NETCONF E. Voit
Internet-Draft Cisco Systems
Intended status: Standards Track A. Clemm
Expires: July 28, 2018 Huawei
A. Gonzalez Prieto
VMWare
E. Nilsen-Nygaard
A. Tripathy
Cisco Systems
January 24, 2018
Custom Subscription to Event Streams
draft-ietf-netconf-subscribed-notifications-09
Abstract
This document defines capabilities and operations for the customized
establishment of subscriptions upon a publisher's event streams.
Also defined are delivery mechanisms for instances of the resulting
notification messages. Effectively this allows a subscriber to
request and receive a continuous, custom feed of publisher generated
information.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on July 28, 2018.
Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
Voit, et al. Expires July 28, 2018 [Page 1]
Internet-Draft Subscribed Notifications January 2018
(https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Motivation . . . . . . . . . . . . . . . . . . . . . . . 3
1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
1.3. Solution Overview . . . . . . . . . . . . . . . . . . . . 4
1.4. Relationship to RFC-5277 . . . . . . . . . . . . . . . . 6
2. Solution . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.1. Event Streams . . . . . . . . . . . . . . . . . . . . . . 6
2.2. Event Stream Filters . . . . . . . . . . . . . . . . . . 7
2.3. QoS . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.4. Dynamic Subscriptions . . . . . . . . . . . . . . . . . . 8
2.5. Configured Subscriptions . . . . . . . . . . . . . . . . 14
2.6. Event Record Delivery . . . . . . . . . . . . . . . . . . 19
2.7. Subscription State Notifications . . . . . . . . . . . . 20
2.8. Subscription Monitoring . . . . . . . . . . . . . . . . . 24
2.9. Advertisement . . . . . . . . . . . . . . . . . . . . . . 24
3. YANG Data Model Trees . . . . . . . . . . . . . . . . . . . . 24
3.1. Event Streams Container . . . . . . . . . . . . . . . . . 25
3.2. Event Stream Filters Container . . . . . . . . . . . . . 25
3.3. Subscriptions Container . . . . . . . . . . . . . . . . . 25
4. Data Model . . . . . . . . . . . . . . . . . . . . . . . . . 26
5. Considerations . . . . . . . . . . . . . . . . . . . . . . . 51
5.1. Implementation Considerations . . . . . . . . . . . . . . 51
5.2. IANA Considerations . . . . . . . . . . . . . . . . . . . 52
5.3. Security Considerations . . . . . . . . . . . . . . . . . 52
6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 53
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 54
7.1. Normative References . . . . . . . . . . . . . . . . . . 54
7.2. Informative References . . . . . . . . . . . . . . . . . 55
Appendix A. Changes between revisions . . . . . . . . . . . . . 55
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 59
1. Introduction
This document defines capabilities and operations for the customized
establishment of subscriptions upon system generated event streams.
Effectively this enables a "subscribe then publish" capability where
the customized information needs of each target receiver are
understood by the publisher before subscribed event records are
Voit, et al. Expires July 28, 2018 [Page 2]
Internet-Draft Subscribed Notifications January 2018
marshaled and pushed. The receiver then gets a continuous, custom
feed of publisher generated information.
While the functionality defined in this document is transport-
agnostic, protocols like NETCONF [RFC6241] or RESTCONF [RFC8040] can
be used to configure or dynamically signal subscriptions, and there
are bindings defined for subscribed event record delivery for NETCONF
within [I-D.draft-ietf-netconf-netconf-event-notifications], and for
HTTP2 or HTTP1.1 within [I-D.draft-ietf-netconf-restconf-notif].
1.1. Motivation
There are various [RFC5277] limitations, many of which have been
exposed in [RFC7923] which needed to be solved. Key capabilities
supported by this document include:
o multiple subscriptions on a single transport session
o support for dynamic and statically configured subscriptions
o modification of an existing subscription
o operational counters and instrumentation
o negotiation of subscription parameters (through the use of hints
returned as part of declined subscription requests)
o state change notifications (e.g., publisher driven suspension,
parameter modification)
o independence from transport protocol
1.2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
Configured subscription: A subscription installed via a configuration
interface which persists across reboots.
Dynamic subscription: A subscription agreed between subscriber and
publisher created via an establish-subscription RPC.
Event: An occurrence of something that may be of interest. (e.g., a
configuration change, a fault, a change in status, crossing a
threshold, or an external input to the system.)
Voit, et al. Expires July 28, 2018 [Page 3]
Internet-Draft Subscribed Notifications January 2018
Event record: A set of information detailing an event.
NACM: NETCONF Access Control Model.
Notification message: A set of transport encapsulated information
intended for a receiver indicating that one or more event(s) have
occurred. A notification message may bundle multiple event records.
This includes the bundling multiple, independent RFC 7950 YANG
notifications.
Publisher: An entity responsible for streaming notification messages
per the terms of a Subscription.
Receiver: A target to which a publisher pushes subscribed event
records. For dynamic subscriptions, the receiver and subscriber are
the same entity.
Stream (also referred to as "event stream"): A continuous ordered set
of events aggregated under some context.
Stream filter: Evaluation criteria which may be applied against event
records within a stream. Event records pass the filter when
specified criteria are met.
Subscribed event records: Event records which have met the terms of
the subscription. This include terms (such as security checks)
enforced by the publisher.
Subscriber: An entity able to request and negotiate a contract for
the generation and push of event records from a publisher.
Subscription: A contract with a publisher, stipulating which
information one or more receivers wish to have pushed from the
publisher without the need for further solicitation.
1.3. Solution Overview
This document describes a transport agnostic mechanism for
subscribing to and receiving content from a stream instantiated
within a publisher. This mechanism is through the use of a
subscription.
Two types of subscriptions are supported:
1. Dynamic subscriptions, where a subscriber initiates a
subscription negotiation with a publisher via RPC. If the
publisher wants to serve this request, it accepts it, and then
starts pushing notification messages. If the publisher does not
Voit, et al. Expires July 28, 2018 [Page 4]
Internet-Draft Subscribed Notifications January 2018
wish to serve it as requested, then an error response is
returned. This response MAY include hints at subscription
parameters which would have been accepted.
2. Configured subscriptions, which allow the management of
subscriptions via a configuration interface so that a publisher
can send notification messages to configured receiver(s).
Support for this capability is optional.
Additional characteristics differentiating configured from dynamic
subscriptions include:
o The lifetime of a dynamic subscription is bounded by the transport
session used to establish it. For connection-oriented stateful
transport like NETCONF, the loss of the transport session will
result in the immediate termination of any associated dynamic
subscriptions. For connectionless or stateless transports like
HTTP, a lack of receipt acknowledgment of a sequential set of
notification messages and/or keep-alives can be used to trigger a
termination of a dynamic subscription. Contrast this to the
lifetime of a configured subscription. This lifetime is driven by
relevant configuration being present within the publisher's
running configuration. Being tied to configuration operations
implies configured subscriptions can be configured to persist
across reboots, and implies a configured subscription can persist
even when its publisher is fully disconnected from any network.
o Configured subscriptions can be modified by any configuration
client with write permission on the configuration of the
subscription. Dynamic subscriptions can only be modified via an
RPC request made by the original subscriber.
Note that there is no mixing-and-matching of dynamic and configured
operations on a single subscription. Specifically, a configured
subscription cannot be modified or deleted using RPCs defined in this
document. Similarly, a subscription established via RPC cannot be
modified through configuration operations. Also note that transport
specific transport drafts based on this specification MUST detail the
life cycles of both dynamic and configured subscriptions.
The publisher MAY decide to terminate a dynamic subscription at any
time. Similarly, it MAY decide to temporarily suspend the sending of
notification messages for any dynamic subscription, or for one or
more receivers of a configured subscription. Such termination or
suspension is driven by internal considerations of the publisher.
Voit, et al. Expires July 28, 2018 [Page 5]
Internet-Draft Subscribed Notifications January 2018
1.4. Relationship to RFC-5277
This document is intended to provide a superset of the subscription
capabilities initially defined within [RFC5277]. Especially when
extending an existing [RFC5277] implementation, it is important to
understand what has been reused and what has been replaced. Key
relationships between these two documents include:
o the data model in this document replaces the data model in
[RFC5277].
o the RPC operations in this draft replaces the symmetrical
operations of [RFC5277], section 4.
o the one way operation of [RFC5277] is still used. However this
operation will no longer be required with the availability of
[I.D.draft-ietf-netconf-notification-messages].
o the definition and contents of the NETCONF stream are identical
between this document and [RFC5277].
o a publisher MAY implement both the data model and RPCs defined in
[RFC5277] and this new document concurrently, in order to support
old clients. However the use of both alternatives on a single
transport session is prohibited.
2. Solution
2.1. Event Streams
An event stream is a named entity on a publisher which exposes a
continuously updating set of event records. Each event stream is
available for subscription. It is out of the scope of this document
to identify a) how streams are defined, b) how event records are
defined/generated, and c) how event records are assigned to streams.
There is only one reserved event stream within this document:
NETCONF. The NETCONF event stream contains all NETCONF XML event
record information supported by the publisher, except for where it
has been explicitly indicated that this the event record MUST be
excluded from the NETCONF stream. The NETCONF stream will include
individual YANG notifications as per [RFC7950] section 7.16. Each of
these YANG notifications will be treated a distinct event record.
Beyond the NETCONF stream, implementations are free to add additional
event streams.
As event records are created by a system, they may be assigned to one
or more streams. The event record is distributed to subscription's
Voit, et al. Expires July 28, 2018 [Page 6]
Internet-Draft Subscribed Notifications January 2018
receiver(s) where: (1) a subscription includes the identified stream,
and (2) subscription filtering does not exclude the event record from
that receiver.
If access control permissions are in use to secure publisher content,
then for event records to be sent to a receiver, that receiver MUST
be allowed access to all the event records on the stream. If
subscriber permissions change during the lifecycle of a subscription,
then the subscription MUST be continued or terminated accordingly.
2.2. Event Stream Filters
This document defines an extensible filtering mechanism. Two
optional stream filtering syntaxes supported are [XPATH] and subtree
[RFC6241]. A filter always removes a complete event record; a subset
of information is never stripped from an event record.
If no stream filter is provided within a subscription, all event
records on a stream are to be sent.
2.3. QoS
This document provides an optional feature describing QoS parameters.
These parameters indicate the treatment of a subscription relative to
other traffic between publisher and receiver. Included are:
o A "dscp" QoS marking to differentiate transport QoS behavior.
Where provided, this marking MUST be stamped on notification
messages.
o A "weighting" so that bandwidth proportional to this weighting can
be allocated to this subscription relative to other subscriptions
destined for that receiver.
o a "dependency" upon another subscription. Notification messages
MUST NOT be sent prior to other notification messages containing
update record(s) for the referenced subscription.
A subscription's weighting MUST work identically to stream dependency
weighting as described within RFC 7540, section 5.3.2.
A subscription's dependency MUST work identically to stream
dependency as described within [RFC7540], sections 5.3.1, 5.3.3, and
5.3.4. If a dependency is attempted via an RPC, but the referenced
subscription does not exist, the dependency will be silently removed.
Voit, et al. Expires July 28, 2018 [Page 7]
Internet-Draft Subscribed Notifications January 2018
2.4. Dynamic Subscriptions
Dynamic subscriptions are managed via RPC, and are made against
targets located within the publisher. These RPCs have been designed
extensibly so that they may be augmented for subscription targets
beyond event streams.
2.4.1. Dynamic Subscription State Model
Below is the publisher's state machine for a dynamic subscription.
It is important to note that such a subscription doesn't exist at the
publisher until an "establish-subscription" RPC is accepted. The
mere request by a subscriber to establish a subscription is
insufficient for that asserted subscription to be externally visible.
States that are reflected in the YANG model appear in upper-case
letters; in addition, start and end states are depicted to reflect
subscription creation and deletion events.
.........
: start :
:.......:
|
establish-subscription
|
| .------modify-subscription-------.
v v '
.-----------. .-----------.
.--------. | receiver |-subscription-suspended->| receiver |
modify- '| ACTIVE | | SUSPENDED |
subscription | |<--subscription-resumed--| |
---------->'-----------' '-----------'
| |
delete/kill-subscription delete/kill-
| subscription
v |
......... |
: end :<-------------------------------'
:.......:
Receiver state for a dynamic subscription
Of interest in this state machine are the following:
o Successful establish or modify RPCs put the subscription into an
active state.
o Failed modify RPCs will leave the subscription in its previous
state, with no visible change to any streaming updates.
Voit, et al. Expires July 28, 2018 [Page 8]
Internet-Draft Subscribed Notifications January 2018
o A delete or kill RPC will end the subscription.
o Suspend and resume state changes are driven by internal process
and prioritization. There are no direct controls over suspend and
resume other than modifying a subscription
2.4.2. Establishing a Subscription
The "establish-subscription" operation allows a subscriber to request
the creation of a subscription via RPC. It MUST be possible to
support multiple establish subscription RPC requests made within the
same transport session.
The input parameters of the operation are:
o A stream name which identifies the targeted stream of events
against which the subscription is applied.
o A stream filter which may reduce the set of event records pushed.
o An optional encoding for the event records pushed. Note: If no
encoding is included, the encoding of the RPC MUST be used.
o An optional stop time for the subscription. If no stop-time is
present, notification messages will continue to be sent until the
subscription is terminated.
o An optional start time for the subscription. If the start-time is
in the past, it indicates that this subscription is requesting a
replay of previously generated information from the event stream.
For more on replay, see Section 2.4.2.1.
If the publisher can satisfy the "establish-subscription" request, it
provides an identifier for the subscription, and immediately starts
streaming notification messages.
Voit, et al. Expires July 28, 2018 [Page 9]
Internet-Draft Subscribed Notifications January 2018
+---x establish-subscription
+---w input
| +---w encoding? encoding
| +---w (target)
| | +--:(stream)
| | +---w (stream-filter)?
| | | +--:(by-reference)
| | | | +---w stream-filter-ref stream-filter-ref
| | | +--:(within-subscription)
| | | +---w (filter-spec)?
| | | +--:(stream-subtree-filter)
| | | | +---w stream-subtree-filter? {subtree}?
| | | +--:(stream-xpath-filter)
| | | +---w stream-xpath-filter?
| | | yang:xpath1.0 {xpath}?
| | +---w stream? stream-ref
| | +---w replay-start-time? yang:date-and-time {replay}?
| +---w stop-time? yang:date-and-time
| +---w dscp? inet:dscp {qos}?
| +---w weighting? uint8 {qos}?
| +---w dependency? sn:subscription-id {qos}?
+--ro output
+--ro identifier subscription-id
Figure 1: establish-subscription RPC
A publisher MAY reject this RPC for many reasons as described in
Section 2.4.6. The contents of the resulting RPC error response MAY
include one or more hints on alternative inputs which would have
resulted in a successfully established subscription. Any such hints
MUST be transported within a yang-data "establish-subscription-error-
stream" container included within the RPC error response.
yang-data establish-subscription-error-stream
+--ro establish-subscription-error-stream
+--ro reason? identityref
+--ro filter-failure-hint? string
+--ro replay-start-time-hint? yang:date-and-time
Figure 2: establish-subscription RPC yang-data
2.4.2.1. Replay Subscription
Replay provides the ability to establish a subscription which is also
capable of passing recently generated event records. In other words,
as the subscription initializes itself, it sends any previously
generated content from within target event stream which meets the
filter and timeframe criteria. These historical event records would
Voit, et al. Expires July 28, 2018 [Page 10]
Internet-Draft Subscribed Notifications January 2018
then be followed by event records generated after the subscription
has been established. All event records will be delivered in the
order generated.
Replay is an optional feature which is dependent on an event stream
supporting some form of logging. Replay puts no restrictions on the
size or form of the log, or where it resides within the device.
The inclusion of a replay-start-time within an "establish-
subscription" RPC indicates a replay request. If the "replay-start-
time" contains a value that is earlier than content stored within the
publisher's replay buffer, then the subscription MUST be rejected,
and the leaf "replay-start-time-hint" MUST be set in the reply.
If a "stop-time" parameter is included, it MAY also be earlier than
the current time and MUST be later than the "replay-start-time". The
publisher MUST NOT accept a "replay-start-time" for a future time.
If the "replay-start-time" is later than any information stored in
the replay buffer, then the publisher MUST send a "replay-completed"
notification immediately after the "subscription-started"
notification.
If a stream supports replay, the "replay-support" leaf is present in
the "/streams/stream" list entry for the stream. An event stream
that does support replay is not expected to have an unlimited supply
of saved notifications available to accommodate any given replay
request. To assess the availability of replay, subscribers can
perform a get on "replay-log-creation-time" and "replay-log-aged-
time". See Figure 10 for the tree describing these elements. The
actual size of the replay log at any given time is a publisher
specific matter. Control parameters for the replay log are outside
the scope of this document.
2.4.3. Modifying a Subscription
The "modify-subscription" operation permits changing the terms of an
existing dynamic subscription previously established on that
transport session via "establish-subscription". Dynamic
subscriptions can be modified one or multiple times. If the
publisher accepts the requested modifications, it acknowledges
success to the subscriber, then immediately starts sending event
records based on the new terms.
Dynamic subscriptions established via RPC can only be modified via
RPC using the same transport session used to establish that
subscription. Subscriptions created by configuration operations
cannot be modified via this RPC.
Voit, et al. Expires July 28, 2018 [Page 11]
Internet-Draft Subscribed Notifications January 2018
+---x modify-subscription
+---w input
+---w identifier? subscription-id
+---w (target)
| +--:(stream)
| +---w (stream-filter)?
| +--:(by-reference)
| | +---w stream-filter-ref stream-filter-ref
| +--:(within-subscription)
| +---w (filter-spec)?
| +--:(stream-subtree-filter)
| | +---w stream-subtree-filter? {subtree}?
| +--:(stream-xpath-filter)
| +---w stream-xpath-filter?
| yang:xpath1.0 {xpath}?
+---w stop-time? yang:date-and-time
Figure 3: modify-subscription RPC
If the publisher accepts the requested modifications on a currently
suspended subscription, the subscription will immediately be resumed
(i.e., the modified subscription is returned to an active state.)
The publisher MAY immediately suspend this newly modified
subscription through the "subscription-suspended" notification before
any event records are sent.
If the publisher rejects the RPC request, the subscription remains as
prior to the request. That is, the request has no impact whatsoever.
Rejection of the RPC for any reason is indicated by via RPC error as
described in Section 2.4.6. The contents of a such a rejected RPC
MAY include one or more hints on alternative inputs which would have
resulted in a successfully modified subscription. These hints MUST
be transported within a yang-data "modify-subscription-error-stream"
container inserted into the RPC error response.
yang-data modify-subscription-error-stream
+--ro modify-subscription-error-stream
+--ro reason? identityref
+--ro filter-failure-hint? string
Figure 4: modify-subscription RPC yang-data
2.4.4. Deleting a Subscription
The "delete-subscription" operation permits canceling an existing
subscription previously established on that transport session. If
the publisher accepts the request, and the publisher has indicated
success, the publisher MUST NOT send any more notification messages
Voit, et al. Expires July 28, 2018 [Page 12]
Internet-Draft Subscribed Notifications January 2018
for this subscription. If the publisher rejects the request, the
request has no impact whatsoever on any subscription.
+---x delete-subscription
+---w input
+---w identifier subscription-id
Figure 5: delete-subscription RPC
Dynamic subscriptions can only be deleted via this RPC using the same
transport session previously used for subscription establishment.
Configured subscriptions cannot be deleted using RPCs.
2.4.5. Killing a Subscription
The "kill-subscription" operation permits an operator to end a
dynamic subscription which is not associated with the transport
session used for the RPC. This operation MUST be secured so that
only connections with sufficiently privileged access rights are able
to invoke this RPC. A publisher MUST terminate any dynamic
subscription identified by RPC request. An operator may find
subscription identifiers which may be used with "kill-subscription"
by searching for the IP address of a receiver within
"subscriptions\subscription\receivers\receiver\address".
Configured subscriptions cannot be killed using this RPC. Instead,
configured subscriptions are deleted as part of regular configuration
operations. Publishers MUST reject any RPC attempt to kill a
configured subscription.
The tree structure of "kill-subscription" is almost identical to
"delete-subscription", with only the name of the RPC and yang-data
changing.
2.4.6. RPC Failures
Whenever an RPC is unsuccessful, the publisher returns relevant error
codes as part of the RPC error response. RPC error codes returned
include both existing transport layer RPC error codes, such as those
seen with NETCONF in [RFC6241] Appendix A, as well as subscription
specific errors such as those defined within this document's YANG
model. As a result of this mixture, how subscription errors are
encoded within an RPC error response is transport dependent.
There are elements of the RPC error mechanism which are transport
independent. Specifically, references to specific identities within
the YANG model MUST be returned as part of the error responses
Voit, et al. Expires July 28, 2018 [Page 13]
Internet-Draft Subscribed Notifications January 2018
resulting from failed attempts at event stream subscription.
Following are valid errors per RPC:
establish-subscription modify-subscription
---------------------- -------------------
dscp-unavailable filter-unsupported
filter-unsupported insufficient-resources
history-unavailable no-such-subscription
insufficient-resources
replay-unsupported
delete-subscription kill-subscription
---------------------- ----------------------
no-such-subscription no-such-subscription
There is one final set of transport independent RPC error elements
included in the YANG model. These are the following three yang-data
structures for failed event stream subscriptions:
1. yang-data establish-subscription-error-stream: This MUST be
returned if an RPC error reason has not been placed elsewhere
within the transport portion of a failed "establish-subscription"
RPC response. This MUST be sent if hints on how to overcome the
RPC error are included.
2. yang-data modify-subscription-error-stream: This MUST be returned
if an RPC error reason has not been placed elsewhere within the
transport portion of a failed "modify-subscription" RPC response.
This MUST be sent if hints on how to overcome the RPC error are
included.
3. yang-data delete-subscription-error: This MUST be returned if an
RPC error reason has not been placed elsewhere within the
transport portion of a failed "delete-subscription" or "kill-
subscription" RPC response.
2.5. Configured Subscriptions
A configured subscription is a subscription installed via a
configuration interface. Configured subscriptions may be modified by
any configuration client with the proper permissions. Subscriptions
can be modified or terminated via the configuration interface at any
point of their lifetime.
Configured subscriptions have several characteristics distinguishing
them from dynamic subscriptions:
o persistence across reboots,
Voit, et al. Expires July 28, 2018 [Page 14]
Internet-Draft Subscribed Notifications January 2018
o persistence even when transport is unavailable, and
o an ability to send notification messages to more than one receiver
(note that the publisher does not provide information to a
receiver about other receivers.)
Supporting configured subscriptions is optional and advertised using
the "configured" feature.
In addition to subscription parameters available to dynamic
subscriptions as described in Section 2.4.2, the following additional
parameters are also available to configured subscriptions:
o One or more receiver IP addresses (and corresponding ports)
intended as the destination for notification messages.
o Optional parameters to identify an egress interface, a host IP
address, a VRF (as defined by the network instance name within
[I-D.draft-ietf-rtgwg-ni-model]), or an IP address plus VRF out of
which notification messages are to be pushed from the publisher.
Where any of this info is not explicitly included, or where just
the VRF is provided, notification messages MUST egress the
publisher's default interface towards that receiver.
2.5.1. Configured Subscription State Model
Below is the state machine for a configured subscription. States
that are reflected in the YANG model appear in upper-case letters; in
addition, start and end states are depicted to reflect configured
subscription creation and deletion events. The creation or
modification of a configured subscription initiates a publisher
evaluation to determine if the subscription is valid or invalid. The
publisher uses its own criteria in making this determination. If
valid, the subscription becomes operational.
Voit, et al. Expires July 28, 2018 [Page 15]
Internet-Draft Subscribed Notifications January 2018
.........
: start :-.
:.......: |
create .---modify-----.----------------------------------.
| | | |
V V .-------. ....... .---------.
.----[evaluate]--no--->|INVALID|-delete->: end :<-delete-|CONCLUDED|
| '-------' :.....: '---------'
|----[evaluate]--no-. ^ ^ ^
| ^ | | | |
yes | '->unsupportable delete stop-time
| modify (subscription- (subscription- (subscription-
| | terminated) terminated) concluded)
| | | | |
| .---------------------------------------------------------------.
'-->| VALID |
'---------------------------------------------------------------'
State model for a configured subscription.
A valid subscription may become invalid on one of two ways. First,
it may be modified in a way which fails a re-evaluation. Second, the
publisher itself might itself determine that the subscription in no
longer supportable. In either case, a "subscription-terminated"
notification is sent to any active or suspended receivers. A valid
subscription may also transition to a concluded state if a configured
stop time has been reached. In this case, a "subscription-concluded"
is sent to any active or suspended receivers.
During any times a subscription is considered valid, a publisher will
attempt to connect with all configured receivers and deliver
notification messages. Below is the state machine for each receiver
of a configured subscription. This receiver state machine itself is
fully contained within the state machine of the configured
subscription, and is only relevant when the configured subscription
itself is determined to be valid.
Voit, et al. Expires July 28, 2018 [Page 16]
Internet-Draft Subscribed Notifications January 2018
.----------------------------------------------------------------.
| VALID |
| .----------. .--------. |
| | receiver |------------------timeout->|receiver| |
| |CONNECTING|<------------------reset---|TIMEOUT | |
| | |<-transport---. '--------' |
| '----------' loss,reset | |
| | | | |
| (subscription | | |
| started) .--------. | .---------. |
| '----->| | '----------------------| | |
| |receiver|-(subscription-suspended)-->|receiver | |
|(subscription-| ACTIVE | |SUSPENDED| |
| modified) | |<-(subscription-resumed,----| | |
| '---->'--------' subscription-modified) '---------' |
'----------------------------------------------------------------'
Receiver state for a configured subscription
When a subscription first becomes valid, the operational state of
each receiver is initialized to connecting. Individual are receivers
are moved to an active state when a "subscription-started" state
change notification is successfully passed to that receiver.
Configured receivers remain active if transport connectivity is not
lost, and event records are not being dropped due to a publisher
buffer overflow. A configured subscription's receiver MUST be moved
to connecting if transport connectivity is lost, or if the receiver
is reset via configuration operations.
A configured subscription's receiver MUST be moved to a suspended
state if there is transport connectivity between the publisher and
receiver, but notification messages are not being generated for that
receiver. A configured subscription receiver MUST be returned to an
active state from the suspended state when notification messages are
again being generated and a receiver has successfully been sent a
"subscription-resumed" or a "subscription-modified".
Modification of a configured subscription is possible at any time. A
"subscription-modified" state change notification will be sent to all
active receivers, immediately followed by notification messages
conforming to the new parameters. Suspended receivers will also be
informed of the modification. However this notification will await
the end of the suspension for that receiver.
The mechanisms described above is mirrored in the RPCs and YANG
notifications within the document. It should be noted that these
RPCs and YANG notifications have been designed to be extensible and
Voit, et al. Expires July 28, 2018 [Page 17]
Internet-Draft Subscribed Notifications January 2018
allow subscriptions into targets other than event streams.
[I-D.ietf-netconf-yang-push] provides an example of such an
extension.
2.5.2. Creating a Configured Subscription
Configured subscriptions are established using configuration
operations against the top-level subtree "subscription-config".
There are two key differences between the new RPCs defined in this
document and configuration operations for subscription creation.
Firstly, configuration operations install a subscription without
question, while the RPCs are designed to the support negotiation and
rejection of requests. Secondly, while the RPCs mandate that the
subscriber establishing the subscription is the only receiver of the
notification messages, configuration operations permit specifying
receivers independent of any tracked subscriber. Because there is no
explicit association with an existing transport session,
configuration operations require additional parameters beyond those
of dynamic subscriptions to indicate receivers, and possibly whether
the notification messages need to come from a specific egress
interface on the publisher.
After a subscription is successfully created, the publisher
immediately sends a "subscription-started" state change notification
to each receiver. It is quite possible that upon configuration,
reboot, or even steady-state operations, a transport session may not
be currently available to the receiver. In this case, when there is
something to transport for an active subscription, transport specific
call-home operations will be used to establish the connection. When
transport connectivity is available, notification messages may then
be pushed.
With active configured subscriptions, it is allowable to buffer event
records even after a "subscription-started" has been sent. However
if events are lost (rather than just delayed) due to replay buffer
overflow, a new "subscription-started" must be sent. This new
"subscription-started" indicates an event record discontinuity.
To see an example at subscription creation using configuration
operations over NETCONF, see Appendix A of
[I-D.draft-ietf-netconf-netconf-event-notifications].
Note that is possible to configure replay on a configured
subscription. This capability is to allow a configured subscription
to exist on a system so that event records generated during boot can
be buffered and pushed as soon as the transport session is
established.
Voit, et al. Expires July 28, 2018 [Page 18]
Internet-Draft Subscribed Notifications January 2018
2.5.3. Modifying a Configured Subscription
Configured subscriptions can be modified using configuration
operations against the top-level subtree "subscription-config".
If the modification involves adding receivers, added receivers are
placed in the "connecting" state. If a receiver is removed, the
state change notification "subscription-terminated" is sent to that
receiver if that receiver is "active" or "suspended" .
If the modification involved changing the policies for the
subscription, the publisher sends to currently active receivers a
"subscription-modified" notification. For any suspended receivers, a
"subscription-modified" notification will be delayed until the
receiver is resumed. (Note: in this case, the "subscription-
modified" notification informs the receiver that the subscription has
been resumed, so no additional "subscription-resumed" need be sent.)
2.5.4. Deleting a Configured Subscription
Subscriptions can be deleted using configuration operations against
the top-level subtree "subscription-config".
Immediately after a subscription is successfully deleted, the
publisher sends to all receivers of that subscription a state change
notification stating the subscription has ended (i.e., "subscription-
terminated").
2.5.5. Resetting a Configured Receiver
It is possible that a configured subscription to a receiver needs to
be reset. This re-initialization may be useful in cases where a
publisher has timed out trying to reach a receiver. When such a
reset occurs, a transport session will be initiated if necessary, and
a new "subscription-started" notification will be sent.
2.6. Event Record Delivery
Whether dynamic or configured, once a subscription has been set up,
the publisher streams event records via notification messages per the
terms of the subscription. For dynamic subscriptions set up via RPC
operations, notification messages are sent over the session used to
establish the subscription. For configured subscriptions,
notification messages are sent over the connections specified by the
transport, plus receiver IP address and port configured.
A notification message is sent to a receiver when an event record is
able to traverse the specified filter criteria. This notification
Voit, et al. Expires July 28, 2018 [Page 19]
Internet-Draft Subscribed Notifications January 2018
message MUST be encoded as one-way notification element of [RFC5277],
Section 4. The following example within [RFC7950] section 7.16.3 is
an example of a compliant message:
<notification
xmlns="urn:ietf:params:xml:ns:netconf:notification:1.0">
<eventTime>2007-09-01T10:00:00Z</eventTime>
<link-failure xmlns="http://acme.example.com/system">
<if-name>so-1/2/3.0</if-name>
<if-admin-status>up</if-admin-status>
<if-oper-status>down</if-oper-status>
</link-failure>
</notification>
Figure 6: subscribed notification message
This [RFC5277] section 4 one-way operation has the drawback of not
including useful header information such as a subscription
identifier. When using this mechanism, it is left up to
implementations or augmentations to this document to determine which
event records belong to which subscription.
These drawbacks, along with other useful common headers and the
ability to bundle multiple event records together is being explored
within [I.D.draft-ietf-netconf-notification-messages]. When the
notification-messages is supported, this document will be updated to
indicate support.
2.7. Subscription State Notifications
In addition to subscribed event records, a publisher will send
subscription state notifications to indicate to receivers that an
event related to the subscription management has occurred.
Subscription state notifications are unlike other notifications which
might be found in the event stream. They cannot be filtered out, and
they are delivered only to directly impacted receiver(s) of a
subscription. The identification of subscription state notifications
is easy to separate from other notification messages through the use
of the YANG extension "subscription-state-notif". This extension
tags a notification as subscription state notification.
The complete set of subscription state notifications is described in
the following subsections.
Voit, et al. Expires July 28, 2018 [Page 20]
Internet-Draft Subscribed Notifications January 2018
2.7.1. subscription-started
This notification indicates that a configured subscription has
started, and event records may be sent. Included in this state
change notification are all the parameters of the subscription,
except for the receiver(s) addressing information and origin
information indicating where notification messages will egress the
publisher. Note that if a referenced filter from the "filters"
container has been used within the subscription, the notification
will include the contents of that referenced under the "within-
subscription" subtree.
Note that for dynamic subscriptions, no "subscription-started"
notifications are ever sent.
+---n subscription-started {configured}?
+--ro identifier subscription-id
+--ro protocol transport {configured}?
+--ro encoding encoding
+--ro (target)
| +--:(stream)
| +--ro (stream-filter)?
| | +--:(by-reference)
| | | +--ro stream-filter-ref stream-filter-ref
| | +--:(within-subscription)
| | +--ro (filter-spec)?
| | +--:(stream-subtree-filter)
| | | +--ro stream-subtree-filter? {subtree}?
| | +--:(stream-xpath-filter)
| | +--ro stream-xpath-filter? yang:xpath1.0 {xpath}?
| +--ro stream stream
| +--ro replay-start-time? yang:date-and-time {replay}?
+--ro stop-time? yang:date-and-time
+--ro dscp? inet:dscp {qos}?
+--ro weighting? uint8 {qos}?
+--ro dependency? sn:subscription-id {qos}?
Figure 7: subscription-started notification
2.7.2. subscription-modified
This notification indicates that a subscription has been modified by
configuration operations. The same parameters of "subscription-
started" are provided via this notification. As a result, the tree
structure of "subscription-modified" is almost identical to
"subscription-started", with only the name of the notification
changing.
Voit, et al. Expires July 28, 2018 [Page 21]
Internet-Draft Subscribed Notifications January 2018
A publisher most often sends this notification directly after the
modification of any configuration parameters impacting a configured
subscription. But it may also be sent at two other times.
o First, where a configured subscription has been modified during
the suspension of a receiver, the notification will be delayed
until the receiver's suspension is lifted. In this situation, the
notification indicates that the subscription has been both
modified and resumed.
o Second, for dynamic subscriptions, there is one and only one time
this notification may be sent. A "subscription-modified" state
change notifications MUST be sent if the contents of a filter
identified by a "stream-filter-ref" has changed.
2.7.3. subscription-terminated
The publisher MAY decide to terminate the pushing of subscribed event
records to a receiver. This notification indicates that no further
notification messages should be expected from the publisher. Such a
decision may be made for two types of reasons. The first type of
reason is that a subscription's referenced objects are no longer
accessible via the YANG model. Identities within the YANG model
corresponding to such a loss include: "filter-unavailable", "no-such-
subscription", and "stream-unavailable". The second reason is that a
suspended subscription has exceeded some timeout. This condition is
indicated via the identity "suspension-timeout". Publisher-driven
terminations are always notified to all receivers.
+---n subscription-terminated
+--ro identifier subscription-id
+--ro reason identityref
Figure 8: subscription-terminated notification
Note: subscribers themselves can terminate existing subscriptions
established via a "delete-subscription" RPC. In such cases, no
"subscription-terminated" state change notifications are sent.
However if a "kill-subscription" RPC is sent, or some other event
other than reaching the subscription's stop time results in the end
of a subscription, then this state change notification MUST be sent.
2.7.4. subscription-suspended
This notification indicates that a publisher has suspended the
sending of event records to a receiver, and also indicates the
possible loss of events. Suspension happens when capacity
constraints stop a publisher from serving a valid subscription. The
Voit, et al. Expires July 28, 2018 [Page 22]
Internet-Draft Subscribed Notifications January 2018
two conditions where is this possible are "insufficient-resources"
and "unsupportable-volume". No further notification will be sent
until the subscription resumes or is terminated.
The tree structure of "subscription-suspended" is almost identical to
"subscription-terminated", with only the name of the notification
changing.
2.7.5. subscription-resumed
This indicates that a previously suspended subscription has been
resumed under the unmodified terms previously in place. Subscribed
event records generated after the generation of this state change
notification will be sent.
+---n subscription-resumed
+--ro identifier subscription-id
Figure 9: subscription-resumed notification
2.7.6. subscription-completed
This notification indicates that a subscription, which includes a
"stop-time", has successfully finished passing event records upon the
reaching of that time.
The tree structure of "subscription-completed" is almost identical to
"subscription-resumed", with only the name of the notification
changing.
2.7.7. replay-completed
This notification indicates that all of the event records prior to
the current time have been sent. This includes new event records
generated since the start of the subscription. This notification
MUST NOT be sent for any other reason.
If subscription contains no "stop-time", or has a "stop-time" which
has not been reached, then after the "replay-completed" notification
has been sent, additional event records will be sent in sequence as
they arise naturally on the publisher.
The tree structure of "replay-completed" is almost identical to
"subscription-resumed", with only the name of the notification
changing.
Voit, et al. Expires July 28, 2018 [Page 23]
Internet-Draft Subscribed Notifications January 2018
2.8. Subscription Monitoring
Container "subscriptions" in the YANG module contains the state of
all known subscriptions. This includes subscriptions that were
established (and have not yet been deleted) using RPCs, as well as
subscriptions that have been configured as part of configuration.
Using the "get" operation with NETCONF, or subscribing to this
information via [I-D.ietf-netconf-yang-push] allows the state of
subscriptions and their connectivity to receivers to be monitored.
Each subscription is represented as a list element. The associated
information includes an identifier for the subscription, receiver
counter information, the state of the receiver (e.g., is currently
active or suspended), as well as the various subscription parameters
that are in effect. Leaf "configured-subscription-state" indicates
that the subscription came into being via configuration, and the
current state of the configured subscription.
Subscriptions that were established by RPC are removed from the list
once they expire (reaching stop-time) or when they are terminated.
Subscriptions that were established by configuration need to be
deleted from the configuration by a configuration editing operation
even if the stop time has been passed.
2.9. Advertisement
Publishers supporting this document MUST indicate support the YANG
model "ietf-subscribed-notifications" within the YANG library of the
publisher. In addition support for optional features: "encode-xml",
"encode-json", "configured" "supports-vrf", and "replay" MUST also be
indicated if supported.
If a publisher supports this specification but not subscriptions via
[RFC5277], the publisher MUST NOT advertise
"urn:ietf:params:netconf:capability:notification:1.0". Even without
this advertisement however, the publisher MUST support the one-way
notification element of [RFC5277] Section 4.
3. YANG Data Model Trees
This section contains tree diagrams for top level YANG Data Node
containers defined in Section 4. If you would rather see tree
diagrams for Notifications, see Section 2.7. Or for the tree
diagrams for the RPCs, see Section 2.4.
Voit, et al. Expires July 28, 2018 [Page 24]
Internet-Draft Subscribed Notifications January 2018
3.1. Event Streams Container
A publisher maintains a list of available event streams as
operational data. This list contains both standardized and vendor-
specific event streams. The list of event streams that are supported
by the publisher and against which subscription is allowed may be
acquired from the "streams" container within the YANG module.
+--rw streams
+--rw stream* [name]
+--rw name stream
+--rw description string
+--rw replay-support? empty {replay}?
+--rw replay-log-creation-time? yang:date-and-time {replay}?
+--rw replay-log-aged-time? yang:date-and-time {replay}?
Figure 10: Stream Container
3.2. Event Stream Filters Container
The "filters" container maintains a list of all subscription filters
which persist outside the life-cycle of a single subscription. This
enables pre-defined and validated filters which may be referenced and
used by more than one subscription.
+--rw filters
+--rw stream-filter* [identifier]
+--rw identifier filter-id
+--rw (filter-spec)?
+--:(stream-subtree-filter)
| +--rw stream-subtree-filter? {subtree}?
+--:(stream-xpath-filter)
+--rw stream-xpath-filter? yang:xpath1.0 {xpath}?
Figure 11: Filter Container
3.3. Subscriptions Container
The "subscriptions" container maintains a list of all subscriptions
on a publisher, both configured and dynamic. It can be used to
retrieve information about the subscriptions which a publisher is
serving.
Voit, et al. Expires July 28, 2018 [Page 25]
Internet-Draft Subscribed Notifications January 2018
+--ro subscriptions
+--ro subscription* [identifier]
+--ro identifier subscription-id
+--ro configured-subscription-state? enumeration {configured}?
+--ro purpose? string {configured}?
+--ro protocol transport {configured}?
+--ro encoding encoding
+--ro (target)
| +--:(stream)
| +--ro (stream-filter)?
| | +--:(by-reference)
| | | +--ro stream-filter-ref stream-filter-ref
| | +--:(within-subscription)
| | +--ro (filter-spec)?
| | +--:(stream-subtree-filter)
| | | +--ro stream-subtree-filter? {subtree}?
| | +--:(stream-xpath-filter)
| | +--ro stream-xpath-filter?
| | yang:xpath1.0 {xpath}?
| +--ro stream? stream-ref
| +--ro replay-start-time? yang:date-and-time {replay}?
+--ro stop-time? yang:date-and-time
+--ro dscp? inet:dscp {qos}?
+--ro weighting? uint8 {qos}?
+--ro dependency? sn:subscription-id {qos}?
+--ro (notification-message-origin)?
| +--:(interface-originated)
| | +--ro source-interface? if:interface-ref
| +--:(address-originated)
| +--ro source-vrf? ->
| /ni:network-instances/network-instance/name {supports-vrf}?
| +--ro source-address? inet:ip-address-no-zone
+--ro receivers
+--ro receiver* [address port]
+--ro address inet:host
+--ro port inet:port-number
+--ro pushed-notifications? yang:counter64
+--ro excluded-notifications? yang:counter64
+--ro state enumeration
+---x reset
+--ro output
+--ro time yang:date-and-time
4. Data Model
<CODE BEGINS> file "ietf-subscribed-notifications@2018-01-25.yang"
module ietf-subscribed-notifications {
yang-version 1.1;
Voit, et al. Expires July 28, 2018 [Page 26]
Internet-Draft Subscribed Notifications January 2018
namespace
"urn:ietf:params:xml:ns:yang:ietf-subscribed-notifications";
prefix sn;
import ietf-yang-types {
prefix yang;
}
import ietf-inet-types {
prefix inet;
}
import ietf-interfaces {
prefix if;
}
import ietf-network-instance {
prefix ni;
}
import ietf-restconf {
prefix rc;
}
organization "IETF";
contact
"WG Web: <http:/tools.ietf.org/wg/netconf/>
WG List: <mailto:netconf@ietf.org>
Editor: Alexander Clemm
<mailto:ludwig@clemm.org>
Editor: Eric Voit
<mailto:evoit@cisco.com>
Editor: Alberto Gonzalez Prieto
<mailto:agonzalezpri@vmware.com>
Editor: Einar Nilsen-Nygaard
<mailto:einarnn@cisco.com>
Editor: Ambika Prasad Tripathy
<mailto:ambtripa@cisco.com>";
description
"Contains a YANG specification for subscribing to event records
and receiving matching content within notification messages.";
revision 2018-01-25 {
description
"Initial version";
Voit, et al. Expires July 28, 2018 [Page 27]
Internet-Draft Subscribed Notifications January 2018
reference
"draft-ietf-netconf-subscribed-notifications-09";
}
/*
* FEATURES
*/
feature encode-json {
description
"This feature indicates that JSON encoding of notification
messages is supported.";
}
feature encode-xml {
description
"This feature indicates that XML encoding of notification
messages is supported.";
}
feature configured {
description
"This feature indicates that configuration of subscription is
supported.";
}
feature replay {
description
"This feature indicates that historical event record replay is
supported. With replay, it is possible for past event records to
be streamed in chronological order.";
}
feature xpath {
description
"This feature indicates support for xpath filtering.";
reference "http://www.w3.org/TR/1999/REC-xpath-19991116";
}
feature subtree {
description
"This feature indicates support for YANG subtree filtering.";
reference "RFC 6241, Section 6.";
}
feature supports-vrf {
description
"This feature indicates a publisher supports VRF configuration
Voit, et al. Expires July 28, 2018 [Page 28]
Internet-Draft Subscribed Notifications January 2018
for configured subscriptions. VRF support for dynamic
subscriptions does not require this feature.";
reference "draft-ietf-rtgwg-ni-model";
}
feature qos {
description
"This feature indicates a publisher supports one or more optional
Quality of Service (QoS) features to differentiate update record
treatment between publisher and receiver.";
}
/*
* EXTENSIONS
*/
extension subscription-state-notification {
description
"This statement applies only to notifications. It indicates that
the notification is a subscription state notification. Therefore
it does not participate in a regular event stream and does not
need to be specifically subscribed to in order to be received.
This statement can only occur as a substatement to the YANG
'notification' statement.";
}
/*
* IDENTITIES
*/
/* Identities for RPC and Notification errors */
identity establish-subscription-error {
description
"Problem found while attempting to fulfill an
'establish-subscription' rpc request. ";
}
identity modify-subscription-error {
description
"Problem found while attempting to fulfill a
'modify-subscription' rpc request. ";
}
identity delete-subscription-error {
description
"Problem found while attempting to fulfill either a
'delete-subscription' rpc request or a 'kill-subscription'
Voit, et al. Expires July 28, 2018 [Page 29]
Internet-Draft Subscribed Notifications January 2018
rpc request. ";
}
identity subscription-terminated-reason {
description
"Problem condition communicated to a receiver as part of absolute
'subscription-terminated' notification. ";
}
identity subscription-suspended-reason {
description
"Problem condition communicated to a receiver as part of absolute
'subscription-terminated' notification. ";
}
identity dscp-unavailable {
base establish-subscription-error;
description
"Requested DSCP marking not allocatable.";
}
identity filter-unavailable {
base subscription-terminated-reason;
description
"Referenced filter does not exist. This means a receiver is
referencing a filter which doesn't exist, or to which they do not
have access permissions.";
}
identity filter-unsupported {
base establish-subscription-error;
base modify-subscription-error;
description
"Cannot parse syntax within the filter. This failure can be from
a syntax error, or a syntax too complex to be processed by the
publisher.";
}
identity history-unavailable {
base establish-subscription-error;
description
"Replay request too far into the past. This means the publisher
does store historic information for the requested stream, but
not back to the requested timestamp.";
}
identity insufficient-resources {
base establish-subscription-error;
Voit, et al. Expires July 28, 2018 [Page 30]
Internet-Draft Subscribed Notifications January 2018
base modify-subscription-error;
base subscription-suspended-reason;
description
"The publisher has insufficient resources to support the
requested subscription.";
}
identity no-such-subscription {
base modify-subscription-error;
base delete-subscription-error;
base subscription-terminated-reason;
description
"Referenced subscription doesn't exist. This may be as a result of
a non-existent subscription ID, an ID which belongs to another
subscriber, or an ID for configured subscription.";
}
identity replay-unsupported {
base establish-subscription-error;
description
"Replay cannot be performed for this subscription. This means the
publisher will not provide the requested historic information from
the stream via replay to this receiver.";
}
identity stream-unavailable {
base subscription-terminated-reason;
description
"Not a subscribable stream. This means the referenced stream is
not available for subscription by the receiver.";
}
identity suspension-timeout {
base subscription-terminated-reason;
description
"Termination of previously suspended subscription. The publisher
has eliminated the subscription as it exceeded a time limit for
suspension.";
}
identity unsupportable-volume {
base subscription-suspended-reason;
description
"The publisher cannot support the volume of information intended
to be sent for an existing subscription.";
}
/* Identities for encodings */
Voit, et al. Expires July 28, 2018 [Page 31]
Internet-Draft Subscribed Notifications January 2018
identity encodings {
description
"Base identity to represent data encodings";
}
identity encode-xml {
base encodings;
if-feature "encode-xml";
description
"Encode data using XML";
}
identity encode-json {
base encodings;
if-feature "encode-json";
description
"Encode data using JSON";
}
/* Identities for transports */
identity transport {
description
"An identity that represents a the underlying mechanism for
passing notification messages.";
}
identity netconf {
base transport;
description
"Netconf is used a transport for notification messages and state
change notifications.";
reference "draft-ietf-netconf-netconf-event-notifications";
}
identity http2 {
base transport;
description
"HTTP2 is used a transport for notification messages and state
change notifications.";
reference "draft-ietf-netconf-restconf-notif-03, Sections 3.1.1" +
"3.1.3";
}
identity http1.1 {
base transport;
description
"HTTP1.1 is used a transport for notification messages and state
change notifications.";
Voit, et al. Expires July 28, 2018 [Page 32]
Internet-Draft Subscribed Notifications January 2018
reference "draft-ietf-netconf-restconf-notif-03, Section 3.1.2";
}
/*
* TYPEDEFs
*/
typedef subscription-id {
type uint32;
description
"A type for subscription identifiers.";
}
typedef filter-id {
type string;
description
"A type to identify filters which can be associated with a
subscription.";
}
typedef encoding {
type identityref {
base encodings;
}
description
"Specifies a data encoding, e.g. for a data subscription.";
}
typedef transport {
type identityref {
base transport;
}
description
"Specifies protocol used to send notification messages to a
receiver.";
}
typedef stream-ref {
type leafref {
path "/sn:streams/sn:stream/sn:name";
}
description
"This type is used to reference a system-provided datastream.";
}
typedef stream-filter-ref {
type leafref {
path "/sn:filters/sn:stream-filter/sn:identifier";
Voit, et al. Expires July 28, 2018 [Page 33]
Internet-Draft Subscribed Notifications January 2018
}
description
"This type is used to reference a configured stream filter.";
}
/*
* GROUPINGS
*/
grouping stream-filter-elements {
description
"This grouping defines the base for filters applied to event
streams.";
choice filter-spec {
description
"The content filter specification for this request.";
anydata stream-subtree-filter {
if-feature "subtree";
description
"Event stream evaluation criteria encoded in the syntax of a
subtree filter as defined in RFC 6241, Section 6.
The subtree filter is applied to the representation of
individual, delineated event records as contained within the
event stream. For example, if the notification message
contains an instance of a notification defined in YANG, then
the top-level element is the name of the YANG notification.
If the subtree filter returns a non-empty node set, the filter
matches the event record, and the it is included in the
notification message sent to the receivers.";
reference "RFC 6241, Section 6.";
}
leaf stream-xpath-filter {
if-feature "xpath";
type yang:xpath1.0;
description
"Event stream evaluation criteria encoded in the syntax of
an XPath 1.0 expression.
The XPath expression is evaluated on the representation of
individual, delineated event records as contained within
the event stream. For example, if the notification message
contains an instance of a notification defined in YANG,
then the top-level element is the name of the YANG
notification, and the root node has this top-level element
as the only child.
Voit, et al. Expires July 28, 2018 [Page 34]
Internet-Draft Subscribed Notifications January 2018
The result of the XPath expression is converted to a
boolean value using the standard XPath 1.0 rules. If the
boolean value is 'true', the filter matches the event
record, and the it is included in the notification message
sent to the receivers.
The expression is evaluated in the following XPath context:
o The set of namespace declarations are those in scope on
the 'xpath-filter' leaf element
o The set of variable bindings is empty.
o The function library is the core function library, and
the XPath functions defined in section 10 in RFC 7950.
o The context node is the root node.";
reference
"http://www.w3.org/TR/1999/REC-xpath-19991116
RFC 7950, Section 10.";
}
}
}
grouping update-qos {
description
"This grouping describes Quality of Service information
concerning a subscription. This information is passed to lower
layers for transport prioritization and treatment";
leaf dscp {
if-feature "qos";
type inet:dscp;
default "0";
description
"The push update's IP packet transport priority. This is made
visible across network hops to receiver. The transport
priority is shared for all receivers of a given subscription.";
}
leaf weighting {
if-feature "qos";
type uint8 {
range "0 .. 255";
}
description
"Relative weighting for a subscription. Allows an underlying
transport layer perform informed load balance allocations
between various subscriptions";
Voit, et al. Expires July 28, 2018 [Page 35]
Internet-Draft Subscribed Notifications January 2018
reference
"RFC-7540, section 5.3.2";
}
leaf dependency {
if-feature "qos";
type subscription-id;
description
"Provides the Subscription ID of a parent subscription which
has absolute priority should that parent have push updates
ready to egress the publisher. In other words, there should be
no streaming of objects from the current subscription if
the parent has something ready to push.";
reference
"RFC-7540, section 5.3.1";
}
}
grouping subscription-policy-modifiable {
description
"This grouping describes all objects which may be changed
in a subscription via an RPC.";
choice target {
mandatory true;
description
"Identifies the source of information against which a
subscription is being applied, as well as specifics on the
subset of information desired from that source. This choice
exists so that additional filter types can be added via
augmentation.";
case stream {
choice stream-filter {
description
"An event stream filter can be applied to a subscription.
That filter will come either referenced from a global list,
or be provided within the subscription itself.";
case by-reference {
description
"Apply a filter that has been configured separately.";
leaf stream-filter-ref {
type stream-filter-ref;
mandatory true;
description
"References an existing stream-filter which is to
be applied to stream for the subscription.";
}
}
case within-subscription {
description
Voit, et al. Expires July 28, 2018 [Page 36]
Internet-Draft Subscribed Notifications January 2018
"Local definition allows a filter to have the same
lifecycle as the subscription.";
uses stream-filter-elements;
}
}
}
}
leaf stop-time {
type yang:date-and-time;
description
"Identifies a time after which notification messages for a
subscription should not be sent. If stop-time is not present,
the notification messages will continue until the subscription
is terminated. If replay-start-time exists, stop-time must be
for a subsequent time. If replay-start-time doesn't exist,
stop-time must be for a future time.";
}
}
grouping subscription-policy-dynamic {
description
"This grouping describes information concerning a subscription
which can be passed over the RPCs defined in this model.";
leaf encoding {
type encoding;
mandatory true;
description
"The type of encoding for the subscribed data.";
}
uses subscription-policy-modifiable {
augment target/stream {
description
"Adds additional objects which can be modified by RPC.";
leaf stream {
type stream-ref {
require-instance false;
}
mandatory true;
description
"Indicates the stream of event records to be considered for
this subscription.";
}
leaf replay-start-time {
if-feature "replay";
type yang:date-and-time;
description
"Used to trigger the replay feature and indicate that the
replay should start at the time specified. If
Voit, et al. Expires July 28, 2018 [Page 37]
Internet-Draft Subscribed Notifications January 2018
replay-start-time is not present, this is not a replay
subscription and event record push should start immediately.
It is never valid to specify start times that are later than
or equal to the current time.";
}
}
}
uses update-qos;
}
grouping subscription-policy {
description
"This grouping describes the full set of policy information
concerning both dynamic and configured subscriptions, except for
configured receivers.";
leaf protocol {
if-feature "configured";
type transport;
mandatory true;
description
"This leaf specifies the transport protocol used to deliver
messages destined to all receivers of a subscription.";
}
uses subscription-policy-dynamic;
}
grouping notification-origin-info {
description
"Defines the sender source from which notification messages for a
configured subscription are sent.";
choice notification-message-origin {
description
"Identifies the egress interface on the Publisher from which
notification messages are to be sent.";
case interface-originated {
description
"When notification messages to egress a specific, designated
interface on the Publisher.";
leaf source-interface {
type if:interface-ref;
description
"References the interface for notification messages.";
}
}
case address-originated {
description
"When notification messages are to depart from a publisher
using specfic originating address and/or routing context
Voit, et al. Expires July 28, 2018 [Page 38]
Internet-Draft Subscribed Notifications January 2018
information.";
leaf source-vrf {
if-feature "supports-vrf";
type leafref {
path "/ni:network-instances/ni:network-instance/ni:name";
}
description
"VRF from which notification messages should egress a
publisher.";
}
leaf source-address {
type inet:ip-address-no-zone;
description
"The source address for the notification messages. If a
source VRF exists, but this object doesn't, a publisher's
default address for that VRF must be used.";
}
}
}
}
grouping receiver-info {
description
"Defines where and how to get notification messages for a
configured subscriptions to one or more targeted recipient. This
includes specifying the destination addressing as well as a
transport protocol acceptable to the receiver.";
container receivers {
description
"Set of receivers in a subscription.";
list receiver {
key "address port";
min-elements 1;
description
"A single host or multipoint address intended as a target
for the notification messages of a subscription.";
leaf address {
type inet:host;
description
"Specifies the address for the traffic to reach a remote
host. One of the following must be specified: an ipv4
address, an ipv6 address, or a host name.";
}
leaf port {
type inet:port-number;
description
"This leaf specifies the port number to use for messages
destined for a receiver.";
Voit, et al. Expires July 28, 2018 [Page 39]
Internet-Draft Subscribed Notifications January 2018
}
}
}
}
/*
* RPCs
*/
rpc establish-subscription {
description
"This RPC allows a subscriber to create (and possibly negotiate)
a subscription on its own behalf. If successful, the
subscription remains in effect for the duration of the
subscriber's association with the publisher, or until the
subscription is terminated. In case an error occurs, or the
publisher cannot meet the terms of a subscription, and RPC error
is returned, the subscription is not created. In that case, the
RPC reply's error-info MAY include suggested parameter settings
that would have a higher likelihood of succeeding in a subsequent
establish-subscription request.";
input {
uses subscription-policy-dynamic {
refine "encoding" {
mandatory false;
description
"The type of encoding for the subscribed data. If not
included as part of the RPC, the encoding MUST be set by the
publisher to be the encoding used by this RPC.";
}
}
}
}
rc:yang-data establish-subscription-error-stream {
container establish-subscription-error-stream {
description
"If any 'establish-subscription' RPC parameters are
unsupportable against the event stream, a subscription is not
created and the RPC error response MUST indicate the reason
why the subscription failed to be created. This yang-data MAY be
inserted as structured data within a subscription's RPC error
response to indicate the failure reason. This yang-data MUST be
inserted if hints are to be provided back to the subscriber.";
leaf reason {
type identityref {
Voit, et al. Expires July 28, 2018 [Page 40]
Internet-Draft Subscribed Notifications January 2018
base establish-subscription-error;
}
description
"Indicates the reason why the subscription has failed to
be created to a targeted stream.";
}
leaf filter-failure-hint {
type string;
description
"Information describing where and/or why a provided filter
was unsupportable for a subscription.";
}
leaf replay-start-time-hint {
type yang:date-and-time;
description
"If a replay has been requested, but the requested replay
time cannot be honored, this may provide a hint at an
alternate time which may be supportable.";
}
}
}
rpc modify-subscription {
description
"This RPC allows a subscriber to modify a subscription that was
previously created using establish-subscription. If successful,
the changed subscription remains in effect for the duration of
the subscriber's association with the publisher, or until the
subscription is again modified or terminated. In case of an
error or an inability to meet the modified parameters, the
subscription is not modified and the original subscription
parameters remain in effect. In that case, the rpc error
MAY include error-info suggested parameter hints that would have
a high likelihood of succeeding in a subsequent
modify-subscription request. A successful modify-subscription
will return a suspended subscription to an active state.";
input {
leaf identifier {
type subscription-id;
description
"Identifier to use for this subscription.";
}
uses subscription-policy-modifiable;
}
}
rc:yang-data modify-subscription-error-stream {
container modify-subscription-error-stream {
Voit, et al. Expires July 28, 2018 [Page 41]
Internet-Draft Subscribed Notifications January 2018
description
"This yang-data MAY be provided as part of a subscription's RPC
error response when there is a failure of a
'modify-subscription' RPC which has been made against a
stream. This yang-data MUST be used if hints are to be
provides back to the subscriber.";
leaf reason {
type identityref {
base modify-subscription-error;
}
description
"Information in a modify-subscription RPC error response which
indicates the reason why the subscription to an event stream
has failed to be modified.";
}
leaf filter-failure-hint {
type string;
description
"Information describing where and/or why a provided filter
was unsupportable for a subscription.";
}
}
}
rpc delete-subscription {
description
"This RPC allows a subscriber to delete a subscription that
was previously created from by that same subscriber using the
establish-subscription RPC.";
input {
leaf identifier {
type subscription-id;
mandatory true;
description
"Identifier of the subscription that is to be deleted.
Only subscriptions that were created using
establish-subscription can be deleted via this RPC.";
}
}
}
rpc kill-subscription {
description
"This RPC allows an operator to delete a dynamic subscription
without restrictions on the originating subscriber or underlying
transport session.";
input {
leaf identifier {
Voit, et al. Expires July 28, 2018 [Page 42]
Internet-Draft Subscribed Notifications January 2018
type subscription-id;
mandatory true;
description
"Identifier of the subscription that is to be deleted. Only
subscriptions that were created using establish-subscription
can be deleted via this RPC.";
}
}
}
rc:yang-data delete-subscription-error {
container delete-subscription-error {
description
"If a 'delete-subscription' RPC or a 'kill-subscription' RPC
fails, the subscription is not deleted and the RPC error
response MUST indicate the reason for this failure. This
yang-data MAY be inserted as structured data within a
subscription's RPC error response to indicate the failure
reason.";
leaf reason {
type identityref {
base delete-subscription-error;
}
mandatory true;
description
"Indicates the reason why the subscription has failed to be
deleted.";
}
}
}
/*
* NOTIFICATIONS
*/
notification replay-completed {
sn:subscription-state-notification;
if-feature "replay";
description
"This notification is sent to indicate that all of the replay
notifications have been sent. It must not be sent for any other
reason.";
leaf identifier {
type subscription-id;
mandatory true;
description
"This references the affected subscription.";
}
Voit, et al. Expires July 28, 2018 [Page 43]
Internet-Draft Subscribed Notifications January 2018
}
notification subscription-completed {
sn:subscription-state-notification;
description
"This notification is sent to indicate that a subscription has
finished passing event records.";
leaf identifier {
type subscription-id;
mandatory true;
description
"This references the gracefully completed subscription.";
}
}
notification subscription-started {
sn:subscription-state-notification;
if-feature "configured";
description
"This notification indicates that a subscription has started and
notifications are beginning to be sent. This notification shall
only be sent to receivers of a subscription; it does not
constitute a general-purpose notification.";
leaf identifier {
type subscription-id;
mandatory true;
description
"This references the affected subscription.";
}
uses subscription-policy {
refine "target/stream/replay-start-time" {
description
"Indicates the time that a replay using for the streaming of
buffered event records. This will be populated with the most
recent of the following: replay-log-creation-time,
replay-log-aged-time, replay-start-time, or the most recent
publisher boot time.";
}
refine "target/stream/stream-filter/within-subscription" {
description
"Filter applied to the subscription. If the
'stream-filter-ref' is populated, the filter within the
subscription came from the 'filters' container. Otherwise it
is populated in-line as part of the subscription.";
}
}
}
Voit, et al. Expires July 28, 2018 [Page 44]
Internet-Draft Subscribed Notifications January 2018
notification subscription-resumed {
sn:subscription-state-notification;
description
"This notification indicates that a subscription that had
previously been suspended has resumed. Notifications will once
again be sent. In addition, a subscription-resumed indicates
that no modification of parameters has occurred since the last
time event records have been sent.";
leaf identifier {
type subscription-id;
mandatory true;
description
"This references the affected subscription.";
}
}
notification subscription-modified {
sn:subscription-state-notification;
description
"This notification indicates that a subscription has been
modified. Notification messages sent from this point on will
conform to the modified terms of the subscription. For
completeness, this state change notification includes both
modified and non-modified aspects of a subscription.";
leaf identifier {
type subscription-id;
mandatory true;
description
"This references the affected subscription.";
}
uses subscription-policy {
refine "target/stream/stream-filter/within-subscription" {
description
"Filter applied to the subscription. If the
'stream-filter-ref' is populated, the filter within the
subscription came from the 'filters' container. Otherwise it
is populated in-line as part of the subscription.";
}
}
}
notification subscription-terminated {
sn:subscription-state-notification;
description
"This notification indicates that a subscription has been
terminated.";
leaf identifier {
type subscription-id;
Voit, et al. Expires July 28, 2018 [Page 45]
Internet-Draft Subscribed Notifications January 2018
mandatory true;
description
"This references the affected subscription.";
}
leaf reason {
type identityref {
base subscription-terminated-reason;
}
mandatory true;
description
"Identifies the condition which resulted in the termination .";
}
}
notification subscription-suspended {
sn:subscription-state-notification;
description
"This notification indicates that a suspension of the
subscription by the publisher has occurred. No further
notifications will be sent until the subscription resumes.
This notification shall only be sent to receivers of a
subscription; it does not constitute a general-purpose
notification.";
leaf identifier {
type subscription-id;
mandatory true;
description
"This references the affected subscription.";
}
leaf reason {
type identityref {
base subscription-suspended-reason;
}
mandatory true;
description
"Identifies the condition which resulted in the suspension.";
}
}
/*
* DATA NODES
*/
container streams {
config false;
description
"This container contains information on the built-in streams
provided by the publisher.";
Voit, et al. Expires July 28, 2018 [Page 46]
Internet-Draft Subscribed Notifications January 2018
list stream {
key "name";
description
"Identifies the built-in streams that are supported by the
publisher.";
leaf name {
type string;
description
"A handle for a system-provided datastream made up of a
sequential set of event records, each of which is
characterized by its own domain and semantics.";
}
leaf description {
type string;
mandatory true;
description
"A description of the event stream, including such information
as the type of event records that are available within this
stream.";
}
leaf replay-support {
if-feature "replay";
type empty;
description
"Indicates that event record replay is available on this
stream.";
}
leaf replay-log-creation-time {
if-feature "replay";
type yang:date-and-time;
description
"The timestamp of the creation of the log used to support the
replay function on this stream. Note that this might be
earlier then the earliest available information contained in
the log. This object is updated if the log resets for some
reason. This object MUST be present if replay is supported.";
}
leaf replay-log-aged-time {
if-feature "replay";
type yang:date-and-time;
description
"The timestamp of the last event record aged out of the log.
This object MUST be present if replay is supported and any
event record have been aged out of the log.";
}
}
}
Voit, et al. Expires July 28, 2018 [Page 47]
Internet-Draft Subscribed Notifications January 2018
container filters {
description
"This container contains a list of configurable filters
that can be applied to subscriptions. This facilitates
the reuse of complex filters once defined.";
list stream-filter {
key "identifier";
description
"A list of pre-positioned filters that can be applied to
subscriptions.";
leaf identifier {
type filter-id;
description
"An identifier to differentiate between filters.";
}
uses stream-filter-elements;
}
}
container subscriptions {
description
"Contains the list of currently active subscriptions, i.e.
subscriptions that are currently in effect, used for subscription
management and monitoring purposes. This includes subscriptions
that have been setup via RPC primitives as well as subscriptions
that have been established via configuration.";
list subscription {
key "identifier";
description
"The identity and specific parameters of a subscription.
Subscriptions within this list can be created using a control
channel or RPC, or be established through configuration.";
leaf identifier {
type subscription-id;
description
"Identifier of a subscription; unique within a publisher";
}
leaf configured-subscription-state {
if-feature "configured";
type enumeration {
enum valid {
value 1;
description
"Connection is active and healthy.";
}
enum invalid {
value 2;
description
Voit, et al. Expires July 28, 2018 [Page 48]
Internet-Draft Subscribed Notifications January 2018
"The subscription as a whole is unsupportable with its
current parameters.";
}
enum concluded {
value 3;
description
"A subscription is inactive as it has hit a stop time,
but not yet been removed from configuration.";
}
}
config false;
description
"The presence of this leaf indicates that the subscription
originated from configuration, not through a control channel
or RPC. The value indicates the system established state
of the subscription.";
}
leaf purpose {
if-feature "configured";
type string;
description
"Open text allowing a configuring entity to embed the
originator or other specifics of this subscription.";
}
uses subscription-policy {
refine "target/stream/stream" {
description
"Indicates the stream of event records to be considered for
this subscription. If a stream has been removed, and no
longer can be referenced by an active subscription, send a
'subscription-terminated' notification with
'stream-unavailable' as the reason. If a configured
subscription refers to a non-existent stream, move that
subscription to the 'invalid' state.";
}
}
uses notification-origin-info {
if-feature "configured";
}
uses receiver-info {
augment receivers/receiver {
description
"include operational data for receivers.";
leaf pushed-notifications {
type yang:counter64;
config false;
description
"Operational data which provides the number of update
Voit, et al. Expires July 28, 2018 [Page 49]
Internet-Draft Subscribed Notifications January 2018
notification messages pushed to a receiver.";
}
leaf excluded-notifications {
type yang:counter64;
config false;
description
"Operational data which provides the number of event
records from a stream explicitly removed via filtering so
that they are not sent to a receiver.";
}
leaf state {
type enumeration {
enum active {
value 1;
description
"Receiver is currently being sent any applicable
notification messages for the subscription.";
}
enum suspended {
value 2;
description
"Receiver state is suspended, so the publisher
is currently unable to provide notification messages
for the subscription.";
}
enum connecting {
value 3;
if-feature "configured";
description
"A subscription has been configured, but a
subscription-started state change notification needs
to be successfully received before notification
messages are sent.";
}
enum timeout {
value 4;
if-feature "configured";
description
"A subscription has failed in sending a subscription
started state change to the receiver.
Additional attempts at connection attempts are not
currently being made.";
}
}
config false;
mandatory true;
description
"Specifies the state of a subscription from the
Voit, et al. Expires July 28, 2018 [Page 50]
Internet-Draft Subscribed Notifications January 2018
perspective of a particular receiver. With this info it
is possible to determine whether a subscriber is currently
generating notification messages intended for that
receiver.";
}
action reset {
description
"Allows the reset of this configured subscription receiver
to the 'connecting' state. This enables the
connection process to be reinitiated.";
output {
leaf time {
type yang:date-and-time;
mandatory true;
description
"Time a publisher returned the receiver to a
connecting state.";
}
}
}
}
}
}
}
}
<CODE ENDS>
5. Considerations
5.1. Implementation Considerations
For a deployment including both configured and dynamic subscriptions,
split subscription identifiers into static and dynamic halves. That
way it is unlikely there will be collisions if the configured
subscriptions attempt to set a subscription-id which might have
already been dynamically allocated. The lower half the "identifier"
object in the subscriptions container SHOULD be used when the
"identifier" is selected and assigned by an external entity (such as
with a configured subscription). And the upper half SHOULD be used
for subscription identifiers dynamically chosen and assigned by the
publisher
Neither state change notification nor subscribed event records within
notification messages may be sent before the transport layer,
including any required capabilities exchange, has been established.
An implementation may choose to transition between active and
suspended subscription states more frequently than required by this
Voit, et al. Expires July 28, 2018 [Page 51]
Internet-Draft Subscribed Notifications January 2018
specification. However if a subscription is unable to marshal all
intended updates into a transmittable message in multiple successive
intervals, the subscription SHOULD be suspended with the reason
"unsupportable-volume".
For configured subscriptions, operations are against the set of
receivers using the subscription identifier as a handle for that set.
But for streaming up dates, state change notifications are local to a
receiver. In this specification it is the case that receivers get no
information from the publisher about the existence of other
receivers. But if an operator wants to let the receivers correlate
results, it is useful to use the subscription identifier handle
across the receivers to allow that correlation.
5.2. IANA Considerations
This document registers the following namespace URI in the "IETF XML
Registry" [RFC3688]:
URI: urn:ietf:params:xml:ns:yang:ietf-subscribed-notifications
Registrant Contact: The IESG.
XML: N/A; the requested URI is an XML namespace.
This document registers the following YANG module in the "YANG Module
Names" registry [RFC6020]:
Name: ietf-subscribed-notifications
Namespace: urn:ietf:params:xml:ns:yang:ietf-subscribed-notifications
Prefix: sn
Reference: draft-ietf-netconf-ietf-subscribed-notifications-08.txt
(RFC form)
5.3. Security Considerations
For dynamic subscriptions the publisher MUST authenticate and
authorize all RPC requests.
Subscriptions could overload a publisher's CPU. For this reason, the
publisher MUST have the ability to decline a dynamic subscription
request, and provide the appropriate RPC error response to a
subscriber should the proposed subscription overly deplete the
publisher's resources.
A publisher needs to be able to suspend an existing dynamic or
configured subscription based on capacity constraints. When this
occurs, the subscription state MUST be updated accordingly and the
receivers notified with subscription state notifications.
Voit, et al. Expires July 28, 2018 [Page 52]
Internet-Draft Subscribed Notifications January 2018
If a malicious or buggy subscriber sends an unexpectedly large number
of RPCs, the result might be an excessive use of system resources.
In such a situation, subscription interactions MAY be terminated by
terminating the transport session.
For both configured and dynamic subscriptions the publisher MUST
authenticate and authorize a receiver via some transport level
mechanism before sending any updates.
A secure transport is highly recommended and the publisher MUST
ensure that the receiver has sufficient authorization to perform the
function they are requesting against the specific subset of content
involved.
A publisher MUST NOT include any content in a notification message
for which the receiver has not been authorized.
With configured subscriptions, one or more publishers could be used
to overwhelm a receiver. No notification messages SHOULD be sent to
any receiver which doesn't even support subscriptions. Receivers
that do not want notification messages need only terminate or refuse
any transport sessions from the publisher.
The NETCONF Authorization Control Model [RFC6536bis] SHOULD be used
to control and restrict authorization of subscription configuration.
This control models permits specifying per-receiver permissions to
receive event records from specific streams.
Where NACM is available, the NACM "very-secure" tag MUST be placed on
the "kill-subscription" RPC so that only administrators have access
to use this.
One subscription id can be used for two or more receivers of the same
configured subscription. But due to the possibility of different
access control permissions per receiver, it SHOULD NOT be assumed
that each receiver is getting identical updates.
6. Acknowledgments
For their valuable comments, discussions, and feedback, we wish to
acknowledge Andy Bierman, Tim Jenkins, Martin Bjorklund, Kent Watsen,
Balazs Lengyel, Robert Wilton, Sharon Chisholm, Hector Trevino, Susan
Hares, Michael Scharf, and Guangying Zheng.
Voit, et al. Expires July 28, 2018 [Page 53]
Internet-Draft Subscribed Notifications January 2018
7. References
7.1. Normative References
[I-D.draft-ietf-rtgwg-ni-model]
Berger, L., Hopps, C., and A. Lindem, "YANG Network
Instances", draft-ietf-rtgwg-ni-model-06 (work in
progress), January 2018.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
DOI 10.17487/RFC3688, January 2004,
<https://www.rfc-editor.org/info/rfc3688>.
[RFC5277] Chisholm, S. and H. Trevino, "NETCONF Event
Notifications", RFC 5277, DOI 10.17487/RFC5277, July 2008,
<https://www.rfc-editor.org/info/rfc5277>.
[RFC6020] Bjorklund, M., Ed., "YANG - A Data Modeling Language for
the Network Configuration Protocol (NETCONF)", RFC 6020,
DOI 10.17487/RFC6020, October 2010,
<https://www.rfc-editor.org/info/rfc6020>.
[RFC6536bis]
Bierman, A. and M. Bjorklund, "Network Configuration
Protocol (NETCONF) Access Control Model", draft-ietf-
netconf-rfc6536bis-09 (work in progress), December 2017.
[RFC7540] Belshe, M., Peon, R., and M. Thomson, Ed., "Hypertext
Transfer Protocol Version 2 (HTTP/2)", RFC 7540,
DOI 10.17487/RFC7540, May 2015,
<https://www.rfc-editor.org/info/rfc7540>.
[RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
RFC 7950, DOI 10.17487/RFC7950, August 2016,
<https://www.rfc-editor.org/info/rfc7950>.
[XPATH] Clark, J. and S. DeRose, "XML Path Language (XPath)
Version 1.0", November 1999,
<http://www.w3.org/TR/1999/REC-xpath-19991116>.
Voit, et al. Expires July 28, 2018 [Page 54]
Internet-Draft Subscribed Notifications January 2018
7.2. Informative References
[I-D.draft-ietf-netconf-netconf-event-notifications]
Clemm, Alexander., Voit, Eric., Gonzalez Prieto, Alberto.,
Nilsen-Nygaard, E., Tripathy, A., Chisholm, S., and H.
Trevino, "NETCONF support for event notifications",
October 2017, <https://datatracker.ietf.org/doc/
draft-ietf-netconf-netconf-event-notifications/>.
[I-D.draft-ietf-netconf-restconf-notif]
Voit, Eric., Clemm, Alexander., Tripathy, A., Nilsen-
Nygaard, E., and Alberto. Gonzalez Prieto, "Restconf and
HTTP transport for event notifications", August 2016,
<https://datatracker.ietf.org/doc/
draft-ietf-netconf-restconf-notif/>.
[I-D.ietf-netconf-yang-push]
Clemm, Alexander., Voit, Eric., Gonzalez Prieto, Alberto.,
Tripathy, A., Nilsen-Nygaard, E., Bierman, A., and B.
Lengyel, "YANG Datastore Subscription", December 2017,
<https://datatracker.ietf.org/doc/
draft-ietf-netconf-yang-push/>.
[I.D.draft-ietf-netconf-notification-messages]
Voit, Eric., Clemm, Alexander., Bierman, A., and T.
Jenkins, "YANG Notification Headers and Bundles",
September 2017, <https://datatracker.ietf.org/doc/
draft-ietf-netconf-notification-messages>.
[RFC6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
and A. Bierman, Ed., "Network Configuration Protocol
(NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
<https://www.rfc-editor.org/info/rfc6241>.
[RFC7923] Voit, E., Clemm, A., and A. Gonzalez Prieto, "Requirements
for Subscription to YANG Datastores", RFC 7923,
DOI 10.17487/RFC7923, June 2016,
<https://www.rfc-editor.org/info/rfc7923>.
[RFC8040] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017,
<https://www.rfc-editor.org/info/rfc8040>.
Appendix A. Changes between revisions
(To be removed by RFC editor prior to publication)
v08 - v09
Voit, et al. Expires July 28, 2018 [Page 55]
Internet-Draft Subscribed Notifications January 2018
o NMDA model supported. Non NMDA version at https://github.com/
netconf-wg/rfc5277bis/
o Error mechanism revamped to match to embedded implementations.
o Explicitly identified error codes relevant to each RPC/
Notification
v07 - v08
o Split YANG trees to separate document subsections.
o Clarified configured state machine based on Balazs comments, and
moved it into the configured subscription subsections.
o Normative reference to Network Instance model for VRF
o One transport protocol for all receivers of configured
subscriptions.
o QoS section moved in from yang-push
v06 - v07
o Clarification on state machine for configured subscriptions.
v05 - v06
o Made changes proposed by Martin, Kent, and others on the list.
Most significant of these are Stream returned to string (with the
SYSLOG identity removed), intro section on 5277 relationship, an
identity set moved to an enumeration, clean up of definitions/
terminology, state machine proposed for configured subscriptions
with a clean-up of subscription state options.
o JSON and XML become features. Also Xpath and subtree filtering
become features
o Terminology updates with event records, and refinement of filters
to just stream filters.
o Encoding refined in establish-subscription so it takes the RPC's
encoding as the default.
o Namespaces in examples fixed.
v04 - v05
Voit, et al. Expires July 28, 2018 [Page 56]
Internet-Draft Subscribed Notifications January 2018
o Returned to the explicit filter subtyping of v00
o stream object changed to 'name' from 'stream'
o Cleaned up examples
o Clarified that JSON support needs notification-messages draft.
v03 - v04
o Moved back to the use of RFC5277 one-way notifications and
encodings.
v03 - v04
o Replay updated
v02 - v03
o RPCs and Notification support is identified by the Notification
2.0 capability.
o Updates to filtering identities and text
o New error type for unsupportable volume of updates
o Text tweaks.
v01 - v02
o Subscription status moved under receiver.
v00 - v01
o Security considerations updated
o Intro rewrite, as well as scattered text changes
o Added Appendix A, to help match this to related drafts in progress
o Updated filtering definitions, and filter types in yang file, and
moved to identities for filter types
o Added Syslog as a stream
o HTTP2 moved in from YANG-Push as a transport option
Voit, et al. Expires July 28, 2018 [Page 57]
Internet-Draft Subscribed Notifications January 2018
o Replay made an optional feature for events. Won't apply to
datastores
o Enabled notification timestamp to have different formats.
o Two error codes added.
v01 5277bis - v00 subscribed notifications
o Kill subscription RPC added.
o Renamed from 5277bis to Subscribed Notifications.
o Changed the notification capabilities version from 1.1 to 2.0.
o Extracted create-subscription and other elements of RFC5277.
o Error conditions added, and made specific in return codes.
o Simplified yang model structure for removal of 'basic' grouping.
o Added a grouping for items which cannot be statically configured.
o Operational counters per receiver.
o Subscription-id and filter-id renamed to identifier
o Section for replay added. Replay now cannot be configured.
o Control plane notification renamed to subscription state
notification
o Source address: Source-vrf changed to string, default address
option added
o In yang model: 'info' changed to 'policy'
o Scattered text clarifications
v00 - v01 of 5277bis
o YANG Model changes. New groupings for subscription info to allow
restriction of what is changeable via RPC. Removed notifications
for adding and removing receivers of configured subscriptions.
o Expanded/renamed definitions from event server to publisher, and
client to subscriber as applicable. Updated the definitions to
include and expand on RFC 5277.
Voit, et al. Expires July 28, 2018 [Page 58]
Internet-Draft Subscribed Notifications January 2018
o Removal of redundancy with other drafts
o Many other clean-ups of wording and terminology
Authors' Addresses
Eric Voit
Cisco Systems
Email: evoit@cisco.com
Alexander Clemm
Huawei
Email: ludwig@clemm.org
Alberto Gonzalez Prieto
VMWare
Email: agonzalezpri@vmware.com
Einar Nilsen-Nygaard
Cisco Systems
Email: einarnn@cisco.com
Ambika Prasad Tripathy
Cisco Systems
Email: ambtripa@cisco.com
Voit, et al. Expires July 28, 2018 [Page 59]