draft-ietf-dots-requirements-10.txt   draft-ietf-dots-requirements-11.txt 
DOTS A. Mortensen DOTS A. Mortensen
Internet-Draft Arbor Networks Internet-Draft Arbor Networks
Intended status: Informational R. Moskowitz Intended status: Informational R. Moskowitz
Expires: July 6, 2018 Huawei Expires: July 27, 2018 Huawei
T. Reddy T. Reddy
McAfee, Inc. McAfee, Inc.
January 02, 2018 January 23, 2018
Distributed Denial of Service (DDoS) Open Threat Signaling Requirements Distributed Denial of Service (DDoS) Open Threat Signaling Requirements
draft-ietf-dots-requirements-10 draft-ietf-dots-requirements-11
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 coordinating Service (DDoS) Open Threat Signaling (DOTS) protocols enabling
attack response against 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 Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/. Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on July 6, 2018. This Internet-Draft will expire on July 27, 2018.
Copyright Notice Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the Copyright (c) 2018 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
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publication of this document. Please review these documents publication of this document. Please review these documents
skipping to change at page 2, line 13 skipping to change at page 2, line 13
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Context and Motivation . . . . . . . . . . . . . . . . . 2 1.1. Context and Motivation . . . . . . . . . . . . . . . . . 2
1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
2. Requirements . . . . . . . . . . . . . . . . . . . . . . . . 5 2. Requirements . . . . . . . . . . . . . . . . . . . . . . . . 5
2.1. General Requirements . . . . . . . . . . . . . . . . . . 7 2.1. General Requirements . . . . . . . . . . . . . . . . . . 6
2.2. Signal Channel Requirements . . . . . . . . . . . . . . . 8 2.2. Signal Channel Requirements . . . . . . . . . . . . . . . 7
2.3. Data Channel Requirements . . . . . . . . . . . . . . . . 12 2.3. Data Channel Requirements . . . . . . . . . . . . . . . . 12
2.4. Security Requirements . . . . . . . . . . . . . . . . . . 13 2.4. Security Requirements . . . . . . . . . . . . . . . . . . 13
2.5. Data Model Requirements . . . . . . . . . . . . . . . . . 15 2.5. Data Model Requirements . . . . . . . . . . . . . . . . . 14
3. Congestion Control Considerations . . . . . . . . . . . . . . 16 3. Congestion Control Considerations . . . . . . . . . . . . . . 15
3.1. Signal Channel . . . . . . . . . . . . . . . . . . . . . 16 3.1. Signal Channel . . . . . . . . . . . . . . . . . . . . . 15
3.2. Data Channel . . . . . . . . . . . . . . . . . . . . . . 16 3.2. Data Channel . . . . . . . . . . . . . . . . . . . . . . 15
4. Security Considerations . . . . . . . . . . . . . . . . . . . 16 4. Security Considerations . . . . . . . . . . . . . . . . . . . 16
5. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 17 5. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 17
6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 17 6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 17
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 17 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 17
7.1. Normative References . . . . . . . . . . . . . . . . . . 17 7.1. Normative References . . . . . . . . . . . . . . . . . . 17
7.2. Informative References . . . . . . . . . . . . . . . . . 19 7.2. Informative References . . . . . . . . . . . . . . . . . 19
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 19 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 20
1. Introduction 1. Introduction
1.1. Context and Motivation 1.1. Context and Motivation
Distributed Denial of Service (DDoS) attacks continue to plague Distributed Denial of Service (DDoS) attacks afflict networks of all
network operators around the globe, from Tier-1 service providers on kinds, plaguing network operators at service providers and
down to enterprises and small businesses. Attack scale and frequency enterprises around the world. High-volume attacks saturating inbound
similarly have continued to increase, in part as a result of software links are now common, as attack scale and frequency continue to
vulnerabilities leading to reflection and amplification attacks. increase.
High-volume attacks saturating inbound links are now common, and the
impact of larger-scale attacks attract the attention of international
press agencies.
The greater impact of contemporary DDoS attacks has led to increased The prevalence and impact of these DDoS attacks has led to an
focus on coordinated attack response. Many institutions and 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-premises
attack mitigation solutions themselves, or simply find themselves attack mitigation solutions themselves, or are constrained by local
constrained by local bandwidth limitations. To address such gaps, bandwidth limitations. To address such gaps, service providers have
security service providers have begun to offer on-demand traffic begun to offer on-demand traffic scrubbing services, which are
scrubbing services, which aim to separate the DDoS traffic from designed to separate the DDoS attack traffic from legitimate traffic
legitimate traffic and forward only the latter. Today each such and forward only the latter.
service offers a proprietary invocation interface for subscribers to
request attack mitigation, tying subscribers to proprietary signaling Today, these services offer proprietary interfaces for subscribers to
implementations while also limiting the subset of network elements request attack mitigation. Such proprietary interfaces tie a
subscriber to a service while also limiting the network elements
capable of participating in the attack mitigation. As a result of capable of participating in the attack mitigation. As a result of
signaling interface incompatibility, attack responses may be signaling interface incompatibility, attack responses may be
fragmentary or otherwise incomplete, leaving key players in the fragmented or otherwise incomplete, leaving operators in the attack
attack path unable to assist in the defense. path unable to assist in the defense.
The lack of a common method to coordinate a real-time response among A standardized method to coordinate a real-time response among
involved actors and network domains inhibits the speed and involved operators will increase the speed and effectiveness of DDoS
effectiveness of DDoS attack mitigation. This document describes the attack mitigation, and reduce the impact of these attacks. This
required characteristics of protocols enabling requests for DDoS document describes the required characteristics of protocols that
attack mitigation, reducing attack impact and leading to more enable attack coordination and mitigation of DDoS attacks.
efficient defensive strategies.
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 does not
dictate the form any defensive action takes. DOTS supplements calls dictate the implementation of these actions. The requirements in
for help with pertinent details about the detected attack, allowing this document are derived from [I-D.ietf-dots-use-cases] and
entities participating in DOTS to form ad hoc, adaptive alliances [I-D.ietf-dots-architecture].
against DDoS attacks as described in the DOTS use cases
[I-D.ietf-dots-use-cases]. The requirements in this document are
derived from those use cases and [I-D.ietf-dots-architecture].
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", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119]. document are to be interpreted as described in [RFC2119].
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 are 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 of servers, services, applications, and/or other the availability and/or other functionality of an attack target.
functionality of an attack target. Denial-of-service Denial-of-service considerations are discussed in detail in
considerations are discussed in detail in [RFC4732]. [RFC4732].
DDoS attack target: A network connected entity with a finite set of DDoS attack target: A network connected entity with a finite set of
resources, such as network bandwidth, memory or CPU, that is the resources, such as network bandwidth, memory or CPU, that is the
target of a DDoS attack. Potential targets include (but are not target of a DDoS attack. Potential targets include (but are not
limited to) network elements, network links, servers, and limited to) network elements, network links, servers, and
services. 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 taken to recognize and Countermeasure: An action or set of actions focused on recognizing
filter out DDoS attack traffic while passing legitimate traffic to and filtering out specific types of DDoS attack traffic while
the attack target. passing legitimate traffic to the attack target. Distinct
countermeasures can be layered to defend against attacks combining
multiple DDoS attack types.
Mitigation: A set of countermeasures enforced against traffic Mitigation: A set of countermeasures enforced against traffic
destined for the target or targets of a detected or reported DDoS destined for the target or targets of a detected or reported DDoS
attack, where countermeasure enforcement is managed by an entity attack, where countermeasure enforcement is managed by an entity
in the network path between attack sources and the attack target. in the network path between attack sources and the attack target.
Mitigation methodology is out of scope for this document. Mitigation methodology is out of scope for this document.
Mitigator: An entity, typically a network element, capable of Mitigator: An entity, typically a network element, capable of
performing mitigation of a detected or reported DDoS attack. For performing mitigation of a detected or reported DDoS attack. The
the purposes of this document, this entity is a black box capable means by which this entity performs these mitigations and how they
of mitigation, making no assumptions about availability or design are requested of it are out of scope. The mitigator and DOTS
of countermeasures, nor about the programmable interface(s) server receiving a mitigation request are assumed to belong to the
between this entity and other network elements. The mitigator and same administrative entity.
invoked DOTS server are assumed to belong to the same
administrative entity.
DOTS client: A DOTS-aware software module responsible for requesting DOTS client: A DOTS-aware software module responsible for requesting
attack response coordination with other DOTS-aware elements. attack response coordination with other DOTS-aware elements.
DOTS server: A DOTS-aware software module handling and responding to DOTS server: A DOTS-aware software module handling and responding to
messages from DOTS clients. The DOTS server enables mitigation on messages from DOTS clients. The DOTS server enables mitigation on
behalf of the DOTS client, if requested, by communicating the DOTS behalf of the DOTS client, if requested, by communicating the DOTS
client's request to the mitigator and returning selected mitigator client's request to the mitigator and returning selected mitigator
feedback to the requesting DOTS client. A DOTS server may also be feedback to the requesting DOTS client.
colocated with a mitigator.
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 a DOTS server and a DOTS client, logical concatenation of the functionality of a DOTS server and a
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 DOTS
client to upstream DOTS servers. Client-domain DOTS gateways are client for upstream DOTS servers. Client-domain DOTS gateways are
DOTS gateways that are in the DOTS client's domain, while server- DOTS gateways that are in the DOTS client's domain, while server-
domain DOTS gateways denote DOTS gateways that are in the DOTS domain DOTS gateways denote DOTS gateways that are in the DOTS
server's domain. DOTS gateways are described further in server's domain. DOTS gateways are described further in
[I-D.ietf-dots-architecture]. [I-D.ietf-dots-architecture].
Signal channel: A bidirectional, mutually authenticated Signal channel: A bidirectional, mutually authenticated
communication channel between two DOTS agents characterized by communication channel between DOTS agents that is resilient even
resilience even in conditions leading to severe packet loss, such in conditions leading to severe packet loss, such as a volumetric
as a volumetric DDoS attack causing network congestion. DDoS attack causing network congestion.
DOTS signal: A concise authenticated status/control message DOTS signal: A concise authenticated status/control message
transmitted between DOTS agents, used to indicate the client's transmitted over the signal channel between DOTS agents, used to
need for mitigation, as well as to convey the status of any indicate the client's need for mitigation, as well as to convey
requested mitigation. the status of any 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 secure communication layer between two DOTS agents Data channel: A bidirectional, mutually authentication
used for infrequent bulk exchange of data not easily or communincation channel between two DOTS agents used for infrequent
appropriately communicated through the signal channel under attack but reliable bulk exchange of data not easily or appropriately
conditions. communicated through the signal channel under attack 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].
Blacklist: A filter list of addresses, prefixes, and/or other Blacklist: A list of filters indicating sources from which traffic
identifiers indicating sources from which traffic should be should be blocked, regardless of traffic content.
blocked, regardless of traffic content.
Whitelist: A list of addresses, prefixes, and/or other identifiers Whitelist: A list of filters indicating sources from which traffic
indicating sources from which traffic should always be allowed, should always be allowed, regardless of contradictory data gleaned
regardless of contradictory data gleaned in a detected attack. in a detected attack.
Multi-homed DOTS client: A DOTS client exchanging messages with Multi-homed 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
This section describes the required features and characteristics of This section describes the required features and characteristics of
the DOTS protocols. the DOTS protocols.
The DOTS protocols enable and manage mitigation on behalf of a The DOTS protocols enable and manage mitigation on behalf of a
network domain or resource which is or may become the focus of a DDoS network domain or resource which is or may become the focus of a DDoS
attack. An active DDoS attack against the entity controlling the attack. An active DDoS attack against the entity controlling the
DOTS client need not be present before establishing a communication DOTS client need not be present before establishing a communication
channel between DOTS agents. Indeed, establishing a relationship channel between DOTS agents. Indeed, establishing a relationship
with peer DOTS agents during normal network conditions provides the with peer DOTS agents during normal network conditions provides the
foundation for more rapid attack response against future attacks, as foundation for more rapid attack response against future attacks, as
all interactions setting up DOTS, including any business or service all interactions setting up DOTS, including any business or service
level agreements, are already complete. Reachability information of level agreements, are already complete. Reachability information of
peer DOTS agents is provisioned to a DOTS client using a variety of peer DOTS agents is provisioned to a DOTS client using a variety of
manual or dynamic methods. manual or dynamic methods. Once a relationship between DOTS agents
is established, regular communication between DOTS clients and
servers enables a common 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 a mitigator's aid mounting a defense, coordinated client to request aid mounting a defense, coordinated by a DOTS
by a DOTS server, against a suspected attack, signaling within or server, against a suspected attack, signaling within or between
between domains as requested by local operators. DOTS clients should domains as requested by local operators. DOTS clients should
similarly be able to withdraw aid requests. DOTS requires no similarly be able to withdraw aid requests. DOTS requires no
justification from DOTS clients for requests for help, nor do DOTS justification from DOTS clients for requests for help, nor do DOTS
clients need to justify withdrawing help requests: the decision is clients need to justify withdrawing help requests: the decision is
local to the DOTS clients' domain. Multi-homed DOTS clients must be local to the DOTS clients' domain. Multi-homed DOTS clients must be
able to select the appropriate DOTS server(s) to which a mitigation able to select the appropriate DOTS server(s) to which a mitigation
request is to be sent. Further multi-homing considerations are out request is to be sent. The method for selecting the appropriate DOTS
of scope. server in a multi-homed environment is out of scope.
Regular feedback between DOTS clients and DOTS servers supplement the
defensive alliance by maintaining a common understanding of the DOTS
agents' health and activity. Bidirectional communication between
DOTS clients and DOTS servers is therefore critical.
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, the protocol must be resilient under extremely hostile network hand, DOTS must include protections ensuring message confidentiality,
conditions, providing continued contact between DOTS agents even as integrity and authenticity to keep the protocols from becoming
attack traffic saturates the link. Such resiliency may be developed additional vectors for the very attadcks it is meant to help fight
several ways, but characteristics such as small message size, off. On the other hand, the protocol must be resilient under
asynchronous, redundant message delivery and minimal connection extremely hostile network conditions, providing continued contact
overhead (when possible given local network policy) will tend to between DOTS agents even as attack traffic saturates the link. Such
contribute to the robustness demanded by a viable DOTS protocol. resiliency may be developed several ways, but characteristics such as
Operators of peer DOTS-enabled domains may enable quality- or class- small message size, asynchronous, redundant message delivery and
of-service traffic tagging to increase the probability of successful minimal connection overhead (when possible given local network
DOTS signal delivery, but DOTS does not require such policies be in policy) will tend to contribute to the robustness demanded by a
place. The DOTS solution indeed must be viable especially in their viable DOTS protocol. Operators of peer DOTS-enabled domains may
enable quality- or class-of-service traffic tagging to increase the
probability of successful DOTS signal delivery, but DOTS does not
require such policies be in place, and should be viable in their
absence. absence.
On the other hand, DOTS must include protections ensuring message The DOTS server and client must also have some standardized method of
confidentiality, integrity and authenticity to keep the protocol from defining the scope of any mitigation, and negotiating related
becoming another vector for the very attacks it's meant to help fight mitigation communication and actions and communications.
off. DOTS clients must be able to authenticate DOTS servers, and
vice versa, to avoid exposing new attack surfaces when deploying
DOTS; specifically, to prevent DDoS mitigation in response to DOTS
signaling from becoming a new form of attack. In order to provide
this level of protection, DOTS agents must have a way to negotiate
and agree upon the terms of protocol security. Attacks against the
transport protocol should not offer a means of attack against the
message confidentiality, integrity and authenticity.
The DOTS server and client must also have some common method of
defining the scope of any mitigation performed by a mitigator, as
well as making adjustments to other commonly configurable features,
such as targeted port numbers, exchanging black- and white-lists, and
so on.
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
operational and proprietary DDoS defenses. Future extensions MUST operational and proprietary DDoS defenses. Future extensions MUST
be backward compatible. DOTS protocols MUST use a version number be backward compatible. DOTS protocols MUST use a version number
system to distinguish protocol revisions. Implementations of system to distinguish protocol revisions. Implementations of
older protocol versions SHOULD ignore information added to DOTS older protocol versions SHOULD ignore information added to DOTS
messages as part of newer protocol versions. messages as part of newer protocol versions.
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 imposed by particular the severely constrained network conditions caused by particular
attack traffic. The protocol MUST be resilient, that is, continue attack traffic. The protocol MUST be resilient, that is, continue
operating despite message loss and out-of-order or redundant operating despite message loss and out-of-order or redundant
message delivery. In support of signaling protocol robustness, message delivery. In support of signaling protocol robustness,
DOTS signals SHOULD be conveyed over a transport not susceptible DOTS signals SHOULD be conveyed over a transport not susceptible
to Head of Line Blocking. to Head of Line Blocking.
GEN-003 Bidirectionality: To support peer health detection, to GEN-003 Bidirectionality: To support peer health detection, to
maintain an open signal channel, and to increase the probability maintain an active signal channel, and increase the probability of
of signal delivery during an attack, the signal channel MUST be 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. Unidirectional messages MUST be supported within the mitigation. Unidirectional messages MUST be supported within the
bidirectional signal channel to allow for unsolicited message bidirectional signal channel to allow for unsolicited message
delivery, enabling asynchronous notifications between DOTS agents. delivery, enabling asynchronous notifications between DOTS agents.
GEN-004 Bulk Data Exchange: Infrequent bulk data exchange between GEN-004 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 black- or coordination, permitting such tasks as population of black- or
white-listed source addresses; address or prefix group aliasing; white-listed source addresses; address or prefix group aliasing;
skipping to change at page 8, line 34 skipping to change at page 8, line 9
MTU Discovery [RFC4821]. If the PMTU cannot be discovered, DOTS MTU Discovery [RFC4821]. If the PMTU cannot be discovered, DOTS
agents SHOULD assume a PMTU of 1280 bytes. If IPv4 support on agents SHOULD assume a PMTU of 1280 bytes. If IPv4 support on
legacy or otherwise unusual networks is a consideration and PMTU legacy or otherwise unusual networks is a consideration and PMTU
is unknown, DOTS implementations MAY rely on a PMTU of 576 bytes, is unknown, DOTS implementations MAY rely on a PMTU of 576 bytes,
as discussed in [RFC0791] and [RFC1122]. as discussed in [RFC0791] and [RFC1122].
SIG-003 Channel Health Monitoring: DOTS agents MUST support exchange SIG-003 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. Peer DOTS agents SHOULD regularly send heartbeats to each health. Peer DOTS agents SHOULD regularly send heartbeats to each
other while a mitigation request is active. The heartbeat other while a mitigation request is active. The heartbeat
interval during active mitigation is not specified, but SHOULD be interval during active mitigation could be negotiable, but SHOULD
frequent enough to maintain any on-path NAT or Firewall bindings be frequent enough to maintain any on-path NAT or Firewall
during mitigation. bindings during mitigation.
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 clients MAY mitigation, and to keep the channel active, DOTS clients MAY
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
active DOTS client has not requested mitigation, in order to active DOTS client has not requested mitigation, in order to
control load. control load.
skipping to change at page 9, line 9 skipping to change at page 8, line 33
Following mutual authentication, a signal channel MUST be Following mutual authentication, a signal channel MUST be
considered active until a DOTS agent explicitly ends the session, considered active until a DOTS agent explicitly ends the session,
or either DOTS agent fails to receive heartbeats from the other or either DOTS agent fails to receive heartbeats from the other
after a mutually agreed upon retransmission procedure has been after a mutually agreed upon retransmission procedure has been
exhausted. Because heartbeat loss is much more likely during exhausted. Because heartbeat loss is much more likely during
volumetric attack, DOTS agents SHOULD avoid signal channel 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. In such received by either DOTS agent for an extended period. In such
circumstances, DOTS clients MAY attempt to reestablish the signal circumstances, DOTS clients MAY attempt to reestablish the signal
channel, but SHOULD continue to send heartbeats so that the DOTS channel, but SHOULD continue to send heartbeats so that the DOTS
server knows the session is still alive. DOTS servers SHOULD server knows the session is still alive. DOTS servers are assumed
monitor the attack, using feedback from the mitigator and other to have the ability to monitor the attack, using feedback from the
available sources, and MAY use the absence of attack traffic and mitigator and other available sources, and MAY use the absence of
lack of client heartbeats as an indication the signal channel is attack traffic and lack of client heartbeats as an indication the
defunct. signal channel is defunct.
SIG-004 Channel Redirection: In order to increase DOTS operational SIG-004 Channel Redirection: In order to increase DOTS operational
flexibility and scalability, DOTS servers SHOULD be able to flexibility and scalability, DOTS servers SHOULD be able to
redirect DOTS clients to another DOTS server at any time. DOTS redirect DOTS clients to another DOTS server at any time. DOTS
clients MUST NOT assume the redirection target DOTS server shares clients MUST NOT assume the redirection target DOTS server shares
security state with the redirecting DOTS server. DOTS clients MAY security state with the redirecting DOTS server. DOTS clients are
attempt abbreviated security negotiation methods supported by the free to attempt abbreviated security negotiation methods supported
protocol, such as DTLS session resumption, but MUST be prepared to by the protocol, such as DTLS session resumption, but MUST be
negotiate new security state with the redirection target DOTS prepared to negotiate new security state with the redirection
server. target DOTS server.
Due to the increased likelihood of packet loss caused by link Due to the increased likelihood of packet loss caused by link
congestion during an attack, DOTS servers SHOULD NOT redirect congestion during an attack, DOTS servers SHOULD NOT redirect
while mitigation is enabled during an active attack against a while mitigation is enabled during an active attack against a
target in the DOTS client's domain. target in the DOTS client's domain.
SIG-005 Mitigation Requests and Status: Authorized DOTS clients MUST SIG-005 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 mitigation request status in response to granted servers MUST send status to the DOTS clients about mitigation
DOTS clients requests for mitigation. If a DOTS server rejects an requests. If a DOTS server rejects an authorized request for
authorized request for mitigation, the DOTS server MUST include a mitigation, the DOTS server MUST include a reason for the
reason for the rejection in the status message sent to the client. rejection in the status message sent to the client.
Due to the higher likelihood of packet loss during a DDoS attack, Due to the higher likelihood of packet loss during a DDoS attack,
DOTS servers SHOULD regularly send mitigation status to authorized DOTS servers SHOULD regularly send mitigation status to authorized
DOTS clients which have requested and been granted mitigation, DOTS clients which have requested and been granted mitigation,
regardless of client requests for mitigation status. regardless of client requests for mitigation status.
When DOTS client-requested mitigation is active, DOTS server When DOTS client-requested mitigation is active, DOTS server
status messages SHOULD include the following mitigation metrics: status messages SHOULD include the following mitigation metrics:
* Total number of packets blocked by the mitigation * Total number of packets blocked by the mitigation
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but terminating. but terminating.
The initial active-but-terminating period is implementation- and The initial active-but-terminating period is implementation- and
deployment- specific, but SHOULD be sufficiently long to absorb deployment- specific, but SHOULD be sufficiently long to absorb
latency incurred by route propagation. If the client requests latency incurred by route propagation. If the client requests
mitigation again before the initial active-but-terminating period mitigation again before the initial active-but-terminating period
elapses, the DOTS server MAY exponentially increase the active- elapses, the DOTS server MAY exponentially increase the active-
but-terminating period up to a maximum of 300 seconds (5 minutes). but-terminating period up to a maximum of 300 seconds (5 minutes).
After the active-but-terminating period elapses, the DOTS server After the active-but-terminating period elapses, the DOTS server
MUST treat the mitigation as terminated, as the DOTS client is no MUST treat the mitigation as terminated, as the DOTS client is no
longer responsible for the mitigation. For example, if there is a longer responsible for the mitigation.
financial relationship between the DOTS client and server domains,
the DOTS client ceases incurring cost at this point.
SIG-006 Mitigation Lifetime: DOTS servers MUST support mitigation SIG-006 Mitigation Lifetime: DOTS servers MUST support mitigations
lifetimes, and MUST terminate a mitigation when the lifetime for a negotiated time interval or lifetime, and MUST terminate a
elapses. DOTS servers also MUST support renewal of mitigation mitigation when the lifetime elapses. DOTS servers also MUST
lifetimes in mitigation requests from DOTS clients, allowing support renewal of mitigation lifetimes in mitigation requests
clients to extend mitigation as necessary for the duration of an from DOTS clients, allowing clients to extend mitigation as
attack. necessary for the 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,
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obtain mitigation scope. obtain mitigation scope.
SIG-008 Mitigation Efficacy: When a mitigation request is active, SIG-008 Mitigation Efficacy: When a mitigation request is active,
DOTS clients SHOULD transmit a metric of perceived mitigation DOTS clients SHOULD transmit a metric of perceived mitigation
efficacy to the DOTS server. DOTS servers MAY use the efficacy efficacy to the DOTS server. DOTS servers MAY use the efficacy
metric to adjust countermeasures activated on a mitigator on metric to adjust countermeasures activated on a mitigator on
behalf of a DOTS client. behalf of a DOTS client.
SIG-009 Conflict Detection and Notification: Multiple DOTS clients SIG-009 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 for pools of protected resources as a result mitigation requests as a result of misconfiguration, operator
of misconfiguration, operator error, or compromised DOTS clients. error, or compromised DOTS clients. DOTS servers in the same
DOTS servers in the same administrative domain attempting to honor administrative domain attempting to honor conflicting requests may
conflicting requests may flap network route or DNS information, flap network route or DNS information, degrading the networks
degrading the networks attempting to participate in attack attempting to participate in attack response with the DOTS
response with the DOTS clients. DOTS servers in a single clients. DOTS servers in a single administrative domain SHALL
administrative domain SHALL detect such conflicting requests, and detect such conflicting requests, and SHALL notify the DOTS
SHALL notify the DOTS clients in conflict. The notification clients in conflict. The notification SHOULD indicate the nature
SHOULD indicate the nature and scope of the conflict, for example, and scope of the conflict, for example, the overlapping prefix
the overlapping prefix range in a conflicting mitigation request. range in a conflicting mitigation request.
SIG-010: Network Address Translator Traversal: DOTS clients may be SIG-010: 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 (BCPs) for NAT traversal. follow established best common practices established in BCP 127
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, which must operate between DOTS agents. Unlike the signal channel, the data channel is
nominally even when confronted with signal degradation due to not expected to be constructed to deal with attack conditions. As
significant packet loss, the data channel is not expected to be the primary function of the data channel is data exchange, a reliable
constructed to deal with attack conditions. As the primary function transport is required in order for DOTS agents to detect data
of the data channel is data exchange, a reliable transport is delivery success or failure.
required in order for DOTS agents to detect data delivery success or
failure.
The DOTS data channel protocol MUST be extensible. We anticipate the The data channel provides a protocol for DOTS configuration,
data channel will be used for such purposes as configuration or management. For example, a DOTS client may submit to a DOTS server a
resource discovery. For example, a DOTS client may submit to a DOTS collection of prefixes it wants to refer to by alias when requesting
server a collection of prefixes it wants to refer to by alias when mitigation, to which the server would respond with a success status
requesting mitigation, to which the server would respond with a and the new prefix group alias, or an error status and message in the
success status and the new prefix group alias, or an error status and event the DOTS client's data channel request failed.
message in the event the DOTS client's data channel request failed.
The transactional nature of such data exchanges suggests a separate
set of requirements for the data channel, while the potentially
sensitive content sent between DOTS agents requires extra precautions
to ensure data privacy and authenticity.
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 order sent.
DATA-002 Data privacy and integrity: Transmissions over the data DATA-002 Data privacy and integrity: Transmissions over the data
channel are likely to contain operationally or privacy-sensitive channel are likely to contain operationally or privacy-sensitive
information or instructions from the remote DOTS agent. Theft or information or instructions from the remote DOTS agent. Theft or
modification of data channel transmissions could lead to modification of data channel 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 below). Consequently data sent over
the data channel MUST be encrypted and authenticated using current the data channel MUST be encrypted and authenticated using current
industry best practices. DOTS servers MUST enable means to IETF best practices. DOTS servers MUST enable means to prevent
prevent leaking operationally or privacy-sensitive data. Although leaking operationally or privacy-sensitive data. Although
administrative entities participating in DOTS may detail what data administrative entities participating in DOTS may detail what data
may be revealed to third-party DOTS agents, such considerations may be revealed to third-party DOTS agents, such considerations
are not in scope for this document. are not in scope for this document.
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 2.2, DOTS server implementations channel requirements in Section 2.1 and Section 2.2, DOTS server
MUST provide an interface to configure resource identifiers, as implementations MUST provide an interface to configure resource
described in SIG-007. DOTS server implementations MAY expose identifiers, as described in SIG-007. DOTS server implementations
additional configurability. Additional configurability is MAY expose additional configurability. Additional configurability
implementation-specific. is implementation-specific.
DATA-004 Black- and whitelist management: DOTS servers MUST provide DATA-004 Black- and whitelist management: DOTS servers MUST provide
methods for DOTS clients to manage black- and white-lists of methods for DOTS clients to manage black- and white-lists of
traffic destined for resources belonging to a client. traffic destined for resources belonging to a client.
For example, a DOTS client should be able to create a black- or For example, a DOTS client should be able to create a black- or
whitelist entry, retrieve a list of current entries from either whitelist 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.
skipping to change at page 14, line 21 skipping to change at page 13, line 36
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 options are not specified, the protocols MUST follow current
industry best practices for encryption and message authentication. industry best practices for encryption and message authentication.
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 be able to in cryptanalysis and traffic analysis, DOTS agents MUST be able to
negotiate the terms and mechanisms of protocol security, subject negotiate the terms and mechanisms of protocol security, subject
to the interoperability and signal message size requirements to the interoperability and signal message size requirements in
above. 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.
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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, modification
or deletion of scope aliases and black-/white-lists when the DOTS or deletion of scope aliases and black-/white-lists when the DOTS
client is unauthorized. 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
The value of DOTS is in standardizing a mechanism to permit elements, A well-structured DOTS data model is critical to the development of
networks or domains under threat of DDoS attack to request aid successful DOTS protocols.
mitigating the effects of any such attack. A well-structured DOTS
data model is therefore critical to the development of successful
DOTS protocols.
DM-001: Structure: The data model structure for the DOTS protocol DM-001: Structure: The data model structure for the DOTS protocol
may be described by a single module, or be divided into related MAY 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 sub-modules. 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 DM-003: Mitigation Status Representation: The data model MUST
skipping to change at page 16, line 42 skipping to change at page 16, line 7
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 TCP may order message delivery. Data channel implementations using TCP may
rely on the TCP implementation's built-in congestion control rely on the TCP implementation's built-in congestion control
mechanisms. mechanisms.
4. Security Considerations 4. Security Considerations
DOTS is at risk from three primary attacks: This document informs future protocols under development, and so does
not have its security considerations of its own. However, naive DOTS
deployment potentially exposes networks to new attack vectors. The
three primary attack vectors are DOTS agent impersonation, traffic
injection, and signal blocking.
o DOTS agent impersonation Impersonation of either DOTS server or DOTS client could have
catastrophic impact on operations in either domain. Should an
attacker develop the ability to impersonate a DOTS client, that
attacker can affect policy on the network path to the DOTS client's
domain, up to and including instantiation of blacklists blocking all
inbound traffic to networks for which the DOTS client is authorized
to request mitigation. Similarly, an impersonated DOTS server may be
able to act as a sort of malicious DOTS gateway, intercepting
requests from the downstream DOTS client, modifying them to inflict
the desired impact on traffic to or from the DOTS client's domain.
Among other things, this malicious DOTS gateway might receive
mitigation requests from the DOTS client, and simply discard them,
ensuring no mitigation is ever applied.
o Traffic injection Traffic injection into a naive DOTS deployment could allow an
attacker to affect DOTS operations selectively. Rather than
impersonating a DOTS agent directly, the attacker crafts DOTS signal
or data channel messages in such a way that the targeted DOTS agent
treats them as if they originated with a legitimate DOTS agent, for
example, by spoofing the sender's IP address. As with agent
impersonation, the attacker capable of injecting traffic can affect
the network path to addresses for which the DOTS client is authorized
to request mitigation.
o Signaling blocking Blocking communication between DOTS agents-signal blocking-has the
potential to disrupt the core function of DOTS, which is to request
mitigation of active or expected DDoS attacks. The DOTS signal
channel is expected to operate over congested inbound links, and, as
described in Section 2.2, the signal channel protocol must be
designed for minimal data transfer to reduce the incidence of signal
blocking.
The DOTS protocol MUST be designed for minimal data transfer to As detailed in Section 2.4, DOTS implementations require mutual
address the blocking risk. Impersonation and traffic injection authentication of DOTS agents in order to make agent impersonation
mitigation can be managed through current secure communications best and traffic injection more difficult. However, impersonation or
practices. See Section 2.4 above for a detailed discussion. traffic injection may still be possible as a result of credential
theft, implementation flaws, or compromise of DOTS agents. Operators
should take steps to reduce attack surfaces through current secure
network communications best practices.
5. Contributors 5. Contributors
Mohamed Boucadair Mohamed Boucadair
Orange Orange
mohamed.boucadair@orange.com mohamed.boucadair@orange.com
Flemming Andreasen Flemming Andreasen
Cisco Systems, Inc. Cisco Systems, Inc.
skipping to change at page 18, line 33 skipping to change at page 18, line 28
[RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing
Architecture", RFC 4291, DOI 10.17487/RFC4291, February Architecture", RFC 4291, DOI 10.17487/RFC4291, February
2006, <https://www.rfc-editor.org/info/rfc4291>. 2006, <https://www.rfc-editor.org/info/rfc4291>.
[RFC4632] Fuller, V. and T. Li, "Classless Inter-domain Routing [RFC4632] Fuller, V. and T. Li, "Classless Inter-domain Routing
(CIDR): The Internet Address Assignment and Aggregation (CIDR): The Internet Address Assignment and Aggregation
Plan", BCP 122, RFC 4632, DOI 10.17487/RFC4632, August Plan", BCP 122, RFC 4632, DOI 10.17487/RFC4632, August
2006, <https://www.rfc-editor.org/info/rfc4632>. 2006, <https://www.rfc-editor.org/info/rfc4632>.
[RFC4787] Audet, F., Ed. and C. Jennings, "Network Address
Translation (NAT) Behavioral Requirements for Unicast
UDP", BCP 127, RFC 4787, DOI 10.17487/RFC4787, January
2007, <https://www.rfc-editor.org/info/rfc4787>.
[RFC4821] Mathis, M. and J. Heffner, "Packetization Layer Path MTU [RFC4821] Mathis, M. and J. Heffner, "Packetization Layer Path MTU
Discovery", RFC 4821, DOI 10.17487/RFC4821, March 2007, Discovery", RFC 4821, DOI 10.17487/RFC4821, March 2007,
<https://www.rfc-editor.org/info/rfc4821>. <https://www.rfc-editor.org/info/rfc4821>.
[RFC5405] Eggert, L. and G. Fairhurst, "Unicast UDP Usage Guidelines [RFC5405] Eggert, L. and G. Fairhurst, "Unicast UDP Usage Guidelines
for Application Designers", RFC 5405, for Application Designers", RFC 5405,
DOI 10.17487/RFC5405, November 2008, DOI 10.17487/RFC5405, November 2008,
<https://www.rfc-editor.org/info/rfc5405>. <https://www.rfc-editor.org/info/rfc5405>.
[RFC6888] Perreault, S., Ed., Yamagata, I., Miyakawa, S., Nakagawa,
A., and H. Ashida, "Common Requirements for Carrier-Grade
NATs (CGNs)", BCP 127, RFC 6888, DOI 10.17487/RFC6888,
April 2013, <https://www.rfc-editor.org/info/rfc6888>.
[RFC7857] Penno, R., Perreault, S., Boucadair, M., Ed., Sivakumar,
S., and K. Naito, "Updates to Network Address Translation
(NAT) Behavioral Requirements", BCP 127, RFC 7857,
DOI 10.17487/RFC7857, April 2016,
<https://www.rfc-editor.org/info/rfc7857>.
[RFC8085] Eggert, L., Fairhurst, G., and G. Shepherd, "UDP Usage [RFC8085] Eggert, L., Fairhurst, G., and G. Shepherd, "UDP Usage
Guidelines", BCP 145, RFC 8085, DOI 10.17487/RFC8085, Guidelines", BCP 145, RFC 8085, DOI 10.17487/RFC8085,
March 2017, <https://www.rfc-editor.org/info/rfc8085>. March 2017, <https://www.rfc-editor.org/info/rfc8085>.
[RFC5952] Kawamura, S. and M. Kawashima, "A Recommendation for IPv6 [RFC5952] Kawamura, S. and M. Kawashima, "A Recommendation for IPv6
Address Text Representation", RFC 5952, Address Text Representation", RFC 5952,
DOI 10.17487/RFC5952, August 2010, DOI 10.17487/RFC5952, August 2010,
<https://www.rfc-editor.org/info/rfc5952>. <https://www.rfc-editor.org/info/rfc5952>.
7.2. Informative References 7.2. Informative References
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