



DOTS                                                          Y. Hayashi
Internet-Draft                                                       NTT
Intended status: Informational                                   M. Chen
Expires: 26 April 2023                                            Li. Su
                                                                    CMCC
                                                         23 October 2022


       Use Cases for DDoS Open Threat Signaling (DOTS) Telemetry
                 draft-ietf-dots-telemetry-use-cases-15

Abstract

   DDoS Open Threat Signaling (DOTS) Telemetry enriches the base DOTS
   protocols to assist the mitigator in using efficient DDoS attack
   mitigation techniques in a network.  This document presents sample
   use cases for DOTS Telemetry.  It discusses what components are
   deployed in the network, how they cooperate, and what information is
   exchanged to effectively use these techniques.

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
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on 26 April 2023.

Copyright Notice

   Copyright (c) 2022 IETF Trust and the persons identified as the
   document authors.  All rights reserved.










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   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents (https://trustee.ietf.org/
   license-info) in effect on the date of publication of this document.
   Please review these documents carefully, as they describe your rights
   and restrictions with respect to this document.  Code Components
   extracted from this document must include Revised BSD License text as
   described in Section 4.e of the Trust Legal Provisions and are
   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Telemetry Use Cases . . . . . . . . . . . . . . . . . . . . .   3
     3.1.  Mitigation Resources Assignment . . . . . . . . . . . . .   3
       3.1.1.  Mitigating Attack Flow of Top-talker
               Preferentially  . . . . . . . . . . . . . . . . . . .   4
       3.1.2.  DMS Selection for Mitigation  . . . . . . . . . . . .   6
       3.1.3.  Path Selection for Redirection  . . . . . . . . . . .   9
       3.1.4.  Short but Extreme Volumetric Attack Mitigation  . . .  11
       3.1.5.  Selecting Mitigation Technique Based on Attack
               Type  . . . . . . . . . . . . . . . . . . . . . . . .  14
     3.2.  Detailed DDoS Mitigation Report . . . . . . . . . . . . .  18
     3.3.  Tuning Mitigation Resources . . . . . . . . . . . . . . .  21
       3.3.1.  Supervised Machine Learning of Flow Collector . . . .  21
       3.3.2.  Unsupervised Machine Learning of Flow Collector . . .  24
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .  26
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  26
   6.  Acknowledgement . . . . . . . . . . . . . . . . . . . . . . .  26
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  26
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .  26
     7.2.  Informative References  . . . . . . . . . . . . . . . . .  26
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  28

1.  Introduction

   Distributed Denial-of-Service (DDoS) attacks, such as volumetric
   attacks and resource-consumption attacks, are critical threats to be
   handled by service providers.  When such DDoS attacks occur, service
   providers have to mitigate them immediately to protect or recover
   their services.

   Therefore, for service providers to immediately protect their network
   services from DDoS attacks, DDoS mitigation needs to be highly
   automated.  To that aim, multivendor components involved in DDoS
   attack detection and mitigation should cooperate and support standard
   interfaces.




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   DDoS Open Threat Signaling (DOTS) is a set of protocols for real-time
   signaling, threat-handling requests, and data filtering between the
   multivendor elements [RFC9132][RFC8783].  DOTS Telemetry enriches the
   DOTS protocols with various telemetry attributes allowing optimal
   DDoS attack mitigation [RFC9244].  This document presents sample use
   cases for DOTS Telemetry which makes concrete overview and purpose
   described in [RFC9244].  This document also presents what components
   are deployed in the network, how they cooperate, and what information
   is exchanged to effectively use attack-mitigation techniques.

2.  Terminology

   The readers should be familiar with the terms defined in [RFC8612],
   [RFC8903] and [RFC9244].

   In addition, this document uses the following terms:

   Top-talker:  A list of attack sources that are involved in an attack
      and which are generating an important part of the attack traffic.

   Supervised Machine Learning:  A machine-learning technique in which
      labeled data is used to train the algorithms (the input and output
      data are known).

   Unsupervised Machine Learning:  A machine learning technique in which
      unlabeled data is used to train the algorithms (the data has no
      historical labels).

3.  Telemetry Use Cases

   This section describes DOTS telemetry use cases that use attributes
   included in the DOTS telemetry specification [RFC9244].

   The following subsections assume that once the DOTS signal channel is
   established, DOTS clients proceed with the telemetry setup
   configuration as detailed in Section 7 of [RFC9244].  The following
   telemetry parameters are used:

   *  'measurement-interval' to define the period during which
      percentiles are computed.

   *  'measurement-sample' to define the time distribution for measuring
      values that are used to compute percentiles.

3.1.  Mitigation Resources Assignment






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3.1.1.  Mitigating Attack Flow of Top-talker Preferentially

   Some transit providers have to mitigate large-scale DDoS attacks by
   using DDoS Mitigation Systems (DMSes) with limited resources, which
   are already deployed in their network.  For example, recently
   reported large DDoS attacks exceeded several Tbps.  [DOTS_Overview]

   This use case enables transit providers to use their DMS efficiently
   under volume-based DDoS attacks whose volume is more than the
   available capacity of the DMS.  To enable this, the attack traffic of
   top-talkers is redirected to the DMS preferentially by cooperation
   among forwarding nodes, flow collectors, and orchestrators.

   Figure 1 gives an overview of this use case.  Figure 2 provides an
   example of a DOTS telemetry message body that is used to signal top-
   talkers (2001:db8:1::/48 and 2001:db8:2::/48).

 (Internet Transit Provider)

                +-----------+      +--------------+ SNMP or YANG/NETCONF
         IPFIX +-----------+| DOTS |              |<---
           --->| Flow      ||C<-->S| Orchestrator | BGP Flowspec
               | collector |+      |              |--->   (Redirect)
               +-----------+       +--------------+

                          +-------------+
                   IPFIX +-------------+| BGP Flowspec (Redirect)
                     <---| Forwarding  ||<---
                         |    nodes    ||
                         |             ||           DDoS Attack
 [ Target(s) ]<==========================================
                         |    ++=========================[top-talker]
                         |    || ++======================[top-talker]
                         +----|| ||---+
                              || ||
                              || ||
                              |/ |/
                         +----x--x----+
                         | DDoS       | SNMP or YANG/NETCONF
                         | mitigation |<---
                         | system     |
                         +------------+

 * C is for DOTS client functionality
 * S is for DOTS server functionality

 Figure 1: Mitigating DDoS Attack Flow of Top-talkers Preferentially




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   {
     "ietf-dots-telemetry:telemetry": {
       "pre-or-ongoing-mitigation": [
         {
           "target": {
             "target-prefix": [
               "2001:db8::1/128"
             ]
           },
           "total-attack-traffic-protocol": [
             {
               "protocol": 17,
               "unit": "megabit-ps",
               "mid-percentile-g": "900"
             }
           ],
           "attack-detail": [
             {
               "vendor-id": 32473,
               "attack-id": 77,
               "start-time": "1645057211",
               "attack-severity": "high",
               "top-talker":{
                 "talker": [
                   {
                     "source-prefix": "2001:db8:1::/48",
                     "total-attack-traffic": [
                       {
                         "unit": "megabit-ps",
                         "mid-percentile-g": "100"
                       }
                     ]
                   },
                   {
                     "source-prefix": "2001:db8:2::/48",
                     "total-attack-traffic": [
                       {
                         "unit": "megabit-ps",
                         "mid-percentile-g": "90"
                       }
                     ]
                   }
                 ]
               }
             }
           ]
         }
       ]



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     }
   }

   Figure 2: An Example of Message Body to Signal Top-Talkers

   The forwarding nodes send traffic statistics to the flow collectors,
   e.g., using IP Flow Information Export (IPFIX) [RFC7011].  When DDoS
   attacks occur, the flow collectors identify the attack traffic and
   send information about the top-talkers to the orchestrator using the
   "target-prefix" and "top-talkers" DOTS telemetry attributes.  The
   orchestrator then checks the available capacity of the DMSes by using
   a network management protocol, such as Simple Network Management
   Protocol (SNMP) [RFC3413] or YANG with Network Configuration Protocol
   (YANG/NETCONF) [RFC7950].  After that, the orchestrator orders the
   forwarding nodes to redirect as much of the top-talker's traffic to
   each DMS as that DMS can handle by dissemination of Flow
   Specifications using tools such as Border Gateway Protocol
   Dissemination of Flow Specification Rules (BGP Flowspec) [RFC8955].

   The flow collector implements a DOTS client while the orchestrator
   implements a DOTS server.

3.1.2.  DMS Selection for Mitigation

   Transit providers can deploy their DMSes in clusters.  Then, they can
   select the DMS to be used to mitigate a DDoS attack at the time of an
   attack.

   This use case enables transit providers to select a DMS with
   sufficient capacity for mitigation based on the volume of the attack
   traffic and the capacity of a DMS.  Figure 3 gives an overview of
   this use case.  Figure 4 provides an example of a DOTS telemetry
   message body that is used to signal various attack traffic
   percentiles.

















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(Internet Transit Provider)

               +-----------+      +--------------+ SNMP or YANG/NETCONF
        IPFIX +-----------+| DOTS |              |<---
          --->| Flow      ||C<-->S| Orchestrator | BGP (Redirect)
              | collector |+      |              |--->
              +-----------+       +--------------+

                         +------------+
                  IPFIX +------------+| BGP (Redirect)
                    <---| Forwarding ||<---
                        |    nodes   ||
                        |            ||     DDoS Attack
[Target A]              | ++=================== [Destined for Target A]
[Target B]              | ||  ++=============== [Destined for Target B]
                        +-||--||-----+
                          ||  ||
                    ++====++  ||  (congested DMS)
                    ||        ||  +-----------+
                    ||        |/  |      DMS3 |
                    ||  +-----x------+        |<--- SNMP or YANG/NETCONF
                    |/  |       DMS2 |--------+
                 +--x---------+      |<--- SNMP or YANG/NETCONF
                 |       DMS1 |------+
                 |            |<--- SNMP or YANG/NETCONF
                 +------------+

* C is for DOTS client functionality
* S is for DOTS server functionality

Figure 3: DMS Selection for Mitigation




















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   {
     "ietf-dots-telemetry:telemetry": {
       "pre-or-ongoing-mitigation": [
         {
           "target": {
             "target-prefix": [
               "192.0.2.3/32"
             ]
           },
           "total-attack-traffic": [
             {
               "unit": "megabit-ps",
               "low-percentile-g": "600",
               "mid-percentile-g": "800",
               "high-percentile-g": "1000",
               "peak-g":"1100",
               "current-g":"700"
             }
           ]
         }
       ]
     }
   }

   Figure 4: Example of Message Body with Total Attack Traffic

   The forwarding nodes send traffic statistics to the flow collectors,
   e.g., using IPFIX.  When DDoS attacks occur, the flow collectors
   identify the attack traffic and send information about the attack
   traffic volume to the orchestrator by using the "target-prefix" and
   "total-attack-traffic" DOTS telemetry attributes.  The orchestrator
   then checks the available capacity of the DMSes by using a network
   management protocol, such as Simple Network Management Protocol
   (SNMP) [RFC3413] or YANG with Network Configuration Protocol (YANG/
   NETCONF) [RFC7950].  After that, the orchestrator selects a DMS with
   sufficient capacity to which attack traffic should be redirected.
   For example, a simple DMS selection algorithm is to choose a DMS
   whose available capacity is greater than the "peak-g" attribute
   indicated in the DOTS telemetry message.  The orchestrator orders the
   appropriate forwarding nodes to redirect the attack traffic to the
   DMS relying upon routing policies, such as BGP [RFC4271].

   The detailed DMS selection algorithm is out of the scope of this
   document.

   The flow collector implements a DOTS client while the orchestrator
   implements a DOTS server.




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3.1.3.  Path Selection for Redirection

   A transit provider network has multiple paths to convey attack
   traffic to a DMS.  In such a network, the attack traffic can be
   conveyed while avoiding congested links by adequately selecting an
   available path.

   This use case enables transit providers to select a path with
   sufficient bandwidth for redirecting attack traffic to a DMS
   according to the bandwidth of the attack traffic and total traffic.
   Figure 5 gives an overview of this use case.  Figure 6 provides an
   example of a DOTS telemetry message body that is used to signal
   various attack traffic percentiles and total traffic percentiles.

 (Internet Transit Provider)

           +-----------+      +--------------+ DOTS
          +-----------+|      |              |S<---
    IPFIX | Flow      || DOTS | Orchestrator |
       -->| collector ||C<-->S|              | BGP Flowspec (Redirect)
          |           |+      |              |--->
          +-----------+       +--------------+

                DOTS +------------+  DOTS +------------+ IPFIX
                --->C| Forwarding |  --->C| Forwarding |--->
        BGP Flowspec |   node     |       |   node     |
      (Redirect) --->|            |       |            |  DDoS Attack
 [Target]            |       ++====================================
                     +-------||---+       +------------+
                             ||              /
                             ||             / (congested link)
                             ||            /
                     DOTS  +-||----------------+ BGP Flowspec (Redirect)
                      --->C| ||  Forwarding    |<---
                           | ++===  node       |
                           +----||-------------+
                                |/
                             +--x-----------+
                             |     DMS      |
                             +--------------+

 * C is for DOTS client functionality
 * S is for DOTS server functionality

 Figure 5: Path Selection for Redirection






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   {
     "ietf-dots-telemetry:telemetry": {
       "pre-or-ongoing-mitigation": [
         {
           "target": {
             "target-prefix": [
               "2001:db8::1/128"
             ]
           },
           "total-traffic": [
             {
               "unit": "megabit-ps",
               "mid-percentile-g": "1300",
               "peak-g": "800"
              }
           ],
           "total-attack-traffic": [
             {
               "unit": "megabit-ps",
               "low-percentile-g": "600",
               "mid-percentile-g": "800",
               "high-percentile-g": "1000",
               "peak-g": "1100",
               "current-g": "700"
              }
           ]
         }
       ]
     }
   }

   Figure 6: An Example of Message Body with Total Attack
                   Traffic and Total Traffic


















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   The forwarding nodes send traffic statistics to the flow collectors,
   e.g., using IPFIX.  When DDoS attacks occur, the flow collectors
   identify attack traffic and send information about the attack traffic
   volume to the orchestrator by using "target-prefix" and "total-
   attack-traffic" DOTS telemetry attributes.  The underlying forwarding
   nodes send the volume on the total traffic passing the node to the
   orchestrator by using "total-traffic" telemetry attributes.  The
   orchestrator then selects a path with sufficient bandwidth to which
   attack-traffic flow should be redirected.  For example, the simple
   algorithm of the selection is to choose a path whose available
   capacity is greater than the "peak-g" attribute that was indicated in
   a DOTS telemetry message.  After that, the orchestrator orders the
   appropriate forwarding nodes to redirect the attack traffic to the
   DMS by dissemination of Flow Specifications using tools such as
   Border Gateway Protocol Dissemination of Flow Specification Rules
   (BGP Flowspec) [RFC8955].

   The detailed path selection algorithm is out of the scope of this
   document.

   The flow collector and forwarding nodes implement a DOTS client while
   the orchestrator implements a DOTS server.

3.1.4.  Short but Extreme Volumetric Attack Mitigation

   Short but extreme volumetric attacks, such as pulse wave DDoS
   attacks, are threats to Internet transit provider networks.  These
   attacks start from zero and go to maximum values in a very short time
   span, then go back to zero, and then back to maximum, repeating in
   continuous cycles at short intervals.  It is difficult for the
   transit providers to mitigate such an attack with their DMSes using a
   redirecting attack flows because this may cause route flapping in the
   network.  The practical way to mitigate short but extreme volumetric
   attacks is to offload mitigation actions to a forwarding node.

   This use case enables transit providers to mitigate short but extreme
   volumetric attacks.  Furthermore, the aim is to estimate the network-
   access success rate based on the bandwidth of the attack traffic.
   Figure 7 gives an overview of this use case.  Figure 8 provides an
   example of a DOTS telemetry message body that is used to signal total
   pipe capacity.  Figure 9 provides an example of a DOTS telemetry
   message body that is used to signal various attack traffic
   percentiles and total traffic percentiles.








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(Internet Transit Provider)

            +------------+       +----------------+
            | Network    |  DOTS | Administrative |
Alert ----->| Management |C<--->S| System         | BGP Flowspec (Rate-Limit)
            | System     |       |                |--->
            +------------+       +----------------+

              +------------+     +------------+ BGP Flowspec (Rate-Limit X bps)
              | Forwarding |     | Forwarding |<---
              |   node     |     |   node     |
        Link1 |            |     |            | DDoS & Normal traffic
[Target]<------------------------------------================
Pipe          +------------+     +------------+  Attack Traffic
Capability                                       Bandwidth
  X bps                                           Y bps

                    Network access success rate
                           X / (X + Y)

* C is for DOTS client functionality
* S is for DOTS server functionality

Figure 7: Short but Extreme Volumetric Attack Mitigation


     {
       "ietf-dots-telemetry:telemetry-setup": {
         "telemetry": [
           {
             "total-pipe-capacity": [
               {
                 "link-id": "link1",
                 "capacity": "1000",
                 "unit": "megabit-ps"
               }
             ]
           }
         ]
       }
     }
   Figure 8: Example of Message Body with Total Pipe Capacity









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   {
     "ietf-dots-telemetry:telemetry": {
       "pre-or-ongoing-mitigation": [
         {
           "target": {
             "target-prefix": [
               "2001:db8::1/128"
             ]
           },
           "total-traffic": [
             {
               "unit": "megabit-ps",
               "mid-percentile-g": "800",
               "peak-g": "1300"
              }
           ],
           "total-attack-traffic": [
             {
               "unit": "megabit-ps",
               "low-percentile-g": "200",
               "mid-percentile-g": "400",
               "high-percentile-g": "500",
               "peak-g": "600",
               "current-g": "400"
             }
           ]
          }
       ]
     }
   }

   Figure 9: Example of Message Body with Total Attack Traffic,
                       and Total Traffic

   When DDoS attacks occur, the network management system receives
   alerts.  Then, it sends the target IP address(es) and volume of the
   DDoS attack traffic to the administrative system by using the
   "target-prefix" and "total-attack-traffic" DOTS telemetry attributes.
   After that, the administrative system orders relevant forwarding
   nodes to carry out rate-limiting of all traffic destined to the
   target based on the pipe capability by the dissemination of the Flow
   Specifications using tools such as Border Gateway Protocol
   Dissemination of Flow Specification Rules (BGP Flowspec) [RFC8955].
   In addition, the administrative system estimates the network-access
   success rate of the target, which is calculated by (total-pipe-
   capability / (total-pipe-capability + total-attack-traffic)).





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   Note that total pipe capability information can be gathered by
   telemetry setup in advance (Section 7.2 of [RFC9244]).

   The network management system implements a DOTS client while the
   administrative system implements a DOTS server.

3.1.5.  Selecting Mitigation Technique Based on Attack Type

   Some volumetric attacks, such as DNS amplification attacks, can be
   detected with high accuracy by checking the Layer 3 or Layer 4
   information of attack packets.  These attacks can be detected and
   mitigated through cooperation among forwarding nodes and flow
   collectors by using IPFIX.  It may also be necessary to inspect the
   Layer 7 information of suspicious packets to detect attacks such as
   DNS Water Torture Attacks [DNS_Water_Torture_Attack].  To carry out
   the DNS water torture attack, an attacker commands a botnet to make
   thousands of DNS requests for fake subdomains against an
   Authoritative Name Server.  Such attack traffic should be detected
   and mitigated at the DMS.

   This use case enables transit providers to select a mitigation
   technique based on the type of attack traffic: amplification attack
   or not.  To use such a technique, the attack traffic is blocked by
   forwarding nodes or redirected to a DMS based on the attack type
   through cooperation among forwarding nodes, flow collectors, and an
   orchestrator.

   Figure 10 gives an overview of this use case.  Figure 11 provides an
   example of attack mappings that are shared by using the DOTS data
   channel in advance.  Figure 12 provides an example of a DOTS
   telemetry message body that is used to signal various attack traffic
   percentiles, total traffic percentiles, total attack connection, and
   attack type.

   The example in Figure 11 uses the folding defined in [RFC8792] for
   long lines.















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     (Internet Transit Provider)

              +-----------+ DOTS +--------------+
             +-----------+|<---->|              | BGP (Redirect)
       IPFIX | Flow      ||C    S| Orchestrator | BGP Flowspec (Drop)
         --->| collector |+      |              |--->
             +-----------+       +--------------+

                         +------------+ BGP (Redirect)
                  IPFIX +------------+| BGP Flowspec (Drop)
                    <---| Forwarding ||<---
                        |    nodes   ||              DDoS Attack
                        |     ++=====||================
                        |     ||     ||x<==============[DNS Amp]
                        |     ||     |+x<==============[NTP Amp]
                        +-----||-----+
                              ||
                              |/
                        +-----x------+
                        | DDoS       |
                        | mitigation |
                        | system     |
                        +------------+

     * C is for DOTS client functionality
     * S is for DOTS server functionality
     * DNS Amp: DNS Amplification
     * NTP Amp: NTP Amplification

   Figure 10: DDoS Mitigation Based on Attack Type





















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   =============== NOTE: '\' line wrapping per RFC 8792 ================

   {
     "ietf-dots-mapping:vendor-mapping": {
       "vendor": [
         {
           "vendor-id": 32473,
           "vendor-name": "mitigator-c",
           "last-updated": "1629898958",
           "attack-mapping": [
             {
               "attack-id": 77,
               "attack-description": "DNS amplification Attack: \
   This attack is a type of reflection attack in which attackers \
   spoof a target's IP address. The attackers abuse vulnerabilities \
   in DNS servers to turn small queries into larger payloads."
             },
             {
               "attack-id": 92,
               "attack-description":"NTP amplification Attack: \
   This attack is a type of reflection attack in which attackers \
   spoof a target's IP address. The attackers abuse vulnerabilities \
   in NTP servers to turn small queries into larger payloads."
             }
           ]
         }
       ]
     }
   }

   Figure 11: Example of Message Body with Attack Mappings

  {
    "ietf-dots-telemetry:telemetry": {
      "pre-or-ongoing-mitigation": [
        {
          "target": {
            "target-prefix": [
              "2001:db8::1/128"
            ]
          },
          "total-attack-traffic": [
            {
              "unit": "megabit-ps",
              "low-percentile-g": "600",
              "mid-percentile-g": "800",
              "high-percentile-g": "1000",
              "peak-g": "1100",



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              "current-g": "700"
             }
          ],
          "total-attack-traffic-protocol": [
            {
              "protocol": 17,
              "unit": "megabit-ps",
              "mid-percentile-g": "500"
            },
            {
              "protocol": 15,
              "unit": "megabit-ps",
              "mid-percentile-g": "200"
            }
          ],
          "total-attack-connection": [
          {
             "mid-percentile-l": [
              {
                "protocol": 15,
                "connection": 200
              }
             ],
             "high-percentile-l": [
              {
                "protocol": 17,
                "connection": 300
              }
             ]
          }
          ],
          "attack-detail": [
            {
              "vendor-id": 32473,
              "attack-id": 77,
              "start-time": "1641169211",
              "attack-severity": "high"
            },
            {
              "vendor-id": 32473,
              "attack-id": 92,
              "start-time": "1641172809",
              "attack-severity": "high"
            }
          ]
        }
      ]
    }



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  }

  Figure 12: Example of Message Body with Total Attack Traffic,
  Total Attack Traffic Protocol, Total Attack Connection and Attack Type

   Attack mappings are shared by using the DOTS data channel in advance
   (Section 8.1.6 of [RFC9244]).  The forwarding nodes send traffic
   statistics to the flow collectors, e.g., using IPFIX.  When DDoS
   attacks occur, the flow collectors identify attack traffic and send
   attack type information to the orchestrator by using "vendor-id" and
   "attack-id" telemetry attributes.  The orchestrator then resolves
   abused port numbers and orders relevant forwarding nodes to block the
   amplification attack traffic flow by dissemination of Flow
   Specifications using tools such as Border Gateway Protocol
   Dissemination of Flow Specification Rules (BGP Flowspec) [RFC8955].
   Also, the orchestrator orders relevant forwarding nodes to redirect
   other traffic than the amplification attack traffic by using a
   routing protocol, such as BGP [RFC4271].

   The flow collector implements a DOTS client while the orchestrator
   implements a DOTS server.

3.2.  Detailed DDoS Mitigation Report

   It is possible for the transit provider to add value to the DDoS
   mitigation service by reporting ongoing and detailed DDoS
   countermeasure status to the enterprise network.  In addition, it is
   possible for the transit provider to know whether the DDoS
   countermeasure is effective or not by receiving reports from the
   enterprise network.

   This use case enables sharing of information about ongoing DDoS
   countermeasures between the transit provider and the enterprise
   network mutually.  Figure 13 gives an overview of this use case.
   Figure 14 provides an example of a DOTS telemetry message body that
   is used to signal total pipe capacity from the enterprise network
   administrator to the orchestrator in the ISP.  Figure 15 provides an
   example of a DOTS telemetry message body that is used to signal
   various total traffic percentiles, total attack traffic percentiles,
   and attack details from the orchestrator to the network.











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     +------------------+       +------------------------+
     | Enterprise       |       |    Upstream            |
     | Network          |       |    Internet Transit    |
     |  +------------+  |       |    Provider            |
     |  | Network    |C |       |   S+--------------+    |
     |  | admini-    |<-----DOTS---->| Orchestrator |    |
     |  | strator    |  |       |    +--------------+    |
     |  +------------+  |       |         C ^            |
     |                  |       |           | DOTS       |
     |                  |       |         S v            |
     |                  |       |    +---------------+ DDoS Attack
     |                  |       |    |      DMS      |+=======
     |                  |       |    +---------------+   |
     |                  |       |           || Clean     |
     |                  |       |           |/ Traffic   |
     |  +---------+     |       |   +---------------+    |
     |  | DDoS    |     |       |   | Forwarding    | Normal Traffic
     |  | Target  |<================| Node          |========
     |  +---------+     | Link1 |   +---------------+    |
     +------------------+       +------------------------+

   * C is for DOTS client functionality
   * S is for DOTS server functionality

   Figure 13: Detailed DDoS Mitigation Report

   {
     "ietf-dots-telemetry:telemetry-setup": {
       "telemetry": [
         {
           "total-pipe-capacity": [
             {
               "link-id": "link1",
               "capacity": "1000",
               "unit": "megabit-ps"
             }
           ]
         }
       ]
     }
   }
   Figure 14: An Example of Message Body with Total Pipe Capacity









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   {
     "ietf-dots-telemetry:telemetry": {
       "pre-or-ongoing-mitigation": [
         {
           "tmid": 567,
           "target": {
             "target-prefix": [
               "2001:db8::1/128"
             ]
           },
           "target-protocol": [
             17
           ],
           "total-traffic": [
             {
               "unit": "megabit-ps",
               "mid-percentile-g": "800"
             }
           ],
           "total-attack-traffic": [
             {
               "unit": "megabit-ps",
               "mid-percentile-g": "100"
             }
           ],
           "attack-detail": [
             {
               "vendor-id": 32473,
               "attack-id": 77,
               "start-time": "1644819611",
               "attack-severity": "high"
             }
           ]
         }
       ]
     }
   }

   Figure 15: An Example of Message Body with Total Traffic,
        Total Attack Traffic Protocol, and Attack Detail

   The network management system in the enterprise network reports
   limits of incoming traffic volume from the transit provider to the
   orchestrator in the transit provider in advance.  It is reported by
   using the "total-pipe-capacity" telemetry attribute in the DOTS
   telemetry setup.





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   When DDoS attacks occur, DDoS mitigation orchestration [RFC8903] is
   carried out in the transit provider.  Then, the DDoS mitigation
   systems report the status of DDoS countermeasures to the orchestrator
   by sending "attack-detail" telemetry attributes.  After that, the
   orchestrator integrates the reports from the DDoS mitigation systems,
   while removing duplicate contents, and sends the integrated report to
   a network administrator by using DOTS telemetry periodically.

   During the DDoS mitigation, the orchestrator in the transit provider
   retrieves link congestion status from the network manager in the
   enterprise network by using "total-traffic" telemetry attributes.
   Then, the orchestrator checks whether the DDoS countermeasures are
   effective or not by comparing the "total-traffic" and the "total-
   pipe-capacity" attributes.

   The DMS implements a DOTS server while the orchestrator behaves as a
   DOTS client and a server in the transit provider.  In addition, the
   network administrator implements a DOTS client.

3.3.  Tuning Mitigation Resources

3.3.1.  Supervised Machine Learning of Flow Collector

   DDoS detection based on tools, such as IPFIX, is a lighter weight
   method of detecting DDoS attacks than DMSes in Internet transit
   provider networks.  DDoS detection based on the DMSes is a more
   accurate method for detecting attack traffic than flow monitoring.

   The aim of this use case is to increase flow collectors' detection
   accuracy by carrying out supervised machine-learning techniques
   according to attack detail reported by the DMSes.  To use such a
   technique, forwarding nodes, flow collectors, and a DMS should
   cooperate.  Figure 16 gives an overview of this use case.  Figure 17
   provides an example of a DOTS telemetry message body that is used to
   signal various total attack traffic percentiles and attack detail.
















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                                   +-----------+
                                  +-----------+| DOTS
                            IPFIX | Flow      ||S<---
                              --->| collector ||
                                  +-----------++

                                   +------------+
                            IPFIX +------------+|
                              <---| Forwarding ||
                                  |    nodes   ||           DDoS Attack
    [ Target ]                    |   ++==============================
                                  |   || ++===========================
                                  |   || || ++========================
                                  +---||-|| ||-+
                                      || || ||
                                      |/ |/ |/
                            DOTS  +---X--X--X--+
                             --->C| DDoS       |
                                  | mitigation |
                                  | system     |
                                  +------------+

           * C is for DOTS client functionality
           * S is for DOTS server functionality

   Figure 16: Training Supervised Machine Learning of Flow Collectors

























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   {
     "ietf-dots-telemetry:telemetry": {
       "pre-or-ongoing-mitigation": [
         {
           "target": {
             "target-prefix": [
               "2001:db8::1/128"
             ]
           },
           "attack-detail": [
             {
               "vendor-id": 32473,
               "attack-id": 77,
               "start-time": "1634192411",
               "attack-severity": "high",
               "top-talker": {
                 "talker": [
                   {
                     "source-prefix": "2001:db8::2/127"
                   }
                 ]
               }
             }
           ]
         }
       ]
     }
   }

   Figure 17: An Example of Message Body with Attack Type
                   and top-talkers

   The forwarding nodes send traffic statistics to the flow collectors,
   e.g., using IPFIX.  When DDoS attacks occur, DDoS mitigation
   orchestration is carried out (as per Section 3.3 of [RFC8903]) and
   the DMS mitigates all attack traffic destined for a target.  The DDoS
   mitigation system reports the "vendor-id", "attack-id", and "top-
   talker" telemetry attributes to a flow collector.

   After mitigating a DDoS attack, the flow collector attaches outputs
   of the DMS as labels to the statistics of traffic flow of top-
   talkers.  The outputs, for example, are the "attack-id" telemetry
   attributes.  The flow collector then carries out supervised machine
   learning to increase its detection accuracy, setting the statistics
   as an explanatory variable and setting the labels as an objective
   variable.





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   The DMS implements a DOTS client while the flow collector implements
   a DOTS server.

3.3.2.  Unsupervised Machine Learning of Flow Collector

   DMSes can detect DDoS attack traffic, which means DMSes can also
   identify clean traffic.  This use case supports unsupervised machine-
   learning for anomaly detection according to a baseline reported by
   the DMSes.  To use such a technique, forwarding nodes, flow
   collectors, and a DMS should cooperate.  Figure 18 gives an overview
   of this use case.  Figure 19 provides an example of a DOTS telemetry
   message body that is used to signal baseline.

                                 +-----------+
                                +-----------+|
                           DOTS | Flow      ||
                           --->S| collector ||
                                +-----------++

                                 +------------+
                                +------------+|
                                | Forwarding ||
                                |    nodes   ||             Traffic
   [ Destination ] <== =============++==============================
                                |   ||       ||
                                |   ||       |+
                                +---||-------+
                                    ||
                                    |/
                          DOTS  +---X--------+
                           --->C| DDoS       |
                                | mitigation |
                                | system     |
                                +------------+

         * C is for DOTS client functionality
         * S is for DOTS server functionality

   Figure 18: Training Unsupervised Machine Learning of Flow Collectors












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     {
       "ietf-dots-telemetry:telemetry-setup": {
         "telemetry": [
           {
             "baseline": [
               {
                 "id": 1,
                 "target-prefix": [
                   "2001:db8:6401::1/128"
                 ],
                 "target-port-range": [
                   {
                     "lower-port": "53"
                   }
                 ],
                 "target-protocol": [
                   17
                 ],
                 "total-traffic-normal": [
                   {
                     "unit": "megabit-ps",
                     "low-percentile-g": "30",
                     "mid-percentile-g": "50",
                     "high-percentile-g": "60",
                     "peak-g": "70"
                   }
                 ]
               }
             ]
           }
         ]
       }
     }

   Figure 19: An Example of Message Body with Traffic Baseline

   The forwarding nodes carry out traffic mirroring to copy the traffic
   destined an IP address and to monitor the traffic by a DMS.  The DMS
   then identifies "clean" traffic and reports the baseline attributes
   to the flow collector by using DOTS telemetry.

   The flow collector then carries out unsupervised machine learning to
   be able to carry out anomaly detection.

   The DMS implements a DOTS client while the flow collector implements
   a DOTS server.





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4.  Security Considerations

   DOTS telemetry security considerations are discussed in Section 14 of
   [RFC9244].  These considerations apply for the communication
   interfaces where DOTS is used.

   Some use cases involve controllers, orchestrators, and programmable
   interfaces.  These interfaces can be misused by misbehaving nodes to
   further exacerbate DDoS attacks.  The considerations are for end-to-
   end systems for DoS mitigation, so the mechanics are outside the
   scope of DOTS protocols.  Section 5 of [RFC7149] discusses some
   generic security considerations to take into account in such contexts
   (e.g., reliable access control).  Specific security measures depend
   on the actual mechanism used to control underlying forwarding nodes
   and other controlled elements.  For example, Section 13 of [RFC8955]
   discusses security considerations that are relevant to BGP Flowspec.
   IPFIX-specific considerations are discussed in Section 11 of
   [RFC7011].

5.  IANA Considerations

   This document does not require any action from IANA.

6.  Acknowledgement

   The authors would like to thank Mohamed Boucadair and Valery Smyslov
   for their valuable feedback.

   Thanks to Paul Wouters for the detailed AD review.

   Many thanks to Donald Eastlake, Phillip Hallam-Baker, Sean Turner,
   and Peter Yee for the AD review.

   Thanks to Lars Eggert, Murray Kucherawy, Roman Danyliw, Robert
   Wiltonm, and Eric Vyncke for the IESG review.

7.  References

7.1.  Normative References

   [RFC9244]  Boucadair, M., Ed., Reddy.K, T., Ed., Doron, E., Chen, M.,
              and J. Shallow, "Distributed Denial-of-Service Open Threat
              Signaling (DOTS) Telemetry", RFC 9244,
              DOI 10.17487/RFC9244, June 2022,
              <https://www.rfc-editor.org/info/rfc9244>.

7.2.  Informative References




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   [DNS_Water_Torture_Attack]
              Xi, L., "A Large Scale Analysis of DNS Water Torture
              Attack", DOI 10.1145/3297156.3297272, December 2018,
              <https://dl.acm.org/doi/10.1145/3297156.3297272>.

   [DOTS_Overview]
              Reddy, T. and M. Boucadair, "DOTS Overview (RFCs 8782,
              8783)", July 2020,
              <https://datatracker.ietf.org/meeting/108/materials/
              slides-108-saag-dots-overview-00>.

   [RFC3413]  Levi, D., Meyer, P., and B. Stewart, "Simple Network
              Management Protocol (SNMP) Applications", STD 62,
              RFC 3413, DOI 10.17487/RFC3413, December 2002,
              <https://www.rfc-editor.org/info/rfc3413>.

   [RFC4271]  Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A
              Border Gateway Protocol 4 (BGP-4)", RFC 4271,
              DOI 10.17487/RFC4271, January 2006,
              <https://www.rfc-editor.org/info/rfc4271>.

   [RFC7011]  Claise, B., Ed., Trammell, B., Ed., and P. Aitken,
              "Specification of the IP Flow Information Export (IPFIX)
              Protocol for the Exchange of Flow Information", STD 77,
              RFC 7011, DOI 10.17487/RFC7011, September 2013,
              <https://www.rfc-editor.org/info/rfc7011>.

   [RFC7149]  Boucadair, M. and C. Jacquenet, "Software-Defined
              Networking: A Perspective from within a Service Provider
              Environment", RFC 7149, DOI 10.17487/RFC7149, March 2014,
              <https://www.rfc-editor.org/info/rfc7149>.

   [RFC7950]  Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
              RFC 7950, DOI 10.17487/RFC7950, August 2016,
              <https://www.rfc-editor.org/info/rfc7950>.

   [RFC8612]  Mortensen, A., Reddy, T., and R. Moskowitz, "DDoS Open
              Threat Signaling (DOTS) Requirements", RFC 8612,
              DOI 10.17487/RFC8612, May 2019,
              <https://www.rfc-editor.org/info/rfc8612>.

   [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>.






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   [RFC8792]  Watsen, K., Auerswald, E., Farrel, A., and Q. Wu,
              "Handling Long Lines in Content of Internet-Drafts and
              RFCs", RFC 8792, DOI 10.17487/RFC8792, June 2020,
              <https://www.rfc-editor.org/info/rfc8792>.

   [RFC8903]  Dobbins, R., Migault, D., Moskowitz, R., Teague, N., Xia,
              L., and K. Nishizuka, "Use Cases for DDoS Open Threat
              Signaling", RFC 8903, DOI 10.17487/RFC8903, May 2021,
              <https://www.rfc-editor.org/info/rfc8903>.

   [RFC8955]  Loibl, C., Hares, S., Raszuk, R., McPherson, D., and M.
              Bacher, "Dissemination of Flow Specification Rules",
              RFC 8955, DOI 10.17487/RFC8955, December 2020,
              <https://www.rfc-editor.org/info/rfc8955>.

   [RFC9132]  Boucadair, M., Ed., Shallow, J., and T. Reddy.K,
              "Distributed Denial-of-Service Open Threat Signaling
              (DOTS) Signal Channel Specification", RFC 9132,
              DOI 10.17487/RFC9132, September 2021,
              <https://www.rfc-editor.org/info/rfc9132>.

Authors' Addresses

   Yuhei Hayashi
   NTT
   3-9-11, Midori-cho, Tokyo
   180-8585
   Japan
   Email: yuuhei.hayashi@gmail.com


   Meiling Chen
   CMCC
   32, Xuanwumen West
   BeiJing
   BeiJing, 100053
   China
   Email: chenmeiling@chinamobile.com


   Li Su
   CMCC
   32, Xuanwumen West
   BeiJing, BeiJing
   100053
   China
   Email: suli@chinamobile.com




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