Multi-homing Deployment Considerations for Distributed-Denial-of-Service Open Threat Signaling (DOTS)
draft-ietf-dots-multihoming-02

Network Working Group                                       M. Boucadair
Internet-Draft                                                    Orange
Intended status: Standards Track                                T. Reddy
Expires: January 23, 2020                                         McAfee
                                                                  W. Pan
                                                     Huawei Technologies
                                                           July 22, 2019


Multi-homing Deployment Considerations for Distributed-Denial-of-Service
                      Open Threat Signaling (DOTS)
                     draft-ietf-dots-multihoming-02

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

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   This Internet-Draft will expire on January 23, 2020.

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   document authors.  All rights reserved.

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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 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  . . . . . . . . . . . . . . . . . . . . . . . . . .  11
     5.4.  Multi-Homed Enterprise: Single ISP  . . . . . . . . . . .  12
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  13
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  13
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  13
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  13
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  13
     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)
   [I-D.ietf-dots-architecture]architecture, 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 DOTS architecture is illustrated in Figure 1
   ([I-D.ietf-dots-architecture]):

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

                     Figure 1: Basic DOTS Architecture

   [I-D.ietf-dots-architecture] 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.

   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 [I-D.ietf-dots-signal-channel] and
   [I-D.ietf-dots-data-channel]; 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
   [I-D.ietf-dots-architecture] 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 sub-sections, 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
      (Customer Premises Equipment).

   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
      [I-D.boucadair-dots-server-discovery].  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).

      Editor's Note: The use of anycast addresses is to be consistently
      discussed.

5.  DOTS 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.





















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   +---------------------------+-------------------------+-------------+
   |          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

   These deployment schemes are further discussed in the following sub-
   sections.

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
   ([I-D.boucadair-dots-server-discovery]) using the DNS servers learned
   from the respective provisioning domain.  The DOTS client 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
   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 prefixes from which target
   prefixes and target IP addresses are derived.  This implies that if
   no appropriate DOTS server is found, the DOTS client must not send
   the mitigation request to any DOTS server.





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   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.

                                                +--+
                                     -----------|S1|
                                    /           +--+
                                   /
                                  /
                            +---+/
                            | C |
                            +---+\
                                  \
                                   \
                                    \           +--+
                                     -----------|S2|
                                                +--+

       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.





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   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 the same request to all its DOTS servers.

                                                   +--+
                                        -----------|S1|
                        +---+          /           +--+
                        | C1|----+    /
                        +---+    |   /
                    +---+      +-+-+/
                    | C3|------| G |
                    +---+      +-+-+\
                        +---+    |   \
                        | C2|----+    \
                        +---+          \           +--+
                                        -----------|S2|
                                                   +--+

    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
      [I-D.boucadair-dots-server-discovery] 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 the
   mitigation request for all its PI addresses/prefixes to all the DOTS
   servers.  The use of anycast addresses 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|--------+
                                   +--+

          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|
                         +--+      +--+      +--+


                    Figure 8: Single Homed DOTS Clients

   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 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 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.



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   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

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:

   1.  The same DOTS server for all network attachments.






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   2.  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
   [I-D.ietf-dots-architecture].

   TBD: In Home networks, if EST is used then how will the DOTS gateway
   (EST client) be provisioned with credentials for initial enrolment
   (see Section 2.2 in RFC 7030).

7.  IANA Considerations

   This document does not require any action from IANA.

8.  Acknowledgements

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

   Thanks to Kirill Kasavchenko for the comments.

9.  References

9.1.  Normative References

   [I-D.ietf-dots-architecture]
              Mortensen, A., K, R., Andreasen, F., Teague, N., and R.
              Compton, "Distributed-Denial-of-Service Open Threat
              Signaling (DOTS) Architecture", draft-ietf-dots-
              architecture-14 (work in progress), May 2019.

   [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>.



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   [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>.

9.2.  Informative References

   [I-D.boucadair-dots-server-discovery]
              Boucadair, M., K, R., and P. Patil, "Distributed-Denial-
              of-Service Open Threat Signaling (DOTS) Server Discovery",
              draft-boucadair-dots-server-discovery-05 (work in
              progress), October 2018.

   [I-D.ietf-dots-data-channel]
              Boucadair, M. and R. K, "Distributed Denial-of-Service
              Open Threat Signaling (DOTS) Data Channel Specification",
              draft-ietf-dots-data-channel-30 (work in progress), July
              2019.

   [I-D.ietf-dots-signal-channel]
              K, R., Boucadair, M., Patil, P., Mortensen, A., and N.
              Teague, "Distributed Denial-of-Service Open Threat
              Signaling (DOTS) Signal Channel Specification", draft-
              ietf-dots-signal-channel-35 (work in progress), July 2019.

   [I-D.ietf-dots-use-cases]
              Dobbins, R., Migault, D., Fouant, S., Moskowitz, R.,
              Teague, N., Xia, L., and K. Nishizuka, "Use cases for DDoS
              Open Threat Signaling", draft-ietf-dots-use-cases-18 (work
              in progress), July 2019.

   [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>.



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Internet-Draft              DOTS Multihoming                   July 2019


   [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>.

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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