DOTS A. Mortensen
Internet-Draft Arbor Networks, Inc.
Intended status: Informational R. Moskowitz
Expires: September 14, 2017 HTT Consulting
T. Reddy
Cisco Systems, Inc.
March 13, 2017
Distributed Denial of Service (DDoS) Open Threat Signaling Requirements
draft-ietf-dots-requirements-04
Abstract
This document defines the requirements for the Distributed Denial of
Service (DDoS) Open Threat Signaling (DOTS) protocols coordinating
attack response against DDoS attacks.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on September 14, 2017.
Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
Mortensen, et al. Expires September 14, 2017 [Page 1]
Internet-Draft DOTS Requirements March 2017
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Context and Motivation . . . . . . . . . . . . . . . . . 2
1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
2. Requirements . . . . . . . . . . . . . . . . . . . . . . . . 5
2.1. General Requirements . . . . . . . . . . . . . . . . . . 7
2.2. Operational Requirements . . . . . . . . . . . . . . . . 8
2.3. Data Channel Requirements . . . . . . . . . . . . . . . . 11
2.4. Security requirements . . . . . . . . . . . . . . . . . . 12
2.5. Data Model Requirements . . . . . . . . . . . . . . . . . 13
3. Congestion Control Considerations . . . . . . . . . . . . . . 14
3.1. Signal Channel . . . . . . . . . . . . . . . . . . . . . 14
3.2. Data Channel . . . . . . . . . . . . . . . . . . . . . . 15
4. Security Considerations . . . . . . . . . . . . . . . . . . . 15
5. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 15
6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 16
7. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . 16
7.1. 04 revision . . . . . . . . . . . . . . . . . . . . . . . 16
7.2. 03 revision . . . . . . . . . . . . . . . . . . . . . . . 16
7.3. 02 revision . . . . . . . . . . . . . . . . . . . . . . . 16
7.4. 01 revision . . . . . . . . . . . . . . . . . . . . . . . 16
7.5. 00 revision . . . . . . . . . . . . . . . . . . . . . . . 17
7.6. Initial revision . . . . . . . . . . . . . . . . . . . . 17
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 17
8.1. Normative References . . . . . . . . . . . . . . . . . . 17
8.2. Informative References . . . . . . . . . . . . . . . . . 19
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 19
1. Introduction
1.1. Context and Motivation
Distributed Denial of Service (DDoS) attacks continue to plague
networks around the globe, from Tier-1 service providers on down to
enterprises and small businesses. Attack scale and frequency
similarly have continued to increase, in part as a result of software
vulnerabilities leading to reflection and amplification attacks.
Once-staggering attack traffic volume is now the norm, 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
focus on coordinated attack response. Many institutions and
enterprises lack the resources or expertise to operate on-premise
Mortensen, et al. Expires September 14, 2017 [Page 2]
Internet-Draft DOTS Requirements March 2017
attack mitigation solutions themselves, or simply find themselves
constrained by local bandwidth limitations. To address such gaps,
security service providers have begun to offer on-demand traffic
scrubbing services, which aim to separate the DDoS traffic from
legitimate traffic and forward only the latter. Today each such
service offers its own interface for subscribers to request attack
mitigation, tying subscribers to proprietary implementations while
also limiting the subset of network elements capable of participating
in the attack response. As a result of incompatibility across
services, attack responses may be fragmentary or otherwise
incomplete, leaving key players in the attack path unable to assist
in the defense.
The lack of a common method to coordinate a real-time response among
involved actors and network domains inhibits the speed and
effectiveness of DDoS attack mitigation. This document describes the
required characteristics of a DOTS protocol enabling requests for
DDoS attack mitigation, reducing attack impact and leading to more
efficient defensive strategies.
DOTS communicates the need for defensive action in anticipation of or
in response to an attack, but does not dictate the form any defensive
action takes. DOTS supplements calls for 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 and
[I-D.ietf-dots-architecture].
1.2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
This document adopts the following terms:
DDoS: A distributed denial-of-service attack, in which traffic
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].
DDoS attack target: A network connected entity with a finite set of
resources, such as network bandwidth, memory or CPU, that is the
focus of a DDoS attack. Potential targets include network
elements, network links, servers, and services.
Mortensen, et al. Expires September 14, 2017 [Page 3]
Internet-Draft DOTS Requirements March 2017
DDoS attack telemetry: Collected measurements and behavioral
characteristics defining the nature of a DDoS attack.
Countermeasure: An action or set of actions taken to recognize and
filter out DDoS attack traffic while passing legitimate traffic to
the attack target.
Mitigation: A set of countermeasures enforced against traffic
destined for the target or targets of a detected or reported DDoS
attack, where countermeasure enforcement is managed by an entity
in the network path between attack sources and the attack target.
Mitigation methodology is out of scope for this document.
Mitigator: An entity, typically a network element, capable of
performing mitigation of a detected or reported DDoS attack. For
the purposes of this document, this entity is a black box capable
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 client: A DOTS-aware software module responsible for requesting
attack response coordination with other DOTS-aware elements.
DOTS server: A DOTS-aware software module handling and responding to
messages from DOTS clients. The DOTS server SHOULD enable
mitigation on behalf of the DOTS client, if requested, by
communicating the DOTS client's request to the mitigator and
returning selected mitigator feedback to the requesting DOTS
client. A DOTS server MAY also be a mitigator.
DOTS agent: Any DOTS-aware software module capable of participating
in a DOTS signaling session.
DOTS gateway: A logical DOTS agent resulting from the logical
concatenation of a DOTS server and a DOTS client, analogous to a
SIP Back-to-Back User Agent (B2BUA) [RFC3261]. DOTS gateways are
discussed in detail in [I-D.ietf-dots-architecture].
Signal channel: A bidirectional, mutually authenticated
communication channel between DOTS agents characterized by
resilience even in conditions leading to severe packet loss, such
as a volumetric DDoS attack causing network congestion.
DOTS signal: A concise authenticated status/control message
transmitted between DOTS agents, used to indicate client's need
for mitigation, as well as to convey the status of any requested
mitigation.
Mortensen, et al. Expires September 14, 2017 [Page 4]
Internet-Draft DOTS Requirements March 2017
Heartbeat: A message transmitted between DOTS agents over the signal
channel, used as a keep-alive and to measure peer health.
Client signal: A message sent from a DOTS client to a DOTS server
over the signal channel, indicating the DOTS client's need for
mitigation, as well as the scope of any requested mitigation,
optionally including additional attack details to supplement
server-initiated mitigation.
Server signal: A message sent from a DOTS server to a DOTS client
over the signal channel. Note that a server signal is not a
response to client signal, but a DOTS server-initiated status
message sent to DOTS clients with which the server has established
signaling sessions.
Data channel: A secure communication layer between DOTS clients and
DOTS servers used for infrequent bulk exchange of data not easily
or appropriately communicated through the signal channel under
attack conditions.
Filter: A policy matching a network traffic flow or set of flows and
rate-limiting or discarding matching traffic.
Blacklist: A filter list of addresses, prefixes and/or other
identifiers indicating sources from which traffic should be
blocked, regardless of traffic content.
Whitelist: A list of addresses, prefixes and/or other identifiers
from indicating sources from which traffic should 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
This section describes the required features and characteristics of
the DOTS protocol.
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 normal
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.
Mortensen, et al. Expires September 14, 2017 [Page 5]
Internet-Draft DOTS Requirements March 2017
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
suspected attack, signaling within or between domains as requested by
local operators. DOTS clients should similarly be able to withdraw
aid requests. DOTS requires no justification from DOTS clients for
requests for help, nor do DOTS clients need to justify withdrawing
help requests: the decision is local to the DOTS clients' domain.
Regular feedback between DOTS clients and DOTS server supplement the
defensive alliance by maintaining a common understanding of DOTS peer
health and activity. Bidirectional communication between DOTS
clients and DOTS servers is therefore critical.
Yet DOTS must also work with a set of competing operational goals.
On the one hand, the protocol must be resilient under extremely
hostile network conditions, providing continued contact between DOTS
agents even as attack traffic saturates the link. Such resiliency
may be developed several ways, but characteristics such as small
message size, asynchronous, redundant message delivery and minimal
connection overhead (when possible given local network policy) will
tend to contribute to the robustness demanded by a 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 requires no such policies
be in place. The DOTS solution indeed must be viable especially in
their absence.
On the other hand, DOTS must include protections ensuring message
confidentiality, integrity and authenticity to keep the protocol from
becoming another vector for the very attacks it's meant to help fight
off. DOTS clients must be able to authenticate DOTS servers, and
vice versa, for DOTS to operate safely, meaning the 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 the mitigator, as
well as making adjustments to other commonly configurable features,
such as listen ports, exchanging black- and white-lists, and so on.
Finally, DOTS should provide sufficient extensibility to meet local,
vendor or future needs in coordinated attack defense, although this
consideration is necessarily superseded by the other operational
requirements.
Mortensen, et al. Expires September 14, 2017 [Page 6]
Internet-Draft DOTS Requirements March 2017
2.1. General Requirements
GEN-001 Extensibility: Protocols and data models developed as part
of DOTS MUST be extensible in order to keep DOTS adaptable to
operational and proprietary DDoS defenses. Future extensions MUST
be backward compatible.
GEN-002 Resilience and Robustness: The signaling protocol MUST be
designed to maximize the probability of signal delivery even under
the severely constrained network conditions imposed by particular
attack traffic. The protocol MUST be resilient, that is, continue
operating despite message loss and out-of-order or redundant
message delivery. In support signaling protocol robustness, DOTS
signals SHOULD be conveyed over a transport not susceptible to
Head of Line Blocking.
GEN-003 Bidirectionality: To support peer health detection, to
maintain an open signal channel, and to increase the probability
of signal delivery during attack, the signal channel MUST be
bidirectional, with client and server transmitting signals to each
other at regular intervals, regardless of any client request for
mitigation. Unidirectional messages MUST be supported within the
bidirectional signal channel to allow for unsolicited message
delivery, enabling asynchronous notifications between agents.
GEN-004 Sub-MTU Message Size: To avoid message fragmentation and the
consequently decreased probability of message delivery, signaling
protocol message size MUST be kept under signaling Path Maximum
Transmission Unit (PMTU), including the byte overhead of any
encapsulation, transport headers, and transport- or message-level
security.
DOTS agents SHOULD attempt to learn the PMTU through mechanisms
such as Path MTU Discovery [RFC1191] or Packetization Layer Path
MTU Discovery [RFC4821]. If the PMTU cannot be discovered, DOTS
agents SHOULD assume a PMTU of 1280 bytes. If IPv4 support on
legacy or otherwise unusual networks is a consideration and PMTU
is unknown, DOTS implementations MAY rely on a PMTU of 576 bytes,
as discussed in [RFC0791] and [RFC1122].
GEN-005 Bulk Data Exchange: Infrequent bulk data exchange between
DOTS agents can also significantly augment attack response
coordination, permitting such tasks as population of black- or
white-listed source addresses; address or prefix group aliasing;
exchange of incident reports; and other hinting or configuration
supplementing attack response.
Mortensen, et al. Expires September 14, 2017 [Page 7]
Internet-Draft DOTS Requirements March 2017
As the resilience requirements for the DOTS signal channel mandate
small signal message size, a separate, secure data channel
utilizing a reliable transport protocol MUST be used for bulk data
exchange.
2.2. Operational Requirements
OP-001 Use of Common Transport Protocols: DOTS MUST operate over
common widely deployed and standardized transport protocols.
While the User Datagram Protocol (UDP) [RFC0768] SHOULD be used
for the signal channel, the Transmission Control Protocol (TCP)
[RFC0793] MAY be used if necessary due to network policy or
middlebox capabilities or configurations. The data channel MUST
use a reliable transport; see Section 2.3 below.
OP-002 Session Health Monitoring: Peer DOTS agents MUST regularly
send heartbeats to each other after mutual authentication in order
to keep the DOTS session active. A session MUST be considered
active until a DOTS agent explicitly ends the session, or either
DOTS agent fails to receive heartbeats from the other after a
mutually agreed upon timeout period has elapsed.
OP-003 Session Redirection: In order to increase DOTS operational
flexibility and scalability, DOTS servers SHOULD be able to
redirect DOTS clients to another DOTS server at any time. DOTS
clients MUST NOT assume the redirection target DOTS server shares
security state with the redirecting DOTS server. DOTS clients MAY
attempt abbreviated security negotiation methods supported by the
protocol, such as DTLS session resumption, but MUST be prepared to
negotiate new security state with the redirection target DOTS
server.
Due to the increased likelihood of packet loss caused by link
congestion during an attack, it is RECOMMENDED DOTS servers avoid
redirecting while mitigation is enabled during an active attack
against a target in the DOTS client's domain.
OP-004 Mitigation Requests and Status: Authorized DOTS clients MUST
be able to request scoped mitigation from DOTS servers. DOTS
servers MUST send mitigation request status in response to DOTS
clients requests for mitigation, and SHOULD accept scoped
mitigation requests from authorized DOTS clients. DOTS servers
MAY reject authorized requests for mitigation, but MUST include a
reason for the rejection in the status message sent to the client.
Due to the higher likelihood of packet loss during a DDoS attack,
DOTS servers SHOULD regularly send mitigation status to authorized
Mortensen, et al. Expires September 14, 2017 [Page 8]
Internet-Draft DOTS Requirements March 2017
DOTS clients which have requested and been granted mitigation,
regardless of client requests for mitigation status.
When DOTS client-requested mitigation is active, DOTS server
status messages SHOULD include the following mitigation metrics:
* Total number of packets blocked by the mitigation
* Current number of packets per second blocked
* Total number of bytes blocked
* Current number of bytes per second blocked
DOTS clients SHOULD take these metrics into account when
determining whether to ask the DOTS server to cease mitigation.
Once a DOTS client requests mitigation, the client MAY withdraw
that request at any time, regardless of whether mitigation is
currently active. The DOTS server MUST immediately acknowledge a
DOTS client's request to stop mitigation.
To protect against route or DNS flapping caused by a client
rapidly toggling mitigation, and to dampen the effect of
oscillating attacks, DOTS servers MAY continue mitigation for a
period of up to five minutes after acknowledging a DOTS client's
withdrawal of a mitigation request. During this period, DOTS
server status messages SHOULD indicate that mitigation is active
but terminating. After the five-minute period elapses, the DOTS
server MUST treat the mitigation as terminated, as the DOTS client
is no longer responsible for the mitigation. For example, if
there is a financial relationship between the DOTS client and
server domains, the DOTS client ceases incurring cost at this
point.
OP-005 Mitigation Lifetime: DOTS servers MUST support mitigation
lifetimes, and MUST terminate a mitigation when the lifetime
elapses. DOTS servers also MUST support renewal of mitigation
lifetimes in mitigation requests from DOTS clients, allowing
clients to extend mitigation as necessary for the duration of an
attack.
DOTS servers MUST treat a mitigation terminated due to lifetime
expiration exactly as if the DOTS client originating the
mitigation had asked to end the mitigation, including the five-
minute termination period, as described above in OP-004.
Mortensen, et al. Expires September 14, 2017 [Page 9]
Internet-Draft DOTS Requirements March 2017
DOTS clients SHOULD include a mitigation lifetime in all
mitigation requests. 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.
DOTS servers SHOULD support indefinite mitigation lifetimes,
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 mitigations with
indefinite lifetimes, for policy reasons. The reasons themselves
are out of scope for this document, but MUST be included in the
mitigation rejection message from the server, per OP-004.
OP-006 Mitigation Scope: DOTS clients MUST indicate desired
mitigation scope. The scope type will vary depending on the
resources requiring mitigation. All DOTS agent implementations
MUST support the following required scope types:
* IPv4 addresses in dotted quad format
* IPv4 address prefixes in CIDR notation [RFC4632]
* IPv6 addresses [RFC2373]
* IPv6 address prefixes [RFC2373]
* Domain names [RFC1035]
The following mitigation scope types are OPTIONAL:
* Uniform Resource Identifiers [RFC3986]
DOTS agents MUST support mitigation scope aliases, allowing DOTS
client and server to refer to collections of protected resources
by an opaque identifier created through the data channel, direct
configuration, or other means.
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.
Mortensen, et al. Expires September 14, 2017 [Page 10]
Internet-Draft DOTS Requirements March 2017
As an active attack evolves, clients MUST be able to adjust as
necessary the scope of requested mitigation by refining the scope
of resources requiring mitigation.
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: 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 the DOTS
signal channel, 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
between DOTS agents. Unlike the signal channel, which must operate
nominally even when confronted with signal degradation due to packet
loss, the data channel is not expected to be constructed to deal with
attack conditions. As the primary function of the data channel is
data exchange, a reliable transport is required in order for DOTS
agents to detect data delivery success or failure.
The data channel must be extensible. We anticipate the data channel
will be used for such purposes as configuration or resource
discovery. For example, a DOTS client may submit to the DOTS server
a collection of prefixes it wants to refer to by alias when
requesting mitigation, to which the server would respond with a
success status and the new prefix group alias, or an error status and
Mortensen, et al. Expires September 14, 2017 [Page 11]
Internet-Draft DOTS Requirements March 2017
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
MUST be delivered reliably, in order sent.
DATA-002 Data privacy and integrity: Transmissions over the data
channel are likely to contain operationally or privacy-sensitive
information or instructions from the remote DOTS agent. Theft or
modification of data channel transmissions could lead to
information leaks or malicious transactions on behalf of the
sending agent (see Section 4 below). Consequently data sent over
the data channel MUST be encrypted and authenticated using current
industry best practices. DOTS servers MUST enable means to
prevent leaking operationally or privacy-sensitive data. Although
administrative entities participating in DOTS may detail what data
may be revealed to third-party DOTS agents, such considerations
are not in scope for this document.
DATA-003 Resource Configuration: To help meet the general and
operational requirements in this document, DOTS server
implementations MUST provide an interface to configure resource
identifiers, as described in OP-007. DOTS server implementations
MAY expose additional configurability. Additional configurability
is implementation-specific.
DATA-004 Black- and whitelist management: DOTS servers SHOULD
provide methods for DOTS clients to manage black- and white-lists
of traffic destined for resources belonging to a client.
For example, a DOTS client should be able to create a black- or
whitelist entry; retrieve a list of current entries from either
list; update the content of either list; and delete entries as
necessary.
How the DOTS server determines client ownership of address space
is not in scope.
2.4. Security requirements
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.
Mortensen, et al. Expires September 14, 2017 [Page 12]
Internet-Draft DOTS Requirements March 2017
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.
While the interfaces between downstream DOTS server and upstream
DOTS client within a DOTS gateway are implementation-specific,
those interfaces nevertheless MUST provide security equivalent to
that of the signaling sessions bridged by gateways in the
signaling path. For example, when a DOTS gateway consisting of a
DOTS server and DOTS client is running on the same logical device,
they must be within the same process security boundary.
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.
2.5. Data Model Requirements
The value of DOTS is in standardizing a mechanism to permit elements,
networks or domains under or under threat of DDoS attack to request
aid mitigating the effects of any such attack. A well-structured
DOTS data model is therefore critical to the development of a
successful 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
collections of hierarchical modules and sub-modules. If the data
model structure is split across modules, those distinct modules
MUST allow references to describe the overall data model's
structural dependencies.
DM-002: Versioning: To ensure interoperability between DOTS protocol
implementations, data models MUST be versioned. The version
Mortensen, et al. Expires September 14, 2017 [Page 13]
Internet-Draft DOTS Requirements March 2017
number of the initial data model SHALL be 1. Each published
change to the initial published DOTS data model SHALL increment
the data model version by 1.
How the protocol represents data model versions is not defined in
this document.
DM-003: Mitigation Status Representation: The data model MUST
provide the ability to represent a request for mitigation and the
withdrawal of such a request. The data model MUST also support a
representation of currently requested mitigation status, including
failures and their causes.
DM-004: Mitigation Scope Representation: The data model MUST support
representation of a requested mitigation's scope. As mitigation
scope may be represented in several different ways, per OP-006
above, the data model MUST be capable of flexible representation
of mitigation scope.
DM-005: Mitigation Lifetime Representation: The data model MUST
support representation of a mitigation request's lifetime,
including mitigations with no specified end time.
DM-006: Mitigation Efficacy Representation: The data model MUST
support representation of a DOTS client's understanding of the
efficacy of a mitigation enabled through a mitigation request.
DM-007: Acceptable Signal Loss Representation: The data model MUST
be able to represent the DOTS agent's preference for acceptable
signal loss when establishing a signaling session, as described in
GEN-002.
DM-008: Heartbeat Interval Representation: The data model MUST be
able to represent the DOTS agent's preferred heartbeat interval,
which the client may include when establishing the signal channel,
as described in OP-002.
DM-009: Relationship to Transport: The DOTS data model MUST NOT
depend on the specifics of any transport to represent fields in
the model.
3. Congestion Control Considerations
3.1. Signal Channel
As part of a protocol expected to operate over links affected by DDoS
attack traffic, the DOTS signal channel MUST NOT contribute
significantly to link congestion. To meet the operational
Mortensen, et al. Expires September 14, 2017 [Page 14]
Internet-Draft DOTS Requirements March 2017
requirements above, DOTS signal channel implementations MUST support
UDP. However, UDP when deployed naively can be a source of network
congestion, as discussed in [RFC5405]. Signal channel
implementations using UDP MUST therefore include a congestion control
mechanism.
Signal channel implementations using TCP may rely on built-in TCP
congestion control support.
3.2. Data Channel
As specified in DATA-001, the data channel requires reliable, in-
order message delivery. Data channel implementations using TCP may
rely on the TCP implementation's built-in congestion control
mechanisms.
4. Security Considerations
DOTS is at risk from three primary attacks:
o DOTS agent impersonation
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
Mohamed Boucadair
Orange
mohamed.boucadair@orange.com
Flemming Andreasen
Cisco Systems, Inc.
fandreas@cisco.com
Dave Dolson
Sandvine
ddolson@sandvine.com
Mortensen, et al. Expires September 14, 2017 [Page 15]
Internet-Draft DOTS Requirements March 2017
6. Acknowledgments
Thanks to Roman Danyliw and Matt Richardson for careful reading and
feedback.
7. Change Log
7.1. 04 revision
2017-03-13
o Establish required and optional mitigation scope types
o Specify message size for DOTS signal channel
o Recast mitigation lifetime as a DOTS server requirement
o Clarify DOTS server's responsibilities after client request to end
mitigation
o Specify security state handling on redirection
o Signal channel should use transport not susceptible to HOL
blocking
o Expanded list of DDoS types to include network links
7.2. 03 revision
2016-10-30
o Extended SEC-003 to require secure interfaces within DOTS
gateways.
o Changed DATA-003 to Resource Configuration, delegating control of
acceptable signal loss, heartbeat intervals, and mitigation
lifetime to DOTS client.
o Added data model requirements reflecting client control over the
above.
7.3. 02 revision
7.4. 01 revision
2016-03-21
Mortensen, et al. Expires September 14, 2017 [Page 16]
Internet-Draft DOTS Requirements March 2017
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
bidirectional 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.
7.5. 00 revision
2015-10-15
7.6. Initial revision
2015-09-24 Andrew Mortensen
8. References
8.1. Normative References
[RFC0768] Postel, J., "User Datagram Protocol", STD 6, RFC 768,
DOI 10.17487/RFC0768, August 1980,
<http://www.rfc-editor.org/info/rfc768>.
Mortensen, et al. Expires September 14, 2017 [Page 17]
Internet-Draft DOTS Requirements March 2017
[RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791,
DOI 10.17487/RFC0791, September 1981,
<http://www.rfc-editor.org/info/rfc791>.
[RFC0793] Postel, J., "Transmission Control Protocol", STD 7,
RFC 793, DOI 10.17487/RFC0793, September 1981,
<http://www.rfc-editor.org/info/rfc793>.
[RFC1035] Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, DOI 10.17487/RFC1035,
November 1987, <http://www.rfc-editor.org/info/rfc1035>.
[RFC1122] Braden, R., Ed., "Requirements for Internet Hosts -
Communication Layers", STD 3, RFC 1122,
DOI 10.17487/RFC1122, October 1989,
<http://www.rfc-editor.org/info/rfc1122>.
[RFC1191] Mogul, J. and S. Deering, "Path MTU discovery", RFC 1191,
DOI 10.17487/RFC1191, November 1990,
<http://www.rfc-editor.org/info/rfc1191>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC2373] Hinden, R. and S. Deering, "IP Version 6 Addressing
Architecture", RFC 2373, DOI 10.17487/RFC2373, July 1998,
<http://www.rfc-editor.org/info/rfc2373>.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, DOI 10.17487/RFC3986, January 2005,
<http://www.rfc-editor.org/info/rfc3986>.
[RFC4632] Fuller, V. and T. Li, "Classless Inter-domain Routing
(CIDR): The Internet Address Assignment and Aggregation
Plan", BCP 122, RFC 4632, DOI 10.17487/RFC4632, August
2006, <http://www.rfc-editor.org/info/rfc4632>.
[RFC4821] Mathis, M. and J. Heffner, "Packetization Layer Path MTU
Discovery", RFC 4821, DOI 10.17487/RFC4821, March 2007,
<http://www.rfc-editor.org/info/rfc4821>.
[RFC5405] Eggert, L. and G. Fairhurst, "Unicast UDP Usage Guidelines
for Application Designers", RFC 5405,
DOI 10.17487/RFC5405, November 2008,
<http://www.rfc-editor.org/info/rfc5405>.
Mortensen, et al. Expires September 14, 2017 [Page 18]
Internet-Draft DOTS Requirements March 2017
8.2. Informative References
[I-D.ietf-dots-architecture]
Mortensen, A., Andreasen, F., Reddy, T.,
christopher_gray3@cable.comcast.com, c., Compton, R., and
N. Teague, "Distributed-Denial-of-Service Open Threat
Signaling (DOTS) Architecture", draft-ietf-dots-
architecture-01 (work in progress), October 2016.
[I-D.ietf-dots-use-cases]
Dobbins, R., Fouant, S., Migault, D., Moskowitz, R.,
Teague, N., Xia, L., and K. Nishizuka, "Use cases for DDoS
Open Threat Signaling", draft-ietf-dots-use-cases-03 (work
in progress), November 2016.
[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>.
[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
Andrew Mortensen
Arbor Networks, Inc.
2727 S. State St
Ann Arbor, MI 48104
United States
Email: amortensen@arbor.net
Robert Moskowitz
HTT Consulting
Oak Park, MI 42837
United States
Email: rgm@htt-consult.com
Mortensen, et al. Expires September 14, 2017 [Page 19]
Internet-Draft DOTS Requirements March 2017
Tirumaleswar Reddy
Cisco Systems, Inc.
Cessna Business Park, Varthur Hobli
Sarjapur Marathalli Outer Ring Road
Bangalore, Karnataka 560103
India
Email: tireddy@cisco.com
Mortensen, et al. Expires September 14, 2017 [Page 20]