draft-ietf-ecrit-data-only-ea-18.txt   draft-ietf-ecrit-data-only-ea-19.txt 
ECRIT B. Rosen ECRIT B. Rosen
Internet-Draft Internet-Draft
Intended status: Standards Track H. Schulzrinne Intended status: Standards Track H. Schulzrinne
Expires: October 19, 2019 Columbia U. Expires: July 31, 2020 Columbia U.
H. Tschofenig H. Tschofenig
ARM Limited ARM Limited
R. Gellens R. Gellens
Core Technology Consulting Core Technology Consulting
April 17, 2019 January 28, 2020
Data-Only Emergency Calls Non-Interactive Emergency Calls
draft-ietf-ecrit-data-only-ea-18 draft-ietf-ecrit-data-only-ea-19
Abstract Abstract
RFC 6443 'Framework for Emergency Calling Using Internet Multimedia' RFC 6443 'Framework for Emergency Calling Using Internet Multimedia'
describes how devices use the Internet to place emergency calls and describes how devices use the Internet to place emergency calls and
how Public Safety Answering Points (PSAPs) handle Internet multimedia how Public Safety Answering Points (PSAPs) handle Internet multimedia
emergency calls natively. The exchange of multimedia traffic for emergency calls natively. The exchange of multimedia traffic for
emergency services involves a Session Initiation Protocol (SIP) emergency services involves a Session Initiation Protocol (SIP)
session establishment starting with a SIP INVITE that negotiates session establishment starting with a SIP INVITE that negotiates
various parameters for that session. various parameters for that session. These calls involve a person,
who uses the interactive media to communicate with the PSAP.
In some cases, however, the transmission of application data is all In some cases, however, the transmission of application data is all
that is needed. Examples of such environments include alerts issued that is needed, and no interactive media channel is established.
by a temperature sensor, burglar alarm, or chemical spill sensor. Examples of such environments include alerts issued by a temperature
Often these alerts are conveyed as one-shot data transmissions. sensor, burglar alarm, or chemical spill sensor. Often these alerts
These type of interactions are called 'data-only emergency calls'. are conveyed as one-shot data transmissions. These type of
This document describes a container for the data based on the Common interactions are called 'non-interactive emergency calls'. This
Alerting Protocol (CAP) and its transmission using the SIP MESSAGE document describes use of a SIP MESSAGE transaction containing a
transaction. container for the data based on the Common Alerting Protocol (CAP).
MESSAGE does not establish a session, which differentiates this type
of emergency request from a SIP INVITE, which would. Any device that
needs to initiate a request for emergency services where no
interactive media channel will be established would use the
mechanisms in this document.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/. Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on October 19, 2019.
This Internet-Draft will expire on July 31, 2020.
Copyright Notice Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the Copyright (c) 2020 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
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described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Architectural Overview . . . . . . . . . . . . . . . . . . . 4 3. Architectural Overview . . . . . . . . . . . . . . . . . . . 4
4. Protocol Specification . . . . . . . . . . . . . . . . . . . 6 4. Protocol Specification . . . . . . . . . . . . . . . . . . . 6
4.1. CAP Transport . . . . . . . . . . . . . . . . . . . . . . 6 4.1. CAP Transport . . . . . . . . . . . . . . . . . . . . . . 6
4.2. Profiling of the CAP Document Content . . . . . . . . . . 7 4.2. Profiling of the CAP Document Content . . . . . . . . . . 7
4.3. Sending a Data-Only Emergency Call . . . . . . . . . . . 8 4.3. Sending a non-interactive Emergency Call . . . . . . . . 8
5. Error Handling . . . . . . . . . . . . . . . . . . . . . . . 9 5. Error Handling . . . . . . . . . . . . . . . . . . . . . . . 9
5.1. 425 (Bad Alert Message) Response Code . . . . . . . . . . 9 5.1. 425 (Bad Alert Message) Response Code . . . . . . . . . . 9
5.2. The AlertMsg-Error Header Field . . . . . . . . . . . . . 9 5.2. The AlertMsg-Error Header Field . . . . . . . . . . . . . 9
6. Call Backs . . . . . . . . . . . . . . . . . . . . . . . . . 11 6. Call Backs . . . . . . . . . . . . . . . . . . . . . . . . . 11
7. Handling Large Amounts of Data . . . . . . . . . . . . . . . 11 7. Handling Large Amounts of Data . . . . . . . . . . . . . . . 11
8. Example . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 8. Example . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
9. Security Considerations . . . . . . . . . . . . . . . . . . . 15 9. Security Considerations . . . . . . . . . . . . . . . . . . . 15
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17
10.1. Registration of the 10.1. Registration of the
'application/EmergencyCallData.cap+xml' MIME type . . . 17 'application/EmergencyCallData.cap+xml' MIME type . . . 17
skipping to change at page 3, line 19 skipping to change at page 3, line 21
multimedia emergency calls natively. The exchange of multimedia multimedia emergency calls natively. The exchange of multimedia
traffic for emergency services involves a SIP session establishment traffic for emergency services involves a SIP session establishment
starting with a SIP INVITE that negotiates various parameters for starting with a SIP INVITE that negotiates various parameters for
that session. that session.
In some cases, however, there is only application data to be conveyed In some cases, however, there is only application data to be conveyed
from the end devices to a PSAP or an intermediary. Examples of such from the end devices to a PSAP or an intermediary. Examples of such
environments includes sensors issuing alerts, or certain types of environments includes sensors issuing alerts, or certain types of
medical monitors. These messages may be one-shot alerts to emergency medical monitors. These messages may be one-shot alerts to emergency
authorities and do not require establishment of a session. These authorities and do not require establishment of a session. These
type of interactions are called 'data-only emergency calls'. In this type of interactions are called 'non-interactive emergency calls'.
document, we use the term "call" so that similarities between data- In this document, we use the term "call" so that similarities between
only (non-interactive) alerts and sessions with interactive media are non-interactive alerts and sessions with interactive media are more
more obvious. obvious.
Data-only emergency calls are similar to regular emergency calls in Non-Interactive emergency calls are similar to regular emergency
the sense that they require the emergency indications, emergency call calls in the sense that they require the emergency indications,
routing functionality and may even have the same location emergency call routing functionality and may even have the same
requirements. However, the communication interaction will not lead location requirements. However, the communication interaction will
to the exchange of interactive media, that is, Real-Time Protocol not lead to the exchange of interactive media, that is, Real-Time
packets, such as voice, video data or real-time text. Protocol packets, such as voice, video data or real-time text.
The Common Alerting Protocol (CAP) [cap] is a format for exchanging The Common Alerting Protocol (CAP) [cap] is a format for exchanging
emergency alerts and public warnings. CAP is mainly used for emergency alerts and public warnings. CAP is mainly used for
conveying alerts and warnings between authorities and from conveying alerts and warnings between authorities and from
authorities to citizen/individuals. This document is concerned with authorities to citizens/individuals. This document is concerned with
citizen to authority "alerts", where the alert is a call without any citizen to authority "alerts", where the alert is a call without any
interactive media. interactive media.
This document describes a method of including a CAP message in a SIP This document describes a method of including a CAP message in a SIP
transaction by defining it as a block of "additional data" as defined transaction by defining it as a block of "additional data" as defined
in [RFC7852]. The CAP message is included either by value (the CAP in [RFC7852]. The CAP message is included either by value (the CAP
message is in the body of the message, using a CID) or by reference message is in the body of the message, using a CID) or by reference
(a URI is included in the message, which when dereferenced returns (a URI is included in the message, which when dereferenced returns
the CAP message). The additional data mechanism is also used to send the CAP message). The additional data mechanism is also used to send
alert specific data beyond that available in the CAP message. This alert specific data beyond that available in the CAP message. This
document also describes how a SIP MESSAGE [RFC3428] transaction can document also describes how a SIP MESSAGE [RFC3428] transaction can
be used to send a data-only call. be used to send a non-interactive call.
2. Terminology 2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119]. document are to be interpreted as described in [RFC2119].
SIP is the Session Initiation Protocol [RFC3261]
PIDF-LO is Presence Information Data Format - Location Object, a data
structure for carrying location [RFC4119]
LoST is the Location To Service Translation protocol [RFC5222]
CID is Content InDirection [RFC2392]
CAP is the Common Alerting Protocol [cap]
PSAP is a Public Safety Answering Point, the call center for
emergency calls.
ESRP is an Emergency Services Routing Proxy, a type of SIP Proxy
Server used in some emergency services networks
3. Architectural Overview 3. Architectural Overview
This section illustrates two envisioned usage modes: targeted and This section illustrates two envisioned usage modes: targeted and
location-based emergency alert routing. location-based emergency alert routing.
1. Emergency alerts containing only data are targeted to an 1. Emergency alerts containing only data are targeted to an
intermediary recipient responsible for evaluating the next steps. intermediary recipient responsible for evaluating the next steps.
These steps could include: These steps could include:
1. Sending a non-interactive call containing only data toward a 1. Sending a non-interactive call containing only data towards a
Public Safety Answering Point (PSAP); Public Safety Answering Point (PSAP);
2. Establishing a third-party initiated emergency call towards a 2. Establishing a third-party initiated emergency call towards a
PSAP that could include audio, video, and data. PSAP that could include audio, video, and data.
2. Emergency alerts may be targeted to a Service URN used for IP- 2. Emergency alerts may be targeted to a Service URN used for IP-
based emergency calls where the recipient is not known to the based emergency calls where the recipient is not known to the
originator. In this scenario, the alert may contain only data originator. In this scenario, the alert may contain only data
(e.g., a CAP, Geolocation header field and one or more Call-Info (e.g., a CAP, Geolocation header field and one or more Call-Info
header fields containing Additional Data [RFC7852] in a SIP header fields containing Additional Data [RFC7852] in a SIP
skipping to change at page 5, line 14 skipping to change at page 5, line 18
+------------+ +------------+ +------------+ +------------+
| Sensor | | Aggregator | | Sensor | | Aggregator |
| | | | | | | |
+---+--------+ +------+-----+ +---+--------+ +------+-----+
| | | |
Sensors | Sensors |
trigger | trigger |
emergency | emergency |
alert | alert |
| MESSAGE with CAP | | SIP MESSAGE with CAP |
|----------------------------->| |----------------------------->|
| | | |
| Aggregator | Aggregator
| processes | processes
| emergency | emergency
| alert | alert
| 200 (OK) | | SIP 200 (OK) |
|<-----------------------------| |<-----------------------------|
| | | |
| | | |
Figure 1: Targeted Emergency Alert Routing Figure 1: Targeted Emergency Alert Routing
In Figure 2 a scenario is shown whereby the alert is routed using In Figure 2 a scenario is shown whereby the alert is routed using
location information and a Service URN. An emergency services location information and a Service URN. An emergency services
routing proxy (ESRP) may use LoST to determine the next hop proxy to routing proxy (ESRP) may use LoST (a protocol defined by [RFC5222]
route the alert message to. A possible receiver is a PSAP and the which translates a location to a URI used to route an emergency call)
recipient of the alert may be a call taker. In the generic case, to determine the next hop proxy to route the alert message to. A
there is very likely no prior relationship between the originator and possible receiver is a PSAP and the recipient of the alert may be a
the receiver, e.g., a PSAP. A PSAP, for example, is likely to call taker. In the generic case, there is very likely no prior
receive and accept alerts from entities it cannot authorize. This relationship between the originator and the receiver, e.g., a PSAP.
scenario corresponds to the classic emergency services use case and A PSAP, for example, is likely to receive and accept alerts from
the description in [RFC6881] is applicable. In this use case, the entities it has no previous relationship with. This scenario
only difference between an emergency call and an emergency data-only corresponds to the classic emergency services use case and the
description in [RFC6881] is applicable. In this use case, the only
difference between an emergency call and an emergency non-interactive
call is that the former uses INVITE, creates a session, and call is that the former uses INVITE, creates a session, and
negotiates one or more media streams, while the latter uses MESSAGE, negotiates one or more media streams, while the latter uses MESSAGE,
does not create a session, and does not have interactive media. does not create a session, and does not have interactive media.
+----------+ +----------+ +-----------+ +----------+ +----------+ +-----------+
|Sensor or | | ESRP | | PSAP | |Sensor or | | ESRP | | PSAP |
|Aggregator| | | | | |Aggregator| | | | |
+----+-----+ +---+------+ +----+------+ +----+-----+ +---+------+ +----+------+
| | | | | |
Sensors | | Sensors | |
trigger | | trigger | |
emergency | | emergency | |
alert | | alert | |
| | | | | |
| | | | | |
| MESSAGE with CAP | | | SIP MESSAGE w/CAP | |
| (including Service URN, | | (including Service URN, |
| such as urn:service:sos) | | such as urn:service:sos) |
|-------------------| | |-------------------| |
| | | | | |
| ESRP performs | | ESRP performs |
| emergency alert | | emergency alert |
| routing | | routing |
| | MESSAGE with CAP | | | MESSAGE with CAP |
| | (including identity info) | | | (including identity info) |
| |----------------------------->| | |----------------------------->|
| | | | | |
| | PSAP | | PSAP
| | processes | | processes
| | emergency | | emergency
| | alert | | alert
| | 200 (OK) | | | SIP 200 (OK) |
| |<-----------------------------| | |<-----------------------------|
| | | | | |
| 200 (OK) | | | SIP 200 (OK) | |
|<------------------| | |<------------------| |
| | | | | |
| | | | | |
Figure 2: Location-Based Emergency Alert Routing Figure 2: Location-Based Emergency Alert Routing
4. Protocol Specification 4. Protocol Specification
4.1. CAP Transport 4.1. CAP Transport
A CAP message may be sent in the initial message of any SIP A CAP message may be sent in the initial message of any SIP
transaction. However, this document only addresses sending a CAP transaction. However, this document only addresses sending a CAP
message in a SIP INVITE that initiates an emergency call, or in a SIP message in a SIP MESSAGE transaction for a one-shot, non-interactive
MESSAGE transaction for a one-shot, data-only emergency call. emergency call. Behavior with other transactions is not defined.
Behavior with other transactions is not defined.
The CAP message is included in a SIP message as an additional-data The CAP message is included in a SIP message as an additional-data
block [RFC7852]. Accordingly, it is introduced to the SIP message block [RFC7852]. Accordingly, it is introduced to the SIP message
with a Call-Info header field with a purpose of with a Call-Info header field with a purpose of
"EmergencyCallData.cap". The header field may contain a URI that is "EmergencyCallData.cap". The header field may contain a URI that is
used by the recipient (or in some cases, an intermediary) to obtain used by the recipient (or in some cases, an intermediary) to obtain
the CAP message. Alternative, the Call-Info header field may contain the CAP message. Alternative, the Call-Info header field may contain
a Content Indirect url [RFC2392] and the CAP message included in the a Content Indirect url [RFC2392] and the CAP message included in the
body of the message. In the latter case, the CAP message is located body of the message. In the latter case, the CAP message is located
in a MIME block of the type 'application/emergencyCallData.cap+xml'. in a MIME block of the type 'application/emergencyCallData.cap+xml'.
skipping to change at page 7, line 38 skipping to change at page 7, line 35
4.2. Profiling of the CAP Document Content 4.2. Profiling of the CAP Document Content
The usage of CAP MUST conform to the specification provided with The usage of CAP MUST conform to the specification provided with
[cap]. For usage with SIP the following additional requirements are [cap]. For usage with SIP the following additional requirements are
imposed: imposed:
sender: The following restrictions and conditions apply to setting sender: The following restrictions and conditions apply to setting
the value of the <sender> element: the value of the <sender> element:
Originator is a SIP entity, Author indication irrelevant: When * Originator is a SIP entity, Author indication irrelevant: When
the alert was created by a SIP-based originator and it is not the alert was created by a SIP-based originator and it is not
useful to be explicit about the author of the alert, then the useful to be explicit about the author of the alert, then the
<sender> element MUST be populated with the SIP URI of the user <sender> element MUST be populated with the SIP URI of the user
agent. agent.
Originator is a non-SIP entity, Author indication irrelevant: * Originator is a non-SIP entity, Author indication irrelevant:
When the alert was created by a non-SIP based entity and the When the alert was created by a non-SIP based entity and the
identity of this original sender is to be preserved, then this identity of this original sender is to be preserved, then this
identity MUST be placed into the <sender> element. In this identity MUST be placed into the <sender> element. In this
situation it is not useful to be explicit about the author of the situation it is not useful to be explicit about the author of
alert. The specific type of identity being used will depend on the alert. The specific type of identity being used will
the technology used by the original originator. depend on the technology used by the original originator.
Author indication relevant: When the author is different from the * Author indication relevant: When the author is different from
actual originator of the message and this distinction should be the actual originator of the message and this distinction
preserved, then the <sender> element MUST NOT contain the SIP URI should be preserved, then the <sender> element MUST NOT contain
of the user agent. the SIP URI of the user agent.
incidents: The <incidents> element MUST be present. This incident incidents: The <incidents> element MUST be present. This incident
identifier MUST be chosen in such a way that it is unique for a identifier MUST be chosen in such a way that it is unique for a
given <sender, expires, incidents> combination. Note that the given <sender, expires, incidents> combination. Note that the
<expires> element is optional and may not be present. <expires> element is optional and may not be present.
scope: The value of the <scope> element MAY be set to "Private" if scope: The value of the <scope> element MAY be set to "Private" if
the alert is not meant for public consumption. The <addresses> the alert is not meant for public consumption. The <addresses>
element is, however, not used by this specification since the element is, however, not used by this specification since the
message routing is performed by SIP and the respective address message routing is performed by SIP and the respective address
information is already available in other SIP header fields. information is already available in other SIP header fields.
Populating information twice into different parts of the message Populating information twice into different parts of the message
may lead to inconsistency. may lead to inconsistency.
parameter: The <parameter> element MAY contain additional parameter: The <parameter> element MAY contain additional
information specific to the sender. information specific to the sender, conforming to the CAP message
syntax.
area: It is RECOMMENDED to omit this element when constructing a area: It is RECOMMENDED to omit this element when constructing a
message. If the CAP message already contains an <area> element, message. If the CAP message already contains an <area> element,
then the specified location information SHOULD be copied into a then the specified location information SHOULD be copied into a
PIDF-LO structure referenced by the 'geolocation' header field. PIDF-LO structure (the data format for location used by emergency
If there is a need to copy the PIDF-LO structure referenced by calls on the Internet) referenced by the SIP 'Geolocation' header
'geolocation' to <area>, implementers must be aware that <area> is field. If there is a need to copy the PIDF-LO structure
limited to a circle or polygon, and conversion of other shapes referenced by 'geolocation' to <area>, implementers must be aware
will be required. Points SHOULD be converted to a circle with a that <area> is limited to a circle or polygon, and conversion of
radius equal to the uncertainty of the point. Arc-bands and other shapes will be required. Points SHOULD be converted to a
ellipses SHOULD be converted to an equivalent polygon. 3D circle with a radius equal to the uncertainty of the point. Arc-
locations SHOULD be converted to their equivalent 2D forms. bands and ellipses SHOULD be converted to an equivalent polygon.
3D locations SHOULD be converted to their equivalent 2D forms.
4.3. Sending a Data-Only Emergency Call 4.3. Sending a non-interactive Emergency Call
A data-only emergency call is sent using a SIP MESSAGE transaction A non-interactive emergency call is sent using a SIP MESSAGE
with a CAP URI or body part as described above in a manner similar to transaction with a CAP URI or body part as described above in a
how an emergency call with interactive media is sent, as described in manner similar to how an emergency call with interactive media is
[RFC6881]. The MESSAGE transaction does not create a session nor sent, as described in [RFC6881]. The MESSAGE transaction does not
establish interactive media streams, but otherwise, the header create a session nor establish interactive media streams, but
content of the transaction, routing, and processing of data-only otherwise, the header content of the transaction, routing, and
calls are the same as those of other emergency calls. processing of non-interactive calls are the same as those of other
emergency calls.
5. Error Handling 5. Error Handling
This section defines a new error response code and a header field for This section defines a new error response code and a header field for
additional information. additional information.
5.1. 425 (Bad Alert Message) Response Code 5.1. 425 (Bad Alert Message) Response Code
This SIP extension creates a new location-specific response code, This SIP extension creates a new location-specific response code,
defined as follows: defined as follows:
425 (Bad Alert Message) 425 (Bad Alert Message)
The 425 response code is a rejection of the request due to its The 425 response code is a rejection of the request due to its
included alert content, indicating that it was malformed or not included alert content, indicating that it was malformed or not
satisfactory for the recipient's purpose. satisfactory for the recipient's purpose.
A SIP intermediary can also reject an alert it receives from a User A SIP intermediary can also reject an alert it receives from a User
Agent (UA) when it understands that the provided alert is malformed. Agent (UA) when it detects that the provided alert is malformed.
Section 5.2 describes an AlertMsg-Error header field with more Section 5.2 describes an AlertMsg-Error header field with more
details about what was wrong with the alert message in the request. details about what was wrong with the alert message in the request.
This header field MUST be included in the 425 response. This header field MUST be included in the 425 response.
It is only appropriate to generate a 425 response when the responding It is only appropriate to generate a 425 response when the responding
entity has no other information in the request that is usable by the entity has no other information in the request that is usable by the
responder. responder.
A 425 response code MUST NOT be sent in response to a request that A 425 response code MUST NOT be sent in response to a request that
skipping to change at page 10, line 25 skipping to change at page 10, line 25
HCOLON, SEMI, and EQUAL are defined in [RFC3261]. DIGIT is defined HCOLON, SEMI, and EQUAL are defined in [RFC3261]. DIGIT is defined
in [RFC5234]. in [RFC5234].
The AlertMsg-Error header field MUST contain only one ErrorValue to The AlertMsg-Error header field MUST contain only one ErrorValue to
indicate what was wrong with the alert payload the recipient indicate what was wrong with the alert payload the recipient
determined was bad. determined was bad.
The ErrorValue contains a 3-digit error code indicating what was The ErrorValue contains a 3-digit error code indicating what was
wrong with the alert in the request. This error code has a wrong with the alert in the request. This error code has a
corresponding quoted error text string that is human understandable. corresponding quoted error text string that is human readable. The
The text string is OPTIONAL, but RECOMMENDED for human readability, text string is OPTIONAL, but RECOMMENDED for human readability,
similar to the string phrase used for SIP response codes. That said, similar to the string phrase used for SIP response codes. That said,
the strings are complete enough for rendering to the user, if so the strings are complete enough for rendering to the user, if so
desired. The strings in this document are recommendations, and are desired. The strings in this document are recommendations, and are
not standardized -- meaning an operator can change the strings -- but not standardized -- meaning an operator can change the strings -- but
MUST NOT change the meaning of the error code. Similar to how RFC 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 3261 specifies, there MUST NOT be more than one string per error
code. code.
The AlertMsg-Error header field MAY be included in any response if an The AlertMsg-Error header field MAY be included in any response if an
alert message was in the request part of the same transaction. For alert message was in the request part of the same transaction. For
skipping to change at page 11, line 24 skipping to change at page 11, line 24
AlertMsg-Error: 103 ; code="Alert Payload was corrupted" AlertMsg-Error: 103 ; code="Alert Payload was corrupted"
Additionally, if an entity cannot or chooses not to process the alert Additionally, if an entity cannot or chooses not to process the alert
message from a SIP request, a 500 (Server Internal Error) SHOULD be message from a SIP request, a 500 (Server Internal Error) SHOULD be
used with or without a configurable Retry-After header field. used with or without a configurable Retry-After header field.
6. Call Backs 6. Call Backs
This document does not describe any method for the recipient to call This document does not describe any method for the recipient to call
back the sender of a data-only call. Usually, these alerts are sent back the sender of a non-interactive call. Usually, these alerts are
by automata, which do not have a mechanism to receive calls of any sent by automata, which do not have a mechanism to receive calls of
kind. The identifier in the 'From' header field may be useful to any kind. The identifier in the 'From' header field may be useful to
obtain more information, but any such mechanism is not defined in obtain more information, but any such mechanism is not defined in
this document. The CAP message may contain related contact this document. The CAP message may contain related contact
information for the sender. information for the sender.
7. Handling Large Amounts of Data 7. Handling Large Amounts of Data
It is not atypical for sensors to have large quantities of data that It is not atypical for sensors to have large quantities of data that
they may wish to send. Including large amounts of data in a MESSAGE they may wish to send. Including large amounts of data (tens of
is not advisable, because SIP entities are usually not equipped to kilobytes) in a MESSAGE is not advisable, because SIP entities are
handle very large messages. In such cases, the sender SHOULD make usually not equipped to handle very large messages. In such cases,
use of the by-reference mechanisms defined in [RFC7852], which the sender SHOULD make use of the by-reference mechanisms defined in
involves making the data available via HTTPS (either at the [RFC7852], which involves making the data available via HTTPS (either
originator or at another entity), placing a URI to the data in the at the originator or at another entity), placing a URI to the data in
'Call-Info' header field, and the recipient using HTTPS to retrieve the 'Call-Info' header field, and the recipient uses HTTPS to
the data. The CAP message itself can be sent by-reference using this retrieve the data. The CAP message itself can be sent by-reference
mechanism, as well as any or all of the Additional Data blocks that using this mechanism, as well as any or all of the Additional Data
may contain sensor-specific data. blocks that may contain sensor-specific data.
8. Example 8. Example
The following example shows a CAP document indicating a BURGLARY The following example shows a CAP document indicating a BURGLARY
alert issued by a sensor called 'sensor1@example.com'. The location alert issued by a sensor called 'sensor1@example.com'. The location
of the sensor can be obtained from the attached location information of the sensor can be obtained from the attached location information
provided via the 'geolocation' header field contained in the SIP provided via the 'geolocation' header field contained in the SIP
MESSAGE structure. Additionally, the sensor provided some data along MESSAGE structure. Additionally, the sensor provided some data along
with the alert message, using proprietary information elements with the alert message, using proprietary information elements
intended only to be processed by the receiver, a SIP entity acting as intended only to be processed by the receiver, a SIP entity acting as
skipping to change at page 13, line 48 skipping to change at page 13, line 48
</gp:usage-rules> </gp:usage-rules>
<gp:method>802.11</gp:method> <gp:method>802.11</gp:method>
</gp:geopriv> </gp:geopriv>
<dm:timestamp>2010-11-04T20:57:29Z</dm:timestamp> <dm:timestamp>2010-11-04T20:57:29Z</dm:timestamp>
</dm:device> </dm:device>
</presence> </presence>
--boundary1-- --boundary1--
Figure 3: Example Message conveying an Alert to an aggregator Figure 3: Example Message conveying an Alert to an aggregator
The following shows the same CAP document sent as a data-only The following shows the same CAP document sent as a non-interactive
emergency call towards a PSAP. emergency call towards a PSAP.
MESSAGE urn:service:sos SIP/2.0 MESSAGE urn:service:sos SIP/2.0
Via: SIP/2.0/TCP sip:aggreg.1.example.com;branch=z9hG4bK776abssa Via: SIP/2.0/TCP sip:aggreg.1.example.com;branch=z9hG4bK776abssa
Max-Forwards: 70 Max-Forwards: 70
From: sip:aggregator@example.com;tag=32336 From: sip:aggregator@example.com;tag=32336
To: 112 To: 112
Call-ID: asdf33443a@example.com Call-ID: asdf33443a@example.com
Route: sip:psap1.example.gov Route: sip:psap1.example.gov
Geolocation: <cid:abcdef@example.com> Geolocation: <cid:abcdef@example.com>
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indicated timeframe is able to detect a replayed message and, if the indicated timeframe is able to detect a replayed message and, if the
content of that message is unchanged, then no additional security content of that message is unchanged, then no additional security
vulnerability is created. Additionally, it is RECOMMENDED to make vulnerability is created. Additionally, it is RECOMMENDED to make
use of SIP security mechanisms, such as SIP Identity [RFC8224], to use of SIP security mechanisms, such as SIP Identity [RFC8224], to
tie the CAP message to the SIP message. To provide protection of the tie the CAP message to the SIP message. To provide protection of the
entire SIP message exchange between neighboring SIP entities, the entire SIP message exchange between neighboring SIP entities, the
usage of TLS is REQUIRED. usage of TLS is REQUIRED.
Note that none of the security mechanism in this document protect Note that none of the security mechanism in this document protect
against a compromised sensor sending crafted alerts. Privacy against a compromised sensor sending crafted alerts. Privacy
provided for any emergency calls, including data-only messages, is provided for any emergency calls, including non-interactive messages,
subject to local regulations. is subject to local regulations.
10. IANA Considerations 10. IANA Considerations
10.1. Registration of the 'application/EmergencyCallData.cap+xml' MIME 10.1. Registration of the 'application/EmergencyCallData.cap+xml' MIME
type type
To: ietf-types@iana.org To: ietf-types@iana.org
Subject: Registration of MIME media type application/ Subject: Registration of MIME media type application/
EmergencyCallData.cap+xml EmergencyCallData.cap+xml
skipping to change at page 21, line 11 skipping to change at page 21, line 11
Schooler, "SIP: Session Initiation Protocol", RFC 3261, Schooler, "SIP: Session Initiation Protocol", RFC 3261,
DOI 10.17487/RFC3261, June 2002, DOI 10.17487/RFC3261, June 2002,
<https://www.rfc-editor.org/info/rfc3261>. <https://www.rfc-editor.org/info/rfc3261>.
[RFC3428] Campbell, B., Ed., Rosenberg, J., Schulzrinne, H., [RFC3428] Campbell, B., Ed., Rosenberg, J., Schulzrinne, H.,
Huitema, C., and D. Gurle, "Session Initiation Protocol Huitema, C., and D. Gurle, "Session Initiation Protocol
(SIP) Extension for Instant Messaging", RFC 3428, (SIP) Extension for Instant Messaging", RFC 3428,
DOI 10.17487/RFC3428, December 2002, DOI 10.17487/RFC3428, December 2002,
<https://www.rfc-editor.org/info/rfc3428>. <https://www.rfc-editor.org/info/rfc3428>.
[RFC4119] Peterson, J., "A Presence-based GEOPRIV Location Object
Format", RFC 4119, DOI 10.17487/RFC4119, December 2005,
<https://www.rfc-editor.org/info/rfc4119>.
[RFC5222] Hardie, T., Newton, A., Schulzrinne, H., and H.
Tschofenig, "LoST: A Location-to-Service Translation
Protocol", RFC 5222, DOI 10.17487/RFC5222, August 2008,
<https://www.rfc-editor.org/info/rfc5222>.
[RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax [RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234, Specifications: ABNF", STD 68, RFC 5234,
DOI 10.17487/RFC5234, January 2008, DOI 10.17487/RFC5234, January 2008,
<https://www.rfc-editor.org/info/rfc5234>. <https://www.rfc-editor.org/info/rfc5234>.
[RFC7303] Thompson, H. and C. Lilley, "XML Media Types", RFC 7303, [RFC7303] Thompson, H. and C. Lilley, "XML Media Types", RFC 7303,
DOI 10.17487/RFC7303, July 2014, DOI 10.17487/RFC7303, July 2014,
<https://www.rfc-editor.org/info/rfc7303>. <https://www.rfc-editor.org/info/rfc7303>.
[RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO [RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO
skipping to change at page 22, line 20 skipping to change at page 22, line 26
[RFC6443] Rosen, B., Schulzrinne, H., Polk, J., and A. Newton, [RFC6443] Rosen, B., Schulzrinne, H., Polk, J., and A. Newton,
"Framework for Emergency Calling Using Internet "Framework for Emergency Calling Using Internet
Multimedia", RFC 6443, DOI 10.17487/RFC6443, December Multimedia", RFC 6443, DOI 10.17487/RFC6443, December
2011, <https://www.rfc-editor.org/info/rfc6443>. 2011, <https://www.rfc-editor.org/info/rfc6443>.
Authors' Addresses Authors' Addresses
Brian Rosen Brian Rosen
470 Conrad Dr 470 Conrad Dr
Mars, PA 16046 Mars, PA 16046
US US
Phone:
Email: br@brianrosen.net Email: br@brianrosen.net
Henning Schulzrinne Henning Schulzrinne
Columbia University Columbia University
Department of Computer Science Department of Computer Science
450 Computer Science Building 450 Computer Science Building
New York, NY 10027 New York, NY 10027
US US
Phone: +1 212 939 7004 Phone: +1 212 939 7004
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