< draft-ietf-netconf-restconf-notif-07.txt		draft-ietf-netconf-restconf-notif-08.txt >
	NETCONF E. Voit		NETCONF E. Voit
	Internet-Draft R. Rahman		Internet-Draft R. Rahman
	Intended status: Standards Track E. Nilsen-Nygaard		Intended status: Standards Track E. Nilsen-Nygaard
	Expires: March 16, 2019 Cisco Systems		Expires: April 7, 2019 Cisco Systems
	A. Clemm		A. Clemm
	Huawei		Huawei
	A. Bierman		A. Bierman
	YumaWorks		YumaWorks
	September 12, 2018		October 4, 2018
	RESTCONF Transport for Event Notifications		RESTCONF Transport for Event Notifications
	draft-ietf-netconf-restconf-notif-07		draft-ietf-netconf-restconf-notif-08
	Abstract		Abstract
	This document defines a RESTCONF binding to the dynamic subscription		This document defines a RESTCONF binding to the dynamic subscription
	capability of both subscribed notifications and YANG-Push.		capability of both subscribed notifications and YANG-Push.
	Subscriptions to publisher defined event streams or nodes/subtrees of		Subscriptions to publisher defined event streams or nodes/subtrees of
	YANG Datastores is supported.		YANG Datastores is supported.
	Status of This Memo		Status of This Memo
	skipping to change at page 1, line 38 ¶		skipping to change at page 1, line 38 ¶
	Internet-Drafts are working documents of the Internet Engineering		Internet-Drafts are working documents of the Internet Engineering
	Task Force (IETF). Note that other groups may also distribute		Task Force (IETF). Note that other groups may also distribute
	working documents as Internet-Drafts. The list of current Internet-		working documents as Internet-Drafts. The list of current Internet-
	Drafts is at https://datatracker.ietf.org/drafts/current/.		Drafts is at https://datatracker.ietf.org/drafts/current/.
	Internet-Drafts are draft documents valid for a maximum of six months		Internet-Drafts are draft documents valid for a maximum of six months
	and may be updated, replaced, or obsoleted by other documents at any		and may be updated, replaced, or obsoleted by other documents at any
	time. It is inappropriate to use Internet-Drafts as reference		time. It is inappropriate to use Internet-Drafts as reference
	material or to cite them other than as "work in progress."		material or to cite them other than as "work in progress."
	This Internet-Draft will expire on March 16, 2019.		This Internet-Draft will expire on April 7, 2019.
	Copyright Notice		Copyright Notice
	Copyright (c) 2018 IETF Trust and the persons identified as the		Copyright (c) 2018 IETF Trust and the persons identified as the
	document authors. All rights reserved.		document authors. All rights reserved.
	This document is subject to BCP 78 and the IETF Trust's Legal		This document is subject to BCP 78 and the IETF Trust's Legal
	Provisions Relating to IETF Documents		Provisions Relating to IETF Documents
	(https://trustee.ietf.org/license-info) in effect on the date of		(https://trustee.ietf.org/license-info) in effect on the date of
	publication of this document. Please review these documents		publication of this document. Please review these documents
	skipping to change at page 2, line 17 ¶		skipping to change at page 2, line 17 ¶
	described in the Simplified BSD License.		described in the Simplified BSD License.
	Table of Contents		Table of Contents
	1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2		1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
	2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3		2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
	3. Dynamic Subscriptions . . . . . . . . . . . . . . . . . . . . 3		3. Dynamic Subscriptions . . . . . . . . . . . . . . . . . . . . 3
	3.1. Transport Connectivity . . . . . . . . . . . . . . . . . 4		3.1. Transport Connectivity . . . . . . . . . . . . . . . . . 4
	3.2. Discovery . . . . . . . . . . . . . . . . . . . . . . . . 4		3.2. Discovery . . . . . . . . . . . . . . . . . . . . . . . . 4
	3.3. RESTCONF RPCs and HTTP Status Codes . . . . . . . . . . . 4		3.3. RESTCONF RPCs and HTTP Status Codes . . . . . . . . . . . 4
	3.4. Call Flow for HTTP2 . . . . . . . . . . . . . . . . . . . 6		3.4. Call Flow for Server-Sent Events (SSE) . . . . . . . . . 6
	3.5. Call flow for HTTP1.1 . . . . . . . . . . . . . . . . . . 8		4. QoS Treatment . . . . . . . . . . . . . . . . . . . . . . . . 8
	4. QoS Treatment . . . . . . . . . . . . . . . . . . . . . . . . 10		5. Mandatory JSON and datastore support . . . . . . . . . . . . 8
	5. Mandatory JSON and datastore support . . . . . . . . . . . . 10		6. Notification Messages . . . . . . . . . . . . . . . . . . . . 8
	6. Notification Messages . . . . . . . . . . . . . . . . . . . . 10		7. YANG Tree . . . . . . . . . . . . . . . . . . . . . . . . . . 8
	7. YANG Tree . . . . . . . . . . . . . . . . . . . . . . . . . . 10		8. YANG module . . . . . . . . . . . . . . . . . . . . . . . . . 9
	8. YANG module . . . . . . . . . . . . . . . . . . . . . . . . . 10		9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
	9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13		10. Security Considerations . . . . . . . . . . . . . . . . . . . 11
	10. Security Considerations . . . . . . . . . . . . . . . . . . . 13		11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 12
	11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 13		12. References . . . . . . . . . . . . . . . . . . . . . . . . . 12
	12. References . . . . . . . . . . . . . . . . . . . . . . . . . 14		12.1. Normative References . . . . . . . . . . . . . . . . . . 12
	12.1. Normative References . . . . . . . . . . . . . . . . . . 14		12.2. Informative References . . . . . . . . . . . . . . . . . 13
	12.2. Informative References . . . . . . . . . . . . . . . . . 15		Appendix A. Examples . . . . . . . . . . . . . . . . . . . . . . 14
	Appendix A. Examples . . . . . . . . . . . . . . . . . . . . . . 16		A.1. Dynamic Subscriptions . . . . . . . . . . . . . . . . . . 14
	A.1. Dynamic Subscriptions . . . . . . . . . . . . . . . . . . 16		A.1.1. Establishing Dynamic Subscriptions . . . . . . . . . 14
	A.1.1. Establishing Dynamic Subscriptions . . . . . . . . . 16		A.1.2. Modifying Dynamic Subscriptions . . . . . . . . . . . 17
	A.1.2. Modifying Dynamic Subscriptions . . . . . . . . . . . 19		A.1.3. Deleting Dynamic Subscriptions . . . . . . . . . . . 18
	A.1.3. Deleting Dynamic Subscriptions . . . . . . . . . . . 20		A.2. Subscription State Notifications . . . . . . . . . . . . 19
	A.2. Subscription State Notifications . . . . . . . . . . . . 21		A.2.1. subscription-modified . . . . . . . . . . . . . . . . 19
	A.2.1. subscription-started and subscription-modified . . . 21
	A.2.2. subscription-completed, subscription-resumed, and		A.2.2. subscription-completed, subscription-resumed, and
	replay-complete . . . . . . . . . . . . . . . . . . . 22		replay-complete . . . . . . . . . . . . . . . . . . . 20
	A.2.3. subscription-terminated and subscription-suspended . 22		A.2.3. subscription-terminated and subscription-suspended . 20
	Appendix B. Changes between revisions . . . . . . . . . . . . . 23		A.3. Filter Example . . . . . . . . . . . . . . . . . . . . . 21
			Appendix B. Changes between revisions . . . . . . . . . . . . . 22
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 24		Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 24
	1. Introduction		1. Introduction
	Mechanisms to support event subscription and push are defined in		Mechanisms to support event subscription and push are defined in
	[I-D.draft-ietf-netconf-subscribed-notifications]. Enhancements to		[I-D.draft-ietf-netconf-subscribed-notifications]. Enhancements to
	[I-D.draft-ietf-netconf-subscribed-notifications] which enable YANG		[I-D.draft-ietf-netconf-subscribed-notifications] which enable YANG
	datastore subscription and push are defined in		datastore subscription and push are defined in
	[I-D.ietf-netconf-yang-push]. This document provides a transport		[I-D.ietf-netconf-yang-push]. This document provides a transport
	specification for dynamic subscriptions over RESTCONF [RFC8040].		specification for dynamic subscriptions over RESTCONF [RFC8040].
	Driving these requirements is [RFC7923].		Driving these requirements is [RFC7923].
	The streaming of notifications encapsulating the resulting		The streaming of notifications encapsulating the resulting
	information push can be done with either HTTP1.1 [RFC7231] or HTTP2		information push is done via the mechanism described in section 6.3
	[RFC7540].		of [RFC8040].
	2. Terminology		2. Terminology
	The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",		The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
	"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this		"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
	document are to be interpreted as described in RFC 2119 [RFC2119].		document are to be interpreted as described in RFC 2119 [RFC2119].
	The following terms use the definitions from		The following terms use the definitions from
	[I-D.draft-ietf-netconf-subscribed-notifications]: dynamic		[I-D.draft-ietf-netconf-subscribed-notifications]: dynamic
	subscription, event stream, notification message, publisher,		subscription, event stream, notification message, publisher,
	skipping to change at page 3, line 30 ¶		skipping to change at page 3, line 30 ¶
	Other terms reused include datastore, which is defined in [RFC8342],		Other terms reused include datastore, which is defined in [RFC8342],
	and HTTP2 stream which maps to the definition of "stream" within		and HTTP2 stream which maps to the definition of "stream" within
	[RFC7540], Section 2.		[RFC7540], Section 2.
	[ note to the RFC Editor - please replace XXXX within this document		[ note to the RFC Editor - please replace XXXX within this document
	with the number of this document ]		with the number of this document ]
	3. Dynamic Subscriptions		3. Dynamic Subscriptions
	This section provides specifics on how to establish and maintain		This section provides specifics on how to establish and maintain
	dynamic subscriptions over HTTP 1.1 and HTTP2 via signaling messages		dynamic subscriptions over RESTCONF [RFC8040]. Subscribing to event
	transported over RESTCONF [RFC8040]. Subscribing to event streams is		streams is accomplished in this way via a RESTCONF POST into RPCs
	accomplished in this way via a RESTCONF POST into RPCs defined within		defined within [I-D.draft-ietf-netconf-subscribed-notifications]
	[I-D.draft-ietf-netconf-subscribed-notifications] Section 2.4. YANG		Section 2.4. YANG datastore subscription is accomplished via
	datastore subscription is accomplished via augmentations to		augmentations to [I-D.draft-ietf-netconf-subscribed-notifications] as
	[I-D.draft-ietf-netconf-subscribed-notifications] as described within		described within [I-D.ietf-netconf-yang-push] Section 4.4.
	[I-D.ietf-netconf-yang-push] Section 4.4.
	Common across all HTTP based dynamic subscriptions is that a POST		As described in [RFC8040] Section 6.3, a GET needs to be made against
	needs to be made against a specific URI on the Publisher.		a specific URI on the publisher. Subscribers cannot pre-determine
	Subscribers cannot pre-determine the URI against which a subscription		the URI against which a subscription might exist on a publisher, as
	might exist on a publisher, as the URI will only exist after the		the URI will only exist after the "establish-subscription" RPC has
	"establish-subscription" has been accepted. The subscription URI		been accepted. The subscription URI will be determined and sent as
	will be determined and sent as part of the response to the		part of the response to the "establish-subscription" RPC, and a
	"establish-subscription", and a subsequent POST to this URI will be		subsequent GET to this URI will be done in order to start the flow of
	done in order to start the flow of notification messages back to the		notification messages back to the subscriber. A subscription does
	subscriber. A subscription does not move to the active state as per		not move to the active state as per Section 2.4.1. of
	Section 2.4.1. of [I-D.draft-ietf-netconf-subscribed-notifications]		[I-D.draft-ietf-netconf-subscribed-notifications] until the GET is
	until the POST is received.		received. The POST for the "establish-subscription" RPC replaces the
			GET request for the "location" leaf which is used in [RFC8040] to
			obtain the URI.
	3.1. Transport Connectivity		3.1. Transport Connectivity
	For a dynamic subscription, where an HTTP client session doesn't		For a dynamic subscription, where an HTTP client session doesn't
	already exist, a new client session is initiated from the subscriber.		already exist, a new client session is initiated from the subscriber.
	If the subscriber is unsure if HTTP2 is supported by the publisher,
	HTTP1.1 will be used for initial messages, and these messages will
	include an HTTP version upgrade request as per [RFC7230],
	Section 6.7. If a publisher response indicates that HTTP2 is
	supported, HTTP2 will be used between subscriber and publisher for
	future HTTP interactions as per [RFC7540].
	A subscriber SHOULD establish the HTTP session over TLS [RFC5246] in		As stated in Section 2.1 of [RFC8040], a subscriber MUST establish
	order to secure the content in transit.		the HTTP session over TLS [RFC5246] in order to secure the content in
			transit.
	Without the involvement of additional protocols, neither HTTP1.1 nor		Without the involvement of additional protocols, HTTP sessions by
	HTTP2 sessions by themselves allow for a quick recognition of when		themselves do not allow for a quick recognition of when the
	the communication path has been lost with the publisher. Where quick		communication path has been lost with the publisher. Where quick
	recognition of the loss of a publisher is required, a subscriber		recognition of the loss of a publisher is required, a subscriber
	SHOULD connect over TLS [RFC5246], and use a TLS heartbeat [RFC6520]		SHOULD use a TLS heartbeat [RFC6520], just from receiver to
	to track HTTP session continuity. In the case where a TLS heartbeat		publisher, to track HTTP session continuity. Loss of the heartbeat
	is included, it should be sent just from receiver to publisher. Loss		MUST result in any subscription related TCP sessions between those
	of the heartbeat MUST result in any subscription related TCP sessions		endpoints being torn down. A subscriber can then attempt to re-
	between those endpoints being torn down. A subscriber can then		establish.
	attempt to re-establish.
	3.2. Discovery		3.2. Discovery
	Subscribers can learn what event streams a RESTCONF server supports		Subscribers can learn what event streams a RESTCONF server supports
	by querying the "streams" container of ietf-subscribed-		by querying the "streams" container of ietf-subscribed-
	notification.yang. Subscribers can learn what datastores a RESTCONF		notification.yang in
	server supports by following [I-D.draft-ietf-netconf-nmda-restconf].		[I-D.draft-ietf-netconf-subscribed-notifications]. Support for the
			"streams" container of ietf-restconf-monitoring.yang in [RFC6520] is
			not required.
			Subscribers can learn what datastores a RESTCONF server supports by
			following [I-D.draft-ietf-netconf-nmda-restconf].
	3.3. RESTCONF RPCs and HTTP Status Codes		3.3. RESTCONF RPCs and HTTP Status Codes
	Specific HTTP responses codes as defined in [RFC7231] section 6 will		Specific HTTP responses codes as defined in [RFC7231] section 6 will
	indicate the result of RESTCONF RPC requests with publisher. An HTTP		indicate the result of RESTCONF RPC requests with publisher. An HTTP
	status code of 200 is the proper response to any successful RPC		status code of 200 is the proper response to any successful RPC
	defined within [I-D.draft-ietf-netconf-subscribed-notifications] or		defined within [I-D.draft-ietf-netconf-subscribed-notifications] or
	[I-D.ietf-netconf-yang-push].		[I-D.ietf-netconf-yang-push].
	If a publisher fails to serve the RPC request for one of the reasons		If a publisher fails to serve the RPC request for one of the reasons
	skipping to change at page 6, line 31 ¶		skipping to change at page 6, line 31 ¶
	"kill-subscription", or a "resynch-subscription" request, no		"kill-subscription", or a "resynch-subscription" request, no
	"error-info" needs to be included, as the "subscription-id" is		"error-info" needs to be included, as the "subscription-id" is
	the only RPC input parameter and no hints regarding this RPC input		the only RPC input parameter and no hints regarding this RPC input
	parameters need to be provided.		parameters need to be provided.
	Note that "error-path" does not need to be included with the "rpc-		Note that "error-path" does not need to be included with the "rpc-
	error" element, as subscription errors are generally not associated		error" element, as subscription errors are generally not associated
	with nodes in the datastore but with the choice of RPC input		with nodes in the datastore but with the choice of RPC input
	parameters.		parameters.
	3.4. Call Flow for HTTP2		3.4. Call Flow for Server-Sent Events (SSE)
			The call flow is defined in Figure 1. The logical connections
			denoted by (a) and (b) can be a TCP connection or an HTTP2 stream.
	Requests to [I-D.draft-ietf-netconf-subscribed-notifications] or		Requests to [I-D.draft-ietf-netconf-subscribed-notifications] or
	[I-D.ietf-netconf-yang-push] augmented RPCs are sent on one or more		[I-D.ietf-netconf-yang-push] augmented RPCs are sent on a connection
	HTTP2 streams indicated by (a) in Figure 1. A successful "establish-		indicated by (a). A successful "establish-subscription" will result
	subscription" will result in an RPC response returned with both a		in an RPC response returned with both a subscription identifier which
	subscription identifier which uniquely identifies a subscription, as		uniquely identifies a subscription, as well as a URI which uniquely
	well as a URI which uniquely identifies the location of subscription		identifies the location of subscription on the publisher (b). This
	on the publisher. This URI is defined via the "uri" leaf the Data		URI is defined via the "uri" leaf the Data Model in Section 8.
	Model in Section 8.
	An HTTP POST is then sent on a logically separate HTTP2 stream (b) to
	the URI on the publisher. This initiates to initiate the flow of
	notification messages which are sent in HTTP Data frames as a
	response to the POST. In the case below, a newly established
	subscription has its associated notification messages pushed over
	HTTP2 stream (7). These notification messages are placed into a
	HTTP2 Data frame (see [RFC7540] Section 6.1).
	+------------+ +------------+
	| Subscriber | | Publisher |
	|HTTP2 Stream| |HTTP2 Stream|
	| (a) (b) | | (a) (b) |
	+------------+ +------------+
	| RESTCONF POST (RPC:establish-subscription) |
	|--------------------------------------------->|
	| HTTP 200 OK (ID,URI)|
	|<---------------------------------------------|
	| (7)HTTP POST (URI) (7)
	| |--------------------------------------------->|
	| | HTTP 200 OK|
	| |<---------------------------------------------|
	| | HTTP Data (notif-message)|
	| |<---------------------------------------------|
	| RESTCONF POST (RPC:modify-subscription) | |
	|--------------------------------------------->| |
	| | HTTP 200 OK| |
	|<---------------------------------------------| |
	| | HTTP Data (subscription-modified)|
	| |<------------------------------------------(c)|
	| | HTTP Data (notif-message)|
	| |<---------------------------------------------|
	| RESTCONF POST (RPC:delete-subscription) | |
	|--------------------------------------------->| |
	| | HTTP 200 OK| |
	|<---------------------------------------------| |
	| | HTTP Headers (end of stream)|
	| (/7)<-----------------------------------------(/7)
	|
	Figure 1: Dynamic with HTTP2
	Additional requirements for dynamic subscriptions over HTTP2 include:
	o A unique HTTP2 stream MAY be used for each subscription.
	o A single HTTP2 stream MUST NOT be used for subscriptions with
	different DSCP values.
	o All subscription state notifications from a publisher MUST be
	returned in a separate HTTP Data frame within the HTTP2 stream
	used by the subscription to which the state change refers.
	o In addition to an RPC response for a "modify-subscription" RPC
	traveling over (a), a "subscription-modified" state change
	notification must be sent within HTTP2 stream (b). This allows
	the receiver to know exactly when the new terms of the
	subscription have been applied to the notification messages. See
	arrow (c).
	o Additional RPCs for a particular subscription MUST NOT use the
	HTTP2 stream currently providing notification messages
	subscriptions.
	o An HTTP end of stream message MUST not be sent until all
	subscriptions using that HTTP2 stream have completed.
	3.5. Call flow for HTTP1.1
	The call flow is defined in Figure 2. Requests to
	[I-D.draft-ietf-netconf-subscribed-notifications] or
	[I-D.ietf-netconf-yang-push] augmented RPCs are sent on a TCP
	connection indicated by (a). A successful "establish-subscription"
	will result in an RPC response returned with both a subscription
	identifier which uniquely identifies a subscription, as well as a URI
	which uniquely identifies the location of subscription on the
	publisher (b). This URI is defined via the "uri" leaf the Data Model
	in Section 8.
	An HTTP POST is then sent on a logically separate TCP connection (b)		An HTTP GET is then sent on a separate logical connection (b) to the
	to the URI on the publisher. This initiates to initiate the flow of		URI on the publisher. This initiates the publisher to initiate the
	notification messages which are sent in SSE [W3C-20150203] as a		flow of notification messages which are sent in SSE [W3C-20150203] as
	response to the POST.		a response to the GET.
	+--------------+ +--------------+		+--------------+ +--------------+
	| Subscriber | | Publisher |		| Subscriber | | Publisher |
	|TCP connection| |TCP connection|		| | | |
			| Logical | | Logical |
			| Connection | | Connection |
	| (a) (b) | | (a) (b) |		| (a) (b) | | (a) (b) |
	+--------------+ +--------------+		+--------------+ +--------------+
	| RESTCONF POST (RPC:establish-subscription) |		| RESTCONF POST (RPC:establish-subscription) |
	|--------------------------------------------->|		|--------------------------------------------->|
	| HTTP 200 OK (ID,URI)|		| HTTP 200 OK (ID,URI)|
	|<---------------------------------------------|		|<---------------------------------------------|
	| |HTTP GET (URI) |		| |HTTP GET (URI) |
	| |--------------------------------------------->|		| |--------------------------------------------->|
	| | HTTP 200 OK|		| | HTTP 200 OK|
	| |<---------------------------------------------|		| |<---------------------------------------------|
	skipping to change at page 9, line 35 ¶		skipping to change at page 7, line 37 ¶
	| |<------------------------------------------(c)|		| |<------------------------------------------(c)|
	| | SSE (notif-message)|		| | SSE (notif-message)|
	| |<---------------------------------------------|		| |<---------------------------------------------|
	| RESTCONF POST (RPC:delete-subscription) | |		| RESTCONF POST (RPC:delete-subscription) | |
	|--------------------------------------------->| |		|--------------------------------------------->| |
	| | HTTP 200 OK| |		| | HTTP 200 OK| |
	|<---------------------------------------------| |		|<---------------------------------------------| |
	| | |		| | |
	| |		| |
	Figure 2: Dynamic with HTTP1.1		Figure 1: Dynamic with server-sent events
	Additional requirements for dynamic subscriptions over HTTP1.1		Additional requirements for dynamic subscriptions over SSE include:
	include:
	o All subscription state notifications from a publisher MUST be		o All subscription state notifications from a publisher MUST be
	returned in a separate SSE message used by the subscription to		returned in a separate SSE message used by the subscription to
	which the state change refers.		which the state change refers.
	o Subscription RPCs MUST NOT use the TCP connection currently		o Subscription RPCs MUST NOT use the connection currently providing
	providing notification messages for that subscription.		notification messages for that subscription.
	o In addition to an RPC response for a "modify-subscription" RPC		o In addition to an RPC response for a "modify-subscription" RPC
	traveling over (a), a "subscription-modified" state change		traveling over (a), a "subscription-modified" state change
	notification must be sent within stream (b). This allows the		notification must be sent within (b). This allows the receiver to
	receiver to know exactly when the new terms of the subscription		know exactly when the new terms of the subscription have been
	have been applied to the notification messages. See arrow (c).		applied to the notification messages. See arrow (c).
	Open question, should we just eliminate this possibility of HTTP1.1		A publisher MUST terminate a subscription in the following cases:
	for subscriptions? It would make the design simpler.
			o Receipt of a "delete-subscription" or a "kill-subscription" RPC
			for that subscription.
			o Loss of TLS heartbeat
			A publisher MAY terminate a subscription at any time as stated in
			[I-D.draft-ietf-netconf-subscribed-notifications] Section 1.3
	4. QoS Treatment		4. QoS Treatment
	To meet subscription quality of service promises, the publisher MUST		To meet subscription quality of service promises, the publisher MUST
	take any existing subscription "dscp" and apply it to the DSCP		take any existing subscription "dscp" and apply it to the DSCP
	marking in the IP header.		marking in the IP header.
	In addition, where HTTP2 transport is available to a notification		In addition, where HTTP2 transport is available to a notification
	message queued for transport to a receiver, the publisher MUST:		message queued for transport to a receiver, the publisher MUST:
	skipping to change at page 10, line 51 ¶		skipping to change at page 9, line 10 ¶
	The YANG model defined in Section 8 has one leaf augmented into four		The YANG model defined in Section 8 has one leaf augmented into four
	places of [I-D.draft-ietf-netconf-subscribed-notifications], plus two		places of [I-D.draft-ietf-netconf-subscribed-notifications], plus two
	identities. As the resulting full tree is large, it will only be		identities. As the resulting full tree is large, it will only be
	inserted at later stages of this document.		inserted at later stages of this document.
	8. YANG module		8. YANG module
	This module references		This module references
	[I-D.draft-ietf-netconf-subscribed-notifications].		[I-D.draft-ietf-netconf-subscribed-notifications].
	<CODE BEGINS> file "ietf-restconf-subscribed-notifications@2018-09-12.yang"		<CODE BEGINS> file "ietf-restconf-subscribed-notifications@2018-10-03.yang"
	module ietf-restconf-subscribed-notifications {		module ietf-restconf-subscribed-notifications {
	yang-version 1.1;		yang-version 1.1;
	namespace		namespace
	"urn:ietf:params:xml:ns:yang:ietf-restconf-subscribed-notifications";		"urn:ietf:params:xml:ns:yang:ietf-restconf-subscribed-notifications";
	prefix rsn;		prefix rsn;
	import ietf-subscribed-notifications {		import ietf-subscribed-notifications {
	prefix sn;		prefix sn;
	}		}
	skipping to change at page 11, line 47 ¶		skipping to change at page 10, line 6 ¶
	Redistribution and use in source and binary forms, with or without		Redistribution and use in source and binary forms, with or without
	modification, is permitted pursuant to, and subject to the license		modification, is permitted pursuant to, and subject to the license
	terms contained in, the Simplified BSD License set forth in Section		terms contained in, the Simplified BSD License set forth in Section
	4.c of the IETF Trust's Legal Provisions Relating to IETF Documents		4.c of the IETF Trust's Legal Provisions Relating to IETF Documents
	(https://trustee.ietf.org/license-info).		(https://trustee.ietf.org/license-info).
	This version of this YANG module is part of RFC XXXX; see the RFC		This version of this YANG module is part of RFC XXXX; see the RFC
	itself for full legal notices.";		itself for full legal notices.";
	revision 2018-09-12 {		revision 2018-10-03 {
	description		description
	"Initial version";		"Initial version";
	reference		reference
	"RFC XXXX: RESTCONF Transport for Event Notifications";		"RFC XXXX: RESTCONF Transport for Event Notifications";
			}
			identity restconf {
			base sn:transport;
			description
			"RESTCONF is used as transport for notification messages and state
			change notifications.";
	}		}
	grouping uri {		grouping uri {
	description		description
	"Provides a reusable description of a URI.";		"Provides a reusable description of a URI.";
	leaf uri {		leaf uri {
	type inet:uri;		type inet:uri;
	config false;		config false;
	description		description
	"Location of a subscription specific URI on the publisher.";		"Location of a subscription specific URI on the publisher.";
	}		}
	}		}
	augment "/sn:establish-subscription/sn:output" {		augment "/sn:establish-subscription/sn:output" {
	description		description
	"This augmentation allows HTTP specific parameters for a		"This augmentation allows RESTCONF specific parameters for a
	response to a publisher's subscription request.";		response to a publisher's subscription request.";
	uses uri;		uses uri;
	}		}
	augment "/sn:subscriptions/sn:subscription" {		augment "/sn:subscriptions/sn:subscription" {
	description		description
	"This augmentation allows HTTP specific parameters to be		"This augmentation allows RESTCONF specific parameters to be
	exposed for a subscription.";		exposed for a subscription.";
	uses uri;		uses uri;
	}		}
	augment "/sn:subscription-started" {
	description
	"This augmentation allows HTTP specific parameters to be included
	part of the notification that a subscription has started.";
	uses uri;
	}
	augment "/sn:subscription-modified" {		augment "/sn:subscription-modified" {
	description		description
	"This augmentation allows HTTP specific parameters to be included		"This augmentation allows RESTCONF specific parameters to be included
	part of the notification that a subscription has been modified.";		part of the notification that a subscription has been modified.";
	uses uri;		uses uri;
	}		}
	}		}
	<CODE ENDS>		<CODE ENDS>
	9. IANA Considerations		9. IANA Considerations
	This document registers the following namespace URI in the "IETF XML		This document registers the following namespace URI in the "IETF XML
	Registry" [RFC3688]:		Registry" [RFC3688]:
	URI: urn:ietf:params:xml:ns:yang:ietf-restconf-subscribed-		URI: urn:ietf:params:xml:ns:yang:ietf-restconf-subscribed-
	notifications		notifications
	Registrant Contact: The IESG.		Registrant Contact: The IESG.
	XML: N/A; the requested URI is an XML namespace.		XML: N/A; the requested URI is an XML namespace.
	skipping to change at page 13, line 51 ¶		skipping to change at page 12, line 10 ¶
	o "uri": leaf will show where subscribed resources might be located		o "uri": leaf will show where subscribed resources might be located
	on a publisher. Access control must be set so that only someone		on a publisher. Access control must be set so that only someone
	with proper access permissions, and perhaps even HTTP session has		with proper access permissions, and perhaps even HTTP session has
	the ability to access this resource.		the ability to access this resource.
	11. Acknowledgments		11. Acknowledgments
	We wish to acknowledge the helpful contributions, comments, and		We wish to acknowledge the helpful contributions, comments, and
	suggestions that were received from: Ambika Prasad Tripathy, Alberto		suggestions that were received from: Ambika Prasad Tripathy, Alberto
	Gonzalez Prieto, Susan Hares, Tim Jenkins, Balazs Lengyel, Kent		Gonzalez Prieto, Susan Hares, Tim Jenkins, Balazs Lengyel, Kent
	Watsen, Michael Scharf, and Guangying Zheng.		Watsen, Michael Scharf, Guangying Zheng and Martin Bjorklund.
	12. References		12. References
	12.1. Normative References		12.1. Normative References
	[I-D.draft-ietf-netconf-subscribed-notifications]		[I-D.draft-ietf-netconf-subscribed-notifications]
	Voit, E., Clemm, A., Gonzalez Prieto, A., Tripathy, A.,		Voit, E., Clemm, A., Gonzalez Prieto, A., Tripathy, A.,
	and E. Nilsen-Nygaard, "Custom Subscription to Event		and E. Nilsen-Nygaard, "Custom Subscription to Event
	Streams", draft-ietf-netconf-subscribed-notifications-13		Streams", draft-ietf-netconf-subscribed-notifications-13
	(work in progress), April 2018.		(work in progress), April 2018.
	skipping to change at page 16, line 15 ¶		skipping to change at page 14, line 22 ¶
	[RFC7231] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer		[RFC7231] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
	Protocol (HTTP/1.1): Semantics and Content", RFC 7231,		Protocol (HTTP/1.1): Semantics and Content", RFC 7231,
	DOI 10.17487/RFC7231, June 2014,		DOI 10.17487/RFC7231, June 2014,
	<https://www.rfc-editor.org/info/rfc7231>.		<https://www.rfc-editor.org/info/rfc7231>.
	[RFC7923] Voit, E., Clemm, A., and A. Gonzalez Prieto, "Requirements		[RFC7923] Voit, E., Clemm, A., and A. Gonzalez Prieto, "Requirements
	for Subscription to YANG Datastores", RFC 7923,		for Subscription to YANG Datastores", RFC 7923,
	DOI 10.17487/RFC7923, June 2016,		DOI 10.17487/RFC7923, June 2016,
	<https://www.rfc-editor.org/info/rfc7923>.		<https://www.rfc-editor.org/info/rfc7923>.
			[RFC8347] Liu, X., Ed., Kyparlis, A., Parikh, R., Lindem, A., and M.
			Zhang, "A YANG Data Model for the Virtual Router
			Redundancy Protocol (VRRP)", RFC 8347,
			DOI 10.17487/RFC8347, March 2018,
			<https://www.rfc-editor.org/info/rfc8347>.
			[XPATH] Clark, J. and S. DeRose, "XML Path Language (XPath)
			Version 1.0", November 1999,
			<http://www.w3.org/TR/1999/REC-xpath-19991116>.
	Appendix A. Examples		Appendix A. Examples
	This section is non-normative. To allow easy comparison, this		This section is non-normative. To allow easy comparison, this
	section mirrors the functional examples shown with NETCONF over XML		section mirrors the functional examples shown with NETCONF over XML
	within [I-D.draft-ietf-netconf-netconf-event-notifications]. In		within [I-D.draft-ietf-netconf-netconf-event-notifications]. In
	addition, HTTP2 vs HTTP1.1 headers are not shown as the contents of		addition, HTTP2 vs HTTP1.1 headers are not shown as the contents of
	the JSON encoded objects are identical within.		the JSON encoded objects are identical within.
	A.1. Dynamic Subscriptions		A.1. Dynamic Subscriptions
	skipping to change at page 17, line 13 ¶		skipping to change at page 15, line 13 ¶
	of 23.		of 23.
	+------------+ +-----------+		+------------+ +-----------+
	| Subscriber | | Publisher |		| Subscriber | | Publisher |
	+------------+ +-----------+		+------------+ +-----------+
	| |		| |
	|establish-subscription |		|establish-subscription |
	|------------------------------>| (a)		|------------------------------>| (a)
	| HTTP 200 OK, id#22, URI#1 |		| HTTP 200 OK, id#22, URI#1 |
	|<------------------------------| (b)		|<------------------------------| (b)
	|POST (URI#1) |		|GET (URI#1) |
	|------------------------------>| (c)		|------------------------------>| (c)
	| HTTP 200 OK,notif-mesg (id#22)|		| HTTP 200 OK,notif-mesg (id#22)|
	|<------------------------------|		|<------------------------------|
	| |		| |
	| |		| |
	|establish-subscription |		|establish-subscription |
	|------------------------------>|		|------------------------------>|
	| HTTP 200 OK, id#23, URI#2|		| HTTP 200 OK, id#23, URI#2|
	|<------------------------------|		|<------------------------------|
	|POST (URI#2) |		|GET (URI#2) |
	|------------------------------>|		|------------------------------>|
	| |		| |
	| |		| |
	| notif-mesg (id#22)|		| notif-mesg (id#22)|
	|<------------------------------|		|<------------------------------|
	| HTTP 200 OK,notif-mesg (id#23)|		| HTTP 200 OK,notif-mesg (id#23)|
	|<------------------------------|		|<------------------------------|
	| |		| |
	Figure 3: Multiple subscriptions over RESTCONF/HTTP		Figure 2: Multiple subscriptions over RESTCONF/HTTP
	To provide examples of the information being transported, example		To provide examples of the information being transported, example
	messages for interactions in Figure 3 are detailed below:		messages for interactions in Figure 2 are detailed below:
	POST /restconf/operations/subscriptions:establish-subscription		POST /restconf/operations/subscriptions:establish-subscription
	{		{
	"ietf-subscribed-notifications:input": {		"ietf-subscribed-notifications:input": {
	"stream": "NETCONF",		"stream": "NETCONF",
	"stream-xpath-filter": "/ex:foo/",		"stream-xpath-filter": "/ds:foo/",
	"dscp": "10"		"dscp": "10"
	}		}
	}		}
	Figure 4: establish-subscription request (a)		Figure 3: establish-subscription request (a)
	As publisher was able to fully satisfy the request, the publisher		As publisher was able to fully satisfy the request, the publisher
	sends the subscription identifier of the accepted subscription, and		sends the subscription identifier of the accepted subscription, and
	the URI:		the URI:
	HTTP status code - 200		HTTP status code - 200
	{		{
	"id": "22",		"id": "22",
	"uri": "/subscriptions/22"		"uri": "/subscriptions/22"
	}		}
	Figure 5: establish-subscription success (b)		Figure 4: establish-subscription success (b)
	Upon receipt of the successful response, the subscriber POSTs to the		Upon receipt of the successful response, the subscriber does a GET
	provided URI to start the flow of notification messages. When the		the provided URI to start the flow of notification messages. When
	publisher receives this, the subscription is moved to the active		the publisher receives this, the subscription is moved to the active
	state (c).		state (c).
	POST /restconf/operations/subscriptions/22		GET /restconf/operations/subscriptions/22
	Figure 6: establish-subscription subsequent POST		Figure 5: establish-subscription subsequent POST
	While not shown in Figure 3, if the publisher had not been able to		While not shown in Figure 2, if the publisher had not been able to
	fully satisfy the request, or subscriber has no authorization to		fully satisfy the request, or subscriber has no authorization to
	establish the subscription, the publisher would have sent an RPC		establish the subscription, the publisher would have sent an RPC
	error response. For instance, if the "dscp" value of 10 asserted by		error response. For instance, if the "dscp" value of 10 asserted by
	the subscriber in Figure 4 proved unacceptable, the publisher may		the subscriber in Figure 3 proved unacceptable, the publisher may
	have returned:		have returned:
	HTTP status code - 406		HTTP status code - 406
	{ "ietf-restconf:errors" : {		{ "ietf-restconf:errors" : {
	"error" : [		"error" : [
	{		{
	"error-type": "application",		"error-type": "application",
	"error-tag": "operation-failed",		"error-tag": "operation-failed",
	"error-severity": "error",		"error-severity": "error",
	"error-app-tag":		"error-app-tag":
	"ietf-subscribed-notifications:dscp-unavailable"		"ietf-subscribed-notifications:dscp-unavailable"
	}		}
	]		]
	}		}
	}		}
	Figure 7: an unsuccessful establish subscription		Figure 6: an unsuccessful establish subscription
	The subscriber can use this information in future attempts to		The subscriber can use this information in future attempts to
	establish a subscription.		establish a subscription.
	A.1.2. Modifying Dynamic Subscriptions		A.1.2. Modifying Dynamic Subscriptions
	An existing subscription may be modified. The following exchange		An existing subscription may be modified. The following exchange
	shows a negotiation of such a modification via several exchanges		shows a negotiation of such a modification via several exchanges
	between a subscriber and a publisher. This negotiation consists of a		between a subscriber and a publisher. This negotiation consists of a
	failed RPC modification request/response, followed by a successful		failed RPC modification request/response, followed by a successful
	skipping to change at page 19, line 34 ¶		skipping to change at page 17, line 34 ¶
	| |		| |
	|modify-subscription (id#23) |		|modify-subscription (id#23) |
	|----------------------------->|		|----------------------------->|
	| HTTP 200 OK |		| HTTP 200 OK |
	|<-----------------------------|		|<-----------------------------|
	| |		| |
	| notif-mesg (id#23)|		| notif-mesg (id#23)|
	|<-----------------------------|		|<-----------------------------|
	| |		| |
	Figure 8: Interaction model for successful subscription modification		Figure 7: Interaction model for successful subscription modification
	If the subscription being modified in Figure 8 is a datastore		If the subscription being modified in Figure 7 is a datastore
	subscription as per [I-D.ietf-netconf-yang-push], the modification		subscription as per [I-D.ietf-netconf-yang-push], the modification
	request made in (d) may look like that shown in Figure 9. As can be		request made in (d) may look like that shown in Figure 8. As can be
	seen, the modifications being attempted are the application of a new		seen, the modifications being attempted are the application of a new
	xpath filter as well as the setting of a new periodic time interval.		xpath filter as well as the setting of a new periodic time interval.
	POST /restconf/operations/subscriptions:modify-subscription		POST /restconf/operations/subscriptions:modify-subscription
	{		{
	"ietf-subscribed-notifications:input": {		"ietf-subscribed-notifications:input": {
	"id": "23",		"id": "23",
	"ietf-yang-push:datastore-xpath-filter":		"ietf-yang-push:datastore-xpath-filter": "/ds:foo/ds:bar",
	"/interfaces-state/interface/oper-status"		"ietf-yang-push:periodic": {
	"ietf-yang-push:periodic": {
	"ietf-yang-push:period": "500"		"ietf-yang-push:period": "500"
	}		}
	}		}
	}		}
	Figure 9: Subscription modification request (c)		Figure 8: Subscription modification request (c)
	If the publisher can satisfy both changes, the publisher sends a		If the publisher can satisfy both changes, the publisher sends a
	positive result for the RPC. If the publisher cannot satisfy either		positive result for the RPC. If the publisher cannot satisfy either
	of the proposed changes, the publisher sends an RPC error response		of the proposed changes, the publisher sends an RPC error response
	(e). The following is an example RPC error response for (e) which		(e). The following is an example RPC error response for (e) which
	includes a hint. This hint is an alternative time period value which		includes a hint. This hint is an alternative time period value which
	might have resulted in a successful modification:		might have resulted in a successful modification:
	HTTP status code - 406		HTTP status code - 406
	skipping to change at page 20, line 45 ¶		skipping to change at page 18, line 44 ¶
	"error-info": {		"error-info": {
	"ietf-yang-push":		"ietf-yang-push":
	"modify-subscription-datastore-error-info": {		"modify-subscription-datastore-error-info": {
	"period-hint": "3000"		"period-hint": "3000"
	}		}
	}		}
	]		]
	}		}
	}		}
	Figure 10: Modify subscription failure with Hint (e)		Figure 9: Modify subscription failure with Hint (e)
	A.1.3. Deleting Dynamic Subscriptions		A.1.3. Deleting Dynamic Subscriptions
	The following demonstrates deleting a subscription. This		The following demonstrates deleting a subscription. This
	subscription may have been to either a stream or a datastore.		subscription may have been to either a stream or a datastore.
	POST /restconf/operations/subscriptions:delete-subscription		POST /restconf/operations/subscriptions:delete-subscription
	{		{
	"delete-subscription": {		"delete-subscription": {
	"id": "22"		"id": "22"
	}		}
	}		}
	Figure 11: Delete subscription		Figure 10: Delete subscription
	If the publisher can satisfy the request, the publisher replies with		If the publisher can satisfy the request, the publisher replies with
	success to the RPC request.		success to the RPC request.
	If the publisher cannot satisfy the request, the publisher sends an		If the publisher cannot satisfy the request, the publisher sends an
	error-rpc element indicating the modification didn't work. Figure 12		error-rpc element indicating the modification didn't work. Figure 11
	shows a valid response for existing valid subscription identifier,		shows a valid response for existing valid subscription identifier,
	but that subscription identifier was created on a different transport		but that subscription identifier was created on a different transport
	session:		session:
	HTTP status code - 406		HTTP status code - 406
	{		{
	"ietf-restconf:errors" : {		"ietf-restconf:errors" : {
	"error" : [		"error" : [
	"error-type": "application",		"error-type": "application",
	"error-tag": "operation-failed",		"error-tag": "operation-failed",
	"error-severity": "error",		"error-severity": "error",
	"error-app-tag":		"error-app-tag":
	"ietf-subscribed-notifications:no-such-subscription"		"ietf-subscribed-notifications:no-such-subscription"
	]		]
	}		}
	}		}
	Figure 12: Unsuccessful delete subscription		Figure 11: Unsuccessful delete subscription
	A.2. Subscription State Notifications		A.2. Subscription State Notifications
	A publisher will send subscription state notifications according to		A publisher will send subscription state notifications according to
	the definitions within		the definitions within
	[I-D.draft-ietf-netconf-subscribed-notifications]).		[I-D.draft-ietf-netconf-subscribed-notifications]).
	A.2.1. subscription-started and subscription-modified		A.2.1. subscription-modified
	A "subscription-started" encoded in JSON would look like:		A "subscription-modified" encoded in JSON would look like:
	{		{
	"ietf-restconf:notification" : {		"ietf-restconf:notification" : {
	"eventTime": "2007-09-01T10:00:00Z",		"eventTime": "2007-09-01T10:00:00Z",
	"ietf-subscribed-notifications:subscription-started": {		"ietf-subscribed-notifications:subscription-modified": {
	"id": "39",		"id": "39",
	"transport": "HTTP2",		"transport": "RESTCONF",
	"stream-xpath-filter": "/ex:foo",		"stream-xpath-filter": "/ex:foo",
	"stream": {		"stream": {
	"ietf-netconf-subscribed-notifications" : "NETCONF"		"ietf-netconf-subscribed-notifications" : "NETCONF"
	}		}
	}		}
	}		}
	}		}
	Figure 13: subscription-started subscription state notification		Figure 12: subscription-modified subscription state notification
	The "subscription-modified" is identical to Figure 13, with just the
	word "started" being replaced by "modified".
	A.2.2. subscription-completed, subscription-resumed, and replay-		A.2.2. subscription-completed, subscription-resumed, and replay-
	complete		complete
	A "subscription-completed" would look like:		A "subscription-completed" would look like:
	{		{
	"ietf-restconf:notification" : {		"ietf-restconf:notification" : {
	"eventTime": "2007-09-01T10:00:00Z",		"eventTime": "2007-09-01T10:00:00Z",
	"ietf-subscribed-notifications:subscription-completed": {		"ietf-subscribed-notifications:subscription-completed": {
	"id": "39",		"id": "39",
	}		}
	}		}
	}		}
	Figure 14: subscription-completed notification in JSON		Figure 13: subscription-completed notification in JSON
	The "subscription-resumed" and "replay-complete" are virtually		The "subscription-resumed" and "replay-complete" are virtually
	identical, with "subscription-completed" simply being replaced by		identical, with "subscription-completed" simply being replaced by
	"subscription-resumed" and "replay-complete".		"subscription-resumed" and "replay-complete".
	A.2.3. subscription-terminated and subscription-suspended		A.2.3. subscription-terminated and subscription-suspended
	A "subscription-terminated" would look like:		A "subscription-terminated" would look like:
	{		{
	"ietf-restconf:notification" : {		"ietf-restconf:notification" : {
	"eventTime": "2007-09-01T10:00:00Z",		"eventTime": "2007-09-01T10:00:00Z",
	"ietf-subscribed-notifications:subscription-terminated": {		"ietf-subscribed-notifications:subscription-terminated": {
	"id": "39",		"id": "39",
	"error-id": "suspension-timeout"		"error-id": "suspension-timeout"
	}		}
	}		}
	}		}
	Figure 15: subscription-terminated subscription state notification		Figure 14: subscription-terminated subscription state notification
	The "subscription-suspended" is virtually identical, with		The "subscription-suspended" is virtually identical, with
	"subscription-terminated" simply being replaced by "subscription-		"subscription-terminated" simply being replaced by "subscription-
	suspended".		suspended".
			A.3. Filter Example
			This section provides an example which illustrate the method of
			filtering event record contents. The example is based on the YANG
			notification "vrrp-protocol-error-event" as defined per the ietf-
			vrrp.yang module within [RFC8347]. Event records based on this
			specification which are generated by the publisher might appear as:
			data: {
			data: "ietf-restconf:notification" : {
			data: "eventTime" : "2018-09-14T08:22:33.44Z",
			data: "ietf-vrrp:vrrp-protocol-error-event" : {
			data: "protocol-error-reason" : "checksum-error"
			data: }
			data: }
			data: }
			Figure 15: RFC 8347 (VRRP) - Example Notification
			Suppose a subscriber wanted to establish a subscription which only
			passes instances of event records where there is a "checksum-error"
			as part of a VRRP protocol event. Also assume the publisher places
			such event records into the NETCONF stream. To get a continuous
			series of matching event records, the subscriber might request the
			application of an XPath filter against the NETCONF stream. An
			"establish-subscription" RPC to meet this objective might be:
			POST /restconf/operations/subscriptions:establish-subscription
			{
			"ietf-subscribed-notifications:input": {
			"stream": "NETCONF",
			"stream-xpath-filter": "/ietf-vrrp:vrrp-protocol-error-event[protocol-error-reason='checksum-error']/",
			}
			}
			Figure 16: Establishing a subscription error reason via XPATH
			For more examples of xpath filters, see [XPATH].
			Suppose the "establish-subscription" in Figure 16 was accepted. And
			suppose later a subscriber decided they wanted to broaden this
			subscription cover to all VRRP protocol events (i.e., not just those
			with a "checksum error"). The subscriber might attempt to modify the
			subscription in a way which replaces the XPath filter with a subtree
			filter which sends all VRRP protocol events to a subscriber. Such a
			"modify-subscription" RPC might look like:
			POST /restconf/operations/subscriptions:modify-subscription
			{
			"ietf-subscribed-notifications:input": {
			"stream": "NETCONF",
			"stream-subtree-filter": "/ietf-vrrp:vrrp-protocol-error-event/",
			}
			}
			Figure 17
			For more examples of subtree filters, see [RFC6241], section 6.4.
	Appendix B. Changes between revisions		Appendix B. Changes between revisions
	(To be removed by RFC editor prior to publication)		(To be removed by RFC editor prior to publication)
			v07 - v08
			o Aligned with RESTCONF mechanism.
			o YANG model: removed augment of subscription-started, added
			restconf transport.
			o Tweaked Appendix A.1 to match draft-ietf-netconf-netconf-event-
			notifications-13.
			o Added Appendix A.3 for filter example.
	v06 - v07		v06 - v07
	o Removed configured subscriptions.		o Removed configured subscriptions.
	o Subscription identifier renamed to id.		o Subscription identifier renamed to id.
	v05 - v06		v05 - v06
	o JSON examples updated by Reshad.		o JSON examples updated by Reshad.
End of changes. 67 change blocks.
	218 lines changed or deleted		226 lines changed or added
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