wdiff draft-ietf-ecrit-data-only-ea-01.txt draft-ietf-ecrit-data-only-ea-02.txt

ECRIT B. Rosen
Internet-Draft NeuStar, Inc.
Intended status: Experimental H. Schulzrinne
Expires: April 28, 2011 January 11, 2012 Columbia U.
H. Tschofenig
Nokia Siemens Networks
October 25, 2010
July 10, 2011

Common Alerting Protocol (CAP) based Data-Only Emergency Alerts using the Session
Initiation Protocol (SIP)
draft-ietf-ecrit-data-only-ea-01.txt
draft-ietf-ecrit-data-only-ea-02.txt

Abstract

The Common Alerting Protocol (CAP) is a document format for
exchanging emergency alerts and public warnings. CAP is mainly used
for conveying alerts and warnings between authorities and from
authorities to citizen/individuals. This document describes how
data-only emergency alerts allow
devices use CAP to issue alerts using the
CAP document format. emergency alerts.

Status of this Memo

This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.

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This Internet-Draft will expire on April 28, 2011. January 11, 2012.

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Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Architectural Overview . . . . . . . . . . . . . . . . . . . . 5
4. Protocol Specification . . . . . . . . . . . . . . . . . . . . 7
4.1. CAP Transport . . . . . . . . . . . . . . . . . . . . . . 7
4.2. Profiling of the CAP Document Content . . . . . . . . . . 7
5. Example . . Error Handling . . . . . . . . . . . . . . . . . . . . . . . . . 8
6. Security Considerations 9
5.1. 425 (Bad Alert Message) Response Code . . . . . . . . . . 9
5.2. The AlertMsg-Error Header Field . . . . . . . . . 10
6.1. Forgery . . . . 9
6. Example . . . . . . . . . . . . . . . . . . . . . 10
6.2. Replay Attack . . . . . . 12
7. Security Considerations . . . . . . . . . . . . . . . . 10
6.3. Injecting False Alerts . . . 14
8. IANA Considerations . . . . . . . . . . . . . . . 11
7. IANA Considerations . . . . . . 16
8.1. Registration of the 'application/cap+xml' MIME type . . . 16
8.2. IANA Registration for 425 Response Code . . . . . . . . . 17
8.3. IANA Registration of New AlertMsg-Error Header Field . . . 12
7.1. 17
8.4. IANA Registration of for the
'application/common-alerting-protocol+xml' MIME type SIP AlertMsg-Error Codes . . . 12
8. . 18
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 14
9. 19
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 15
9.1. 20
10.1. Normative References . . . . . . . . . . . . . . . . . . . 15
9.2. 20
10.2. Informative References . . . . . . . . . . . . . . . . . . 15 21
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 17 22

1. Introduction

The Common Alerting Protocol (CAP) [cap] is an XML document format
for exchanging emergency alerts and public warnings. CAP is mainly
used for conveying alerts and warnings between authorities and from
authorities to citizen/individuals. This document describes how
data-only emergency calls are able to utilize the same CAP document
format.

Emergency alerts containing data are similar to regular emergency
calls in the sense that they require emergency call routing
functionality and may even have the same location requirements. On
the other hand, the communication interaction may occur without
establishment of a voice or video channel.

Data-only emergency alerts are similar to regular emergency calls in
the sense that they require emergency call routing functionality and
may even have the same location requirements. On the other hand, the
initial communication interaction will not lead to the establishment
of a voice or video channel.

Based on the deployment experience with non-IP based systems we
distinguish between systems, two types of environments, namely (1) data-only
emergency
major deployment scenarios are envisaged:

1. Emergency alerts that containing only data are targeted directly to a recipient
responsible for evaluating the alerts and for taking the necessary next steps, including triggering which could include:

1. Sending an emergency call towards alert containing only data toward a Public Safety
Answering Point (PSAP) and (2) alerts (PSAP);

2. Establishing an emergency call with a PSAP that are could include
audio/video as well as data

2. Emergency alerts targeted to a Service URN as used for regular IP-based
emergency calls where the recipient is not known to the
originator. In this scenario, the alert may contain only data
(e.g. a CAP and a PIDF-LO payload in a SIP MESSAGE) or could be
included along with establishment of an audio/video channel (e.g.
SIP INVITE)

We describe these two cases in more detail in Section 3.

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].

This document utilizes terminology introduced in
[I-D.ietf-atoca-requirements]. In particular, the terms for author,
originator, receiver and recipient, are relevant for this document.
The originator and the receiver are SIP-based entities while the
author and the recipient are entities that relate to the alert
message delivery, when this is relevant for the communication.

3. Architectural Overview

This section illustrates two envisioned usage modes; targeted and
location-based emergency alert routing. Figure 1 shows a deployment
variant where a sensor, as the author and originator of the alert, is
pre-configured (using techniques outside the scope of this document)
to issue an alert to a receiver or an aggregator, a special form of
mediator, that processes these messages and performs whatever steps
are necessary to appropriately react on the alert. For example, a
security firm may use different sensor inputs to dispatch their
security staff to a building they protect. protect or to initiate a third
party emergency call.

+------------+ +------------+
| Sensor | | Aggregator |
| | | |
+---+--------+ +------+-----+
| |
Sensors |
trigger |
emergency |
alert |
| MESSAGE with CAP |
|----------------------------->|
| |
| Aggregator
| processes
| emergency
| alert
| 200 (OK) |
|<-----------------------------|
| |
| |

Figure 1: Targeted Emergency Alert Routing

In Figure 2 a scenario is shown whereby the alert is routed using
location information and the Service URN. In case the LoST
resolution is done at an An emergency services
routing proxy rather than
at the entity issuing the alert since it (ESRP) may not know use LoST to determine the address of next hop proxy to
route the receiver. alert message to. A possible receiver is a PSAP and the
recipient of the alert may be call taker. In the generic case, there
is very likely no prior relationship between the originator and the
receiver, e.g. PSAP. A PSAP, for example, is likely to receive and
accept alerts from entities it cannot authorize. This scenario
corresponds more to the classical emergency services use case and the
description in [I-D.ietf-ecrit-phonebcp] is applicable.

+-----------+ +----------+
+--------+ | SIP Proxy ESRP | | PSAP as |
| Sensor | | as Relay | | Receiver |
+---+----+ +---+-------+ +---+------+
| | |
Sensors | |
trigger | |
emergency | |
alert | |
| | |
| | |
| MESSAGE with CAP | |
| (including Service URN, |
| such as urn:service:sos) |
|------------------->| |
| | |
| SIP Proxy ESRP performs |
| emergency alert |
| routing |
| | MESSAGE with CAP |
| | (including identity info) |
| |----------------------------->|
| | |
| | PSAP
| | processes
| | emergency
| | alert
| | 200 (OK) |
| |<-----------------------------|
| | |
| 200 (OK) | |
|<-------------------| |
| | |
| | |

Figure 2: Location-Based Emergency Alert Routing

4. Protocol Specification

4.1. CAP Transport

Since alerts structured via CAP require a "push" medium, they SHOULD
be sent via the medium. The
following SIP MESSAGE. requests MAY carry the CAP payload defined in this
document: INVITE [RFC3261], UPDATE [RFC3311], MESSAGE [RFC3428], INFO
[RFC6086], NOTIFY [RFC3265], and PUBLISH [RFC3903]. The MIME type is
set to 'application/
common-alerting-protocol+xml'.

Alternatively, 'application/cap+xml'.

If the SIP PUBLISH mechanism or other SIP messages
could server does not support the functionality required to fulfill
the request then a 501 Not Implemented MUST be used. However, returned by RFC 3261
[RFC3261]. This is the usage appropriate response when a UAS does not
recognize the request method and is not capable of SIP MESSAGE supporting it for
any user.

The 415 Unsupported Media Type error MUST be returned by RFC 3261
[RFC3261] if the server is refusing to service the request because
the message body of the request is in a simple
enough approach from an implementation point format not supported by the
server for the requested method. The server MUST return a list of view.
acceptable formats using the Accept, Accept-Encoding, or Accept-
Language header field, depending on the specific problem with the
content.

4.2. Profiling of the CAP Document Content

The usage of CAP MUST conform to the specification provided with
[cap]. For the usage with SIP the following additional requirements
are imposed:

sender: A few sub-categories for putting a value in the <sender>
element have to be considered:

Originator is a SIP entity, Author indication irrelevant: When
the CAP alert was created by a SIP-based entity originator and it is not
useful to be explicit about the author of the alert then the
<sender> element MUST be populated with the SIP URI of the user
agent.

Originator is a non-SIP entity, Author indication irrelevant: In
case that entity. the alert was created by a non-SIP based entity and
the identity of this original sender wants to be preserved then
this identity MUST be placed into the <sender> element. In
this category the it is not useful to be explicit about the
author of the alert. The specific type of identity being used
will depends on the technology being used by the original
originator.

Author indication relevant: In case the author is different from
the actual originator of the message and this distinction wants
to be preserved then the <sender> element MUST NOT contain the
SIP URI.

incidents: The <incidents> element MUST be present whenever there is
a possibility that alert information needs to be updated. The
initial message will then contain an incident identifier carried
in the <incidents> element. This incident identifier MUST be
chosen in such a way that it is unique for a given <sender,
expires, incidents> combination. Note that the <expires> element
is optional and may not be present.

scope: The value of the <scope> element MUST be set to "private" "Private" as
the alert is not meant for public consumption. The <addresses>
element is, however, not used by this specification since the
message routing is performed by SIP and the respective address
information is already available in the geolocation header. other SIP headers. Populating location
information twice into different parts of the message can quickly may lead to
inconsistency.

parameter: The <parameter> element MAY contain additional
information specific to the sensor.

area: It is RECOMMENDED to omit this element when constructing a
message. In case that the CAP message already contained an <area>
element then the specified location information MUST be copied
into the PIDF-LO structure of the geolocation header element. 'geolocation' header.

5. Error Handling

This section defines a new error response code and a header field for
additional information.

5.1. 425 (Bad Alert Message) Response Code

This SIP extension creates a new location-specific response code,
defined as follows,

425 (Bad Alert Message)

The 425 response code is a rejection of the request due to its
included alert content, indicating that it was malformed or not
satisfactory for the recipient's purpose.

A SIP intermediary can also reject an alert it receives from a UA
when it understands that the provided alert is malformed.

Section 5.2 describes a AlertMsg-Error header field with more details
about what was wrong with the alert message in the request. This
header field MUST be included in the 425 response.

It is only appropriate to generate a 425 response when the responding
entity has no other information in the request that are usable by the
responder.

A 425 response code MUST NOT be sent in response to a request that
lacks an alert message entirely, as the user agent in that case may
not support this extension at all.

A 425 response is a final response within a transaction, and MUST NOT
terminate an existing dialog.

5.2. The AlertMsg-Error Header Field

The AlertMsg-Error header provides additional information about what
was wrong with the original request. In some cases the provided
information will be used for debugging purposes.

The AlertMsg-Error header field has the following ABNF [RFC5234]:

message-header /= AlertMsg-Error
; (message-header from 3261)
AlertMsg-Error = "AlertMsg-Error" HCOLON
ErrorValue
ErrorValue = error-code
*(SEMI error-params)
error-code = 1*3DIGIT
error-params = error-code-text
/ generic-param ; from RFC3261
error-code-text = "code" EQUAL quoted-string ; from RFC3261

HCOLON, SEMI, and EQUAL are defined in RFC3261 [RFC3261]. DIGIT is
defined in RFC5234 [RFC5234].

The AlertMsg-Error header field MUST contain only one ErrorValue to
indicate what was wrong with the alert payload the recipient
determined was bad.

The ErrorValue contains a 3-digit error code indicating what was
wrong with the alert in the request. This error code has a
corresponding quoted error text string that is human understandable.
The text string are OPTIONAL, but RECOMMENDED for human readability,
similar to the string phrase used for SIP response codes. That said,
the strings are complete enough for rendering to the user, if so
desired. The strings in this document are recommendations, and are
not standardized - meaning an operator can change the strings - but
MUST NOT change the meaning of the error code. Similar to how RFC
3261 specifies, there MUST NOT be more than one string per error
code.

The AlertMsg-Error header field MAY be included in any response as an
alert message was in the request part of the same transaction. For
example, a UA includes an alert in an MESSAGE to a PSAP. The PSAP
can accept this MESSAGE, thus creating a dialog, even though his UA
determined the alert message contained in the MESSAGE was bad. The
PSAP merely includes a AlertMsg-Error header value in the 200 OK to
the MESSAGE informing the UA that the MESSAGE was accepted but the
alert provided was bad.

If, on the other hand, the PSAP cannot accept the MESSAGE without a
suitable alert message, a 425 response is sent.

A SIP intermediary that requires the UA's alert message in order to
properly process the MESSAGE may also sends a 425 with a AlertMsg-
Error code.

This document defines an initial list of error code ranges for any
SIP response, including provisional responses (other than 100 Trying)
and the new 425 response. There MUST be no more than one AlertMsg-
Error code in a SIP response.

AlertMsg-Error: 100 ; code="Cannot Process the Alert Payload"

AlertMsg-Error: 101 ; code="Alert Payload was not present or could
not be found"

AlertMsg-Error: 102 ; code="Not enough information to determine the
purpose of the alert"

AlertMsg-Error: 103 ; code="Alert Payload was corrupted"

Additionally, if an LR cannot or chooses not to process the alert
message from a SIP request, a 500 (Server Internal Error) SHOULD be
used with or without a configurable Retry-After header field.

6. Example

Figure 3 shows a CAP document indicating a BURLARY alert issued by a
sensor with the identity 'sensor1@domain.com'. The location of the
sensor can be obtained from the attached geolocation location information
provided via the geolocation 'geolocation' header contained in the SIP MESSAGE
structure. Additionally, the sensor provided some data long with the
alert message using proprietary information elements only to be
processed by the receiver, a SIP entity acting as an aggregator.
This example reflects the description in Figure 1.

MESSAGE sip:aggregator@domain.com SIP/2.0
Via: SIP/2.0/TCP sensor1.domain.com;branch=z9hG4bK776sgdkse
Max-Forwards: 70
From: sip:sensor1@domain.com;tag=49583
To: sip:aggregator@domain.com
Call-ID: asd88asd77a@1.2.3.4
Geolocation: <cid:abcdef@domain.com>
;routing-allowed=yes
Supported: geolocation
Accept: application/pidf+xml, application/common-alerting-protocol+xml application/cap+xml
CSeq: 1 MESSAGE
Content-Type: multipart/mixed; boundary=boundary1
Content-Length: ...

--boundary1

Content-Type: common-alerting-protocol+xml cap+xml
Content-ID: <abcdef2@domain.com>
<?xml version="1.0" encoding="UTF-8"?>

<alert xmlns="urn:oasis:names:tc:emergency:cap:1.1">
<identifier>S-1</identifier>
<sender>sip:sensor1@domain.com</sender>
<sent>2008-11-19T14:57:00-07:00</sent>
<status>Actual</status>
<msgType>Alert</msgType>
<scope>Private</scope>
<incidents>abc1234</incidents>
<info>
<category>Security</category>
<event>BURGLARY</event>
<urgency>Expected</urgency>
<certainty>Likely</certainty>
<severity>Moderate</severity>
<senderName>SENSOR 1</senderName>
<parameter>
<valueName>SENSOR-DATA-NAMESPACE1</valueName>
<value>123</value>
</parameter>
<parameter>
<valueName>SENSOR-DATA-NAMESPACE2</valueName>
<value>TRUE</value>
</parameter>
</info>
</alert>

--boundary1

Content-Type: application/pidf+xml
Content-ID: <abcdef2@domain.com>
<?xml version="1.0" encoding="UTF-8"?>
<presence
xmlns="urn:ietf:params:xml:ns:pidf"
xmlns:gp="urn:ietf:params:xml:ns:pidf:geopriv10"
xmlns:gbp="urn:ietf:params:xml:ns:pidf:geopriv10:basicPolicy"
xmlns:cl="urn:ietf:params:xml:ns:pidf:geopriv10:civicAddr"
xmlns:gml="http://www.opengis.net/gml"
entity="pres:sensor1@domain.com">
<tuple id="12345">
xmlns:dm="urn:ietf:params:xml:ns:pidf:data-model"
entity="pres:alice@atlanta.example.com">
<dm:device id="sensor1"> id="sensor">
<gp:geopriv>
<gp:location-info>
<gml:location>
<gml:Point srsName="urn:ogc:def:crs:EPSG::4326">
<gml:pos>32.86726 -97.16054</gml:pos>
</gml:Point>
</gml:location>
</gp:location-info>
<gp:usage-rules>
<gp:retransmission-allowed>yes
</gp:retransmission-allowed>
<gp:retention-expiry>2010-07-30T20:00:00Z
</gp:retention-expiry>
<gbp:retransmission-allowed>false
</gbp:retransmission-allowed>
<gbp:retention-expiry>2010-11-14T20:00:00Z
</gbp:retention-expiry>
</gp:usage-rules>
<gp:method>802.11</gp:method>
</gp:geopriv>
<dm:deviceID>mac:1234567890ab</dm:deviceID>
<dm:timestamp>2010-07-28T20:57:29Z</dm:timestamp>
<dm:timestamp>2010-11-04T20:57:29Z</dm:timestamp>
</dm:device>
</tuple>
</presence>
--boundary1--

Figure 3: Example Message conveying an Alert

7. Security Considerations

This section discusses security considerations when using SIP to make
data-only user agents
issue emergency alerts utilizing CAP. Location specific threats are
not unique to this document and the discussion are discussed in
[I-D.ietf-ecrit-trustworthy-location].

6.1. Forgery

Threat:

An adversary could forge or alter
[I-D.ietf-ecrit-trustworthy-location] and
[I-D.ietf-sipcore-location-conveyance].

The ECRIT emergency services architecture [I-D.ietf-ecrit-phonebcp]
considers classical individual-to-authority emergency calling and the
identity of the emergency caller does not play a CAP document role at the time of
the call establishment itself, i.e., a response to report false the emergency alarms.

Countermeasures:

To avoid this kind call
will not depend on the identity of attack, the entities must assure caller. In case of emergency
alerts generated by devices, like sensors, the processing may be
different in order to reduce the number of falsely generated
emergency alerts. Alerts may get triggered based on certain sensor
input that proper
mechanisms may have been caused by other factors than the actual
occurrence of an alert relevant event. For example, a sensor may
simply be malfunctioning. For this purpose not all alert messages
are directly sent to a PSAP but are rather pre-processed by a
separate entity, potentially under supervision by a human, to filter
alerts and potentially correlate received alerts with others to
obtain a larger picture of the ongoing situation. These two message
routing examples are shown in Figure 1 and in Figure 2.

In any case, for protecting alerts that are initiated by sensors the CAP documents identity
may play an important role in deciding whether to accept or ignore an
incoming alert message. With the scenario shown in Figure 1 it is
very likely that only authorized sensor input will be processed. For
this purpose it needs to be ensured that no alert messages from an
unknown origin are employed, e.g.,
signing accepted. Two types of information elements can
be used for this purpose:

1. SIP itself provides security mechanisms that allow the
verification of the originator's identity. These mechanisms can
be re-used, such as P-Asserted-Identity [RFC3325] or SIP Identity
[RFC4474]. The latter provides a cryptographic assurance while
the former relies on a chain of trust model.

2. CAP document itself. provides additional security mechanisms and the ability to
carry additional information about the sender's identity.
Section 3.3.2.1 of [cap] specifies the signing algorithms of CAP
documents. This does not protect
against a legitimate sensor sending phrank alerts after being
compromised.

6.2. Replay Attack

Threat:

An adversary could eavesdrop alerts

In addition to the desire to perform identity-based access control
the classical communication security threats need to be considered,
including integrity protection to prevent forgery and reply them at replay of alert
messages in transit. To deal with replay of alerts a later
time.

Countermeasures:

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 sender 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. Additionally, it is RECOMMENDED to make use of SIP
security mechanisms, such as SIP Identity [RFC4474], to tie the CAP
message to the SIP message.

6.3. Injecting False Alerts

Threat:

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 adversaries. In scenario

Countermeasures:

For some types To provide protection of data-only emergency calls author/originator and the receiver/recipient have a relationship with each other and
hence it is possible (using cryptographic techniques) to verify
whether a entire SIP
message was indeed issued by an authorized entity.
Figure 1 is such an environment. Standard exchange between neighboring SIP security mechanisms
can be re-used for this purpose. For example, identity based
access control is a viable approach utilizing the asserted
identity of entities the alert originator using P-Asserted-Identity
[RFC3325] or SIP Identity [RFC4474].

There are, however, other types usage of data-only emergency calls where
there TLS is no such relationship between the author/originator and
the receiver/recipient. Incoming alerts need to be treated more
carefully than multi-media emergency calls
mandatory.

Note that contain additional
information, such as audio, to allow none of the security mechanism in this document protect
against a call taker to sort out
phrank calls.

7. compromised sensor sending crafted alerts.

8. IANA Considerations

7.1.

8.1. Registration of the 'application/common-alerting-protocol+xml' 'application/cap+xml' MIME type

To: ietf-types@iana.org

Subject: Registration of MIME media type application/ common-
alerting-protocol+xml cap+xml

MIME media type name: application

MIME subtype name: common-alerting-protocol+xml cap+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].

Applications which use this media type: Applications that convey
alerts and warnings according to the CAP standard.

Additional information: OASIS has published the Common Alerting
Protocol at http://www.oasis-open.org/committees/
documents.php&wg_abbrev=emergency

Person & and email address to contact for further information: Hannes
Tschofenig, Hannes.Tschofenig@nsn.com

Intended usage: Limited use

Author/Change controller: IETF SIPPING ECRIT 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.

8. application/cap+xml.

8.2. IANA Registration for 425 Response Code

In the SIP Response Codes registry, the following is added

Reference: RFC-XXXX (i.e., this document)

Response code: 425 (recommended number to assign)

Default reason phrase: Bad Alert Message

Registry:
Response Code Reference
------------------------------------------ ---------
Request Failure 4xx
425 Bad Alert Message [this doc]

This SIP Response code is defined in Section 5.

8.3. IANA Registration of New AlertMsg-Error Header Field

The SIP AlertMsg-error header field is created by this document, with
its definition and rules in Section 5, to be added to the IANA sip-
parameters registry with two actions:

1. Update the Header Fields registry with

Registry:
Header Name compact Reference
----------------- ------- ---------
AlertMsg-Error [this doc]

2. In the portion titled "Header Field Parameters and Parameter
Values", add

Predefined
Header Field Parameter Name Values Reference
----------------- ------------------- ---------- ---------
AlertMsg-Error code yes [this doc]

8.4. IANA Registration for the SIP AlertMsg-Error Codes

This document creates a new registry for SIP, called "AlertMsg-Error
Codes". AlertMsg-Error codes provide reason for the error discovered
by recipients, categorized by action to be taken by error recipient.
The initial values for this registry are shown below.

Registry Name: AlertMsg-Error Codes

Reference: [this doc]

Registration Procedures: Specification Required

Code Default Reason Phrase Reference
---- --------------------------------------------------- ---------
100 "Cannot Process the Alert Payload" [this doc]

101 "Alert Payload was not present or could not be found" [this doc]

102 "Not enough information to determine
the purpose of the alert" [this doc]

103 "Alert Payload was corrupted" [this doc]

Details of these error codes are in Section 5.

9. Acknowledgments

The authors would like to thank the participants of the Early Warning
adhoc meeting at IETF#69 for their feedback. Additionally, we would
like to thank the members of the NENA Long Term Direction Working
Group for their feedback.

Additionally, we would like to thank Martin Thomson, James
Winterbottom, Shida Schubert, Bernard Aboba, and Marc Linsner for
their review comments.

10. References

9.1.

10.1. 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.

[I-D.ietf-ecrit-trustworthy-location]
Tschofenig, H., Schulzrinne, H., and B. Aboba,
"Trustworthy Location Information",
draft-ietf-ecrit-trustworthy-location-01 (work in
progress), October 2010.

9.2. Informative References

[I-D.ietf-ecrit-phonebcp]
Rosen, B. and J. Polk, "Best Current Practice for
Communications Services in support of Emergency Calling",
draft-ietf-ecrit-phonebcp-15
draft-ietf-ecrit-phonebcp-17 (work in progress),
July 2010.
March 2011.

[I-D.ietf-sipcore-location-conveyance]
Polk, J., Rosen, B., and J. Peterson, "Location Conveyance
for the Session Initiation Protocol",
draft-ietf-sipcore-location-conveyance-08 (work in
progress), May 2011.

[RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
A., Peterson, J., Sparks, R., Handley, M., and E.
Schooler, "SIP: Session Initiation Protocol", RFC 3261,
June 2002.

[RFC3311] Rosenberg, J., "The Session Initiation Protocol (SIP)
UPDATE Method", RFC 3311, October 2002.

[RFC3428] Campbell, B., Rosenberg, J., Schulzrinne, H., Huitema, C.,
and D. Gurle, "Session Initiation Protocol (SIP) Extension
for Instant Messaging", RFC 3428, December 2002.

[RFC6086] Holmberg, C., Burger, E., and H. Kaplan, "Session
Initiation Protocol (SIP) INFO Method and Package
Framework", RFC 6086, January 2011.

[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.

[RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234, January 2008.

10.2. 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 draft-ietf-atoca-requirements-01
(work in progress), September 2010. January 2011.

[I-D.ietf-ecrit-trustworthy-location]
Tschofenig, H., Schulzrinne, H., and B. Aboba,
"Trustworthy Location Information",
draft-ietf-ecrit-trustworthy-location-02 (work in
progress), May 2011.

[RFC4474] Peterson, J. and C. Jennings, "Enhancements for
Authenticated Identity Management in the Session
Initiation Protocol (SIP)", RFC 4474, August 2006.

[RFC3325] Jennings, C., Peterson, J., and M. Watson, "Private
Extensions to the Session Initiation Protocol (SIP) for
Asserted Identity within Trusted Networks", RFC 3325,
November 2002.

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