 McAfee
	W. Pan		W. Pan
	Huawei Technologies		Huawei Technologies
	November 23, 2020		May 25, 2021
	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-05		draft-ietf-dots-multihoming-06
	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/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
	skipping to change at page 1, line 36 ¶		skipping to change at page 1, line 36 ¶
	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 May 27, 2021.		This Internet-Draft will expire on November 26, 2021.
	Copyright Notice		Copyright Notice
	Copyright (c) 2020 IETF Trust and the persons identified as the		Copyright (c) 2021 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 24 ¶		skipping to change at page 2, line 24 ¶
	4.2. Multi-Homed Enterprise: Single CPE, Multiple Upstream		4.2. Multi-Homed Enterprise: Single CPE, Multiple Upstream
	ISPs . . . . . . . . . . . . . . . . . . . . . . . . . . 5		ISPs . . . . . . . . . . . . . . . . . . . . . . . . . . 5
	4.3. Multi-homed Enterprise: Multiple CPEs, Multiple Upstream		4.3. Multi-homed Enterprise: Multiple CPEs, Multiple Upstream
	ISPs . . . . . . . . . . . . . . . . . . . . . . . . . . 6		ISPs . . . . . . . . . . . . . . . . . . . . . . . . . . 6
	4.4. Multi-homed Enterprise with the Same ISP . . . . . . . . 7		4.4. Multi-homed Enterprise with the Same ISP . . . . . . . . 7
	5. DOTS Multi-homing Deployment Considerations . . . . . . . . . 7		5. DOTS Multi-homing Deployment Considerations . . . . . . . . . 7
	5.1. Residential CPE . . . . . . . . . . . . . . . . . . . . . 8		5.1. Residential CPE . . . . . . . . . . . . . . . . . . . . . 8
	5.2. Multi-Homed Enterprise: Single CPE, Multiple Upstream		5.2. Multi-Homed Enterprise: Single CPE, Multiple Upstream
	ISPs . . . . . . . . . . . . . . . . . . . . . . . . . . 9		ISPs . . . . . . . . . . . . . . . . . . . . . . . . . . 9
	5.3. Multi-Homed Enterprise: Multiple CPEs, Multiple Upstream		5.3. Multi-Homed Enterprise: Multiple CPEs, Multiple Upstream
	ISPs . . . . . . . . . . . . . . . . . . . . . . . . . . 11		ISPs . . . . . . . . . . . . . . . . . . . . . . . . . . 12
	5.4. Multi-Homed Enterprise: Single ISP . . . . . . . . . . . 12		5.4. Multi-Homed Enterprise: Single ISP . . . . . . . . . . . 13
	6. Security Considerations . . . . . . . . . . . . . . . . . . . 13		6. Security Considerations . . . . . . . . . . . . . . . . . . . 13
	7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13		7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13
	8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 13		8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 13
	9. References . . . . . . . . . . . . . . . . . . . . . . . . . 13		9. References . . . . . . . . . . . . . . . . . . . . . . . . . 13
	9.1. Normative References . . . . . . . . . . . . . . . . . . 13		9.1. Normative References . . . . . . . . . . . . . . . . . . 14
	9.2. Informative References . . . . . . . . . . . . . . . . . 14		9.2. Informative References . . . . . . . . . . . . . . . . . 14
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 15		Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 15
	1. Introduction		1. Introduction
	In many deployments, it may not be possible for a network to		In many deployments, it may not be possible for a network to
	determine the cause of a distributed Denial-of-Service (DoS) attack		determine the cause of a distributed Denial-of-Service (DoS) attack
	[RFC4732]. Rather, the network may just realize that some resources		[RFC4732]. Rather, the network may just realize that some resources
	seem to be under attack. To improve such situation, the IETF is		seem to be under attack. To improve such situation, the IETF is
	specifying the DDoS Open Threat Signaling (DOTS)		specifying the DDoS Open Threat Signaling (DOTS) architecture
	[RFC8811]architecture, where a DOTS client can inform a DOTS server		[RFC8811], where a DOTS client can inform a DOTS server that the
	that the network is under a potential attack and that appropriate		network is under a potential attack and that appropriate mitigation
	mitigation actions are required. Indeed, because the lack of a		actions are required. Indeed, because the lack of a common method to
	common method to coordinate a real-time response among involved		coordinate a real-time response among involved actors and network
	actors and network domains jeopardizes the efficiency of DDoS attack		domains jeopardizes the efficiency of DDoS attack mitigation actions,
	mitigation actions, the DOTS protocol is meant to carry requests for		the DOTS protocol is meant to carry requests for DDoS attack
	DDoS attack mitigation, thereby reducing the impact of an attack and		mitigation, thereby reducing the impact of an attack and leading to
	leading to more efficient responsive actions.		more efficient responsive actions. [I-D.ietf-dots-use-cases]
	[I-D.ietf-dots-use-cases] identifies a set of scenarios for DOTS;		identifies a set of scenarios for DOTS; most of these scenarios
	most of these scenarios involve a Customer Premises Equipment (CPE).		involve a Customer Premises Equipment (CPE).
	The high-level base DOTS architecture is illustrated in Figure 1		The high-level base DOTS architecture is illustrated in Figure 1
	([RFC8811]):		([RFC8811]):
	+-----------+ +-------------+		+-----------+ +-------------+
	| Mitigator | ~~~~~~~~~~ | DOTS Server |		| Mitigator | ~~~~~~~~~~ | DOTS Server |
	+-----------+ +-------------+		+-----------+ +-------------+
	|		|
	|		|
	|		|
	+---------------+ +-------------+		+---------------+ +-------------+
	| Attack Target | ~~~~~~ | DOTS Client |		| Attack Target | ~~~~~~ | DOTS Client |
	+---------------+ +-------------+		+---------------+ +-------------+
	Figure 1: Basic DOTS Architecture		Figure 1: Basic DOTS Architecture
	[RFC8811] specifies that the DOTS client may be provided with a list		[RFC8811] specifies that the DOTS client may be provided with a list
	of DOTS servers; each of these servers is associated with one or more		of DOTS servers; each of these servers is associated with one or more
	IP addresses. These addresses may or may not be of the same address		IP addresses. These addresses may or may not be of the same address
	family. The DOTS client establishes one or more DOTS sessions by		family. The DOTS client establishes one or more DOTS sessions by
	connecting to the provided DOTS server(s) addresses.		connecting to the provided DOTS server(s) addresses (e.g.,
			[RFC8973]).
	DOTS may be deployed within networks that are connected to one single		DOTS may be deployed within networks that are connected to one single
	upstream provider. It can also be enabled within networks that are		upstream provider. It can also be enabled within networks that are
	multi-homed. The reader may refer to [RFC3582] for an overview of		multi-homed. The reader may refer to [RFC3582] for an overview of
	multi-homing goals and motivations. This document discusses DOTS		multi-homing goals and motivations. This document discusses DOTS
	multi-homing considerations. Specifically, the document aims to:		multi-homing considerations. Specifically, the document aims to:
	1. Complete the base DOTS architecture with multi-homing specifics.		1. Complete the base DOTS architecture with multi-homing specifics.
	Those specifics need to be taken into account because:		Those specifics need to be taken into account because:
	skipping to change at page 4, line 47 ¶		skipping to change at page 4, line 47 ¶
	3. Terminology		3. Terminology
	This document makes use of the terms defined in [RFC8811] and		This document makes use of the terms defined in [RFC8811] and
	[RFC4116].		[RFC4116].
	IP indifferently refers to IPv4 or IPv6.		IP indifferently refers to IPv4 or IPv6.
	4. Multi-Homing Scenarios		4. Multi-Homing Scenarios
	This section describes some multi-homing scenarios that are relevant		This section describes some multi-homing scenarios that are relevant
	to DOTS. In the following sub-sections, only the connections of		to DOTS. In the following subsections, only the connections of
	border routers are shown; internal network topologies are not		border routers are shown; internal network topologies are not
	elaborated.		elaborated.
	This section distinguishes between residential CPEs vs. enterprise		This section distinguishes between residential CPEs vs. enterprise
	CPEs because PI addresses may be used for enterprises while this is		CPEs because PI addresses may be used for enterprises while this is
	not the current practice for residential CPEs.		not the current practice for residential CPEs.
	4.1. Residential Single CPE		4.1. Residential Single CPE
	The scenario shown in Figure 2 is characterized as follows:		The scenario shown in Figure 2 is characterized as follows:
	o The home network is connected to the Internet using one single CPE		o The home network is connected to the Internet using one single
	(Customer Premises Equipment).		CPE.
	o The CPE is connected to multiple provisioning domains (i.e., both		o The CPE is connected to multiple provisioning domains (i.e., both
	fixed and mobile networks). Provisioning domain (PvD) is		fixed and mobile networks). Provisioning domain (PvD) is
	explained in [RFC7556].		explained in [RFC7556].
	o Each of these provisioning domains assigns IP addresses/prefixes		o Each of these provisioning domains assigns IP addresses/prefixes
	to the CPE and provides additional configuration information such		to the CPE and provides additional configuration information such
	as a list of DNS servers, DNS suffixes associated with the		as a list of DNS servers, DNS suffixes associated with the
	network, default gateway address, and DOTS server's name		network, default gateway address, and DOTS server's name
	[I-D.ietf-dots-server-discovery]. These addresses/prefixes are		[RFC8973]. These addresses/prefixes are assumed to be Provider-
	assumed to be Provider-Aggregatable (PA).		Aggregatable (PA).
	o Because of ingress filtering, packets forwarded by the CPE towards		o Because of ingress filtering, packets forwarded by the CPE towards
	a given provisioning domain must be sent with a source IP address		a given provisioning domain must be sent with a source IP address
	that was assigned by that domain [RFC8043].		that was assigned by that domain [RFC8043].
	+-------+ +-------+		+-------+ +-------+
	|Fixed | |Mobile |		|Fixed | |Mobile |
	|Network| |Network|		|Network| |Network|
	+---+---+ +---+---+		+---+---+ +---+---+
	| | Service Providers		| | Service Providers
	skipping to change at page 7, line 26 ¶		skipping to change at page 7, line 26 ¶
	Figure 4: Multi-homed Enterprise Network (Multiple CPEs, Multiple		Figure 4: Multi-homed Enterprise Network (Multiple CPEs, Multiple
	ISPs)		ISPs)
	4.4. Multi-homed Enterprise with the Same ISP		4.4. Multi-homed Enterprise with the Same ISP
	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).
	Editor's Note: The use of anycast addresses is to be consistently
	discussed.
	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 | DOTS |
	| | | gateway |		| | | gateway |
	+---------------------------+-------------------------+-------------+		+---------------------------+-------------------------+-------------+
	skipping to change at page 8, line 24 ¶		skipping to change at page 8, line 5 ¶
	| 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 | CPEs (rtr1 and rtr2) | and rtr2) |		| Single provisioning | CPEs (rtr1 and rtr2) | and rtr2) |
	| domain | | |		| domain | | |
	+---------------------------+-------------------------+-------------+		+---------------------------+-------------------------+-------------+
	Table 1: Sample Deployment Cases		Table 1: Sample Deployment Cases
	These deployment schemes are further discussed in the following sub-		These deployment schemes are further discussed in the following
	sections.		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
	the scenario described in Section 4.1.		the scenario described in Section 4.1.
	For each provisioning domain, the DOTS client MUST resolve the DOTS		For each provisioning domain, the DOTS client MUST resolve the DOTS
	server's name provided by a provisioning domain		server's name provided by a provisioning domain ([RFC8973]) using the
	([I-D.ietf-dots-server-discovery]) using the DNS servers learned from		DNS servers learned from the respective provisioning domain.
	the respective provisioning domain. IPv6-capable DOTS clients MUST		IPv6-capable DOTS clients MUST use the source address selection
	use the source address selection algorithm defined in [RFC6724] to		algorithm defined in [RFC6724] to select the candidate source
	select the candidate source addresses to contact each of these DOTS		addresses to contact each of these DOTS servers. DOTS sessions MUST
	servers. DOTS sessions MUST be established and maintained with each		be established and maintained with each of the DOTS servers because
	of the DOTS servers because the mitigation scope of these servers is		the mitigation scope of these servers is restricted. The DOTS client
	restricted. The DOTS client SHOULD use the certificate provisioned		SHOULD use the certificate provisioned by a provisioning domain to
	by a provisioning domain to authenticate itself to the DOTS server		authenticate itself to the DOTS server(s) provided by the same
	provided by the same provisioning domain.		provisioning domain.
	When conveying a mitigation request to protect the attack target(s),		When conveying a mitigation request to protect the attack target(s),
	the DOTS client among the DOTS servers available MUST select a DOTS		the DOTS client among the DOTS servers available MUST select a DOTS
	server whose network has assigned the prefixes from which target		server whose network has assigned the IP prefixes from which target
	prefixes and target IP addresses are derived. This implies that if		IP prefixes/addresses are derived. This implies that if no
	no appropriate DOTS server is found, the DOTS client MUST NOT send		appropriate DOTS server is found, the DOTS client MUST NOT send the
	the mitigation request to any DOTS server.		mitigation request to any other available DOTS server.
	For example, a mitigation request to protect target resources bound		For example, a mitigation request to protect target resources bound
	to a PA IP address/prefix cannot be satisfied by a provisioning		to a PA IP address/prefix cannot be satisfied by a provisioning
	domain another domain than the one that owns those addresses/		domain another domain than the one that owns those addresses/
	prefixes. Consequently, if a CPE detects a DDoS attack that spreads		prefixes. Consequently, if a CPE detects a DDoS attack that spreads
	over all its network attachments, it MUST contact both DOTS servers		over all its network attachments, it MUST contact both DOTS servers
	for mitigation purposes. Nevertheless, if the DDoS attack is		for mitigation purposes. Nevertheless, if the DDoS attack is
	received from one single network, then only the DOTS server of that		received from one single network, then only the DOTS server of that
	network MUST be contacted.		network MUST be contacted.
	The DOTS client MUST be able to associate a DOTS server with each		The DOTS client MUST be able to associate a DOTS server with each
	provisioning domain. For example, if the DOTS client is provisioned		provisioning domain. For example, if the DOTS client is provisioned
	with S1 using DHCP when attaching to a first network and with S2		with S1 using DHCP when attaching to a first network and with S2
	using Protocol Configuration Option (PCO) when attaching to a second		using Protocol Configuration Option (PCO) when attaching to a second
	network, the DOTS client must record the interface from which a DOTS		network, the DOTS client must record the interface from which a DOTS
	server was provisioned. DOTS signaling session to a given DOTS		server was provisioned. DOTS signaling session to a given DOTS
	server must be established using the interface from which the DOTS		server must be established using the interface from which the DOTS
	server was provisioned.		server was provisioned.
	+--+		+--+
	-----------|S1|		----------|S1|
	/ +--+		/ +--+
	/		/ DOTS Server Domain #1
	/		/
	+---+/		+---+/
	| C |		| C |
	+---+\		+---+\
	\		\
	\		\
	\ +--+		\ +--+
	-----------|S2|		----------|S2|
	+--+		+--+
			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 associations that can be
	established with a DOTS gateway, which is enabled within the context		established with a DOTS gateway, which is enabled within the context
	of the scenario described in Section 4.2. This deployment is		of the scenario described in Section 4.2. This deployment is
	characterized as follows:		characterized as follows:
	skipping to change at page 10, line 15 ¶		skipping to change at page 10, line 5 ¶
	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 DOTS gateway to
	contact its DOTS server(s). The DOTS gateways can be reachable from		contact its DOTS server(s). The DOTS gateways can be reachable from
	DOTS clients by using an unicast address or an anycast address.		DOTS clients by using an unicast address or an anycast address.
	Nevertheless, when PI addresses/prefixes are assigned, the DOTS		Nevertheless, when PI addresses/prefixes are assigned, the DOTS
	gateway MUST send mitigation requests to all its DOTS servers.		gateway MUST send mitigation requests to all its DOTS servers.
	Otherwise, the attack traffic may still be delivered via the ISP		Otherwise, the attack traffic may still be delivered via the ISP
	which hasn't received the mitigation request.		which hasn't received the mitigation request.
	+--+		+--+
	-----------|S1|		----------|S1|
	+---+ / +--+		+---+ / +--+
	| C1|----+ /		| C1|----+ / DOTS Server Domain #1
	+---+ | /		+---+ | /
	+---+ +-+-+/		+---+ +-+-+/
	| C3|------| G |		| C3|------| G |
	+---+ +-+-+\		+---+ +-+-+\
	+---+ | \		+---+ | \
	| C2|----+ \		| C2|----+ \
	+---+ \ +--+		+---+ \ +--+
	-----------|S2|		----------|S2|
	+--+		+--+
			DOTS Server Domain #2
	Figure 6: Multiple DOTS Clients, Single DOTS Gateway, Multiple DOTS		Figure 6: Multiple DOTS Clients, Single DOTS Gateway, Multiple DOTS
	Servers		Servers
	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:
	o One or more DOTS clients are enabled in hosts located in the		o One or more DOTS clients are enabled in hosts located in the
	internal network. These DOTS clients may use		internal network. These DOTS clients may use [RFC8973] to
	[I-D.ietf-dots-server-discovery] to discover their DOTS server(s).		discover their DOTS server(s).
	o These DOTS clients communicate directly with upstream DOTS		o These DOTS clients communicate directly with upstream DOTS
	servers.		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.		addresses to reach the DOTS servers is NOT RECOMMENDED.
	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 arise to steer traffic towards the appropriate		context), some issues arise to steer traffic towards the appropriate
	DOTS server by using the appropriate source IP address. These		DOTS server by using the appropriate source IP address. These
	complications discussed in [RFC4116] are not specific to DOTS.		complications discussed in [RFC4116] are not specific to DOTS.
	+--+		..........
			. +--+ .
	+--------|C1|--------+		+--------|C1|--------+
	| +--+ |		| . +--+ . |
	+--+ +--+ +--+		+--+ . +--+ . +--+
	|S2|------|C3|------|S1|		|S2|------|C3|------|S1|
	+--+ +--+ +--+		+--+ . +--+ . +--+
	| +--+ |		| . +--+ . |
	+--------|C2|--------+		+--------|C2|--------+
	+--+		. +--+ .
			..........
			DOTS Client
			Domain
	Figure 7: Multiple DOTS Clients, Multiple DOTS Servers		Figure 7: Multiple DOTS Clients, Multiple DOTS Servers
	Another deployment approach is to enable many DOTS clients; each of		Another deployment approach is to enable many DOTS clients; each of
	them is responsible for handling communications with a specific DOTS		them is responsible for handling communications with a specific DOTS
	server (see Figure 8).		server (see Figure 8).
	+--+		..........
	+--------|C1|		. +--+ .
	| +--+		+--------|C1| .
	+--+ +--+ +--+		| . +--+ .
	|S2| |C2|------|S1|		+--+ . +--+ . +--+
	+--+ +--+ +--+		|S2| . |C2|------|S1|
			+--+ . +--+ . +--+
			..........
			DOTS Client
			Domain
	Figure 8: Single Homed DOTS Clients		Figure 8: Single Homed DOTS Clients
	Each DOTS client SHOULD be provided with policies (e.g., a prefix		Each DOTS client SHOULD be provided with policies (e.g., a prefix
	filter that will be against DDoS detection alarms) that will trigger		filter that will be against DDoS detection alarms) that will trigger
	DOTS communications with the DOTS servers. Such policies will help		DOTS communications with the DOTS servers. Such policies will help
	the DOTS client to select the appropriate destination DOTS server.		the DOTS client to select the appropriate destination DOTS server.
	The CPE MUST select the appropriate source IP address when forwarding		The CPE MUST select the appropriate source IP address when forwarding
	DOTS messages received from an internal DOTS client. If anycast		DOTS messages received from an internal DOTS client. If anycast
	skipping to change at page 12, line 49 ¶		skipping to change at page 13, line 12 ¶
	Figure 9: Multiple DOTS Clients, Multiple DOTS Gateways, Multiple		Figure 9: Multiple DOTS Clients, Multiple DOTS Gateways, Multiple
	DOTS Servers		DOTS Servers
	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:
	1. The same DOTS server for all network attachments.		o The same DOTS server for all network attachments.
	2. Distinct DOTS servers for each network attachment. These DOTS		o Distinct DOTS servers for each network attachment. These DOTS
	servers need to coordinate when a mitigation action is received		servers need to coordinate when a mitigation action is received
	from the enterprise network.		from the enterprise network.
	In both cases, DOTS agents enabled within the enterprise network MAY		In both cases, DOTS agents enabled within the enterprise network MAY
	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].
	skipping to change at page 14, line 16 ¶		skipping to change at page 14, line 27 ¶
	2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,		2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
	May 2017, <https://www.rfc-editor.org/info/rfc8174>.		May 2017, <https://www.rfc-editor.org/info/rfc8174>.
	[RFC8811] Mortensen, A., Ed., Reddy.K, T., Ed., Andreasen, F.,		[RFC8811] Mortensen, A., Ed., Reddy.K, T., Ed., Andreasen, F.,
	Teague, N., and R. Compton, "DDoS Open Threat Signaling		Teague, N., and R. Compton, "DDoS Open Threat Signaling
	(DOTS) Architecture", RFC 8811, DOI 10.17487/RFC8811,		(DOTS) Architecture", RFC 8811, DOI 10.17487/RFC8811,
	August 2020, <https://www.rfc-editor.org/info/rfc8811>.		August 2020, <https://www.rfc-editor.org/info/rfc8811>.
	9.2. Informative References		9.2. Informative References
	[I-D.ietf-dots-server-discovery]
	Boucadair, M. and T. Reddy.K, "Distributed-Denial-of-
	Service Open Threat Signaling (DOTS) Agent Discovery",
	draft-ietf-dots-server-discovery-15 (work in progress),
	November 2020.
	[I-D.ietf-dots-use-cases]		[I-D.ietf-dots-use-cases]
	Dobbins, R., Migault, D., Moskowitz, R., Teague, N., Xia,		Dobbins, R., Migault, D., Moskowitz, R., Teague, N., Xia,
	L., and K. Nishizuka, "Use cases for DDoS Open Threat		L., and K. Nishizuka, "Use cases for DDoS Open Threat
	Signaling", draft-ietf-dots-use-cases-25 (work in		Signaling", draft-ietf-dots-use-cases-25 (work in
	progress), July 2020.		progress), July 2020.
	[RFC3582] Abley, J., Black, B., and V. Gill, "Goals for IPv6 Site-		[RFC3582] Abley, J., Black, B., and V. Gill, "Goals for IPv6 Site-
	Multihoming Architectures", RFC 3582,		Multihoming Architectures", RFC 3582,
	DOI 10.17487/RFC3582, August 2003,		DOI 10.17487/RFC3582, August 2003,
	<https://www.rfc-editor.org/info/rfc3582>.		<https://www.rfc-editor.org/info/rfc3582>.
	skipping to change at page 15, line 16 ¶		skipping to change at page 15, line 22 ¶
	Mortensen, A., and N. Teague, "Distributed Denial-of-		Mortensen, A., and N. Teague, "Distributed Denial-of-
	Service Open Threat Signaling (DOTS) Signal Channel		Service Open Threat Signaling (DOTS) Signal Channel
	Specification", RFC 8782, DOI 10.17487/RFC8782, May 2020,		Specification", RFC 8782, DOI 10.17487/RFC8782, May 2020,
	<https://www.rfc-editor.org/info/rfc8782>.		<https://www.rfc-editor.org/info/rfc8782>.
	[RFC8783] Boucadair, M., Ed. and T. Reddy.K, Ed., "Distributed		[RFC8783] Boucadair, M., Ed. and T. Reddy.K, Ed., "Distributed
	Denial-of-Service Open Threat Signaling (DOTS) Data		Denial-of-Service Open Threat Signaling (DOTS) Data
	Channel Specification", RFC 8783, DOI 10.17487/RFC8783,		Channel Specification", RFC 8783, DOI 10.17487/RFC8783,
	May 2020, <https://www.rfc-editor.org/info/rfc8783>.		May 2020, <https://www.rfc-editor.org/info/rfc8783>.
			[RFC8973] Boucadair, M. and T. Reddy.K, "DDoS Open Threat Signaling
			(DOTS) Agent Discovery", RFC 8973, DOI 10.17487/RFC8973,
			January 2021, <https://www.rfc-editor.org/info/rfc8973>.
	Authors' Addresses		Authors' Addresses
	Mohamed Boucadair		Mohamed Boucadair
	Orange		Orange
	Rennes 35000		Rennes 35000
	France		France
	Email: mohamed.boucadair@orange.com		Email: mohamed.boucadair@orange.com
	Tirumaleswar Reddy		Tirumaleswar Reddy
End of changes. 28 change blocks.
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