[Dots] comments on the use case draft 09

Daniel Migault <daniel.migault@ericsson.com> Thu, 15 March 2018 14:46 UTC

From: Daniel Migault <daniel.migault@ericsson.com>
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Subject: [Dots] comments on the use case draft 09
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Hi all,

Please find my personal comments on the current draft. Co-authors have decided to bring their comments to the WG mailing list so the WG can be informed of the evolution of the draft. A version is expected to come very soon.

Feel free to comment!

Yours,

Daniel

looking at the different inter domain use cases, my feeling is that the most generic use case is the use case described in the current section 3.1.2.2. "MSSP as an end-customer requesting overflow DDoS mitigation assistance from other MSSPs". The use case "Upstream Transit Providers Offering DDoS Mitigation Services" seems to me related to the "Overlay MSSPs Offering DDoS Mitigation Services" with the addition that the ddos mitigation is bound to a specific link. This constraint, in case multiple links adds some managements between providers.

With that perspective, I would favor to start with the use case described in the current section 3.1.2.2. "MSSP as an end-customer requesting overflow DDoS mitigation assistance from other MSSPs" and then follow up with the "Upstream Transit Providers Offering DDoS Mitigation Services" as another use case. I would expect the "Overlay MSSPs Offering DDoS Mitigation Services" to have the complete description that is currently provided in section 3.1.1.1 while the "Upstream Transit Providers Offering DDoS Mitigation Services" only document the additional constraint of binding ddos mitigation to the upstream link, the motivation for adding this constraints as well as the additional management overhead associated to that constraint. I do not think that repeating the complete steps as currently described in 3.1.1.1. would be necessary since these would already be described before.

In my opinion, reducing the number of use cases would ease the reading of the document. These are the use cases I would consider, each being summed up into a single section/subsection.

* Use Case1 : "End-customer with an overlay DDoS mitigation managed security service provider (MSSP)" (current section 3.1.2.2)

* Use Case2: Upstream Transit Providers Offering DDoS Mitigation Services (current section 3.1.1.)

* Use Case 3: DDoS Orchestration (current section 3.2.3)

I read section 3.1.3 as specific implementations of Use Case 1-2-3, and As such I would split the information of section section 1-2-3 into the section related in each Use case.

I read section MSSP as an end-customer requesting overflow DDoS mitigation assistance from other MSSPs ( current section 3.1.2.2.) as redundant with 3.2.3. DDoS Orchestration, and so remove this subsection.

I read section 3.2.2. "Home Network DDoS Detection Collaboration for ISP network management" as very close to 3.1.1.1. End-customer with a single upstream transit provider offering DDoS mitigation services or 3.1.1.2. End-customer with multiple upstream transit providers offering DDoS mitigation services. I would expect that all these section be merged into UseCase2.

I also agree with the text in section 3.2.

"""

The DOTS communications model in these scenarios are largely

identical to that described in Section 3.1, except that all the DOTS

communications take place within the same span of administrative

control and the same network. These variations are mainly of

interest from the operational point of view, as they illustrate

processes, procedures, and topological details which are

externalities from the standpoint of the DOTS ecosystem, but which

are of great importance for network operators and DDoS mitigation

service providers.

"""

As a result, I see this section as duplicating of the previous use cases. I would rather add the complementary information as a note added to each use case and remove the distinction between internal external. This would result in restructuring the current section 3 as:

* section 3.1 use case 1

* section 3.2 use case 2

* section 3.3 use case 3

Eventually an additional use case may be added Use Case 2b: where the initiation of the DDoS mitigation is handled by the upstream provider instead of the CPE.

Other comments are added directly in the text:

DOTS R. Dobbins

Internet-Draft Arbor Networks

Intended status: Informational D. Migault

Expires: May 17, 2018 Ericsson

S. Fouant

R. Moskowitz

HTT Consulting

N. Teague

Verisign

L. Xia

Huawei

K. Nishizuka

NTT Communications

November 13, 2017

Use cases for DDoS Open Threat Signaling

draft-ietf-dots-use-cases-09

Abstract

The DDoS Open Threat Signaling (DOTS) effort is intended to provide a

protocol to facilitate interoperability between multivendor DDoS

mitigation solutions and services. This document presents use cases

which describe the interactions expected between the DOTS components

as well as DOTS messaging exchanges. The purpose of describing use

cases is to identify the interacting DOTS components, 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 17, 2018.

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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 . . . . . . . . . . . . . . . . . . . . . . . . 2

2. Terminology and Acronyms . . . . . . . . . . . . . . . . . . 3

2.1. Requirements Terminology . . . . . . . . . . . . . . . . 4

3. Use Cases Scenarios . . . . . . . . . . . . . . . . . . . . . 4

3.1. Inter-domain Use Cases . . . . . . . . . . . . . . . . . 4

3.1.1. Upstream Transit Providers Offering DDoS Mitigation

Services . . . . . . . . . . . . . . . . . . . . . . 5

3.1.2. Overlay MSSPs Offering DDoS Mitigation Services . . . 10

3.1.3. Examples of DOTS clients integrated with

applications, services, and network infrastructure

devices . . . . . . . . . . . . . . . . . . . . . . . 12

3.2. Intra-domain Use Cases . . . . . . . . . . . . . . . . . 13

3.2.1. Suppression of outbound DDoS traffic originating from

a consumer broadband access network . . . . . . . . . 14

3.2.2. Home Network DDoS Detection Collaboration for ISP

network management . . . . . . . . . . . . . . . . . 16

3.2.3. DDoS Orchestration . . . . . . . . . . . . . . . . . 19

4. Security Considerations . . . . . . . . . . . . . . . . . . . 21

5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 22

6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 22

7. References . . . . . . . . . . . . . . . . . . . . . . . . . 22

7.1. Normative References . . . . . . . . . . . . . . . . . . 22

7.2. Informative References . . . . . . . . . . . . . . . . . 22

Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 22

1. Introduction

Currently, distributed denial-of-service (DDoS) attack mitigation

solutions are largely based upon siloed, proprietary communications

schemes which result in vendor lock-in. As a side-effect, this makes

the configuration, provisioning, operation, and activation of these

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solutions a highly manual and often time-consuming process.

Additionally, coordination of multiple DDoS mitigation solutions

simultaneously engaged in defending the same organization (resources)

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 specify a

protocol that facilitates interoperability between multivendor DDoS

mitigation solutions and ensures more automation in term of

mitigation requests and attack characterization patterns. As DDoS

solutions are broadly heterogeneous among vendors, the primary goal

of DOTS is to provide high-level interaction amongst differeing DDoS

solutions, such as initiating or terminating DDoS mitigation

assistance.

It should be noted that DOTS is not intended toperform orchestration

functions; rather, DOTS is intended to allowdevices, services, and

applications to request DDoS attack mitigation assistance and receive

mitigation status updates.

These use cases are expected to provide inputs for the design of the

DOTS protocol(s).

2. Terminology and Acronyms

This document makes use of the terms defined in

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

In addition, this document introduces the following terms:

Inter-domain: a DOTS communications relationship between distinct

organizations with separate spans of administrative control.

Typical inter-domain DOTS communication relationships would be

between a DDoS mitigation service provider and an end-customer who

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-domain: a DOTS communications relationship between various

(network) elements that are owned and operated by the same

administrative entity. A typical intra-domain DOTS communications

relationship would be between DOTS agents [I-D.ietf-dots-

requirements] within the same organization.

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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].

3. Use Cases Scenarios

This section provides a high-level description of scenarios addressed

by DOTS. In both sub-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 entities depends, for

example, on the characteristic or functionality of the entity itself,

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 attack telemetry 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.

3.1. Inter-domain Use Cases

Inter-domain DOTS deployment scenarios encompass two or more distinct

spans of administrative control. A typical inter-domain DOTS

deployment may consist of an endpoint network such as an Internet-

connected enterprise requesting DDoS mitigation assistance from one

or more upstream transit providers offering DDoS mitigation services,

or from a topologically-distant MSSP offering cloud-based overlay

DDoS mitigation services. DOTS may also be used to facilitate

coordination of DDoS mitigation activities between mitigation

providers.

Coordination between organizations making use of DOTS in such

scenarios is necessary. Along with DOTS-specific tasks such as DOTS

peering and validating the exchange of DOTS messaging between the

relevant organizations, externalities relating to routing

advertisements, authoritative DNS records (for DNS-based diversion),

network access policies for DOTS nodes, service-level agreements

(SLAs), and DDoS mitigation provisioning are required.

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3.1.1. Upstream Transit Providers Offering DDoS Mitigation Services

The use-cases in this section reflect scenarios in which the

immediate upstream transit network(s) offer DDoS mitigation services

to their end-customers. The DOTS communications models in these use-

cases are largely identical with that decribed in Section 3.1.1.1,

with the exceptions of Section 3.1.1.4 and Section 3.1.1.5. These

variations are mainly of interest from the operational point of view,

as they illustrate processes, procedures, and topological details

which are externalities from the standpoint of the DOTS ecosystem,

but which are of great importance for network operators and DDoS

mitigation service providers.

3.1.1.1. End-customer with a single upstream transit provider offering

DDoS mitigation services

In this scenario, an enterprise network with self-hosted Internet-

facing properties such as Web servers, authoritative DNS servers, and

VoIP PBXes has an intelligent DDoS mitigation system (IDMS) deployed

to protect those servers and applications from DDoS attacks. In

addition to their on-premise DDoS defense capability, they have

contracted with their Internet transit provider for DDoS mitigation

services which threaten to overwhelm their transit link bandwidth.

The IDMS is configured such that if the incoming Internet traffic

volume exceeds 50% of the provisioned upstream Internet transit link

capacity, the IDMS will request DDoS mitigation assistance from the

upstream transit provider.

The requests to trigger, manage, and finalize a DDoS mitigation

between the enterprise IDMS and the transit provider is performed

using DOTS. The enterprise IDMS implements a DOTS client while the

transit provider implements a DOTS server which is integrated with

their DDoS mitigation orchestration system.

When the IDMS detects an inbound DDoS attack targeting the enterprise

servers and applications, it immediately begins mitigating the

attack.

During the course of the attack, the inbound traffic volume exceeds

the 50% threshold; the IDMS DOTS client signals the DOTS server on

the upstream transit provider network to initiate DDoS mitigation.

The DOTS server signals the DOTS client that it can service this

request, and mitigation is initiated on the transit provider network.

Over the course of the attack, the DOTS server on the transit

provider network periodically signals the DOTS client on the

enterprise IDMS in order to provide mitigation status information,

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statistics related to DDoS attack traffic mitigation, and related

information. Once the DDoS attack has ended, the DOTS server signals

the enterprise IDMS DOTS client that the attack has subsided.

The enterprise IDMS then requests that DDoS mitigation services on

the upstream transit provider network be terminated. The DOTS server

on the transit provider network receives this request, communicates

with the transit provider orchestration system controlling its DDoS

mitigation system to terminate attack mitigation, and once the

mitigation has ended, confirms the end of upstream DDoS mitigation

service to the enterprise IDMS DOTS client.

Note that communications between the enterprise DOTS client and the

upstream transit provider DOTS server may take place in-band within

the main Internet transit link between the enterprise and the transit

provider; out-of-band via a separate, dedicated wireline network link

utilized solely for DOTS signaling; or out-of-band via some other

form of network connectivity such as a third-party wireless 4G

network link.

The following is an overview of the DOTS communication model for this

use-case:

(a) A DDoS attack is initiated against online properties of an

organization which has deployed a DOTS-client-capable IDMS.

(b) The IDMS detects, classifies, and begins mitigating the DDoS

attack.

mitigate the DDoS attack is insufficient, and utilize its DOTS client

functionality to send a DOTS mitigation service initiation request to

one or more DOTS servers residing on the upstream transit networks.

This DOTS mitigation service initiation request is automatically

initiated by the DOTS client.

(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 client, and initiate situationally-

appropriate DDoS mitigation service.

(e) The DOTS servers transmit a DOTS service status message to the

DOTS client 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 DOTS client.

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(g) While DDoS mitigation services are active, the DOTS client may

optionally regularly transmit DOTS mitigation efficacy updates to the

DOTS server.

(h) When the upstream DDoS mitigators determine that the DDoS attack

has ceased, they indicate this change in status to the DOTS server.

<mglt>I see that the upstream provides measurements, but it seems that the end of the attack should be determined by the client based on the indicators of the server. More specifically, when an attack reaches picks every 15 min, maybe the client is better of remaining under the protection of the upstream mitigation. Maybe we could clarify this point but to me it could be removed.</mglt>

(i) The DOTS server transmist a DOTS mitigation status update to the

DOTS client indicating that the DDoS attack has ceased.

(j) The DOTS client transmits a DOTS mitigation service termination

request to the DOTS server.

(k) The DOTS server terminates DDoS mitigation service.

<mglt> I do not think that l and m brings much information to understand the use-case. It seems more a protocol issue when both parties must ensure they are in synch. I would remove l and m .</mglt>

(l) The DOTS server transmis a DOTS mitigation status update to the

DOTS client indicating that DDoS mitigation services have been

terminated.

(m) The DOTS client transmits a DOTS mitigation termination status

acknowledgement to the DOTS servers.

3.1.1.2. End-customer with multiple upstream transit providers offering

DDoS mitigation services

This scenario shares many characteristics with Section 3.1.1.1, but

with the key difference that the enterprise in question is multi-

homed, i.e., has two or more upstream transit providers, and that

they all provide DDoS mitigation services.

In most cases, the communications model for a multi-homed model would

be the same as in the single-homed model, merely duplicated in

parallel. However, if two or more of the upstream transit providers

have entered into a mutual DDoS mitigation agreement and have

established DOTS peering relationships, DDoS mitigation status

messages may exchanged between their respective DOTS servers in order

to provide a more complete picture of the DDoS attack scope. This

will also allow for either automated or operator-assisted

programmatic cooperative DDoS mitigation activities on the part of

the DOTS-peered transit providers.

The addtional DOTS communications between the upstream transit

providers will consist of mitigation start, mitigation status, and

mitigation termination messages.

<mglt>My very personal opinion is that this use case is very similar and straight forward to the previous one. I would remove this section.</mglt>

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3.1.1.3. End-customer with multiple upstream transit providers, but

only a single upstream transit provider offering DDoS

mitigation services

This scenario is similar to that outlined in Section 3.1.1.2;

however, only one of the upstream transit providers in question

offers DDoS mitigation services. In this situation, the enterprise

would cease advertising the relevant network prefixes via the transit

providers which do not provide DDoS mitigation services - or, in the

case where the enterprise does not control its own routing, request

that the upstream transit providers which do not offer DDoS

mitigation services stop advertising the relevant network prefixes on

their behalf.

Once it has been determined that the DDoS attack has ceased, the

enterprise once again announces the relevant routes to the upstream

transit providers which do not offer DDoS mitigation services, or

requests that they resume announcing the relevant routes on behalf of

the enterprise.

Note that falling back to a single transit provider has the effect of

reducing available inbound transit bandwidth during a DDoS attack.

Without proper planning and sufficient provisioning of both the link

capacity and DDoS mitigation capacity of the sole transit provider

offering DDoS mitigation services, this reduction of available

bandwidth could lead to network link congestion caused by legitimate

inbound network traffic. Therefore, careful planning and

provisioning of both upstream transit bandwidth as well as DDoS

mitigation capacity is required in scenarios of this nature.

The withdrawal and announcement of routing prefixes described in this

use-case falls outside the scope of DOTS, although they could

conceivably be triggered as a result of provider-specific

orchestration triggered by the receipt of specific DOTS messages from

the enterprise in question.

<mglt>3.1.1.2 and 3.1.1.3 describes a need to manage mitigation services when those are associated to a specific link. I do not think that is necessary to have these examples, but I agree that 3.1.1.3 may be interesting. If we decide to keep them I would merge them into a single section.</mglt>

3.1.1.4. End-customer with an upstream transit provider offering DDoS

mitigation services on an ongoing basis

This scenario is similar to that described in Section 3.1.1.1, except

that due to the lack of a capable local IDMS solution, strict uptime

requirements, or other considerations, the end-customer has

previously arranged for continuous active DDoS mitigation coverage;

thus, the concepts of initiating or terminating DDoS mitigation

services do not apply.

During an attack, the DOTS server on the upstream transit provider

network immediately notifies the DOTS client on the enterprise

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network about the attack and periodically signals the DOTS client in

order to provide mitigation status information and related

information. The end-customer may then use this information to add

capacity or implement configuration changes intended to increase

resilience, to plan maintenance windows or changes to routing

policies, etc.

3.1.1.5. End-customer with an upstream transit provider offering DDoS

mitigation services, but DDoS mitigation service is refused

This scenario is similar to that described in Section 3.1.1.1, except

that the upstream transit provider is unable to honor the DDoS

mitigation service request from the end-customer due to mitigation

capacity limitations, technical faults, or other circumstances. The

end-customer DOTS client may be configured to make repeated attempts

to engage DDoS mitigation service from the refusing provider, or

alternately may be configured to request DDoS mitigation service from

alternate providers.

<mglt> I believe that the text above is sufficient and shoudl be moved to 3.1.1.1. The text below is straight forward.</mglt>

The following is an overview of the DOTS communication model for this

use-case:

(a) A DDoS attack is initiated against online properties of an

organization which has deployed a DOTS-client-capable IDMS.

(b) The IDMS detects, classifies, and begins mitigating the DDoS

attack.

mitigate the DDoS attack is insufficient, and utilizes its DOTS

client functionality to send a DOTS mitigation service initiation

request to a DOTS server residing on an upstream transit network.

(d) The DOTS servers which receives the DOTS mitigation service

initiation requests determines that it has been configured to honor

requests from the requesting DOTS client, and attempts to initiate

situationally-appropriate DDoS mitigation service.

(e) The DDoS mitigators on the upstream network report back to the

DOTS server 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.

(f) The DOTS servers transmits a DOTS service status message to the

DOTS client indicating that upstream DDoS mitigation service cannot

be initiated as requested.

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(g) The DOTS client may optionally regularly re-transmit DOTS

mitigation status request messages to the DOTS server until receiving

acknowledgement that DDos mitigation services have been initiated.

(h) The DOTS client may optionally transmit a DOTS mitigation service

initiation request to a DOTS server 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 client determines

that the DDoS attack volume has decreased to a level and/or

complexity which it can successfully mitigate; the DDoS attack has

ceased; or manual intervention by personnel of the requesting

organization has taken place.

3.1.2. Overlay MSSPs Offering DDoS Mitigation Services

The use-cases in this section reflect scenarios in which

topologically-distant managed security service providers (MSSPs)

offer DDoS mitigation services to end-customers. The DOTS

communications models in these use-cases are largely identical with

that decribed in Section 3.1.1.1. These variations are mainly of

interest from the operational point of view, as they illustrate

processes, procedures, and topological details which are

externalities from the standpoint of the DOTS ecosystem, but which

are of great importance for network operators and DDoS mitigation

service providers.

3.1.2.1. End-customer with an overlay DDoS mitigation managed security

service provider (MSSP)

This use case details an enterprise that has a local DDoS detection

and classification capability and may or may not have an on-premise

mitigation capability. The enterprise is contracted with an overlay

DDoS mitigation MSSP, topologically distant from the enterprise

network (i.e., not a direct upstream transit provider), which can

redirect (divert) traffic away from the enterprise, provide DDoS

mitigation services services, and then forward (re-inject) legitimate

traffic to the enterprise on an on-demand basis. In this scenario,

diversion of Internet traffic destined for the enterprise network

into the overlay DDoS mitigation MSSP network is typically

accomplished via eBGP announcements of the relevant enterprise

network CIDR blocks, or via authoritative DNS subdomain-based

mechanisms (other mechanisms are not precluded, these are merely the

most common ones in use today).

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The enterprise determines thresholds at which a request for

mitigation is triggered indicating to the MSSP that inbound network

traffic should be diverted into the MSSP network and that DDoS

mitigation should be initiated. The enterprise may also elect to

manually request diversion and mitigation via the MSSP network as

desired.

The communications required to initiate, manage, and terminate active

DDoS mitigation by the MSSP is performed using DOTS. The enterprise

DDoS detection/classification system implements a DOTS client, while

the MSSP implements a DOTS server integrated with its DDoS mitigation

orchestration system. One or more out-of-band methods for initiating

a mitigation request, such as a Web portal, a smartphone app, or

voice support hotline, may also be made available by the MSSP.

When an attack is detected, an automated or manual DOTS mitigation

request is generated by the enterprise and sent to the MSSP. The

enterprise DOTS mitigation request is processed by the MSSP DOTS

server, which validates the origin of the request and passes it to

the MSSP DDoS mitigation orchestration system, which then initiates

active DDoS mitigation. This action will usually involve the

diversion of all network traffic destined for the targeted enterprise

into the MSSP DDoS mitigation network, where it will be subjected to

further scrutiny, with DDoS attack traffic filtered by the MSSP.

Successful mitigation of the DDoS attack will not only result

preserving the availability of services and applications resident on

the enterprise network, but will also prevent DDoS attack traffic

from ingressing the networks of the enterprise upstream transit

providers and/or peers.

The MSSP should signal via DOTS to the enterprise that a mitigation

request has been received and acted upon, and should also include an

update of the mitigation status. The MSSP may respond periodically

with additional updates on the mitigation status to in order to

enable the enterprise to make an informed decision on whether to

maintain or terminate the mitigation. An alternative approach would

be for the DOTS client mitigation request to include a time to live

(TTL) for the mitigation, which may also be extended by the client

should the attack still be ongoing as the TTL reaches expiration.

A variation of this use case may be that the enterprise is providing

a DDoS monitoring and analysis service to customers whose networks

may be protected by any one of a number of third-party providers.

The enterprise in question may integrate with these third-party

providers using DOTS and signal accordingly when a customer is

attacked - the MSSP may then manage the life-cycle of the attack

mitigation on behalf of the enterprise.

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3.1.2.2. MSSP as an end-customer requesting overflow DDoS mitigation

assistance from other MSSPs

This is a more complex use-case involving multiple DDoS MSSPs,

whether transit operators, overlay MSSPs, or both. In this scenario,

an MSSP has entered into a pre-arranged DDoS mitigation assistance

agreement with one or more other DDoS MSSPs in order to ensure that

sufficient DDoS mitigation capacity and/or capabilities may be

activated in the event that a given DDoS attack threatens to

overwhelm the ability of a given DDoS MSSP to mitigate the attack on

its own.

BGP-based diversion (including relevant Letters of Authorization, or

LoAs), DNS-based diversion (including relevant LoAs), traffic re-

injection mechanisms such as Generic Routing Encapsulation (GRE)

tunnels, provisioning of DDoS orchestration systems, et. al,. must be

arranged in advance between the DDoS MSSPs which are parties to the

agreement. They should also be tested on a regular basis.

When a DDoS MSSP which is party to the agreement is nearing its

capacity or ability to mitigate a given DDoS attack traffic, the DOTS

client integrated with the MSSP DDoS mitigation orchestration system

signals partner MSSPs to initiate network traffic diversion and DDoS

mitigation activities. Ongoing attack and mitigation status messages

may be passed between the DDoS MSSPs, and between the requesting MSSP

and the ultimate end-customer of the attack.

Once the requesting DDoS MSSP is confident that the DDoS attack has

either ceased or has fallen to levels of traffic/complexity which

they can handle on their own, the requesting DDoS MSSP DOTS client

sends mitigation termination requests to the participating overflow

DDoS MSSPs.

3.1.3. Examples of DOTS clients integrated with applications, services,

and network infrastructure devices

The use-cases in this section reflect scenarios in which DOTS clients

are integrated into devices and services which have heretofore been

unable to request DDoS mitigation services on an as-needed basis.

The DOTS communications models in these use-cases are largely

identical with those decribed in {{interdomain-use-cases}. These

variations are mainly of interest because they illustrate how DOTS

allows DDoS mitigation services to expand in scope and utility.

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3.1.3.1. End-customer operating an application or service with an

integrated DOTS client

In this scenario, a Web server has a built-in mechanism to detect and

classify DDoS attacks, which also incorporates a DOTS client. When

an attack is detected, the self-defense mechanism is activated, and

local DDoS mitigation is initiated.

The DOTS client built into the Web server has been configured to

request DDoS mitigation services from an upstream transit provider or

overlay MSSP once specific attack traffic thresholds have been

reached, or certain network traffic conditions prevail. Once attack

traffic subsides below configured thresholds and/or the specified

network traffic conditions no longer apply, the DOTS client requests

the termination of DDoS mitigation services.

3.1.3.2. End-customer operating a CPE network infrastructure device

with an integrated DOTS client

Similar to the above use-case featuring applications or services with

built-in DDoS attack detection/classification and DOTS client

capabilities, in this scenario, an end-customer network

infrastructure CPE device such as a router, layer-3 switch, firewall,

IDS/IPS, Web application firewall or load-balancer incorporates both

the functionality required to detect and classify incoming DDoS

attacks as well as DOTS client functionality.

3.1.3.3. End-customer with an out-of-band smartphone application

featuring DOTS client capabilities

This scenario would typically apply in a small office or home office

(SOHO) setting, where the end-customer does not have CPE equipment or

software capable of detecting/classifying/mitigating DDoS attack, yet

still has a requirement for on-demand DDoS mitigation services. A

smartphone application containing a DOTS client would be provided by

the upstream transit mitigation provider or overlay DDoS MSSP to the

SOHO end-customer; this application would allow a manual 'panic-

button' to request the initiation and termination of DDoS mitigation

services. The end-customer DOTS client application will display

mitigation status information while DDoS mitigation activities are

taking place.

3.2. Intra-domain Use Cases

While many of the DOTS-specific elements of inter-domain DOTS

deployment scenarios apply to intra-domain scenarios, it is expected

that many externalities such as coordination of and authorization for

routing advertisements and authoritative DNS updates may be automated

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to a higher degree than is practicable in inter-domain scenarios,

given that the scope of required activities and authorizations are

confined to a single organization. In theory, provisioning and

change-control related both to DOTS itself as well as relevant

externalities may require less administrative overhead and less

implementation lead-times.

The scope of potential DDoS mitigation actions may also be broader in

intra-organizational scenarios, as presumably an organization will

have a higher degree of autonomy with regards to both techically and

administratively feasible activities.

The DOTS communications model in these scenarios are largely

identical to that described in Section 3.1, except that all the DOTS

communications take place within the same span of administrative

control and the same network. These variations are mainly of

interest from the operational point of view, as they illustrate

processes, procedures, and topological details which are

externalities from the standpoint of the DOTS ecosystem, but which

are of great importance for network operators and DDoS mitigation

service providers.

3.2.1. Suppression of outbound DDoS traffic originating from a consumer

broadband access network

While most DDoS defenses concentrate on inbound DDoS attacks

ingressing from direct peering links or upstream transit providers,

the DDoS attack traffic in question originates from one or more

Internet-connected networks. In some cases, compromised devices

residing on the local networks of broadband access customers are used

to directly generate this DDoS attack traffic; in others,

misconfigured devices residing on said local customer networks are

exploited by attackers to launch reflection/amplification DDoS

attacks. In either scenario, the outbound DDoS traffic emanating

from these devices can be just as disruptive as an inbound DDoS

attack, and can cause disruption for substantial proportions of the

broadband access network operator's customer base.

Some broadband access network operators provide CPE devices (DSL

modems/routers, cablemodems, FTTH routers, etc.) to their end-

customers. Others allow end-customers to provide their own CPE

devices. Many will either provide CPE devices or allow end-customers

to supply their own.

Broadband access network operators typically have mechanisms to

detect and classify both inbound and outbound DDoS attacks, utilizing

flow telemetry exported from their peering/transit and customer

aggregation routers. In the event of an outbound DDoS attack, they

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may make use of internally-developed systems which leverage their

subscriber-management systems to de-provision end-customers who are

sourcing outbound DDoS traffic; in some cases, they may have

implemented quarantine systems to block all outbound traffic sourced

from the offending end-customers. In either case, the perceived

disruption of the end-customer's Internet access often prompts a

help-desk call, which erodes the margins of the broadband access

provider and can cause end-customer dissatisfaction.

Increasingly, CPE devices themselves are targeted by attackers who

exploit security flaws in these devices in order to compromise them

and subsume them into botnets, and then leverage them to launch

outbound DDoS attacks. In all of the described scenarios, the end-

customers are unaware that their computers and/or CPE devices have

been compromised and are being used to launch outbound DDoS attacks -

however, they may notice a degradation of their Internet connectivity

as a result of outbound bandwidth consumption or other disruption.

By deploying DOTS-enabled telemetry systems and CPE devices (and

possibly requiring DOTS functionality in customer-provided CPE

devices), broadband access providers can utilize a standards-based

mechanism to suppress outbound DDoS attack traffic while optionally

allowing legitimate end-customer traffic to proceed unmolested.

In order to achieve this capability, the telemetry analysis system

utilized by the broadband access provider must have DOTS client

functionality, and the end-customer CPE devices must have DOTS server

functionality. When the telemetry analysis system detects and

classifies an outbound DDoS attack sourced from one or more end-

customer networks/devices, the DOTS client of the telemetry analysis

system sends a DOTS request to the DOTS server implemented on the CPE

devices, requesting local mitigation assistance in suppressing either

the identified outbound DDoS traffic, or all outbound traffic sourced

from the end-customer networks/devices. The DOTS server residing

within the CPE device(s) would then perform predefined actions such

as implementing on-board access-control lists (ACLs) to suppress the

outbound traffic in question and prevent it from leaving the local

end-customer network(s).

Broadband access network operators may choose to implement a

quarantine of all or selected network traffic originating from end-

customer networks/devices which are sourcing outbound DDoS traffic,

redirecting traffic from interactive applications such as Web

browsers to an internal portal which informs the end-customer of the

quarantine action, and providing instructions for self-remediation

and/or helpdesk contact information.

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Quarantine systems for broadband access networks are typically

custom-developed and -maintained, and are generally deployed only by

a relatively small number of broadband access providers with

considerable internal software development and support capabilities.

By requiring the manufacturers of operator-supplied CPE devices to

implement DOTS server functionality, and requiring customer-provided

CPE devices to feature DOTS server functionality, broadband access

network operators who previously could not afford the development

expense of creating custom quarantine systems to integrate DOTS-

enabled network telemetry systems to act as DOTS clients and perform

effective quarantine of end-customer networks and devices until such

time as they have been remediated.

The DOTS communications model in this scenario resembles that

described in Section 3.1.1.1, except that all the DOTS communications

take place within the same span of administrative control and the

same network.

3.2.2. Home Network DDoS Detection Collaboration for ISP network

management

Home networks run with (limited) bandwidth as well as limited routing

resources, while they are expected to provide services reachable from

the outside [RFC7368]. This makes such networks some easy targets to

DDoS attacks via their WAN interface. As these DDoS attacks are easy

to perform, they may remain undetected by the upstream ISP. When the

CPE is congested, the customer is likely to call the ISP hotline. In

order to improve the quality of experience of the connectivity as

well as to automate the request for DDoS mitigation, ISPs are likely

to consider a standard mean for CPEs to automatically inform a

dedicated service mitigation platform when they are under a suspected

DDoS.

Note also that this section only considers DDoS attacks CPE or

services in the home network are encountering. This differs from

DDoS attacks the CPE or any device within the home network may take

part of - such as botnets. In the later attacks, the home network

generates traffic under the control of a botmaster. Such attacks may

only be detected once the attacks have been characterized. It would

be tempting to consider a feature in the DOTS protocol to allow a

DOTS server to inform a CPE that some suspect traffic is being sent

by the CPE so that appropriate actions are undertaken by the CPE/

user. Nevertheless, this feature would require some interaction with

the CPE administrator. Such scenario is outside the scope of this

document.

In this use case, ISPs are willing to prevent their customer

undergoing DDoS attacks in order to enhance the quality of experience

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of their customers, to avoid unnecessary costly call on hot lines as

well as to optimize the bandwidth of their network. A key challenge

for the ISP is to detect DDoS attacks. In fact, DDoS detection is

not only fine grained but is also expected to be different for each

home network or small businesses networks (SOHO), and the ISP is

unlikely to have sufficient resource to inspect the traffic of all

its customers.

In order to address these challenges, ISPs are delegating the DDoS

detection to CPE of home network or SOHO. Outsourcing the detection

on the CPE provides the following advantages to the ISP: 1) Avoid the

ISP to dedicate a huge amount of resource for deep packet inspection

over a large amount of traffic with a specific security policies

associated to each home network. It is expected that such traffic

only constitutes a small fraction of the total traffic the ISP is

responsible for. 2) DDoS detection is deployed in a scalable way. 3)

Provide more deterministic DDoS attack detection. For example, what

could be suspected to be an UDP flood by the ISP may be consented by

the terminating point hosted in the home network or SOHO. In fact,

without specific home network security policies, the ISP is likely to

detect DDoS attack over regular traffic or to miss DDoS attacks

targeting a specific home network or CPE. In the first case, this

would result in the ISP spending unnecessary resources and in the

second case this would directly impact the quality of experience of

the customer.

Note that in this scenario slightly differs from the "Enterprise with

an upstream transit provider DDoS mitigation Service" scenario

described in Section 3.1.1. In this scenario, the detection DDoS is

motivated by the ISP in order to operate appropriately its network.

For that purpose, it requires some collaboration with the home

network. In Section 3.1.1, the target network requests a mitigation

service from the upstream transit provider in order to operate its

services.

Even though the motivations differ, there are still significant

advantages for the home network to collaborate. On the home network

or SOHO perspective such collaboration provides the following

advantages: 1) If it removes the flows contributing to a DDoS

attacks, then it enhances the quality of experience of the users of

the targeted services or the entire home network. 2) If mitigation is

being handled by the ISP rather then the home network, then it

reduces the management of DDoS attacks by the network administrator

which involves detection as well as mitigation as well as the

provisioning of extra resources. 3) If the DDoS detection is based on

information specific to the home network, such as for example the

description of the services, the hosts capacities or the network

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topology, then performing the DDoS detection by the home network

instead of the ISP avoids the home network to leak private

information to the ISP. In that sense, it better preserves the home

network or SOHO privacy while enabling a better detection. However,

the request for mitigation may still leak some informations. ISPs

must not retrieve sensitive data without the consent of the user.

This is usually captured in administrative contracts that are out of

scope of this document.

When the CPE suspects an attack, it notifies automatically or the

ISP. The contact address of the DDoS Mitigation service of the ISP

may be hard coded or may be configured manually or automatically

(e.g., eventually the DHCP server may provide the DDoS mitigation

service via specific DHCP options).

The communication to trigger a DDoS mitigation between the home

network and the ISP is performed using DOTS. The home network CPE

implements a DOTS client while the ISP implements a DOTS server.

The DOTS client on the CPE monitors the status of CPE's resource and

WAN link bandwidth usage. If something unusual happens based on

preconfigured throughput, traffic patter, explicit action from the

user, or some heuristics methods, the DOTS client sends a DOTS

mitigation request to the ISP DOTS server. Typically, a default

configuration with no additional information associated to the DOTS

mitigation request is expected. The ISP derives traffic to mitigate

from the CPE IP address.

In some cases, the DOTS mitigation request contains options such as

some IP addresses or prefixes that belongs to a whitelist or a

blacklist. In this case, the white and black lists are not

associated to some analysis performed by the CPE - as the CPE is

clearly not expected to analyze such attacks. Instead these are part

of some configuration parameters. For example, in the case of small

business, one may indicate specific legitimate IP addresses such as

those used for VPNs, or third party services the company is likely to

set a session. Similarly, the CPE may provide the IP addresses

targeting the assets to be protected inside the network. Note that

the IP address is the IP address used to reach the asset from the

internet, and as such is expected to be globally routable. Such

options may include the IP address as well as a service description.

Similarly to the previous blacklist and whitelist, such information

are likely not derived from a traffic analysis performed by the CPE,

but instead are more related to configuration parameters.

Upon receiving the DOTS mitigation request, the DOTS server

acknowledges its reception and confirms DDoS mitigation starts or

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not. Such feed back is mostly to avoid retransmission of the

request.

Note that the ISP is connected to multiple CPEs and as such the CPE

can potentially perform DDoS attack to the DOTS server. ISP may use

gateways to absorbs the traffic. These gateways, will typically

aggregate a smaller number of CPEs and retransmit to the destination

DOTS Server a selected information. Note that such gateways may

somehow act as a DOTS relay, which is implemented with a DOTS Server

and a DOTS Client. Note also that the case of a large DDoS attack

targeting simultaneously multiple CPEs is expected to be detected and

mitigated by the upstream architecture, eventually without DOTS

alerts sent by each single CPE.

ISP may activate mitigation 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 ISP.

It is unlikely the CPE will follow the status of the mitigation. The

ISP is only expected to inform the CPE the mitigation has been

stopped.

Upon receipt of such notification the CPE may, for example, re-

activate the monitoring jobs and thus is likely to provide some

further DOTS alert.

3.2.3. DDoS Orchestration

In this use case, one or more DDoS telemetry systems or monitoring

devices such as a flow telemetry collector monitor a network --

typically an ISP network. Upon detection of a DDoS attack, these

telemetry systems alert an orchestrator in charge of coordinating the

various DDoS mitigation systems within the domain. The telemetry

systems may be configured to provide necessary and useful pieces of

information, such as a preliminary analysis of the observation to the

orchestrator.

The orchestrator analyses the various information it receives from

specialized equipement, and elaborates one or multiple DDoS

mitigation strategies. In some case, a manual confirmation may also

be required to choose a proposed strategy or to initiate a DDoS

mitigation. The DDoS mitigation may consist of multiple steps such

as configuring the network, various hardware, or updating already

instantiated DDoS mitigation functions. In some cases, some specific

virtual DDoS mitigation functions must be instantiated and properly

ordered. Eventually, the coordination of the mitigation may involve

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external DDoS resources such as a transit provider (Section 3.1.1.1)

or an MSSP (Section 3.1.2.1).

The communications used to trigger a DDoS mitigation between the

telemetry and monitoring systems and the orchestrator is performed

using DOTS. The telemetry systems implements a DOTS client while the

orchestrator implements a DOTS server.

The communication between a network administrator and the

orchestrator is also performed using DOTS. The network administrator

via its web interfaces implements a DOTS client, while the

Orchestrator implements a DOTS server.

The communication between the Orchestrator and the DDoS mitigation

systems is performed using DOTS. The Orchestrator implements a DOTS

client while the DDoS mitigation systems implement a DOTS server.

The configuration aspects of each DDoS mitigation system, as well as

the instantiations of DDoS mitigation functions or network

configuration is not part of DOTS. Similarly, the discovery of

available DDoS mitigation functions is not part of DOTS.

+----------+

| network |C

| adminis |<-+

| trator | |

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

| (internal)

+----------+ | S+--------------+ +-----------+

|telemetry/| +->| |C S| DDoS |+

|monitoring|<--->| Orchestrator |<--->| mitigation||

|systems |C S| |<-+ | systems ||

+----------+ +--------------+C | +-----------+|

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

| (external)

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

| S| DDoS |

+->| mitigation|

| systems |

+-----------+

* C is for DOTS client functionality

* S is for DOTS server functionality

Figure 1: DDoS Orchestration

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The telemetry systems monitor various traffic network and perform

their measurement tasks. They are configured so that when an event

or some measurements reach a predefined level to report a DOTS

mitigation request to the Orchestrator. The DOTS mitigation request

may be associated with some element such as specific reporting.

Upon receipt of the DOTS mitigation request from the telemetry

system, the Orchestrator responds with an acknowledgement, to avoid

retransmission of the request for mitigation. The status of the DDoS

mitigation indicates the Orchestrator is in an analysing phase. The

Orchestrator begins collecting various information from various

telemetry systems in order to correlate the measurements and provide

an analysis of the event. Eventually, the Orchestrator may ask

additional information to the telemetry system, however, the

collection of these information is performed outside DOTS.

The orchestrator may be configured to start a DDoS mitigation upon

approval from a network administrator. The analysis from the

orchestrator is reported to the network administrator via a web

interface. If the network administrator decides to start the

mitigation, she orders through her web interface a DOTS client to

send a request for DDoS mitigation. This request is expected to be

associated with a context that identifies the DDoS mitigation

selected.

Upon receiving the DOTS request for DDoS mitigation from the network

administrator, the orchestrator orchestrates the DDoS mitigation

according to the specified strategy. Its status indicates the DDoS

mitigation is starting while not effective.

Orchestration of the DDoS mitigation systems works similarly as

described in Section 3.1.1.1 and Section 3.1.2.1. The Orchestrator

indicates with its status whether the DDoS Mitigation is effective.

When the DDoS mitigation is finished on the DDoS mitigation systems,

the orchestrator indicates to the Telemetry systems as well as to the

network administrator the DDoS mitigation is finished.

4. Security Considerations

DOTS is at risk from four primary forms of attack: DOTS agent

impersonation, traffic injection, signal-blocking, and DDoS attacks.

Associated security requirements and additional ones are defined in

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

These security risks can be managed through current secure

communications best practices.

DOTS is not subject to anything new or unique in this area.

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5. IANA Considerations

No IANA considerations exist for this document at this time.

6. Acknowledgments

The authors would like to thank among others Tirumaleswar Reddy;

Andrew Mortensen; Mohamed Boucadaire; Artyom Gavrichenkov; and the

DOTS WG chairs, Roman D. Danyliw and Tobias Gondrom, for their

valuable feedback.

7. References

7.1. Normative References

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate

Requirement Levels", BCP 14, RFC 2119,

DOI 10.17487/RFC2119, March 1997, <https://www.rfc-

editor.org/info/rfc2119>.

7.2. Informative References

[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-07 (work in

progress), October 2017.

[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,

<https://www.rfc-editor.org/info/rfc6335>.

[RFC7368] Chown, T., Ed., Arkko, J., Brandt, A., Troan, O., and J.

Weil, "IPv6 Home Networking Architecture Principles",

RFC 7368, DOI 10.17487/RFC7368, October 2014,

<https://www.rfc-editor.org/info/rfc7368>.

Authors' Addresses

Roland Dobbins

Arbor Networks

Singapore

EMail: rdobbins@arbor.net

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Daniel Migault

Ericsson

8400 boulevard Decarie

Montreal, QC H4P 2N2

Canada

EMail: daniel.migault@ericsson.com

Stefan Fouant

USA

EMail: stefan.fouant@copperriverit.com

Robert Moskowitz

HTT Consulting

Oak Park, MI 48237

USA

EMail: rgm@labs.htt-consult.com

Nik Teague

Verisign

12061 Bluemont Way

Reston, VA 20190

EMail: nteague@verisign.com

Liang Xia

Huawei

No. 101, Software Avenue, Yuhuatai District

Nanjing

China

EMail: Frank.xialiang@huawei.com

Kaname Nishizuka

NTT Communications

GranPark 16F 3-4-1 Shibaura, Minato-ku

Tokyo 108-8118

Japan

EMail: kaname@nttv6.jp

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