draft-ietf-i2rs-ephemeral-state-00.txt		draft-ietf-i2rs-ephemeral-state-01.txt
	I2RS working group J. Haas		I2RS working group J. Haas
	Internet-Draft Juniper		Internet-Draft Juniper
	Intended status: Standards Track S. Hares		Intended status: Standards Track S. Hares
	Expires: December 25, 2015 Huawei		Expires: February 29, 2016 Huawei
	June 23, 2015		August 28, 2015
	I2RS Ephemeral State Requirements		I2RS Ephemeral State Requirements
	draft-ietf-i2rs-ephemeral-state-00		draft-ietf-i2rs-ephemeral-state-01
	Abstract		Abstract
	This document covers requests to the netmod and netconf Working		This document covers requests to the netmod and netconf Working
	Groups for functionality to support the ephemeral state requirements		Groups for functionality to support the ephemeral state requirements
	to implement the I2RS architecture.		to implement the I2RS architecture.
	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
	skipping to change at page 1, line 33		skipping to change at page 1, line 33
	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 December 25, 2015.		This Internet-Draft will expire on February 29, 2016.
	Copyright Notice		Copyright Notice
	Copyright (c) 2015 IETF Trust and the persons identified as the		Copyright (c) 2015 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
	skipping to change at page 2, line 12		skipping to change at page 2, line 12
	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. Review of Requirements from I2RS architecture document . . . 3		2. Review of Requirements from I2RS architecture document . . . 3
	3. Ephemeral State Requirements . . . . . . . . . . . . . . . . 4		3. Ephemeral State Requirements . . . . . . . . . . . . . . . . 4
	3.1. Persistence . . . . . . . . . . . . . . . . . . . . . . . 4		3.1. Persistence . . . . . . . . . . . . . . . . . . . . . . . 4
	3.2. Constraints . . . . . . . . . . . . . . . . . . . . . . . 4		3.2. Constraints . . . . . . . . . . . . . . . . . . . . . . . 4
	3.3. Hierarchy . . . . . . . . . . . . . . . . . . . . . . . . 4		3.3. Hierarchy . . . . . . . . . . . . . . . . . . . . . . . . 5
	4. changes to YANG . . . . . . . . . . . . . . . . . . . . . . . 5		3.4. changes to YANG . . . . . . . . . . . . . . . . . . . . . 5
	5. Changes to NETCONF . . . . . . . . . . . . . . . . . . . . . 5		3.5. Minimal sub-set of Changes . . . . . . . . . . . . . . . 5
	6. Requirements regarding Identity, Secondary-Identity and		3.6. Requirements regarding Identity, Secondary-Identity and
	Priority . . . . . . . . . . . . . . . . . . . . . . . . . . 6		Priority . . . . . . . . . . . . . . . . . . . . . . . . 5
	6.1. Identity Requirements . . . . . . . . . . . . . . . . . . 6		3.6.1. Identity Requirements . . . . . . . . . . . . . . . . 5
	6.2. Priority Requirements . . . . . . . . . . . . . . . . . . 6		3.6.2. Priority Requirements . . . . . . . . . . . . . . . . 5
	6.3. Representing I2RS Attributes in ephemeral configuration		3.6.3. Transactions . . . . . . . . . . . . . . . . . . . . 6
	state . . . . . . . . . . . . . . . . . . . . . . . . . . 7		3.6.4. Subscriptions to Changed State Requirements . . . . . 7
	6.4. Semantics around storing and managing of priority and		4. Previously Considered Ideas . . . . . . . . . . . . . . . . . 8
	client ID. . . . . . . . . . . . . . . . . . . . . . . . 7		4.1. A Separate Ephemeral Datastore . . . . . . . . . . . . . 8
	7. Subscriptions to Changed State Requirements . . . . . . . . . 9		4.2. Panes of Glass/Overlay . . . . . . . . . . . . . . . . . 8
	8. Transactions . . . . . . . . . . . . . . . . . . . . . . . . 10		5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
	9. Previously Considered Ideas . . . . . . . . . . . . . . . . . 10		6. Security Considerations . . . . . . . . . . . . . . . . . . . 9
	9.1. A Separate Ephemeral Datastore . . . . . . . . . . . . . 10		7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9
	9.2. Panes of Glass/Overlay . . . . . . . . . . . . . . . . . 11		8. References . . . . . . . . . . . . . . . . . . . . . . . . . 10
	10. Actions Required to Implement this Draft . . . . . . . . . . 11		8.1. Normative References: . . . . . . . . . . . . . . . . . . 10
	11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11		8.2. Informative References . . . . . . . . . . . . . . . . . 10
	12. Security Considerations . . . . . . . . . . . . . . . . . . . 12		Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11
	13. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 12
	14. References . . . . . . . . . . . . . . . . . . . . . . . . . 12
	14.1. Normative References: . . . . . . . . . . . . . . . . . 12
	14.2. Informative References . . . . . . . . . . . . . . . . . 13
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 13
	1. Introduction		1. Introduction
	The Interface to the Routing System (I2RS) Working Group is chartered		The Interface to the Routing System (I2RS) Working Group is chartered
	with providing architecture and mechanisms to inject into and		with providing architecture and mechanisms to inject into and
	retrieve information from the routing system. The I2RS Architecture		retrieve information from the routing system. The I2RS Architecture
	document [I-D.ietf-i2rs-architecture] abstractly documents a number		document [I-D.ietf-i2rs-architecture] abstractly documents a number
	of requirements for implementing the I2RS requirements.		of requirements for implementing the I2RS requirements.
	The I2RS Working Group has chosen to use the YANG data modeling		The I2RS Working Group has chosen to use the YANG data modeling
	language [RFC6020] as the basis to implement its mechanisms.		language [RFC6020] as the basis to implement its mechanisms.
	Additionally, the I2RS Working group has chosen to use the NETCONF		Additionally, the I2RS Working group has chosen to use the NETCONF
	[RFC6241] and its similar but lighter-weight relative RESTCONF		[RFC6241] and its similar but lighter-weight relative RESTCONF
	[I-D.bierman-netconf-restconf] as the protocols for carrying I2RS.		[I-D.ietf-netconf-restconf] as the protocols for carrying I2RS.
	While YANG, NETCONF and RESTCONF are a good starting basis for I2RS,		While YANG, NETCONF and RESTCONF are a good starting basis for I2RS,
	there are some things needed from each of them in order for I2RS to		there are some things needed from each of them in order for I2RS to
	be implemented.		be implemented.
	2. Review of Requirements from I2RS architecture document		2. Review of Requirements from I2RS architecture document
	The following are ten requirements that [I-D.ietf-i2rs-architecture]		The following are ten requirements that [I-D.ietf-i2rs-architecture]
	contains which are important high level requirements:		contains which are important high level requirements:
	skipping to change at page 4, line 26		skipping to change at page 4, line 22
	10. The I2RS protocol MUST support the use of a secure transport.		10. The I2RS protocol MUST support the use of a secure transport.
	However, certain functions such as notifications MAY use a non-		However, certain functions such as notifications MAY use a non-
	secure transport. Each model or service (notification, logging)		secure transport. Each model or service (notification, logging)
	must define within the model or service the valid uses of a non-		must define within the model or service the valid uses of a non-
	secure transport.		secure transport.
	3. Ephemeral State Requirements		3. Ephemeral State Requirements
	3.1. Persistence		3.1. Persistence
	I2RS requires ephemeral state; i.e. state that does not persist		Ephemeral-REQ-01: I2RS requires ephemeral state; i.e. state that does
	across reboots. If state must be restored, it should be done solely		not persist across reboots. If state must be restored, it should be
	by replay actions from the I2RS client via the I2RS agent.		done solely by replay actions from the I2RS client via the I2RS
			agent.
	While at first glance this may seem equivalent to the writable-		While at first glance this may seem equivalent to the writable-
	running datastore in NETCONF, running-config can be copied to a		running datastore in NETCONF, running-config can be copied to a
	persistant data store, like startup config. I2RS ephemeral state		persistant data store, like startup config. I2RS ephemeral state
	MUST NOT be persisted.		MUST NOT be persisted.
	3.2. Constraints		3.2. Constraints
	Ephemeral state MAY refer to non-ephemeral state for purposes of		Ephemeral-REQ-02: Non-ephemeral state MUST NOT refer to ephemeral
	implementing constraints. The designer of ephemeral state modules		state for constraint purposes; it SHALL be considered a validation
	are advised that such constraints may impact the speed of processing		error if it does.
	ephemeral state commits and should avoid them when speed is
	essential.
	Non-ephemeral state MUST NOT refer to ephemeral state for constraint
	purposes; it SHALL be considered a validation error if it does.
	3.3. Hierarchy
	Similar to configuration state (config true, see [RFC6020], section
	7.19.1), ephemeral state is not permitted to be configured underneath
	nodes that are "config false" (state data).
	Configuration of ephemeral state underneath "config true" is
	permitted. This permits augmentation of configuration state with
	ephemeral nodes.
	Configuration of "config true" state underneath ephemeral state MUST
	NOT be done.
	State data, "config false", is permitted underneath ephemeral state.
	This state data is part of the ephemeral module and should become
	inaccessible if the ephemeral module reboots.
	4. changes to YANG		Ephemeral-REQ-03: Ephemeral state must be able to utilized temporary
			operational state which (MPLS LSP-ID or a BGP IN-RIB) as a
			constraints.
	The YANG "config" keyword ([RFC6020], section 7.19.1) is extended to		Ephemeral-REQ-04> Ephemeral state MAY refer to non-ephemeral state
	support the keyword "ephemeral" in addition to "true" and "false".		for purposes of implementing constraints. The designer of ephemeral
	"config ephemeral" declares the nodes underneath to be ephemeral		state modules are advised that such constraints may impact the speed
	configuration.		of processing ephemeral state commits and should avoid them when
			speed is essential.
	5. Changes to NETCONF		3.3. Hierarchy
	A capability is registered declaring that the server supports		Ephemeral-REQ-05: The ability to add on an object (or a hierarchy of
	ephemeral configuration. E.g.:		objects) that have the property of being ephemeral. An object needs
			to be able to have (both) the property of being writable and the
			property of the data being ephemeral (or non-ephemeral).
	:ephemeral-config		3.4. changes to YANG
	urn:ietf:params:netconf:capability:ephemeral-config:1.0
	<get-config> will normally return "config ephemeral" nodes as it is a		Ephemeral-REQ-06: Yang MUST have a way to indicate in a data model
	form of configuration. It is further extended to add a new		that nodes have the following properties: ephemeral, writable/not-
	parameter, "filter-ephemeral". This parameter accepts the following		writable, status/configuration.
	arguments:
	o none (default): No filtering of persistent or ephemeral state is		3.5. Minimal sub-set of Changes
	done.
	o ephemeral-only: Only nodes representing ephemeral state are		Ephemeral-REQ-07: The minimal set is ...
	returned.
	o exclude-ephemeral: Only persistent configuration is returned.		Potential set:
	<get> is similarly extended to support "filter-ephemeral".		3.6. Requirements regarding Identity, Secondary-Identity and Priority
	When a <copy-config> is done, regardless of datastore, nodes that are		3.6.1. Identity Requirements
	"config ephemeral" are excluded from the target output.
	6. Requirements regarding Identity, Secondary-Identity and Priority		Ephemeral-REQ-08:Clients shall have identities, and secondary
			identities.
	6.1. Identity Requirements		Explanation
	I2RS requires clients to have an identity. This identity will be		I2RS requires clients to have an identity. This identity will be
	used by the Agent authentication mechanism over the appropriate		used by the Agent authentication mechanism over the appropriate
	protocol.		protocol.
	I2RS also permits clients to have a secondary identity which may be		The Secondary identities can be carried as part of RPC or meta-data.
	used for troubleshooting. This secondary identity is an opaque		The primary purpose of the secondary identity is for traceability
	value. [I-D.ietf-i2rs-traceability] provides an example of how the		information which logs (who modifies certain nodes). This secondary
	secondary identity can be used for traceability.		identity is an opaque value. [I-D.ietf-i2rs-traceability] provides
			an example of how the secondary identity can be used for
	The secondary identity is carried in the configuration operation		traceability.
	using a new parameter to <edit-config>. E.g.:
	<rpc message-id="101" xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
	<edit-config>
	<i2rs:irs-secondary-identity>user1</i2rs>
	<target>
	<running/>
	</target>
	<config>
	<top xmlns="http://example.com/schema/1.2/config">
	<interface>
	<name>Ethernet0/0</name>
	<mtu>1500</mtu>
	</interface>
	</top>
	</config>
	</edit-config>
	</rpc>
	"config ephemeral" nodes that are created or altered as part of the
	config operation will carry the secondary-identity as read-only
	metadata.
	6.2. Priority Requirements		3.6.2. Priority Requirements
	To support Multi-Headed Control, I2RS requires that there be a		To support Multi-Headed Control, I2RS requires that there be a
	decidable means of arbitrating the correct state of data when		decidable means of arbitrating the correct state of data when
	multiple clients attempt to manipulate the same piece of data. This		multiple clients attempt to manipulate the same piece of data. This
	is done via a priority mechanism with the highest priority winning.		is done via a priority mechanism with the highest priority winning.
	This priority is per-client.		This priority is per-client.
	This further implies that priority is an attribute that is stored in		Ephemeral-REQ-09: The data nodes MAY store I2RS client identity and
	the NETCONF Access Control Model [RFC6536] as part of the group.		not the effective priority at the time the data node is stored. The
	E.g.:		I2RS Client MUST have one priority at a time. The priority MAY be
			dynamically changed by AAA, but the exact actions are part of the
			protocol definition as long as Collisions are handled as described in
			Ephemeral-REQ-10, Ephemeral-REQ-11, and Ephemeral-REQ-12.
	+--rw nacm		Ephemeral-REQ-10: When a collision occurs as two clients are trying
	+--rw enable-nacm? boolean		to write the same data node, this collision is considered an error
	+--rw read-default? action-type		and priorities were created to give a deterministic result. When
	+--rw write-default? action-type		there is a collision, a notification MUST BE sent to the original
	+--rw exec-default? action-type		client to give the original client a chance to deal with the issues
	+--rw enable-external-groups? boolean		surrounding the collision. The original client may need to fix their
	+--ro denied-operations yang:zero-based-counter32		state.
	+--ro denied-data-writes yang:zero-based-counter32
	+--ro denied-notifications yang:zero-based-counter32		Ephemeral-REQ-11: The requirement to support multi-headed control is
	+--rw groups		required for collisions and the priority resolution of collisions.
	| +--rw group [name]		Multi-headed control is not tied to ephemeral state. I2RS is not
	| +--rw name group-name-type		mandating how AAA supports priority. Mechanisms which prevent
	| +--rw user-name* user-name-type		collisions of two clients trying the same node of data are the focus.
	| +--rw i2rs:i2rs-priority i2rs-priority-type
			Ephemeral-REQ-12: If two clients have the same priority, the
			architecture says the first one wins. The I2RS protocol has this
			requirement to prevent was the oscillation between clients. If one
			uses the last wins scenario, you may oscillate. That was our
			opinion, but a design which prevents oscillation is the key point.
			Hints for Implementation
	Ephemeral configuration state nodes that are created or altered by		Ephemeral configuration state nodes that are created or altered by
	users that match a rule carrying i2rs-priority will have those nodes		users that match a rule carrying i2rs-priority will have those nodes
	annotated with metadata. Additionally, during commit processing, if		annotated with metadata. Additionally, during commit processing, if
	nodes are found where i2rs-priority is already present, and the		nodes are found where i2rs-priority is already present, and the
	priority is better than the transaction's user's priority for that		priority is better than the transaction's user's priority for that
	node, the commit SHALL fail. An appropriate error should be returned		node, the commit should fail. An appropriate error should be
	to the user stating the nodes where the user had insufficient		returned to the user stating the nodes where the user had
	priority to override the state.		insufficient priority to override the state.
	6.3. Representing I2RS Attributes in ephemeral configuration state
	I2RS attributes may be modeled as meta-data,
	[I-D.ietf-netmod-yang-metadata]. This meta-data MUST be read-only;
	operations attempting to alter it MUST be silently ignored. An I2RS
	module will be defined to document this meta data. An example of its
	use:
	<foo xmlns:i2rs="https://ietf.example.com/i2rs"
	i2rs:i2rs-secondary-identity="user1" i2rs:i2rs-priority="47">
	...
	</foo>
	6.4. Semantics around storing and managing of priority and client ID.
	The semantics and desired behavior around the storing and managing of
	priority and client ID have the following properties:
	1. First - the priority mechanism is intended to handle "error cases
	of colliding writes" in a predictable way that results in a
	consistent mechanism. It is true that the same mechanism could
	be used if they were not considered "errors", but it is important
	to minimize the need and impact of the priority mechanism
	2. Second, if there is a priority conflict where both clients
	(Client_A and Client_B) share the same priority, the client that
	wrote first wins. This is to avoid network oscillation if two
	clients are "fighting" over writing the same state. When there
	are multiple clients and the time arrival of the messages may not
	be predictable (network transit differences, which socket is
	read, software differences), basing state on last arrival time
	doesn't give consistent and predictable behavior. That gives
	behavior ont the following time-line
	1. Time_1: Client_A writes X=N with priority 10
	2. Time_2: Client_B attempts to write X=K with priority 10 and
	is rejected
	3. Time_3: Client_A writes X=P with priority 10 and succeeds
	For the I2RS Agent to properly handle these actions, it is
	necessary to know that X is owned by Client_A. Priority alone is
	not sufficient because the basis for rejecting Client_B's write
	but accepting Client_A's write is that Client_A is the owner.
	Thus it is necessary to store the Client Identity with the nodes
	that it owns. This could be in an I2RS-specific overlay that is
	only used by the I2RS agent and only contains the nodes that have
	been written by I2RS.
	3. Third, a question has come up regarding what the behavior of
	priority is if a client's priority changes and whether priority
	needs to be stored with each node when that node is written. In
	my "keep-it-simple" perspective, priority is associated with a
	Client and is only used on a conflict. This would mean that
	priority is not stored with a node when that node is written.
	Instead, the Client Identity is stored with the node and the
	Client's priority is looked up in a client table that the I2RS
	Agent can access. That client table could be populated via
	configuration, via a AAA protocol, via NACM, etc. The sematic
	implications are as follows:
	1. Time_1: Client_A writes X=N with priority 10
	2. Time_2: Client_A's priority is changed (UNUSUAL) to priority
	6
	3. Time_3: Client_B writes X=K with priority 8 (succeeds since 8
	> 6)
	4. Time_4: Client_A attempts to write X=N with priority 6 (fails
	b/c 8 > > 6)
	5. Time_5: Client_B's priority is changed (UNUSUAL) to priority
	7
	6. Time_6 Client_B writes X=P with priority 7 and succeeds (same
	> owner, no priority check)
	The alternate approach would have store the priority with which a		3.6.3. Transactions
	node was written. That is more like a priority lock that could
	only be changed by a client with higher priority or by the same
	client, regardless of priority. This approach would require
	storing a priority per node and the semantic implications would
	be as follows:
	1. Time_1:Client_A writes X=N with priority 10		Ephemeral-REQ-13: Section 7.9 of the [I-D.ietf-i2rs-architecture]
			states the I2RS architecture does not include multi-message atomicity
			and roll-back mechanisms, but suggests an I2RS client may indicates
			one of the following error handling techniques for a given message
			sent to the I2RS client:
	2. Time_2:Client_A's priority is changed (UNUSUAL) to priority 6		1. Perform all or none: All operations succeed or none of them will
			be applied. This useful when there are mutual dependencies.
	3. Time_3: Client_B attempts to write X=K with priority 8 and		2. Perform until error: Operations are applied in order, and when
	fails (10 > 8)		error occurs the processing stops. This is useful when
			dependencies exist between multiple-message operations, and order
			is important.
	4. Time_4: Client_A writes X=N with priority 6 and succeeds		3. Perform all storing errors: Perform all actions storing error
	(same owner, no priority check)		indications for errors. This method can be used when there are
			no dependencies between operations, and the client wants to sort
			it out.
	5. Time_5: Client_B's priority is changed (UNUSUAL) to priority		I2RS-REQ-XX: None of these three error handling for multi-message
	7		cases SHOULD cause errors into be insert the I2RS ephemeral data-
			store.
	6. Time_6 Client_B writes X=P with priority 7 and succeeds (7 >		Discussion of Current NETCONF/RESTCONF versus
	6)
	The behavior for these two models is different at Time_3 and		RESTCONF does an atomic action within a http session, and NETCONF has
	Time_4.		atomic actions within a commit. These features may be used to
			perform these features.
	The initial preference was that the priority is not stored with the		I2RS processing is dependent on the I2RS model. The I2RS model must
	node, but if it necessary to store it with the node additional		consider the dependencies within multiple operations work within a
	discussion may be needed with the I2RS WG.		model.
	7. Subscriptions to Changed State Requirements		3.6.4. Subscriptions to Changed State Requirements
	I2RS clients require the ability to monitor changes to ephemeral		I2RS clients require the ability to monitor changes to ephemeral
	state. While subscriptions are well defined for receiving		state. While subscriptions are well defined for receiving
	notifications, the need to create a notification set for all		notifications, the need to create a notification set for all
	ephemeral configuration state may be overly burdensome to the user.		ephemeral configuration state may be overly burdensome to the user.
	There is thus a need for a general subscription mechanism that can		There is thus a need for a general subscription mechanism that can
	provide notification of changed state, with sufficient information to		provide notification of changed state, with sufficient information to
	permit the client to retrieve the impacted nodes. This should be		permit the client to retrieve the impacted nodes. This should be
	doable without requiring the notifications to be created as part of		doable without requiring the notifications to be created as part of
	every single I2RS module.		every single I2RS module.
	8. Transactions		The following requirements from the
			[I-D.ietf-i2rs-pub-sub-requirements] apply to ephemeral state:
	Section 7.9 of the [I-D.ietf-i2rs-architecture] states the I2RS		o PubSub-REQ-1: The I2RS interface SHOULD support user subscriptions
	architecture does not include multi-message atomicity and rollback		to data with the following parameters: push of data synchronously
	mechanisms, but suggests an I2RS client may inidicate one of the		or asynchronously via registered subscriptions.
	following error handling techniques for a given message sent to the
	I2RS client:
	1. Perform all or none: All operations succeed or none of them will		o PubSSub-REQ-2: Real time for notifications SHOULD BEdefined
	be applied. This useful when there are mutual dependencies.		defined by the data models.
	2. Perform until error: Operations are applied in order, and when		o PubSub-REQ-3: Security of the pub/sub data stream SHOULD be able
	error occurs the processing stops. This is useful when		to be model dependent.
	dependencies exist between multiple-message operations, and order
	is important.
	3. Perform all storing errors: Perform all actions storing error		o PubSub-REQ-4: The Pub/Sub mechanism SHOULD allow subscription to
	indications for errors. This method can be used when there are		critical Node Events. Examples of critical node events are BGP
	no dependencies between operations, and the client wants to sort		peers down or ISIS protocol overload bits.
	it out.
	None of these three cases insert known errors into the I2RS ephemeral		o PubSub-REQ-5:I2RS telemetry data for certain protocols (E.g. BGP)
	datastore.		will require a hierarchy of filters or XPATHs. The I2RS protocol
			design MUST balance security against the throughput of the
			telemetry data.
	RESTCONF does an atomic action within a http session, and NETCONF has		o PubSub-REQ-6: I2RS Filters SHOULD be able to be dynamic.
	atomic actions within a commit. These features may be used to
	perform these features.
	I2RS processing is dependent on the I2RS model. The I2RS model must		o Pub-Sub-REQ-7: I2rs protocol MUST be able to allow I2RS agent to
	consider the dependencies within multiple operations work within a		set limits on the data models it will support for pub/sub and
	model.		within data models to support knobs for maximum frequency or
			resolution of pub/sub data.
	9. Previously Considered Ideas		4. Previously Considered Ideas
	9.1. A Separate Ephemeral Datastore		4.1. A Separate Ephemeral Datastore
	The primary advantage of a fully separate datastore is that the		The primary advantage of a fully separate datastore is that the
	semantics of its contents are always clearly ephemeral. It also		semantics of its contents are always clearly ephemeral. It also
	provides strong segregation of I2RS configuration and operational		provides strong segregation of I2RS configuration and operational
	state from the rest of the system within the network element.		state from the rest of the system within the network element.
	The most obvious disadvantage of such a fully separate datastore is		The most obvious disadvantage of such a fully separate datastore is
	that interaction with the network element's operational or		that interaction with the network element's operational or
	configuration state becomes significantly more difficult. As an		configuration state becomes significantly more difficult. As an
	example, a BGP I2RS use case would be the dynamic instantiation of a		example, a BGP I2RS use case would be the dynamic instantiation of a
	skipping to change at page 11, line 13		skipping to change at page 8, line 48
	groupings from an IETF-standardized BGP module in such an I2RS		groupings from an IETF-standardized BGP module in such an I2RS
	ephemeral datastore's modules, one cannot currently reference state		ephemeral datastore's modules, one cannot currently reference state
	from one datastore to anothe		from one datastore to anothe
	For example, XPath queries are done in the context document of the		For example, XPath queries are done in the context document of the
	datastore in question and thus it is impossible for an I2RS model to		datastore in question and thus it is impossible for an I2RS model to
	fulfil a "must" or "when" requirement in the BGP module in the		fulfil a "must" or "when" requirement in the BGP module in the
	standard data stores. To implement such a mechanism would require		standard data stores. To implement such a mechanism would require
	appropriate semantics for XPath.		appropriate semantics for XPath.
	9.2. Panes of Glass/Overlay		4.2. Panes of Glass/Overlay
	I2RS ephemeral configuration state is generally expected to be		I2RS ephemeral configuration state is generally expected to be
	disjoint from persistent configuration. In some cases, extending		disjoint from persistent configuration. In some cases, extending
	persistent configuration with ephemeral attributes is expected to be		persistent configuration with ephemeral attributes is expected to be
	useful. A case that is considered potentially useful but problematic		useful. A case that is considered potentially useful but problematic
	was explored was the ability to "overlay" persistent configuration		was explored was the ability to "overlay" persistent configuration
	with ephemeral configuration.		with ephemeral configuration.
	In this overlay scenario, persistent configuration that was not		In this overlay scenario, persistent configuration that was not
	shadowed by ephemeral configuration could be "read through".		shadowed by ephemeral configuration could be "read through".
	There were two perceived disadvantages to this mechanism:		There were two perceived disadvantages to this mechanism:
	The general complexity with managing the overlay mechanism itself.		The general complexity with managing the overlay mechanism itself.
	Consistency issues with validation should the ephemeral state be		Consistency issues with validation should the ephemeral state be
	lost, perhaps on reboot. In such a case, the previously shadowed		lost, perhaps on reboot. In such a case, the previously shadowed
	persistent state may no longer validate.		persistent state may no longer validate.
	10. Actions Required to Implement this Draft		5. IANA Considerations
	o Draft for adding "config ephemeral" to YANG.
	o Draft defining NETCONF changes including capability, RPC operation
	changes and support of secondary identity, RPC changes to support
	priority.
	o I2RS draft to define meta-data for priority and secondary-
	identity.
	11. IANA Considerations
	TBD.		There are no IANA requirements for this document.
	12. Security Considerations		6. Security Considerations
	TBD.		The security requirements for the I2RS protocol are covered in
			[I-D.hares-i2rs-auth-trans] document.
	13. Acknowledgements		7. Acknowledgements
	This document is an attempt to distill lengthy conversations on the		This document is an attempt to distill lengthy conversations on the
	I2RS mailing list for an architecture that was for a long period of		I2RS mailing list for an architecture that was for a long period of
	time a moving target. Some individuals in particular warrant		time a moving target. Some individuals in particular warrant
	specific mention for their extensive help in providing the basis for		specific mention for their extensive help in providing the basis for
	this document:		this document:
	o Alia Atlas		o Alia Atlas
	o Andy Bierman		o Andy Bierman
	skipping to change at page 12, line 32		skipping to change at page 10, line 4
	o Dean Bogdanavich		o Dean Bogdanavich
	o Rex Fernando		o Rex Fernando
	o Joel Halpern		o Joel Halpern
	o Thomas Nadeau		o Thomas Nadeau
	o Juergen Schoenwaelder		o Juergen Schoenwaelder
	o Kent Watsen		o Kent Watsen
	14. References		8. References
	14.1. Normative References:		8.1. Normative References:
			[I-D.hares-i2rs-auth-trans]
			Hares, S., Migault, D., and J. Halpern, "I2RS Security
			Related Requirements", draft-hares-i2rs-auth-trans-05
			(work in progress), August 2015.
	[I-D.ietf-i2rs-architecture]		[I-D.ietf-i2rs-architecture]
	Atlas, A., Halpern, J., Hares, S., Ward, D., and T.		Atlas, A., Halpern, J., Hares, S., Ward, D., and T.
	Nadeau, "An Architecture for the Interface to the Routing		Nadeau, "An Architecture for the Interface to the Routing
	System", draft-ietf-i2rs-architecture-09 (work in		System", draft-ietf-i2rs-architecture-09 (work in
	progress), March 2015.		progress), March 2015.
			[I-D.ietf-i2rs-pub-sub-requirements]
			Voit, E., Clemm, A., and A. Prieto, "Requirements for
			Subscription to YANG Datastores", draft-ietf-i2rs-pub-sub-
			requirements-02 (work in progress), March 2015.
	[I-D.ietf-i2rs-rib-info-model]		[I-D.ietf-i2rs-rib-info-model]
	Bahadur, N., Folkes, R., Kini, S., and J. Medved, "Routing		Bahadur, N., Folkes, R., Kini, S., and J. Medved, "Routing
	Information Base Info Model", draft-ietf-i2rs-rib-info-		Information Base Info Model", draft-ietf-i2rs-rib-info-
	model-06 (work in progress), March 2015.		model-06 (work in progress), March 2015.
	[I-D.ietf-i2rs-traceability]		[I-D.ietf-i2rs-traceability]
	Clarke, J., Salgueiro, G., and C. Pignataro, "Interface to		Clarke, J., Salgueiro, G., and C. Pignataro, "Interface to
	the Routing System (I2RS) Traceability: Framework and		the Routing System (I2RS) Traceability: Framework and
	Information Model", draft-ietf-i2rs-traceability-03 (work		Information Model", draft-ietf-i2rs-traceability-03 (work
	in progress), May 2015.		in progress), May 2015.
	[I-D.ietf-netmod-yang-metadata]		[I-D.ietf-netmod-yang-metadata]
	Lhotka, L., "Defining and Using Metadata with YANG",		Lhotka, L., "Defining and Using Metadata with YANG",
	draft-ietf-netmod-yang-metadata-01 (work in progress),		draft-ietf-netmod-yang-metadata-01 (work in progress),
	June 2015.		June 2015.
	14.2. Informative References		8.2. Informative References
	[I-D.bierman-netconf-restconf]		[I-D.ietf-netconf-restconf]
	Bierman, A., Bjorklund, M., Watsen, K., and R. Fernando,		Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
	"RESTCONF Protocol", draft-bierman-netconf-restconf-04		Protocol", draft-ietf-netconf-restconf-07 (work in
	(work in progress), February 2014.		progress), July 2015.
	[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate		[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
	Requirement Levels", BCP 14, RFC 2119, March 1997.		Requirement Levels", BCP 14, RFC 2119,
			DOI 10.17487/RFC2119, March 1997,
			<http://www.rfc-editor.org/info/rfc2119>.
	[RFC6020] Bjorklund, M., "YANG - A Data Modeling Language for the		[RFC6020] Bjorklund, M., Ed., "YANG - A Data Modeling Language for
	Network Configuration Protocol (NETCONF)", RFC 6020,		the Network Configuration Protocol (NETCONF)", RFC 6020,
	October 2010.		DOI 10.17487/RFC6020, October 2010,
			<http://www.rfc-editor.org/info/rfc6020>.
	[RFC6241] Enns, R., Bjorklund, M., Schoenwaelder, J., and A.		[RFC6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
	Bierman, "Network Configuration Protocol (NETCONF)", RFC		and A. Bierman, Ed., "Network Configuration Protocol
	6241, June 2011.		(NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
			<http://www.rfc-editor.org/info/rfc6241>.
	[RFC6536] Bierman, A. and M. Bjorklund, "Network Configuration		[RFC6536] Bierman, A. and M. Bjorklund, "Network Configuration
	Protocol (NETCONF) Access Control Model", RFC 6536, March		Protocol (NETCONF) Access Control Model", RFC 6536,
	2012.		DOI 10.17487/RFC6536, March 2012,
			<http://www.rfc-editor.org/info/rfc6536>.
	Authors' Addresses		Authors' Addresses
	Jeff Haas		Jeff Haas
	Juniper		Juniper
	Email: jhaas@juniper.net		Email: jhaas@juniper.net
	Susan Hares		Susan Hares
	Huawei		Huawei
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