One document matched: draft-ietf-atoca-requirements-01.xml
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<front>
<title abbrev="Exigent Communications">Requirements, Terminology and Framework for Exigent
Communications</title>
<author initials="H." surname="Schulzrinne" fullname="Henning Schulzrinne">
<organization>Columbia University</organization>
<address>
<postal>
<street>Department of Computer Science</street>
<street>450 Computer Science Building</street>
<city>New York</city>
<region>NY</region>
<code>10027</code>
<country>US</country>
</postal>
<phone>+1 212 939 7004</phone>
<email>hgs+ecrit@cs.columbia.edu</email>
<uri>http://www.cs.columbia.edu</uri>
</address>
</author>
<author fullname="Steve Norreys" initials="S." surname="Norreys">
<organization>BT Group</organization>
<address>
<postal>
<street>1 London Road</street>
<city>Brentwood</city>
<region>Essex</region>
<code>CM14 4QP</code>
<country>UK</country>
</postal>
<phone>+44 1277 32 32 20</phone>
<email>steve.norreys@bt.com</email>
</address>
</author>
<author initials="B." surname="Rosen" fullname="Brian Rosen">
<organization>NeuStar, Inc. </organization>
<address>
<postal>
<street>470 Conrad Dr</street>
<city>Mars</city>
<region> PA </region>
<code>16046 </code>
<country>US </country>
</postal>
<phone> </phone>
<email>br@brianrosen.net
</email>
</address>
</author>
<author initials="H." surname="Tschofenig" fullname="Hannes Tschhofenig">
<organization>Nokia Siemens Networks</organization>
<address>
<postal>
<street>Linnoitustie 6</street>
<city>Espoo</city>
<code>02600</code>
<country>Finland</country>
</postal>
<phone>+358 (50) 4871445</phone>
<email>Hannes.Tschofenig@gmx.net</email>
<uri>http://www.tschofenig.priv.at</uri>
</address>
</author>
<date year="2011"/>
<area>RAI</area>
<workgroup>ATOCA</workgroup>
<keyword>I-D</keyword>
<keyword>Internet-Draft</keyword>
<keyword>Emergency</keyword>
<keyword>Early Warning</keyword>
<keyword>Exigent Communications</keyword>
<abstract>
<t>Before, during and after emergency situations various agencies need to provide information to a group of persons or to
the public within a geographical area. While many aspects of such
systems are specific to national or local jurisdictions, emergencies span such boundaries
and notifications need to reach visitors from other jurisdictions.</t>
<t>This document provides
terminology, requirements and an architectural description for protocols exchanging alerts between IP-based end points.</t>
</abstract>
</front>
<middle>
<section title="Introduction" toc="default">
<section title="Classical Early Warning Situations">
<t> During large-scale emergencies, public safety authorities need to reliably communicate
with citizens in the affected areas, to provide warnings, indicate whether citizens should
evacuate and how, and to dispel misinformation. Accurate information can reduce the impact
of such emergencies. </t>
<t> Traditionally, emergency alerting has used church bells, sirens, loudspeakers, radio and
television to warn citizens and to provide information. However, techniques, such as
sirens and bells, provide limited information content; loud speakers cover only very small
areas and are often hard to understand, even for those not hearing impaired or fluent in
the local language. Radio and television offer larger information volume, but are hard to
target geographically and do not work well to address the “walking wounded” or other
pedestrians. Both are not suitable for warnings, as many of those needing the information
will not be listening or watching at any given time, particularly during work/school and
sleep hours. </t>
<t> This problem has been illustrated by the London underground bombing on July 7, 2006, as
described in a government report <xref target="July2005"/>. The UK authorities could only
use broadcast media and could not, for example, easily announce to the "walking wounded"
where to assemble. </t>
</section>
<section title="Exigent Communications">
<t>With the usage of the term 'Exigent Communications' this document aims to generalize the
concept of conveying alerts to IP-based systems and at the same time to re-define the
actors that participate in the messaging communication. More precisely, exigent
communications is defined as: </t>
<t>
<list style="empty">
<t> Communication that requirs immediate action or remedy. Information about the reason
for action and details about the steps that have to be taken are provided in the alert
message.<vspace blankLines="1"/>
</t>
<t>An alert message (or warning message) is a cautionary advice about something imminent
(especially imminent danger or other unpleasantness). In the context of exigent
communication such an alert message refers to a future, ongoing or past event as the
signaling exchange itself may relate to different stages of the lifecycle of the
event. The alert message itself, and not the signaling protocol that convey it, provides sufficient
context about the specific state of the lifecycle the alert message refers to.</t>
</list>
</t>
<t>Communication typically occurs in two phases:</t>
<t>
<list style="hanging">
<t hangText="Subscription:"> In this step Recipients express their interest to receive certain types of alerts and happens prior to the actual delivery of the alert. This expression of interest may be in form of an explicit communication step by having the Receiver sending a subscription message potentially with an indication of the type of alerts they are interested in, the duration of the subscription and a number of other indicators. For example, parents may want to be alerted of emergencies
affecting the school attended by their children and adult children may need to know
about emergencies affecting elderly parents. The subscription step may, however, also happen outside the Internet communication infrastructure but rather by the Recipient signing a contract and thereby agreeing to receive certain alerts. Additionally, certain subscriptions may happen without the Recipient's explicit consent and without the Receiver sending a subscription. For example, a Tsunami flood alert may be delievered to Recipients in case they are located in a specific geographical area.<vspace blankLines="1"/>
It is important to note that a protocol interaction initiated by the Receiver may need to take place to subscribe to certain types of alerts.
In some other cases the subscription does not require such interaction from the Receiver. Orthogonal to the need to have a protocol interaction is the question of opt-in vs. opt-out. This is a pure policy decision and largely outside the scope of a technical specification. <vspace blankLines="1"/>
</t>
<t hangText="Alert Delivery">In this step the alert message is distributed to one or multiple Receivers. The Receiver as a software module then presents the alert message to the Receipient. The alert encoding is accomplished via the Common Alerting Protocol (CAP) and such an alert message contains useful information needed for dealing with the imminent danger.</t>
</list>
</t>
<t>
Note that alert Receivers as software modules may not necessarily only be executed on end devices humans typically carry around, such as
mobile phones, Internet tablets, or laptops. Instead, alert distribution may well directly communicate with
displays in subway stations, or electronic bill boards. When a Receiver obtains such an alert then it may not necessarily
need to interact with a human (as the Recipient) but may instead use the alert as input to another process
to trigger automated behaviors, such as closing vents during a chemical
spill or activating sirens or other warning systems in commercial buildings.
</t>
<t>This document provides
terminology, requirements and an architectural description. Note that the requirements focus on the communication protocols for subscription and alert delivery rather than on the content of the alert message itself. With the usage of CAP these alert message content requirements are delegated to the authors and originators of alerts.</t>
</section>
</section>
<!-- ////////////////////////////////////////////////////////////////////////////////// -->
<section anchor="terminology" title="Terminology">
<t>The keywords "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"/>, with the important qualification that, unless otherwise stated,
these terms apply to the design of a protocol conveying warning messages, not its
implementation or application. </t>
</section>
<!-- ////////////////////////////////////////////////////////////////////////////////// -->
<section title="Alert Delivery Architecture">
<t>This section illustrates the roles useful for alert delivery.</t>
<section title="Responsible Actor Roles">
<t>The communication system used for the dissemination of alert messages builds on top of
existing communication infrastructure. At the time of writing this underlying communication
infrastructure is the Session Initiation Protocol (SIP) and the Extensible Messaging and Presence Protocol (XMPP).
These distributed services consist of a variety of
actors playing different roles. On a high level we differentiate between the User, and the Message Handling Service (MHS) actors.
We will describe them in more detail below.
</t>
<section title="User Actors">
<t> Users are the sources and sinks of alert messages. We differentiate between two types of users:</t>
<t>
<list style="symbols">
<t> Authors </t>
<t> Recipients </t>
</list>
</t>
<t>From the user perspective, all alert message transfer activities are performed by a
monolithic Message Handling Service (MHS), even though the actual service can be provided
by many independent organizations. </t>
<section title="Author">
<t> The Author is a human responsible for creating the alert message, its contents, and its
intended recipients, even though the exact list of recipients may be unknown to the
Author at the time of writing the alert message. The MHS transfers the alert message
from the Author and delivers it to the Recipients.</t>
</section>
<section title="Recipient">
<t> The Recipient is a consumer of the delivered alert message. It is a human reading the alert message.</t>
</section>
</section>
<section title="Message Handling Service (MHS) Actors">
<t> The Message Handling Service (MHS) performs a single end-to-end transfer of warning
messages on behalf of the Author to reach the Recipient.
As a pragmatic heuristic MHS actors actors generate, modify or look at only
transfer data, rather than the entire message. </t>
<t>
<xref target="actors-figure"/> shows the relationships among transfer participants.
Although it shows the Originator as distinct from the Author and Receiver as distinct from
Recipient, each pair of roles usually has the same actor. Transfers typically entail one
or more Relays. However, direct delivery from the Originator to Receiver is possible.
Delivery of warning messages within a single administrative boundary usually only involve
a single Relay. </t>
<t>
<figure anchor="actors-figure" title="Relationships Among MHS Actors">
<artwork>
<![CDATA[
++==========++ ++===========++
|| Author || || Recipient ||
++====++====++ ++===========++
|| /\
|| ||
\/ ||
+----------+ +---++----+
| | | |
/-+----------+----------------------------+---------+---\
| | | Message Handling | | |
| |Originator| System (MHS) |Receiver | |
| | | | | |
| +---++-----+ +---------+ |
| || /\ |
| || || |
| \/ || |
| +---------+ +---------+ +-+--++---+ |
| | Relay +======-=>| Relay +=======>| Relay | |
| +---------+ +----++---+ +---------+ |
| || |
| || |
| \/ |
| +---------+ |
| | Gateway +--> |
| +---------+ |
\-------------------------------------------------------/
Legend: === and || lines indicate primary (possibly
indirect) transfers or roles
]]></artwork>
</figure>
</t>
<section title="Originator">
<t> The Originator ensures that a warning message is valid for transfer and then submits
it to a Relay. A message is valid if it conforms to both communication and warning
message encapsulation standards and local operational policies. The Originator can
simply review the message for conformance and reject it if it finds errors, or it can
create some or all of the necessary information. </t>
<t> The Originator serves the Author and can be the same entity in absence of a human crafting alert messages.</t>
<t> The Originator also performs any post-submission, Author-related administrative tasks
associated with message transfer and delivery. Notably, these tasks pertain to sending
error and delivery notices, enforcing local policies, and dealing with messages from the
Author that prove to be problematic for the Internet. The Originator is accountable for
the message content, even when it is not responsible for it. The Author creates the
message, but the Originator handles any transmission issues with it. </t>
</section>
<section title="Relay">
<t> The Relay performs MHS-level transfer-service routing and store-and-forward, by
transmitting or retransmitting the message to its Recipients. The Relay may add history
information (e.g., as available with SIP History Info <xref
target="RFC4244"/>) or security related protection (e.g., as available with SIP
Identity <xref target="RFC4474"/>) but does not modify the envelope information or the
message content semantics. </t>
<t> A Message Handling System (MHS) network consists of a set of Relays. This MHS network is
above any underlying packet-switching network that might be used and below any Gateways. </t>
</section>
<section title="Gateway">
<t> A Gateway is a hybrid of User and Relay that connects heterogeneous communication
infrastructures. Its purpose is to emulate a Relay and the closer it comes to this, the
better. A Gateway operates as a User when it needs the ability to modify message
content. </t>
<t> Differences between the different communication systems can be as small as minor
syntax variations, but they usually encompass significant, semantic distinctions. Hence,
the Relay function in a Gateway presents a significant design challenge, if the
resulting performance is to be seen as nearly seamless. The challenge is to ensure
user-to-user functionality between the communication services, despite differences in
their syntax and semantics. </t>
<t> The basic test of Gateway design is whether an Author on one side of a Gateway can
send a useful warning message to a Recipient on the other side, without requiring
changes to any components in the Author's or Receiver's communication service other
than adding the Gateway. To each of these otherwise independent services, the Gateway
appears to be a native participant. </t>
</section>
<section title="Receiver">
<t> The Receiver performs final delivery or sends the warning message to an alternate
address. In case of warning messages it is typically responsible for ensuring that the
appropriate user interface interactions are triggered to interact with the Recipient. </t>
</section>
</section>
</section>
</section>
<!-- ////////////////////////////////////////////////////////////////////////////////// -->
<section title="Requirements" toc="default">
<section title="Requirements for Alert Subscription">
<t>The requirements listed below refer to the alert subscription phase. </t>
<t>
<list style="hanging">
<t hangText="Req-S1:"><vspace blankLines="1"/>The protocol solution MUST allow a potential
Recipient to indicate the language used by alert messages.
<vspace blankLines="1"/>
</t>
<t hangText="Req-S2:"><vspace blankLines="1"/>The protocol solution MUST allow a potential
Recipient to express the geographical area it wants to receive alerts about.
<vspace blankLines="1"/></t>
<t hangText="Req-S3:"><vspace blankLines="1"/>The protocol solution MUST allow a potential
Recipient to indicate preferences about the type of alerts it wants to receive.
<vspace blankLines="1"/></t>
<t hangText="Req-S4:"><vspace blankLines="1"/>The protocol solution MUST allow a potential
Recipient to express preference for certain media types. The support for different media
types depends on the content of the warning message but also impacts the communication protocol.
This functionality is, for example, useful for hearing and vision impaired persons.
<vspace blankLines="1"/></t>
</list>
</t>
</section>
<section title="Requirements for Alert Message Delivery">
<t>The requirements listed below refer to the delivery of alerts.</t>
<t>
<list style="hanging">
<t hangText="Req-D1:"><vspace blankLines="1"/>The protocol solution MUST allow delivery of alerts
by utilizing the lower layer infrastructure ensuring congestion control being considered. Note that
congestion does not only focus on over-utilization of a network caused by a large number of alerts
but also in relationship with other traffic not related to exigent communication. Network layer
multicast, anycast or broadcast mechanisms may be utilized. The topological network structure may
be used for efficient alert distribution.<vspace blankLines="1"/>
</t>
<t hangText="Req-D2:">
<vspace blankLines="1"/>The protocol solution MUST allow delivery of messages
simultaneously to a large audience. <vspace blankLines="1"/>
</t>
<t hangText="Req-D3:"><vspace blankLines="1"/>The protocol solution MUST be independent
of the underlying link layer technology. <vspace blankLines="1"/>
</t>
<t hangText="Req-D4:">
<vspace blankLines="1"/>The protocol solution MUST allow targeting notifications to
specific individuals and to groups of individuals.<vspace blankLines="1"/>
</t>
<t hangText="Req-D5:"><vspace blankLines="1"/>The protocol solution MUST allow a
Recipient to learn the identity of the Author of the alert message. <vspace blankLines="1"/></t>
</list>
</t>
</section>
</section>
<!-- ////////////////////////////////////////////////////////////////////////////////// -->
<section title="IANA Considerations" toc="default">
<t>This document does not require actions by IANA.</t>
</section>
<!-- ////////////////////////////////////////////////////////////////////////////////// -->
<section title="Security Considerations" toc="default" anchor="section-security">
<t><xref target="actors-figure"/> shows the actors for delivering an alert message assuming
that a prior subscription has taken place already. The desired security properties of an MHS
for conveying alerts will depend on the number of administrative domains involved. Each
administrative domain can have vastly different operating policies and trust-based
decision-making. One obvious example is the distinction between alert messages that are
exchanged within an closed group (such as alert messages received by parents affecting the
school attended by their children) and alert messages that are exchanged between independent
organizations (e.g., in case of large scale disasters). The rules for handling both types
of communication architectures tend to be quite different. That difference requires defining
the boundaries of each.</t>
<t> Operation of communication systems that are used to convey alert messages are typically
carried out by different providers (or operators). Since each be in operated in an
independent administrative domain it is useful to consider administrative domain boundaries
in the description to facilitate discussion about designs, policies and operations that need
to distinguish between internal issues and external entities. Most significant is that the
entities communicating across administrative boundaries typically have the added burden of
enforcing organizational policies concerning external communications. For example, routing
alerts between administrative domains can create requirements, such as needing to route
alert messages between organizational partners over specially trusted paths.</t>
<t> The communication interactions are subject to the policies of that domain, which cover
concerns such as these:</t>
<t>
<list style="symbols">
<t>Reliability</t>
<t>Access control</t>
<t>Accountability</t>
<t>Content evaluation, adaptation, and modification</t>
</list>
</t>
<t>Many communication system make the distinction of administrative domains since they impact the
requirements on security solutions. However, with the distribution of alert messages a number of
additional security threats need to be addressed. Due to the nature of alerts it is quite likely
that end device implementations will offer user interface enhancements to get the Recipients
attention whenever an alert arrives, which is an attractive property for adversaries to exploit.
Below we list the most important threats any solution will have to deal with.
</t>
<t>
<list style="hanging">
<t hangText="Originator Impersonation:">
<vspace blankLines="1"/> An attacker could then conceivably attempt to impersonate
the Originator of an alert message. This threat is particularly applicable to those
deployment environments where authorization decisions are based on the identity of
the Originator.<vspace blankLines="1"/>
</t>
<t hangText="Alert Message Forgery:">
<vspace blankLines="1"/> An attacker could forge or alter an alert message in order
to convey custom messages to Recipients to get their immediate attention.
<vspace blankLines="1"/>
</t>
<t hangText="Replay:">
<vspace blankLines="1"/> An attacker could obtain previously distributed alert messages
and to replay them at a later time in the hope that Recipients could be tricked into
believing they are fresh. <vspace blankLines="1"/>
</t>
<t hangText="Unauthorized Distribution:">
<vspace blankLines="1"/> When a Receiver receives an alert message it has to determine
whether the Author distributing the alert messages is genuine to avoid accepting
messages that are injected by malicious entities with the potential desire to at least
get the immediate attention of the Recipient.<vspace blankLines="1"/>
</t>
<t hangText="Amplification Attack:">
<vspace blankLines="1"/> An attacker may use the Message Handling System to inject a single
alert message for distribution that may then be instantly turned into potentially millions
of alert messages for distribution.
</t>
</list>
</t>
<t>One important security challenge is related to authorization. When an alert message arrives at the
Receiver then certain security checks may need to be performed to ensure that the alert message meets
certain criteria. The final consumer of the alert message is, however, the Recipient - a human. From
a security point of view the work split between the Recipient and the Receiver for making the
authorization decision is important, particularly when an alert message is rejected due to a failed
security verfication by the Receiver. False positives may be fatal but accepting every alert message
lowers the trustworthiness in the overall system.
</t>
</section>
<!-- ////////////////////////////////////////////////////////////////////////////////// -->
<section title="Acknowledgments" toc="default">
<!--
<t>This document reuses requirements captured outside the IETF, namely ETSI (with <xref
target="ETSI-TS-102-182"/>), and the 3GPP (with <xref target="3GPP-TR-22.968"/>). We would
like to thank the authors of these specifications for their work. Note, however, that only a
small subset of the requirements have been reflected that do not relate to specific
deployments, user interface aspects, detailed regulatory requirements, management and
operational considerations, and non-IP specific technologies.</t>
<t>We would like to thank Leopold Murhammer for his review in July 2007.</t>
-->
<t>This document re-uses text from <xref target="RFC5598"/>. The
authors would like to thank Dave Crocker for his work.</t>
<t>The authors would like to thank Martin Thomson, Carl Reed, Leopold Murhammer, and
Tony Rutkowski for their comments.</t>
<t>At IETF#79 the following persons provided feedback leading to changes in this document:
Keith Drage, Scott Bradner, Ken Carberg, Keeping Li, Martin Thomson, Igor Faynberg,
Mark Wood, Peter Saint-Andre.</t>
</section>
</middle>
<back>
<references title="Normative References"> &RFC2119; &RFC5598; </references>
<references title="Informative References"> &RFC4244; &RFC4474; <reference
anchor="July2005">
<front>
<title>Report of the 7 July Review Committee, ISBN 1 85261 878 7</title>
<author fullname="Greater London Authority" initials=" " surname=" ">
<organization>www.london.gov.uk</organization>
</author>
<date month="June" year="2006"/>
</front>
<seriesInfo name="(PDF document),"
value="http://www.london.gov.uk/assembly/reports/7july/report.pdf"/>
</reference>
<!-- <reference anchor="ETSI-TS-102-182">
<front>
<title>ETSI TS 102 182, V1.2.1 (2006-12), Technical Specification, Emergency
Communications (EMTEL); Requirements for communications from authorities/organizations
to individuals, groups or the general public during emergencies</title>
<author fullname=" " initials=" " surname=" ">
<organization>ETSI</organization>
</author>
<date month="December" year="2006"/>
</front>
<format target="" type="PDF"/>
</reference>
<reference anchor="3GPP-TR-22.968">
<front>
<title>3GPP TR 22.968, V1.0.0 (2007-04), 3rd Generation Partnership Project; Technical
Specification Group Services and System Aspects; Study for requirements for a Public
Warning System (PWS) Service (Release 8) </title>
<author fullname=" " initials=" " surname=" ">
<organization>ETSI</organization>
</author>
<date month="December" year="2006"/>
</front>
<format target="" type="PDF"/>
</reference>
-->
</references>
</back>
</rfc>
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