draft-ietf-cdni-control-triggers-15.txt		rfc8007.txt
	Network Working Group R. Murray		Internet Engineering Task Force (IETF) R. Murray
	Internet-Draft B. Niven-Jenkins		Request for Comments: 8007 B. Niven-Jenkins
	Intended status: Standards Track Nokia		Category: Standards Track Nokia
	Expires: November 20, 2016 May 19, 2016		ISSN: 2070-1721 December 2016
	CDNI Control Interface / Triggers		Content Delivery Network Interconnection (CDNI)
	draft-ietf-cdni-control-triggers-15		Control Interface / Triggers
	Abstract		Abstract
	This document describes the part of the CDN Interconnection Control		This document describes the part of the Content Delivery Network
	Interface that allows a CDN to trigger activity in an interconnected		Interconnection (CDNI) Control interface that allows a CDN to trigger
	CDN that is configured to deliver content on its behalf. The		activity in an interconnected CDN that is configured to deliver
	upstream CDN can use this mechanism to request that the downstream		content on its behalf. The upstream CDN can use this mechanism to
	CDN pre-positions metadata or content, or that it invalidates or		request that the downstream CDN pre-position metadata or content or
	purges metadata or content. The upstream CDN can monitor the status		to request that it invalidate or purge metadata or content. The
	of activity that it has triggered in the downstream CDN.		upstream CDN can monitor the status of activity that it has triggered
			in the downstream CDN.
	Requirements Language
	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].
	Status of This Memo		Status of This Memo
	This Internet-Draft is submitted in full conformance with the		This is an Internet Standards Track document.
	provisions of BCP 78 and BCP 79.
	Internet-Drafts are working documents of the Internet Engineering
	Task Force (IETF). Note that other groups may also distribute
	working documents as Internet-Drafts. The list of current Internet-
	Drafts is at http://datatracker.ietf.org/drafts/current/.
	Internet-Drafts are draft documents valid for a maximum of six months		This document is a product of the Internet Engineering Task Force
	and may be updated, replaced, or obsoleted by other documents at any		(IETF). It represents the consensus of the IETF community. It has
	time. It is inappropriate to use Internet-Drafts as reference		received public review and has been approved for publication by the
	material or to cite them other than as "work in progress."		Internet Engineering Steering Group (IESG). Further information on
			Internet Standards is available in Section 2 of RFC 7841.
	This Internet-Draft will expire on November 20, 2016.		Information about the current status of this document, any errata,
			and how to provide feedback on it may be obtained at
			http://www.rfc-editor.org/info/rfc8007.
	Copyright Notice		Copyright Notice
	Copyright (c) 2016 IETF Trust and the persons identified as the		Copyright (c) 2016 IETF Trust and the persons identified as the
	document authors. All rights reserved.		document authors. All rights reserved.
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	(http://trustee.ietf.org/license-info) in effect on the date of		(http://trustee.ietf.org/license-info) in effect on the date of
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	carefully, as they describe your rights and restrictions with respect		carefully, as they describe your rights and restrictions with respect
	to this document. Code Components extracted from this document must		to this document. Code Components extracted from this document must
	include Simplified BSD License text as described in Section 4.e of		include Simplified BSD License text as described in Section 4.e of
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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
	1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4		1.1. Terminology ................................................4
	2. Model for CDNI Triggers . . . . . . . . . . . . . . . . . . . 4		2. Model for CDNI Triggers .........................................4
	2.1. Timing of Triggered Activity . . . . . . . . . . . . . . 6		2.1. Timing of Triggered Activity ...............................6
	2.2. Scope of Triggered Activity . . . . . . . . . . . . . . . 6		2.2. Scope of Triggered Activity ................................7
	2.2.1. Multiple Interconnected CDNs . . . . . . . . . . . . 7		2.2.1. Multiple Interconnected CDNs ........................7
	2.3. Trigger Results . . . . . . . . . . . . . . . . . . . . . 8		2.3. Trigger Results ............................................8
	3. Collections of Trigger Status Resources . . . . . . . . . . . 8		3. Collections of Trigger Status Resources .........................9
	4. CDNI Trigger Interface . . . . . . . . . . . . . . . . . . . 9		4. CDNI Trigger Interface .........................................10
	4.1. Creating Triggers . . . . . . . . . . . . . . . . . . . . 10		4.1. Creating Triggers .........................................11
	4.2. Checking Status . . . . . . . . . . . . . . . . . . . . . 11		4.2. Checking Status ...........................................12
	4.2.1. Polling Trigger Status Resource collections . . . . . 12		4.2.1. Polling Trigger Status Resource Collections ........12
	4.2.2. Polling Trigger Status Resources . . . . . . . . . . 12		4.2.2. Polling Trigger Status Resources ...................13
	4.3. Cancelling Triggers . . . . . . . . . . . . . . . . . . . 12		4.3. Canceling Triggers ........................................13
	4.4. Deleting Triggers . . . . . . . . . . . . . . . . . . . . 13		4.4. Deleting Triggers .........................................14
	4.5. Expiry of Trigger Status Resources . . . . . . . . . . . 14		4.5. Expiry of Trigger Status Resources ........................14
	4.6. Loop Detection and Prevention . . . . . . . . . . . . . . 14		4.6. Loop Detection and Prevention .............................15
	4.7. Error Handling . . . . . . . . . . . . . . . . . . . . . 15		4.7. Error Handling ............................................15
	4.8. Content URLs . . . . . . . . . . . . . . . . . . . . . . 16		4.8. Content URLs ..............................................16
	5. CI/T Object Properties and Encoding . . . . . . . . . . . . . 16		5. CI/T Object Properties and Encoding ............................17
	5.1. CI/T Objects . . . . . . . . . . . . . . . . . . . . . . 16		5.1. CI/T Objects ..............................................17
	5.1.1. CI/T Commands . . . . . . . . . . . . . . . . . . . . 16		5.1.1. CI/T Commands ......................................17
	5.1.2. Trigger Status Resource . . . . . . . . . . . . . . . 17		5.1.2. Trigger Status Resources ...........................18
	5.1.3. Trigger Collection . . . . . . . . . . . . . . . . . 19		5.1.3. Trigger Collections ................................20
	5.2. Properties of CI/T Objects . . . . . . . . . . . . . . . 20		5.2. Properties of CI/T Objects ................................21
	5.2.1. Trigger Specification . . . . . . . . . . . . . . . . 20		5.2.1. Trigger Specification ..............................21
	5.2.2. Trigger Type . . . . . . . . . . . . . . . . . . . . 21		5.2.2. Trigger Type .......................................23
	5.2.3. Trigger Status . . . . . . . . . . . . . . . . . . . 22		5.2.3. Trigger Status .....................................24
	5.2.4. PatternMatch . . . . . . . . . . . . . . . . . . . . 23		5.2.4. PatternMatch .......................................24
	5.2.5. Absolute Time . . . . . . . . . . . . . . . . . . . . 24		5.2.5. Absolute Time ......................................25
	5.2.6. Error Description . . . . . . . . . . . . . . . . . . 24		5.2.6. Error Description ..................................26
	5.2.7. Error Code . . . . . . . . . . . . . . . . . . . . . 25		5.2.7. Error Code .........................................26
	6. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 26		6. Examples .......................................................27
	6.1. Creating Triggers . . . . . . . . . . . . . . . . . . . . 26		6.1. Creating Triggers .........................................28
	6.1.1. Preposition . . . . . . . . . . . . . . . . . . . . . 26		6.1.1. Preposition ........................................28
	6.1.2. Invalidate . . . . . . . . . . . . . . . . . . . . . 28		6.1.2. Invalidate .........................................30
			6.2. Examining Trigger Status ..................................32
			6.2.1. Collection of All Triggers .........................32
			6.2.2. Filtered Collections of Trigger Status Resources ...33
			6.2.3. Individual Trigger Status Resources ................34
			6.2.4. Polling for Changes in Status ......................36
			6.2.5. Deleting Trigger Status Resources ..................38
			6.2.6. Error Reporting ....................................39
	6.2. Examining Trigger Status . . . . . . . . . . . . . . . . 29		7. IANA Considerations ............................................40
	6.2.1. Collection of All Triggers . . . . . . . . . . . . . 29		7.1. CDNI Payload Type Parameter Registrations .................40
	6.2.2. Filtered Collections of Trigger Status Resources . . 30		7.2. "CDNI CI/T Trigger Types" Registry ........................41
	6.2.3. Individual Trigger Status Resources . . . . . . . . . 32		7.3. "CDNI CI/T Error Codes" Registry ..........................41
	6.2.4. Polling for Change . . . . . . . . . . . . . . . . . 34		8. Security Considerations ........................................41
	6.2.5. Deleting Trigger Status Resources . . . . . . . . . . 37		8.1. Authentication, Authorization, Confidentiality,
	6.2.6. Error Reporting . . . . . . . . . . . . . . . . . . . 38		Integrity Protection ......................................42
	7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 39		8.2. Denial of Service .........................................43
	7.1. CDNI Payload Type Parameter Registrations . . . . . . . . 40		8.3. Privacy ...................................................44
	7.2. CDNI CI/T Trigger Types Registry . . . . . . . . . . . . 40		9. References .....................................................44
	7.3. CDNI CI/T Error Codes Registry . . . . . . . . . . . . . 40		9.1. Normative References ......................................44
	8. Security Considerations . . . . . . . . . . . . . . . . . . . 41		9.2. Informative References ....................................45
	8.1. Authentication, Authorization, Confidentiality, Integrity		Appendix A. Formalization of the JSON Data ........................47
	Protection . . . . . . . . . . . . . . . . . . . . . . . 41		Acknowledgments ...................................................49
	8.2. Denial of Service . . . . . . . . . . . . . . . . . . . . 42		Authors' Addresses ................................................49
	8.3. Privacy . . . . . . . . . . . . . . . . . . . . . . . . . 43
	9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 43
	10. References . . . . . . . . . . . . . . . . . . . . . . . . . 43
	10.1. Normative References . . . . . . . . . . . . . . . . . . 43
	10.2. Informative References . . . . . . . . . . . . . . . . . 44
	Appendix A. Formalization of the JSON Data . . . . . . . . . . . 45
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 46
	1. Introduction		1. Introduction
	[RFC6707] introduces the problem scope for CDN Interconnection (CDNI)		[RFC6707] introduces the problem scope for Content Delivery Network
	and lists the four categories of interfaces that may be used to		Interconnection (CDNI) and lists the four categories of interfaces
	compose a CDNI solution (Control, Metadata, Request Routing,		that may be used to compose a CDNI solution (Control, Metadata,
	Logging).		Request Routing, and Logging).
	[RFC7336] expands on the information provided in [RFC6707] and		[RFC7336] expands on the information provided in [RFC6707] and
	describes each of the interfaces and the relationships between them		describes each of the interfaces and the relationships between them
	in more detail.		in more detail.
	This document describes the "CI/T" interface, "CDNI Control interface		This document describes the "CI/T" interface -- "CDNI Control
	/ Triggers". It does not consider those parts of the control		interface / Triggers". It does not consider those parts of the
	interface that relate to configuration, bootstrapping or		Control interface that relate to configuration, bootstrapping, or
	authentication of CDN Interconnect interfaces. Section 4 of		authentication of CDN Interconnect interfaces. Section 4 of
	[RFC7337] identifies the requirements specific to the CI interface,		[RFC7337] identifies the requirements specific to the CI/T interface;
	requirements applicable to the CI/T interface are CI-1 to CI-6.		requirements applicable to the CI/T interface are CI-1 to CI-6.
	o Section 2 outlines the model for the CI/T Interface at a high		o Section 2 outlines the model for the CI/T interface at a high
	level.		level.
	o Section 3 describes collections of Trigger Status Resources.		o Section 3 describes collections of Trigger Status Resources.
	o Section 4 defines the web service provided by the dCDN.		o Section 4 defines the web service provided by the downstream CDN.
	o Section 5 lists properties of CI/T Commands and Status Resources.		o Section 5 lists properties of CI/T Commands and Status Resources.
	o Section 6 contains example messages.		o Section 6 contains example messages.
	1.1. Terminology		1.1. Terminology
	This document reuses the terminology defined in [RFC6707] and uses		This document reuses the terminology defined in [RFC6707] and uses
	"uCDN" and "dCDN" as shorthand for "Upstream CDN" and "Downstream		"uCDN" and "dCDN" as shorthand for "upstream CDN" and "downstream
	CDN", respectively.		CDN", respectively.
			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].
	2. Model for CDNI Triggers		2. Model for CDNI Triggers
	A CI/T Command, sent from the uCDN to the dCDN, is a request for the		A CI/T Command, sent from the uCDN to the dCDN, is a request for the
	dCDN to do some work relating to data associated with content		dCDN to do some work relating to data associated with content
	requests originating from the uCDN.		requests originating from the uCDN.
	There are two types of CI/T Command: CI/T Trigger Commands, and CI/T		There are two types of CI/T Commands: CI/T Trigger Commands and CI/T
	Cancel Commands. The CI/T Cancel Command can be used to request		Cancel Commands. The CI/T Cancel Command can be used to request
	cancellation of an earlier CI/T Trigger Command. A CI/T Trigger		cancellation of an earlier CI/T Trigger Command. A CI/T Trigger
	Command is of one of the following types:		Command is of one of the following types:
	o preposition - used to instruct the dCDN to fetch metadata from the		o preposition - used to instruct the dCDN to fetch metadata from the
	uCDN, or content from any origin including the uCDN.		uCDN, or content from any origin including the uCDN.
	o invalidate - used to instruct the dCDN to revalidate specific		o invalidate - used to instruct the dCDN to revalidate specific
	metadata or content before re-using it.		metadata or content before reusing it.
	o purge - used to instruct the dCDN to delete specific metadata or		o purge - used to instruct the dCDN to delete specific metadata or
	content.		content.
	The CI/T interface is a web service offered by the dCDN. It allows		The CI/T interface is a web service offered by the dCDN. It allows
	CI/T commands to be issued, and triggered activity to be tracked.		CI/T Commands to be issued and allows triggered activity to be
	The CI/T interface builds on top of HTTP/1.1 [RFC7230]. References		tracked. The CI/T interface builds on top of HTTP/1.1 [RFC7230].
	to URL in this document relate to http/https URIs, as defined in		References to URL in this document relate to HTTP/HTTPS URIs, as
	[RFC7230] section 2.7.		defined in Section 2.7 of [RFC7230].
	When the dCDN accepts a CI/T Command it creates a resource describing		When the dCDN accepts a CI/T Command, it creates a resource
	status of the triggered activity, a Trigger Status Resource. The		describing the status of the triggered activity -- a Trigger Status
	uCDN can poll Trigger Status Resources to monitor progress.		Resource. The uCDN can poll Trigger Status Resources to monitor
			progress.
	The dCDN maintains at least one collection of Trigger Status		The dCDN maintains at least one collection of Trigger Status
	Resources for each uCDN. Each uCDN only has access to its own		Resources for each uCDN. Each uCDN only has access to its own
	collections, the locations of which are shared when CDN		collections, the locations of which are shared when CDNI is
	interconnection is established.		established.
	To trigger activity in the dCDN, the uCDN POSTs a CI/T Command to the		To trigger activity in the dCDN, the uCDN POSTs a CI/T Command to the
	collection of Trigger Status Resources. If the dCDN accepts the CI/T		collection of Trigger Status Resources. If the dCDN accepts the CI/T
	Command, it creates a new Trigger Status Resource and returns its		Command, it creates a new Trigger Status Resource and returns its
	location to the uCDN. To monitor progress, the uCDN can GET the		location to the uCDN. To monitor progress, the uCDN can GET the
	Trigger Status Resource. To request cancellation of a CI/T Trigger		Trigger Status Resource. To request cancellation of a CI/T Trigger
	Command the uCDN can POST to the collection of Trigger Status		Command, the uCDN can POST to the collection of Trigger Status
	Resources, or simply DELETE the Trigger Status Resource.		Resources or simply delete the Trigger Status Resource.
	In addition to the collection of all Trigger Status Resources for the		In addition to the collection of all Trigger Status Resources for the
	uCDN, the dCDN can maintain filtered views of that collection. These		uCDN, the dCDN can maintain filtered views of that collection. These
	filtered views are defined in Section 3 and include collections of		filtered views are defined in Section 3 and include collections of
	Trigger Status Resources corresponding to active and completed CI/T		Trigger Status Resources corresponding to active and completed CI/T
	Trigger Commands. These collections provide a mechanism for polling		Trigger Commands. These collections provide a mechanism for polling
	the status of multiple jobs.		the status of multiple jobs.
	Figure 1 is an example showing the basic message flow used by the		Figure 1 is an example showing the basic message flow used by the
	uCDN to trigger activity in the dCDN, and for the uCDN to discover		uCDN to trigger activity in the dCDN and for the uCDN to discover the
	the status of that activity. Only successful triggering is shown.		status of that activity. Only successful triggering is shown.
	Examples of the messages are given in Section 6.		Examples of the messages are given in Section 6.
	uCDN dCDN		uCDN dCDN
	| (1) POST https://dcdn.example.com/triggers/uCDN |		| (1) POST https://dcdn.example.com/triggers/uCDN |
	[ ] --------------------------------------------------> [ ]--+		[ ] --------------------------------------------------> [ ]--+
	| [ ] | (2)		| [ ] | (2)
	| (3) HTTP 201 Response [ ]<-+		| (3) HTTP 201 Response [ ]<-+
	[ ] <-------------------------------------------------- [ ]		[ ] <-------------------------------------------------- [ ]
	| Loc: https://dcdn.example.com/triggers/uCDN/123 |		| Loc: https://dcdn.example.com/triggers/uCDN/123 |
	| |		| |
	skipping to change at page 5, line 43 ¶		skipping to change at page 6, line 5 ¶
	| (4) GET https://dcdn.example.com/triggers/uCDN/123 |		| (4) GET https://dcdn.example.com/triggers/uCDN/123 |
	[ ] --------------------------------------------------> [ ]		[ ] --------------------------------------------------> [ ]
	| [ ]		| [ ]
	| (5) HTTP 200 Trigger Status Resource [ ]		| (5) HTTP 200 Trigger Status Resource [ ]
	[ ] <-------------------------------------------------- [ ]		[ ] <-------------------------------------------------- [ ]
	| |		| |
	| |		| |
	Figure 1: Basic CDNI Message Flow for Triggers		Figure 1: Basic CDNI Message Flow for Triggers
	The steps in Figure 1 are:		The steps in Figure 1 are as follows:
	1. The uCDN triggers action in the dCDN by posting a CI/T Command to		1. The uCDN triggers action in the dCDN by POSTing a CI/T Command to
	a collection of Trigger Status Resources,		a collection of Trigger Status Resources --
	"https://dcdn.example.com/triggers/uCDN". The URL of this was		"https://dcdn.example.com/triggers/uCDN". This URL was given to
	given to the uCDN when the CI/T interface was established.		the uCDN when the CI/T interface was established.
	2. The dCDN authenticates the request, validates the CI/T Command		2. The dCDN authenticates the request, validates the CI/T Command,
	and, if it accepts the request, creates a new Trigger Status		and, if it accepts the request, creates a new Trigger Status
	Resource.		Resource.
	3. The dCDN responds to the uCDN with an HTTP 201 response status,		3. The dCDN responds to the uCDN with an HTTP 201 response status
	and the location of the Trigger Status Resource.		and the location of the Trigger Status Resource.
	4. The uCDN can poll, possibly repeatedly, the Trigger Status		4. The uCDN can poll, possibly repeatedly, the Trigger Status
	Resource in the dCDN.		Resource in the dCDN.
	5. The dCDN responds with the Trigger Status Resource, describing		5. The dCDN responds with the Trigger Status Resource, describing
	progress or results of the CI/T Trigger Command.		the progress or results of the CI/T Trigger Command.
	The remainder of this document describes the messages, Trigger Status		The remainder of this document describes the messages, Trigger Status
	Resources, and collections of Trigger Status Resources in more		Resources, and collections of Trigger Status Resources in more
	detail.		detail.
	2.1. Timing of Triggered Activity		2.1. Timing of Triggered Activity
	Timing of the execution of CI/T Commands is under the dCDN's control,		Timing of the execution of CI/T Commands is under the dCDN's control,
	including its start-time and pacing of the activity in the network.		including its start time and pacing of the activity in the network.
	CI/T invalidate and purge commands MUST be applied to all data		CI/T "invalidate" and "purge" commands MUST be applied to all data
	acquired before the command was accepted by the dCDN. The dCDN		acquired before the command was accepted by the dCDN. The dCDN
	SHOULD NOT apply CI/T invalidate and purge commands to data acquired		SHOULD NOT apply CI/T "invalidate" and "purge" commands to data
	after the CI/T Command was accepted, but this may not always be		acquired after the CI/T Command was accepted, but this may not always
	achievable so the uCDN cannot count on that.		be achievable, so the uCDN cannot count on that.
	If the uCDN wishes to invalidate or purge content then immediately		If the uCDN wishes to invalidate or purge content and then
	pre-position replacement content at the same URLs, it SHOULD ensure		immediately pre-position replacement content at the same URLs, it
	the dCDN has completed the invalidate/purge before initiating the		SHOULD ensure that the dCDN has completed the invalidate/purge before
	prepositioning. Otherwise, there is a risk that the dCDN pre-		initiating the pre-positioning. Otherwise, there is a risk that the
	positions the new content, then immediately invalidates or purges it		dCDN pre-positions the new content, then immediately invalidates or
	(as a result of the two uCDN requests running in parallel).		purges it (as a result of the two uCDN requests running in parallel).
	Because the CI/T Command timing is under the dCDN's control, the dCDN		Because the CI/T Command timing is under the dCDN's control, the dCDN
	implementation can choose whether to apply CI/T invalidate and purge		implementation can choose whether to apply CI/T "invalidate" and
	commands to content acquisition that has already started when the		"purge" commands to content acquisition that has already started when
	command is received.		the command is received.
	2.2. Scope of Triggered Activity		2.2. Scope of Triggered Activity
	Each CI/T Command can operate on multiple metadata and content URLs.		Each CI/T Command can operate on multiple metadata and content URLs.
	Multiple representations of an HTTP resource may share the same URL.		Multiple representations of an HTTP resource may share the same URL.
	CI/T Trigger Commands that invalidate or purge metadata or content		CI/T Trigger Commands that invalidate or purge metadata or content
	apply to all resource representations with matching URLs.		apply to all resource representations with matching URLs.
	2.2.1. Multiple Interconnected CDNs		2.2.1. Multiple Interconnected CDNs
	In a network of interconnected CDNs a single uCDN will originate a		In a network of interconnected CDNs, a single uCDN will originate a
	given item of metadata and associated content, it may distribute that		given item of metadata and associated content. It may distribute
	metadata and content to more than one dCDN, which may in-turn		that metadata and content to more than one dCDN, which may in turn
	distribute that metadata and content to further-downstream CDNs.		distribute that metadata and content to CDNs located further
			downstream.
	An intermediate CDN is a dCDN that passes on CDNI metadata and		An intermediate CDN is a dCDN that passes on CDNI Metadata and
	content to further-downstream dCDNs.		content to dCDNs located further downstream.
	A diamond configuration is one where a dCDN can acquire metadata and		A "diamond" configuration is one where a dCDN can acquire metadata
	content originated in one uCDN from that uCDN itself and an		and content originated in one uCDN from that uCDN itself and an
	intermediate CDN, or via more than one intermediate CDN.		intermediate CDN, or via more than one intermediate CDN.
	CI/T commands originating in the single source uCDN affect metadata		CI/T Commands originating in the single source uCDN affect metadata
	and content in all dCDNs but, in a diamond configuration, it may not		and content in all dCDNs; however, in a diamond configuration, it may
	be possible for the dCDN to determine which uCDN it acquired content		not be possible for the dCDN to determine which uCDN it acquired
	from. In this case a dCDN MUST allow each uCDN from which it may		content from. In this case, a dCDN MUST allow each uCDN from which
	have acquired the content to act upon that content using CI/T		it may have acquired the content to act upon that content using CI/T
	Commands.		Commands.
	In all other cases, a dCDN MUST reject CI/T Commands from a uCDN that		In all other cases, a dCDN MUST reject CI/T Commands from a uCDN that
	act on another uCDN's data using, for example, HTTP "403 Forbidden".		attempts to act on another uCDN's content by using, for example,
			HTTP 403 ("Forbidden").
	Security considerations are discussed further in Section 8.		Security considerations are discussed further in Section 8.
	The diamond configuration may lead to inefficient interactions, but		The diamond configuration may lead to inefficient interactions, but
	the interactions are otherwise harmless. For example:		the interactions are otherwise harmless. For example:
	o When the uCDN issues an invalidate CI/T command, a dCDN will		o When the uCDN issues an "invalidate" CI/T Command, a dCDN will
	receive that command from multiple directly connected uCDNs. The		receive that command from multiple directly connected uCDNs. The
	dCDN may schedule multiple those commands separately, and the last		dCDN may schedule multiple such commands separately, and the last
	may affect content already revalidated following execution of the		scheduled command may affect content already revalidated following
	invalidate command scheduled first.		execution of the "invalidate" command that was scheduled first.
	o If one of a dCDN's directly-connected uCDNs loses its rights to		o If one of a dCDN's directly connected uCDNs loses its rights to
	distribute content, it may issue a CI/T purge command. That purge		distribute content, it may issue a CI/T "purge" command. That
	may affect content the dCDN could retain because it's distributed		purge may affect content the dCDN could retain because it's
	by another directly-connected uCDN. But, that content can be re-		distributed by another directly connected uCDN. But, that content
	acquired by the dCDN from the remaining uCDN.		can be reacquired by the dCDN from the remaining uCDN.
	o When the uCDN originating an item of content issues a CI/T purge		o When the uCDN originating an item of content issues a CI/T purge
	followed by a preposition - two directly connected uCDNs will pass		followed by a pre-position, two directly connected uCDNs will pass
	those commands to a dCDN. That dCDN implementation need not merge		those commands to a dCDN. That dCDN implementation need not merge
	those operations, or notice the repetition. In which case the		those operations or notice the repetition, in which case the purge
	purge issued by one uCDN will complete before the other. The		issued by one uCDN will complete before the other. The first uCDN
	first uCDN to finish its purge may then forward the preposition		to finish its purge may then forward the "preposition" trigger,
	trigger, and content pre-positioned as a result might be affected		and content pre-positioned as a result might be affected by the
	by the still-running purge issued by the other uCDN. However, the		still-running purge issued by the other uCDN. However, the dCDN
	dCDN will re-acquire that content as needed, or when it's asked to		will reacquire that content as needed, or when it's asked to
	pre-position the content by the second uCDN. A dCDN		pre-position the content by the second uCDN. A dCDN
	implementation could avoid this interaction by knowing which uCDN		implementation could avoid this interaction by knowing which uCDN
	it acquired the content from, or it could minimize the		it acquired the content from, or it could minimize the
	consequences by recording the time at which the invalidate/purge		consequences by recording the time at which the
	command was received and not applying it to content acquired after		"invalidate"/"purge" command was received and not applying it to
	that time.		content acquired after that time.
	2.3. Trigger Results		2.3. Trigger Results
	Possible states for a Trigger Status Resource are defined in section		Possible states for a Trigger Status Resource are defined in
	Section 5.2.3.		Section 5.2.3.
	The CI/T Trigger Command MUST NOT be reported as 'complete' until all		The CI/T Trigger Command MUST NOT be reported as "complete" until all
	actions have been completed successfully. The reasons for failure,		actions have been completed successfully. The reasons for failure,
	and URLs or Patterns affected, SHOULD be enumerated in the Trigger		and URLs or patterns affected, SHOULD be enumerated in the Trigger
	Status Resource. For more detail, see section Section 4.7.		Status Resource. For more details, see Section 4.7.
	If a dCDN is also acting as a uCDN in a cascade, it MUST forward CI/T		If a dCDN is also acting as a uCDN in a cascade, it MUST forward CI/T
	Commands to any downstream CDNs that may be affected. The CI/T		Commands to any dCDNs that may be affected. The CI/T Trigger Command
	Trigger Command MUST NOT be reported as 'complete' in a CDN until it		MUST NOT be reported as "complete" in a CDN until it is "complete" in
	is 'complete' in all of its downstream CDNs. If a CI/T Trigger		all of its dCDNs. If a CI/T Trigger Command is reported as
	Command is reported as 'processed' in any dCDN, intermediate CDNs		"processed" in any dCDN, intermediate CDNs MUST NOT report
	MUST NOT report 'complete', instead they MUST also report		"complete"; instead, they MUST also report "processed". A CI/T
	'processed'. A CI/T Command MAY be reported as 'failed' as soon as		Command MAY be reported as "failed" as soon as it fails in a CDN or
	it fails in a CDN or in any of its downstream CDNs. A cancelled CI/T		in any of its dCDNs. A canceled CI/T Trigger Command MUST be
	Trigger Command MUST be reported as 'cancelling' until it has been		reported as "cancelling" until it has been reported as "cancelled",
	reported as 'cancelled', 'complete', or 'failed' by all dCDNs in a		"complete", or "failed" by all dCDNs in a cascade.
	cascade.
	3. Collections of Trigger Status Resources		3. Collections of Trigger Status Resources
	As described in Section 2, Trigger Status Resources exist in the dCDN		As described in Section 2, Trigger Status Resources exist in the dCDN
	to report the status of activity triggered by each uCDN.		to report the status of activity triggered by each uCDN.
	A collection of Trigger Status Resources is a resource that contains		A collection of Trigger Status Resources is a resource that contains
	a reference to each Trigger Status Resource in that collection.		a reference to each Trigger Status Resource in that collection.
	The dCDN MUST make a collection of a uCDN's Trigger Status Resources		The dCDN MUST make a collection of a uCDN's Trigger Status Resources
	available to that uCDN. This collection includes all of the Trigger		available to that uCDN. This collection includes all of the Trigger
	Status Resources created for CI/T Commands from the uCDN that have		Status Resources created for CI/T Commands from the uCDN that have
	been accepted by the dCDN, and have not yet been deleted by the uCDN,		been accepted by the dCDN, and have not yet been deleted by the uCDN,
	or expired and removed by the dCDN (as described in section		or expired and removed by the dCDN (as described in Section 4.4).
	Section 4.4). Trigger Status Resources belonging to a uCDN MUST NOT		Trigger Status Resources belonging to a uCDN MUST NOT be visible to
	be visible to any other CDN. The dCDN could, for example, achieve		any other CDN. The dCDN could, for example, achieve this by offering
	this by offering different collection URLs to each uCDN, and by		different collection URLs to each uCDN and by filtering the response
	filtering the response based on the uCDN with which the HTTP client		based on the uCDN with which the HTTP client is associated.
	is associated.
	To trigger activity in a dCDN, or to cancel triggered activity, the		To trigger activity in a dCDN or to cancel triggered activity, the
	uCDN POSTs a CI/T Command to the dCDN's collection of the uCDN's		uCDN POSTs a CI/T Command to the dCDN's collection of the uCDN's
	Trigger Status Resources.		Trigger Status Resources.
	In order to allow the uCDN to check the status of multiple jobs in a		In order to allow the uCDN to check the status of multiple jobs in a
	single request, the dCDN MAY also maintain collections representing		single request, the dCDN MAY also maintain collections representing
	filtered views of the collection of all Trigger Status Resources.		filtered views of the collection of all Trigger Status Resources.
	These filtered collections are optional-to-implement but, if		These filtered collections are "optional-to-implement", but if they
	implemented, the dCDN MUST include links to them in the collection of		are implemented, the dCDN MUST include links to them in the
	all Trigger Status Resources. The filtered collections are:		collection of all Trigger Status Resources. The filtered
			collections are:
	o Pending - Trigger Status Resources for CI/T Trigger Commands that		o Pending - Trigger Status Resources for CI/T Trigger Commands that
	have been accepted, but not yet acted upon.		have been accepted but not yet acted upon.
	o Active - Trigger Status Resources for CI/T Trigger Commands that		o Active - Trigger Status Resources for CI/T Trigger Commands that
	are currently being processed in the dCDN.		are currently being processed in the dCDN.
	o Complete - Trigger Status Resources representing activity that		o Complete - Trigger Status Resources representing activity that
	completed successfully, and 'processed' CI/T Trigger Commands for		completed successfully, and "processed" CI/T Trigger Commands for
	which no further status updates will be made by the dCDN.		which no further status updates will be made by the dCDN.
	o Failed - Trigger Status Resources representing CI/T Commands that		o Failed - Trigger Status Resources representing CI/T Commands that
	failed or were cancelled by the uCDN.		failed or were canceled by the uCDN.
	4. CDNI Trigger Interface		4. CDNI Trigger Interface
	This section describes an interface to enable an upstream CDN to		This section describes an interface to enable a uCDN to trigger
	trigger activity in a downstream CDN.		activity in a dCDN.
	The CI/T interface builds on top of HTTP, so dCDNs may make use of		The CI/T interface builds on top of HTTP, so dCDNs may make use of
	any HTTP feature when implementing the CI/T interface. For example,		any HTTP feature when implementing the CI/T interface. For example,
	a dCDN SHOULD make use of HTTP's caching mechanisms to indicate that		a dCDN SHOULD make use of HTTP's caching mechanisms to indicate that
	a requested response/representation has not been modified, reducing		a requested response/representation has not been modified, reducing
	the uCDN's processing needed to determine whether the status of		the uCDN's processing needed to determine whether the status of
	triggered activity has changed.		triggered activity has changed.
	All dCDNs implementing CI/T MUST support the HTTP GET, HEAD, POST and		All dCDNs implementing CI/T MUST support the HTTP GET, HEAD, POST,
	DELETE methods as defined in [RFC7231].		and DELETE methods as defined in [RFC7231].
	The only representation specified in this document is JSON,		The only representation specified in this document is JSON [RFC7159].
	[RFC7159]. It MUST be supported by the uCDN and by the dCDN.		It MUST be supported by the uCDN and by the dCDN.
	The URL of the dCDN's collection of all Trigger Status Resources		The URL of the dCDN's collection of all Trigger Status Resources
	needs to be either discovered by, or configured in, the uCDN. The		needs to be either discovered by or configured in the uCDN. The
	mechanism for discovery of that URL is outside the scope of this		mechanism for discovery of that URL is outside the scope of this
	document.		document.
	CI/T Commands are POSTed to the dCDN's collection of all Trigger		CI/T Commands are POSTed to the dCDN's collection of all Trigger
	Status Resources. If a CI/T Trigger Command is accepted by the dCDN,		Status Resources. If a CI/T Trigger Command is accepted by the dCDN,
	the dCDN creates a new Trigger Status Resource and returns its URI to		the dCDN creates a new Trigger Status Resource and returns its URI to
	the uCDN in an HTTP 201 response. The triggered activity can then be		the uCDN in an HTTP 201 response. The triggered activity can then be
	monitored by the uCDN using that resource and the collections		monitored by the uCDN using that resource and the collections
	described in Section 3.		described in Section 3.
	The URI of each Trigger Status Resource is returned to the uCDN when		The URI of each Trigger Status Resource is returned to the uCDN when
	it is created, and URIs of all Trigger Status Resources are listed in		it is created, and URIs of all Trigger Status Resources are listed in
	the dCDN's collection of all Trigger Status Resources. This means		the dCDN's collection of all Trigger Status Resources. This means
	all Trigger Status Resources can be discovered by the uCDN, so dCDNs		all Trigger Status Resources can be discovered by the uCDN, so dCDNs
	are free to assign whatever structure they desire to the URIs for CI/		are free to assign whatever structure they desire to the URIs for
	T resources. Therefore uCDNs MUST NOT make any assumptions regarding		CI/T resources. Therefore, uCDNs MUST NOT make any assumptions
	the structure of CI/T URIs or the mapping between CI/T objects and		regarding the structure of CI/T URIs or the mapping between CI/T
	their associated URIs. URIs present in the examples in this document		objects and their associated URIs. URIs present in the examples in
	are purely illustrative and are not intended to impose a definitive		this document are purely illustrative and are not intended to impose
	structure on CI/T interface implementations.		a definitive structure on CI/T interface implementations.
	4.1. Creating Triggers		4.1. Creating Triggers
	To issue a CI/T Command, the uCDN makes an HTTP POST to the dCDN's		To issue a CI/T Command, the uCDN makes an HTTP POST to the dCDN's
	collection of all of the uCDN's Trigger Status Resources. The		collection of all of the uCDN's Trigger Status Resources. The
	request body of that POST is a CI/T Command, as described in		request body of that POST is a CI/T Command, as described in
	Section 5.1.1.		Section 5.1.1.
	The dCDN validates the CI/T Command. If the command is malformed or		The dCDN validates the CI/T Command. If the command is malformed or
	the uCDN does not have sufficient access rights, the dCDN MUST either		the uCDN does not have sufficient access rights, the dCDN MUST either
	respond with an appropriate 4xx HTTP error code and not create a		respond with an appropriate 4xx HTTP error code and not create a
	Trigger Status Resource, or create a 'failed' Trigger Status Resource		Trigger Status Resource or create a "failed" Trigger Status Resource
	containing an appropriate error description.		containing an appropriate Error Description.
	When a CI/T Trigger Command is accepted, the uCDN MUST create a new		When a CI/T Trigger Command is accepted, the uCDN MUST create a new
	Trigger Status Resource which will convey a specification of the CI/T		Trigger Status Resource that will convey a specification of the CI/T
	Command and its current status. The HTTP response to the dCDN MUST		Command and its current status. The HTTP response to the dCDN MUST
	have status code 201 and MUST convey the URI of the Trigger Status		have status code 201 and MUST convey the URI of the Trigger Status
	Resource in the Location header field. The HTTP response SHOULD		Resource in the Location header field [RFC7231]. The HTTP response
	include the content of the newly created Trigger Status Resource.		SHOULD include the content of the newly created Trigger Status
	This is particularly important in cases where the CI/T Trigger		Resource. This is particularly important in cases where the CI/T
	Command has completed immediately.		Trigger Command has completed immediately.
	Once a Trigger Status Resource has been created the dCDN MUST NOT re-		Once a Trigger Status Resource has been created, the dCDN MUST NOT
	use its URI, even after that Trigger Status Resource has been		reuse its URI, even after that Trigger Status Resource has been
	removed.		removed.
	The dCDN SHOULD track and report on progress of CI/T Trigger Commands		The dCDN SHOULD track and report on the progress of CI/T Trigger
	using a Trigger Status Resource, Section 5.1.2. If the dCDN is not		Commands using a Trigger Status Resource (Section 5.1.2). If the
	able to do that, it MUST indicate that it has accepted the request		dCDN is not able to do that, it MUST indicate that it has accepted
	but will not be providing further status updates. To do this, it		the request but will not be providing further status updates. To do
	sets the status of the Trigger Status Resource to "processed". In		this, it sets the status of the Trigger Status Resource to
	this case, CI/T processing should continue as for a "complete"		"processed". In this case, CI/T processing should continue as for a
	request, so the Trigger Status Resource MUST be added to the dCDN's		"complete" request, so the Trigger Status Resource MUST be added to
	collection of Complete Trigger Status Resources. The dCDN SHOULD		the dCDN's collection of complete Trigger Status Resources. The dCDN
	also provide an estimated completion time for the request, by using		SHOULD also provide an estimated completion time for the request by
	the "etime" property of the Trigger Status Resource. This will allow		using the "etime" property of the Trigger Status Resource. This will
	the uCDN to schedule prepositioning after an earlier delete of the		allow the uCDN to schedule pre-positioning after an earlier delete of
	same URLs is expected to have finished.		the same URLs is expected to have finished.
	If the dCDN is able to track the execution of CI/T Commands and a CI/		If the dCDN is able to track the execution of CI/T Commands and a
	T Command is queued by the dCDN for later action, the status property		CI/T Command is queued by the dCDN for later action, the "status"
	of the Trigger Status Resource MUST be "pending". Once processing		property of the Trigger Status Resource MUST be "pending". Once
	has started the "status" MUST be "active". Finally, once the CI/T		processing has started, the status MUST be "active". Finally, once
	Command is complete, the status MUST be set to "complete" or		the CI/T Command is complete, the status MUST be set to "complete" or
	"failed".		"failed".
	A CI/T Trigger Command may result in no activity in the dCDN if, for		A CI/T Trigger Command may result in no activity in the dCDN if, for
	example, it is an invalidate or purge request for data the dCDN has		example, it is an "invalidate" or "purge" request for data the dCDN
	not yet acquired, or a pre-position request for data it has already		has not yet acquired, or a "preposition" request for data that it has
	acquired and which is still valid. In this case, the "status" of the		already acquired and that is still valid. In this case, the status
	Trigger Status Resource MUST be "processed" or "complete", and the		of the Trigger Status Resource MUST be "processed" or "complete", and
	Trigger Status Resource MUST be added to the dCDN's collection of		the Trigger Status Resource MUST be added to the dCDN's collection of
	Complete Trigger Status Resources.		complete Trigger Status Resources.
	Once created, Trigger Status Resources can be cancelled or deleted by		Once created, Trigger Status Resources can be canceled or deleted by
	the uCDN, but not modified. The dCDN MUST reject PUT and POST		the uCDN, but not modified. The dCDN MUST reject PUT and POST
	requests from the uCDN to Trigger Status Resources by responding with		requests from the uCDN to Trigger Status Resources by responding with
	an appropriate HTTP status code, for example 405 "Method Not		an appropriate HTTP status code -- for example, 405 ("Method Not
	Allowed".		Allowed").
	4.2. Checking Status		4.2. Checking Status
	The uCDN has two ways to check progress of CI/T Commands it has		The uCDN has two ways to check the progress of CI/T Commands it has
	issued to the dCDN, described in sections Section 4.2.1 and		issued to the dCDN, as described in Sections 4.2.1 and 4.2.2.
	Section 4.2.2.
	To allow the uCDN to check for change in status of a Trigger Status		To allow the uCDN to check for changes in the status of a Trigger
	Resource or collection of Trigger Status Resources without re-		Status Resource or collection of Trigger Status Resources without
	fetching the whole Resource or Collection, the dCDN SHOULD include		refetching the whole resource or collection, the dCDN SHOULD include
	Entity Tags for the uCDN to use as cache validators, as defined in		entity-tags (ETags) for the uCDN to use as cache validators, as
	[RFC7232].		defined in [RFC7232].
	The dCDN SHOULD use the cache control headers for responses to GETs		The dCDN SHOULD use the cache control headers for responses to GETs
	for Trigger Status Resources and Collections to indicate the		for Trigger Status Resources and Collections to indicate the
	frequency at which it recommends the uCDN should poll for change.		frequency at which it recommends that the uCDN should poll for
			change.
	4.2.1. Polling Trigger Status Resource collections		4.2.1. Polling Trigger Status Resource Collections
	The uCDN can fetch the collection of its Trigger Status Resources, or		The uCDN can fetch the collection of its Trigger Status Resources or
	filtered views of that collection.		filtered views of that collection.
	This makes it possible to poll status of all CI/T Trigger Commands in		This makes it possible to poll the status of all CI/T Trigger
	a single request. If the dCDN moves a Trigger Status Resource from		Commands in a single request. If the dCDN moves a Trigger Status
	the Active to the Completed collection, the uCDN can fetch the result		Resource from the active to the completed collection, the uCDN can
	of that activity.		fetch the result of that activity.
	When polling in this way, the uCDN SHOULD use HTTP Entity Tags to		When polling in this way, the uCDN SHOULD use HTTP ETags to monitor
	monitor for change, rather than repeatedly fetching the whole		for change, rather than repeatedly fetching the whole collection. An
	collection. An example of this is given in section Section 6.2.4.		example of this is given in Section 6.2.4.
	4.2.2. Polling Trigger Status Resources		4.2.2. Polling Trigger Status Resources
	The uCDN has a URI provided by the dCDN for each Trigger Status		The uCDN has a URI provided by the dCDN for each Trigger Status
	Resource it has created, it may fetch that Trigger Status Resource at		Resource it has created. It may fetch that Trigger Status Resource
	any time.		at any time.
	This can be used to retrieve progress information, and to fetch the		This can be used to retrieve progress information and to fetch the
	result of the CI/T Command.		result of the CI/T Command.
	When polling in this way, the uCDN SHOULD use HTTP Entity Tags to		When polling in this way, the uCDN SHOULD use HTTP ETags to monitor
	monitor for change, rather than repeatedly fetching the Trigger		for change, rather than repeatedly fetching the Trigger Status
	Status Resource.		Resource.
	4.3. Cancelling Triggers		4.3. Canceling Triggers
	The uCDN can request cancellation of a CI/T Trigger Command by		The uCDN can request cancellation of a CI/T Trigger Command by
	POSTing a CI/T Cancel Command to the collection of all Trigger Status		POSTing a CI/T Cancel Command to the collection of all Trigger Status
	Resources.		Resources.
	The dCDN is required to accept and respond to the CI/T Cancel		The dCDN is required to accept and respond to the CI/T Cancel
	Command, but the actual cancellation of a CI/T Trigger Command is		Command, but the actual cancellation of a CI/T Trigger Command is
	optional-to-implement.		optional-to-implement.
	The dCDN MUST respond to the CI/T Cancel Command appropriately, for		The dCDN MUST respond to the CI/T Cancel Command appropriately -- for
	example with HTTP status code 200 "OK" if the cancellation has been		example, with HTTP status code 200 ("OK") if the cancellation has
	processed and the CI/T Command is inactive, 202 "Accepted" if the		been processed and the CI/T Command is inactive, 202 ("Accepted") if
	command has been accepted but the CI/T Command remains active, or 501		the command has been accepted but the CI/T Command remains active, or
	"Not Implemented" if cancellation is not supported by the dCDN.		501 ("Not Implemented") if cancellation is not supported by the dCDN.
	If cancellation of a "pending" Trigger Status Resource is accepted by		If cancellation of a "pending" Trigger Status Resource is accepted by
	the dCDN, the dCDN SHOULD NOT start processing of that activity.		the dCDN, the dCDN SHOULD NOT start the processing of that activity.
	Issuing a CT/T Cancel Command for a "pending" Trigger Status Resource		Issuing a CI/T Cancel Command for a "pending" Trigger Status Resource
	does not however guarantee that the corresponding activity will not		does not, however, guarantee that the corresponding activity will not
	be started, because the uCDN cannot control the timing of that		be started, because the uCDN cannot control the timing of that
	activity. Processing could, for example, start after the POST is		activity. Processing could, for example, start after the POST is
	sent by the uCDN but before that request is processed by the dCDN.		sent by the uCDN but before that request is processed by the dCDN.
	If cancellation of an "active" or "processed" Trigger Status Resource		If cancellation of an "active" or "processed" Trigger Status Resource
	is accepted by the dCDN, the dCDN SHOULD stop processing the CI/T		is accepted by the dCDN, the dCDN SHOULD stop processing the CI/T
	Command. However, as with cancellation of a "pending" CI/T Command,		Command. However, as with cancellation of a "pending" CI/T Command,
	the dCDN does not guarantee this.		the dCDN does not guarantee this.
	If the CI/T Command cannot be stopped immediately, the status in the		If the CI/T Command cannot be stopped immediately, the status in the
	corresponding Trigger Status Resource MUST be set to "cancelling",		corresponding Trigger Status Resource MUST be set to "cancelling",
	and the Trigger Status Resource MUST remain in the collection of		and the Trigger Status Resource MUST remain in the collection of
	Trigger Status Resources for active CI/T Commands. If processing is		Trigger Status Resources for active CI/T Commands. If processing is
	stopped before normal completion, the status value in the Trigger		stopped before normal completion, the status value in the Trigger
	Status Resource MUST be set to "cancelled", and the Trigger Status		Status Resource MUST be set to "cancelled", and the Trigger Status
	Resource MUST be included in the collection of failed CT/T Trigger		Resource MUST be included in the collection of failed CI/T Trigger
	Commands.		Commands.
	Cancellation of a "complete" or "failed" Trigger Status Resource		Cancellation of a "complete" or "failed" Trigger Status Resource
	requires no processing in the dCDN. Its status MUST NOT be changed		requires no processing in the dCDN. Its status MUST NOT be changed
	to "cancelled".		to "cancelled".
	4.4. Deleting Triggers		4.4. Deleting Triggers
	The uCDN can delete Trigger Status Resources at any time, using the		The uCDN can delete Trigger Status Resources at any time, using the
	HTTP DELETE method. The effect is similar to cancellation, but no		HTTP DELETE method. The effect is similar to cancellation, but no
	Trigger Status Resource remains afterwards.		Trigger Status Resource remains afterwards.
	Once deleted, the references to a Trigger Status Resource MUST be		Once deleted, the references to a Trigger Status Resource MUST be
	removed from all Trigger Status Resource collections. Subsequent		removed from all Trigger Status Resource collections. Subsequent
	requests to GET the deleted Trigger Status Resource SHOULD be		requests to GET the deleted Trigger Status Resource SHOULD be
	rejected by the dCDN with an HTTP error.		rejected by the dCDN with an HTTP error.
	If a "pending" Trigger Status Resource is deleted, the dCDN SHOULD		If a "pending" Trigger Status Resource is deleted, the dCDN
	NOT start processing of that activity. Deleting a "pending" Trigger		SHOULD NOT start the processing of that activity. Deleting a
	Status Resource does not however guarantee that it has not started		"pending" Trigger Status Resource does not, however, guarantee that
	because the uCDN cannot control the timing of that activity.		it has not started, because the uCDN cannot control the timing of
	Processing may, for example, start after the DELETE is sent by the		that activity. Processing may, for example, start after the DELETE
	uCDN but before that request is processed by the dCDN.		is sent by the uCDN but before that request is processed by the dCDN.
	If an "active" or "processed" Trigger Status Resource is deleted, the		If an "active" or "processed" Trigger Status Resource is deleted, the
	dCDN SHOULD stop processing the CI/T Command. However, as with		dCDN SHOULD stop processing the CI/T Command. However, as with
	deletion of a "pending" Trigger Status Resource, the dCDN does not		deletion of a "pending" Trigger Status Resource, the dCDN does not
	guarantee this.		guarantee this.
	Deletion of a "complete" or "failed" Trigger Status Resource requires		Deletion of a "complete" or "failed" Trigger Status Resource requires
	no processing in the dCDN other than deletion of the Trigger Status		no processing in the dCDN other than deletion of the Trigger Status
	Resource.		Resource.
	4.5. Expiry of Trigger Status Resources		4.5. Expiry of Trigger Status Resources
	The dCDN can choose to automatically delete Trigger Status Resources		The dCDN can choose to automatically delete Trigger Status Resources
	some time after they become "complete", "processed", "failed" or		some time after they become "complete", "processed", "failed", or
	"cancelled". In this case, the dCDN will remove the Trigger Status		"cancelled". In this case, the dCDN will remove the Trigger Status
	Resource and respond to subsequent requests for it with an HTTP		Resource and respond to subsequent requests for it with an HTTP
	error.		error.
	If the dCDN does remove Trigger Status Resources automatically, it		If the dCDN does remove Trigger Status Resources automatically, it
	MUST report the length of time after which it will do so, using a		MUST report the length of time after which it will do so, using a
	property of the collection of all Trigger Status Resources. It is		property of the collection of all Trigger Status Resources. It is
	RECOMMENDED that Trigger Status Resources are not automatically		RECOMMENDED that Trigger Status Resources are not automatically
	deleted by the dCDN for at least 24 hours after they become		deleted by the dCDN for at least 24 hours after they become
	"complete", "processed", "failed" or "cancelled".		"complete", "processed", "failed", or "cancelled".
	To ensure it is able to get the status of its Trigger Status		To ensure that it is able to get the status of its Trigger Status
	Resources for completed and failed CI/T Commands, it is RECOMMENDED		Resources for completed and failed CI/T Commands, it is RECOMMENDED
	that the uCDN polling interval is less than the time after which		that the uCDN polling interval is less than the time after which
	records for completed activity will be deleted.		records for completed activity will be deleted.
	4.6. Loop Detection and Prevention		4.6. Loop Detection and Prevention
	Given three CDNs, A, B and C, if CDNs B and C delegate delivery of		Given three CDNs, A, B, and C, if CDNs B and C delegate delivery of
	CDN A's content to each other, CDN A's CI/T Commands could be passed		CDN A's content to each other, CDN A's CI/T Commands could be passed
	between CDNs B and C in a loop. More complex networks of CDNs could		between CDNs B and C in a loop. More complex networks of CDNs could
	contain similar loops involving more hops.		contain similar loops involving more hops.
	In order to prevent and detect such CI/T loops, each CDN uses a CDN		In order to prevent and detect such CI/T loops, each CDN uses a CDN
	Provider ID to uniquely identify itself. In every CI/T Command it		Provider ID (PID) to uniquely identify itself. In every CI/T Command
	originates or cascades, each CDN MUST append an array element		it originates or cascades, each CDN MUST append an array element
	containing its CDN Provider ID to a JSON array under an entry named		containing its CDN PID to a JSON array under an entry named
	"cdn-path". When receiving CI/T Commands a dCDN MUST check the cdn-		"cdn-path". When receiving CI/T Commands, a dCDN MUST check the
	path and reject any CI/T Command which already contains its own CDN		cdn-path and reject any CI/T Command that already contains its own
	Provider ID in the cdn-path. Transit CDNs MUST check the cdn-path		CDN PID in the cdn-path. Transit CDNs MUST check the cdn-path and
	and not cascade the CI/T Command to dCDNs that are already listed in		not cascade the CI/T Command to dCDNs that are already listed in the
	cdn-path.		cdn-path.
	The CDN Provider Id consists of the two characters "AS" followed by		The CDN PID consists of the two characters "AS" followed by the CDN
	the CDN Provider's Autonomous System number [RFC1930], then a colon		provider's Autonomous System number [RFC1930], then a colon (":") and
	(':') and an additional qualifier that is used to guarantee		an additional qualifier that is used to guarantee uniqueness in case
	uniqueness in case a particular AS has multiple independent CDNs		a particular AS has multiple independent CDNs deployed -- for
	deployed. For example "AS64496:0".		example, "AS64496:0".
	If the CDN provider has multiple Autonomous Systems, the same AS		If the CDN provider has multiple ASes, the same AS number SHOULD be
	number SHOULD be used in all messages from that CDN provider, unless		used in all messages from that CDN provider, unless there are
	there are multiple distinct CDNs.		multiple distinct CDNs.
	If the RI interface described in [I-D.ietf-cdni-redirection] is		If the CDNI Request Routing Redirection interface (RI) described in
	implemented by the dCDN, the CI/T and RI interfaces SHOULD use the		[RFC7975] is implemented by the dCDN, the CI/T interface and the RI
	same CDN Provider Id.		SHOULD use the same CDN PID.
	4.7. Error Handling		4.7. Error Handling
	A dCDN can signal rejection of a CI/T Command using HTTP status		A dCDN can signal rejection of a CI/T Command using HTTP status codes
	codes. For example, 400 if the request is malformed, or 403 or 404		-- for example, 400 ("Bad Request") if the request is malformed, or
	if the uCDN does not have permission to issue CI/T Commands or it is		403 ("Forbidden") or 404 ("Not Found") if the uCDN does not have
	trying to act on another CDN's data.		permission to issue CI/T Commands or it is trying to act on another
			CDN's data.
	If any part of the CI/T Trigger Command fails, the trigger SHOULD be		If any part of the CI/T Trigger Command fails, the trigger SHOULD be
	reported as "failed" once its activity is complete or if no further		reported as "failed" once its activity is complete or if no further
	errors will be reported. The "errors" property in the Trigger Status		errors will be reported. The "errors" property in the Trigger Status
	Resource will be used to enumerate which actions failed and the		Resource will be used to enumerate which actions failed and the
	reasons for failure, and can be present while the Trigger Status		reasons for failure, and can be present while the Trigger Status
	Resource is still "pending" or "active", if the CI/T Trigger Command		Resource is still "pending" or "active", if the CI/T Trigger Command
	is still running for some URLs or Patterns in the Trigger		is still running for some URLs or patterns in the Trigger
	Specification.		Specification.
	Once a request has been accepted, processing errors are reported in		Once a request has been accepted, processing errors are reported in
	the Trigger Status Resource using a list of Error Descriptions. Each		the Trigger Status Resource using a list of Error Descriptions. Each
	Error Description is used to report errors against one or more of the		Error Description is used to report errors against one or more of the
	URLs or Patterns in the Trigger Specification.		URLs or patterns in the Trigger Specification.
	If a surrogate affected by a CI/T Trigger Command is offline in the		If a Surrogate affected by a CI/T Trigger Command is offline in the
	dCDN, or the dCDN is unable to pass a CI/T Command on to any of its		dCDN or the dCDN is unable to pass a CI/T Command on to any of its
	cascaded dCDNs:		cascaded dCDNs:
	o If the CI/T Command is abandoned by the dCDN, the dCDN SHOULD		o If the CI/T Command is abandoned by the dCDN, the dCDN SHOULD
	report an error.		report an error.
	o A CI/T "invalidate" command may be reported as "complete" when		o A CI/T "invalidate" command may be reported as "complete" when
	surrogates that may have the data are offline. In this case,		Surrogates that may have the data are offline. In this case,
	surrogates MUST NOT use the affected data without first		Surrogates MUST NOT use the affected data without first
	revalidating it when they are back online.		revalidating it when they are back online.
	o CI/T "preposition" and "purge" commands can be reported as		o CI/T "preposition" and "purge" commands can be reported as
	"processed" if affected caches are offline and the activity will		"processed" if affected caches are offline and the activity will
	complete when they return to service.		complete when they return to service.
	o Otherwise, the dCDN SHOULD keep the Trigger Status Resource in		o Otherwise, the dCDN SHOULD keep the Trigger Status Resource in
	state "pending" or "active" until the CI/T Command is acted upon,		state "pending" or "active" until either the CI/T Command is acted
	or the uCDN chooses to cancel it.		upon or the uCDN chooses to cancel it.
	4.8. Content URLs		4.8. Content URLs
	If content URLs are transformed by an intermediate CDN in a cascade,		If content URLs are transformed by an intermediate CDN in a cascade,
	that intermediate CDN MUST similarly transform URLs in CI/T Commands		that intermediate CDN MUST similarly transform URLs in CI/T Commands
	it passes to its dCDN.		it passes to its dCDN.
	When processing Trigger Specifications, CDNs MUST ignore the URL		When processing Trigger Specifications, CDNs MUST ignore the URL
	scheme (http or https) in comparing URLs. For example, for a CI/T		scheme (HTTP or HTTPS) in comparing URLs. For example, for a CI/T
	invalidate or purge command, content MUST be invalidated or purged		"invalidate" or "purge" command, content MUST be invalidated or
	regardless of the protocol clients use to request it.		purged regardless of the protocol clients used to request it.
	5. CI/T Object Properties and Encoding		5. CI/T Object Properties and Encoding
	The CI/T Commands, Trigger Status Resources and Trigger Collections		The CI/T Commands, Trigger Status Resources, and Trigger Collections,
	and their properties are encoded using JSON, as defined in sections		as well as their properties, are encoded using JSON, as defined in
	Section 5.1.1, Section 5.2.1, and Section 5.1.2. They MUST use the		Sections 5.1.1, 5.1.2, and 5.1.3. They MUST use the MIME media type
	MIME Media Type 'application/cdni', with parameter 'ptype' values as		"application/cdni", with parameter "ptype" values as defined below
	defined below and in Section 7.1.		and in Section 7.1.
	Names in JSON are case sensitive. The names and literal values		Names in JSON are case sensitive. The names and literal values
	specified in the present document MUST always use lower-case.		specified in the present document MUST always use lowercase.
	JSON types, including 'object', 'array', 'number' and 'string' are		JSON types, including "object", "array", "number", and "string", are
	defined in [RFC7159].		defined in [RFC7159].
	Unrecognised name/value pairs in JSON objects SHOULD NOT be treated		Unrecognized name/value pairs in JSON objects SHOULD NOT be treated
	as an error by either the uCDN or dCDN. They SHOULD be ignored in		as an error by either the uCDN or dCDN. They SHOULD be ignored
	the processing, and passed on by dCDN to any further dCDNs in a		during processing and passed on by the dCDN to any further dCDNs in a
	cascade.		cascade.
	5.1. CI/T Objects		5.1. CI/T Objects
	The top-level objects defined by the CI/T interface are described in		The top-level objects defined by the CI/T interface are described in
	this section.		this section.
	The encoding of values used by these objects is described in		The encoding of values used by these objects is described in
	Section 5.2.		Section 5.2.
	5.1.1. CI/T Commands		5.1.1. CI/T Commands
	CI/T Commands MUST use a MIME Media Type of 'application/cdni;		CI/T Commands MUST use a MIME media type of "application/cdni;
	ptype=ci-trigger-command'.		ptype=ci-trigger-command".
	A CI/T Command is encoded as a JSON object containing the following		A CI/T Command is encoded as a JSON object containing the following
	name/value pairs.		name/value pairs.
	Name: trigger		Name: trigger
	Description: A specification of the trigger type, and a set of
			Description: A specification of the trigger type and a set of
	data to act upon.		data to act upon.
	Value: A Trigger Specification, as defined in Section 5.2.1.		Value: A Trigger Specification, as defined in Section 5.2.1.
	Mandatory: No, but exactly one of "trigger" or "cancel" MUST be		Mandatory: No, but exactly one of "trigger" or "cancel" MUST be
	present in a CI/T Command.		present in a CI/T Command.
	Name: cancel		Name: cancel
	Description: The URLs of Trigger Status Resources for CI/T		Description: The URLs of Trigger Status Resources for CI/T
	Trigger Commands that the uCDN wants to cancel.		Trigger Commands that the uCDN wants to cancel.
	Value: A non-empty JSON array of URLs represented as JSON		Value: A non-empty JSON array of URLs represented as JSON
	strings.		strings.
	Mandatory: No, but exactly one of "trigger" or "cancel" MUST be		Mandatory: No, but exactly one of "trigger" or "cancel" MUST be
	present in a CI/T Command.		present in a CI/T Command.
	Name: cdn-path		Name: cdn-path
	Description: The CDN Provider Identifiers of CDNs that have		Description: The CDN PIDs of CDNs that have already issued the
	already issued the CI/T Command to their dCDNs.		CI/T Command to their dCDNs.
	Value: A non-empty JSON array of JSON strings, where each		Value: A non-empty JSON array of JSON strings, where each
	string is a CDN Provider Identifier as defined in Section 4.6.		string is a CDN PID as defined in Section 4.6.
	Mandatory: Yes.		Mandatory: Yes.
	5.1.2. Trigger Status Resource		5.1.2. Trigger Status Resources
	Trigger Status Resources MUST use a MIME Media Type of 'application/		Trigger Status Resources MUST use a MIME media type of
	cdni; ptype=ci-trigger-status'.		"application/cdni; ptype=ci-trigger-status".
	A Trigger Status Resource is encoded as a JSON object containing the		A Trigger Status Resource is encoded as a JSON object containing the
	following name/value pairs.		following name/value pairs.
	Name: trigger		Name: trigger
	Description: The Trigger Specification posted in the body of		Description: The Trigger Specification POSTed in the body of
	the CI/T Command. Note that this need not be a byte-for-byte		the CI/T Command. Note that this need not be a byte-for-byte
	copy. For example, in the JSON representation the dCDN may re-		copy. For example, in the JSON representation the dCDN may
	serialise the information differently.		re-serialize the information differently.
	Value: A Trigger Specification, as defined in Section 5.2.1.		Value: A Trigger Specification, as defined in Section 5.2.1.
	Mandatory: Yes		Mandatory: Yes.
	Name: ctime		Name: ctime
	Description: Time at which the CI/T Command was received by the		Description: Time at which the CI/T Command was received by the
	dCDN. Time is determined by the dCDN, there is no requirement		dCDN. Time is determined by the dCDN; there is no requirement
	to synchronise clocks between interconnected CDNs.		to synchronize clocks between interconnected CDNs.
	Value: Absolute Time, as defined in Section 5.2.5.		Value: Absolute Time, as defined in Section 5.2.5.
	Mandatory: Yes		Mandatory: Yes.
	Name: mtime		Name: mtime
	Description: Time at which the Trigger Status Resource was last		Description: Time at which the Trigger Status Resource was last
	modified. Time is determined by the dCDN, there is no		modified. Time is determined by the dCDN; there is no
	requirement to synchronise clocks between interconnected CDNs.		requirement to synchronize clocks between interconnected CDNs.
	Value: Absolute Time, as defined in Section 5.2.5.		Value: Absolute Time, as defined in Section 5.2.5.
	Mandatory: Yes		Mandatory: Yes.
	Name: etime		Name: etime
	Description: Estimate of the time at which the dCDN expects to		Description: Estimate of the time at which the dCDN expects to
	complete the activity. Time is determined by the dCDN, there		complete the activity. Time is determined by the dCDN; there
	is no requirement to synchronise clocks between interconnected		is no requirement to synchronize clocks between interconnected
	CDNs.		CDNs.
	Value: Absolute Time, as defined in Section 5.2.5.		Value: Absolute Time, as defined in Section 5.2.5.
	Mandatory: No		Mandatory: No.
	Name: status		Name: status
	Description: Current status of the triggered activity.		Description: Current status of the triggered activity.
	Value: Trigger Status, as defined in Section 5.2.3.		Value: Trigger Status, as defined in Section 5.2.3.
	Mandatory: Yes		Mandatory: Yes.
	Name: errors		Name: errors
	Description: Descriptions of errors that have occurred while		Description: Descriptions of errors that have occurred while
	processing a Trigger Command.		processing a Trigger Command.
	Value: An array of Error Description, as defined in		Value: An array of Error Descriptions, as defined in
	Section 5.2.6. An empty array is allowed, and equivalent to		Section 5.2.6. An empty array is allowed and is equivalent to
	omitting "errors" from the object.		omitting "errors" from the object.
	Mandatory: No.		Mandatory: No.
	5.1.3. Trigger Collection		5.1.3. Trigger Collections
	Trigger Collections MUST use a MIME Media Type of 'application/cdni;		Trigger Collections MUST use a MIME media type of "application/cdni;
	ptype=ci-trigger-collection'.		ptype=ci-trigger-collection".
	A Trigger Collection is encoded as a JSON object containing the		A Trigger Collection is encoded as a JSON object containing the
	following name/value pairs.		following name/value pairs.
	Name: triggers		Name: triggers
	Description: Links to Trigger Status Resources in the		Description: Links to Trigger Status Resources in the
	collection.		collection.
	Value: A JSON array of zero or more URLs, represented as JSON		Value: A JSON array of zero or more URLs, represented as JSON
	strings.		strings.
	Mandatory: Yes		Mandatory: Yes.
	Name: staleresourcetime		Name: staleresourcetime
	Description: The length of time for which the dCDN guarantees		Description: The length of time for which the dCDN guarantees
	to keep a completed Trigger Status Resource. After this time,		to keep a completed Trigger Status Resource. After this time,
	the dCDN SHOULD delete the Trigger Status Resource and all		the dCDN SHOULD delete the Trigger Status Resource and all
	references to it from collections.		references to it from collections.
	Value: A JSON number, which must be a positive integer,		Value: A JSON number, which must be a positive integer,
	representing time in seconds.		representing time in seconds.
	Mandatory: Yes, in the collection of all Trigger Status		Mandatory: Yes, in the collection of all Trigger Status
	Resources if the dCDN deletes stale entries. If the property		Resources if the dCDN deletes stale entries. If the property
	is present in the filtered collections, it MUST have the same		is present in the filtered collections, it MUST have the same
	value as in the collection of all Trigger Status Resources.		value as in the collection of all Trigger Status Resources.
	Names: coll-all, coll-pending, coll-active, coll-complete, coll-		Names: coll-all, coll-pending, coll-active, coll-complete,
	failed		coll-failed
	Description: Link to a Trigger Collection.		Description: Link to a Trigger Collection.
	Value: A URL represented as a JSON string.		Value: A URL represented as a JSON string.
	Mandatory: Links to all of the filtered collections are		Mandatory: Links to all of the filtered collections are
	mandatory in the collection of all Trigger Status Resources, if		mandatory in the collection of all Trigger Status Resources, if
	the dCDN implements the filtered collections. Otherwise,		the dCDN implements the filtered collections. Otherwise,
	optional.		optional.
	Name: cdn-id		Name: cdn-id
	Description: The CDN Provider Identifier of the dCDN.
	Value: A JSON string, the dCDN's CDN Provider Identifier, as		Description: The CDN PID of the dCDN.
	defined in Section 4.6.
			Value: A JSON string, the dCDN's CDN PID, as defined in
			Section 4.6.
	Mandatory: Only in the collection of all Trigger Status		Mandatory: Only in the collection of all Trigger Status
	Resources, if the dCDN implements the filtered collections.		Resources, if the dCDN implements the filtered collections.
	Optional in the filtered collections (the uCDN can always find		Optional in the filtered collections (the uCDN can always find
	the dCDN's cdn-id in the collection of all Trigger Status		the dCDN's cdn-id in the collection of all Trigger Status
	Resources, but the dCDN can choose to repeat that information		Resources, but the dCDN can choose to repeat that information
	in its implementation of filtered collections).		in its implementation of filtered collections).
	5.2. Properties of CI/T Objects		5.2. Properties of CI/T Objects
	This section defines the values that can appear in the top level		This section defines the values that can appear in the top-level
	objects described in Section 5.1, and their encodings.		objects described in Section 5.1, and their encodings.
	5.2.1. Trigger Specification		5.2.1. Trigger Specification
	A Trigger Collection is encoded as a JSON object containing the		A Trigger Collection is encoded as a JSON object containing the
	following name/value pairs.		following name/value pairs.
	An unrecognised name/value pair in the Trigger Specification object		An unrecognized name/value pair in the Trigger Specification object
	contained in a CI/T Command SHOULD be preserved in the Trigger		contained in a CI/T Command SHOULD be preserved in the Trigger
	Specification of any Trigger Status Resource it creates.		Specification of any Trigger Status Resource it creates.
	Name: type		Name: type
	Description: This property defines the type of the CI/T Trigger		Description: Defines the type of the CI/T Trigger Command.
	Command.
	Value: Trigger Type, as defined in Section 5.2.2.		Value: Trigger Type, as defined in Section 5.2.2.
	Mandatory: Yes		Mandatory: Yes.
	Name: metadata.urls		Name: metadata.urls
	Description: The uCDN URLs of the metadata the CI/T Trigger		Description: The uCDN URLs of the metadata the CI/T Trigger
	Command applies to.		Command applies to.
	Value: A JSON array of URLs represented as JSON strings.		Value: A JSON array of URLs represented as JSON strings.
	Mandatory: No, but at least one of 'metadata.*' or 'content.*'		Mandatory: No, but at least one of "metadata.*" or "content.*"
	MUST be present and non-empty.		MUST be present and non-empty.
	Name: content.urls		Name: content.urls
	Description: URLs of content the CI/T Trigger Command applies		Description: URLs of content the CI/T Trigger Command applies
	to, see Section 4.8.		to. See Section 4.8.
	Value: A JSON array of URLs represented as JSON strings.		Value: A JSON array of URLs represented as JSON strings.
	Mandatory: No, but at least one of 'metadata.*' or 'content.*'		Mandatory: No, but at least one of "metadata.*" or "content.*"
	MUST be present and non-empty.		MUST be present and non-empty.
	Name: content.ccid		Name: content.ccid
	Description: The Content Collection Identifier of content the		Description: The Content Collection IDentifier of content the
	trigger applies to. The 'ccid' is a grouping of content, as		trigger applies to. The "ccid" is a grouping of content, as
	defined by [I-D.ietf-cdni-metadata].		defined by [RFC8006].
	Value: A JSON array of strings, where each string is a Content		Value: A JSON array of strings, where each string is a Content
	Collection Identifier.		Collection IDentifier.
	Mandatory: No, but at least one of 'metadata.*' or 'content.*'		Mandatory: No, but at least one of "metadata.*" or "content.*"
	MUST be present and non-empty.		MUST be present and non-empty.
	Name: metadata.patterns		Name: metadata.patterns
	Description: The metadata the trigger applies to.		Description: The metadata the trigger applies to.
	Value: A JSON array of Pattern Match, as defined in		Value: A JSON array of PatternMatch objects, as defined in
	Section 5.2.4.		Section 5.2.4.
	Mandatory: No, but at least one of 'metadata.*' or 'content.*'		Mandatory: No, but at least one of "metadata.*" or "content.*"
	MUST be present and non-empty, and metadata.patterns MUST NOT		MUST be present and non-empty, and metadata.patterns MUST NOT
	be present if the TriggerType is Preposition.		be present if the Trigger Type is "preposition".
	Name: content.patterns		Name: content.patterns
	Description: The content data the trigger applies to.		Description: The content data the trigger applies to.
	Value: A JSON array of Pattern Match, as defined in		Value: A JSON array of PatternMatch objects, as defined in
	Section 5.2.4.		Section 5.2.4.
	Mandatory: No, but at least one of 'metadata.*' or 'content.*'		Mandatory: No, but at least one of "metadata.*" or "content.*"
	MUST be present and non-empty, and content.patterns MUST NOT be		MUST be present and non-empty, and content.patterns MUST NOT be
	present if the TriggerType is Preposition.		present if the Trigger Type is "preposition".
	5.2.2. Trigger Type		5.2.2. Trigger Type
	Trigger Type is used in a Trigger Specification to describe trigger		Trigger Type is used in a Trigger Specification to describe trigger
	action.		action.
	All trigger types MUST be registered in the IANA CI/T Trigger Types		All trigger types MUST be registered in the IANA "CDNI CI/T Trigger
	registry (see Section 7.2).		Types" registry (see Section 7.2).
	A dCDN receiving a request containing a trigger type it does not		A dCDN receiving a request containing a trigger type it does not
	recognise or does not support MUST reject the request by creating a		recognize or does not support MUST reject the request by creating a
	Trigger Status Resource with status to "failed" and the "errors"		Trigger Status Resource with a status of "failed" and the "errors"
	array containing an Error Description with error "eunsupported".		array containing an Error Description with error "eunsupported".
	The following trigger types are defined by this document:		The following trigger types are defined by this document:
	+-------------+-----------------------------------------------------+		+-------------+-----------------------------------------------------+
	| JSON String | Description |		| JSON String | Description |
	+-------------+-----------------------------------------------------+		+-------------+-----------------------------------------------------+
	| preposition | A request for the dCDN to acquire metadata or |		| preposition | A request for the dCDN to acquire metadata or |
	| | content. |		| | content. |
	| invalidate | A request for the dCDN to invalidate metadata or |		| invalidate | A request for the dCDN to invalidate metadata or |
	| | content. After servicing this request the dCDN will |		| | content. After servicing this request, the dCDN |
	| | not use the specified data without first re- |		| | will not use the specified data without first |
	| | validating it using, for example, an "If-None- |		| | revalidating it using, for example, an |
	| | Match" HTTP request. The dCDN need not erase the |		| | "If-None-Match" HTTP request. The dCDN need not |
	| | associated data. |		| | erase the associated data. |
	| purge | A request for the dCDN to erase metadata or |		| purge | A request for the dCDN to erase metadata or |
	| | content. After servicing the request, the specified |		| | content. After servicing the request, the |
	| | data MUST NOT be held on the dCDN (the dCDN should |		| | specified data MUST NOT be held on the dCDN (the |
	| | re-acquire the metadata or content from uCDN if it |		| | dCDN should reacquire the metadata or content from |
	| | needs it). |		| | the uCDN if it needs it). |
	+-------------+-----------------------------------------------------+		+-------------+-----------------------------------------------------+
	5.2.3. Trigger Status		5.2.3. Trigger Status
	This describes the current status of a Trigger. It MUST be one of		Trigger Status describes the current status of the triggered
	the JSON strings in the following table:		activity. It MUST be one of the JSON strings in the following table:
	+------------+------------------------------------------------------+		+-----------+-------------------------------------------------------+
	| JSON | Description |		| JSON | Description |
	| String | |		| String | |
	+------------+------------------------------------------------------+		+-----------+-------------------------------------------------------+
	| pending | The CI/T Trigger Command has not yet been acted |		| pending | The CI/T Trigger Command has not yet been acted upon. |
	| | upon. |		| active | The CI/T Trigger Command is currently being acted |
	| active | The CI/T Trigger Command is currently being acted |		| | upon. |
	| | upon. |		| complete | The CI/T Trigger Command completed successfully. |
	| complete | The CI/T Trigger Command completed successfully. |		| processed | The CI/T Trigger Command has been accepted, and no |
	| processed | The CI/T Trigger Command has been accepted and no |		| | further status update will be made (can be used in |
	| | further status update will be made (can be used in |		| | cases where completion cannot be confirmed). |
	| | cases where completion cannot be confirmed). |		| failed | The CI/T Trigger Command could not be completed. |
	| failed | The CI/T Trigger Command could not be completed. |		| canceling | Processing of the CI/T Trigger Command is still in |
	| cancelling | Processing of the CI/T Trigger Command is still in |		| | progress, but the CI/T Trigger Command has been |
	| | progress, but the CI/T Trigger Command has been |		| | canceled by the uCDN. |
	| | cancelled by the uCDN. |		| canceled | The CI/T Trigger Command was canceled by the uCDN. |
	| cancelled | The CI/T Trigger Command was cancelled by the uCDN. |		+-----------+-------------------------------------------------------+
	+------------+------------------------------------------------------+
	5.2.4. PatternMatch		5.2.4. PatternMatch
	A Pattern Match consists of a string pattern to match against a URI,		A PatternMatch consists of a string pattern to match against a URI,
	and flags describing the type of match.		and flags describing the type of match.
	It is encoded as a JSON object with the following name/value pairs:		It is encoded as a JSON object with the following name/value pairs:
	Name: pattern		Name: pattern
	Description: A pattern for URI matching.		Description: A pattern for URI matching.
	Value: A JSON string representing the pattern. The pattern may		Value: A JSON string representing the pattern. The pattern can
	contain the wildcards * and ?, where * matches any sequence of		contain the wildcards * and ?, where * matches any sequence of
	characters (including the empty string) and ? matches exactly		[RFC3986] pchar or "/" characters (including the empty string)
	one character. The three literals "\" , "*" and "?" MUST be		and ? matches exactly one [RFC3986] pchar character. The three
	escaped as "\\", "\*" and "\?".		literals $, * and ? MUST be escaped as $$, $* and $? (where $
			is the designated escape character). All other characters are
			treated as literals.
	Mandatory: Yes.		Mandatory: Yes.
	Name: case-sensitive		Name: case-sensitive
	Description: Flag indicating whether or not case-sensitive		Description: Flag indicating whether or not case-sensitive
	matching should be used.		matching should be used.
	Value: One of the JSON values 'true' (the matching is case-		Value: One of the JSON values "true" (the matching is case
	sensitive) or 'false' (the matching is case-insensitive).		sensitive) or "false" (the matching is case insensitive).
	Mandatory: No, default is case-insensitive match.		Mandatory: No; default is case-insensitive match.
	Name: match-query-string		Name: match-query-string
	Description: Flag indicating whether or not the query part of		Description: Flag indicating whether to include the query part
	the URI should be included in the pattern match.		of the URI when comparing against the pattern.
	Value: One of the JSON values 'true' (the full URI including		Value: One of the JSON values "true" (the full URI, including
	the query part should be compared against the given pattern),		the query part, should be compared against the given pattern)
	or 'false' (the query part of the URI should be dropped before		or "false" (the query part of the URI should be dropped before
	comparison with the given pattern).		comparison with the given pattern).
	Mandatory: No, default is 'false', the query part of the URI		Mandatory: No; default is "false". The query part of the URI
	should be dropped before comparison with the given pattern.		should be dropped before comparison with the given pattern.
	Example of case-sensitive prefix match against		Example of case-sensitive prefix match against
	"https://www.example.com/trailers/":		"https://www.example.com/trailers/":
	{		{
	"pattern": "https://www.example.com/trailers/*",		"pattern": "https://www.example.com/trailers/*",
	"case-sensitive": true		"case-sensitive": true
	}		}
	5.2.5. Absolute Time		5.2.5. Absolute Time
	A JSON number, seconds since the UNIX epoch, 00:00:00 UTC on 1		A JSON number, seconds since the UNIX epoch (00:00:00 UTC on
	January 1970.		1 January 1970).
	5.2.6. Error Description		5.2.6. Error Description
	An Error Description is used to report failure of a CI/T Command, or		An Error Description is used to report the failure of a CI/T Command
	in the activity it triggered. It is encoded as a JSON object with		or failure in the activity it triggered. It is encoded as a JSON
	the following name/value pairs:		object with the following name/value pairs:
	Name: error		Name: error
	Value: Error Code, as defined in Section 5.2.7.		Value: Error Code, as defined in Section 5.2.7.
	Mandatory: Yes.		Mandatory: Yes.
	Names: metadata.urls, content.urls, metadata.patterns,		Names: metadata.urls, content.urls, metadata.patterns,
	content.patterns		content.patterns
	Description: Metadata and content references copied from the		Description: Metadata and content references copied from the
	Trigger Specification. Only those URLs and patterns to which		Trigger Specification. Only those URLs and patterns to which
	the error applies are included in each property, but those URLs		the error applies are included in each property, but those URLs
	and patterns MUST be exactly as they appear in the request, the		and patterns MUST be exactly as they appear in the request; the
	dCDN MUST NOT generalise the URLs. (For example, if the uCDN		dCDN MUST NOT generalize the URLs. (For example, if the uCDN
	requests prepositioning of URLs "https://content.example.com/a"		requests pre-positioning of URLs
	and "https://content.example.com/b", the dCDN must not		"https://content.example.com/a" and
	generalise its error report to Pattern		"https://content.example.com/b", the dCDN must not generalize
			its error report to the pattern
	"https://content.example.com/*".)		"https://content.example.com/*".)
	Value: A JSON array of JSON strings, where each string is		Value: A JSON array of JSON strings, where each string is
	copied from a 'content.*' or 'metadata.*' value in the		copied from a "content.*" or "metadata.*" value in the
	corresponding Trigger Specification.		corresponding Trigger Specification.
	Mandatory: At least one of these name/value pairs is mandatory		Mandatory: At least one of these name/value pairs is mandatory
	in each Error Description object.		in each Error Description object.
	Name: description		Name: description
	Description: A human-readable description of the error.		Description: A human-readable description of the error.
	Value: A JSON string, the human-readable description.		Value: A JSON string, the human-readable description.
	Mandatory: No.		Mandatory: No.
	5.2.7. Error Code		5.2.7. Error Code
	This type is used by the dCDN to report failures in trigger		This type is used by the dCDN to report failures in trigger
	processing. All error codes MUST be registered in the IANA CI/T		processing. All Error Codes MUST be registered in the IANA "CDNI
	Error Codes registry (see Section 7.3). Unknown error codes MUST be		CI/T Error Codes" registry (see Section 7.3). Unknown Error Codes
	treated as fatal errors, and the request MUST NOT be automatically		MUST be treated as fatal errors, and the request MUST NOT be
	retried without modification.		automatically retried without modification.
	The following error codes are defined by this document, and MUST be		The following Error Codes are defined by this document and MUST be
	supported by an implementation of the CI/T interface.		supported by an implementation of the CI/T interface.
	+--------------+----------------------------------------------------+		+--------------+----------------------------------------------------+
	| Error Code | Description |		| Error Code | Description |
	+--------------+----------------------------------------------------+		+--------------+----------------------------------------------------+
	| emeta | The dCDN was unable to acquire metadata required |		| emeta | The dCDN was unable to acquire metadata required |
	| | to fulfil the request. |		| | to fulfill the request. |
	| econtent | The dCDN was unable to acquire content (CT/T |		| econtent | The dCDN was unable to acquire content (CI/T |
	| | preposition commands only). |		| | "preposition" commands only). |
	| eperm | The uCDN does not have permission to issue the |		| eperm | The uCDN does not have permission to issue the |
	| | CI/T Command (for example, the data is owned by |		| | CI/T Command (for example, the data is owned by |
	| | another CDN). |		| | another CDN). |
	| ereject | The dCDN is not willing to fulfil the CI/T Command |		| ereject | The dCDN is not willing to fulfill the CI/T |
	| | (for example, a preposition request for content at |		| | Command (for example, a "preposition" request for |
	| | a time when the dCDN would not accept Request |		| | content at a time when the dCDN would not accept |
	| | Routing requests from the uCDN). |		| | Request Routing requests from the uCDN). |
	| ecdn | An internal error in the dCDN or one of its |		| ecdn | An internal error in the dCDN or one of its dCDNs. |
	| | downstream CDNs. |		| ecanceled | The uCDN canceled the request. |
	| ecancelled | The uCDN cancelled the request. |
	| eunsupported | The Trigger Specification contained a "type" that |		| eunsupported | The Trigger Specification contained a "type" that |
	| | is not supported by the dCDN. No action was taken |		| | is not supported by the dCDN. No action was taken |
	| | bythe dCDN other than to create a Trigger Status |		| | by the dCDN other than to create a Trigger Status |
	| | Resource in state "failed". |		| | Resource in state "failed". |
	+--------------+----------------------------------------------------+		+--------------+----------------------------------------------------+
	6. Examples		6. Examples
	The following sections provide examples of different CI/T objects		The following subsections provide examples of different CI/T objects
	encoded as JSON.		encoded as JSON.
	Discovery of the triggers interface is out of scope of this document.		Discovery of the CI/T interface is out of scope for this document.
	In an implementation, all CI/T URLs are under the control of the		In an implementation, all CI/T URLs are under the control of the
	dCDN. The uCDN MUST NOT attempt to ascribe any meaning to individual		dCDN. The uCDN MUST NOT attempt to ascribe any meaning to individual
	elements of the path.		elements of the path.
	In examples in this section, the URL 'https://dcdn.example.com/		In examples in this section, the URL "https://dcdn.example.com/
	triggers' is used as the location of the collection of all Trigger		triggers" is used as the location of the collection of all Trigger
	Status Resources, and the CDN Provider Id of uCDN is "AS64496:1".		Status Resources, and the CDN PID of the uCDN is "AS64496:1".
	6.1. Creating Triggers		6.1. Creating Triggers
	Examples of the uCDN triggering activity in the dCDN:		Examples of the uCDN triggering activity in the dCDN:
	6.1.1. Preposition		6.1.1. Preposition
	An example of a CI/T preposition command, a POST to the collection of		Below is an example of a CI/T "preposition" command -- a POST to the
	all Trigger Status Resources.		collection of all Trigger Status Resources.
	Note that "metadata.patterns" and "content.patterns" are not allowed		Note that "metadata.patterns" and "content.patterns" are not allowed
	in a preposition Trigger Specification.		in a pre-position Trigger Specification.
	REQUEST:		REQUEST:
	POST /triggers HTTP/1.1		POST /triggers HTTP/1.1
	User-Agent: example-user-agent/0.1		User-Agent: example-user-agent/0.1
	Host: dcdn.example.com		Host: dcdn.example.com
	Accept: */*		Accept: */*
	Content-Type: application/cdni; ptype=ci-trigger-command		Content-Type: application/cdni; ptype=ci-trigger-command
	Content-Length: 352		Content-Length: 352
	{		{
	"trigger" : {		"trigger": {
	"type": "preposition",		"type": "preposition",
	"metadata.urls" : [ "https://metadata.example.com/a/b/c" ],		"metadata.urls": [ "https://metadata.example.com/a/b/c" ],
	"content.urls" : [		"content.urls": [
	"https://www.example.com/a/b/c/1",		"https://www.example.com/a/b/c/1",
	"https://www.example.com/a/b/c/2",		"https://www.example.com/a/b/c/2",
	"https://www.example.com/a/b/c/3",		"https://www.example.com/a/b/c/3",
	"https://www.example.com/a/b/c/4"		"https://www.example.com/a/b/c/4"
	]		]
	},		},
	"cdn-path" : [ "AS64496:1" ]		"cdn-path": [ "AS64496:1" ]
	}		}
	RESPONSE:		RESPONSE:
	HTTP/1.1 201 Created		HTTP/1.1 201 Created
	Date: Wed, 04 May 2016 08:48:10 GMT		Date: Wed, 04 May 2016 08:48:10 GMT
	Content-Length: 467		Content-Length: 467
	Content-Type: application/cdni; ptype=ci-trigger-status		Content-Type: application/cdni; ptype=ci-trigger-status
	Location: https://dcdn.example.com/triggers/0		Location: https://dcdn.example.com/triggers/0
	Server: example-server/0.1		Server: example-server/0.1
	skipping to change at page 28, line 10 ¶		skipping to change at page 30, line 7 ¶
	],		],
	"metadata.urls": [		"metadata.urls": [
	"https://metadata.example.com/a/b/c"		"https://metadata.example.com/a/b/c"
	],		],
	"type": "preposition"		"type": "preposition"
	}		}
	}		}
	6.1.2. Invalidate		6.1.2. Invalidate
	An example of a CI/T invalidate command, another POST to the		Below is an example of a CI/T "invalidate" command -- another POST to
	collection of all Trigger Status Resources. This instructs the dCDN		the collection of all Trigger Status Resources. This instructs the
	to re-validate the content at "https://www.example.com/a/index.html",		dCDN to revalidate the content at "https://www.example.com/a/
	as well as any metadata and content whose URLs are prefixed by		index.html", as well as any metadata and content whose URLs are
	"https://metadata.example.com/a/b/" using case-insensitive matching,		prefixed by "https://metadata.example.com/a/b/" using
	and "https://www.example.com/a/b/" respectively, using case-sensitive		case-insensitive matching, and "https://www.example.com/a/b/" using
	matching.		case-sensitive matching, respectively.
	REQUEST:		REQUEST:
	POST /triggers HTTP/1.1		POST /triggers HTTP/1.1
	User-Agent: example-user-agent/0.1		User-Agent: example-user-agent/0.1
	Host: dcdn.example.com		Host: dcdn.example.com
	Accept: */*		Accept: */*
	Content-Type: application/cdni; ptype=ci-trigger-command		Content-Type: application/cdni; ptype=ci-trigger-command
	Content-Length: 387		Content-Length: 387
	{		{
	"trigger" : {		"trigger": {
	"type": "invalidate",		"type": "invalidate",
	"metadata.patterns" : [		"metadata.patterns": [
	{ "pattern" : "https://metadata.example.com/a/b/*" }		{ "pattern": "https://metadata.example.com/a/b/*" }
	],		],
	"content.urls" : [ "https://www.example.com/a/index.html" ],		"content.urls": [ "https://www.example.com/a/index.html" ],
	"content.patterns" : [		"content.patterns": [
	{ "pattern" : "https://www.example.com/a/b/*",		{ "pattern": "https://www.example.com/a/b/*",
	"case-sensitive" : true		"case-sensitive": true
	}		}
	]		]
	},		},
	"cdn-path" : [ "AS64496:1" ]		"cdn-path": [ "AS64496:1" ]
	}		}
	RESPONSE:		RESPONSE:
	HTTP/1.1 201 Created		HTTP/1.1 201 Created
	Date: Wed, 04 May 2016 08:48:11 GMT		Date: Wed, 04 May 2016 08:48:11 GMT
	Content-Length: 545		Content-Length: 545
	Content-Type: application/cdni; ptype=ci-trigger-status		Content-Type: application/cdni; ptype=ci-trigger-status
	Location: https://dcdn.example.com/triggers/1		Location: https://dcdn.example.com/triggers/1
	Server: example-server/0.1		Server: example-server/0.1
	skipping to change at page 29, line 33 ¶		skipping to change at page 32, line 8 ¶
	"pattern": "https://metadata.example.com/a/b/*"		"pattern": "https://metadata.example.com/a/b/*"
	}		}
	],		],
	"type": "invalidate"		"type": "invalidate"
	}		}
	}		}
	6.2. Examining Trigger Status		6.2. Examining Trigger Status
	Once Trigger Status Resources have been created, the uCDN can check		Once Trigger Status Resources have been created, the uCDN can check
	their status as shown in these examples.		their status as shown in the following examples.
	6.2.1. Collection of All Triggers		6.2.1. Collection of All Triggers
	The uCDN can fetch the collection of all Trigger Status Resources it		The uCDN can fetch the collection of all Trigger Status Resources it
	has created that have not yet been deleted or removed as expired.		has created that have not yet been deleted or removed as expired.
	After creation of the "preposition" and "invalidate" triggers shown		After creation of the "preposition" and "invalidate" triggers shown
	above, this collection might look as follows:		above, this collection might look as follows:
	REQUEST:		REQUEST:
	skipping to change at page 30, line 40 ¶		skipping to change at page 33, line 9 ¶
	"triggers": [		"triggers": [
	"https://dcdn.example.com/triggers/0",		"https://dcdn.example.com/triggers/0",
	"https://dcdn.example.com/triggers/1"		"https://dcdn.example.com/triggers/1"
	]		]
	}		}
	6.2.2. Filtered Collections of Trigger Status Resources		6.2.2. Filtered Collections of Trigger Status Resources
	The filtered collections are also available to the uCDN. Before the		The filtered collections are also available to the uCDN. Before the
	dCDN starts processing the two CI/T Trigger Commands shown above,		dCDN starts processing the two CI/T Trigger Commands shown above,
	both will appear in the collection of Pending Triggers, for example:		both will appear in the collection of pending triggers. For example:
	REQUEST:		REQUEST:
	GET /triggers/pending HTTP/1.1		GET /triggers/pending HTTP/1.1
	User-Agent: example-user-agent/0.1		User-Agent: example-user-agent/0.1
	Host: dcdn.example.com		Host: dcdn.example.com
	Accept: */*		Accept: */*
	RESPONSE:		RESPONSE:
	skipping to change at page 32, line 30 ¶		skipping to change at page 34, line 23 ¶
	Date: Wed, 04 May 2016 08:48:11 GMT		Date: Wed, 04 May 2016 08:48:11 GMT
	Content-Type: application/cdni; ptype=ci-trigger-collection		Content-Type: application/cdni; ptype=ci-trigger-collection
	{		{
	"staleresourcetime": 86400,		"staleresourcetime": 86400,
	"triggers": []		"triggers": []
	}		}
	6.2.3. Individual Trigger Status Resources		6.2.3. Individual Trigger Status Resources
	The Trigger Status Resources can also be examined for detail about		The Trigger Status Resources can also be examined for details about
	individual CI/T Trigger Commands. For example, for the CI/T		individual CI/T Trigger Commands. For example, for the CI/T
	"preposition" and "invalidate" commands from previous examples:		"preposition" and "invalidate" commands from previous examples:
	REQUEST:		REQUEST:
	GET /triggers/0 HTTP/1.1		GET /triggers/0 HTTP/1.1
	User-Agent: example-user-agent/0.1		User-Agent: example-user-agent/0.1
	Host: dcdn.example.com		Host: dcdn.example.com
	Accept: */*		Accept: */*
	skipping to change at page 34, line 47 ¶		skipping to change at page 36, line 28 ¶
	],		],
	"metadata.patterns": [		"metadata.patterns": [
	{		{
	"pattern": "https://metadata.example.com/a/b/*"		"pattern": "https://metadata.example.com/a/b/*"
	}		}
	],		],
	"type": "invalidate"		"type": "invalidate"
	}		}
	}		}
	6.2.4. Polling for Change		6.2.4. Polling for Changes in Status
	The uCDN SHOULD use the Entity Tags of collections or Trigger Status		The uCDN SHOULD use the ETags of collections or Trigger Status
	Resources when polling for change in status, as shown in the		Resources when polling for changes in status, as shown in the
	following examples:		following examples:
	REQUEST:		REQUEST:
	GET /triggers/pending HTTP/1.1		GET /triggers/pending HTTP/1.1
	User-Agent: example-user-agent/0.1		User-Agent: example-user-agent/0.1
	Host: dcdn.example.com		Host: dcdn.example.com
	Accept: */*		Accept: */*
	If-None-Match: "4331492443626270781"		If-None-Match: "4331492443626270781"
	skipping to change at page 35, line 44 ¶		skipping to change at page 37, line 25 ¶
	HTTP/1.1 304 Not Modified		HTTP/1.1 304 Not Modified
	Content-Length: 0		Content-Length: 0
	Expires: Wed, 04 May 2016 08:49:10 GMT		Expires: Wed, 04 May 2016 08:49:10 GMT
	Server: example-server/0.1		Server: example-server/0.1
	ETag: "6990548174277557683"		ETag: "6990548174277557683"
	Cache-Control: max-age=60		Cache-Control: max-age=60
	Date: Wed, 04 May 2016 08:48:10 GMT		Date: Wed, 04 May 2016 08:48:10 GMT
	Content-Type: application/cdni; ptype=ci-trigger-status		Content-Type: application/cdni; ptype=ci-trigger-status
	When the CI/T Trigger Command is complete, the contents of the		When the CI/T Trigger Command is complete, the contents of the
	filtered collections will be updated along with their Entity Tags.		filtered collections will be updated along with their ETags. For
	For example, when the two example CI/T Trigger Commands are complete,		example, when the two example CI/T Trigger Commands are complete, the
	the collections of pending and complete Trigger Status Resources		collections of pending and complete Trigger Status Resources might
	might look like:		look like:
	REQUEST:		REQUEST:
	GET /triggers/pending HTTP/1.1		GET /triggers/pending HTTP/1.1
	User-Agent: example-user-agent/0.1		User-Agent: example-user-agent/0.1
	Host: dcdn.example.com		Host: dcdn.example.com
	Accept: */*		Accept: */*
	RESPONSE:		RESPONSE:
	skipping to change at page 38, line 35 ¶		skipping to change at page 39, line 35 ¶
	{		{
	"staleresourcetime": 86400,		"staleresourcetime": 86400,
	"triggers": [		"triggers": [
	"https://dcdn.example.com/triggers/1"		"https://dcdn.example.com/triggers/1"
	]		]
	}		}
	6.2.6. Error Reporting		6.2.6. Error Reporting
	In this example the uCDN has requested prepositioning of		In this example, the uCDN has requested pre-positioning of
	"https://newsite.example.com/index.html", but the dCDN was unable to		"https://newsite.example.com/index.html", but the dCDN was unable to
	locate metadata for that site:		locate metadata for that site:
	REQUEST:		REQUEST:
	GET /triggers/2 HTTP/1.1		GET /triggers/2 HTTP/1.1
	User-Agent: example-user-agent/0.1		User-Agent: example-user-agent/0.1
	Host: dcdn.example.com		Host: dcdn.example.com
	Accept: */*		Accept: */*
	skipping to change at page 39, line 47 ¶		skipping to change at page 40, line 40 ¶
	"trigger": {		"trigger": {
	"content.urls": [		"content.urls": [
	"https://newsite.example.com/index.html"		"https://newsite.example.com/index.html"
	],		],
	"type": "preposition"		"type": "preposition"
	}		}
	}		}
	7. IANA Considerations		7. IANA Considerations
	[RFC Editor Note: Please replace references to [RFCthis] in this
	section with this document's RFC number before publication.]
	7.1. CDNI Payload Type Parameter Registrations		7.1. CDNI Payload Type Parameter Registrations
	The IANA is requested to register the following new Payload Types in		The IANA is requested to register the following new Payload Types in
	the CDNI Payload Type Parameter registry defined by [RFC7736], for		the "CDNI Payload Types" registry defined by [RFC7736], for use with
	use with the 'application/cdni' MIME media type.		the "application/cdni" MIME media type.
	+-----------------------+---------------+		+-----------------------+---------------+
	| Payload Type | Specification |		| Payload Type | Specification |
	+-----------------------+---------------+		+-----------------------+---------------+
	| ci-trigger-command | [RFCthis] |		| ci-trigger-command | RFC 8007 |
	| ci-trigger-status | [RFCthis] |		| ci-trigger-status | RFC 8007 |
	| ci-trigger-collection | [RFCthis] |		| ci-trigger-collection | RFC 8007 |
	+-----------------------+---------------+		+-----------------------+---------------+
	7.2. CDNI CI/T Trigger Types Registry		7.2. "CDNI CI/T Trigger Types" Registry
	The IANA is requested to create a new "CDNI CI/T Trigger Types"		The IANA is requested to create a new "CDNI CI/T Trigger Types"
	subregistry under the "Content Delivery Networks Interconnection		subregistry under the "Content Delivery Network Interconnection
	(CDNI) Parameters" registry.		(CDNI) Parameters" registry.
	Additions to the CDNI CI/T Error Code Registry will be made via "RFC		Additions to the "CDNI CI/T Trigger Types" registry will be made via
	Required" as defined in [RFC5226].		the RFC Required policy as defined in [RFC5226].
	The initial contents of the CDNI CI/T Trigger Types Registry comprise		The initial contents of the "CDNI CI/T Trigger Types" registry
	the names and descriptions listed in section Section 5.2.2 of this		comprise the names and descriptions listed in Section 5.2.2 of this
	document, with this document acting as the specification.		document, with this document acting as the specification.
	7.3. CDNI CI/T Error Codes Registry		7.3. "CDNI CI/T Error Codes" Registry
	The IANA is requested to create a new "CDNI CI/T Error Codes"		The IANA is requested to create a new "CDNI CI/T Error Codes"
	subregistry under the "Content Delivery Networks Interconnection		subregistry under the "Content Delivery Network Interconnection
	(CDNI) Parameters" registry.		(CDNI) Parameters" registry.
	Additions to the CDNI CI/T Error Codes Registry will be made via		Additions to the "CDNI CI/T Error Codes" registry will be made via
	"Specification Required" as defined in [RFC5226]. The Designated		the Specification Required policy as defined in [RFC5226]. The
	Expert will verify that new error code registrations do not duplicate		Designated Expert will verify that new Error Code registrations do
	existing error code definitions (in name or functionality), prevent		not duplicate existing Error Code definitions (in name or
	gratuitous additions to the namespace, and prevent any additions to		functionality), prevent gratuitous additions to the namespace, and
	the namespace that would impair the interoperability of CDNI		prevent any additions to the namespace that would impair the
	implementations.		interoperability of CDNI implementations.
	The initial contents of the CDNI CI/T Error Codes Registry comprise		The initial contents of the "CDNI CI/T Error Codes" registry comprise
	the names and descriptions of the Error Codes listed in Section 5.2.7		the names and descriptions of the Error Codes listed in Section 5.2.7
	of this document, with this document acting as the specification.		of this document, with this document acting as the specification.
	8. Security Considerations		8. Security Considerations
	The CI/T interface provides a mechanism to allow a uCDN to generate		The CI/T interface provides a mechanism to allow a uCDN to generate
	requests into the dCDN and to inspect its own CI/T requests and their		requests into the dCDN and to inspect its own CI/T requests and their
	current state. The CI/T interface does not allow access to or		current states. The CI/T interface does not allow access to, or
	modification of the uCDN or dCDN metadata relating to content		modification of, the uCDN or dCDN metadata relating to content
	delivery, or to the content itself. It can only control the presence		delivery or to the content itself. It can only control the presence
	of that metadata in the dCDN, and the processing work and network		of that metadata in the dCDN, and the processing work and network
	utilisation involved in ensuring that presence.		utilization involved in ensuring that presence.
	By examining pre-positioning requests to a dCDN, and correctly		By examining "preposition" requests to a dCDN, and correctly
	interpreting content and metadata URLs, an attacker could learn the		interpreting content and metadata URLs, an attacker could learn the
	uCDN or content owner's predictions for future content popularity.		uCDN's or content owner's predictions for future content popularity.
	By examining invalidate or purge requests, an attacker could learn		By examining "invalidate" or "purge" requests, an attacker could
	about changes in the content owner's catalogue.		learn about changes in the content owner's catalog.
	By injecting CI/T commands an attacker, or a misbehaving uCDN, would		By injecting CI/T Commands, an attacker or a misbehaving uCDN would
	generate work in the dCDN and uCDN as they process those requests.		generate work in the dCDN and uCDN as they process those requests.
	And so would a man in the middle attacker modifying valid CI/T		So would a man-in-the-middle attacker modifying valid CI/T Commands
	commands generated by the uCDN. In both cases, that would decrease		generated by the uCDN. In both cases, that would decrease the dCDN's
	the dCDN caching efficiency by causing it to unnecessarily acquire or		caching efficiency by causing it to unnecessarily acquire or
	re-acquire content metadata and/or content.		reacquire content metadata and/or content.
	A dCDN implementation of CI/T MUST restrict the actions of a uCDN to		A dCDN implementation of CI/T MUST restrict the actions of a uCDN to
	the data corresponding to that uCDN. Failure to do so would allow		the data corresponding to that uCDN. Failure to do so would allow
	uCDNs to detrimentally affect each other's efficiency by generating		uCDNs to detrimentally affect each other's efficiency by generating
	unnecessary acquisition or re-acquisition load.		unnecessary acquisition or reacquisition load.
	An origin that chooses to delegate its delivery to a CDN is trusting		An origin that chooses to delegate its delivery to a CDN is trusting
	that CDN to deliver content on its behalf, CDN-interconnection is an		that CDN to deliver content on its behalf; the interconnection of
	extension of that trust to downstream CDNs. That trust relationship		CDNs is an extension of that trust to dCDNs. That trust relationship
	is a commercial arrangement, outside the scope of the CDNi protocols.		is a commercial arrangement, outside the scope of the CDNI protocols.
	So, while a malicious CDN could deliberately generate load on a dCDN		So, while a malicious CDN could deliberately generate load on a dCDN
	using the CI/T, the protocol does not otherwise attempt to address		using the CI/T interface, the protocol does not otherwise attempt to
	malicious behaviour between interconnected CDNs.		address malicious behavior between interconnected CDNs.
	8.1. Authentication, Authorization, Confidentiality, Integrity		8.1. Authentication, Authorization, Confidentiality, Integrity
	Protection		Protection
	A CI/T implementation MUST support TLS transport for HTTP (https) as		A CI/T implementation MUST support Transport Layer Security (TLS)
	per [RFC2818] and [RFC7230].		transport for HTTP (HTTPS) as per [RFC2818] and [RFC7230].
	TLS MUST be used by the server-side (dCDN) and the client-side (uCDN)		TLS MUST be used by the server side (dCDN) and the client side (uCDN)
	of the CI/T interface, including authentication of the remote end,		of the CI/T interface, including authentication of the remote end,
	unless alternate methods are used for ensuring the security of the		unless alternate methods are used for ensuring the security of the
	information in the CI/T interface requests and responses (such as		information in the CI/T interface requests and responses (such as
	setting up an IPsec tunnel between the two CDNs or using a physically		setting up an IPsec tunnel between the two CDNs or using a physically
	secured internal network between two CDNs that are owned by the same		secured internal network between two CDNs that are owned by the same
	corporate entity).		corporate entity).
	The use of TLS for transport of the CI/T interface allows:		The use of TLS for transport of the CI/T interface allows the dCDN
			and the uCDN to authenticate each other using TLS client
	o The dCDN and the uCDN to authenticate each other using TLS client		authentication and TLS server authentication.
	auth and TLS server auth.
	And, once they have mutually authenticated each other, it allows:		Once the dCDN and the uCDN have mutually authenticated each other,
			TLS allows:
	o The dCDN and the uCDN to authorize each other (to ensure they are		o The dCDN and the uCDN to authorize each other (to ensure that they
	receiving CI/T Commands from, or reporting status to, an		are receiving CI/T Commands from, or reporting status to, an
	authorized CDN).		authorized CDN).
	o CDNI commands and responses to be transmitted with		o CDNI commands and responses to be transmitted with
	confidentiality.		confidentiality.
	o Protection of the integrity of CDNI commands and responses.		o Protection of the integrity of CDNI commands and responses.
	When TLS is used, the general TLS usage guidance in [RFC7525] MUST be		When TLS is used, the general TLS usage guidance in [RFC7525] MUST be
	followed.		followed.
	The mechanisms for access control are dCDN-specific, not standardised		The mechanisms for access control are dCDN-specific and are not
	as part of this CI/T specification.		standardized as part of this CI/T specification.
	HTTP requests that attempt to access or operate on CI/T data		HTTP requests that attempt to access or operate on CI/T data
	belonging to another CDN MUST be rejected using, for example, HTTP		belonging to another CDN MUST be rejected using, for example,
	"403 Forbidden" or "404 Not Found". This is intended to prevent		HTTP 403 ("Forbidden") or 404 ("Not Found"). This is intended to
	unauthorised users from generating unnecessary load in dCDN or uCDN		prevent unauthorized users from generating unnecessary load in dCDNs
	due to revalidation, reacquisition, or unnecessary acquisition.		or uCDNs due to revalidation, reacquisition, or unnecessary
			acquisition.
	When deploying a network of interconnected CDNs, the possible		When deploying a network of interconnected CDNs, the possible
	inefficiencies related to the "diamond" configuration discussed in		inefficiencies related to the diamond configuration discussed in
	Section 2.2.1 should be considered.		Section 2.2.1 should be considered.
	8.2. Denial of Service		8.2. Denial of Service
	This document does not define a specific mechanism to protect against		This document does not define a specific mechanism to protect against
	Denial of Service (DoS) attacks on the CI/T. However, CI/T endpoints		Denial-of-Service (DoS) attacks on the CI/T interface. However, CI/T
	can be protected against DoS attacks through the use of TLS transport		endpoints can be protected against DoS attacks through the use of TLS
	and/or via mechanisms outside the scope of the CI/T interface, such		transport and/or via mechanisms outside the scope of the CI/T
	as firewalling or use of Virtual Private Networks (VPNs).		interface, such as firewalling or the use of Virtual Private Networks
			(VPNs).
	Depending on the implementation, triggered activity may consume		Depending on the implementation, triggered activity may consume
	significant processing and bandwidth in the dCDN. A malicious or		significant processing and bandwidth in the dCDN. A malicious or
	faulty uCDN could use this to generate unnecessary load in the dCDN.		faulty uCDN could use this to generate unnecessary load in the dCDN.
	The dCDN should consider mechanisms to avoid overload, for example by		The dCDN should consider mechanisms to avoid overload -- for example,
	rate-limiting acceptance or processing of CI/T Commands, or batching		by rate-limiting acceptance or processing of CI/T Commands, or by
	up its processing.		performing batch processing.
	8.3. Privacy		8.3. Privacy
	The CI/T protocol does not carry any information about individual End		The CI/T protocol does not carry any information about individual end
	Users of a CDN, there are no privacy concerns for End Users.		users of a CDN; there are no privacy concerns for end users.
	The CI/T protocol does carry information which could be considered		The CI/T protocol does carry information that could be considered
	commercially sensitive by CDN operators and content owners. The use		commercially sensitive by CDN operators and content owners. The use
	of mutually authenticated TLS to establish a secure session for the		of mutually authenticated TLS to establish a secure session for the
	transport of CI/T data, as discussed in Section 8.1, provides		transport of CI/T data, as discussed in Section 8.1, provides
	confidentiality while the CI/T data is in transit, and prevents		confidentiality while the CI/T data is in transit and prevents
	parties other than the authorised dCDN from gaining access to that		parties other than the authorized dCDN from gaining access to that
	data. The dCDN MUST ensure that it only exposes CI/T data related to		data. The dCDN MUST ensure that it only exposes CI/T data related to
	a uCDN to clients it has authenticated as belonging to that uCDN.		a uCDN to clients it has authenticated as belonging to that uCDN.
	9. Acknowledgements		9. References
	The authors thank Kevin Ma for his input, and Carsten Bormann for his
	review and formalization of the JSON data.
	10. References
	10.1. Normative References
	[I-D.ietf-cdni-metadata]		9.1. Normative References
	Niven-Jenkins, B., Murray, R., Caulfield, M., and K. Ma,
	"CDN Interconnection Metadata", draft-ietf-cdni-
	metadata-16 (work in progress), April 2016.
	[RFC1930] Hawkinson, J. and T. Bates, "Guidelines for creation,		[RFC1930] Hawkinson, J. and T. Bates, "Guidelines for creation,
	selection, and registration of an Autonomous System (AS)",		selection, and registration of an Autonomous System (AS)",
	BCP 6, RFC 1930, DOI 10.17487/RFC1930, March 1996,		BCP 6, RFC 1930, DOI 10.17487/RFC1930, March 1996,
	<http://www.rfc-editor.org/info/rfc1930>.		<http://www.rfc-editor.org/info/rfc1930>.
	[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate		[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
	Requirement Levels", BCP 14, RFC 2119, March 1997.		Requirement Levels", BCP 14, RFC 2119,
			DOI 10.17487/RFC2119, March 1997,
			<http://www.rfc-editor.org/info/rfc2119>.
	[RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818, May 2000.		[RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818,
			DOI 10.17487/RFC2818, May 2000,
			<http://www.rfc-editor.org/info/rfc2818>.
			[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
			Resource Identifier (URI): Generic Syntax", STD 66,
			RFC 3986, DOI 10.17487/RFC3986, January 2005,
			<http://www.rfc-editor.org/info/rfc3986>.
	[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an		[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
	IANA Considerations Section in RFCs", BCP 26, RFC 5226,		IANA Considerations Section in RFCs", BCP 26, RFC 5226,
	DOI 10.17487/RFC5226, May 2008,		DOI 10.17487/RFC5226, May 2008,
	<http://www.rfc-editor.org/info/rfc5226>.		<http://www.rfc-editor.org/info/rfc5226>.
	[RFC6707] Niven-Jenkins, B., Le Faucheur, F., and N. Bitar, "Content		[RFC6707] Niven-Jenkins, B., Le Faucheur, F., and N. Bitar, "Content
	Distribution Network Interconnection (CDNI) Problem		Distribution Network Interconnection (CDNI) Problem
	Statement", RFC 6707, September 2012.		Statement", RFC 6707, DOI 10.17487/RFC6707,
			September 2012, <http://www.rfc-editor.org/info/rfc6707>.
	[RFC7159] Bray, T., "The JavaScript Object Notation (JSON) Data		[RFC7159] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
	Interchange Format", RFC 7159, March 2014.		Interchange Format", RFC 7159, DOI 10.17487/RFC7159,
			March 2014, <http://www.rfc-editor.org/info/rfc7159>.
	[RFC7230] Fielding, R. and J. Reschke, "Hypertext Transfer Protocol		[RFC7230] Fielding, R., Ed., and J. Reschke, Ed., "Hypertext
	(HTTP/1.1): Message Syntax and Routing", RFC 7230, June		Transfer Protocol (HTTP/1.1): Message Syntax and Routing",
	2014.		RFC 7230, DOI 10.17487/RFC7230, June 2014,
			<http://www.rfc-editor.org/info/rfc7230>.
	[RFC7231] Fielding, R. and J. Reschke, "Hypertext Transfer Protocol		[RFC7231] Fielding, R., Ed., and J. Reschke, Ed., "Hypertext
	(HTTP/1.1): Semantics and Content", RFC 7231, June 2014.		Transfer Protocol (HTTP/1.1): Semantics and Content",
			RFC 7231, DOI 10.17487/RFC7231, June 2014,
			<http://www.rfc-editor.org/info/rfc7231>.
	[RFC7232] Fielding, R. and J. Reschke, "Hypertext Transfer Protocol		[RFC7232] Fielding, R., Ed., and J. Reschke, Ed., "Hypertext
	(HTTP/1.1): Conditional Requests", RFC 7232, June 2014.		Transfer Protocol (HTTP/1.1): Conditional Requests",
			RFC 7232, DOI 10.17487/RFC7232, June 2014,
			<http://www.rfc-editor.org/info/rfc7232>.
	[RFC7525] Sheffer, Y., Holz, R., and P. Saint-Andre,		[RFC7525] Sheffer, Y., Holz, R., and P. Saint-Andre,
	"Recommendations for Secure Use of Transport Layer		"Recommendations for Secure Use of Transport Layer
	Security (TLS) and Datagram Transport Layer Security		Security (TLS) and Datagram Transport Layer Security
	(DTLS)", BCP 195, RFC 7525, May 2015.		(DTLS)", BCP 195, RFC 7525, DOI 10.17487/RFC7525,
			May 2015, <http://www.rfc-editor.org/info/rfc7525>.
	10.2. Informative References		[RFC8006] Niven-Jenkins, B., Murray, R., Caulfield, M., and K. Ma,
			"Content Delivery Network Interconnection (CDNI)
			Metadata", RFC 8006, DOI 10.17487/RFC8006, December 2016,
			<http://www.rfc-editor.org/info/rfc8006>.
	[I-D.greevenbosch-appsawg-cbor-cddl]		9.2. Informative References
			[CBOR-CDDL]
	Vigano, C. and H. Birkholz, "CBOR data definition language		Vigano, C. and H. Birkholz, "CBOR data definition language
	(CDDL): a notational convention to express CBOR data		(CDDL): a notational convention to express CBOR data
	structures", draft-greevenbosch-appsawg-cbor-cddl-08 (work		structures", Work in Progress,
	in progress), March 2016.		draft-greevenbosch-appsawg-cbor-cddl-09, September 2016.
	[I-D.ietf-cdni-redirection]
	Niven-Jenkins, B. and R. Brandenburg, "Request Routing
	Redirection interface for CDN Interconnection", draft-
	ietf-cdni-redirection-18 (work in progress), April 2016.
	[RFC7336] Peterson, L., Davie, B., and R. van Brandenburg,		[RFC7336] Peterson, L., Davie, B., and R. van Brandenburg, Ed.,
	"Framework for Content Distribution Network		"Framework for Content Distribution Network
	Interconnection (CDNI)", RFC 7336, August 2014.		Interconnection (CDNI)", RFC 7336, DOI 10.17487/RFC7336,
			August 2014, <http://www.rfc-editor.org/info/rfc7336>.
	[RFC7337] Leung, K. and Y. Lee, "Content Distribution Network		[RFC7337] Leung, K., Ed., and Y. Lee, Ed., "Content Distribution
	Interconnection (CDNI) Requirements", RFC 7337, August		Network Interconnection (CDNI) Requirements", RFC 7337,
	2014.		DOI 10.17487/RFC7337, August 2014,
			<http://www.rfc-editor.org/info/rfc7337>.
	[RFC7736] Ma, K., "Content Delivery Network Interconnection (CDNI)		[RFC7736] Ma, K., "Content Delivery Network Interconnection (CDNI)
	Media Type Registration", RFC 7736, DOI 10.17487/RFC7736,		Media Type Registration", RFC 7736, DOI 10.17487/RFC7736,
	December 2015, <http://www.rfc-editor.org/info/rfc7736>.		December 2015, <http://www.rfc-editor.org/info/rfc7736>.
			[RFC7975] Niven-Jenkins, B., Ed., and R. van Brandenburg, Ed.,
			"Request Routing Redirection Interface for Content
			Delivery Network (CDN) Interconnection", RFC 7975,
			DOI 10.17487/RFC7975, October 2016,
			<http://www.rfc-editor.org/info/rfc7975>.
	Appendix A. Formalization of the JSON Data		Appendix A. Formalization of the JSON Data
	This appendix is non-normative.		This appendix is non-normative.
	The JSON data described in this document has been formalised using		The JSON data described in this document has been formalized using
	CDDL [I-D.greevenbosch-appsawg-cbor-cddl] as follows:		the CBOR Data Definition Language (CDDL) [CBOR-CDDL] (where "CBOR"
			means "Concise Binary Object Representation"), as follows:
	CIT-object = CIT-command / Trigger-Status-Resource / Trigger-Collection		CIT-object = CIT-command / Trigger-Status-Resource / Trigger-Collection
	CIT-command ; use media type application/cdni; ptype=ci-trigger-command		CIT-command ; use media type application/cdni; ptype=ci-trigger-command
	= {		= {
	? trigger: Triggerspec		? trigger: Triggerspec
	? cancel: [* URI]		? cancel: [* URI]
	cdn-path: [* Cdn-PID]		cdn-path: [* Cdn-PID]
	}		}
	skipping to change at page 45, line 43 ¶		skipping to change at page 47, line 44 ¶
	triggers: [* URI]		triggers: [* URI]
	? staleresourcetime: int ; time in seconds		? staleresourcetime: int ; time in seconds
	? coll-all: URI		? coll-all: URI
	? coll-pending: URI		? coll-pending: URI
	? coll-active: URI		? coll-active: URI
	? coll-complete: URI		? coll-complete: URI
	? coll-failed: URI		? coll-failed: URI
	? cdn-id: Cdn-PID		? cdn-id: Cdn-PID
	}		}
	Triggerspec = { ; 5.2.1		Triggerspec = { ; see Section 5.2.1
	type: Trigger-Type		type: Trigger-Type
	? metadata.urls: [* URI]		? metadata.urls: [* URI]
	? content.urls: [* URI]		? content.urls: [* URI]
	? content.ccid: [* Ccid]		? content.ccid: [* Ccid]
	? metadata.patterns: [* Pattern-Match]		? metadata.patterns: [* Pattern-Match]
	? content.patterns: [* Pattern-Match]		? content.patterns: [* Pattern-Match]
	}		}
			Trigger-Type = "preposition" / "invalidate"
			/ "purge" ; see Section 5.2.2
	Trigger-Type = "preposition" / "invalidate" / "purge" ; 5.2.2
	Trigger-Status = "pending" / "active" / "complete" / "processed"		Trigger-Status = "pending" / "active" / "complete" / "processed"
	/ "failed" / "cancelling" / "cancelled" ; 5.2.3		/ "failed" / "cancelling" / "cancelled" ; see Section 5.2.3
	Pattern-Match = { ; 5.2.4		Pattern-Match = { ; see Section 5.2.4
	pattern: tstr		pattern: tstr
	? case-sensitive: bool		? case-sensitive: bool
	? match-query-string: bool		? match-query-string: bool
	}		}
	Absolute-Time = number ; seconds since UNIX epoch, 5.2.5		Absolute-Time = number ; seconds since UNIX epoch (Section 5.2.5)
	Error-Description = { ; 5.2.6		Error-Description = { ; see Section 5.2.6
	error: Error-Code		error: Error-Code
	? metadata.urls: [* URI]		? metadata.urls: [* URI]
	? content.urls: [* URI]		? content.urls: [* URI]
	? metadata.patterns: [* Pattern-Match]		? metadata.patterns: [* Pattern-Match]
	? content.patterns: [* Pattern-Match]		? content.patterns: [* Pattern-Match]
	? description: tstr		? description: tstr
	}		}
	Error-Code = "emeta" / "econtent" / "eperm" / "ereject"		Error-Code = "emeta" / "econtent" / "eperm" / "ereject"
	/ "ecdn" / "ecancelled" ; 5.2.7		/ "ecdn" / "ecanceled" ; see Section 5.2.7
	Ccid = tstr ; see I-D.ietf-cdni-metadata		Ccid = tstr ; see RFC 8006
	Cdn-PID = tstr .regexp "AS[0-9]+:[0-9]+"		Cdn-PID = tstr .regexp "AS[0-9]+:[0-9]+"
	URI = tstr		URI = tstr
			Acknowledgments
			The authors thank Kevin Ma for his input, and Carsten Bormann for his
			review and formalization of the JSON data.
	Authors' Addresses		Authors' Addresses
	Rob Murray		Rob Murray
	Nokia		Nokia
	3 Ely Road		3 Ely Road
	Milton, Cambridge CB24 6DD		Milton, Cambridge CB24 6DD
	UK		United Kingdom
	Email: rob.murray@nokia.com		Email: rob.murray@nokia.com
	Ben Niven-Jenkins		Ben Niven-Jenkins
	Nokia		Nokia
	3 Ely Road		3 Ely Road
	Milton, Cambridge CB24 6DD		Milton, Cambridge CB24 6DD
	UK		United Kingdom
	Email: ben.niven-jenkins@nokia.com		Email: ben.niven-jenkins@nokia.com
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