One document matched: draft-ietf-dots-requirements-00.xml

<?xml version="1.0" encoding="us-ascii"?>
  <?xml-stylesheet type="text/xsl" href="rfc2629.xslt" ?>
  <!-- generated by https://github.com/cabo/kramdown-rfc2629 version 1.0.28 -->

<!DOCTYPE rfc SYSTEM "rfc2629.dtd" [
<!ENTITY RFC0768 SYSTEM "http://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.0768.xml">
<!ENTITY RFC0793 SYSTEM "http://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.0793.xml">
<!ENTITY RFC2119 SYSTEM "http://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.2119.xml">
<!ENTITY RFC1518 SYSTEM "http://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.1518.xml">
<!ENTITY RFC1519 SYSTEM "http://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.1519.xml">
<!ENTITY RFC2373 SYSTEM "http://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.2373.xml">
<!ENTITY RFC4271 SYSTEM "http://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.4271.xml">
]>

<?rfc toc="yes"?>
<?rfc sortrefs="no"?>
<?rfc symrefs="yes"?>

<rfc docName="draft-ietf-dots-requirements-00" category="info">

  <front>
    <title>DDoS Open Threat Signaling Requirements</title>

    <author initials="A." surname="Mortensen" fullname="Andrew Mortensen">
      <organization>Arbor Networks, Inc.</organization>
      <address>
        <postal>
          <street>2727 S. State St</street>
          <city>Ann Arbor, MI</city>
          <code>48104</code>
          <country>United States</country>
        </postal>
        <email>amortensen@arbor.net</email>
      </address>
    </author>
    <author initials="R." surname="Moskowitz" fullname="Robert Moskowitz">
      <organization>HTT Consulting</organization>
      <address>
        <postal>
          <street></street>
          <city>Oak Park, MI</city>
          <code>42837</code>
          <country>United States</country>
        </postal>
        <email>rgm@htt-consult.com</email>
      </address>
    </author>
    <author initials="T." surname="Reddy" fullname="Tirumaleswar Reddy">
      <organization>Cisco Systems, Inc.</organization>
      <address>
        <postal>
          <street>Cessna Business Park, Varthur Hobli</street> <street>Sarjapur Marathalli Outer Ring Road</street>
          <city>Bangalore, Karnataka</city>
          <code>560103</code>
          <country>India</country>
        </postal>
        <email>tireddy@cisco.com</email>
      </address>
    </author>

    <date year="2015" month="October" day="19"/>

    <area>Security</area>
    <workgroup>DOTS</workgroup>
    <keyword>Internet-Draft</keyword>

    <abstract>


<t>This document defines the requirements for the DDoS Open Threat Signaling
(DOTS) protocols coordinating attack response against Distributed Denial of
Service (DDoS) attacks.</t>



    </abstract>


  </front>

  <middle>


<section anchor="problems" title="Introduction">

<section anchor="overview" title="Overview">
<t>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, thanks to 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.</t>

<t>The higher profile and 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 attack
prevention 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. Each 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 response may be fragmentary or
otherwise incomplete, leaving key players in the attack path unable to assist
in the defense.</t>

<t>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.</t>

<t>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.</t>

<t>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.</t>

<t>Lastly, the protocol must take care to ensure the confidentiality, integrity
and authenticity of messages passed between peers to prevent the protocol from
being repurposed to contribute to the very attacks it’s meant to deflect.</t>

<t>Drawing on the DOTS use cases [I-D.ietf-dots-use-cases] for reference, this
document details the requirements for protocols achieving the DOTS goal of
standards-based open threat signaling.</t>

</section>
<section anchor="terminology" title="Terminology">

<t>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 <xref target="RFC2119"/>.</t>

<t>The following terms are used to define relationships between elements,
the data they exchange, and methods of communication among them:</t>

<t><list style="hanging">
  <t hangText='attack telemetry:'>
  collected network traffic characteristics defining the nature of a DDoS
attack.</t>
  <t hangText='mitigation:'>
  A defensive response against a detected DDoS attack, performed by an entity
in the network path between attack sources 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.</t>
  <t hangText='mitigator:'>
  A network element capable of performing mitigation of a detected DDoS attack.</t>
  <t hangText='DOTS client:'>
  A DOTS-aware network element requesting attack response coordination with
another DOTS-aware element, with the expectation that the remote element is
capable of helping fend off the attack against the client.</t>
  <t hangText='DOTS server:'>
  A DOTS-aware network element handling and responding to messages from a
DOTS client. 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 client. A DOTS server
may also be a mitigator.</t>
  <t hangText='DOTS relay:'>
  A DOTS-aware network element positioned between a DOTS server and a DOTS
client. 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.</t>
  <t hangText='DOTS agents:'>
  A collective term for DOTS clients, servers and relays.</t>
  <t hangText='signal channel:'>
  A bidirectional, mutually authenticated communication layer between DOTS
agents characterized by resilience even in conditions leading to severe
packet loss, such as a volumetric DDoS attack causing network congestion.</t>
  <t hangText='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.</t>
  <t hangText='heartbeat:'>
  A keep-alive message transmitted between DOTS agents over the signal channel,
used to measure peer health. Heartbeat functionality is not required to be
distinct from signal.</t>
  <t hangText='client signal:'>
  A message sent from a DOTS client to a DOTS server over the signal channel,
possibly traversing a DOTS relay, indicating the DOTS client’s need for
mitigation, as well as the scope of any requested mitigation, optionally
including detected attack telemetry to supplement server-initiated
mitigation.</t>
  <t hangText='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 the DOTS client, containing
information about the status of any requested mitigation and its efficacy.</t>
  <t hangText='data channel:'>
  A secure communication layer between client and server used for infrequent
bulk exchange of data not easily or appropriately communicated through the
signal channel under attack conditions.</t>
  <t hangText='blacklist:'>
  a list of source addresses or prefixes from which traffic should be blocked.</t>
  <t hangText='whitelist:'>
  a list of source addresses or prefixes from which traffic should always be
allowed, regardless of contradictory data gleaned in a detected attack.</t>
</list></t>

</section>
</section>
<section anchor="requirements" title="Requirements">

<t>This section describes the required features and characteristics of the DOTS
protocols. The requirements are informed by the use cases described in
[I-D.ietf-dots-use-cases].</t>

<t>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 detected attack,
by signaling inter- or intra-domain using the DOTS protocol. DOTS clients
should similarly be able to withdraw aid requests arbitrarily. Regular feedback
between DOTS client and server supplement the defensive alliance by maintaining
a common understanding of DOTS peer health and activity. Bidirectional
communication between DOTS client and server is therefore critical.</t>

<t>Yet the DOTS protocol 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) with a given network will tend to contribute to the robustness demanded
by a viable DOTS protocol.</t>

<t>On the other hand, DOTS must have adequate message confidentiality, integrity
and authenticity to keep the protocol from becoming another vector for the
very attacks it’s meant to help fight off. The DOTS client must be
authenticated to the DOTS server, 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.</t>

<t>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.</t>

<t>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.</t>

<section anchor="general-requirements" title="General Requirements">

<t><list style="hanging">
  <t hangText='G-001'>
  Interoperability: DOTS’s objective is to develop a standard mechanism for
signaling detected ongoing DDoS attacks. That objective is unattainable
without well-defined specifications for any protocols or data models emerging
from DOTS. All protocols, data models and interfaces MUST be detailed enough
to ensure interoperable implementations.</t>
  <t hangText='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.</t>
  <t hangText='G-003'>
  Resilience: The signaling protocol MUST be designed to maximize the
probability of signal delivery even under the severely constrained network
conditions imposed by the attack traffic. The protocol SHOULD be resilient,
that is, continue operating despite message loss and out-of-order or
redundant signal delivery.</t>
  <t hangText='G-004'>
  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.</t>
  <t hangText='G-005'>
  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 (MTU), including
the byte overhead of any encapsulation, transport headers, and transport- or
message-level security.</t>
  <t hangText='G-006'>
  Message Integrity: 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.</t>
  <t>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.</t>
  <t hangText='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.</t>
  <t hangText='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 white-listed source
addresses; address group aliasing; exchange of incident reports; and other
hinting or configuration supplementing attack response.</t>
  <t>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.</t>
</list></t>

</section>
<section anchor="operational-requirements" title="Operational requirements">

<t><list style="hanging">
  <t hangText='OP-001'>
  Use of Common Transports: DOTS MUST operate over common standardized
transport protocols. While the protocol resilience requirement
strongly RECOMMENDS the use of connectionless protocols, in particular the
User Datagram Protocol (UDP) <xref target="RFC0768"/>, use of a standardized,
connection-oriented protocol like the Transmission Control Protocol (TCP)
<xref target="RFC0793"></xref> MAY be necessary due to network policy or middleware limitations.</t>
  <t hangText='OP-002'>
  Peer Mutual Authentication: The client and server MUST 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.</t>
  <t hangText='OP-003'>
  Session Health Monitoring: The client and server MUST regularly send
heartbeats to each other after mutual authentication in order to keep the
DOTS session open. A session MUST be considered active until a client or
server explicitly ends the session, or either DOTS agent fails to receive
heartbeats from the other after a mutually negotiated timeout period has
elapsed.</t>
  <t hangText='OP-004'>
  Mitigation Capability Opacity: DOTS is a threat signaling protocol. The
server and mitigator MUST NOT make any assumption about the attack detection,
classification, or mitigation capabilities of the client. While the server
and mitigator MAY take hints from any attack telemetry included in client
signals, the server and mitigator cannot depend on the client for
authoritative attack classification. Similarly, the mitigator cannot assume
the client can or will mitigate attack traffic on its own.</t>
  <t>The client likewise MUST NOT make any assumptions about the capabilities of
the server or mitigator with respect to detection, classification, and
mitigation of DDoS attacks. The form of any attack response undertaken by the
mitigator is not in scope.</t>
  <t hangText='OP-005'>
  Mitigation Status: DOTS clients MUST be able to request or withdraw a request
for mitigation from the DOTS server. The DOTS server MUST acknowledge a DOTS
client’s request to withdraw from coordinated attack response in subsequent
signals, and MUST cease mitigation activity as quickly as possible.
However, a DOTS client rapidly toggling active mitigation may result in
undesirable side-effects for the network path, such as route or DNS flapping.
A DOTS server therefore MAY continue mitigating for a mutually negotiated
period after receiving the DOTS client’s request to stop.</t>
  <t>A server MAY refuse to engage in coordinated attack response with a client.
To make the status of a client’s request clear, the server MUST indicate in
server signals whether client-initiated mitigation is active. When a
client-initiated mitigation is active, and threat handling details such as
mitigation scope and statistics are available to the server, the server
SHOULD include those details in server signals sent to the client. DOTS
clients SHOULD take mitigation statistics into account when deciding whether
to request the DOTS server cease mitigation.</t>
  <t hangText='OP-006'>
  Mitigation Scope: DOTS clients MUST indicate the desired address
space coverage of any mitigation, for example by using Classless Internet
Domain Routing (CIDR) <xref target="RFC1518"></xref>,<xref target="RFC1519"></xref> prefixes, <xref target="RFC2373"></xref> for IPv6
prefixes, the length/prefix convention established in the Border Gateway
Protocol (BGP) <xref target="RFC4271"></xref>, or by a prefix group alias agreed upon with the
server through the data channel. If there is additional information available
narrowing the scope of any requested attack response, such as targeted port
range, protocol, or service, clients SHOULD include that information in
client signals.</t>
  <t>As an active attack evolves, clients MUST be able to adjust as necessary the
scope of requested mitigation by refining the address space requiring
intervention.</t>
</list></t>

</section>
<section anchor="data-channel-requirements" title="Data channel requirements">

<t>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 despite 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.</t>

<t>The data channel should be adaptable and 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 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.</t>

<t><list style="hanging">
  <t hangText='DATA-001'>
  Reliable transport: Transmissions over the data channel may be transactional,
requiring reliable, in-order packet delivery.</t>
  <t hangText='DATA-002'>
  Data privacy and integrity: Transmissions over the data channel may contain
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 Security
Considerations below.) Consequently data sent over the data channel MUST be
encrypted and authenticated using current industry best practices.</t>
  <t hangText='DATA-003'>
  Mutual authentication: DOTS agents MUST mutually authenticate each other
before data may be exchanged over the data channel. DOTS agents MAY take
additional steps to authorize data exchange, as in the prefix group example
above, before accepting data over the data channel. The form of
authentication and authorization is unspecified.</t>
  <t hangText='DATA-004'>
  Black- and whitelist management: DOTS servers SHOULD provide methods for
DOTS clients to manage black- and white-lists of source addresses of traffic
destined for addresses belonging to a client.</t>
  <t>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.</t>
  <t>How the DOTS server determines client ownership of address space is not in
scope.</t>
</list></t>

</section>
<section anchor="data-model-requirements" title="Data model requirements">

<t>TODO</t>

</section>
</section>
<section anchor="congestion-control-considerations" title="Congestion Control Considerations">

<t>The DOTS signal channel will not contribute measurably to link congestion, as
the protocol’s transmission rate will be negligible regardless of network
conditions. Bulk data transfers are performed over the data channel, which
should use a reliable transport with built-in congestion control mechanisms,
such as TCP.</t>

</section>
<section anchor="security-considerations" title="Security Considerations">

<t>DOTS is at risk from three primary attacks: DOTS agent impersonation, 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.</t>

</section>
<section anchor="change-log" title="Change Log">

<section anchor="revision" title="00 revision">

<t>2015-10-15</t>

</section>
<section anchor="initial-revision" title="Initial revision">

<t>2015-09-24      Andrew Mortensen</t>

</section>
</section>


  </middle>

  <back>

    <references title='Normative References'>

&RFC0768;
&RFC0793;
&RFC2119;


    </references>

    <references title='Informative References'>

&RFC1518;
&RFC1519;
&RFC2373;
&RFC4271;


    </references>



  </back>
</rfc>