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DOTS WG                                                  R. Dobbins, Ed.
Internet-Draft                                            Arbor Networks
Intended status: Informational                                 S. Fouant
Expires: May 21, 2017                            Corero Network Security
                                                              D. Migault
                                                                Ericsson
                                                            R. Moskowitz
                                                                  Huawei
                                                               N. Teague
                                                            Verisign Inc
                                                                  L. Xia
                                                                  Huawei
                                                            K. Nishizuka
                                                      NTT Communications
                                                       November 17, 2016


                Use cases for DDoS Open Threat Signaling
                    draft-ietf-dots-use-cases-03.txt

Abstract

   The DDoS Open Threat Signaling (DOTS) effort is intended to provide a
   protocol that facilitates interoperability between multivendor
   solutions/services.  This document presents use cases to evaluate the
   interactions expected between the DOTS components as well as the DOTS
   exchanges.  The purpose of the use cases is to identify the
   interacting DOTS component, how they collaborate and what are the
   types of information to be exchanged.

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 http://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 May 21, 2017.





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Copyright Notice

   Copyright (c) 2016 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
   Provisions Relating to IETF Documents
   (http://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 Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Terminology and Acronyms  . . . . . . . . . . . . . . . . . .   3
     2.1.  Requirements Terminology  . . . . . . . . . . . . . . . .   3
     2.2.  Acronyms  . . . . . . . . . . . . . . . . . . . . . . . .   4
     2.3.  Terms . . . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  Use Cases Scenarios . . . . . . . . . . . . . . . . . . . . .   4
     3.1.  Elementary Intra-organizational DDoS Mitigation . . . . .   5
     3.2.  Advanced/Extended Intra-Organizational DDoS Mitigation  .   6
     3.3.  Orchestrated Intra-Organizational DDoS Mitigation . . . .   6
     3.4.  Inter-Organizational DDoS Mitigation  . . . . . . . . . .   7
   4.  Use Cases Taxonomy  . . . . . . . . . . . . . . . . . . . . .   7
     4.1.  DOTS Client Taxonomy  . . . . . . . . . . . . . . . . . .   8
     4.2.  DOTS Server Taxonomy  . . . . . . . . . . . . . . . . . .  10
     4.3.  DOTS Message Taxonomy . . . . . . . . . . . . . . . . . .  10
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .  11
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  11
   7.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  11
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  12
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .  12
     8.2.  Informative References  . . . . . . . . . . . . . . . . .  12
   Appendix A.  Use Cases  . . . . . . . . . . . . . . . . . . . . .  12
     A.1.  Primary Use Cases . . . . . . . . . . . . . . . . . . . .  15
       A.1.1.  Automatic or Operator-Assisted DOTS Clients Request
               Upstream DDoS Mitigation Services . . . . . . . . . .  15
       A.1.2.  Manual Request to Upstream Mitigator  . . . . . . . .  17
       A.1.3.  Unsuccessful Automatic or Operator-Assisted DOTS
               Clients         Request Upstream DDoS Mitigation
               Services  . . . . . . . . . . . . . . . . . . . . . .  19
     A.2.  Ancillary Use Cases . . . . . . . . . . . . . . . . . . .  20
       A.2.1.  Auto-registration of DOTS clients with DOTS   servers  20
       A.2.2.  Auto-provisioning of DDoS countermeasures . . . . . .  21



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       A.2.3.  Informational DDoS attack notification to
               interested and authorized third parties . . . . . . .  21
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  21

1.  Introduction

   Currently, distributed denial-of-service (DDoS) attack mitigation
   solutions/services are largely based upon siloed, proprietary
   communications paradigms which result in vendor/service lock-in.  As
   a side-effect, this makes the configuration, provisioning, operation,
   and activation of these solutions a highly manual and often time-
   consuming process.  Additionally, coordination of multiple DDoS
   mitigation solutions/services simultaneously engaged in defending the
   same organization against DDoS attacks is fraught with both technical
   and process-related hurdles.  This greatly increase operational
   complexity and often results in suboptimal DDoS attack mitigation
   efficacy.

   The DDoS Open Threat Signaling (DOTS) effort is intended to provide a
   protocol that facilitates interoperability between multivendor DDoS
   mitigation solutions/services.  As DDoS solutions/services are
   broadly heterogeneous among different vendors, the primary goal for
   DOTS is to provide a high level interaction with these DDoS
   solutions/services such as initiating or terminating DDoS mitigation
   assistance.

   It should be noted that DOTS is not in and of itself intended to
   perform orchestration functions duplicative of the functionality
   being developed by the [I2NSF] WG; rather, DOTS is intended to allow
   devices, services, and applications to request DDoS attack mitigation
   assistance and receive mitigation status updates from systems of this
   nature.

   The use cases presented in the document are intended to provide
   examples of communications interactions DOTS-enabled nodes in both
   inter- and intra-organizational DDoS mitigation scenarios.  These use
   cases are expected to provide inputs for the design of the DOTS
   protocol(s).

2.  Terminology and Acronyms

2.1.  Requirements Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119].





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2.2.  Acronyms

   This document makes use of the same terminology and definitions as
   [I-D.ietf-dots-requirements], except where noted.

2.3.  Terms

   Inter-organizational: a DOTS communications relationship between
   distinct organizations with separate spans of administrative control.
   Typical inter-organizational DOTS communication relationships would
   be between a DDoS mitigation service provider and an end-customer
   organizational which requires DDoS mitigation assistance; between
   multiple DDoS mitigation service providers coordinating mutual
   defense of a mutual end-customer; or between DDoS mitigation service
   providers which are requesting additional DDoS mitigation assistance
   in for attacks which exceed their inherent DDoS mitigation capacities
   and/or capabilities.

   Intra-organizational: a DOTS communications relationship between
   various elements within a single span of administrative control.  A
   typical intra-organizational DOTS communications relationship would
   be between DOTS clients, DOTS gateways, and DOTS servers within the
   same organization.

3.  Use Cases Scenarios

   This section provides a high-level description of scenarios addressed
   by DOTS.  These scenarios are described in more detail in Appendix A.
   In both sections, the scenarios are provided in order to illustrate
   the use of DOTS in typical DDoS attack scenarios.  They are not
   definitive, and other use cases are expected to emerge with
   widespread DOTS deployment.

   All scenarios present a coordination between the targeted
   organization, the DDoS attack telemetry and the mitigator.  The
   coordination and communication between these entity depends, for
   example on the characteristic or functionality of the equipment, the
   reliability of the information provided by DDoS attack telemetry, and
   the business relationship between the DDoS target domain and the
   mitigator.

   More explicitly, in some cases, the DDoS telemetry attack may simply
   activate a DDoS mitigation, whereas in other cases, it may
   collaborate by providing some information about an attack.  In some
   cases, the DDoS mitigation may be orchestrated, which includes
   selecting a specific appliance as well as starting/ending a
   mitigation.




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3.1.  Elementary Intra-organizational DDoS Mitigation

   The most elementary scenario considers equipment such as a CPE that
   when overloaded sends an alert to specific equipment located
   upstream.  In many cases, these very basic devices are unlikely to
   diagnose whether an DDoS attack is ongoing or not and detection as
   well as potential mitigation is left to the upstream equipment.

   In many deployments, the upstream equipment belongs to the same
   organization as the CPE.  In such cases, it is not expected that a
   specific commercial contract is established between the CPE and the
   DDoS mitigation service.  The CPE and concerned traffic is likely to
   be identified by the source of the alert, which also imply the
   mitigator is aware of the nature of the equipment as well as the
   architecture of the organization.

   For example, the DDoS mitigation service may be equipment that is
   located on path or a controller that will configure the network to
   the traffic to be analyzed and mitigated is redirected to a dedicated
   vendor specific equipment or solution.  The DDoS mitigation service
   may be activated only for the traffic associated to the CPE sending
   the alert or instead to the traffic associated to all CPE.  Such
   decisions are not part of DOTS, but instead depend on the policies of
   the network administrator.

   The DDoS mitigation service is expected to acknowledge the reception
   of the alert in order to avoid retransmission.  This may become an
   issue if an ISP receives alerts from all CPEs multiple times.
   However, it is unlikely that in such cases the CPE will follow the
   status of the mitigation.  Instead, as the DDoS mitigation service
   and the CPE belongs to the same administrative domain, it is expected
   that the decision of mitigating or not, as well as the decision to
   end an ongoing mitigation will be left to DDoS mitigation service
   without notice to the CPEs.

   There are several merits of using DOTS signaling in an intra-
   organizational manner:

   1.  It will facilitate interoperability between DDoS solutions/
   services by providing a standards-based, programmatic communications
   mechanism

   2.  It will reduce time to initiate DDoS mitigation services

   The required data exchange between DOTS client and DOTS server may be
   equivalent to or a subset of information set of inter-organizational
   use cases.




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3.2.  Advanced/Extended Intra-Organizational DDoS Mitigation

   This section considers that more specialized equipment is generating
   DDoS alerts.  These devices are likely to provide reliable
   information about the ongoing attack.

   Such equipment could typically be a telemetry system, or a specific
   targeted service such as a web server, or another type application
   detecting application-specific attacks.

   Typically, a telemetry system may indicate classifiers of DDoS attack
   traffic as well indicators or qualification of the detected attack.

   As the telemetry system is expected to monitor multiple aspects of
   the traffic, similarly when an attack is detected by the target
   service.

   The destination of the alert is likely to receive alerts from
   multiple different services (DNS, HTTP, TCP, UDP, application layer
   specific...).  Such information is likely to be trusted and
   considered by the mitigator to apply to the appropriated security
   appliance.

   Note that within a single domain it is likely that the service or the
   telemetry system is the most accurate equipment to qualify the
   attack.

   As a result, not providing the information is likely to re-do the
   analysis phase.  Providing the information while sending the alert
   avoid re-processing the analysis.  Instead the mitigator directly
   uses the information to redirect the traffic to the appropriated
   specialized appliance.

   For the same reasons as the CPE, as mitigation of the DDoS Service is
   performed in a single administrative domain, the source of the alert
   may not manage the end of the mitigation service and leave such
   decision to the administrator of domain or the DDoS mitigation
   service.

3.3.  Orchestrated Intra-Organizational DDoS Mitigation

   This section presents a generalization of the Service/System intra-
   organizational scenario.  Orchestration goes one step further and
   considers that the information carried by the alert could have some
   management purpose.  This includes explicitly starting/ending
   mitigation as well as selecting a specific DDoS mitigation service.
   This differs from the previous case in that the source of the alert




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   does not leave the decision on how to mitigate the attack by the
   mitigator.  Instead the mitigator is orchestrated.

   Typical example of orchestrators could be a network administrator
   that monitors the traffic and manually initiates a DDoS mitigation
   from its web portal.  Orchestration may also applied automatically by
   an orchestrator.

3.4.  Inter-Organizational DDoS Mitigation

   In the case of inter-organizational mitigation, it is expected that a
   DDoS mitigation service provider can provide DDoS mitigation service
   to the targeted organization.  The relationship between the two
   organizations is generally expected to be described into a pre-agreed
   contract, although ad-hoc mitigation scenarios without a pre-existing
   business relationship are also quite common, and DOTS is intended to
   work in either scenario, once the appropriate DOTS communications
   relationships are configured by the involved parties.

   Mutual authentication between all elements in the DOTS communications
   chain is required in both intra- and inter-organizational scenarios.

   DDoS attacks are often sourced from multiple independent networks on
   the Internet.  The targeted organization may request DDoS mitigation
   services from multiple peered DOTS organizations with cooperation
   contract in order to mitigate a given attack.

   The coordination relationship among the DOTS organizations will often
   be bilateral, which represents a direct peer to peer communication
   between each DOTS organization without the existence of a broker or
   orchestrator.  The other case is a broker or orchestrator
   facilitating DDOS mitigation coordination among multiple DOTS-enabled
   organizations.

4.  Use Cases Taxonomy

   DOTS communication is a communication between a DOTS Client and a
   DOTS Server.  A DOTS Client or DOTS Server can be hosted on different
   nodes which are associated to different functionalities, and thus
   leading to different expectations from DOTS.  This section provides a
   classification of the DOTS Client, DOTS Servers as well as the
   different examples of DOTS message exchanges.

   Appendix A provides more details of anticipated DOTS communications
   relationships, message flow, and message type examples.






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4.1.  DOTS Client Taxonomy

   DOTS clients initiate DOTS communications in order to request DDoS
   mitigation assistance.  This includes initiation/termination ofDDoS
   mitigation service as well as requesting and reporting the status and
   efficacy of an ongoing DDoS mitigation.

   Note that this section only considers DOTS Client that are actually
   initiating an exchange with a DOTS Server, and nodes that simply
   relay DOTS messages are not considered here.

   Here are the categories of DOTS Client envisioned in this document:

   (a)  DOTS Client alerting a DDoS attack is ongoing

        i)     hosted on the target attack

        ii)    hosted on a monitoring service/system

   (b)  DOTS Client coordinating an DDoS attack mitigation

        i)     hosted on an orchestrator

        ii)    hosted on administrative GUI

   When an alert is raised by the node under attack, very little
   information is expected to be provided by DOTS Client to the DDoS
   mitigation service/system.  More particularly telemetric information
   or characteristics of the attack are likely to be unreliable as the
   host is already overloaded, and may not have sophisticated DDoS
   detection/classification capabilities.

   When the DOTS Client is hosted on a more sophisticated attack
   monitoring system, the monitoring system may raise an alert an attack
   is ongoing.  Unlike the host under attack, the monitoring system is
   expected to have sufficient resource so it is not itself overload and
   impacted by the ongoing attack.  As a result, the DOTS Client is more
   likely to provide additional information associated to the alert, as
   this information is expected to be reliable.  The type of information
   associated may be associated to the asset to protect and eventually
   some information qualifying the attack.  The information associated
   also depends on what has been agreed with DDoS mitigation service/
   system.  In most cases, when a DDoS attack is detected all the
   traffic is redirected to the DDoS mitigation procedure that has been
   agreed between the DDoS mitigation service/system and the entity
   hosting the monitoring service.  In such cases, very little
   information is needed.




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   When the DOTS Client is hosted on an orchestrator, the DOTS Client
   contacts the DDoS mitigation service/system to initiates a DDoS
   mitigation.  The orchestrator is responsible for setting the network
   to redirect the traffic to the DDoS mitigation service/system.  If
   the DDoS mitigation service/system is not available, the orchestrator
   is responsible for finding an alternative.  Again the orchestrator is
   likely to provide additional information to the DDoS mitigation
   service/system.  For example, typical information may be the asset to
   protect, as well as the specific mitigation function requested.

   The service is usually expected to be associated with the mitigation
   service, and so may not be explicitly specified.  In addition, the
   DOTS Client is also expected to control how the DDoS mitigation is
   performed.  More specifically, it is expected that the DOTS Client
   can terminate the DDoS mitigation.  The DOTS Client should have
   sufficient information to decide how to operate next.  For example,
   it should be able to check if the mitigation is ongoing as well as
   the efficiency of the mitigation.

   When the DOTS client is hosted on an administrative system, the DOTS
   Client may be triggered by the network administrator to initiate a
   DDoS mitigation.  In this case, the DOTS Server is likely to be an
   orchestrator, and all necessary information may be provided so the
   DDoS mitigation can be initiated.  This includes, the asset to be
   protected, the action expected to be performed by the orchestrator,
   the DDoS mitigation service/system to contact...

   Note that information included by DOTS Client in a request for
   mitigation is not limited to simple mitigation assistance requests;
   it can be more detailed.  However, as DDoS mitigation systems are
   highly heterogeneous, if there is a need to provide interoperability
   between the vendors and DDoS mitigation services/systems, the actions
   provided by a DOTS Clients remains small and accepted by all
   services/systems.  As a result here are the envisioned optional
   information provided by the DOTS Client.

   (a)  recommended asset to protect (e.g.  IP, port number, DNS record,
        URI, et. all.).  This information specifies the expected action
        from the DDoS mitigation service/system.

   (b)  optional DDoS Mitigation Contract ID: which references the
        contract agreed out-of-band.  This information specifies the
        expected action from the DDoS mitigation service/system.

   (c)  optional Requested Service: which designates the function or
        service associated to the DDoS mitigation service/system.  This
        information specifies the expected action from the DDoS
        mitigation service/system.



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   (d)  optional DDoS attack information (e.g. suspected attack,
        telemetry): This information is expected to help the mitigation
        service/system to diagnose the ongoing attack.

   In both cases, the DOTS Client sends a request for DDoS mitigation to
   the DOTS Server, and expects the DDoS mitigation service/system to
   mitigate the DDoS attack.  The difference between sending a request
   for DDoS mitigation as an alert or for coordinating an DDoS
   mitigation is that an alert is a request to completely outsource the
   mitigation, whereas the coordination requires additional control over
   the DDoS mitigation.  An alert may be acknowledged by the DOTS Server
   to acknowledge the reception whereas during the coordination, the
   DOTS server may acknowledge the initiation of the DDoS mitigation.

4.2.  DOTS Server Taxonomy

   DOTS Servers terminate DOTS communications.  The DOTS Server is
   typically hosted on a DDoS mitigation service/system or an
   intermediary node such as an orchestrator.

   The DOTS Server is expected to be the entry point of a DDoS
   mitigation service/system.  Some DOTS Clients do not expect any
   further interaction from the DOTS Server, once a DDoS mitigation has
   been requested.  This is especially true for DOTS Clients hosted on
   the attack target.  Other DOTS Clients hosted on orchestrators or
   DDoS mitigation service/systems are likely to expect from the DOTS
   Server a confirmation the system accepts the DDoS mitigation task.

   These DOTS Client are also likely to expect a confirmation when DDoS
   mitigation service termination has been requested.

   In addition, DOTS Servers are also expected to provide information
   related to the mitigation status when requested by the DOTS Client.

   It is also expected that the DOTS Server could provide some status
   report of the DDoS mitigation on a push basis.

4.3.  DOTS Message Taxonomy

   The core essential messages to coordination a heterogeneous set of
   DDoS mitigation services/system needs to be small and enable future
   options.  Here are the different exchanges envisioned in this
   document between a DOTS Client and a DOTS Server.

   (a)  DOTS MITIGATION CONTROL messages are used by the DOTS Client to
        initiate or terminate a DDoS mitigation.  The initiator the
        termination can be specified by the action type START or STOP.
        These messages can carry some additional options that specify



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        information such as the asset under attack.  These DOTS
        MITIGATION CONTROL messages are expected to be ACKed by the DOTS
        Server, in order to indicate the DOTS Server will perform the
        requested action.  In any other case an error is expected to be
        returned.  In the case of a DOTS Client sends an alert, ACK is
        recommended so the DOTS Client stop sending the alert.

   (b)  DOTS MITIGATION INFORMATIONAL message are left for any
        additional interaction between a DOTS Client and DOTS Server
        regarding an ongoing request.  An INFORMATIONAL message can be
        ignored by the receiver if it does not understand the requested
        information or options.  In the current document an
        informational message can be the status of the ongoing
        mitigation.

   (c)  DOTS ERROR contains the errors associated to a request.

   (d)  DOTS OPTIONS: options can be used to indicate some optional
        information.  The option is expected to specify whether the DOTS
        Server can ignore it or must return an error if it is not
        understood.  Options are not messages, but part of the message.

5.  Security Considerations

   DOTS is at risk from three primary attacks: DOTS agent impersonation,
   traffic injection, and signaling blocking.  The DOTS protocol MUST be
   designed for minimal data transfer to address the blocking risk.

   Impersonation and traffic injection mitigation can be managed through
   current secure communications best practices.  DOTS is not subject to
   anything new in this area.  One consideration could be to minimize
   the security technologies in use at any one time.  The more needed,
   the greater the risk of failures coming from assumptions on one
   technology providing protection that it does not in the presence of
   another technology.

   Additional details of DOTS security requirements may be found in
   [I-D.ietf-dots-requirements].

6.  IANA Considerations

   No IANA considerations exist for this document at this time.

7.  Acknowledgments

   TBD





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8.  References

8.1.  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,
              <http://www.rfc-editor.org/info/rfc2119>.

8.2.  Informative References

   [APACHE]   "Apache mod_security", <https://www.modsecurity.org>.

   [I-D.ietf-dots-requirements]
              Mortensen, A., Moskowitz, R., and T. Reddy, "Distributed
              Denial of Service (DDoS) Open Threat Signaling
              Requirements", draft-ietf-dots-requirements-03 (work in
              progress), October 2016.

   [RFC6335]  Cotton, M., Eggert, L., Touch, J., Westerlund, M., and S.
              Cheshire, "Internet Assigned Numbers Authority (IANA)
              Procedures for the Management of the Service Name and
              Transport Protocol Port Number Registry", BCP 165,
              RFC 6335, DOI 10.17487/RFC6335, August 2011,
              <http://www.rfc-editor.org/info/rfc6335>.

   [RRL]      "BIND RRL", <https://deepthought.isc.org/article/AA-
              00994/0/Using-the-Response-Rate-Limiting-Feature-in-BIND-
              9.10.html>.

Appendix A.  Use Cases

   This section provides a high-level overview of likely use cases and
   deployment scenarios for DOTS-enabled DDoS mitigation services.  It
   should be noted that DOTS servers may be standalone entities which,
   upon receiving a DOTS mitigation service request from a DOTS client,
   proceed to initiate DDoS mitigation service by communicating directly
   or indirectly with DDoS mitigators, and likewise terminate the
   service upon receipt of a DOTS service termination request;
   conversely, the DDoS mitigators themselves may incorporate DOTS
   servers and/or DOTS clients.  The mechanisms by which DOTS servers
   initiate and terminate DDoS mitigation service with DDoS mitigators
   is beyond the scope of this document.

   All of the primary use cases described in this section are derived
   from current, real-world DDoS mitigation functionality, capabilities,
   and operational models.




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   The posited ancillary use cases described in this section are
   reasonable and highly desirable extrapolations of the functionality
   of baseline DOTS capabilities, and are readily attainable in the near
   term.

   Each of the primary and ancillary use cases described in this section
   may be read as involving one or more DDoS mitigation service
   providers; DOTS makes multi-provider coordinated DDoS defenses much
   more effective and practical due to abstraction of the particulars of
   a given DDoS mitigation service/solution set.

   Both the primary and ancillary use cases may be facilitated by direct
   DOTS client - DOTS server communications or via DOTS relays deployed
   in order to aggregate DOTS mitigation service requests/responses, to
   mediate between stateless and stateful underlying transport
   protocols, to aggregate multiple DOTS requests and/or responses, to
   filter DOTS requests and/or responses via configured policy
   mechanisms, or some combination of these functions.

   All DOTS messages exchanged between the DOTS clients and DOTS servers
   in these use cases may be communicated directly between DOTS clients
   and servers, or mediated by one or more DOTS relays residing on the
   network of the originating network, the network where upstream DDoS
   mitigation service takes place, an intervening network or networks,
   or some combination of the above.

   DOTS is intended to apply to both inter- and Intra-organizational
   DDoS attack mitigation scenarios.  The technical and operational
   requirements for inter- and Intra-organizational DOTS communications
   are identical.  The main difference is administrative in nature;
   although it should be noted that provisioning challenges which are
   typically associated with inter-organizational DOTS communications
   relationships may also apply in intra-organizational deployment
   scenarios, based upon organizational factors.  All of the same
   complexities surrounding authentication and authorization can apply
   in both contexts, including considerations such as network access
   policies to allow DOTS communications; DOTS transport selection
   (including considerations of the implications of link congestion if a
   stateful DOTS transport option is selected), etc.  Registration of
   well-known ports for DOTS transports per [RFC6335] should be
   considered in light of these challenges.

   It should also be noted that DOTS does not directly ameliorate the
   various administrative challenges required for successful DDoS attack
   mitigation.  Letters of authorization, RADB updates, DNS zone
   delegations, alteration of network access policies, technical
   configurations required to facilitate network traffic diversion and
   re-injection, etc., are all outside the scope of DOTS.  DOTS may,



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   however, prove useful in automating the registration of DOTS clients
   with DOTS servers, as well as in the automatic provisioning of
   situationally-appropriate DDoS defenses and countermeasures.  This
   ancillary DOTS functionality is described in Appendix A.2.

   Many of the 'external' administrative challenges associated with
   establishing workable DDoS attack mitigation service may be addressed
   by work currently in progress in the I2RS and I2NSF WGs.  Interested
   parties may wish to consider tracking those efforts, and coordination
   with both I2RS and I2NSF is highly desirable.

   Note that all the use-cases in this document are universal in nature.
   They apply equally to endpoint networks, transit backbone providers,
   cloud providers, broadband access providers, ASPs, CDNs, etc.  They
   are not specific to particular business models, topological models,
   or application types, and are deliberately generalizable.  Both
   networks targeted for attack as well as any adjacent or topologically
   distant networks involved in a given scenario may be either single-
   or multi-homed.  In the accompanying vector illustrations
   incorporated into draft-ietf-dots-use-cases-01.pdf, specific business
   and topological models are described in order to provide context.

   Likewise, both DOTS itself and the use cases described in this
   document are completely independent of technologies utilized for the
   detection, classification, traceback, and mitigation of DDoS attacks.

   Flow telemetry such as NetFlow and IPFIX, direct full-packet
   analysis, log-file analysis, indirection manual observation, etc. can
   and will be enablers for detection, classification and traceback.

   Intelligent DDoS mitigation systems (IDMSes), flowspec, S/RTBH, ACLs,
   and other network traffic manipulation tools and techniques may be
   used for DDoS attack mitigation.  BGP, flowspec, DNS, inline
   deployment, and various 'NFV' technologies may be used for network
   traffic diversion into mitigation centers or devices in applicable
   scenarios; GRE, MPLS, 'NFV', inline deployment and other techniques
   may be utilized for 'cleaned' traffic re-injection to its intended
   destination.

   The scope, format, and content of all DOTS message types cited in
   this document must be codified by the DOTS WG.

   The following use cases are intended to inform the DOTS requirements
   described in [I-D.ietf-dots-requirements].







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A.1.  Primary Use Cases

A.1.1.  Automatic or Operator-Assisted DOTS Clients Request Upstream
        DDoS Mitigation Services

   DOTS client can be supported on different devices or systems, like:

   - CPE or PE mitigators: CPE or PE mitigators can mitigate the DDoS
   attack by itself, but also with DOTS client capabilities may be
   configured to signal to one or more DOTS servers in order to request
   upstream DDoS mitigation service initiation during an attack when
   DDoS attack volumes and/or attack characteristics exceed the
   capabilities of such CPE mitigators;

   - CPE or PE network infrastructure elements: Refer to the network
   elements like routers, switches, load-balancers, firewalls, 'IPSes',
   etc, which have the capability to detect and classify DDoS attacks.
   These network elements involved are not engaged in mitigating DDoS
   attack traffic, instead have DOTS client capabilities to be
   configured to signal to one or more DOTS servers in order to request
   upstream DDoS mitigation service initiation during an attack;

   - CPE or PE Attack Telemetry Detection/Classification Systems: These
   systems having DOTS client capabilities may be configured so that
   upon detecting and classifying a DDoS attack, they signal one or more
   DOTS servers in order to request upstream DDoS mitigation service
   initiation.  These systems do not possess any inherent capability to
   mitigate DDoS attack traffic, and is signaling for upstream
   mitigation assistance;

   - The DDoS targeted service/applications: A service or application
   which is the target of a DDoS attack and which has the capability to
   detect and classify DDoS attacks (i.e, Apache mod_security [APACHE],
   BIND RRL [RRL], etc.) as well as DOTS client functionality may be
   configured so that upon detecting and classifying a DDoS attack, it
   signals one or more DOTS servers in order to request upstream DDoS
   mitigation service initiation.  They do not possess any inherent
   capability to mitigate DDoS attack traffic, and is signaling for
   upstream mitigation assistance.

   Despite the different implementations of DOTS client, the DOTS
   signaling process of them are very similar.  For simplicity, the
   abstract term 'DOTS client' is used here as a general representation
   for all kinds of implementation.

   One or more DOTS clients may be configured to signal to one or more
   DOTS servers in order to request upstream DDoS mitigation service
   initiation during an attack.  DDoS mitigation service may be



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   terminated either automatically or manually via a DOTS mitigation
   service termination request initiated by the DOTS client when it has
   been determined that the DDoS attack has ended.  The DOTS signaling
   process listed below applies to both intra- and inter-organizational
   scenarios:

   (a)  A DDoS attack is initiated against online properties of an
        organization with DOTS clients deployed.

   (b)  DOTS client detects, classifies, and maybe begin mitigating the
        DDoS attack (if it's implemented as the DDoS mitigator).

   (c)  DOTS client determine to send a DOTS mitigation service
        initiation request (for DDoS mitigator, if their capability to
        mitigate the DDoS attack is insufficient) to one or more DOTS
        servers residing on one or more upstream transit networks, peer
        networks, or overlay MSSP networks, either directly or via
        intermediate DOTS relays residing upon the requesting
        organization's network, the upstream mitigation provider's
        network, or both.  This DOTS mitigation service initiation
        request may be automatically initiated by the DOTS clients, or
        may be manually triggered by personnel of the requesting
        organization in response to an alert from the DOTS clients (the
        mechanism by which this process takes place is beyond the scope
        of this document).

   (d)  The DOTS servers which receive the DOTS mitigation service
        initiation requests determine that they have been configured to
        honor requests from the requesting DOTS clients, and initiate
        situationally-appropriate DDoS mitigation service on their
        respective networks (the mechanism by which this process takes
        place is beyond the scope of this document).

   (e)  The DOTS servers transmit a DOTS service status message to the
        requesting DOTS clients indicating that upstream DDoS mitigation
        service has been initiated.

   (f)  While DDoS mitigation services are active, the DOTS servers
        regularly transmit DOTS mitigation status updates to the
        requesting DOTS clients.

   (g)  While DDoS mitigation services are active, the DOTS clients may
        optionally regularly transmit DOTS mitigation efficacy updates
        to the relevant DOTS servers.

   (h)  When the upstream DDoS mitigators determine that the DDoS attack
        has ceased, they indicate this change in status to their




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        respective DOTS servers (the mechanism by which this process
        takes place is beyond the scope of this document).

   (i)  The DOTS servers transmit a DOTS mitigation status update to the
        DOTS clients indicating that the DDoS attack has ceased.

   (j)  The DOTS clients transmit a DOTS mitigation service termination
        request to the DOTS servers.  This DOTS mitigation service
        termination request may be automatically initiated by the DOTS
        clients, or may be manually triggered by personnel of the
        requesting organization in response to an alert from the DOTS
        clients or a management system which monitors them (the
        mechanism by which this process takes place is beyond the scope
        of this document).

   (k)  The DOTS servers terminate DDoS mitigation service on their
        respective networks (the mechanism by which this process takes
        place is beyond the scope of this document).

   (l)  The DOTS servers transmit a DOTS mitigation status update to the
        DOTS clients indicating that DDoS mitigation services have been
        terminated.

   (m)  The DOTS clients transmit a DOTS mitigation termination status
        acknowledgement to the DOTS servers.

A.1.2.  Manual Request to Upstream Mitigator

   A Web portal, or application for mobile devices such as smartphones
   and tablets, which has DOTS client capabilities has been configured
   in order to allow authorized personnel of organizations which are
   targeted by DDoS attacks to manually request upstream DDoS mitigation
   service initiation from a DOTS server.  When an organization has
   reason to believe that it is under active attack, authorized
   personnel may utilize the Web portal or mobile device application to
   manually initiate a DOTS client mitigation request to one or more
   DOTS servers in order to initiate upstream DDoS mitigation services.
   DDoS mitigation service may be terminated manually via a DOTS
   mitigation service termination request through the Web portal or
   mobile device application when it has been determined that the DDoS
   attack has ended.

   In this use-case, the organization targeted for attack does not
   possess any automated or operator-assisted mechanisms for DDoS attack
   detection, classification, traceback, or mitigation; the existence of
   an attack has been inferred manually, and the organization is
   requesting upstream mitigation assistance.  This can theoretically be




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   an inter- or Intra-organizational use-case, but is more typically an
   inter-organizational scenario.

   (a)  A DDoS attack is initiated against online properties of an
        organization have access to a Web portal or mobile device
        application which incorporates DOTS client functionality and can
        generate DOTS mitigation service requests upon demand.

   (b)  Authorized personnel utilize the Web portal or mobile device
        application to send a DOTS mitigation service initiation request
        to one or more upstream transit networks, peer networks, or
        overlay MSSP networks, either directly or via intermediate DOTS
        relays residing upon the requesting organization's network, the
        upstream mitigation provider's network, or both.  This DOTS
        mitigation service initiation request is manually triggered by
        personnel of the requesting organization when it is judged that
        the organization is under DDoS attack (the mechanism by which
        this process takes place is beyond the scope of this document).

   (c)  The DOTS servers which receive the DOTS mitigation service
        initiation requests determine that they have been provisioned to
        honor requests from the Web portal or mobile device application,
        and initiate situationally-appropriate DDoS mitigation service
        on their respective networks (the mechanism by which this
        process takes place is beyond the scope of this document).

   (d)  The DOTS servers transmit a DOTS service status message to the
        Web portal or mobile device application indicating that upstream
        DDoS mitigation service has been initiated.

   (e)  While DDoS mitigation services are active, the DOTS servers
        regularly transmit DOTS mitigation status updates to the Web
        portal or mobile device application.

   (f)  While DDoS mitigation services are active, the Web portal or
        mobile device application may optionally regularly transmit
        manually-triggered DOTS mitigation efficacy updates to the
        relevant DOTS servers.

   (g)  When the upstream DDoS mitigators determine that the DDoS attack
        has ceased, they indicate this change in status to their
        respective DOTS servers (the mechanism by which this process
        takes place is beyond the scope of this document).

   (h)  The DOTS servers transmit a DOTS mitigation status update to the
        Web portal or mobile device application indicating that the DDoS
        attack has ceased.




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   (i)  The Web portal or mobile device application transmits a
        manually-triggered DOTS mitigation service termination request
        to the DOTS servers (the mechanism by which this process takes
        place is beyond the scope of this document).

   (j)  The DOTS servers terminate DDoS mitigation service on their
        respective networks (the mechanism by which this process takes
        place is beyond the scope of this document).

   (k)  The DOTS servers transmit a DOTS mitigation status update to the
        Web portal or mobile device application indicating that DDoS
        mitigation services have been terminated.

   (l)  The Web portal or mobile device application transmits a DOTS
        mitigation termination status acknowledgement to the DOTS
        servers.

A.1.3.  Unsuccessful Automatic or Operator-Assisted DOTS Clients Request
        Upstream DDoS Mitigation Services

   One or more DOTS clients may be configured to signal to one or more
   DOTS servers in order to request upstream DDoS mitigation service
   initiation during an attack (for DDoS mitigators, when DDoS attack
   volumes and/or attack characteristics exceed the capabilities of such
   mitigators).  DDoS mitigation service may be terminated either
   automatically or manually via a DOTS mitigation service termination
   request initiated by the DOTS client when it has been determined that
   the DDoS attack has ended.

   This can theoretically be an inter- or Intra-organizational use-case,
   but is more typically an inter-organizational scenario.

   (a)  A DDoS attack is initiated against online properties of an
        organization with DOTS clients deployed.

   (b)  DOTS client detects, classifies, and begins mitigating the DDoS
        attack (if it's implemented as the DDoS mitigator).

   (c)  DOTS clients determine to send a DOTS mitigation service
        initiation request (for DDoS mitigator, if their capability to
        mitigate the DDoS attack is insufficient) to one or more DOTS
        servers residing on one or more upstream transit networks, peer
        networks, or overlay MSSP networks, either directly or via
        intermediate DOTS relays residing upon the requesting
        organization's network, the upstream mitigation provider's
        network, or both.  This DOTS mitigation service initiation
        request may be automatically initiated by the DOTS clients, or
        may be manually triggered by personnel of the requesting



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        organization in response to an alert from the DOTS clients (the
        mechanism by which this process takes place is beyond the scope
        of this document).

   (d)  The DOTS servers which receive the DOTS mitigation service
        initiation requests determine that they have been configured to
        honor requests from the requesting DOTS clients, and attempt to
        initiate situationally-appropriate DDoS mitigation service on
        their respective networks (the mechanism by which this process
        takes place is beyond the scope of this document).

   (e)  The DDoS mitigators on the upstream network report back to the
        DOTS servers that they are unable to initiate DDoS mitigation
        service for the requesting organization due to mitigation
        capacity constraints, bandwidth constraints, functionality
        constraints, hardware casualties, or other impediments (the
        mechanism by which this process takes place is beyond the scope
        of this document).

   (f)  The DOTS servers transmit a DOTS service status message to the
        requesting DOTS clients indicating that upstream DDoS mitigation
        service cannot be initiated as requested.

   (g)  The DOTS clients may optionally regularly re-transmit DOTS
        mitigation status request messages to the relevant DOTS servers
        until acknowledgement that mitigation services have been
        initiated.

   (h)  The DOTS clients may optionally transmit a DOTS mitigation
        service initiation request to DOTS servers associated with a
        configured fallback upstream DDoS mitigation service.  Multiple
        fallback DDoS mitigation services may optionally be configured.

   (i)  The process describe above cyclically continues until the DDoS
        mitigation service request is fulfilled; the DOTS clients
        determine that the DDoS attack volume has decreased to a level
        and/or complexity which they themselves can successfully
        mitigate; the DDoS attack has ceased; or manual intervention by
        personnel of the requesting organization has taken place.

A.2.  Ancillary Use Cases

A.2.1.  Auto-registration of DOTS clients with DOTS servers

   An additional benefit of DOTS is that by utilizing agreed-upon
   authentication mechanisms, DOTS clients can automatically register
   for DDoS mitigation service with one or more upstream DOTS servers.




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   The details of such registration are beyond the scope of this
   document.

A.2.2.  Auto-provisioning of DDoS countermeasures

   The largely manual tasks associated with provisioning effective,
   situationally-appropriate DDoS countermeasures is a significant
   barrier to providing/obtaining DDoS mitigation services for both
   mitigation providers and mitigation recipients.  Due to the 'self-
   descriptive' nature of DOTS registration messages and mitigation
   requests, the implementation and deployment of DOTS has the potential
   to automate countermeasure selection and configuration for DDoS
   mitigators.  The details of such provisioning are beyond the scope of
   this document.

   This can theoretically be an inter- or Intra-organizational use-case,
   but is more typically an inter-organizational scenario.

A.2.3.  Informational DDoS attack notification to interested and
        authorized third parties

   In addition to its primary role of providing a standardized,
   programmatic approach to the automated and/or operator-assisted
   request of DDoS mitigation services and providing status updates of
   those mitigations to requesters, DOTS may be utilized to notify
   security researchers, law enforcement agencies, regulatory bodies,
   etc. of DDoS attacks against attack targets, assuming that
   organizations making use of DOTS choose to share such third-party
   notifications, in keeping with all applicable laws, regulations,
   privacy and confidentiality considerations, and contractual
   agreements between DOTS users and said third parties.

   This is an inter-organizational scenario.

Authors' Addresses

   Roland Dobbins (editor)
   Arbor Networks
   30 Raffles Place
   Level 17 Chevron House
   Singapore 048622
   Singapore

   Email: rdobbins@arbor.net







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   Stefan Fouant
   Corero Network Security

   Email: Stefan.Fouant@corero.com


   Daniel Migault
   Ericsson
   8400 boulevard Decarie
   Montreal, QC  H4P 2N2
   Canada

   Phone: +1 514-452-2160
   Email: daniel.migault@ericsson.com


   Robert Moskowitz
   Huawei
   Oak Park, MI  48237
   USA

   Email: rgm@labs.htt-consult.com


   Nik Teague
   Verisign Inc
   12061 Bluemont Way
   Reston, VA  20190
   USA

   Phone: +44 791 763 5384
   Email: nteague@verisign.com


   Liang Xia
   Huawei
   No. 101, Software Avenue, Yuhuatai District
   Nanjing
   China

   Email: Frank.xialiang@huawei.com










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   Kaname Nishizuka
   NTT Communications
   GranPark 16F
   3-4-1 Shibaura, Minato-ku, Tokyo
   108-8118,Japan

   Email: kaname@nttv6.jp












































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