Multi-homing Deployment Considerations for Distributed-Denial-of-Service Open Threat Signaling (DOTS)
draft-ietf-dots-multihoming-06

Document Type Active Internet-Draft (dots WG)
Authors Mohamed Boucadair  , Tirumaleswar Reddy.K  , Wei Pan 
Last updated 2021-05-25
Replaces draft-boucadair-dots-multihoming
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Network Working Group                                       M. Boucadair
Internet-Draft                                                    Orange
Intended status: Standards Track                                T. Reddy
Expires: November 26, 2021                                        McAfee
                                                                  W. Pan
                                                     Huawei Technologies
                                                            May 25, 2021

Multi-homing Deployment Considerations for Distributed-Denial-of-Service
                      Open Threat Signaling (DOTS)
                     draft-ietf-dots-multihoming-06

Abstract

   This document discusses multi-homing considerations for Distributed-
   Denial-of-Service Open Threat Signaling (DOTS).  The goal is to
   provide some guidance for DOTS clients/gateways when multihomed.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on November 26, 2021.

Copyright Notice

   Copyright (c) 2021 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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   include Simplified BSD License text as described in Section 4.e of

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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Requirements Language . . . . . . . . . . . . . . . . . . . .   4
   3.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   4
   4.  Multi-Homing Scenarios  . . . . . . . . . . . . . . . . . . .   4
     4.1.  Residential Single CPE  . . . . . . . . . . . . . . . . .   5
     4.2.  Multi-Homed Enterprise: Single CPE, Multiple Upstream
           ISPs  . . . . . . . . . . . . . . . . . . . . . . . . . .   5
     4.3.  Multi-homed Enterprise: Multiple CPEs, Multiple Upstream
           ISPs  . . . . . . . . . . . . . . . . . . . . . . . . . .   6
     4.4.  Multi-homed Enterprise with the Same ISP  . . . . . . . .   7
   5.  DOTS Multi-homing Deployment Considerations . . . . . . . . .   7
     5.1.  Residential CPE . . . . . . . . . . . . . . . . . . . . .   8
     5.2.  Multi-Homed Enterprise: Single CPE, Multiple Upstream
           ISPs  . . . . . . . . . . . . . . . . . . . . . . . . . .   9
     5.3.  Multi-Homed Enterprise: Multiple CPEs, Multiple Upstream
           ISPs  . . . . . . . . . . . . . . . . . . . . . . . . . .  12
     5.4.  Multi-Homed Enterprise: Single ISP  . . . . . . . . . . .  13
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  13
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  13
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  13
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  13
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  14
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  14
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  15

1.  Introduction

   In many deployments, it may not be possible for a network to
   determine the cause of a distributed Denial-of-Service (DoS) attack
   [RFC4732].  Rather, the network may just realize that some resources
   seem to be under attack.  To improve such situation, the IETF is
   specifying the DDoS Open Threat Signaling (DOTS) architecture
   [RFC8811], where a DOTS client can inform a DOTS server that the
   network is under a potential attack and that appropriate mitigation
   actions are required.  Indeed, because the lack of a common method to
   coordinate a real-time response among involved actors and network
   domains jeopardizes the efficiency of DDoS attack mitigation actions,
   the DOTS protocol is meant to carry requests for DDoS attack
   mitigation, thereby reducing the impact of an attack and leading to
   more efficient responsive actions.  [I-D.ietf-dots-use-cases]
   identifies a set of scenarios for DOTS; most of these scenarios
   involve a Customer Premises Equipment (CPE).

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   The high-level base DOTS architecture is illustrated in Figure 1
   ([RFC8811]):

          +-----------+            +-------------+
          | Mitigator | ~~~~~~~~~~ | DOTS Server |
          +-----------+            +-------------+
                                          |
                                          |
                                          |
          +---------------+        +-------------+
          | Attack Target | ~~~~~~ | DOTS Client |
          +---------------+        +-------------+

                     Figure 1: Basic DOTS Architecture

   [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
   IP addresses.  These addresses may or may not be of the same address
   family.  The DOTS client establishes one or more DOTS sessions by
   connecting to the provided DOTS server(s) addresses (e.g.,
   [RFC8973]).

   DOTS may be deployed within networks that are connected to one single
   upstream provider.  It can also be enabled within networks that are
   multi-homed.  The reader may refer to [RFC3582] for an overview of
   multi-homing goals and motivations.  This document discusses DOTS
   multi-homing considerations.  Specifically, the document aims to:

   1.  Complete the base DOTS architecture with multi-homing specifics.
       Those specifics need to be taken into account because:

       *  Send a DOTS mitigation request to an arbitrary DOTS server
          won't help mitigating a DDoS attack.

       *  Blindly forking all DOTS mitigation requests among all
          available DOTS servers is suboptimal.

       *  Sequentially contacting DOTS servers may increase the delay
          before a mitigation plan is enforced.

   2.  Identify DOTS deployment schemes in a multi-homing context, where
       DOTS services can be offered by all or a subset of upstream
       providers.

   3.  Sketch guidelines and recommendations for placing DOTS requests
       in multi-homed networks, e.g.,:

       *  Select the appropriate DOTS server(s).

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       *  Identify cases where anycast is not recommended.

   This document adopts the following methodology:

   o  Identify and extract viable deployment candidates from
      [I-D.ietf-dots-use-cases].

   o  Augment the description with multi-homing technicalities, e.g.,

      *  One vs. multiple upstream network providers

      *  One vs. multiple interconnect routers

      *  Provider-Independent (PI) vs. Provider-Aggregatable (PA) IP
         addresses

   o  Describe the recommended behavior of DOTS clients and gateways for
      each case.

   Multi-homed DOTS agents are assumed to make use of the protocols
   defined in [RFC8782] and [RFC8783]; no specific extension is required
   to the base DOTS protocols for deploying DOTS in a multi-homed
   context.

2.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 [RFC2119][RFC8174] when, and only when, they appear in all
   capitals, as shown here.

3.  Terminology

   This document makes use of the terms defined in [RFC8811] and
   [RFC4116].

   IP indifferently refers to IPv4 or IPv6.

4.  Multi-Homing Scenarios

   This section describes some multi-homing scenarios that are relevant
   to DOTS.  In the following subsections, only the connections of
   border routers are shown; internal network topologies are not
   elaborated.

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   This section distinguishes between residential CPEs vs. enterprise
   CPEs because PI addresses may be used for enterprises while this is
   not the current practice for residential CPEs.

4.1.  Residential Single CPE

   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 CPE is connected to multiple provisioning domains (i.e., both
      fixed and mobile networks).  Provisioning domain (PvD) is
      explained in [RFC7556].

   o  Each of these provisioning domains assigns IP addresses/prefixes
      to the CPE and provides additional configuration information such
      as a list of DNS servers, DNS suffixes associated with the
      network, default gateway address, and DOTS server's name
      [RFC8973].  These addresses/prefixes are assumed to be Provider-
      Aggregatable (PA).

   o  Because of ingress filtering, packets forwarded by the CPE towards
      a given provisioning domain must be sent with a source IP address
      that was assigned by that domain [RFC8043].

                  +-------+            +-------+
                  |Fixed  |            |Mobile |
                  |Network|            |Network|
                  +---+---+            +---+---+
                      |                    |     Service Providers
          ............|....................|.......................
                      +---------++---------+     Home Network
                                ||
                             +--++-+
                             | CPE |
                             +-----+
                                   ... (Internal Network)

               Figure 2: Typical Multi-homed Residential CPE

4.2.  Multi-Homed Enterprise: Single CPE, Multiple Upstream ISPs

   The scenario shown in Figure 3 is characterized as follows:

   o  The enterprise network is connected to the Internet using one
      single router.

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   o  That router is connected to multiple provisioning domains (i.e.,
      managed by distinct administrative entities).

   Unlike the previous scenario, two sub-cases can be considered for an
   enterprise network with regards to assigned addresses:

   1.  PI addresses/prefixes: The enterprise is the owner of the IP
       addresses/prefixes; the same address/prefix is then used when
       establishing communications over any of the provisioning domains.

   2.  PA addresses/prefixes: Each of the provisioning domains assigns
       IP addresses/prefixes to the enterprise network.

                  +------+              +------+
                  | ISP1 |              | ISP2 |
                  +---+--+              +--+---+
                      |                    |     Service Providers
          ............|....................|.......................
                      +---------++---------+     Enterprise Network
                                ||
                             +--++-+
                             | rtr |
                             +-----+
                                   ... (Internal Network)

     Figure 3: Multi-homed Enterprise Network (Single CPE connected to
                            Multiple Networks)

4.3.  Multi-homed Enterprise: Multiple CPEs, Multiple Upstream ISPs

   This scenario is similar to the one described in Section 4.2; the
   main difference is that dedicated routers are used to connect to each
   provisioning domain.

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                            +------+    +------+
                            | ISP1 |    | ISP2 |
                            +---+--+    +--+---+
                                |          |     Service Providers
          ......................|..........|.......................
                                |          |     Enterprise Network
                            +---+--+    +--+---+
                            | rtr1 |    | rtr2 |
                            +------+    +------+

                                  ... (Internal Network)

     Figure 4: Multi-homed Enterprise Network (Multiple CPEs, Multiple
                                   ISPs)

4.4.  Multi-homed Enterprise with the Same ISP

   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
   domain).

5.  DOTS Multi-homing Deployment Considerations

   Table 1 provides some sample, non-exhaustive, deployment schemes to
   illustrate how DOTS agents may be deployed for each of the scenarios
   introduced in Section 4.

   +---------------------------+-------------------------+-------------+
   |          Scenario         |       DOTS client       |     DOTS    |
   |                           |                         |   gateway   |
   +---------------------------+-------------------------+-------------+
   |      Residential CPE      |           CPE           |     N/A     |
   +---------------------------+-------------------------+-------------+
   |    Single CPE, Multiple   |  internal hosts or CPE  |     CPE     |
   |    provisioning domains   |                         |             |
   +---------------------------+-------------------------+-------------+
   |  Multiple CPEs, Multiple  |  internal hosts or all  |  CPEs (rtr1 |
   |    provisioning domains   |   CPEs (rtr1 and rtr2)  |  and rtr2)  |
   +---------------------------+-------------------------+-------------+
   |  Multi-homed enterprise,  |  internal hosts or all  |  CPEs (rtr1 |
   |    Single provisioning    |   CPEs (rtr1 and rtr2)  |  and rtr2)  |
   |           domain          |                         |             |
   +---------------------------+-------------------------+-------------+

                     Table 1: Sample Deployment Cases

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   These deployment schemes are further discussed in the following
   subsections.

5.1.  Residential CPE

   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
   the scenario described in Section 4.1.

   For each provisioning domain, the DOTS client MUST resolve the DOTS
   server's name provided by a provisioning domain ([RFC8973]) using the
   DNS servers learned from the respective provisioning domain.
   IPv6-capable DOTS clients MUST use the source address selection
   algorithm defined in [RFC6724] to select the candidate source
   addresses to contact each of these DOTS servers.  DOTS sessions MUST
   be established and maintained with each of the DOTS servers because
   the mitigation scope of these servers is restricted.  The DOTS client
   SHOULD use the certificate provisioned by a provisioning domain to
   authenticate itself to the DOTS server(s) provided by the same
   provisioning domain.

   When conveying a mitigation request to protect the attack target(s),
   the DOTS client among the DOTS servers available MUST select a DOTS
   server whose network has assigned the IP prefixes from which target
   IP prefixes/addresses are derived.  This implies that if no
   appropriate DOTS server is found, the DOTS client MUST NOT send the
   mitigation request to any other available DOTS server.

   For example, a mitigation request to protect target resources bound
   to a PA IP address/prefix cannot be satisfied by a provisioning
   domain another domain than the one that owns those addresses/
   prefixes.  Consequently, if a CPE detects a DDoS attack that spreads
   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
   provisioning domain.  For example, if the DOTS client is provisioned
   with S1 using DHCP when attaching to a first network and with S2
   using Protocol Configuration Option (PCO) when attaching to a second
   network, the DOTS client must record the interface from which a DOTS
   server was provisioned.  DOTS signaling session to a given DOTS
   server must be established using the interface from which the DOTS
   server was provisioned.

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                                            +--+
                                  ----------|S1|
                                /           +--+
                               /    DOTS Server Domain #1
                              /
                        +---+/
                        | C |
                        +---+\
                              \
                               \
                                \           +--+
                                  ----------|S2|
                                            +--+
                                    DOTS Server Domain #2

       Figure 5: DOTS Associations for a Multihomed Residential CPE

5.2.  Multi-Homed Enterprise: Single CPE, Multiple Upstream ISPs

   Figure 6 illustrates a first set of DOTS associations that can be
   established with a DOTS gateway, which is enabled within the context
   of the scenario described in Section 4.2.  This deployment is
   characterized as follows:

   o  One of more DOTS clients are enabled in hosts located in the
      internal network.

   o  A DOTS gateway is enabled to aggregate and then relay the requests
      towards upstream DOTS servers.

   When PA addresses/prefixes are in use, the same considerations
   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
   DOTS clients by using an unicast address or an anycast address.

   Nevertheless, when PI addresses/prefixes are assigned, the DOTS
   gateway MUST send mitigation requests to all its DOTS servers.
   Otherwise, the attack traffic may still be delivered via the ISP
   which hasn't received the mitigation request.

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                                              +--+
                                    ----------|S1|
                   +---+          /           +--+
                   | C1|----+    /     DOTS Server Domain #1
                   +---+    |   /
               +---+      +-+-+/
               | C3|------| G |
               +---+      +-+-+\
                   +---+    |   \
                   | C2|----+    \
                   +---+          \           +--+
                                    ----------|S2|
                                              +--+
                                      DOTS Server Domain #2

    Figure 6: Multiple DOTS Clients, Single DOTS Gateway, Multiple DOTS
                                  Servers

   An alternate deployment model is depicted in Figure 7.  This
   deployment assumes that:

   o  One or more DOTS clients are enabled in hosts located in the
      internal network.  These DOTS clients may use [RFC8973] to
      discover their DOTS server(s).

   o  These DOTS clients communicate directly with upstream DOTS
      servers.

   If PI addresses/prefixes are in use, the DOTS client MUST send a
   mitigation request to all the DOTS servers.  The use of anycast
   addresses to reach the DOTS servers is NOT RECOMMENDED.

   If PA addresses/prefixes are used, the same considerations discussed
   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
   may not be assigned to the DOTS client (typically in an IPv4
   context), some issues arise to steer traffic towards the appropriate
   DOTS server by using the appropriate source IP address.  These
   complications discussed in [RFC4116] are not specific to DOTS.

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                                ..........
                                .  +--+  .
                          +--------|C1|--------+
                          |     .  +--+  .     |
                         +--+   .  +--+  .   +--+
                         |S2|------|C3|------|S1|
                         +--+   .  +--+  .   +--+
                          |     .  +--+  .     |
                          +--------|C2|--------+
                                .  +--+  .
                                ..........
                               DOTS Client
                                 Domain

          Figure 7: Multiple DOTS Clients, Multiple DOTS Servers

   Another deployment approach is to enable many DOTS clients; each of
   them is responsible for handling communications with a specific DOTS
   server (see Figure 8).

                                ..........
                                .  +--+  .
                          +--------|C1|  .
                          |     .  +--+  .
                         +--+   .  +--+  .   +--+
                         |S2|   .  |C2|------|S1|
                         +--+   .  +--+  .   +--+
                                ..........
                               DOTS Client
                                 Domain

                    Figure 8: Single Homed DOTS Clients

   Each DOTS client SHOULD be provided with policies (e.g., a prefix
   filter that will be against DDoS detection alarms) that will trigger
   DOTS communications with the DOTS servers.  Such policies will help
   the DOTS client to select the appropriate destination DOTS server.

   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.

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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 is to select the appropriate exit router when contacting a
   given DOTS server.

   An alternative deployment scheme is shown in Figure 9:

   o  DOTS clients are enabled in hosts located in the internal network.

   o  A DOTS gateway is enabled in each CPE (rtr1, rtr2).

   o  Each of these DOTS gateways communicates with the DOTS server of
      the provisioning domain.

   When PI addresses/prefixes are used, DOTS clients MUST contact all
   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
   addresses is NOT RECOMMENDED to establish DOTS sessions between DOTS
   clients and DOTS gateways.

   When PA addresses/prefixes are used, but no filter rules are provided
   to DOTS clients, the latter MUST contact all DOTS gateways
   simultaneously to send a DOTS message.  Upon receipt of a request by
   a DOTS gateway, it MUST check whether the request is to be forwarded
   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
   provided to DOTS clients using some means that are out of scope of
   this document, the clients MUST select the appropriate DOTS gateway
   to reach.  The use of anycast addresses is NOT RECOMMENDED to reach
   DOTS gateways.

                                       +---+
                          +------------| C1|----+
                          |            +---+    |
              +--+      +-+-+      +---+      +-+-+      +--+
              |S2|------|G2 |------| C3|------|G1 |------|S1|
              +--+      +-+-+      +---+      +-+-+      +--+
                          |            +---+    |
                          +------------| C2|----+
                                       +---+

     Figure 9: Multiple DOTS Clients, Multiple DOTS Gateways, Multiple
                               DOTS Servers

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5.4.  Multi-Homed Enterprise: Single ISP

   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
   ISP.  Concretely, that ISP can decide to provision the enterprise
   network with:

   o  The same DOTS server for all network attachments.

   o  Distinct DOTS servers for each network attachment.  These DOTS
      servers need to coordinate when a mitigation action is received
      from the enterprise network.

   In both cases, DOTS agents enabled within the enterprise network MAY
   decide to select one or all network attachments to send DOTS
   mitigation requests.

6.  Security Considerations

   DOTS-related security considerations are discussed in Section 4 of
   [RFC8811].

   DOTS clients should control the information that they share with peer
   DOTS servers.  For example, if a DOTS client maintains DOTS
   associations with specific DOTS servers per interconnection link, the
   DOTS client should not leak information specific to a given link to
   DOTS servers not authorized to mitigate attacks received on that
   link.  Whether this constraint is relaxed is deployment specific and
   must be subject to explicit consent from the DOTS client domain
   administrator.

7.  IANA Considerations

   This document does not require any action from IANA.

8.  Acknowledgements

   Thanks to Roland Dobbins, Nik Teague, Jon Shallow, Dan Wing, and
   Christian Jacquenet for sharing their comments on the mailing list.

   Thanks to Kirill Kasavchenko for the comments.

9.  References

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9.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC6724]  Thaler, D., Ed., Draves, R., Matsumoto, A., and T. Chown,
              "Default Address Selection for Internet Protocol Version 6
              (IPv6)", RFC 6724, DOI 10.17487/RFC6724, September 2012,
              <https://www.rfc-editor.org/info/rfc6724>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

   [RFC8811]  Mortensen, A., Ed., Reddy.K, T., Ed., Andreasen, F.,
              Teague, N., and R. Compton, "DDoS Open Threat Signaling
              (DOTS) Architecture", RFC 8811, DOI 10.17487/RFC8811,
              August 2020, <https://www.rfc-editor.org/info/rfc8811>.

9.2.  Informative References

   [I-D.ietf-dots-use-cases]
              Dobbins, R., Migault, D., Moskowitz, R., Teague, N., Xia,
              L., and K. Nishizuka, "Use cases for DDoS Open Threat
              Signaling", draft-ietf-dots-use-cases-25 (work in
              progress), July 2020.

   [RFC3582]  Abley, J., Black, B., and V. Gill, "Goals for IPv6 Site-
              Multihoming Architectures", RFC 3582,
              DOI 10.17487/RFC3582, August 2003,
              <https://www.rfc-editor.org/info/rfc3582>.

   [RFC4116]  Abley, J., Lindqvist, K., Davies, E., Black, B., and V.
              Gill, "IPv4 Multihoming Practices and Limitations",
              RFC 4116, DOI 10.17487/RFC4116, July 2005,
              <https://www.rfc-editor.org/info/rfc4116>.

   [RFC4732]  Handley, M., Ed., Rescorla, E., Ed., and IAB, "Internet
              Denial-of-Service Considerations", RFC 4732,
              DOI 10.17487/RFC4732, December 2006,
              <https://www.rfc-editor.org/info/rfc4732>.

   [RFC7556]  Anipko, D., Ed., "Multiple Provisioning Domain
              Architecture", RFC 7556, DOI 10.17487/RFC7556, June 2015,
              <https://www.rfc-editor.org/info/rfc7556>.

Boucadair, et al.       Expires November 26, 2021              [Page 14]
Internet-Draft              DOTS Multihoming                    May 2021

   [RFC8043]  Sarikaya, B. and M. Boucadair, "Source-Address-Dependent
              Routing and Source Address Selection for IPv6 Hosts:
              Overview of the Problem Space", RFC 8043,
              DOI 10.17487/RFC8043, January 2017,
              <https://www.rfc-editor.org/info/rfc8043>.

   [RFC8782]  Reddy.K, T., Ed., Boucadair, M., Ed., Patil, P.,
              Mortensen, A., and N. Teague, "Distributed Denial-of-
              Service Open Threat Signaling (DOTS) Signal Channel
              Specification", RFC 8782, DOI 10.17487/RFC8782, May 2020,
              <https://www.rfc-editor.org/info/rfc8782>.

   [RFC8783]  Boucadair, M., Ed. and T. Reddy.K, Ed., "Distributed
              Denial-of-Service Open Threat Signaling (DOTS) Data
              Channel Specification", RFC 8783, DOI 10.17487/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

   Mohamed Boucadair
   Orange
   Rennes  35000
   France

   Email: mohamed.boucadair@orange.com

   Tirumaleswar Reddy
   McAfee, Inc.
   Embassy Golf Link Business Park
   Bangalore, Karnataka  560071
   India

   Email: TirumaleswarReddy_Konda@McAfee.com

   Wei Pan
   Huawei Technologies

   Email: william.panwei@huawei.com

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