draft-ietf-dots-requirements-22.txt   rfc8612.txt 
DOTS A. Mortensen Internet Engineering Task Force (IETF) A. Mortensen
Internet-Draft Arbor Networks Request for Comments: 8612 Arbor Networks
Intended status: Informational T. Reddy Category: Informational T. Reddy
Expires: September 24, 2019 McAfee ISSN: 2070-1721 McAfee
R. Moskowitz R. Moskowitz
Huawei Huawei
March 23, 2019 May 2019
Distributed Denial of Service (DDoS) Open Threat Signaling Requirements DDoS Open Threat Signaling (DOTS) Requirements
draft-ietf-dots-requirements-22
Abstract Abstract
This document defines the requirements for the Distributed Denial of This document defines the requirements for the Distributed Denial-of-
Service (DDoS) Open Threat Signaling (DOTS) protocols enabling Service (DDoS) Open Threat Signaling (DOTS) protocols enabling
coordinated response to DDoS attacks. coordinated response to DDoS attacks.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This document is not an Internet Standards Track specification; it is
provisions of BCP 78 and BCP 79. published for informational purposes.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months This document is a product of the Internet Engineering Task Force
and may be updated, replaced, or obsoleted by other documents at any (IETF). It represents the consensus of the IETF community. It has
time. It is inappropriate to use Internet-Drafts as reference received public review and has been approved for publication by the
material or to cite them other than as "work in progress." Internet Engineering Steering Group (IESG). Not all documents
approved by the IESG are candidates for any level of Internet
Standard; see Section 2 of RFC 7841.
This Internet-Draft will expire on September 24, 2019. Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc8612.
Copyright Notice Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the Copyright (c) 2019 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of (https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
skipping to change at page 2, line 23 skipping to change at page 2, line 21
2.1. General Requirements . . . . . . . . . . . . . . . . . . 7 2.1. General Requirements . . . . . . . . . . . . . . . . . . 7
2.2. Signal Channel Requirements . . . . . . . . . . . . . . . 8 2.2. Signal Channel Requirements . . . . . . . . . . . . . . . 8
2.3. Data Channel Requirements . . . . . . . . . . . . . . . . 13 2.3. Data Channel Requirements . . . . . . . . . . . . . . . . 13
2.4. Security Requirements . . . . . . . . . . . . . . . . . . 14 2.4. Security Requirements . . . . . . . . . . . . . . . . . . 14
2.5. Data Model Requirements . . . . . . . . . . . . . . . . . 16 2.5. Data Model Requirements . . . . . . . . . . . . . . . . . 16
3. Congestion Control Considerations . . . . . . . . . . . . . . 17 3. Congestion Control Considerations . . . . . . . . . . . . . . 17
3.1. Signal Channel . . . . . . . . . . . . . . . . . . . . . 17 3.1. Signal Channel . . . . . . . . . . . . . . . . . . . . . 17
3.2. Data Channel . . . . . . . . . . . . . . . . . . . . . . 17 3.2. Data Channel . . . . . . . . . . . . . . . . . . . . . . 17
4. Security Considerations . . . . . . . . . . . . . . . . . . . 17 4. Security Considerations . . . . . . . . . . . . . . . . . . . 17
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18
6. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 18 6. References . . . . . . . . . . . . . . . . . . . . . . . . . 18
7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 19 6.1. Normative References . . . . . . . . . . . . . . . . . . 18
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 19 6.2. Informative References . . . . . . . . . . . . . . . . . 20
8.1. Normative References . . . . . . . . . . . . . . . . . . 19 Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 21
8.2. Informative References . . . . . . . . . . . . . . . . . 20 Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 21 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 21
1. Introduction 1. Introduction
1.1. Context and Motivation 1.1. Context and Motivation
Distributed Denial of Service (DDoS) attacks afflict networks Distributed Denial-of-Service (DDoS) attacks afflict networks
connected to the Internet, plaguing network operators at service connected to the Internet, plaguing network operators at service
providers and enterprises around the world. High-volume attacks providers and enterprises around the world. High-volume attacks
saturating inbound links are now common, as attack scale and saturating inbound links are now common as attack scale and frequency
frequency continue to increase. continue to increase.
The prevalence and impact of these DDoS attacks has led to an The prevalence and impact of these DDoS attacks has led to an
increased focus on coordinated attack response. However, many increased focus on coordinated attack response. However, many
enterprises lack the resources or expertise to operate on-premises enterprises lack the resources or expertise to operate on-premise
attack mitigation solutions themselves, or are constrained by local attack mitigation solutions themselves, or are constrained by local
bandwidth limitations. To address such gaps, service providers have bandwidth limitations. To address such gaps, service providers have
begun to offer on-demand traffic scrubbing services, which are begun to offer on-demand traffic scrubbing services, which are
designed to separate the DDoS attack traffic from legitimate traffic designed to separate the DDoS attack traffic from legitimate traffic
and forward only the latter. and forward only the latter.
Today, these services offer proprietary interfaces for subscribers to Today, these services offer proprietary interfaces for subscribers to
request attack mitigation. Such proprietary interfaces tie a request attack mitigation. Such proprietary interfaces tie a
subscriber to a service and limit the abilities of network elements subscriber to a service and limit the abilities of network elements
that would otherwise be capable of participating in attack that would otherwise be capable of participating in attack
mitigation. As a result of signaling interface incompatibility, mitigation. As a result of signaling interface incompatibility,
attack responses may be fragmented or otherwise incomplete, leaving attack responses may be fragmented or otherwise incomplete, leaving
operators in the attack path unable to assist in the defense. operators in the attack path unable to assist in the defense.
A standardized method to coordinate a real-time response among A standardized method to coordinate a real-time response among
involved operators will increase the speed and effectiveness of DDoS involved operators will increase the speed and effectiveness of DDoS
attack mitigation, and reduce the impact of these attacks. This attack mitigation and reduce the impact of these attacks. This
document describes the required characteristics of protocols that document describes the required characteristics of protocols that
enable attack response coordination and mitigation of DDoS attacks. enable attack response coordination and mitigation of DDoS attacks.
DDoS Open Threat Signaling (DOTS) communicates the need for defensive DDoS Open Threat Signaling (DOTS) communicates the need for defensive
action in anticipation of or in response to an attack, but does not action in anticipation of or in response to an attack, but it does
dictate the implementation of these actions. The DOTS use cases are not dictate the implementation of these actions. The DOTS use cases
discussed in [I-D.ietf-dots-use-cases] and the DOTS architecture is are discussed in [DOTS-USE], and the DOTS architecture is discussed
discussed in [I-D.ietf-dots-architecture]. in [DOTS-ARCH].
1.2. Terminology 1.2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
document are to be interpreted as described in BCP14 [RFC2119] "OPTIONAL" in this document are to be interpreted as described in
[RFC8174], when, and only when, they appear in all capitals. These BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitalized words are used to signify the requirements for DOTS capitals, as shown here.
protocols design.
These capitalized words are used to signify the requirements for the
DOTS protocols design.
This document adopts the following terms: This document adopts the following terms:
DDoS: A distributed denial-of-service attack, in which traffic DDoS: A distributed denial-of-service attack in which traffic
originating from multiple sources is directed at a target on a originating from multiple sources is directed at a target on a
network. DDoS attacks are intended to cause a negative impact on network. DDoS attacks are intended to cause a negative impact on
the availability and/or other functionality of an attack target. the availability and/or functionality of an attack target.
Denial-of-service considerations are discussed in detail in Denial-of-service considerations are discussed in detail in
[RFC4732]. [RFC4732].
DDoS attack target: A network connected entity that is the target of DDoS attack target: A network-connected entity that is the target of
a DDoS attack. Potential targets include (but are not limited to) a DDoS attack. Potential targets include (but are not limited to)
network elements, network links, servers, and services. network elements, network links, servers, and services.
DDoS attack telemetry: Collected measurements and behavioral DDoS attack telemetry: Collected measurements and behavioral
characteristics defining the nature of a DDoS attack. characteristics defining the nature of a DDoS attack.
Countermeasure: An action or set of actions focused on recognizing Countermeasure: An action or set of actions focused on recognizing
and filtering out specific types of DDoS attack traffic while and filtering out specific types of DDoS attack traffic while
passing legitimate traffic to the attack target. Distinct passing legitimate traffic to the attack target. Distinct
countermeasures can be layered to defend against attacks combining countermeasures can be layered to defend against attacks combining
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DOTS agent: Any DOTS-aware software module capable of participating DOTS agent: Any DOTS-aware software module capable of participating
in a DOTS signal or data channel. It can be a DOTS client, DOTS in a DOTS signal or data channel. It can be a DOTS client, DOTS
server, or, as a logical agent, a DOTS gateway. server, or, as a logical agent, a DOTS gateway.
DOTS gateway: A DOTS-aware software module resulting from the DOTS gateway: A DOTS-aware software module resulting from the
logical concatenation of the functionality of a DOTS server and a logical concatenation of the functionality of a DOTS server and a
DOTS client into a single DOTS agent. This functionality is DOTS client into a single DOTS agent. This functionality is
analogous to a Session Initiation Protocol (SIP) [RFC3261] Back- analogous to a Session Initiation Protocol (SIP) [RFC3261] Back-
to-Back User Agent (B2BUA) [RFC7092]. A DOTS gateway has a to-Back User Agent (B2BUA) [RFC7092]. A DOTS gateway has a
client-facing side, which behaves as a DOTS server for downstream client-facing side, which behaves as a DOTS server for downstream
clients, and a server-facing side, which performs the role of DOTS clients, and a server-facing side, which performs the role of a
client for upstream DOTS servers. Client-domain DOTS gateways are DOTS client for upstream DOTS servers. Client-domain DOTS
DOTS gateways that are in the DOTS client's domain, while server- gateways are DOTS gateways that are in the DOTS client's domain,
domain DOTS gateways denote DOTS gateways that are in the DOTS while server-domain DOTS gateways denote DOTS gateways that are in
server's domain. A DOTS gateway may terminate multiple discrete the DOTS server's domain. A DOTS gateway may terminate multiple
DOTS client connections and may aggregate these into a single or discrete DOTS client connections and may aggregate these into one
multiple connections. DOTS gateways are described further in or more connections. DOTS gateways are described further in
[I-D.ietf-dots-architecture]. [DOTS-ARCH].
Signal channel: A bidirectional, mutually authenticated Signal channel: A bidirectional, mutually authenticated
communication channel between DOTS agents that is resilient even communication channel between DOTS agents that is resilient even
in conditions leading to severe packet loss, such as a volumetric in conditions leading to severe packet loss such as a volumetric
DDoS attack causing network congestion. DDoS attack causing network congestion.
DOTS signal: A status/control message transmitted over the DOTS signal: A status/control message transmitted over the
authenticated signal channel between DOTS agents, used to indicate authenticated signal channel between DOTS agents, used to indicate
the client's need for mitigation, or to convey the status of any the client's need for mitigation or to convey the status of any
requested mitigation. requested mitigation.
Heartbeat: A message transmitted between DOTS agents over the signal Heartbeat: A message transmitted between DOTS agents over the signal
channel, used as a keep-alive and to measure peer health. channel, used as a keep-alive and to measure peer health.
Data channel: A bidirectional, mutually authenticated communication Data channel: A bidirectional, mutually authenticated communication
channel between two DOTS agents used for infrequent but reliable channel between two DOTS agents used for infrequent but reliable
bulk exchange of data not easily or appropriately communicated bulk exchange of data not easily or appropriately communicated
through the signal channel. Reliable bulk data exchange may not through the signal channel. Reliable bulk data exchange may not
function well or at all during attacks causing network congestion. function well or at all during attacks causing network congestion.
The data channel is not expected to operate in such conditions. The data channel is not expected to operate in such conditions.
Filter: A specification of a matching network traffic flow or set of Filter: A specification of a matching network traffic flow or set of
flows. The filter will typically have a policy associated with flows. The filter will typically have a policy associated with
it, e.g., rate-limiting or discarding matching traffic [RFC4949]. it, e.g., rate-limiting or discarding matching traffic [RFC4949].
Drop-list: A list of filters indicating sources from which traffic Drop-list: A list of filters indicating sources from which traffic
should be blocked, regardless of traffic content. should be blocked regardless of traffic content.
Accept-list: A list of filters indicating sources from which traffic Accept-list: A list of filters indicating sources from which traffic
should always be allowed, regardless of contradictory data gleaned should always be allowed regardless of contradictory data gleaned
in a detected attack. in a detected attack.
Multi-homed DOTS client: A DOTS client exchanging messages with Multihomed DOTS client: A DOTS client exchanging messages with
multiple DOTS servers, each in a separate administrative domain. multiple DOTS servers, each in a separate administrative domain.
2. Requirements 2. Requirements
The expected layout and interactions amongst DOTS entities is The expected layout and interactions amongst DOTS entities is
described in the DOTS Architecture [I-D.ietf-dots-architecture]. described in the DOTS Architecture [DOTS-ARCH].
The goal of the DOTS requirements specification is to specify the The goal of the DOTS requirements specification is to specify the
requirements for DOTS signal channel and data channel protocols that requirements for DOTS signal channel and data channel protocols that
have different application and transport layer requirements. This have different application and transport-layer requirements. This
section describes the required features and characteristics of the section describes the required features and characteristics of the
DOTS protocols. DOTS protocols.
The goal of DOTS protocols is to enable and manage mitigation on The goal of DOTS protocols is to enable and manage mitigation on
behalf of a network domain or resource which is or may become the behalf of a network domain or resource that is or may become the
focus of a DDoS attack. An active DDoS attack against the entity focus of a DDoS attack. An active DDoS attack against the entity
controlling the DOTS client need not be present before establishing a controlling the DOTS client need not be present before establishing a
communication channel between DOTS agents. Indeed, establishing a communication channel between DOTS agents. Indeed, establishing a
relationship with peer DOTS agents during normal network conditions relationship with peer DOTS agents during normal network conditions
provides the foundation for more rapid attack response against future provides the foundation for a more rapid attack response against
attacks, as all interactions setting up DOTS, including any business future attacks, as all interactions setting up DOTS, including any
or service level agreements, are already complete. Reachability business or service-level agreements, are already complete.
information of peer DOTS agents is provisioned to a DOTS client using Reachability information of peer DOTS agents is provisioned to a DOTS
a variety of manual or dynamic methods. Once a relationship between client using a variety of manual or dynamic methods. Once a
DOTS agents is established, regular communication between DOTS relationship between DOTS agents is established, regular
clients and servers enables a common understanding of the DOTS communication between DOTS clients and servers enables a common
agents' health and activity. understanding of the DOTS agents' health and activity.
The DOTS protocol must at a minimum make it possible for a DOTS The DOTS protocol must, at a minimum, make it possible for a DOTS
client to request aid mounting a defense against a suspected attack. client to request aid mounting a defense against a suspected attack.
This defense could be coordinated by a DOTS server and include This defense could be coordinated by a DOTS server and include
signaling within or between domains as requested by local operators. signaling within or between domains as requested by local operators.
DOTS clients should similarly be able to withdraw aid requests. DOTS DOTS clients should similarly be able to withdraw aid requests. DOTS
requires no justification from DOTS clients for requests for help, requires no justification from DOTS clients for requests for help,
nor do DOTS clients need to justify withdrawing help requests: the nor do DOTS clients need to justify withdrawing help requests; the
decision is local to the DOTS clients' domain. Multi-homed DOTS decision is local to the DOTS clients' domain. Multihomed DOTS
clients must be able to select the appropriate DOTS server(s) to clients must be able to select the appropriate DOTS server(s) to
which a mitigation request is to be sent. The method for selecting which a mitigation request is to be sent. The method for selecting
the appropriate DOTS server in a multi-homed environment is out of the appropriate DOTS server in a multihomed environment is out of
scope for this document. scope for this document.
DOTS protocol implementations face competing operational goals when DOTS protocol implementations face competing operational goals when
maintaining this bidirectional communication stream. On the one maintaining this bidirectional communication stream. On the one
hand, DOTS must include measures to ensure message confidentiality, hand, DOTS must include measures to ensure message confidentiality,
integrity, authenticity, and replay protection to keep the protocols integrity, authenticity, and replay protection to keep the protocols
from becoming additional vectors for the very attacks it is meant to from becoming additional vectors for the very attacks it is meant to
help fight off. On the other hand, the protocol must be resilient help fight off. On the other hand, the protocol must be resilient
under extremely hostile network conditions, providing continued under extremely hostile network conditions, providing continued
contact between DOTS agents even as attack traffic saturates the contact between DOTS agents even as attack traffic saturates the
link. Such resiliency may be developed several ways, but link. Such resiliency may be developed several ways, but
characteristics such as small message size, asynchronous, redundant characteristics such as small message size, asynchronous
message delivery and minimal connection overhead (when possible given notifications, redundant message delivery, and minimal connection
local network policy) will tend to contribute to the robustness overhead (when possible, given local network policy) will tend to
demanded by a viable DOTS protocol. Operators of peer DOTS-enabled contribute to the robustness demanded by a viable DOTS protocol.
domains may enable quality- or class-of-service traffic tagging to Operators of peer DOTS-enabled domains may enable either quality-of-
increase the probability of successful DOTS signal delivery, but DOTS service or class-of-service traffic tagging to increase the
does not require such policies be in place, and should be viable in probability of successful DOTS signal delivery, but DOTS does not
their absence. require such policies be in place and should be viable in their
absence.
The DOTS server and client must also have some standardized method of The DOTS server and client must also have some standardized method of
defining the scope of any mitigation, as well as managing other defining the scope of any mitigation, as well as managing other
mitigation-related configuration. mitigation-related configurations.
Finally, DOTS should be sufficiently extensible to meet future needs Finally, DOTS should be sufficiently extensible to meet future needs
in coordinated attack defense, although this consideration is in coordinated attack defense, although this consideration is
necessarily superseded by the other operational requirements. necessarily superseded by the other operational requirements.
2.1. General Requirements 2.1. General Requirements
GEN-001 Extensibility: Protocols and data models developed as part GEN-001 Extensibility: Protocols and data models developed as part
of DOTS MUST be extensible in order to keep DOTS adaptable to of DOTS MUST be extensible in order to keep DOTS adaptable to
proprietary DDoS defenses. Future extensions MUST be backward proprietary DDoS defenses. Future extensions MUST be backward
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GEN-002 Resilience and Robustness: The signaling protocol MUST be GEN-002 Resilience and Robustness: The signaling protocol MUST be
designed to maximize the probability of signal delivery even under designed to maximize the probability of signal delivery even under
the severely constrained network conditions caused by attack the severely constrained network conditions caused by attack
traffic. Additional means to enhance the resilience of DOTS traffic. Additional means to enhance the resilience of DOTS
protocols, including when multiple DOTS servers are provisioned to protocols, including when multiple DOTS servers are provisioned to
the DOTS clients, SHOULD be considered. The protocol MUST be the DOTS clients, SHOULD be considered. The protocol MUST be
resilient, that is, continue operating despite message loss and resilient, that is, continue operating despite message loss and
out-of-order or redundant message delivery. In support of out-of-order or redundant message delivery. In support of
signaling protocol robustness, DOTS signals SHOULD be conveyed signaling protocol robustness, DOTS signals SHOULD be conveyed
over transport and application protocols not susceptible to Head over transport and application protocols not susceptible to head-
of Line Blocking. These requirements are at SHOULD strength to of-line blocking. These requirements are at SHOULD strength to
handle middle-boxes and firewall traversal. handle middle-boxes and firewall traversal.
GEN-003 Bulk Data Exchange: Infrequent bulk data exchange between GEN-003 Bulk Data Exchange: Infrequent bulk data exchange between
DOTS agents can also significantly augment attack response DOTS agents can also significantly augment attack response
coordination, permitting such tasks as population of drop- or coordination, permitting such tasks as population of drop- or
accept-listed source addresses; address or prefix group aliasing; accept-listed source addresses, address or prefix group aliasing,
exchange of incident reports; and other hinting or configuration exchange of incident reports, and other hinting or configuration
supplementing attack response. supplementing attack responses.
As the resilience requirements for the DOTS signal channel mandate As the resilience requirements for the DOTS signal channel mandate
small signal message size, a separate, secure data channel a small signal message size, a separate, secure data channel
utilizing a reliable transport protocol MUST be used for bulk data utilizing a reliable transport protocol MUST be used for bulk data
exchange. However, reliable bulk data exchange may not be exchange. However, reliable bulk data exchange may not be
possible during attacks causing network congestion. possible during attacks causing network congestion.
GEN-004 Mitigation Hinting: DOTS clients may have access to attack GEN-004 Mitigation Hinting: DOTS clients may have access to attack
details which can be used to inform mitigation techniques. details that can be used to inform mitigation techniques. Example
Example attack details might include locally collected attack details might include locally collected fingerprints for an
fingerprints for an on-going attack, or anticipated or active on-going attack, or anticipated or active attack focal points
attack focal points based on other threat intelligence. DOTS based on other threat intelligence. DOTS clients MAY send
clients MAY send mitigation hints derived from attack details to mitigation hints derived from attack details to DOTS servers, with
DOTS servers, in the full understanding that the DOTS server MAY the full understanding that the DOTS server MAY ignore mitigation
ignore mitigation hints. Mitigation hints MUST be transmitted hints. Mitigation hints MUST be transmitted across the signal
across the signal channel, as the data channel may not be channel, as the data channel may not be functional during an
functional during an attack. DOTS server handling of mitigation attack. DOTS-server handling of mitigation hints is
hints is implementation-specific. implementation-specific.
GEN-005 Loop Handling: In certain scenarios, typically involving GEN-005 Loop Handling: In certain scenarios, typically involving
misconfiguration of DNS or routing policy, it may be possible for misconfiguration of DNS or routing policy, it may be possible for
communication between DOTS agents to loop. Signal and data communication between DOTS agents to loop. Signal and data
channel implementations should be prepared to detect and terminate channel implementations should be prepared to detect and terminate
such loops to prevent service disruption. such loops to prevent service disruption.
2.2. Signal Channel Requirements 2.2. Signal Channel Requirements
SIG-001 Use of Common Transport Protocols: DOTS MUST operate over SIG-001 Use of Common Transport Protocols: DOTS MUST operate over
common widely deployed and standardized transport protocols. common, widely deployed and standardized transport protocols.
While connectionless transport such as the User Datagram Protocol While connectionless transport such as the User Datagram Protocol
(UDP) [RFC0768] SHOULD be used for the signal channel, the (UDP) [RFC768] SHOULD be used for the signal channel, the
Transmission Control Protocol (TCP) [RFC0793] MAY be used if Transmission Control Protocol (TCP) [RFC793] MAY be used if
necessary due to network policy or middlebox capabilities or necessary due to network policy or middlebox capabilities or
configurations. configurations.
SIG-002 Sub-MTU Message Size: To avoid message fragmentation and the SIG-002 Sub-MTU Message Size: To avoid message fragmentation and the
consequently decreased probability of message delivery over a consequently decreased probability of message delivery over a
congested link, signaling protocol message size MUST be kept under congested link, signaling protocol message size MUST be kept under
signaling Path Maximum Transmission Unit (PMTU), including the the signaling Path Maximum Transmission Unit (PMTU), including the
byte overhead of any encapsulation, transport headers, and byte overhead of any encapsulation, transport headers, and
transport- or message-level security. If the total message size transport- or message-level security. If the total message size
exceeds the path MTU, the DOTS agent MUST split the message into exceeds the PMTU, the DOTS agent MUST split the message into
separate messages; for example, the list of mitigation scope types separate messages; for example, the list of mitigation scope types
could be split into multiple lists and each list conveyed in a new could be split into multiple lists and each list conveyed in a new
message. message.
DOTS agents can attempt to learn PMTU using the procedures DOTS agents can attempt to learn PMTU using the procedures
discussed in [I-D.ietf-intarea-frag-fragile]. If the PMTU cannot discussed in [IP-FRAG-FRAGILE]. If the PMTU cannot be discovered,
be discovered, DOTS agents MUST assume a PMTU of 1280 bytes, as DOTS agents MUST assume a PMTU of 1280 bytes, as IPv6 requires
IPv6 requires that every link in the Internet have an MTU of 1280 that every link in the Internet have an MTU of 1280 octets or
octets or greater as specified in [RFC8200]. If IPv4 support on greater as specified in [RFC8200]. If IPv4 support on legacy or
legacy or otherwise unusual networks is a consideration and the otherwise unusual networks is a consideration and the PMTU is
PMTU is unknown, DOTS implementations MAY assume on a PMTU of 576 unknown, DOTS implementations MAY assume a PMTU of 576 bytes for
bytes for IPv4 datagrams, as every IPv4 host must be capable of IPv4 datagrams, as every IPv4 host must be capable of receiving a
receiving a packet whose length is equal to 576 bytes as discussed packet whose length is equal to 576 bytes as discussed in [RFC791]
in [RFC0791] and [RFC1122]. and [RFC1122].
SIG-003 Bidirectionality: To support peer health detection, to SIG-003 Bidirectionality: To support peer health detection, to
maintain an active signal channel, and to increase the probability maintain an active signal channel, and to increase the probability
of signal delivery during an attack, the signal channel MUST be of signal delivery during an attack, the signal channel MUST be
bidirectional, with client and server transmitting signals to each bidirectional, with client and server transmitting signals to each
other at regular intervals, regardless of any client request for other at regular intervals regardless of any client request for
mitigation. The bidirectional signal channel MUST support mitigation. The bidirectional signal channel MUST support
unidirectional messaging to enable notifications between DOTS unidirectional messaging to enable notifications between DOTS
agents. agents.
SIG-004 Channel Health Monitoring: DOTS agents MUST support exchange SIG-004 Channel Health Monitoring: DOTS agents MUST support exchange
of heartbeat messages over the signal channel to monitor channel of heartbeat messages over the signal channel to monitor channel
health. These keepalives serve the purpose to maintain any on- health. These keep-alives serve to maintain any on-path NAT or
path NAT or Firewall bindings to avoid cryptographic handshake for Firewall bindings to avoid cryptographic handshake for new
new mitigation requests. The heartbeat interval during active mitigation requests. The heartbeat interval during active
mitigation could be negotiable based on NAT/Firewall mitigation could be negotiable based on NAT/Firewall
characteristics. Absent information about the NAT/Firewall characteristics. Absent information about the NAT/Firewall
characteristics, DOTS agent needs to ensure its on-path NAT or characteristics, DOTS agents need to ensure its on-path NAT or
Firewall bindings do not expire, by using the keep-alive frequency Firewall bindings do not expire, by using the keep-alive frequency
discussed in Section 3.5 of [RFC8085]. discussed in Section 3.5 of [RFC8085].
To support scenarios in which loss of heartbeat is used to trigger To support scenarios in which loss of heartbeat is used to trigger
mitigation, and to keep the channel active, DOTS servers MUST mitigation, and to keep the channel active, DOTS servers MUST
solicit heartbeat exchanges after successful mutual solicit heartbeat exchanges after successful mutual
authentication. When DOTS agents are exchanging heartbeats and no authentication. When DOTS agents are exchanging heartbeats and no
mitigation request is active, either agent MAY request changes to mitigation request is active, either agent MAY request changes to
the heartbeat rate. For example, a DOTS server might want to the heartbeat rate. For example, a DOTS server might want to
reduce heartbeat frequency or cease heartbeat exchanges when an reduce heartbeat frequency or cease heartbeat exchanges when an
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considered active until a DOTS agent explicitly ends the session. considered active until a DOTS agent explicitly ends the session.
When no attack traffic is present, the signal channel MUST be When no attack traffic is present, the signal channel MUST be
considered active until either DOTS agent fails to receive considered active until either DOTS agent fails to receive
heartbeats from the other peer after a mutually agreed upon heartbeats from the other peer after a mutually agreed upon
retransmission procedure has been exhausted. Peer DOTS agents retransmission procedure has been exhausted. Peer DOTS agents
MUST regularly send heartbeats to each other while a mitigation MUST regularly send heartbeats to each other while a mitigation
request is active. Because heartbeat loss is much more likely request is active. Because heartbeat loss is much more likely
during volumetric attack, DOTS agents SHOULD avoid signal channel during volumetric attack, DOTS agents SHOULD avoid signal channel
termination when mitigation is active and heartbeats are not termination when mitigation is active and heartbeats are not
received by either DOTS agent for an extended period. The received by either DOTS agent for an extended period. The
exception circumstances to terminate the signal channel session exception circumstances to terminating the signal channel session
during active mitigation are discussed below: during active mitigation are discussed below:
* To handle possible DOTS server restart or crash, the DOTS * To handle a possible DOTS server restart or crash, the DOTS
clients MAY attempt to establish a new signal channel session, clients MAY attempt to establish a new signal channel session
but MUST continue to send heartbeats on the current session so but MUST continue to send heartbeats on the current session so
that the DOTS server knows the session is still alive. If the that the DOTS server knows the session is still alive. If the
new session is successfully established, the DOTS client can new session is successfully established, the DOTS client can
terminate the current session. terminate the current session.
* DOTS servers are assumed to have the ability to monitor the * DOTS servers are assumed to have the ability to monitor the
attack, using feedback from the mitigator and other available attack, using feedback from the mitigator and other available
sources, and MAY use the absence of attack traffic and lack of sources, and MAY use the absence of attack traffic and lack of
client heartbeats as an indication the signal channel is client heartbeats as an indication the signal channel is
defunct. defunct.
skipping to change at page 10, line 31 skipping to change at page 10, line 29
target in the DOTS client's domain. target in the DOTS client's domain.
SIG-006 Mitigation Requests and Status: Authorized DOTS clients MUST SIG-006 Mitigation Requests and Status: Authorized DOTS clients MUST
be able to request scoped mitigation from DOTS servers. DOTS be able to request scoped mitigation from DOTS servers. DOTS
servers MUST send status to the DOTS clients about mitigation servers MUST send status to the DOTS clients about mitigation
requests. If a DOTS server rejects an authorized request for requests. If a DOTS server rejects an authorized request for
mitigation, the DOTS server MUST include a reason for the mitigation, the DOTS server MUST include a reason for the
rejection in the status message sent to the client. rejection in the status message sent to the client.
DOTS servers MUST regularly send mitigation status updates to DOTS servers MUST regularly send mitigation status updates to
authorized DOTS clients which have requested and been granted authorized DOTS clients that have requested and been granted
mitigation. If unreliable transport is used for the signal mitigation. If unreliable transport is used for the signal
channel protocol, due to the higher likelihood of packet loss channel protocol, due to the higher likelihood of packet loss
during a DDoS attack, DOTS servers needs to send mitigation status during a DDoS attack, DOTS servers need to send the mitigation
multiple times at regular intervals following the the data status multiple times at regular intervals following the data
transmission guidelines discussed in Section 3.1.3 of [RFC8085]. transmission guidelines discussed in Section 3.1.3 of [RFC8085].
When DOTS client-requested mitigation is active, DOTS server When DOTS client-requested mitigation is active, DOTS server
status messages MUST include the following mitigation metrics: status messages MUST include the following mitigation metrics:
* Total number of packets blocked by the mitigation * Total number of packets blocked by the mitigation
* Current number of packets per second blocked * Current number of packets per second blocked
* Total number of bytes blocked * Total number of bytes blocked
* Current number of bytes per second blocked * Current number of bytes per second blocked
DOTS clients MAY take these metrics into account when determining DOTS clients MAY take these metrics into account when determining
whether to ask the DOTS server to cease mitigation. whether to ask the DOTS server to cease mitigation.
A DOTS client MAY withdraw a mitigation request at any time, A DOTS client MAY withdraw a mitigation request at any time
regardless of whether mitigation is currently active. The DOTS regardless of whether mitigation is currently active. The DOTS
server MUST immediately acknowledge a DOTS client's request to server MUST immediately acknowledge a DOTS client's request to
stop mitigation. stop mitigation.
To protect against route or DNS flapping caused by a client To protect against route or DNS flapping caused by a client
rapidly toggling mitigation, and to dampen the effect of rapidly toggling mitigation, and to dampen the effect of
oscillating attacks, DOTS servers MAY allow mitigation to continue oscillating attacks, DOTS servers MAY allow mitigation to continue
for a limited period after acknowledging a DOTS client's for a limited period after acknowledging a DOTS client's
withdrawal of a mitigation request. During this period, DOTS withdrawal of a mitigation request. During this period, DOTS
server status messages SHOULD indicate that mitigation is active server status messages SHOULD indicate that mitigation is active
but terminating. DOTS clients MAY reverse the mitigation but terminating. DOTS clients MAY reverse the mitigation
termination during this active-but-terminating period with a new termination during this active-but-terminating period with a new
mitigation request for the same scope. The DOTS server MUST treat mitigation request for the same scope. The DOTS server MUST treat
this request as a mitigation lifetime extension (see SIG-007 this request as a mitigation lifetime extension (see SIG-007).
below).
The initial active-but-terminating period is implementation- and The initial active-but-terminating period is both implementation-
deployment- specific, but SHOULD be sufficiently long to absorb and deployment-specific, but SHOULD be sufficiently long enough to
latency incurred by route propagation. If a DOTS client refreshes absorb latency incurred by route propagation. If a DOTS client
the mitigation before the active-but-terminating period elapses, refreshes the mitigation before the active-but-terminating period
the DOTS server MAY increase the active-but-terminating period up elapses, the DOTS server MAY increase the active-but-terminating
to a maximum of 300 seconds (5 minutes). After the active-but- period up to a maximum of 300 seconds (5 minutes). After the
terminating period elapses, the DOTS server MUST treat the active-but-terminating period elapses, the DOTS server MUST treat
mitigation as terminated, as the DOTS client is no longer the mitigation as terminated, as the DOTS client is no longer
responsible for the mitigation. responsible for the mitigation.
SIG-007 Mitigation Lifetime: DOTS servers MUST support mitigations SIG-007 Mitigation Lifetime: DOTS servers MUST support mitigations
for a negotiated time interval, and MUST terminate a mitigation for a negotiated time interval and MUST terminate a mitigation
when the lifetime elapses. DOTS servers also MUST support renewal when the lifetime elapses. DOTS servers also MUST support renewal
of mitigation lifetimes in mitigation requests from DOTS clients, of mitigation lifetimes in mitigation requests from DOTS clients,
allowing clients to extend mitigation as necessary for the allowing clients to extend mitigation as necessary for the
duration of an attack. duration of an attack.
DOTS servers MUST treat a mitigation terminated due to lifetime DOTS servers MUST treat a mitigation terminated due to lifetime
expiration exactly as if the DOTS client originating the expiration exactly as if the DOTS client originating the
mitigation had asked to end the mitigation, including the active- mitigation had asked to end the mitigation, including the active-
but-terminating period, as described above in SIG-005. but-terminating period, as described above in SIG-005.
DOTS clients MUST include a mitigation lifetime in all mitigation DOTS clients MUST include a mitigation lifetime in all mitigation
requests. requests.
DOTS servers SHOULD support indefinite mitigation lifetimes, DOTS servers SHOULD support indefinite mitigation lifetimes,
enabling architectures in which the mitigator is always in the enabling architectures in which the mitigator is always in the
traffic path to the resources for which the DOTS client is traffic path to the resources for which the DOTS client is
requesting protection. DOTS clients MUST be prepared to not be requesting protection. DOTS clients MUST be prepared to not be
granted mitigations with indefinite lifetimes. DOTS servers MAY granted mitigations with indefinite lifetimes. DOTS servers MAY
refuse mitigations with indefinite lifetimes, for policy reasons. refuse mitigations with indefinite lifetimes for policy reasons.
The reasons themselves are out of scope for this document. If the
The reasons themselves are out of scope. If the DOTS server does DOTS server does not grant a mitigation request with an indefinite
not grant a mitigation request with an indefinite mitigation mitigation lifetime, it MUST set the lifetime to a value that is
lifetime, it MUST set the lifetime to a value that is configured configured locally. That value MUST be returned in a reply to the
locally. That value MUST be returned in a reply to the requesting requesting DOTS client.
DOTS client.
SIG-008 Mitigation Scope: DOTS clients MUST indicate desired SIG-008 Mitigation Scope: DOTS clients MUST indicate desired
mitigation scope. The scope type will vary depending on the mitigation scope. The scope type will vary depending on the
resources requiring mitigation. All DOTS agent implementations resources requiring mitigation. All DOTS agent implementations
MUST support the following required scope types: MUST support the following required scope types:
* IPv4 prefixes [RFC4632] * IPv4 prefixes [RFC4632]
* IPv6 prefixes [RFC4291][RFC5952] * IPv6 prefixes [RFC4291] [RFC5952]
* Domain names [RFC1035] * Domain names [RFC1035]
The following mitigation scope types are OPTIONAL: The following mitigation scope type is OPTIONAL:
* Uniform Resource Identifiers [RFC3986] * Uniform Resource Identifiers [RFC3986]
DOTS servers MUST be able to resolve domain names and (when DOTS servers MUST be able to resolve domain names and (when
supported) URIs. How name resolution is managed on the DOTS supported) URIs. How name resolution is managed on the DOTS
server is implementation-specific. server is implementation-specific.
DOTS agents MUST support mitigation scope aliases, allowing DOTS DOTS agents MUST support mitigation scope aliases, allowing DOTS
clients and servers to refer to collections of protected resources clients and servers to refer to collections of protected resources
by an opaque identifier created through the data channel, direct by an opaque identifier created through the data channel, direct
configuration, or other means. Domain name and URI mitigation configuration, or other means. Domain name and URI mitigation
scopes may be thought of as a form of scope alias, in which the scopes may be thought of as a form of scope alias in which the
addresses to which the domain name or URI resolve represent the addresses to which the domain name or URI resolve represent the
full scope of the mitigation. full scope of the mitigation.
If there is additional information available narrowing the scope If there is additional information available narrowing the scope
of any requested attack response, such as targeted port range, of any requested attack response, such as targeted port range,
protocol, or service, DOTS clients SHOULD include that information protocol, or service, DOTS clients SHOULD include that information
in client mitigation requests. DOTS clients MAY also include in client mitigation requests. DOTS clients MAY also include
additional attack details. DOTS servers MAY ignore such additional attack details. DOTS servers MAY ignore such
supplemental information when enabling countermeasures on the supplemental information when enabling countermeasures on the
mitigator. mitigator.
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on behalf of a DOTS client. on behalf of a DOTS client.
SIG-010 Conflict Detection and Notification: Multiple DOTS clients SIG-010 Conflict Detection and Notification: Multiple DOTS clients
controlled by a single administrative entity may send conflicting controlled by a single administrative entity may send conflicting
mitigation requests as a result of misconfiguration, operator mitigation requests as a result of misconfiguration, operator
error, or compromised DOTS clients. DOTS servers in the same error, or compromised DOTS clients. DOTS servers in the same
administrative domain attempting to honor conflicting requests may administrative domain attempting to honor conflicting requests may
flap network route or DNS information, degrading the networks flap network route or DNS information, degrading the networks
attempting to participate in attack response with the DOTS attempting to participate in attack response with the DOTS
clients. DOTS servers in a single administrative domain SHALL clients. DOTS servers in a single administrative domain SHALL
detect such conflicting requests, and SHALL notify the DOTS detect such conflicting requests and SHALL notify the DOTS clients
clients in conflict. The notification MUST indicate the nature in conflict. The notification MUST indicate the nature and scope
and scope of the conflict, for example, the overlapping prefix of the conflict, for example, the overlapping prefix range in a
range in a conflicting mitigation request. conflicting mitigation request.
SIG-011 Network Address Translator Traversal: DOTS clients may be SIG-011 Network Address Translator Traversal: DOTS clients may be
deployed behind a Network Address Translator (NAT), and need to deployed behind a Network Address Translator (NAT) and need to
communicate with DOTS servers through the NAT. DOTS protocols communicate with DOTS servers through the NAT. DOTS protocols
MUST therefore be capable of traversing NATs. MUST therefore be capable of traversing NATs.
If UDP is used as the transport for the DOTS signal channel, all If UDP is used as the transport for the DOTS signal channel, all
considerations in "Middlebox Traversal Guidelines" in [RFC8085] considerations in "Middlebox Traversal Guidelines" in [RFC8085]
apply to DOTS. Regardless of transport, DOTS protocols MUST apply to DOTS. Regardless of transport, DOTS protocols MUST
follow established best common practices established in BCP 127 follow established best common practices established in BCP 127
for NAT traversal [RFC4787][RFC6888][RFC7857]. for NAT traversal [RFC4787] [RFC6888] [RFC7857].
2.3. Data Channel Requirements 2.3. Data Channel Requirements
The data channel is intended to be used for bulk data exchanges The data channel is intended to be used for bulk data exchanges
between DOTS agents. Unlike the signal channel, the data channel is between DOTS agents. Unlike the signal channel, the data channel is
not expected to be constructed to deal with attack conditions. As not expected to be constructed to deal with attack conditions. As
the primary function of the data channel is data exchange, a reliable the primary function of the data channel is data exchange, a reliable
transport is required in order for DOTS agents to detect data transport is required in order for DOTS agents to detect data
delivery success or failure. delivery success or failure.
The data channel provides a protocol for DOTS configuration, The data channel provides a protocol for DOTS configuration and
management. For example, a DOTS client may submit to a DOTS server a management. For example, a DOTS client may submit to a DOTS server a
collection of prefixes it wants to refer to by alias when requesting collection of prefixes it wants to refer to by alias when requesting
mitigation, to which the server would respond with a success status mitigation, to which the server would respond with a success status
and the new prefix group alias, or an error status and message in the and the new prefix group alias, or an error status and message in the
event the DOTS client's data channel request failed. event the DOTS client's data channel request failed.
DATA-001 Reliable transport: Messages sent over the data channel DATA-001 Reliable transport: Messages sent over the data channel
MUST be delivered reliably, in order sent. MUST be delivered reliably in the order sent.
DATA-003 Resource Configuration: To help meet the general and signal DATA-003 Resource Configuration: To help meet the general and signal
channel requirements in Section 2.1 and Section 2.2, DOTS server channel requirements in Sections 2.1 and 2.2, DOTS server
implementations MUST provide an interface to configure resource implementations MUST provide an interface to configure resource
identifiers, as described in SIG-008. DOTS server implementations identifiers, as described in SIG-008. DOTS server implementations
MAY expose additional configurability. Additional configurability MAY expose additional configurability. Additional configurability
is implementation-specific. is implementation-specific.
DATA-004 Policy management: DOTS servers MUST provide methods for DATA-004 Policy Management: DOTS servers MUST provide methods for
DOTS clients to manage drop- and accept-lists of traffic destined DOTS clients to manage drop- and accept-lists of traffic destined
for resources belonging to a client. for resources belonging to a client.
For example, a DOTS client should be able to create a drop- or For example, a DOTS client should be able to create a drop- or
accept-list entry, retrieve a list of current entries from either accept-list entry, retrieve a list of current entries from either
list, update the content of either list, and delete entries as list, update the content of either list, and delete entries as
necessary. necessary.
How a DOTS server authorizes DOTS client management of drop- and How a DOTS server authorizes DOTS client management of drop- and
accept-list entries is implementation-specific. accept-list entries is implementation-specific.
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2.4. Security Requirements 2.4. Security Requirements
DOTS must operate within a particularly strict security context, as DOTS must operate within a particularly strict security context, as
an insufficiently protected signal or data channel may be subject to an insufficiently protected signal or data channel may be subject to
abuse, enabling or supplementing the very attacks DOTS purports to abuse, enabling or supplementing the very attacks DOTS purports to
mitigate. mitigate.
SEC-001 Peer Mutual Authentication: DOTS agents MUST authenticate SEC-001 Peer Mutual Authentication: DOTS agents MUST authenticate
each other before a DOTS signal or data channel is considered each other before a DOTS signal or data channel is considered
valid. The method of authentication is not specified in this valid. The method of authentication is not specified in this
document, but should follow current IETF best practices [RFC7525] document but should follow current IETF best practices [RFC7525]
with respect to any cryptographic mechanisms to authenticate the with respect to any cryptographic mechanisms to authenticate the
remote peer. remote peer.
SEC-002 Message Confidentiality, Integrity and Authenticity: DOTS SEC-002 Message Confidentiality, Integrity, and Authenticity: DOTS
protocols MUST take steps to protect the confidentiality, protocols MUST take steps to protect the confidentiality,
integrity and authenticity of messages sent between client and integrity, and authenticity of messages sent between client and
server. While specific transport- and message-level security server. While specific transport- and message-level security
options are not specified, the protocols MUST follow current IETF options are not specified, the protocols MUST follow current IETF
best practices [RFC7525] for encryption and message best practices [RFC7525] for encryption and message
authentication. Client-domain DOTS gateways are more trusted than authentication. Client-domain DOTS gateways are more trusted than
DOTS clients, while server-domain DOTS gateways and DOTS servers DOTS clients, while server-domain DOTS gateways and DOTS servers
share the same level of trust. A security mechanism at the share the same level of trust. A security mechanism at the
transport layer TLS/DTLS is thus adequate to provide security transport layer (TLS or DTLS) is thus adequate to provide security
between peer DOTS agents. between peer DOTS agents.
In order for DOTS protocols to remain secure despite advancements In order for DOTS protocols to remain secure despite advancements
in cryptanalysis and traffic analysis, DOTS agents MUST support in cryptanalysis and traffic analysis, DOTS agents MUST support
secure negotiation of the terms and mechanisms of protocol secure negotiation of the terms and mechanisms of protocol
security, subject to the interoperability and signal message size security, subject to the interoperability and signal message size
requirements in Section 2.2. requirements in Section 2.2.
While the interfaces between downstream DOTS server and upstream While the interfaces between downstream DOTS server and upstream
DOTS client within a DOTS gateway are implementation-specific, DOTS client within a DOTS gateway are implementation-specific,
those interfaces nevertheless MUST provide security equivalent to those interfaces nevertheless MUST provide security equivalent to
that of the signal channels bridged by gateways in the signaling that of the signal channels bridged by gateways in the signaling
path. For example, when a DOTS gateway consisting of a DOTS path. For example, when a DOTS gateway consisting of a DOTS
server and DOTS client is running on the same logical device, the server and DOTS client is running on the same logical device, the
two DOTS agents could be implemented within the same process two DOTS agents could be implemented within the same process
security boundary. security boundary.
SEC-003 Data privacy and integrity: Transmissions over the DOTS SEC-003 Data Privacy and Integrity: Transmissions over the DOTS
protocols are likely to contain operationally or privacy-sensitive protocols are likely to contain operationally or privacy-sensitive
information or instructions from the remote DOTS agent. Theft, information or instructions from the remote DOTS agent. Theft,
modification, or replay of message transmissions could lead to modification, or replay of message transmissions could lead to
information leaks or malicious transactions on behalf of the information leaks or malicious transactions on behalf of the
sending agent (see Section 4 below). Consequently data sent over sending agent (see Section 4). Consequently, data sent over the
the DOTS protocols MUST be encrypted using secure transports TLS/ DOTS protocols MUST be encrypted using secure transports (TLS or
DTLS. DOTS servers MUST enable means to prevent leaking DTLS). DOTS servers MUST enable means to prevent leaking
operationally or privacy-sensitive data. Although administrative operationally or privacy-sensitive data. Although administrative
entities participating in DOTS may detail what data may be entities participating in DOTS may detail what data may be
revealed to third-party DOTS agents, such considerations are not revealed to third-party DOTS agents, such considerations are not
in scope for this document. in scope for this document.
SEC-004 Message Replay Protection: To prevent a passive attacker SEC-004 Message Replay Protection: To prevent a passive attacker
from capturing and replaying old messages, and thereby potentially from capturing and replaying old messages, and thereby potentially
disrupting or influencing the network policy of the receiving DOTS disrupting or influencing the network policy of the receiving DOTS
agent's domain, DOTS protocols MUST provide a method for replay agent's domain, DOTS protocols MUST provide a method for replay
detection and prevention. detection and prevention.
Within the signal channel, messages MUST be uniquely identified Within the signal channel, messages MUST be uniquely identified
such that replayed or duplicated messages can be detected and such that replayed or duplicated messages can be detected and
discarded. Unique mitigation requests MUST be processed at most discarded. Unique mitigation requests MUST be processed at most
once. once.
SEC-005 Authorization: DOTS servers MUST authorize all messages from SEC-005 Authorization: DOTS servers MUST authorize all messages from
DOTS clients which pertain to mitigation, configuration, DOTS clients that pertain to mitigation, configuration, filtering,
filtering, or status. or status.
DOTS servers MUST reject mitigation requests with scopes which the DOTS servers MUST reject mitigation requests with scopes that the
DOTS client is not authorized to manage. DOTS client is not authorized to manage.
Likewise, DOTS servers MUST refuse to allow creation, modification Likewise, DOTS servers MUST refuse to allow creation,
or deletion of scope aliases and drop-/accept-lists when the DOTS modification, or deletion of scope aliases and drop- or accept-
client is unauthorized. lists when the DOTS client is unauthorized.
The modes of authorization are implementation-specific. The modes of authorization are implementation-specific.
2.5. Data Model Requirements 2.5. Data Model Requirements
A well-structured DOTS data model is critical to the development of A well-structured DOTS data model is critical to the development of
successful DOTS protocols. successful DOTS protocols.
DM-001 Structure: The data model structure for the DOTS protocol MAY DM-001 Structure: The data-model structure for the DOTS protocol MAY
be described by a single module, or be divided into related be described by a single module or be divided into related
collections of hierarchical modules and sub-modules. If the data collections of hierarchical modules and submodules. If the data
model structure is split across modules, those distinct modules model structure is split across modules, those distinct modules
MUST allow references to describe the overall data model's MUST allow references to describe the overall data model's
structural dependencies. structural dependencies.
DM-002 Versioning: To ensure interoperability between DOTS protocol DM-002 Versioning: To ensure interoperability between DOTS protocol
implementations, data models MUST be versioned. How the protocols implementations, data models MUST be versioned. How the protocols
represent data model versions is not defined in this document. represent data-model versions is not defined in this document.
DM-003 Mitigation Status Representation: The data model MUST provide DM-003 Mitigation Status Representation: The data model MUST provide
the ability to represent a request for mitigation and the the ability to represent a request for mitigation and the
withdrawal of such a request. The data model MUST also support a withdrawal of such a request. The data model MUST also support a
representation of currently requested mitigation status, including representation of currently-requested mitigation status, including
failures and their causes. failures and their causes.
DM-004 Mitigation Scope Representation: The data model MUST support DM-004 Mitigation Scope Representation: The data model MUST support
representation of a requested mitigation's scope. As mitigation representation of a requested mitigation's scope. As mitigation
scope may be represented in several different ways, per SIG-008 scope may be represented in several different ways, per SIG-008,
above, the data model MUST include extensible representation of the data model MUST include extensible representation of
mitigation scope. mitigation scope.
DM-005 Mitigation Lifetime Representation: The data model MUST DM-005 Mitigation Lifetime Representation: The data model MUST
support representation of a mitigation request's lifetime, support representation of a mitigation request's lifetime,
including mitigations with no specified end time. including mitigations with no specified end time.
DM-006 Mitigation Efficacy Representation: The data model MUST DM-006 Mitigation Efficacy Representation: The data model MUST
support representation of a DOTS client's understanding of the support representation of a DOTS client's understanding of the
efficacy of a mitigation enabled through a mitigation request. efficacy of a mitigation enabled through a mitigation request.
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consecutive missed heartbeat messages, retransmission count, or consecutive missed heartbeat messages, retransmission count, or
request timeouts. request timeouts.
DM-008 Heartbeat Interval Representation: The data model MUST be DM-008 Heartbeat Interval Representation: The data model MUST be
able to represent the DOTS agent's preferred heartbeat interval, able to represent the DOTS agent's preferred heartbeat interval,
which the client may include when establishing the signal channel, which the client may include when establishing the signal channel,
as described in SIG-003. as described in SIG-003.
DM-009 Relationship to Transport: The DOTS data model MUST NOT make DM-009 Relationship to Transport: The DOTS data model MUST NOT make
any assumptions about specific characteristics of any given any assumptions about specific characteristics of any given
transport into the data model, but instead, represent the fields transport into the data model, but instead represent the fields in
in the model explicitly. the model explicitly.
3. Congestion Control Considerations 3. Congestion Control Considerations
3.1. Signal Channel 3.1. Signal Channel
As part of a protocol expected to operate over links affected by DDoS As part of a protocol expected to operate over links affected by DDoS
attack traffic, the DOTS signal channel MUST NOT contribute attack traffic, the DOTS signal channel MUST NOT contribute
significantly to link congestion. To meet the signal channel significantly to link congestion. To meet the signal channel
requirements above, DOTS signal channel implementations SHOULD requirements above, DOTS signal channel implementations SHOULD
support connectionless transports. However, some connectionless support connectionless transports. However, some connectionless
transports when deployed naively can be a source of network transports, when deployed naively, can be a source of network
congestion, as discussed in [RFC8085]. Signal channel congestion, as discussed in [RFC8085]. Signal channel
implementations using such connectionless transports, such as UDP, implementations using such connectionless transports, such as UDP,
therefore MUST include a congestion control mechanism. therefore MUST include a congestion control mechanism.
Signal channel implementations using a IETF standard congestion- Signal channel implementations using an IETF standard congestion-
controlled transport protocol (like TCP) may rely on built-in controlled transport protocol (like TCP) may rely on built-in
transport congestion control support. transport congestion control support.
3.2. Data Channel 3.2. Data Channel
As specified in DATA-001, the data channel requires reliable, in- As specified in DATA-001, the data channel requires reliable, in-
order message delivery. Data channel implementations using a IETF order message delivery. Data channel implementations using an IETF
standard congestion-controlled transport protocol may rely on the standard congestion-controlled transport protocol may rely on the
transport implementation's built-in congestion control mechanisms. transport implementation's built-in congestion control mechanisms.
4. Security Considerations 4. Security Considerations
This document informs future protocols under development, and so does This document informs future protocols under development and so does
not have security considerations of its own. However, operators not have security considerations of its own. However, operators
should be aware of potential risks involved in deploying DOTS. DOTS should be aware of potential risks involved in deploying DOTS. DOTS
agent impersonation and signal blocking are discussed here. agent impersonation and signal blocking are discussed here.
Additional DOTS security considerations may be found in Additional DOTS security considerations may be found in [DOTS-ARCH]
[I-D.ietf-dots-architecture] and DOTS protocol documents. and DOTS protocol documents.
Impersonation of either a DOTS server or a DOTS client could have Impersonation of either a DOTS server or a DOTS client could have
catastrophic impact on operations in either domain. If an attacker catastrophic impact on operations in either domain. If an attacker
has the ability to impersonate a DOTS client, that attacker can has the ability to impersonate a DOTS client, that attacker can
affect policy on the network path to the DOTS client's domain, up to affect policy on the network path to the DOTS client's domain up to
and including instantiation of drop-lists blocking all inbound and including instantiation of drop-lists blocking all inbound
traffic to networks for which the DOTS client is authorized to traffic to networks for which the DOTS client is authorized to
request mitigation. request mitigation.
Similarly, an impersonated DOTS server may be able to act as a sort Similarly, an impersonated DOTS server may be able to act as a sort
of malicious DOTS gateway, intercepting requests from the downstream of malicious DOTS gateway, intercepting requests from the downstream
DOTS client, and modifying them before transmission to the DOTS DOTS client and modifying them before transmission to the DOTS server
server to inflict the desired impact on traffic to or from the DOTS to inflict the desired impact on traffic to or from the DOTS client's
client's domain. Among other things, this malicious DOTS gateway domain. Among other things, this malicious DOTS gateway might
might receive and discard mitigation requests from the DOTS client, receive and discard mitigation requests from the DOTS client,
ensuring no requested mitigation is ever applied. ensuring no requested mitigation is ever applied.
To detect misuse, as detailed in Section 2.4, DOTS implementations To detect misuse, as detailed in Section 2.4, DOTS implementations
require mutual authentication of DOTS agents in order to make agent require mutual authentication of DOTS agents in order to make agent
impersonation more difficult. However, impersonation may still be impersonation more difficult. However, impersonation may still be
possible as a result of credential theft, implementation flaws, or possible as a result of credential theft, implementation flaws, or
compromise of DOTS agents. DOTS agents being compromised.
To detect compromised DOTS agents, DOTS operators should carefully To detect compromised DOTS agents, DOTS operators should carefully
monitor and audit DOTS agents to detect misbehavior and to deter monitor and audit DOTS agents to detect misbehavior and deter misuse
misuse, while employing current secure network communications best while employing best current practices to secure network
practices to reduce attack surface. communications to reduce attack surface.
Blocking communication between DOTS agents has the potential to Blocking communication between DOTS agents has the potential to
disrupt the core function of DOTS, which is to request mitigation of disrupt the core function of DOTS, which is to request mitigation of
active or expected DDoS attacks. The DOTS signal channel is expected active or expected DDoS attacks. The DOTS signal channel is expected
to operate over congested inbound links, and, as described in to operate over congested inbound links, and, as described in
Section 2.2, the signal channel protocol must be designed for minimal Section 2.2, the signal channel protocol must be designed for minimal
data transfer to reduce the incidence of signal loss. data transfer to reduce the incidence of signal loss.
5. IANA Considerations 5. IANA Considerations
This document does not require any IANA action. This document has no IANA actions.
6. Contributors
Mohamed Boucadair
Orange
mohamed.boucadair@orange.com
Flemming Andreasen
Cisco Systems, Inc.
fandreas@cisco.com
Dave Dolson
Sandvine
ddolson@sandvine.com
7. Acknowledgments
Thanks to Roman Danyliw, Matt Richardson, Joe Touch, Scott Bradner,
Robert Sparks, Brian Weis, Benjamin Kaduk, Eric Rescorla, Alvaro
Retana, Suresh Krishnan, Ben Campbell, Mirja Kuehlewind and Jon
Shallow for careful reading and feedback.
8. References 6. References
8.1. Normative References 6.1. Normative References
[RFC0768] Postel, J., "User Datagram Protocol", STD 6, RFC 768, [RFC768] Postel, J., "User Datagram Protocol", STD 6, RFC 768,
DOI 10.17487/RFC0768, August 1980, DOI 10.17487/RFC0768, August 1980,
<https://www.rfc-editor.org/info/rfc768>. <https://www.rfc-editor.org/info/rfc768>.
[RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791, [RFC791] Postel, J., "Internet Protocol", STD 5, RFC 791,
DOI 10.17487/RFC0791, September 1981, DOI 10.17487/RFC0791, September 1981,
<https://www.rfc-editor.org/info/rfc791>. <https://www.rfc-editor.org/info/rfc791>.
[RFC0793] Postel, J., "Transmission Control Protocol", STD 7, [RFC793] Postel, J., "Transmission Control Protocol", STD 7,
RFC 793, DOI 10.17487/RFC0793, September 1981, RFC 793, DOI 10.17487/RFC0793, September 1981,
<https://www.rfc-editor.org/info/rfc793>. <https://www.rfc-editor.org/info/rfc793>.
[RFC1035] Mockapetris, P., "Domain names - implementation and [RFC1035] Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, DOI 10.17487/RFC1035, specification", STD 13, RFC 1035, DOI 10.17487/RFC1035,
November 1987, <https://www.rfc-editor.org/info/rfc1035>. November 1987, <https://www.rfc-editor.org/info/rfc1035>.
[RFC1122] Braden, R., Ed., "Requirements for Internet Hosts - [RFC1122] Braden, R., Ed., "Requirements for Internet Hosts -
Communication Layers", STD 3, RFC 1122, Communication Layers", STD 3, RFC 1122,
DOI 10.17487/RFC1122, October 1989, DOI 10.17487/RFC1122, October 1989,
skipping to change at page 20, line 44 skipping to change at page 20, line 18
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>. May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6 [RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", STD 86, RFC 8200, (IPv6) Specification", STD 86, RFC 8200,
DOI 10.17487/RFC8200, July 2017, DOI 10.17487/RFC8200, July 2017,
<https://www.rfc-editor.org/info/rfc8200>. <https://www.rfc-editor.org/info/rfc8200>.
8.2. Informative References 6.2. Informative References
[I-D.ietf-dots-architecture] [DOTS-ARCH]
Mortensen, A., Andreasen, F., K, R., Teague, N., Compton, Mortensen, A., Ed., Reddy, T., Ed., Andreasen, F., Teague,
R., and c. christopher_gray3@cable.comcast.com, N., and R. Compton, "Distributed-Denial-of-Service Open
"Distributed-Denial-of-Service Open Threat Signaling Threat Signaling (DOTS) Architecture", Work in Progress,
(DOTS) Architecture", draft-ietf-dots-architecture-12 draft-ietf-dots-architecture-13, April 2019.
(work in progress), February 2019.
[I-D.ietf-dots-use-cases] [DOTS-USE]
Dobbins, R., Migault, D., Fouant, S., Moskowitz, R., Dobbins, R., Migault, D., Fouant, S., Moskowitz, R.,
Teague, N., Xia, L., and K. Nishizuka, "Use cases for DDoS Teague, N., Xia, L., and K. Nishizuka, "Use cases for DDoS
Open Threat Signaling", draft-ietf-dots-use-cases-17 (work Open Threat Signaling", Work in Progress, draft-ietf-dots-
in progress), January 2019. use-cases-17, January 2019.
[I-D.ietf-intarea-frag-fragile] [IP-FRAG-FRAGILE]
Bonica, R., Baker, F., Huston, G., Hinden, R., Troan, O., Bonica, R., Baker, F., Huston, G., Hinden, R., Troan, O.,
and F. Gont, "IP Fragmentation Considered Fragile", draft- and F. Gont, "IP Fragmentation Considered Fragile", Work
ietf-intarea-frag-fragile-09 (work in progress), February in Progress, draft-ietf-intarea-frag-fragile-10, May 2019.
2019.
[RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
A., Peterson, J., Sparks, R., Handley, M., and E. A., Peterson, J., Sparks, R., Handley, M., and E.
Schooler, "SIP: Session Initiation Protocol", RFC 3261, Schooler, "SIP: Session Initiation Protocol", RFC 3261,
DOI 10.17487/RFC3261, June 2002, DOI 10.17487/RFC3261, June 2002,
<https://www.rfc-editor.org/info/rfc3261>. <https://www.rfc-editor.org/info/rfc3261>.
[RFC7092] Kaplan, H. and V. Pascual, "A Taxonomy of Session [RFC7092] Kaplan, H. and V. Pascual, "A Taxonomy of Session
Initiation Protocol (SIP) Back-to-Back User Agents", Initiation Protocol (SIP) Back-to-Back User Agents",
RFC 7092, DOI 10.17487/RFC7092, December 2013, RFC 7092, DOI 10.17487/RFC7092, December 2013,
skipping to change at page 21, line 43 skipping to change at page 21, line 15
[RFC4949] Shirey, R., "Internet Security Glossary, Version 2", [RFC4949] Shirey, R., "Internet Security Glossary, Version 2",
FYI 36, RFC 4949, DOI 10.17487/RFC4949, August 2007, FYI 36, RFC 4949, DOI 10.17487/RFC4949, August 2007,
<https://www.rfc-editor.org/info/rfc4949>. <https://www.rfc-editor.org/info/rfc4949>.
[RFC7525] Sheffer, Y., Holz, R., and P. Saint-Andre, [RFC7525] Sheffer, Y., Holz, R., and P. Saint-Andre,
"Recommendations for Secure Use of Transport Layer "Recommendations for Secure Use of Transport Layer
Security (TLS) and Datagram Transport Layer Security Security (TLS) and Datagram Transport Layer Security
(DTLS)", BCP 195, RFC 7525, DOI 10.17487/RFC7525, May (DTLS)", BCP 195, RFC 7525, DOI 10.17487/RFC7525, May
2015, <https://www.rfc-editor.org/info/rfc7525>. 2015, <https://www.rfc-editor.org/info/rfc7525>.
Acknowledgments
Thanks to Roman Danyliw, Matt Richardson, Joe Touch, Scott Bradner,
Robert Sparks, Brian Weis, Benjamin Kaduk, Eric Rescorla, Alvaro
Retana, Suresh Krishnan, Ben Campbell, Mirja Kuehlewind, and Jon
Shallow for their careful reading and feedback.
Contributors
Mohamed Boucadair
Orange
mohamed.boucadair@orange.com
Flemming Andreasen
Cisco Systems, Inc.
fandreas@cisco.com
Dave Dolson
Sandvine
ddolson@sandvine.com
Authors' Addresses Authors' Addresses
Andrew Mortensen Andrew Mortensen
Arbor Networks Arbor Networks
2727 S. State St 2727 S. State St.
Ann Arbor, MI 48104 Ann Arbor, MI 48104
United States United States of America
Email: andrewmortensen@gmail.com Email: andrewmortensen@gmail.com
Tirumaleswar Reddy Tirumaleswar Reddy
McAfee McAfee
Embassy Golf Link Business Park Embassy Golf Link Business Park
Bangalore, Karnataka 560071 Bangalore, Karnataka 560071
India India
Email: TirumaleswarReddy_Konda@McAfee.com Email: TirumaleswarReddy_Konda@McAfee.com
Robert Moskowitz Robert Moskowitz
Huawei Huawei
skipping to change at page 22, line 15 skipping to change at page 22, line 26
McAfee McAfee
Embassy Golf Link Business Park Embassy Golf Link Business Park
Bangalore, Karnataka 560071 Bangalore, Karnataka 560071
India India
Email: TirumaleswarReddy_Konda@McAfee.com Email: TirumaleswarReddy_Konda@McAfee.com
Robert Moskowitz Robert Moskowitz
Huawei Huawei
Oak Park, MI 42837 Oak Park, MI 42837
United States United States of America
Email: rgm@htt-consult.com Email: rgm@htt-consult.com
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