< 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
	Provisions Relating to IETF Documents		Provisions Relating to IETF Documents
	(https://trustee.ietf.org/license-info) in effect on the date of		(https://trustee.ietf.org/license-info) in effect on the date of
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	to this document. Code Components extracted from this document must		to this document. Code Components extracted from this document must
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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>
	skipping to change at page 17, line 7 ¶		skipping to change at page 17, line 7 ¶
	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
End of changes. 38 change blocks.
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