< draft-ietf-netconf-restconf-notif-01.txt		draft-ietf-netconf-restconf-notif-02.txt >
	NETCONF E. Voit		NETCONF E. Voit
	Internet-Draft A. Clemm		Internet-Draft A. Gonzalez Prieto
	Intended status: Standards Track A. Gonzalez Prieto		Intended status: Standards Track A. Tripathy
	Expires: April 2, 2017 A. Tripathy		Expires: September 14, 2017 E. Nilsen-Nygaard
	E. Nilsen-Nygaard
	Cisco Systems		Cisco Systems
			A. Clemm
			Huawei
	A. Bierman		A. Bierman
	YumaWorks		YumaWorks
	September 29, 2016		March 13, 2017
	Restconf and HTTP Transport for Event Notifications		Restconf and HTTP Transport for Event Notifications
	draft-ietf-netconf-restconf-notif-01		draft-ietf-netconf-restconf-notif-02
	Abstract		Abstract
	This document defines Restconf, HTTP2, and HTTP1.1 bindings for the		This document defines Restconf, HTTP2, and HTTP1.1 bindings for the
	transport Subscription requests and corresponding push updates.		transport of Subscription requests and corresponding push updates.
	Being subscribed may be both Event Notifications and YANG Datastores.		Being subscribed may be either Event Notifications or objects or
			subtress of YANG Datastores.
	Status of This Memo		Status of This Memo
	This Internet-Draft is submitted in full conformance with the		This Internet-Draft is submitted in full conformance with the
	provisions of BCP 78 and BCP 79.		provisions of BCP 78 and BCP 79.
	Internet-Drafts are working documents of the Internet Engineering		Internet-Drafts are working documents of the Internet Engineering
	Task Force (IETF). Note that other groups may also distribute		Task Force (IETF). Note that other groups may also distribute
	working documents as Internet-Drafts. The list of current Internet-		working documents as Internet-Drafts. The list of current Internet-
	Drafts is at http://datatracker.ietf.org/drafts/current/.		Drafts is at http://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 April 2, 2017.		This Internet-Draft will expire on September 14, 2017.
	Copyright Notice		Copyright Notice
	Copyright (c) 2016 IETF Trust and the persons identified as the		Copyright (c) 2017 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
	(http://trustee.ietf.org/license-info) in effect on the date of		(http://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
	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
	the Trust Legal Provisions and are provided without warranty as		the Trust Legal Provisions and are provided without warranty as
	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. Solution . . . . . . . . . . . . . . . . . . . . . . . . . . 4		3. Solution . . . . . . . . . . . . . . . . . . . . . . . . . . 3
	3.1. Mechanisms for Subscription Establishment and Maintenance 4		3.1. Dynamic YANG Subscription with RESTCONF control . . . . . 3
	3.2. Dynamic YANG Subscription with RESTCONF control . . . . . 5		3.2. Subscription Multiplexing . . . . . . . . . . . . . . . . 6
	3.3. Subscription Multiplexing . . . . . . . . . . . . . . . . 8		4. Encoded Subscription and Event Notification Examples . . . . 7
	3.4. Encoded Subscription and Event Notification Examples . . 9		4.1. Restconf Subscription and Events over HTTP1.1 . . . . . . 7
	3.5. Stream Discovery . . . . . . . . . . . . . . . . . . . . 14		4.2. Event Notification over HTTP2 . . . . . . . . . . . . . . 12
	4. Security Considerations . . . . . . . . . . . . . . . . . . . 14		5. Security Considerations . . . . . . . . . . . . . . . . . . . 12
	5. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 15		6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 13
	6. References . . . . . . . . . . . . . . . . . . . . . . . . . 15		7. References . . . . . . . . . . . . . . . . . . . . . . . . . 13
	6.1. Normative References . . . . . . . . . . . . . . . . . . 15		7.1. Normative References . . . . . . . . . . . . . . . . . . 13
	6.2. Informative References . . . . . . . . . . . . . . . . . 16		7.2. Informative References . . . . . . . . . . . . . . . . . 14
	Appendix A. Proxy YANG Subscription when the Subscriber and		Appendix A. End-to-End Deployment Guidance . . . . . . . . . . . 14
	Receiver are different . . . . . . . . . . . . . . . 17		A.1. Call Home . . . . . . . . . . . . . . . . . . . . . . . . 14
	Appendix B. End-to-End Deployment Guidance . . . . . . . . . . . 17		A.2. TLS Heartbeat . . . . . . . . . . . . . . . . . . . . . . 15
	B.1. Call Home . . . . . . . . . . . . . . . . . . . . . . . . 17		Appendix B. Issues being worked and resolved . . . . . . . . . . 15
	B.2. TLS Heartbeat . . . . . . . . . . . . . . . . . . . . . . 18		B.1. Unresolved Issues . . . . . . . . . . . . . . . . . . . . 15
	Appendix C. Issues being worked and resolved . . . . . . . . . . 18		Appendix C. Changes between revisions . . . . . . . . . . . . . 15
	C.1. Unresolved Issues . . . . . . . . . . . . . . . . . . . . 18		Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 16
	C.2. Agreement in principal . . . . . . . . . . . . . . . . . 18
	C.3. Resolved Issues . . . . . . . . . . . . . . . . . . . . . 18
	Appendix D. Changes between revisions . . . . . . . . . . . . . 19
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 19
	1. Introduction		1. Introduction
	Mechanisms to support Event subscription and push are defined in		Mechanisms to support Event subscription and push are defined in
	[rfc5277bis]. Enhancements to [rfc5277bis] which enable YANG		[sn]. Enhancements to [sn] which enable YANG Datastore subscription
	Datastore subscription and push are defined in [yang-push]. This		and push are defined in [yang-push]. This document provides a
	document provides a transport specification for these protocols over		transport specification for these protocols over Restconf and HTTP.
	Restconf and HTTP. Driving these requirements is [RFC7923].		Driving these requirements is [RFC7923].
	The streaming of Subscription Event Notifications has synergies with		The streaming of Subscription Event Notifications has synergies with
	HTTP2 streams. Benefits which can be realized when transporting		HTTP2 streams. Benefits which can be realized when transporting
	events directly HTTP2 [RFC7540] include:		events directly HTTP2 [RFC7540] include:
	o Elimination of head-of-line blocking		o Elimination of head-of-line blocking
	o Weighting and proportional dequeuing of Events from different		o Weighting and proportional dequeuing of Events from different
	subscriptions		subscriptions
	o Explicit precedence in subscriptions so that events from one		o Explicit precedence in subscriptions so that events from one
	subscription must be sent before another dequeues		subscription must be sent before another dequeues
	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].
	Configured Subscription: a Subscription installed via a configuration		The following terms use the defintions from [sn]: Configured
	interface which persists across reboots.		Subscription, Dynamic Subscription, Event Notification, Publisher,
			Receiver, Subscriber, Subscription.
	Dynamic Subscription: a Subscription negotiated between Subscriber
	and Publisher via create, establish, modify, and delete RPC signaling
	messages.
	Event: an occurrence of something that may be of interest. (e.g., a
	configuration change, a fault, a change in status, crossing a
	threshold, status of a flow, or an external input to the system.)
	Event Notification: a set of information intended for a Receiver
	indicating that one or more Event(s) have occurred. Details of the
	Event(s) may be included within.
	Event Stream: a continuous, ordered set of Events grouped under an
	explicit criteria.
	Notification: the communication of an occurrence, perhaps triggered
	by the occurrence of an Event.
	Publisher: an entity responsible for streaming Event Notifications
	per the terms of a Subscription.
	Receiver: a target to which a Publisher pushes Event Notifications.
	For Dynamic Subscriptions, the Receiver and Subscriber will often be
	the same entity.
	Subscriber: an entity able to request and negotiate a contract for
	the receipt of Event Notifications from a Publisher
	Subscription: a contract between a Subscriber and a Publisher
	stipulating which information the Receiver wishes to have pushed from
	the Publisher without the need for further solicitation.
	3. Solution		3. Solution
	Event subscription is defined in [rfc5277bis], YANG Datastore		Event subscription is defined in [sn], YANG Datastore subscription is
	subscription is defined in [yang-push]. This section specifies		defined in [yang-push]. This section specifies transport mechanisms
	transport mechanisms applicable to both.		applicable to both.
	3.1. Mechanisms for Subscription Establishment and Maintenance
	There are three models for Subscription establishment and
	maintenance:
	1. Dynamic Subscription: Here the Subscriber and Receiver are the
	same. A Subscription ends with a subscription-terminated
	notification, or by a loss of transport connectivity.
	2. Configured Subscription: Receiver(s) are specified on Publisher
	in startup and running config. Subscription is not terminated
	except via an operations interface. (Subscriptions may be
	Suspended, with no Event Notifications sent however.)
	3. Proxy Subscription: Subscriber and Receiver are different.
	Subscription ends when a Subscription End-time is reached, or the
	Publisher process is restarted. A key difference between this
	and configured subscriptions (#2) is that configuration requests
	are made to RPCs which might evaluate run-time conditions much
	like in (#1). Typically direct configuration via (#2) will not
	go through the same sort of capacity and validation checks seen
	in (#1).
	The first two models are described in this section. The third is
	described in Appendix A. This third model will be moved into the
	body of this specification should the IETF community desire. In
	theory, all three models may be intermixed in a single deployment.
	.---------------.
	| Publisher |
	'---------------'
	^ ^ | ^
	| | | |
	.-----Restconf----' | | '-----Restconf----.
	| .-----' '-HTTP-. |
	V | V |
	.-------------. .------------. .----------. .------------.
	| Subscriber+ | | Operations | | Receiver | | Subscriber |
	| Receiver | | /Config | '----------' '------------'
	'-------------' '------------' ^ ^ ^
	^ (out of scope) : : :
	: ^ : :...Model #3....:
	Model #1 :..Model #2...: (out of scope)
	Figure 1: Subscription Models
	3.2. Dynamic YANG Subscription with RESTCONF control		3.1. Dynamic YANG Subscription with RESTCONF control
	Dynamic Subscriptions for both [rfc5277bis] and its [yang-push]		Dynamic Subscriptions for both [sn] and its [yang-push] augmentations
	augmentations are configured and managed via signaling messages		are configured and managed via signaling messages transported over
	transported over [restconf]. These interactions will be accomplished		[RFC8040]. These interactions will be accomplished via a Restconf
	via a Restconf POST into RPCs located on the Publisher. HTTP		POST into RPCs located on the Publisher. HTTP responses codes will
	responses codes will indicate the results of the interaction with the		indicate the results of the interaction with the Publisher. An HTTP
	Publisher. An HTTP status code of 200 is the proper response to a		status code of 200 is the proper response to a successful <establish-
	successful <establish-subscription> RPC call. The successful		subscription> RPC call. The successful <establish-subscription> will
	<establish-subscription> will result in a HTTP message with returned		result in a HTTP message with returned subscription URI on a
	subscription URI on a logically separate mechanism than was used for		logically separate mechanism than was used for the original Restconf
	the original Restconf POST. This mechanism would be via a parallel		POST. This mechanism is via a parallel TCP connection in the case of
	TCP connection in the case of HTTP 1.x, or in the case of HTTP2 via a		HTTP 1.x, or in the case of HTTP2 via a separate HTTP stream within
	separate HTTP stream within the HTTP connection. When a being		the HTTP connection. When a being returned by the Publisher, failure
	returned by the Publisher, failure will be indicated by error codes		will be indicated by error codes transported in payload.
	transported in payload, as well as the return of negotiation
	parameters.
	Once established, streaming Event Notifications are then delivered		Once established, the resulting stream of Event Notifications are
	via SSE for HTTP1.1 and via HTTP Data for HTTP2.		then delivered via SSE for HTTP1.1 and via HTTP Data for HTTP2.
	3.2.1. Call Flow for HTTP2		3.1.1. Call Flow for HTTP2
	Requests to [yang-push] augmented RPCs are sent on one or more HTTP2		Requests to [yang-push] augmented RPCs are sent on one or more HTTP2
	streams indicated by (a) in Figure 2. Event Notifications related to		streams indicated by (a) in Figure 2. Event Notifications related to
	a single subscription are pushed on a unique logical channel (b). In		a single subscription are pushed on a unique logical channel (b). In
	the case below, a newly established subscription has its events		the case below, a newly established subscription has its events
	pushed over HTTP2 stream (7).		pushed over HTTP2 stream (7).
	+------------+ +------------+		+------------+ +------------+
	| Subscriber | | Publisher |		| Subscriber | | Publisher |
	|HTTP2 Stream| |HTTP2 Stream|		|HTTP2 Stream| |HTTP2 Stream|
	skipping to change at page 6, line 36 ¶		skipping to change at page 4, line 36 ¶
	| | HTTP Data (event-notif)|		| | HTTP Data (event-notif)|
	| |<---------------------------------------------|		| |<---------------------------------------------|
	| Restconf POST (RPC:delete-subscription) | |		| Restconf POST (RPC:delete-subscription) | |
	|--------------------------------------------->| |		|--------------------------------------------->| |
	| | HTTP 200 OK| |		| | HTTP 200 OK| |
	|<---------------------------------------------| |		|<---------------------------------------------| |
	| | HTTP Headers (end of stream)|		| | HTTP Headers (end of stream)|
	| (/7)<-----------------------------------------(/7)		| (/7)<-----------------------------------------(/7)
	|		|
	Figure 2: Dynamic with HTTP2		Figure 1: Dynamic with HTTP2
	3.2.2. Call flow for HTTP1.1		3.1.2. Call flow for HTTP1.1
	Requests to [yang-push] RPCs are sent on the TCP connection indicated		Requests to [yang-push] RPCs are sent on the TCP connection indicated
	by (a). Event Notifications are pushed on a separate connection (b).		by (a). Event Notifications are pushed on a separate connection (b).
	This connection (b) will be used for all Event Notifications across		This connection (b) will be used for all Event Notifications across
	all subscriptions.		all subscriptions.
	+--------------+ +--------------+		+--------------+ +--------------+
	| Subscriber | | Publisher |		| Subscriber | | Publisher |
	|TCP connection| |TCP connection|		|TCP connection| |TCP connection|
	| (a) (b) | | (a) (b) |		| (a) (b) | | (a) (b) |
	skipping to change at page 7, line 35 ¶		skipping to change at page 5, line 35 ¶
	| |<---------------------------------------------|		| |<---------------------------------------------|
	| | SSE (event-notif)|		| | SSE (event-notif)|
	| |<---------------------------------------------|		| |<---------------------------------------------|
	| Restconf POST (RPC:delete-subscription) | |		| Restconf POST (RPC:delete-subscription) | |
	|--------------------------------------------->| |		|--------------------------------------------->| |
	| | HTTP 200 OK| |		| | HTTP 200 OK| |
	|<---------------------------------------------| |		|<---------------------------------------------| |
	| | |		| | |
	| |		| |
	Figure 3: Dynamic with HTTP1.1		Figure 2: Dynamic with HTTP1.1
	3.2.3. Configured Subscription over HTTP2		3.1.3. Configured Subscription over HTTP2
	With a Configured Subscription, all information needed to establish a		With a Configured Subscription, all information needed to establish a
	secure relationship with that Receiver is available on the Publisher.		secure relationship with that Receiver is available on the Publisher.
	With this information, the Publisher will establish a secure		With this information, the Publisher will establish a secure
	transport connection with the Receiver and then begin pushing the		transport connection with the Receiver and then begin pushing the
	Event Notifications to the Receiver. Since Restconf might not exist		Event Notifications to the Receiver. Since Restconf might not exist
	on the Receiver, it is not desirable to require that such Event		on the Receiver, it is not desirable to require that such Event
	Notifications be pushed with any dependency on Restconf. Nor is		Notifications be pushed with any dependency on Restconf. Nor is
	there value which Restconf provides on top of HTTP. Therefore in		there value which Restconf provides on top of HTTP. Therefore in
	place of Restconf, a TLS secured HTTP2 Client connection must be		place of Restconf, a TLS secured HTTP2 Client connection must be
	skipping to change at page 8, line 32 ¶		skipping to change at page 6, line 32 ¶
	|--------------------------------------------->|		|--------------------------------------------->|
	| | HTTP Post Headers, Data (event-notif)|		| | HTTP Post Headers, Data (event-notif)|
	| |<---------------------------------------------|		| |<---------------------------------------------|
	| | HTTP Data (event-notif)|		| | HTTP Data (event-notif)|
	| |<---------------------------------------------|		| |<---------------------------------------------|
	| | HTTP Data (sub-terminate)|		| | HTTP Data (sub-terminate)|
	| |<---------------------------------------------|		| |<---------------------------------------------|
	| |HTTP 200 OK |		| |HTTP 200 OK |
	| |--------------------------------------------->|		| |--------------------------------------------->|
	Figure 4: Configured over HTTP2		Figure 3: Configured over HTTP2
	As the HTTP2 transport is available to the Receiver, the Publisher		As the HTTP2 transport is available to the Receiver, the Publisher
	should:		should:
	o take any subscription-priority and copy it into the HTTP2 stream		o take any subscription-priority and copy it into the HTTP2 stream
	priority, and		priority, and
	o take a subscription-dependency if it has been provided and map the		o take a subscription-dependency if it has been provided and map the
	HTTP2 stream for the parent subscription into the HTTP2 stream		HTTP2 stream for the parent subscription into the HTTP2 stream
	dependency.		dependency.
	3.3. Subscription Multiplexing		3.2. Subscription Multiplexing
	It is possible that updates might be delivered in a different		It is possible that updates might be delivered in a different
	sequence than generated. Reasons for this might include (but are not		sequence than generated. Reasons for this might include (but are not
	limited to):		limited to):
	o replay of pushed updates		o replay of pushed updates
	o temporary loss of transport connectivity, with update buffering		o temporary loss of transport connectivity, with update buffering
	and different dequeuing priorities per Subscription		and different dequeuing priorities per Subscription
	o population, marshalling and bundling of independent Subscription		o population, marshalling and bundling of independent Subscription
	Updates, and		Updates, and
	Therefore each Event Notification will include a millisecond level		Therefore each Event Notification will include a timestamp to ensure
	timestamp to ensure that a Receiver understands the time when a that		that a Receiver understands the time when a that update was
	update was generated. Use of this timestamp can give an indication		generated. Use of this timestamp can give an indication of the state
	of the state of objects at a Publisher when state-entangled		of objects at a Publisher when state-entangled information is
	information is received across different subscriptions. The use of		received across different subscriptions. The use of the latest Event
	the latest Event Notification timestamp for a particular object		Notification timestamp for a particular object update can introduce
	update can introduce errors. So when state-entangled updates have		errors. So when state-entangled updates have inconsistent object
	inconsistent object values and temporally close timestamps, a		values and temporally close timestamps, a Receiver might consider
	Receiver might consider performing a GET to validate the current		performing a GET to validate the current state of a Publisher.
	state of a Publisher.
	3.4. Encoded Subscription and Event Notification Examples		4. Encoded Subscription and Event Notification Examples
	Transported updates will contain context data for one or more Event		Transported updates will contain context data for one or more Event
	Notifications. Each transported Event Notification will contain		Notifications. Each transported Event Notification will contain
	several parameters:		several parameters:
	3.4.1. Restconf Subscription and Events over HTTP1.1		4.1. Restconf Subscription and Events over HTTP1.1
	Subscribers can dynamically learn whether a RESTCONF server supports		Subscribers can dynamically learn whether a RESTCONF server supports
	various types of Event or Yang datastore subscription capabilities.		various types of Event or Yang datastore subscription capabilities.
	This is done by issuing an HTTP request OPTIONS, HEAD, or GET on the		This is done by issuing an HTTP request OPTIONS, HEAD, or GET on the
	stream. Some examples building upon the Call flow for HTTP1.1 from		stream. Some examples building upon the Call flow for HTTP1.1 from
	Section 3.2.2 are:		Section 3.2.2 are:
	GET /restconf/data/ietf-restconf-monitoring:restconf-state/		GET /restconf/data/ietf-restconf-monitoring:restconf-state/
	streams/stream=yang-push HTTP/1.1		streams/stream=yang-push HTTP/1.1
	Host: example.com		Host: example.com
	skipping to change at page 13, line 12 ¶		skipping to change at page 11, line 12 ¶
	the Subscription above. It contains a subtree with root foo that		the Subscription above. It contains a subtree with root foo that
	contains a leaf called bar:		contains a leaf called bar:
	XML encoding representation:		XML encoding representation:
	<?xml version="1.0" encoding="UTF-8"?>		<?xml version="1.0" encoding="UTF-8"?>
	<notification xmlns="urn:ietf:params:xml:ns:yang:ietf-restconf">		<notification xmlns="urn:ietf:params:xml:ns:yang:ietf-restconf">
	<subscription-id xmlns="urn:ietf:params:xml:ns:restconf:		<subscription-id xmlns="urn:ietf:params:xml:ns:restconf:
	datastore-push:1.0">		datastore-push:1.0">
	my-sub		my-sub
	</subscription-id>		</subscription-id>
	<eventTime>2015-03-09T19:14:56.23Z</eventTime>		<eventTime>2015-03-09T19:14:56.233Z</eventTime>
	<datastore-contents xmlns="urn:ietf:params:xml:ns:restconf:		<datastore-contents xmlns="urn:ietf:params:xml:ns:restconf:
	datastore-push:1.0">		datastore-push:1.0">
	<foo xmlns="http://example.com/yang-push/1.0">		<foo xmlns="http://example.com/yang-push/1.0">
	<bar>some_string</bar>		<bar>some_string</bar>
	</foo>		</foo>
	</datastore-contents>		</datastore-contents>
	</notification>		</notification>
	Or with the equivalent YANG over JSON encoding representation as		Or with the equivalent YANG over JSON encoding representation as
	defined in [RFC7951]:		defined in [RFC7951]:
	{		{
	"ietf-restconf:notification": {		"ietf-restconf:notification": {
	"datastore-push:subscription-id": "my-sub",		"datastore-push:subscription-id": "my-sub",
	"eventTime": "2015-03-09T19:14:56.23Z",		"eventTime": "2015-03-09T19:14:56.233Z",
	"datastore-push:datastore-contents": {		"datastore-push:datastore-contents": {
	"example-mod:foo": { "bar": "some_string" }		"example-mod:foo": { "bar": "some_string" }
	}		}
	}		}
	}		}
	To modify a Subscription, the subscriber issues another POST request		To modify a Subscription, the subscriber issues another POST request
	on the provided URI using the same subscription-id as in the original		on the provided URI using the same subscription-id as in the original
	request. For example, to modify the update period to 10 seconds, the		request. For example, to modify the update period to 10 seconds, the
	subscriber may send:		subscriber may send:
	skipping to change at page 14, line 9 ¶		skipping to change at page 12, line 9 ¶
	"ietf-event-notifications:input" : {		"ietf-event-notifications:input" : {
	?subscription-id?: 100,		?subscription-id?: 100,
	?period" : 10		?period" : 10
	}		}
	}		}
	To delete a Subscription, the Subscriber issues a DELETE request on		To delete a Subscription, the Subscriber issues a DELETE request on
	the provided URI using the same subscription-id as in the original		the provided URI using the same subscription-id as in the original
	request		request
	3.4.2. Event Notification over HTTP2		4.2. Event Notification over HTTP2
	The basic encoding will look as below. It will consists of a JSON		The basic encoding will look as below. It will consists of a JSON
	representation wrapped in an HTTP2 header.		representation wrapped in an HTTP2 header.
	HyperText Transfer Protocol 2		HyperText Transfer Protocol 2
	Stream: HEADERS, Stream ID: 5		Stream: HEADERS, Stream ID: 5
	Header: :method: POST		Header: :method: POST
	Stream: HEADERS, Stream ID: 5		Stream: HEADERS, Stream ID: 5
	{		{
	"ietf-yangpush:notification": {		"ietf-yangpush:notification": {
	"datastore-push:subscription-id": "my-sub",		"datastore-push:subscription-id": "my-sub",
	"eventTime": "2015-03-09T19:14:56.23Z",		"eventTime": "2015-03-09T19:14:56.233Z",
	"datastore-push:datastore-contents": {		"datastore-push:datastore-contents": {
	"foo": { "bar": "some_string" }		"foo": { "bar": "some_string" }
	}		}
	}		}
	}		}
	3.5. Stream Discovery		5. Security Considerations
	Relevant for Dynamic Subscriptions, this will be accomplished as
	specified in [restconf] section 6.2. The namespace chosen will be
	the same as how stream names are acquired for NETCONF, and so that
	backwards compatibility can be maintained without replicating this
	information.
	As per [restconf] section 6.3, RESTCONF clients can determine the URL
	for the subscription resource (to receive notifications) by sending
	an HTTP GET request for the "location" leaf with the stream list
	entry.
	4. Security Considerations
	Subscriptions could be used to intentionally or accidentally overload		Subscriptions could be used to intentionally or accidentally overload
	the resources of a Publisher. For this reason, it is important that		the resources of a Publisher. For this reason, it is important that
	the Publisher has the ability to prioritize the establishment and		the Publisher has the ability to prioritize the establishment and
	push of Event Notifications where there might be resource exhaust		push of Event Notifications where there might be resource exhaust
	potential. In addition, a server needs to be able to suspend		potential. In addition, a server needs to be able to suspend
	existing Subscriptions when needed. When this occurs, the		existing Subscriptions when needed. When this occurs, the
	subscription status must be updated accordingly and the Receivers		subscription status must be updated accordingly and the Receivers
	notified.		notified.
	skipping to change at page 15, line 28 ¶		skipping to change at page 13, line 14 ¶
	terminate or refuse any transport sessions from the Publisher.		terminate or refuse any transport sessions from the Publisher.
	Second, the HTTP transport augmentation on the Receiver must send an		Second, the HTTP transport augmentation on the Receiver must send an
	HTTP 200 OK to a subscription started notification before the		HTTP 200 OK to a subscription started notification before the
	Publisher starts streaming any events.		Publisher starts streaming any events.
	One or more Publishers could overwhelm a Receiver which is unable to		One or more Publishers could overwhelm a Receiver which is unable to
	control or handle the volume of Event Notifications received. In		control or handle the volume of Event Notifications received. In
	deployments where this might be a concern, HTTP2 transport such as		deployments where this might be a concern, HTTP2 transport such as
	HTTP2) should be selected.		HTTP2) should be selected.
	5. Acknowledgments		6. Acknowledgments
	We wish to acknowledge the helpful contributions, comments, and		We wish to acknowledge the helpful contributions, comments, and
	suggestions that were received from: Susan Hares, Tim Jenkins, Balazs		suggestions that were received from: Susan Hares, Tim Jenkins, Balazs
	Lengyel, Kent Watsen, Michael Scharf, and Guangying Zheng.		Lengyel, Kent Watsen, Michael Scharf, and Guangying Zheng.
	6. References		7. References
	6.1. Normative References
	[restconf]		7.1. Normative References
	Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
	Protocol", March 2016, <https://datatracker.ietf.org/doc/
	draft-ietf-netconf-restconf/>.
	[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,		Requirement Levels", BCP 14, RFC 2119,
	DOI 10.17487/RFC2119, March 1997,		DOI 10.17487/RFC2119, March 1997,
	<http://www.rfc-editor.org/info/rfc2119>.		<http://www.rfc-editor.org/info/rfc2119>.
	[RFC6520] Seggelmann, R., Tuexen, M., and M. Williams, "Transport		[RFC6520] Seggelmann, R., Tuexen, M., and M. Williams, "Transport
	Layer Security (TLS) and Datagram Transport Layer Security		Layer Security (TLS) and Datagram Transport Layer Security
	(DTLS) Heartbeat Extension", RFC 6520,		(DTLS) Heartbeat Extension", RFC 6520,
	DOI 10.17487/RFC6520, February 2012,		DOI 10.17487/RFC6520, February 2012,
	skipping to change at page 16, line 15 ¶		skipping to change at page 13, line 45 ¶
	[RFC6536] Bierman, A. and M. Bjorklund, "Network Configuration		[RFC6536] Bierman, A. and M. Bjorklund, "Network Configuration
	Protocol (NETCONF) Access Control Model", RFC 6536,		Protocol (NETCONF) Access Control Model", RFC 6536,
	DOI 10.17487/RFC6536, March 2012,		DOI 10.17487/RFC6536, March 2012,
	<http://www.rfc-editor.org/info/rfc6536>.		<http://www.rfc-editor.org/info/rfc6536>.
	[RFC7540] Belshe, M., Peon, R., and M. Thomson, Ed., "Hypertext		[RFC7540] Belshe, M., Peon, R., and M. Thomson, Ed., "Hypertext
	Transfer Protocol Version 2 (HTTP/2)", RFC 7540,		Transfer Protocol Version 2 (HTTP/2)", RFC 7540,
	DOI 10.17487/RFC7540, May 2015,		DOI 10.17487/RFC7540, May 2015,
	<http://www.rfc-editor.org/info/rfc7540>.		<http://www.rfc-editor.org/info/rfc7540>.
			[RFC8040] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
			Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017,
			<http://www.rfc-editor.org/info/rfc8040>.
			[sn] Voit, E., Clemm, A., Gonzalez Prieto, A., Prasad Tripathy,
			A., and E. Nilsen-Nygaard, "Subscribing to Event
			Notifications", February 2017,
			<https://datatracker.ietf.org/doc/draft-ietf-netconf-
			subscribed-notifications/>.
			7.2. Informative References
	[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,
	<http://www.rfc-editor.org/info/rfc7923>.		<http://www.rfc-editor.org/info/rfc7923>.
	[RFC7951] Lhotka, L., "JSON Encoding of Data Modeled with YANG",		[RFC7951] Lhotka, L., "JSON Encoding of Data Modeled with YANG",
	RFC 7951, DOI 10.17487/RFC7951, August 2016,		RFC 7951, DOI 10.17487/RFC7951, August 2016,
	<http://www.rfc-editor.org/info/rfc7951>.		<http://www.rfc-editor.org/info/rfc7951>.
	6.2. Informative References		[RFC8071] Watsen, K., "NETCONF Call Home and RESTCONF Call Home",
			RFC 8071, DOI 10.17487/RFC8071, February 2017,
	[call-home]		<http://www.rfc-editor.org/info/rfc8071>.
	Watsen, K., "NETCONF Call Home and RESTCONF Call Home",
	December 2015, <https://tools.ietf.org/html/draft-ietf-
	netconf-call-home-17>.
	[rfc5277bis]
	Gonzalez Prieto, A., Clemm, A., Voit, E., Prasad Tripathy,
	A., and E. Nilsen-Nygaard, "NETCONF Event Notifications",
	September 2016, <https://datatracker.ietf.org/doc/draft-
	ietf-netconf-rfc5277bis/>.
	[W3C-20150203]		[W3C-20150203]
	"Server-Sent Events, World Wide Web Consortium CR CR-		"Server-Sent Events, World Wide Web Consortium CR CR-
	eventsource-20121211", February 2015,		eventsource-20121211", February 2015,
	<https://www.w3.org/TR/2015/REC-eventsource-20150203/>.		<https://www.w3.org/TR/2015/REC-eventsource-20150203/>.
	[yang-push]		[yang-push]
	Clemm, A., Voit, E., Gonzalez Prieto, A., Prasad Tripathy,		Clemm, A., Voit, E., Gonzalez Prieto, A., Prasad Tripathy,
	A., and E. Nilsen-Nygaard, "Subscribing to YANG datastore		A., Nilsen-Nygaard, E., Bierman, A., and B. Lengyel,
	push updates", June 2016,		"Subscribing to YANG datastore push updates", March 2017,
	<https://datatracker.ietf.org/doc/draft-ietf-netconf-yang-		<https://datatracker.ietf.org/doc/draft-ietf-netconf-yang-
	push/>.		push/>.
	Appendix A. Proxy YANG Subscription when the Subscriber and Receiver		Appendix A. End-to-End Deployment Guidance
	are different
	The properties of Dynamic and Configured Subscriptions can be
	combined to enable deployment models where the Subscriber and
	Receiver are different. Such separation can be useful with some
	combination of:
	o An operator does not want the subscription to be dependent on the
	maintenance of transport level keep-alives. (Transport
	independence provides different scalability characteristics.)
	o There is not a transport session binding, and a transient
	Subscription needs to survive in an environment where there is
	unreliable connectivity with the Receiver and/or Subscriber.
	o An operator wants the Publisher to include highly restrictive
	capacity management and Subscription security mechanisms outside
	of domain of existing operational or programmatic interfaces.
	To build a Proxy Subscription, first the necessary information must
	be signaled as part of the <establish-subscription>. Using this set
	of Subscriber provided information; the same process described within
	section 3 will be followed. There is one exception. Only when an
	HTTP status code of 200 comes back from the receiver, will it inform
	the Subscriber of Subscription establishment success via its Restconf
	connection.
	After a successful establishment, if the Subscriber wishes to track
	the state of Receiver subscriptions, it may choose to place a
	separate on-change Subscription into the "Subscriptions" subtree of
	the YANG Datastore on the Publisher.
	Appendix B. End-to-End Deployment Guidance
	Several technologies are expected to be seen within a deployment to		Several technologies are expected to be seen within a deployment to
	achieve security and ease-of-use requirements. These are not		achieve security and ease-of-use requirements. These are not
	necessary for an implementation of this specification, but will be		necessary for an implementation of this specification, but will be
	useful to consider when considering the operational context.		useful to consider when considering the operational context.
	B.1. Call Home		A.1. Call Home
	Pub/Sub implementations should have the ability to transparently		Pub/Sub implementations should have the ability to transparently
	incorporate [call-home] so that secure TLS connections can originate		incorporate 'call home' [RFC8071] so that secure TLS connections can
	from the desired device.		originate from the desired device.
	B.2. TLS Heartbeat		A.2. TLS Heartbeat
	HTTP sessions might not quickly allow a Subscriber to recognize when		HTTP sessions might not quickly allow a Subscriber to recognize when
	the communication path has been lost from the Publisher. To		the communication path has been lost from the Publisher. To
	recognize this, it is possible for a Receiver to establish a TLS		recognize this, it is possible for a Receiver to establish a TLS
	heartbeat [RFC6520]. In the case where a TLS heartbeat is included,		heartbeat [RFC6520]. In the case where a TLS heartbeat is included,
	it should be sent just from Receiver to Publisher. Loss of the		it should be sent just from Receiver to Publisher. Loss of the
	heartbeat should result in any Subscription related TCP sessions		heartbeat should result in any Subscription related TCP sessions
	between those endpoints being torn down. The subscription can then		between those endpoints being torn down. The subscription can then
	attempt to re-establish.		attempt to re-establish.
	Appendix C. Issues being worked and resolved		Appendix B. Issues being worked and resolved
	(To be removed by RFC editor prior to publication)		(To be removed by RFC editor prior to publication)
	C.1. Unresolved Issues		B.1. Unresolved Issues
	RT3 - Do we include 3rd party signaled subscriptions within models
	that need to be supported generically, or for a particular type of
	transport.
	RT10 - Right now the examples show a YANG timestamp at the hundredths
	of a second level. But the yang-push draft is at seconds. And the
	requirements show at least milliseconds (if not more).
	C.2. Agreement in principal
	RT4 - Need to add into document examples of 5277bis Event streams.		GRPC compatibility 1: Mechanisms for HTTP2 to GRPC mapping need to be
	Document only includes yang-push examples at this point.		considered. There is a good start there as this draft only uses
			POST, not GET. As GET is used in RESTCONF for capabilities
			discovery, we have some backwards compatibility issues with existing
			IETF drafts. Possible options to address are (1) provide a POST
			method for anything done by GET in RESTCONF, (2) await support of GET
			by GRPC, or (3) tunnel RESTCONF's GET messages within a GRPC POST.
	RT6 - We need to define encodings of rfc5277bis notifications.		GRPC compatibility 2: We need to expose a method against which POST
			is done as events begin on a stream. See Stream 7 in figure 2. Can
			only send traffic to a method, not a URI. URI points to a method,
			not a resource.
	C.3. Resolved Issues		Need to add into document examples of Event streams. Document only
			includes yang-push examples at this point.
	RT1 - Integration specifics for Restconf capability discovery on		We need to reference the viable encodings of notifications.
	different types of Streams
	RT2 - In what way to we position Event notifications model in this		Appendix C. Changes between revisions
	document vs. current solution in Restconf.
	RT5 - Doesn't make sense to use Restconf for Configured		(To be removed by RFC editor prior to publication)
	subscriptions. HTTP will be used.
	RT7 - HTTP native option doesn't currently use SSE. But we should		v01 - v02
	evaluate moving to that as possible. It will make development
	integration easier and more consistent.
	RT8 - Once SSE starts, there will be no more Restconf interpretation		o Removed sections now redundant with [sn] and [yang-push] such as:
	of further signaling upon the connection. It is unclear how this can		mechanisms for subscription maintenance, terminology definitions,
	be made to work with modify and delete subscription. If it cannot, a		stream discovery.
	method of sending events without SSE will be needed, although this
	would diverge from the existing Restconf mechanisms
	RT9 - For static subscriptions, perhaps we can use Restconf call home		o 3rd party subscriptions are out-of-scope.
	to originate an SSE connection. This assume RT8 & RT2 can be
	resolved with SSE.
	Appendix D. Changes between revisions		o SSE only used with Restconf and HTTP1.1 Dynamic Subscriptions
			o Timeframes for event tagging are self-defined.
	(To be removed by RFC editor prior to publication)		o Clean-up of wording, references to terminology, section numbers.
	v00 - v01		v00 - v01
	o Removed the ability for more than one subscription to go to a		o Removed the ability for more than one subscription to go to a
	single HTTP2 stream.		single HTTP2 stream.
	o Updated call flows. Extensively.		o Updated call flows. Extensively.
	o SSE only used with Restconf and HTTP1.1 Dynamic Subscriptions		o SSE only used with Restconf and HTTP1.1 Dynamic Subscriptions
	skipping to change at page 19, line 40 ¶		skipping to change at page 16, line 29 ¶
	o Many clean-ups of wording and terminology		o Many clean-ups of wording and terminology
	Authors' Addresses		Authors' Addresses
	Eric Voit		Eric Voit
	Cisco Systems		Cisco Systems
	Email: evoit@cisco.com		Email: evoit@cisco.com
	Alexander Clemm
	Cisco Systems
	Email: alex@clemm.org
	Alberto Gonzalez Prieto		Alberto Gonzalez Prieto
	Cisco Systems		Cisco Systems
	Email: albertgo@cisco.com		Email: albertgo@cisco.com
	Ambika Prasad Tripathy		Ambika Prasad Tripathy
	Cisco Systems		Cisco Systems
	Email: ambtripa@cisco.com		Email: ambtripa@cisco.com
	Einar Nilsen-Nygaard		Einar Nilsen-Nygaard
	Cisco Systems		Cisco Systems
	Email: einarnn@cisco.com		Email: einarnn@cisco.com
			Alexander Clemm
			Huawei
			Email: ludwig@clemm.org
	Andy Bierman		Andy Bierman
	YumaWorks		YumaWorks
	Email: andy@yumaworks.com		Email: andy@yumaworks.com
End of changes. 56 change blocks.
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