< draft-ietf-dots-multihoming-00.txt		draft-ietf-dots-multihoming-01.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: July 18, 2019 McAfee		Expires: July 25, 2019 McAfee
	January 14, 2019		January 21, 2019
	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-00		draft-ietf-dots-multihoming-01
	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 a set of 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
	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 July 18, 2019.		This Internet-Draft will expire on July 25, 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 2, line 12 ¶		skipping to change at page 2, line 12 ¶
	the Trust Legal Provisions and are provided without warranty as		the Trust Legal Provisions and are provided without warranty as
	described in the Simplified BSD License.		described in the Simplified BSD License.
	Table of Contents		Table of Contents
	1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2		1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
	2. Requirements Language . . . . . . . . . . . . . . . . . . . . 4		2. Requirements Language . . . . . . . . . . . . . . . . . . . . 4
	3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4		3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
	4. Multi-Homing Scenarios . . . . . . . . . . . . . . . . . . . 4		4. Multi-Homing Scenarios . . . . . . . . . . . . . . . . . . . 4
	4.1. Residential Single CPE . . . . . . . . . . . . . . . . . 5		4.1. Residential Single CPE . . . . . . . . . . . . . . . . . 5
	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 Deployment Considerations . . . . . . . . . . . . . . . 7		5. DOTS Deployment Considerations . . . . . . . . . . . . . . . 7
	5.1. Residential CPE . . . . . . . . . . . . . . . . . . . . . 7		5.1. Residential CPE . . . . . . . . . . . . . . . . . . . . . 7
	5.2. Multi-homed Enterprise: Single CPE, Multiple Upstream		5.2. Multi-Homed Enterprise: Single CPE, Multiple Upstream
	ISPs . . . . . . . . . . . . . . . . . . . . . . . . . . 8		ISPs . . . . . . . . . . . . . . . . . . . . . . . . . . 9
	5.3. Multi-homed Enterprise: Multiple CPEs, Multiple Upstream		5.3. Multi-Homed Enterprise: Multiple CPEs, Multiple Upstream
	ISPs . . . . . . . . . . . . . . . . . . . . . . . . . . 10		ISPs . . . . . . . . . . . . . . . . . . . . . . . . . . 11
	5.4. Multi-homed Enterprise: Single ISP . . . . . . . . . . . 11		5.4. Multi-Homed Enterprise: Single ISP . . . . . . . . . . . 12
	6. Security Considerations . . . . . . . . . . . . . . . . . . . 12		6. Security Considerations . . . . . . . . . . . . . . . . . . . 12
	7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12		7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12
	8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 12		8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 12
	9. References . . . . . . . . . . . . . . . . . . . . . . . . . 12		9. References . . . . . . . . . . . . . . . . . . . . . . . . . 13
	9.1. Normative References . . . . . . . . . . . . . . . . . . 12		9.1. Normative References . . . . . . . . . . . . . . . . . . 13
	9.2. Informative References . . . . . . . . . . . . . . . . . 13		9.2. Informative References . . . . . . . . . . . . . . . . . 13
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 14		Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 14
	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 for a distributed Denial-of-Service (DoS) attack		determine the cause of a distributed Denial-of-Service (DoS) attack
	[RFC4732], but instead just realize that some resources seem to be		[RFC4732]. Rather, the network may just realize that some resources
	under attack. To fill that gap, the IETF is specifying an		seem to be under attack. To improve such situation, the IETF is
	architecture, called DDoS Open Threat Signaling (DOTS)		specifying the DDoS Open Threat Signaling (DOTS)
	[I-D.ietf-dots-architecture], in which a DOTS client can inform a		[I-D.ietf-dots-architecture]architecture, where a DOTS client can
	DOTS server that the network is under a potential attack and that		inform a DOTS server that the network is under a potential attack and
	appropriate mitigation actions are required. Indeed, because the		that appropriate mitigation actions are required. Indeed, because
	lack of a common method to coordinate a real-time response among		the lack of a common method to coordinate a real-time response among
	involved actors and network domains inhibits the effectiveness of		involved actors and network domains jeopardizes the efficiency of
	DDoS attack mitigation, DOTS protocol is meant to carry requests for		DDoS attack mitigation actions, the DOTS protocol is meant to carry
	DDoS attack mitigation, thereby reducing the impact of an attack and		requests for DDoS attack mitigation, thereby reducing the impact of
	leading to more efficient defensive actions.		an attack and leading to more efficient responsive actions.
	[I-D.ietf-dots-use-cases] identifies a set of scenarios for DOTS;		[I-D.ietf-dots-use-cases] identifies a set of scenarios for DOTS;
	almost all these scenarios involve a CPE.		most of these scenarios involve a Customer Premises Equipment (CPE).
	The basic high-level DOTS architecture is illustrated in Figure 1		The high-level DOTS architecture is illustrated in Figure 1
	([I-D.ietf-dots-architecture]):		([I-D.ietf-dots-architecture]):
	+-----------+ +-------------+		+-----------+ +-------------+
	| Mitigator | ~~~~~~~~~~ | DOTS Server |		| Mitigator | ~~~~~~~~~~ | DOTS Server |
	+-----------+ +-------------+		+-----------+ +-------------+
	|		|
	|		|
	|		|
	+---------------+ +-------------+		+---------------+ +-------------+
	| Attack Target | ~~~~~~ | DOTS Client |		| Attack Target | ~~~~~~ | DOTS Client |
	+---------------+ +-------------+		+---------------+ +-------------+
	Figure 1: Basic DOTS Architecture		Figure 1: Basic DOTS Architecture
	[I-D.ietf-dots-architecture] specifies that the DOTS client may be		[I-D.ietf-dots-architecture] specifies that the DOTS client may be
	provided with a list of DOTS servers; each associated with one or		provided with a list of DOTS servers; each of these servers is
	more IP addresses. These addresses may or may not be of the same		associated with one or more IP addresses. These addresses may or may
	address family. The DOTS client establishes one or more DOTS		not be of the same address family. The DOTS client establishes one
	sessions by connecting to the provided DOTS server(s) addresses.		or more DOTS sessions by connecting to the provided DOTS server(s)
			addresses.
	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 taking into account because:		Those specifics need to be taken into account because:
	* Send a DOTS mitigation request to an arbitrary DOTS server		* Send a DOTS mitigation request to an arbitrary DOTS server
	won't help mitigating a DDoS attack.		won't help mitigating a DDoS attack.
	* Blindly forking all DOTS mitigation requests among all		* Blindly forking all DOTS mitigation requests among all
	available DOTS servers is suboptimal.		available DOTS servers is suboptimal.
	* Sequentially contacting DOTS servers may increase the delay		* Sequentially contacting DOTS servers may increase the delay
	before a mitigation plan is enforced.		before a mitigation plan is enforced.
	2. Identify DOTS deployment schemes in a multi-homing context, where		2. Identify DOTS deployment schemes in a multi-homing context, where
	DOTS service can be offered by all or a subset of upstream		DOTS services can be offered by all or a subset of upstream
	providers.		providers.
	3. Sketch guidelines and recommendations for placing DOTS requests		3. Sketch guidelines and recommendations for placing DOTS requests
	in multi-homed networks, e.g.,:		in multi-homed networks, e.g.,:
	* Select the appropriate DOTS server(s).		* Select the appropriate DOTS server(s).
	* Identify cases where anycast is not recommended.		* Identify cases where anycast is not recommended.
	This document adopts the following methodology:		This document adopts the following methodology:
	skipping to change at page 4, line 23 ¶		skipping to change at page 4, line 25 ¶
	* Provider-Independent (PI) vs. Provider-Aggregatable (PA) IP		* Provider-Independent (PI) vs. Provider-Aggregatable (PA) IP
	addresses		addresses
	o Describe the recommended behavior of DOTS clients and gateways for		o Describe the recommended behavior of DOTS clients and gateways for
	each case.		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 [I-D.ietf-dots-signal-channel] and		defined in [I-D.ietf-dots-signal-channel] and
	[I-D.ietf-dots-data-channel]; no specific extension is required to		[I-D.ietf-dots-data-channel]; no specific extension is required to
	the base DOTS protocols for deploying DOTS in a multihomed context.		the base DOTS protocols for deploying DOTS in a multi-homed 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
	"OPTIONAL" in this document are to be interpreted as described in BCP		"OPTIONAL" in this document are to be interpreted as described in BCP
	14 [RFC2119][RFC8174] when, and only when, they appear in all		14 [RFC2119][RFC8174] when, and only when, they appear in all
	capitals, as shown here.		capitals, as shown here.
	3. Terminology		3. Terminology
	This document makes use of the terms defined in		This document makes use of the terms defined in
	[I-D.ietf-dots-architecture] and [RFC4116].		[I-D.ietf-dots-architecture] and [RFC4116].
	IP refers to both IPv4 and IPv6.		IP indifferently refers to IPv4 or IPv6.
	4. Multi-Homing Scenarios		4. Multi-Homing Scenarios
	This section briefly describes some multi-homing scenarios that are		This section describes some multi-homing scenarios that are relevant
	relevant to DOTS. In the following sub-sections, only the		to DOTS. In the following sub-sections, only the connections of
	connections of border routers are shown; internal network topologies		border routers are shown; internal network topologies are not
	are not elaborated hereafter.		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 CPE
	skipping to change at page 5, line 21 ¶		skipping to change at page 5, line 21 ¶
	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.boucadair-dots-server-discovery]. These addresses/prefixes		[I-D.boucadair-dots-server-discovery]. These addresses/prefixes
	are said to be Provider-Aggregatable (PA).		are assumed to be Provider-Aggregatable (PA).
	o Because of ingress filtering, packets forwarded by the CPE to a		o Because of ingress filtering, packets forwarded by the CPE towards
	given provisioning domain must be send with a source IP address		a given provisioning domain must be sent with a source IP address
	that was assigned by that network [RFC8043].		that was assigned by that domain [RFC8043].
	+-------+ +-------+		+-------+ +-------+
	|Fixed | |Mobile |		|Fixed | |Mobile |
	|Network| |Network|		|Network| |Network|
	+---+---+ +---+---+		+---+---+ +---+---+
	| | Service Providers		| | Service Providers
	............|....................|.......................		............|....................|.......................
	+---------++---------+ Home Network		+---------++---------+ Home Network
	||		||
	+--++-+		+--++-+
	| CPE |		| CPE |
	+-----+		+-----+
	... (Internal Network)		... (Internal Network)
	Figure 2: Typical Multi-homed Residential CPE		Figure 2: Typical Multi-homed Residential CPE
	4.2. Multi-homed Enterprise: Single CPE, Multiple Upstream ISPs		4.2. Multi-Homed Enterprise: Single CPE, Multiple Upstream ISPs
	The scenario shown in Figure 3 is characterized as follows:		The scenario shown in Figure 3 is characterized as follows:
	o The enterprise network is connected to the Internet using one		o The enterprise network is connected to the Internet using one
	single router.		single router.
	o That router is connected to multiple provisioning domains (i.e.,		o That router is connected to multiple provisioning domains (i.e.,
	managed by distinct administrative entities).		managed by distinct administrative entities).
	Unlike the previous scenario, two sub-cases can be considered for an		Unlike the previous scenario, two sub-cases can be considered for an
	enterprise network with regards to assigned addresses:		enterprise network with regards to assigned addresses:
	1. PI addresses/prefixes: The enterprise is the owner of the IP		1. PI addresses/prefixes: The enterprise is the owner of the IP
	addresses/prefixes; the same address/prefix is then used for		addresses/prefixes; the same address/prefix is then used when
	communication placed using any of the provisioning domains.		establishing communications over any of the provisioning domains.
	2. PA addresses/prefixes: each of provisioning domains assigns IP		2. PA addresses/prefixes: each of the provisioning domains assigns
	addresses/prefixes to the enterprise network.		IP addresses/prefixes to the enterprise network.
	+------+ +------+		+------+ +------+
	| ISP1 | | ISP2 |		| ISP1 | | ISP2 |
	+---+--+ +--+---+		+---+--+ +--+---+
	| | Service Providers		| | Service Providers
	............|....................|.......................		............|....................|.......................
	+---------++---------+ Enterprise Network		+---------++---------+ Enterprise Network
	||		||
	+--++-+		+--++-+
	| rtr |		| rtr |
	+-----+		+-----+
	... (Internal Network)		... (Internal Network)
	Figure 3: Multi-homed Enterprise Network (Single CPE connected to		Figure 3: Multi-homed Enterprise Network (Single CPE connected to
	Multiple Networks)		Multiple Networks)
	4.3. Multi-homed Enterprise: Multiple CPEs, Multiple Upstream ISPs		4.3. Multi-homed Enterprise: Multiple CPEs, Multiple Upstream ISPs
	This scenario is similar to the one in Section 4.2; the main		This scenario is similar to the one described in Section 4.2; the
	difference is that dedicated routers are used to connect to each		main difference is that dedicated routers are used to connect to each
	provisioning domain.		provisioning domain.
	+------+ +------+		+------+ +------+
	| ISP1 | | ISP2 |		| ISP1 | | ISP2 |
	+---+--+ +--+---+		+---+--+ +--+---+
	| | Service Providers		| | Service Providers
	......................|..........|.......................		......................|..........|.......................
	| | Enterprise Network		| | Enterprise Network
	+---+--+ +--+---+		+---+--+ +--+---+
	| rtr1 | | rtr2 |		| rtr1 | | rtr2 |
	+------+ +------+		+------+ +------+
	... (Internal Network)		... (Internal Network)
	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 provided 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 Deployment Considerations		5. DOTS 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 |
	+---------------------------+-------------------------+-------------+		+---------------------------+-------------------------+-------------+
	| 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 |
	skipping to change at page 7, line 41 ¶		skipping to change at page 7, line 44 ¶
	| 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 sub-
	sections.		sections.
	5.1. Residential CPE		5.1. Residential CPE
	Figure 5 depicts DOTS sessions that are required to be established		Figure 5 depicts DOTS sessions that need to be established between a
	between a DOTS client (C) and DOTS servers (S1, S2) in 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
	([I-D.boucadair-dots-server-discovery]) using the DNS servers learned		([I-D.boucadair-dots-server-discovery]) using the DNS servers learned
	from the same provisioning domain. The DOTS client MUST use the		from the respective provisioning domain. The DOTS client MUST use
	source address selection algorithm defined in [RFC6724] to select the		the source address selection algorithm defined in [RFC6724] to select
	candidate source addresses to contact each of these DOTS servers.		the candidate source addresses to contact each of these DOTS servers.
	DOTS sessions must be established and maintained with each of the		DOTS sessions must be established and maintained with each of the
	DOTS servers because the mitigation scope of these servers is		DOTS servers because the mitigation scope of these servers is
	restricted. The DOTS client SHOULD use the certificate provisioned		restricted. The DOTS client SHOULD use the certificate provisioned
	by a provisioning domain to authenticate itself to the DOTS server		by a provisioning domain to authenticate itself to the DOTS server
	provided by the same provisioning domain. When conveying a		provided by the same provisioning domain.
	mitigation request to protect the attack target(s), the DOTS client
	among the DOTS servers available MUST select a DOTS server whose		When conveying a mitigation request to protect the attack target(s),
	network has assigned the prefixes from which target prefixes and		the DOTS client among the DOTS servers available MUST select a DOTS
	target IP addresses are derived. This implies that if no appropriate		server whose network has assigned the prefixes from which target
	DOTS server is found, the DOTS client must not send the mitigation		prefixes and target IP addresses are derived. This implies that if
	request to any DOTS server. For example, mitigation request to		no appropriate DOTS server is found, the DOTS client must not send
	protect target resources bound to a PA IP address/prefix cannot be		the mitigation request to any DOTS server.
	honored by an provisioning domain other than the one that owns those
	addresses/prefixes. Consequently, Typically, if a CPE detects a DDoS		For example, a mitigation request to protect target resources bound
	attack on all its network attachments, it must contact both DOTS		to a PA IP address/prefix cannot be satisfied by a provisioning
	servers for mitigation. Nevertheless, if the DDoS attack is received		domain another domain than the one that owns those addresses/
	from one single network, then only the DOTS server of that network		prefixes. Consequently, if a CPE detects a DDoS attack that spreads
	must be contacted.		over all its network attachments, it must contact both DOTS servers
			for mitigation purposes. Nevertheless, if the DDoS attack is
			received from one single network, then only the DOTS server of that
			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.
	skipping to change at page 8, line 46 ¶		skipping to change at page 9, line 5 ¶
	| C |		| C |
	+---+\		+---+\
	\		\
	\		\
	\ +--+		\ +--+
	-----------|S2|		-----------|S2|
	+--+		+--+
	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 is enabled in the context of the		established with a DOTS gateway, which is enabled within the context
	scenario described in Section 4.2. This deployment is characterized		of the scenario described in Section 4.2. This deployment is
	as follows:		characterized as follows:
	o One of more DOTS clients are enabled in hosts located in the		o One of more DOTS clients are enabled in hosts located in the
	internal network.		internal network.
	o A DOTS gateway is enabled to aggregate/relay the requests to		o A DOTS gateway is enabled to aggregate and then relay the requests
	upstream DOTS servers.		towards upstream 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 are 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 client using a unicast or 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 sent the same request to all its DOTS servers.		gateway MUST send the same request to all its DOTS servers.
	+--+		+--+
	-----------|S1|		-----------|S1|
	+---+ / +--+		+---+ / +--+
	| C1|----+ /		| C1|----+ /
	+---+ | /		+---+ | /
	+---+ +-+-+/		+---+ +-+-+/
	| C3|------| G |		| C3|------| G |
	+---+ +-+-+\		+---+ +-+-+\
	+---+ | \		+---+ | \
	skipping to change at page 9, line 39 ¶		skipping to change at page 9, line 46 ¶
	+---+ \ +--+		+---+ \ +--+
	-----------|S2|		-----------|S2|
	+--+		+--+
	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 of 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 client may use		internal network. These DOTS clients may use
	[I-D.boucadair-dots-server-discovery] to discover its DOTS		[I-D.boucadair-dots-server-discovery] to discover their DOTS
	server(s).		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 can send the		If PI addresses/prefixes are in use, the DOTS client MUST send the
	mitigation request for all its PI addresses/prefixes to any one of		mitigation request for all its PI addresses/prefixes to all the DOTS
	the DOTS servers. The use of anycast addresses is NOT RECOMMENDED.		servers. The use of anycast addresses is NOT RECOMMENDED.
	If PA addresses/prefxies are used, the same considerations discussed		If PA addresses/prefixes are used, the same considerations discussed
	in Section 5.1 are 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 located on the CPE and multiple addreses/prefixes may		clients are not embedded in the CPE and multiple addreses/prefixes
	not be assigned to the DOTS client (IPv4 context, typically), some		may not be assigned to the DOTS client (typically in an IPv4
	complications arise to steer the traffic to the appropriate DOTS		context), some issues arise to steer traffic towards the appropriate
	server using the appropriate source IP address. These complications		DOTS server by using the appropriate source IP address. These
	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|--------+
	+--+		+--+
	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 responsible to handle communication with a specific DOTS server		them is responsible for handling communications with a specific DOTS
	(see Figure 8). Each DOTS client is provided with policies (e.g.,		server (see Figure 8).
	prefix filter) that will trigger DOTS communications with the DOTS
	servers. The CPE MUST select the appropriate source IP address when
	forwarding DOTS messages received from an internal DOTS client. If
	anycast addresses are used to reach DOTS servers, the CPE may not be
	able to select the appropriate provisioning domain to which the
	mitigation request should be forwarded. As a consequence, the
	request may not be forwarded to the appropriate DOTS server.
	+--+		+--+
	+--------|C1|		+--------|C1|
	| +--+		| +--+
	+--+ +--+ +--+		+--+ +--+ +--+
	|S2| |C2|------|S1|		|S2| |C2|------|S1|
	+--+ +--+ +--+		+--+ +--+ +--+
	Figure 8: Single Homed DOTS Clients		Figure 8: Single Homed DOTS Clients
	5.3. Multi-homed Enterprise: Multiple CPEs, Multiple Upstream ISPs		Each DOTS client is provided with policies (e.g., prefix filter) that
			will trigger DOTS communications with the DOTS servers. Such
			policies will help the DOTS client to select the appropriate
			destination IP address.
	The deployments depicted in Figure 7 and Figure 8 apply also for the		The CPE MUST select the appropriate source IP address when forwarding
			DOTS messages received from an internal DOTS client. If anycast
			addresses are used to reach DOTS servers, the CPE may not be able to
			select the appropriate provisioning domain to which the mitigation
			request should be forwarded. As a consequence, the request may not
			be forwarded to the appropriate DOTS server.
			5.3. Multi-Homed Enterprise: Multiple CPEs, Multiple Upstream ISPs
			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:
	o DOTS clients are enabled in hosts located in the internal network.		o DOTS clients are enabled in hosts located in the internal network.
	o A DOTS gateway is enabled in each CPE (rtr1, rtr2).		o A DOTS gateway is enabled in each CPE (rtr1, rtr2).
	o Each of these DOTS gateways communicate with the DOTS server of		o Each of these DOTS gateways communicates with the DOTS server of
	the provisioning domain.		the provisioning domain.
	When PI addresses/prefixes are used, DOTS clients can contact any of		When PI addresses/prefixes are used, DOTS clients MUST contact all
	the DOTS gateways to send a DOTS message. DOTS gateway will then		the DOTS gateways to send a DOTS message. DOTS gateways will then
	relay the request to the DOTS server. Note that the use of anycast		relay the request to the DOTS server. Note that the use of anycast
	addresses is NOT RECOMMENDED to establish DOTS sessions between DOTS		addresses is NOT RECOMMENDED to establish DOTS sessions between DOTS
	client and DOTS gateways.		clients and DOTS gateways.
	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, these MUST contact all DOTS gateways simultaneously		to DOTS clients, the latter MUST contact all DOTS gateways
	to send a DOTS message. Upon receipt of a request by a DOTS gateway,		simultaneously to send a DOTS message. Upon receipt of a request by
	it MUST check whether the request is to be forwarded upstream or be		a DOTS gateway, it MUST check whether the request is to be forwarded
	rejected.		upstream (if the target IP prefix is 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,		provided to DOTS clients using some means that are out of scope of
	these later MUST select the appropriate DOTS gateway to be contacted.		this document, the clients MUST select the appropriate DOTS gateway
	The use of anycast is NOT RECOMMENDED to reach DOTS gateways.		to reach. The use of anycast addresses is NOT RECOMMENDED to reach
			DOTS gateways.
	+---+		+---+
	+------------| 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
	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 decided 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.		1. The same DOTS server for all network attachments.
	2. Distinct DOTS servers for each network attachment. These DOTS		2. Distinct DOTS servers for each network attachment. These DOTS
	servers needs 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 place 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
	[I-D.ietf-dots-architecture].		[I-D.ietf-dots-architecture].
	TBD: In Home networks, if EST is used then how will the DOTS gateway		TBD: In Home networks, if EST is used then how will the DOTS gateway
	(EST client) be provisioned with credentials for initial enrolment		(EST client) be provisioned with credentials for initial enrolment
	(see Section 2.2 in RFC 7030).		(see Section 2.2 in RFC 7030).
	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 Wei		Thanks to Roland Dobbins, Nik Teague, Jon Shallow, Dan Wing, Wei Pan,
	Pan for sharing their comments on the mailing list.		and Christian Jacquenet for sharing their comments on the mailing
			list.
	Thanks to Kirill Kasavchenko for the comments.		Thanks to Kirill Kasavchenko for the comments.
	9. References		9. References
	9.1. Normative References		9.1. Normative References
	[I-D.ietf-dots-architecture]		[I-D.ietf-dots-architecture]
	Mortensen, A., Andreasen, F., K, R., Teague, N., Compton,		Mortensen, A., Andreasen, F., K, R., Teague, N., Compton,
	R., and c. christopher_gray3@cable.comcast.com,		R., and c. christopher_gray3@cable.comcast.com,
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