draft-ietf-dots-requirements-00.txt   draft-ietf-dots-requirements-01.txt 
DOTS A. Mortensen DOTS A. Mortensen
Internet-Draft Arbor Networks, Inc. Internet-Draft Arbor Networks, Inc.
Intended status: Informational R. Moskowitz Intended status: Informational R. Moskowitz
Expires: April 21, 2016 HTT Consulting Expires: September 19, 2016 HTT Consulting
T. Reddy T. Reddy
Cisco Systems, Inc. Cisco Systems, Inc.
October 19, 2015 March 18, 2016
DDoS Open Threat Signaling Requirements Distributed Denial of Service (DDoS) Open Threat Signaling Requirements
draft-ietf-dots-requirements-00 draft-ietf-dots-requirements-01
Abstract Abstract
This document defines the requirements for the DDoS Open Threat This document defines the requirements for the Distributed Denial of
Signaling (DOTS) protocols coordinating attack response against Service (DDoS) Open Threat Signaling (DOTS) protocols coordinating
Distributed Denial of Service (DDoS) attacks. attack response against DDoS attacks.
Status of This Memo Status of This Memo
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This Internet-Draft will expire on April 21, 2016. This Internet-Draft will expire on September 19, 2016.
Copyright Notice Copyright Notice
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . 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 . . . . . . . . . . . . . . . . . . 6 2.1. General Requirements . . . . . . . . . . . . . . . . . . 6
2.2. Operational requirements . . . . . . . . . . . . . . . . 7 2.2. Operational Requirements . . . . . . . . . . . . . . . . 7
2.3. Data channel requirements . . . . . . . . . . . . . . . . 9 2.3. Data Channel Requirements . . . . . . . . . . . . . . . . 10
2.4. Data model requirements . . . . . . . . . . . . . . . . . 10 2.4. Security requirements . . . . . . . . . . . . . . . . . . 11
3. Congestion Control Considerations . . . . . . . . . . . . . . 10 3. Congestion Control Considerations . . . . . . . . . . . . . . 12
4. Security Considerations . . . . . . . . . . . . . . . . . . . 10 4. Security Considerations . . . . . . . . . . . . . . . . . . . 12
5. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . 11 5. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 12
5.1. 00 revision . . . . . . . . . . . . . . . . . . . . . . . 11 6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 12
5.2. Initial revision . . . . . . . . . . . . . . . . . . . . 11 7. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . 13
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 11 7.1. 01 revision . . . . . . . . . . . . . . . . . . . . . . . 13
6.1. Normative References . . . . . . . . . . . . . . . . . . 11 7.2. 00 revision . . . . . . . . . . . . . . . . . . . . . . . 13
6.2. Informative References . . . . . . . . . . . . . . . . . 11 7.3. Initial revision . . . . . . . . . . . . . . . . . . . . 13
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 14
8.1. Normative References . . . . . . . . . . . . . . . . . . 14
8.2. Informative References . . . . . . . . . . . . . . . . . 14
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 15
1. Introduction 1. Introduction
1.1. Overview 1.1. Context and Motivation
Distributed Denial of Service (DDoS) attacks continue to plague Distributed Denial of Service (DDoS) attacks continue to plague
networks around the globe, from Tier-1 service providers on down to networks around the globe, from Tier-1 service providers on down to
enterprises and small businesses. Attack scale and frequency enterprises and small businesses. Attack scale and frequency
similarly have continued to increase, thanks to software similarly have continued to increase, in part as a result of software
vulnerabilities leading to reflection and amplification attacks. vulnerabilities leading to reflection and amplification attacks.
Once staggering attack traffic volume is now the norm, and the impact Once staggering attack traffic volume is now the norm, and the impact
of larger-scale attacks attract the attention of international press of larger-scale attacks attract the attention of international press
agencies. agencies.
The higher profile and greater impact of contemporary DDoS attacks The greater impact of contemporary DDoS attacks has led to increased
has led to increased focus on coordinated attack response. Many focus on coordinated attack response. Many institutions and
institutions and enterprises lack the resources or expertise to enterprises lack the resources or expertise to operate on-premise
operate on-premise attack prevention solutions themselves, or simply attack prevention solutions themselves, or simply find themselves
find themselves constrained by local bandwidth limitations. To constrained by local bandwidth limitations. To address such gaps,
address such gaps, security service providers have begun to offer on- security service providers have begun to offer on-demand traffic
demand traffic scrubbing services. Each service offers its own scrubbing services. Each service offers its own interface for
interface for subscribers to request attack mitigation, tying subscribers to request attack mitigation, tying subscribers to
subscribers to proprietary implementations while also limiting the proprietary implementations while also limiting the subset of network
subset of network elements capable of participating in the attack elements capable of participating in the attack response. As a
response. As a result of incompatibility across services, attack result of incompatibility across services, attack responses may be
response may be fragmentary or otherwise incomplete, leaving key fragmentary or otherwise incomplete, leaving key players in the
players in the attack path unable to assist in the defense. attack path unable to assist in the defense.
There are many ways to respond to an ongoing DDoS attack, some of
them better than others, but the lack of a common method to
coordinate a real-time response across layers and network domains
inhibits the speed and effectiveness of DDoS attack mitigation.
DOTS was formed to address this lack. The DOTS protocols are
therefore not concerned with the form of response, but rather with
communicating the need for a response, supplementing the call for
help with pertinent details about the detected attack. To achieve
this aim, the protocol must permit the DOTS client to request or
withdraw a request for coordinated mitigation; to set the scope of
mitigation, restricted to the client's network space; and to supply
summarized attack information and additional hints the DOTS server
elements can use to increase the accuracy and speed of the attack
response.
The protocol must also continue to operate even in extreme network
conditions. It must be resilient enough to ensure a high probability
of signal delivery in spite of high packet loss rates. As such,
elements should be in regular, bidirectional contact to measure peer
health, provide mitigation-related feedback, and allow for active
mitigation adjustments.
Lastly, the protocol must take care to ensure the confidentiality, The lack of a common method to coordinate a real-time response among
integrity and authenticity of messages passed between peers to involved actors and network domains inhibits the speed and
prevent the protocol from being repurposed to contribute to the very effectiveness of DDoS attack mitigation. This document describes the
attacks it's meant to deflect. required characteristics of DOTS protocols that would mitigate
contemporary DDoS attack impact and lead to more efficient defensive
strategies.
Drawing on the DOTS use cases [I-D.ietf-dots-use-cases] for DOTS is less concerned with the form of defensive action than with
reference, this document details the requirements for protocols communicating the need for that action. DOTS supplements calls for
achieving the DOTS goal of standards-based open threat signaling. help with pertinent details about the detected attack, allowing
entities participating in DOTS to form ad hoc, adaptive alliances
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.
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].
The following terms are used to define relationships between This document adopts the following terms:
elements, the data they exchange, and methods of communication among
them:
attack telemetry: collected network traffic characteristics defining DDoS: A distributed denial-of-service attack, in which of traffic
the nature of a DDoS attack. originating from multiple sources are directed at a target on a
network. DDoS attacks are intended to cause a negative impact on
the availability of servers, services, applications, and/or other
functionality of an attack target. Denial-of-service
considerations are discussed in detail in [RFC4732].
mitigation: A defensive response against a detected DDoS attack, DDoS attack target: A networked server, network service or
performed by an entity in the network path between attack sources application that is the focus of a DDoS attack.
and the attack target, either through inline deployment or some
form of traffic diversion. The form mitigation takes is out of
scope for this document.
mitigator: A network element capable of performing mitigation of a DDoS attack telemetry: Collected network traffic characteristics
detected DDoS attack. defining the nature of a DDoS attack. This document makes no
assumptions regarding telemetry collection methodology.
DOTS client: A DOTS-aware network element requesting attack response Countermeasure: An action or set of actions taken to recognize and
coordination with another DOTS-aware element, with the expectation filter out DDoS attack traffic while passing legitimate traffic to
that the remote element is capable of helping fend off the attack the attack target.
against the client.
DOTS server: A DOTS-aware network element handling and responding to Mitigation: A set of countermeasures enforced against traffic
messages from a DOTS client. The DOTS server MAY enable destined for the target or targets of a detected or reported DDoS
mitigation on behalf of the DOTS client, if requested, by attack, where countermeasure enforcement is managed by an entity
communicating the DOTS client's request to the mitigator and in the network path between attack sources and the attack target.
relaying any mitigator feedback to the client. A DOTS server may Mitigation methodology is out of scope for this document.
also be a mitigator.
DOTS relay: A DOTS-aware network element positioned between a DOTS Mitigator: An entity, typically a network element, capable of
server and a DOTS client. A DOTS relay receives messages from a performing mitigation of a detected or reported DDoS attack. For
DOTS client and relays them to a DOTS server, and similarly passes the purposes of this document, this entity is a black box capable
messages from the DOTS server to the DOTS client. of mitigation, making no assumptions about availability or design
of countermeasures, nor about the programmable interface between
this entity and other network elements. The mitigator and DOTS
server are assumed to belong to the same administrative entity.
DOTS agents: A collective term for DOTS clients, servers and relays. DOTS client: A DOTS-aware software module responsible for requesting
attack response coordination with other DOTS-aware elements.
signal channel: A bidirectional, mutually authenticated DOTS server: A DOTS-aware software module handling and responding to
messages from DOTS clients. The DOTS server MAY enable mitigation
on behalf of the DOTS client, if requested, by communicating the
DOTS client's request to the mitigator and relaying any mitigator
feedback to the requesting DOTS client. A DOTS server may also be
a mitigator.
DOTS relay: A DOTS-aware software module positioned between a DOTS
server and a DOTS client in the signaling path. A DOTS relay
receives messages from a DOTS client and relays them to a DOTS
server, and similarly passes messages from the DOTS server to the
DOTS client. A DOTS relay acts as a proxy or bridge between
stateful and stateless transport signaling, and may also aggregate
signaling from multiple downstream DOTS clients into a single
session with an upstream DOTS server or DOTS relay.
DOTS agents: Any DOTS functional element, including DOTS clients,
DOTS servers and DOTS relays.
Signal channel: A bidirectional, mutually authenticated
communication layer between DOTS agents characterized by communication layer between DOTS agents characterized by
resilience even in conditions leading to severe packet loss, such resilience even in conditions leading to severe packet loss, such
as a volumetric DDoS attack causing network congestion. as a volumetric 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 client's need transmitted between DOTS agents, used to indicate client's need
for mitigation, as well as to convey the status of any requested for mitigation, as well as to convey the status of any requested
mitigation. mitigation.
heartbeat: A keep-alive message transmitted between DOTS agents over Heartbeat: A message transmitted between DOTS agents over the signal
the signal channel, used to measure peer health. Heartbeat channel, used as a keep-alive and to measure peer health.
functionality is not required to be distinct from signal.
client signal: A message sent from a DOTS client to a DOTS server Client signal: A message sent from a DOTS client to a DOTS server or
over the signal channel, possibly traversing a DOTS relay, DOTS relay over the signal channel, indicating the DOTS client's
indicating the DOTS client's need for mitigation, as well as the need for mitigation, as well as the scope of any requested
scope of any requested mitigation, optionally including detected mitigation, optionally including additional attack details to
attack telemetry to supplement server-initiated mitigation. supplement server-initiated mitigation.
server signal: A message sent from a DOTS server to a DOTS client Server signal: A message sent from a DOTS server to a DOTS client or
over the signal channel. Note that a server signal is not a DOTS relay over the signal channel. Note that a server signal is
response to client signal, but a DOTS server-initiated status not a response to client signal, but a DOTS server-initiated
message sent to the DOTS client, containing information about the status message sent to DOTS clients with which the server has
status of any requested mitigation and its efficacy. established signaling sessions, containing information about the
status of DOTS client-requested mitigation and its efficacy.
data channel: A secure communication layer between client and server Data channel: A secure communication layer between DOTS clients and
used for infrequent bulk exchange of data not easily or DOTS servers used for infrequent bulk exchange of data not easily
appropriately communicated through the signal channel under attack or appropriately communicated through the signal channel under
conditions. attack conditions.
blacklist: a list of source addresses or prefixes from which traffic Blacklist: A list of addresses, prefixes and/or other identifiers
should be blocked. indicating sources from which traffic should be blocked,
regardless of traffic content.
whitelist: a list of source addresses or prefixes from which traffic Whitelist: A list of addresses, prefixes and/or other
should always be allowed, regardless of contradictory data gleaned identifiersfrom indicating sources from which traffic should
in a detected attack. always be allowed, regardless of contradictory data gleaned in a
detected attack.
Multi-homed DOTS client: A DOTS client exchanging messages with
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 requirements are informed by the use cases the DOTS protocols.
described in [I-D.ietf-dots-use-cases].
DOTS is an advisory protocol. An active DDoS attack against the
entity controlling the DOTS client need not be present before
establishing DOTS communication between DOTS agents. Indeed,
establishing a relationship with peer DOTS agents during nominal
network conditions provides the foundation for more rapid attack
response against future attacks, as all interactions setting up DOTS,
including any business or service level agreements, are already
complete.
DOTS must at a minimum make it possible for a DOTS client to request DOTS must at a minimum make it possible for a DOTS client to request
a DOTS server's aid in mounting a coordinated defense against a a DOTS server's aid in mounting a coordinated defense against a
detected attack, by signaling inter- or intra-domain using the DOTS detected attack, signaling inter- or intra-domain as requested by
protocol. DOTS clients should similarly be able to withdraw aid local operators. DOTS clients should similarly be able to withdraw
requests arbitrarily. Regular feedback between DOTS client and aid requests. DOTS requires no justification from DOTS clients for
server supplement the defensive alliance by maintaining a common requests for help, nor must DOTS clients justify withdrawing help
requests: the decision is local to the entity owning the DOTS
clients. Regular feedback between DOTS clients and DOTS server
supplement the defensive alliance by maintaining a common
understanding of DOTS peer health and activity. Bidirectional understanding of DOTS peer health and activity. Bidirectional
communication between DOTS client and server is therefore critical. communication between DOTS clients and DOTS servers is therefore
critical.
Yet the DOTS protocol must also work with a set of competing Yet DOTS must also work with a set of competing operational goals.
operational goals. On the one hand, the protocol must be resilient On the one hand, the protocol must be resilient under extremely
under extremely hostile network conditions, providing continued hostile network conditions, providing continued contact between DOTS
contact between DOTS agents even as attack traffic saturates the agents even as attack traffic saturates the link. Such resiliency
link. Such resiliency may be developed several ways, but may be developed several ways, but characteristics such as small
characteristics such as small message size, asynchronous, redundant message size, asynchronous, redundant message delivery and minimal
message delivery and minimal connection overhead (when possible given connection overhead (when possible given local network policy) will
local network policy) with a given network will tend to contribute to tend to contribute to the robustness demanded by a viable DOTS
the robustness demanded by a viable DOTS protocol. 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 requires no such policies
be in place. The DOTS solution indeed must be viable especially in
their absence.
On the other hand, DOTS must have adequate message confidentiality, On the other hand, DOTS must include protections ensuring message
integrity and authenticity to keep the protocol from becoming another confidentiality, integrity and authenticity to keep the protocol from
vector for the very attacks it's meant to help fight off. The DOTS becoming another vector for the very attacks it's meant to help fight
client must be authenticated to the DOTS server, and vice versa, for off. DOTS clients must be able to authenticate DOTS servers, and
DOTS to operate safely, meaning the DOTS agents must have a way to vice versa, for DOTS to operate safely, meaning the DOTS agents must
negotiate and agree upon the terms of protocol security. Attacks have a way to negotiate and agree upon the terms of protocol
against the transport protocol should not offer a means of attack security. Attacks against the transport protocol should not offer a
against the message confidentiality, integrity and authenticity. means of attack against the message confidentiality, integrity and
authenticity.
The DOTS server and client must also have some common method of The DOTS server and client must also have some common method of
defining the scope of any mitigation performed by the mitigator, as defining the scope of any mitigation performed by the mitigator, as
well as making adjustments to other commonly configurable features, well as making adjustments to other commonly configurable features,
such as listen ports, exchanging black- and white-lists, and so on. such as listen ports, exchanging black- and white-lists, and so on.
Finally, DOTS should provide sufficient extensibility to meet local, Finally, DOTS should provide sufficient extensibility to meet local,
vendor or future needs in coordinated attack defense, although this vendor or future needs in coordinated attack defense, although this
consideration is necessarily superseded by the other operational consideration is necessarily superseded by the other operational
requirements. requirements.
2.1. General Requirements 2.1. General Requirements
G-001 Interoperability: DOTS's objective is to develop a standard GEN-001 Extensibility: Protocols and data models developed as part
mechanism for signaling detected ongoing DDoS attacks. That of DOTS MUST be extensible in order to keep DOTS adaptable to
objective is unattainable without well-defined specifications for operational and proprietary DDoS defenses. Future extensions MUST
any protocols or data models emerging from DOTS. All protocols, be backward compatible.
data models and interfaces MUST be detailed enough to ensure
interoperable implementations.
G-002 Extensibility: Any protocols or data models developed as part
of DOTS MUST be designed to support future extensions. Provided
they do not undermine the interoperability and backward
compatibility requirements, extensions are a critical part of
keeping DOTS adaptable to changing operational and proprietary
needs to keep pace with evolving DDoS attack methods.
G-003 Resilience: The signaling protocol MUST be designed to GEN-002 Resilience and Robustness: The signaling protocol MUST be
maximize the probability of signal delivery even under the designed to maximize the probability of signal delivery even under
severely constrained network conditions imposed by the attack the severely constrained network conditions imposed by particular
traffic. The protocol SHOULD 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
signal delivery. signal delivery.
G-004 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 open signal channel, and to increase the probability
of signal delivery during attack, the signal channel MUST be of signal delivery during 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. mitigation. Unidirectional messages MUST be supported within the
bidirectional signal channel to allow for unsolicited message
delivery, enabling asynchronous notifications between agents.
G-005 Sub-MTU Message Size: To avoid message fragmentation and the GEN-004 Sub-MTU Message Size: To avoid message fragmentation and the
consequently decreased probability of message delivery, signaling consequently decreased probability of message delivery, signaling
protocol message size MUST be kept under signaling path Maximum protocol message size MUST be kept under signaling path Maximum
Transmission Unit (MTU), including the byte overhead of any Transmission Unit (MTU), including the byte overhead of any
encapsulation, transport headers, and transport- or message-level encapsulation, transport headers, and transport- or message-level
security. security.
G-006 Message Integrity: DOTS protocols MUST take steps to protect GEN-005 Bulk Data Exchange: Infrequent bulk data exchange between
the confidentiality, integrity and authenticity of messages sent DOTS agents can also significantly augment attack response
between client and server. While specific transport- and message-
level security options are not specified, the protocols MUST
follow current industry best practices for encryption and message
authentication.
In order for DOTS protocols to remain secure despite advancements
in cryptanalysis, DOTS agents MUST be able to negotiate the terms
and mechanisms of protocol security, subject to the
interoperability and signal message size requirements above.
G-007 Message Replay Protection: In order to prevent a passive
attacker from capturing and replaying old messages, DOTS protocols
MUST provide a method for replay detection, such as including a
timestamp or sequence number in every heartbeat and signal sent
between DOTS agents.
G-008 Bulk Data Exchange: Infrequent bulk data exchange between DOTS
client and server 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 group aliasing; exchange of white-listed source addresses; address or prefix group aliasing;
incident reports; and other hinting or configuration supplementing exchange of incident reports; and other hinting or configuration
attack response. supplementing attack response.
As the resilience requirements for DOTS mandate small signal
message size, a separate, secure data channel utilizing an
established reliable protocol SHOULD be used for bulk data
exchange. The mechanism for bulk data exchange is not yet
specified, but the nature of the data involved suggests use of a
reliable, adaptable protocol with established and configurable
conventions for authentication and authorization.
2.2. Operational requirements
OP-001 Use of Common Transports: DOTS MUST operate over common As the resilience requirements for the DOTS signal channel mandate
standardized transport protocols. While the protocol resilience small signal message size, a separate, secure data channel
requirement strongly RECOMMENDS the use of connectionless utilizing an established reliable transport protocol MUST be used
protocols, in particular the User Datagram Protocol (UDP) for bulk data exchange.
[RFC0768], use of a standardized, connection-oriented protocol
like the Transmission Control Protocol (TCP) [RFC0793] MAY be
necessary due to network policy or middleware limitations.
OP-002 Peer Mutual Authentication: The client and server MUST 2.2. Operational Requirements
authenticate each other before a DOTS session is considered
active. The method of authentication is not specified, but should
follow current industry best practices with respect to any
cryptographic mechanisms to authenticate the remote peer.
OP-003 Session Health Monitoring: The client and server MUST OP-001 Use of Common Transport Protocols: DOTS MUST operate over
regularly send heartbeats to each other after mutual common widely deployed and standardized transport protocols.
authentication in order to keep the DOTS session open. A session While the User Datagram Protocol (UDP) [RFC0768] SHOULD be used
MUST be considered active until a client or server explicitly ends for the signal channel, the Transmission Control Protocol (TCP)
the session, or either DOTS agent fails to receive heartbeats from [RFC0793] MAY be used if necessary due to network policy or
the other after a mutually negotiated timeout period has elapsed. middlebox capabilities or configurations. The data channel MUST
use TCP; see Section 2.3 below.
OP-004 Mitigation Capability Opacity: DOTS is a threat signaling OP-002 Session Health Monitoring: Peer DOTS agents MUST regularly
protocol. The server and mitigator MUST NOT make any assumption send heartbeats to each other after mutual authentication in order
about the attack detection, classification, or mitigation to keep the DOTS session open. A session MUST be considered
capabilities of the client. While the server and mitigator MAY active until a DOTS agent explicitly ends the session, or either
take hints from any attack telemetry included in client signals, DOTS agent fails to receive heartbeats from the other after a
the server and mitigator cannot depend on the client for mutually negotiated timeout period has elapsed.
authoritative attack classification. Similarly, the mitigator
cannot assume the client can or will mitigate attack traffic on
its own.
The client likewise MUST NOT make any assumptions about the OP-003 Session Redirection: In order to increase DOTS operational
capabilities of the server or mitigator with respect to detection, flexibility and scalability, DOTS servers SHOULD be able to
classification, and mitigation of DDoS attacks. The form of any redirect DOTS clients to another DOTS server or relay at any time.
attack response undertaken by the mitigator is not in scope. Due to the decreased probability of DOTS server signal delivery
due to link congestion, it is RECOMMENDED DOTS servers avoid
redirecting while mitigation is enabled during an active attack
against a target in the DOTS client's domain. Either the DOTS
servers have to fate-share the security state, the client MUST
have separate security state with each potential redirectable
server, or be able to negotiate new state as part of redirection.
OP-005 Mitigation Status: DOTS clients MUST be able to request or OP-004 Mitigation Status: DOTS MUST provide a means to report the
withdraw a request for mitigation from the DOTS server. The DOTS status of an action requested by a DOTS client. In particular,
server MUST acknowledge a DOTS client's request to withdraw from DOTS clients MUST be able to request or withdraw a request for
coordinated attack response in subsequent signals, and MUST cease mitigation from the DOTS server. The DOTS server MUST acknowledge
mitigation activity as quickly as possible. However, a DOTS a DOTS client's request to withdraw from coordinated attack
client rapidly toggling active mitigation may result in response in subsequent signals, and MUST cease mitigation activity
undesirable side-effects for the network path, such as route or as quickly as possible. However, a DOTS client rapidly toggling
DNS flapping. A DOTS server therefore MAY continue mitigating for active mitigation may result in undesirable side-effects for the
a mutually negotiated period after receiving the DOTS client's network path, such as route or DNS [RFC1034] flapping. A DOTS
request to stop. server therefore MAY continue mitigating for a mutually negotiated
period after receiving the DOTS client's request to stop.
A server MAY refuse to engage in coordinated attack response with A server MAY refuse to engage in coordinated attack response with
a client. To make the status of a client's request clear, the a client. To make the status of a client's request clear, the
server MUST indicate in server signals whether client-initiated server MUST indicate in server signals whether client-initiated
mitigation is active. When a client-initiated mitigation is mitigation is active. When a client-initiated mitigation is
active, and threat handling details such as mitigation scope and active, and threat handling details such as mitigation scope and
statistics are available to the server, the server SHOULD include statistics are available to the server, the server SHOULD include
those details in server signals sent to the client. DOTS clients those details in server signals sent to the client. DOTS clients
SHOULD take mitigation statistics into account when deciding SHOULD take mitigation statistics into account when deciding
whether to request the DOTS server cease mitigation. whether to request the DOTS server cease mitigation.
OP-005 Mitigation Lifetime: A DOTS client SHOULD indicate the
desired lifetime of any mitigation requested from the DOTS server.
As DDoS attack duration is unpredictable, the DOTS client SHOULD
be able to extend mitigation lifetime with periodic renewed
requests for help. When the mitigation lifetime comes to an end,
the DOTS server SHOULD delay session termination for a protocol-
defined grace period to allow for delivery of delayed mitigation
renewals over the signal channel. After the grace period elapses,
the DOTS server MAY terminate the session at any time.
If a DOTS client does not include a mitigation lifetime in
requests for help sent to the DOTS server, the DOTS server will
use a reasonable default as defined by the protocol. As above,
the DOTS client MAY extend a current mitigation request's lifetime
trivially with renewed requests for help.
A DOTS client MAY also request an indefinite mitigation lifetime,
enabling architectures in which the mitigator is always in the
traffic path to the resources for which the DOTS client is
requesting protection. DOTS servers MAY refuse such requests for
any reason. The reasons themselves are not in scope.
OP-006 Mitigation Scope: DOTS clients MUST indicate the desired OP-006 Mitigation Scope: DOTS clients MUST indicate the desired
address space coverage of any mitigation, for example by using address or prefix space coverage of any mitigation, for example by
Classless Internet Domain Routing (CIDR) [RFC1518],[RFC1519] using Classless Internet Domain Routing (CIDR) [RFC1518],[RFC1519]
prefixes, [RFC2373] for IPv6 prefixes, the length/prefix prefixes, [RFC2373] for IPv6 [RFC2460] prefixes, the length/prefix
convention established in the Border Gateway Protocol (BGP) convention established in the Border Gateway Protocol (BGP)
[RFC4271], or by a prefix group alias agreed upon with the server [RFC4271], SIP URIs [RFC3261], E.164 numbers, DNS names, or by a
through the data channel. If there is additional information prefix group alias agreed upon with the server through the data
available narrowing the scope of any requested attack response, channel.
such as targeted port range, protocol, or service, clients SHOULD
include that information in client signals. If there is additional information available narrowing the scope
of any requested attack response, such as targeted port range,
protocol, or service, DOTS clients SHOULD include that information
in client signals. DOTS clients MAY also include additional
attack details. Such supplemental information is OPTIONAL, and
DOTS servers MAY ignore it when enabling countermeasures on the
mitigator.
As an active attack evolves, clients MUST be able to adjust as As an active attack evolves, clients MUST be able to adjust as
necessary the scope of requested mitigation by refining the necessary the scope of requested mitigation by refining the
address space requiring intervention. address space requiring intervention.
2.3. Data channel requirements OP-007 Mitigation Efficacy: When a mitigation request by a DOTS
client is active, DOTS clients SHOULD transmit a metric of
perceived mitigation efficacy to the DOTS server, per "Automatic
or Operator-Assisted CPE or PE Mitigators Request Upstream DDoS
Mitigation Services" in [I-D.ietf-dots-use-cases]. DOTS servers
MAY use the efficacy metric to adjust countermeasures activated on
a mitigator on behalf of a DOTS client.
OP-008 Conflict Detection and Notification: Multiple DOTS clients
controlled by a single administrative entity may send conflicting
mitigation requests for pool of protected resources, as a result
of misconfiguration, operator error, or compromised DOTS clients.
DOTS servers attempting to honor conflicting requests may flap
network route or DNS information, degrading the networks
attempting to participate in attack response with the DOTS
clients. DOTS servers SHALL detect such conflicting requests, and
SHALL notify the DOTS clients in conflict. The notification
SHOULD indicate the nature and scope of the conflict, for example,
the overlapping prefix range in a conflicting mitigation request.
OP-009: Lookup Caching: DOTS agents SHOULD cache resolved names, PKI
validation chains, and similarly queried data as necessary.
Network-based lookups and validation may be inhibited or
unavailable during an active attack due to link congestion. For
example, DOTS agents SHOULD cache resolved names and addresses of
peer DOTS agents, and SHOULD refer to those agents by IPv4
[RFC0791] or IPv6 address for all communications following initial
name resolution.
OP-010: Network Address Translator Traversal: The DOTS protocol MUST
operate over networks in which Network Address Translation (NAT)
is deployed. As UDP is the recommended transport for DOTS, all
considerations in "Middlebox Traversal Guidelines" in [RFC5405]
apply to DOTS. Regardless of transport, DOTS protocols MUST
follow established best common practices (BCPs) for NAT traversal.
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, which must operate
nominally even when confronted with despite signal degradation due to nominally even when confronted with despite signal degradation due to
packet loss, the data channel is not expected to be constructed to packet loss, the data channel is not expected to be constructed to
deal with attack conditions. As the primary function of the data deal with attack conditions. As the primary function of the data
channel is data exchange, a reliable transport is required in order channel is data exchange, a reliable transport is required in order
for DOTS agents to detect data delivery success or failure. for DOTS agents to detect data delivery success or failure.
The data channel should be adaptable and extensible. We anticipate The data channel must be extensible. We anticipate the data channel
the data channel will be used for such purposes as configuration or will be used for such purposes as configuration or resource
resource discovery. For example, a DOTS client may submit to the discovery. For example, a DOTS client may submit to the DOTS server
DOTS server a collection of prefixes it wants to refer to by alias a collection of prefixes it wants to refer to by alias when
when requesting mitigation, to which the server would respond with a requesting mitigation, to which the server would respond with a
success status and the new prefix group alias, or an error status and success status and the new prefix group alias, or an error status and
message in the 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 The transactional nature of such data exchanges suggests a separate
set of requirements for the data channel, while the potentially set of requirements for the data channel, while the potentially
sensitive content sent between DOTS agents requires extra precautions sensitive content sent between DOTS agents requires extra precautions
to ensure data privacy and authenticity. to ensure data privacy and authenticity.
DATA-001 Reliable transport: Transmissions over the data channel may DATA-001 Reliable transport: Transmissions over the data channel
be transactional, requiring reliable, in-order packet delivery. MUST be transactional, requiring reliable, in-order packet
delivery.
DATA-002 Data privacy and integrity: Transmissions over the data DATA-002 Data privacy and integrity: Transmissions over the data
channel may contain sensitive information or instructions from the channel is likely to contain operationally or privacy-sensitive
remote DOTS agent. Theft or modification of data channel information or instructions from the remote DOTS agent. Theft or
transmissions could lead to information leaks or malicious modification of data channel transmissions could lead to
transactions on behalf of the sending agent. (See Security information leaks or malicious transactions on behalf of the
Considerations below.) Consequently data sent over the data sending agent (see Section 4 below). Consequently data sent over
channel MUST be encrypted and authenticated using current industry the data channel MUST be encrypted and authenticated using current
best practices. industry best practices. DOTS servers and relays MUST enable
means to prevent leaking operationally or privacy-sensitive data.
DATA-003 Mutual authentication: DOTS agents MUST mutually Although administrative entities participating in DOTS may detail
authenticate each other before data may be exchanged over the data what data may be revealed to third-party DOTS agents, such
channel. DOTS agents MAY take additional steps to authorize data considerations are not in scope for this document.
exchange, as in the prefix group example above, before accepting
data over the data channel. The form of authentication and
authorization is unspecified.
DATA-004 Black- and whitelist management: DOTS servers SHOULD DATA-003 Black- and whitelist management: DOTS servers SHOULD
provide methods for DOTS clients to manage black- and white-lists provide methods for DOTS clients to manage black- and white-lists
of source addresses of traffic destined for addresses belonging to of source addresses of traffic destined for addresses belonging to
a client. 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.
How the DOTS server determines client ownership of address space How the DOTS server determines client ownership of address space
is not in scope. is not in scope.
2.4. Data model requirements 2.4. Security requirements
TODO DOTS must operate within a particularly strict security context, as
an insufficiently protected signal or data channel may be subject to
abuse, enabling or supplementing the very attacks DOTS purports to
mitigate.
SEC-001 Peer Mutual Authentication: DOTS agents MUST authenticate
each other before a DOTS session is considered valid. The method
of authentication is not specified, but should follow current
industry best practices with respect to any cryptographic
mechanisms to authenticate the remote peer.
SEC-002 Message Confidentiality, Integrity and Authenticity: DOTS
protocols MUST take steps to protect the confidentiality,
integrity and authenticity of messages sent between client and
server. While specific transport- and message-level security
options are not specified, the protocols MUST follow current
industry best practices for encryption and message authentication.
In order for DOTS protocols to remain secure despite advancements
in cryptanalysis and traffic analysis, DOTS agents MUST be able to
negotiate the terms and mechanisms of protocol security, subject
to the interoperability and signal message size requirements
above.
SEC-003 Message Replay Protection: In order to prevent a passive
attacker from capturing and replaying old messages, DOTS protocols
MUST provide a method for replay detection.
3. Congestion Control Considerations 3. Congestion Control Considerations
The DOTS signal channel will not contribute measurably to link The DOTS signal channel will not contribute measurably to link
congestion, as the protocol's transmission rate will be negligible congestion, as the protocol's transmission rate will be negligible
regardless of network conditions. Bulk data transfers are performed regardless of network conditions. Bulk data transfers are performed
over the data channel, which should use a reliable transport with over the data channel, which should use a reliable transport with
built-in congestion control mechanisms, such as TCP. built-in congestion control mechanisms, such as TCP.
4. Security Considerations 4. Security Considerations
DOTS is at risk from three primary attacks: DOTS agent impersonation, DOTS is at risk from three primary attacks:
traffic injection, and signaling blocking. The DOTS protocol MUST be
designed for minimal data transfer to address the blocking risk.
Impersonation and traffic injection mitigation can be managed through
current secure communications best practices. DOTS is not subject to
anything new in this area. One consideration could be to minimize
the security technologies in use at any one time. The more needed,
the greater the risk of failures coming from assumptions on one
technology providing protection that it does not in the presence of
another technology.
5. Change Log o DOTS agent impersonation
5.1. 00 revision o Traffic injection
o Signaling blocking
The DOTS protocol MUST be designed for minimal data transfer to
address the blocking risk. Impersonation and traffic injection
mitigation can be managed through current secure communications best
practices. See Section 2.4 above for a detailed discussion.
5. Contributors
Med Boucadair
6. Acknowledgments
Thanks to Roman Danyliw and Matt Richardson for careful reading and
feedback.
7. Change Log
7.1. 01 revision
2016-03-21
o Reconciled terminology with -00 revision of
[I-D.ietf-dots-use-cases].
o Terminology clarification based on working group feedback.
o Moved security-related requirements to separate section.
o Made resilience/robustness primary general requirement to align
with charter.
o Clarified support for unidirectional communication within the
bidirection signal channel.
o Added proposed operational requirement to support session
redirection.
o Added proposed operational requirement to support conflict
notification.
o Added proposed operational requirement to support mitigation
lifetime in mitigation requests.
o Added proposed operational requirement to support mitigation
efficacy reporting from DOTS clients.
o Added proposed operational requirement to cache lookups of all
kinds.
o Added proposed operational requirement regarding NAT traversal.
o Removed redundant mutual authentication requirement from data
channel requirements.
7.2. 00 revision
2015-10-15 2015-10-15
5.2. Initial revision 7.3. Initial revision
2015-09-24 Andrew Mortensen 2015-09-24 Andrew Mortensen
6. References 8. References
6.1. Normative References 8.1. Normative References
[RFC0768] Postel, J., "User Datagram Protocol", STD 6, RFC 768, DOI [RFC0768] Postel, J., "User Datagram Protocol", STD 6, RFC 768, DOI
10.17487/RFC0768, August 1980, 10.17487/RFC0768, August 1980,
<http://www.rfc-editor.org/info/rfc768>. <http://www.rfc-editor.org/info/rfc768>.
[RFC0793] Postel, J., "Transmission Control Protocol", STD 7, RFC [RFC0793] Postel, J., "Transmission Control Protocol", STD 7, RFC
793, DOI 10.17487/RFC0793, September 1981, 793, DOI 10.17487/RFC0793, September 1981,
<http://www.rfc-editor.org/info/rfc793>. <http://www.rfc-editor.org/info/rfc793>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/ Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/
RFC2119, March 1997, RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>. <http://www.rfc-editor.org/info/rfc2119>.
6.2. Informative References [RFC5405] Eggert, L. and G. Fairhurst, "Unicast UDP Usage Guidelines
for Application Designers", BCP 145, RFC 5405, DOI
10.17487/RFC5405, November 2008,
<http://www.rfc-editor.org/info/rfc5405>.
8.2. Informative References
[I-D.ietf-dots-use-cases]
Dobbins, R., Fouant, S., Migault, D., Moskowitz, R.,
Teague, N., and L. Xia, "Use cases for DDoS Open Threat
Signaling", draft-ietf-dots-use-cases-00 (work in
progress), October 2015.
[RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791, DOI
10.17487/RFC0791, September 1981,
<http://www.rfc-editor.org/info/rfc791>.
[RFC1034] Mockapetris, P., "Domain names - concepts and facilities",
STD 13, RFC 1034, DOI 10.17487/RFC1034, November 1987,
<http://www.rfc-editor.org/info/rfc1034>.
[RFC1518] Rekhter, Y. and T. Li, "An Architecture for IP Address [RFC1518] Rekhter, Y. and T. Li, "An Architecture for IP Address
Allocation with CIDR", RFC 1518, DOI 10.17487/RFC1518, Allocation with CIDR", RFC 1518, DOI 10.17487/RFC1518,
September 1993, <http://www.rfc-editor.org/info/rfc1518>. September 1993, <http://www.rfc-editor.org/info/rfc1518>.
[RFC1519] Fuller, V., Li, T., Yu, J., and K. Varadhan, "Classless [RFC1519] Fuller, V., Li, T., Yu, J., and K. Varadhan, "Classless
Inter-Domain Routing (CIDR): an Address Assignment and Inter-Domain Routing (CIDR): an Address Assignment and
Aggregation Strategy", RFC 1519, DOI 10.17487/RFC1519, Aggregation Strategy", RFC 1519, DOI 10.17487/RFC1519,
September 1993, <http://www.rfc-editor.org/info/rfc1519>. September 1993, <http://www.rfc-editor.org/info/rfc1519>.
[RFC2373] Hinden, R. and S. Deering, "IP Version 6 Addressing [RFC2373] Hinden, R. and S. Deering, "IP Version 6 Addressing
Architecture", RFC 2373, DOI 10.17487/RFC2373, July 1998, Architecture", RFC 2373, DOI 10.17487/RFC2373, July 1998,
<http://www.rfc-editor.org/info/rfc2373>. <http://www.rfc-editor.org/info/rfc2373>.
[RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", RFC 2460, DOI 10.17487/RFC2460,
December 1998, <http://www.rfc-editor.org/info/rfc2460>.
[RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
A., Peterson, J., Sparks, R., Handley, M., and E.
Schooler, "SIP: Session Initiation Protocol", RFC 3261,
DOI 10.17487/RFC3261, June 2002,
<http://www.rfc-editor.org/info/rfc3261>.
[RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A [RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A
Border Gateway Protocol 4 (BGP-4)", RFC 4271, DOI Border Gateway Protocol 4 (BGP-4)", RFC 4271, DOI
10.17487/RFC4271, January 2006, 10.17487/RFC4271, January 2006,
<http://www.rfc-editor.org/info/rfc4271>. <http://www.rfc-editor.org/info/rfc4271>.
[RFC4732] Handley, M., Ed., Rescorla, E., Ed., and IAB, "Internet
Denial-of-Service Considerations", RFC 4732, DOI 10.17487/
RFC4732, December 2006,
<http://www.rfc-editor.org/info/rfc4732>.
Authors' Addresses Authors' Addresses
Andrew Mortensen Andrew Mortensen
Arbor Networks, Inc. Arbor Networks, Inc.
2727 S. State St 2727 S. State St
Ann Arbor, MI 48104 Ann Arbor, MI 48104
United States United States
Email: amortensen@arbor.net Email: amortensen@arbor.net
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