ATOCA B. Rosen
Internet-Draft NeuStar, Inc.
Intended status: Standards Track H. Schulzrinne
Expires: April 21, 2011 Columbia U.
H. Tschofenig
Nokia Siemens Networks
October 18, 2010
Session Initiation Protocol (SIP) Event Package for the Common Alerting
Protocol (CAP)
draft-ietf-atoca-cap-00.txt
Abstract
The Common Alerting Protocol (CAP) is an XML document format for
exchanging emergency alerts and public warnings. This document
allows CAP documents to be distributed via the event notification
mechanism available with the Session Initiation Protocol (SIP).
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 April 21, 2011.
Copyright Notice
Copyright (c) 2010 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
Rosen, et al. Expires April 21, 2011 [Page 1]
Internet-Draft SIP CAP October 2010
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. The 'common-alerting-protocol' Event Package . . . . . . . . . 5
3.1. Package Name . . . . . . . . . . . . . . . . . . . . . . . 5
3.2. Event Package Parameters . . . . . . . . . . . . . . . . . 5
3.3. SUBSCRIBE Bodies . . . . . . . . . . . . . . . . . . . . . 5
3.3.1. Location Filter . . . . . . . . . . . . . . . . . . . 5
3.3.2. Service Filter . . . . . . . . . . . . . . . . . . . . 6
3.3.3. Rate Control . . . . . . . . . . . . . . . . . . . . . 7
3.4. Subscription Duration . . . . . . . . . . . . . . . . . . 7
3.5. NOTIFY Bodies . . . . . . . . . . . . . . . . . . . . . . 7
3.6. Notifier Processing of SUBSCRIBE Requests . . . . . . . . 8
3.7. Notifier Generation of NOTIFY Requests . . . . . . . . . . 8
3.8. Subscriber Processing of NOTIFY Requests . . . . . . . . . 9
3.9. Handling of Forked Requests . . . . . . . . . . . . . . . 9
3.10. Rate of Notifications . . . . . . . . . . . . . . . . . . 9
3.11. State Agents . . . . . . . . . . . . . . . . . . . . . . . 9
3.12. Examples . . . . . . . . . . . . . . . . . . . . . . . . . 10
3.13. Use of URIs to Retrieve State . . . . . . . . . . . . . . 10
3.14. PUBLISH Bodies . . . . . . . . . . . . . . . . . . . . . . 10
3.15. PUBLISH Response Bodies . . . . . . . . . . . . . . . . . 10
3.16. Multiple Sources for Event State . . . . . . . . . . . . . 10
3.17. Event State Segmentation . . . . . . . . . . . . . . . . . 10
3.18. Rate of Publication . . . . . . . . . . . . . . . . . . . 11
4. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
5. Security Considerations . . . . . . . . . . . . . . . . . . . 13
5.1. Amplification . . . . . . . . . . . . . . . . . . . . . . 13
5.1.1. Forgery of Alerts . . . . . . . . . . . . . . . . . . 14
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15
6.1. Registration of the 'common-alerting-protocol' Event
Package . . . . . . . . . . . . . . . . . . . . . . . . . 15
6.2. Registration of the
'application/common-alerting-protocol+xml' MIME type . . . 15
6.3. Early Warning Service URNs . . . . . . . . . . . . . . . . 16
7. Open Issues . . . . . . . . . . . . . . . . . . . . . . . . . 18
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 19
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 20
9.1. Normative References . . . . . . . . . . . . . . . . . . . 20
9.2. Informative References . . . . . . . . . . . . . . . . . . 21
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 22
Rosen, et al. Expires April 21, 2011 [Page 2]
Internet-Draft SIP CAP October 2010
1. Introduction
The Common Alerting Protocol (CAP) [cap] is an XML document format
for exchanging emergency alerts and public warnings. The abstract
architectural description for the distribution of alerts can be found
in [I-D.ietf-atoca-requirements].
This document specifies how CAP documents are distributed via the
event notification mechanism available with the Session Initiation
Protocol (SIP). Additionally, a MIME object is registered to allow
CAP documents to be exchanged in other SIP messages.
Rosen, et al. Expires April 21, 2011 [Page 3]
Internet-Draft SIP CAP October 2010
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 RFC 2119 [RFC2119].
Note that early warning specific definitions can be found in
[I-D.ietf-atoca-requirements].
Rosen, et al. Expires April 21, 2011 [Page 4]
Internet-Draft SIP CAP October 2010
3. The 'common-alerting-protocol' Event Package
RFC 3265 [RFC3265] defines a SIP extension for subscribing to remote
nodes and receiving notifications of changes (events) in their
states. It leaves the definition of many aspects of these events to
concrete extensions, i.e. event packages. This document defines such
a new "common-alerting-protocol" event package. RFC 3903 [RFC3903]
defines an extension that allows SIP User Agents to publish event
state. Event Publication Agents (EPA) use PUBLISH requests to inform
an Event State Compositor (ESC) of changes in the "common-alerting-
protocol event package. Acting as a notifier, the ESC notifies
subscribers about emergency alerts and public warnings.
3.1. Package Name
The name of this package is "common-alerting-protocol". As specified
in RFC 3265 [RFC3265], this value appears in the Event header field
present in SUBSCRIBE and NOTIFY requests. As specified in RFC 3903
[RFC3903], this value also appears in the Event header field present
in PUBLISH requests.
3.2. Event Package Parameters
RFC 3265 [RFC3265] allows event packages to define additional
parameters carried in the Event header field. This event package
does not define additional parameters.
3.3. SUBSCRIBE Bodies
RFC 3265 [RFC3265] allows a SUBSCRIBE request to contain a body.
This document allows the body to contain event filters, see [RFC4660]
and [RFC4661] with the information elements listed in the subsections
below.
3.3.1. Location Filter
The 2D location shapes listed in [RFC5491] (e.g., <Point> <Polygon>,
<Circle>, <Ellipse>, <ArcBand>) and the <civicAddress> element,
defined in [RFC5139]. Repeating these elements is allowed and the
semantic is equivalent to a union. The <alertArea> element indicates
the area of interest; whenever an event happens in this area an alert
message is delivered.
An example can be found below:
Rosen, et al. Expires April 21, 2011 [Page 5]
Internet-Draft SIP CAP October 2010
<?xml version="1.0" encoding="UTF-8"?>
<filter-set
xmlns="urn:ietf:params:xml:ns:simple-filter"
xmlns:af="urn:ietf:params:xml:ns:alert-filter"
xmlns:gml="http://www.opengis.net/gml"
xmlns:gs="http://www.opengis.net/pidflo/1.0">
<filter id="123" uri="sip:presentity@example.com">
<trigger>
<af:alertArea>
<gs:Circle
srsName="urn:ogc:def:crs:EPSG::4326">
<gml:pos>42.5463 -73.2512</gml:pos>
<gs:radius
uom="urn:ogc:def:uom:EPSG::9001">
5000
</gs:radius>
</gs:Circle>
</af:alertArea>
</trigger>
</filter>
</filter-set>
Example of a SIP SUBSCRIBE Body with a Location Filter
3.3.2. Service Filter
To filter different types of alerts the <serviceFilter> element MUST
be included as a child element of the <what> element and it MUST list
one or more Service URNs [RFC5031], which indicate the type of alerts
the recipient is interested in. This document registers a number of
alerts relevant for exigent communications, which can be found in
Section 6.
An example can be found below:
<?xml version="1.0" encoding="UTF-8"?>
<filter-set
xmlns="urn:ietf:params:xml:ns:simple-filter"
xmlns:af="urn:ietf:params:xml:ns:alert-filter">
<filter id="123" uri="sip:presentity@example.com">
<what>
<af:serviceFilter>
urn:service:warning.met
</af:serviceFilter>
</what>
Rosen, et al. Expires April 21, 2011 [Page 6]
Internet-Draft SIP CAP October 2010
</filter>
</filter-set>
Example of a SIP SUBSCRIBE Body with a Service Filter
3.3.3. Rate Control
[I-D.ietf-sipcore-event-rate-control] extends the SIP events
framework by defining three "Event" header field parameters that
allow a subscriber to set a minimum, a maximum and an average rate of
event notifications generated by the notifier. This allows a
subscriber to have overall control over the stream of notifications,
for example to avoid being flooded.
A notifier is required to send a NOTIFY request immediately after
creation of a subscription. If state is not available at that time,
then the NOTIFY request may be sent with no content. A separate
NOTIFY containing an alert message may be generated some time later
when it becomes available. Figure 1 shows a SUBSCRIBE/NOTIFY
exchange.
Subscriber Notifier
|---SUBSCRIBE(1)--->| Create subscription
|<-------200--------|
|<-----NOTIFY(2)----| Return initial notify with no state
|--------200------->|
|<-----NOTIFY(3)----| Alert message comes available
|--------200------->|
Figure 1: SUBSCRIBE/NOTIFY with Rate Control
3.4. Subscription Duration
The default expiration time for subscriptions within this package is
3600 seconds. As per RFC 3265 [RFC3265], the subscriber MAY specify
an alternate expiration in the Expires header field.
3.5. NOTIFY Bodies
As described in RFC 3265 [RFC3265], the NOTIFY message will contain
bodies describing the state of the subscribed resource. This body is
in a format listed in the Accept header field of the SUBSCRIBE
request, or a package-specific default format if the Accept header
field was omitted from the SUBSCRIBE request.
In this event package, the body of the notification contains a Common
Rosen, et al. Expires April 21, 2011 [Page 7]
Internet-Draft SIP CAP October 2010
Alerting Protocol (CAP) document, i.e., an XML document. The format
of the XML documents used by CAP are described in [cap].
For an initial notify, unlike for other event packages, there is no
current initial state, unless there's a pending alert. Hence,
returning a NOTIFY with a non-empty body only makes sense if there
are indeed active alerts.
All subscribers and notifiers of the "common-alerting-protocol" event
package MUST support the "application/common-alerting-protocol+xml"
data format. The SUBSCRIBE request MAY contain an Accept header
field. If no such header field is present, it has a default value of
"application/common-alerting-protocol+xml" (assuming that the Event
header field contains a value of "common-alerting-protocol"). If the
Accept header field is present, it MUST include "application/
common-alerting-protocol+xml".
3.6. Notifier Processing of SUBSCRIBE Requests
The contents of a CAP document may contain public information,
depending on the alert message type and the intended recipient of the
alert message. It is, however, expected that in many cases providing
CAP documents does not require authorization by subscribers.
3.7. Notifier Generation of NOTIFY Requests
RFC 3265 [RFC3265] details the formatting and structure of NOTIFY
messages. However, packages are mandated to provide detailed
information on when to send a NOTIFY, how to compute the state of the
resource, how to generate neutral or fake state information, and
whether state information is complete or partial. This section
describes those details for the common-alerting-protocol event
package.
A notifier MAY send a NOTIFY at any time. Typically, it will send
one when an alert or early warning message is available. The NOTIFY
request contains a body containing one or multiple CAP document(s).
The times at which the NOTIFY is sent for a particular subscriber,
and the contents of the body within that notification, are subject to
any rules specified by the authorization policy that governs the
subscription.
If the subscription is rejected, a NOTIFY MAY be sent. As described
in RFC 3265 [RFC3265], the Subscription-State header field indicates
the state of the subscription.
The body of the NOTIFY MUST be sent using one of the types listed in
the Accept header field in the most recent SUBSCRIBE request, or
Rosen, et al. Expires April 21, 2011 [Page 8]
Internet-Draft SIP CAP October 2010
using the type "application/common-alerting-protocol+xml" if no
Accept header field was present.
Notifiers act as Event State Compositors (ESC). Thus, they learn the
'common-alerting-protocol' event state via PUBLISH requests sent from
authorized Event Publication Agents (EPAs). A Notifier may also be
an EPA, or might accept PUBLISH requests from authorized EPAs.
3.8. Subscriber Processing of NOTIFY Requests
RFC 3265 [RFC3265] leaves it to event packages to describe the
process followed by the subscriber upon receipt of a NOTIFY request,
including any logic required to form a coherent resource state.
3.9. Handling of Forked Requests
RFC 3265 [RFC3265] requires each package to describe handling of
forked SUBSCRIBE requests.
Given that a single SUBSCRIBE might include multiple services and
locations, it is reasonable and useful for a SUBSCRIBE request to
fork and to reach multiple UAs. This is equivalent to multiple
sources providing alerts for the same geographical, with a dedicated
relay serving an aggregation function.
As a result, a forked SUBSCRIBE request can install multiple
subscriptions. Subscribers to this package MUST be prepared to
install subscription state for each NOTIFY generated as a result of a
single SUBSCRIBE.
3.10. Rate of Notifications
RFC 3265 [RFC3265] requires each package to specify the maximum rate
at which notifications can be sent.
Notifiers SHOULD NOT generate notifications for a single user at a
rate of more than once every five seconds.
3.11. State Agents
RFC 3265 [RFC3265] requires each package to consider the role of
state agents in the package and, if they are used, to specify how
authentication and authorization are done. This specification allows
state agents to be located in the network.
Rosen, et al. Expires April 21, 2011 [Page 9]
Internet-Draft SIP CAP October 2010
3.12. Examples
An example is provided in Section 4.
3.13. Use of URIs to Retrieve State
RFC 3265 [RFC3265] allows packages to use URIs to retrieve large
state documents.
CAP documents are fairly small. This event package does not provide
a mechanism to use URIs to retrieve large state documents.
3.14. PUBLISH Bodies
RFC 3903 [RFC3903] requires event packages to define the content
types expected in PUBLISH requests.
In this event package, the body of a PUBLISH request may contain a
CAP document. A CAP document describes an emergency alert or an
early warning event.
All EPAs and ESCs MUST support the "application/
common-alerting-protocol+xml" data format and MAY support other
formats.
3.15. PUBLISH Response Bodies
This specification assumes that the response to a PUBLISH does not
contain a body.
3.16. Multiple Sources for Event State
RFC 3903 [RFC3903] requires event packages to specify whether
multiple sources can contribute to the event state view at the ESC.
This event package allows different EPAs to publish CAP documents for
a particular user. The concept of composition is not applicable for
this application usage.
3.17. Event State Segmentation
RFC 3903 [RFC3903] defines segments within a state document. Each
segment is defined as one of potentially many identifiable sections
in the published event state.
This event package defines does not differentiate between different
segments.
Rosen, et al. Expires April 21, 2011 [Page 10]
Internet-Draft SIP CAP October 2010
3.18. Rate of Publication
RFC 3903 [RFC3903] allows event packages to define their own rate of
publication. This event package allows rate control to be utilized,
as described in Section 3.3.3.
Rosen, et al. Expires April 21, 2011 [Page 11]
Internet-Draft SIP CAP October 2010
4. Examples
Here is an example of a CAP document.
<?xml version="1.0" encoding="UTF-8"?>
<alert xmlns="urn:oasis:names:tc:emergency:cap:1.1">
<identifier>KSTO1055887203</identifier>
<sender>KSTO@NWS.NOAA.GOV</sender>
<sent>2003-06-17T14:57:00-07:00</sent>
<status>Actual</status>
<msgType>Alert</msgType>
<scope>Public</scope>
<info>
<category>Met</category>
<event>SEVERE THUNDERSTORM</event>
<urgency>Severe</urgency>
<certainty>Likely</certainty>
<senderName>NATIONAL WEATHER SERVICE SACRAMENTO</senderName>
<headline>SEVERE THUNDERSTORM WARNING</headline>
<description> AT 254 PM PDT...
NATIONAL WEATHER SERVICE
DOPPLER RADAR INDICATED A SEVERE
THUNDERSTORM OVER SOUTH CENTRAL ALPINE COUNTY...
OR ABOUT 18 MILES SOUTHEAST OF
KIRKWOOD... MOVING SOUTHWEST AT 5 MPH. HAIL...
INTENSE RAIN AND STRONG DAMAGING WINDS
ARE LIKELY WITH THIS STORM </description>
<instruction> TAKE COVER IN A SUBSTANTIAL SHELTER
UNTIL THE STORM PASSES </instruction>
<contact>BARUFFALDI/JUSKIE</contact>
<area>
<areaDesc> EXTREME NORTH CENTRAL TUOLUMNE COUNTY
IN CALIFORNIA, EXTREME NORTHEASTERN
CALAVERAS COUNTY IN CALIFORNIA, SOUTHWESTERN
ALPINE COUNTY IN CALIFORNIA </areaDesc>
<polygon> 38.47,-120.14 38.34,-119.95 38.52,-119.74
38.62,-119.89 38.47,-120.14 </polygon>
</area>
</info>
</alert>
Example for a Severe Thunderstorm Warning
Rosen, et al. Expires April 21, 2011 [Page 12]
Internet-Draft SIP CAP October 2010
5. Security Considerations
This section discusses security considerations when using SIP to
distribute warning messages using CAP.
Based on the framework outlined in [I-D.ietf-atoca-requirements] the
following security concerns arise:
Amplification Attacks: An adversary could inject alerts into the
message handling system and therefore a single PUBLISH request
could potentially results in millions of NOTIFY messages delivered
to receivers. Injecting messages may happen at a number of ways,
such as by adversaries who manage to impersonate a legitimate
originator, a relay or gateway. Ensuring that only authorized
entities are permitted to inject alerts is a pre-condition. This
does, however, not help if the host of a trusted participant in
the message handling system got compromised.
Forgery of Alerts: Alerts may get modified or replayed. The former
is possible if the adversary manages to get access to a relay or
gateway. Two mechanisms are proposed for countering forgery:
using digital signatures or channel security (TLS). The first
provides end-to-end security; the second utilizes a hop by hop
security model based on a transitive chain of trust.
The sub-sections below discuss these threats and their
countermeasures in more detail.
5.1. Amplification
Threat:
The attacker could then conceivably attempt to impersonate an
originator, or a relay. A side effect of being able to inject an
alert for distribution is the amplification effect.
Countermeasures:
When an entity receives a CAP message it has to determine whether
the entity distributing the CAP messages is genuine to avoid
accepting messages that are injected by malicious entities.
When receiving a CAP document a couple of verification steps must
be performed. First, it needs to be ensured that the message was
delivered via a trusted entity and that the communication channel
between the User Agent and it's SIP proxy is properly secured to
exclude various attacks at the SIP level. Then, the message
Rosen, et al. Expires April 21, 2011 [Page 13]
Internet-Draft SIP CAP October 2010
contains the <sender> that may contain an entity that falls within
the white list of the entity receiving the message. Finally, the
message is protected by a digital signature and the entity signing
the CAP message may again be listed in a white list of the
receiving entity and may therefore be trusted. If none of these
verification checks lead to a positive indication of a known
sender then the CAP document should be treated as suspicious and
configuration at the receiving entity may dictate how to process
and display CAP documents in such a case.
5.1.1. Forgery of Alerts
Threat:
A malicious user could forge a CAP document. Alternatively, a CAP
document distributed earlier could be replied.
Countermeasures:
To avoid forgery, the entities must assure that proper mechanisms
for protecting the CAP documents are employed, for example signing
the CAP document itself or securing the communication between
participating entities using TLS. Section 3.3.2.1 of [cap]
specifies the signing of CAP documents.
Regarding replay attacks the following observations can be made.
A CAP document contains the mandatory <identifier>, <sender>,
<sent> elements and an optional <expire> element. These
attributes make the CAP document unique for a specific originator/
author and provide time restrictions. An entity that has received
a CAP message already within the indicated timeframe is able to
detect a replayed message and, if the content of that message is
unchanged, then no additional security vulnerability is created.
Recipients who enter the area of a disaster after the initial
distribution of warnings may not yet have seen the original CAP
message and, as such, would not be able to distinguish a replay
from the initial message being sent around. However, if the
threat that lead to the distribution of warning messages is still
imminent then there is no reason not to worry about that message.
The originator/author distributing the alert is, however, adviced
to carefully select a value for the <expires> element and it is
RECOMMENDED to set a value for this element.
Rosen, et al. Expires April 21, 2011 [Page 14]
Internet-Draft SIP CAP October 2010
6. IANA Considerations
6.1. Registration of the 'common-alerting-protocol' Event Package
This specification registers an event package, based on the
registration procedures defined in RFC 3265 [RFC3265]. The following
is the information required for such a registration:
Package Name: common-alerting-protocol
Package or Template-Package: This is a package.
Published Document: RFC XXX [Replace by the RFC number of this
specification].
Person to Contact: Hannes Tschofenig, Hannes.Tschofenig@nsn.com
6.2. Registration of the 'application/common-alerting-protocol+xml'
MIME type
To: ietf-types@iana.org
Subject: Registration of MIME media type application/ common-
alerting-protocol+xml
MIME media type name: application
MIME subtype name: common-alerting-protocol+xml
Required parameters: (none)
Optional parameters: charset; Indicates the character encoding of
enclosed XML. Default is UTF-8 [RFC3629].
Encoding considerations: Uses XML, which can employ 8-bit
characters, depending on the character encoding used. See RFC
3023 [RFC3023], Section 3.2.
Security considerations: This content type is designed to carry
payloads of the Common Alerting Protocol (CAP).
Interoperability considerations: This content type provides a way to
convey CAP payloads.
Published specification: RFC XXX [Replace by the RFC number of this
specification].
Rosen, et al. Expires April 21, 2011 [Page 15]
Internet-Draft SIP CAP October 2010
Applications which use this media type: Applications that convey
alerts and early warnings according to the CAP standard.
Additional information: OASIS has published the Common Alerting
Protocol at [cap].
Person & email address to contact for further information: Hannes
Tschofenig, Hannes.Tschofenig@nsn.com
Intended usage: Limited use
Author/Change controller: IETF SIPPING working group
Other information: This media type is a specialization of
application/xml RFC 3023 [RFC3023], and many of the considerations
described there also apply to application/
common-alerting-protocol+xml.
6.3. Early Warning Service URNs
In according with RFC 5031 this document defines a new top-level
service called 'warning'. This section defines the first service
registration within the IANA registry using the top-level service
label 'warning'.
The 'warning' service type describes emergency services requiring an
immediate action or remedy by the recipient of the alert message as
instructed by the author of the message. Additional sub-services can
be added after expert review and must be of general public interest
and have a similar emergency nature. The expert is designated by the
ECRIT working group, its successor, or, in their absence, the IESG.
The expert review should only approve emergency services that are
offered widely and in different countries, with approximately the
same caller expectation in terms of services rendered.
The following list contains the initial IANA registration for the
'warning' service.
urn:service:warning.geo: Geophysical (inc. landslide)
urn:service:warning.met: Meteorological (inc. flood)
urn:service:warning.safety: General emergency and public safety
urn:service:warning.security: Law enforcement, military, homeland
and local/private security
Rosen, et al. Expires April 21, 2011 [Page 16]
Internet-Draft SIP CAP October 2010
urn:service:warning.rescue: Rescue and recovery
urn:service:warning.fire: Fire suppression and rescue
urn:service:warning.health: Medical and public health
urn:service:warning.env: Pollution and other environmental
urn:service:warning.transport: Public and private transportation
urn:service:warning.infra: Utility, telecommunication, other non-
transport infrastructure
urn:service:warning.cbrne: Chemical, Biological, Radiological,
Nuclear or High-Yield Explosive threat or attack
urn:service:warning.other: Other events
Rosen, et al. Expires April 21, 2011 [Page 17]
Internet-Draft SIP CAP October 2010
7. Open Issues
The authors would like to point to a number of issues that require
discussion:
Rate Control: The -00 version of the document introduced rate
control for notifications Section 3.3.3. Is this functionality is
needed?
Early Warning Service URNs: Specifying services is always difficult
since there is no universally agreed service semantic. This
document contains a proposal that re-use the classification in the
CAP specification [cap]. Is the proposal acceptable?
Event Filter: By using [RFC4660] and [RFC4661] filters in the body
of a SUBSCRIBE the number of notifications can be reduced to those
of interest to the subscriber. There is a certain overhead
associated with the generic usage of those event filters. Should
alternatives be considered?
Forked SUBSCRIBE Requests: This document allows forked subscribe
request. This is useful when a single service is offered by more
than one entity and therefore related to the cases discussed in
[I-D.forte-lost-extensions] and in
[I-D.forte-ecrit-service-classification]. For example, imagine a
warning service like 'urn:service:warning.geo' that is advertised
by a number of different service providers.
Security: The security consideration section was re-written and
focuses now mostly on two types of attacks, namely amplificiation
and forgery. Does this reflect the understanding of the group?
Rosen, et al. Expires April 21, 2011 [Page 18]
Internet-Draft SIP CAP October 2010
8. Acknowledgments
The authors would like to thank Cullen Jennings for his early support
and the participants of the Early Warning Adhoc meeting at IETF#69
for their feedback.
We would furthermore like to thank Martin Thomson for his detailed
draft review in July 2010.
Rosen, et al. Expires April 21, 2011 [Page 19]
Internet-Draft SIP CAP October 2010
9. References
9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", March 1997.
[cap] Jones, E. and A. Botterell, "Common Alerting Protocol v.
1.1", October 2005.
[RFC3265] Roach, A., "Session Initiation Protocol (SIP)-Specific
Event Notification", RFC 3265, June 2002.
[RFC3903] Niemi, A., "Session Initiation Protocol (SIP) Extension
for Event State Publication", RFC 3903, October 2004.
[RFC3023] Murata, M., St. Laurent, S., and D. Kohn, "XML Media
Types", RFC 3023, January 2001.
[RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO
10646", STD 63, RFC 3629, November 2003.
[RFC5491] Winterbottom, J., Thomson, M., and H. Tschofenig, "GEOPRIV
Presence Information Data Format Location Object (PIDF-LO)
Usage Clarification, Considerations, and Recommendations",
RFC 5491, March 2009.
[RFC5139] Thomson, M. and J. Winterbottom, "Revised Civic Location
Format for Presence Information Data Format Location
Object (PIDF-LO)", RFC 5139, February 2008.
[RFC5031] Schulzrinne, H., "A Uniform Resource Name (URN) for
Emergency and Other Well-Known Services", RFC 5031,
January 2008.
[I-D.ietf-sipcore-event-rate-control]
Niemi, A., Kiss, K., and S. Loreto, "Session Initiation
Protocol (SIP) Event Notification Extension for
Notification Rate Control",
draft-ietf-sipcore-event-rate-control-04 (work in
progress), July 2010.
[RFC4660] Khartabil, H., Leppanen, E., Lonnfors, M., and J. Costa-
Requena, "Functional Description of Event Notification
Filtering", RFC 4660, September 2006.
[RFC4661] Khartabil, H., Leppanen, E., Lonnfors, M., and J. Costa-
Requena, "An Extensible Markup Language (XML)-Based Format
Rosen, et al. Expires April 21, 2011 [Page 20]
Internet-Draft SIP CAP October 2010
for Event Notification Filtering", RFC 4661,
September 2006.
9.2. Informative References
[I-D.ietf-atoca-requirements]
Schulzrinne, H., Norreys, S., Rosen, B., and H.
Tschofenig, "Requirements, Terminology and Framework for
Exigent Communications", draft-ietf-atoca-requirements-00
(work in progress), September 2010.
[I-D.forte-lost-extensions]
Forte, A. and H. Schulzrinne, "Location-to-Service
Translation Protocol (LoST) Extensions",
draft-forte-lost-extensions-02 (work in progress),
September 2010.
[I-D.forte-ecrit-service-classification]
Forte, A. and H. Schulzrinne, "Labels for Common Location-
Based Services",
draft-forte-ecrit-service-classification-03 (work in
progress), January 2010.
Rosen, et al. Expires April 21, 2011 [Page 21]
Internet-Draft SIP CAP October 2010
Authors' Addresses
Brian Rosen
NeuStar, Inc.
470 Conrad Dr
Mars, PA 16046
US
Phone:
Email: br@brianrosen.net
Henning Schulzrinne
Columbia University
Department of Computer Science
450 Computer Science Building
New York, NY 10027
US
Phone: +1 212 939 7004
Email: hgs+ecrit@cs.columbia.edu
URI: http://www.cs.columbia.edu
Hannes Tschofenig
Nokia Siemens Networks
Linnoitustie 6
Espoo 02600
Finland
Phone: +358 (50) 4871445
Email: Hannes.Tschofenig@gmx.net
URI: http://www.tschofenig.priv.at
Rosen, et al. Expires April 21, 2011 [Page 22]