NETCONF A. Clemm
Internet-Draft Huawei
Intended status: Standards Track E. Voit
Expires: April 28, 2018 Cisco Systems
A. Gonzalez Prieto
VMware
A. Tripathy
E. Nilsen-Nygaard
Cisco Systems
A. Bierman
YumaWorks
B. Lengyel
Ericsson
October 25, 2017
YANG Datastore Subscription
draft-ietf-netconf-yang-push-11
Abstract
Providing visibility into changes made on YANG configuration and
operational objects enables new capabilities such as remote mirroring
of configuration and operational state. Via the mechanism described
in this document, subscriber applications may request a continuous,
customized stream of updates from a YANG datastore.
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 April 28, 2018.
Clemm, et al. Expires April 28, 2018 [Page 1]
Internet-Draft YANG-Push October 2017
Copyright Notice
Copyright (c) 2017 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
(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.
This document may contain material from IETF Documents or IETF
Contributions published or made publicly available before November
10, 2008. The person(s) controlling the copyright in some of this
material may not have granted the IETF Trust the right to allow
modifications of such material outside the IETF Standards Process.
Without obtaining an adequate license from the person(s) controlling
the copyright in such materials, this document may not be modified
outside the IETF Standards Process, and derivative works of it may
not be created outside the IETF Standards Process, except to format
it for publication as an RFC or to translate it into languages other
than English.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Definitions and Acronyms . . . . . . . . . . . . . . . . . . 4
3. Solution Overview . . . . . . . . . . . . . . . . . . . . . . 4
3.1. Subscription Model . . . . . . . . . . . . . . . . . . . 4
3.2. Negotiation of Subscription Policies . . . . . . . . . . 6
3.3. On-Change Considerations . . . . . . . . . . . . . . . . 6
3.4. Promise-Theory Considerations . . . . . . . . . . . . . . 7
3.5. Data Encodings . . . . . . . . . . . . . . . . . . . . . 8
3.6. Datastore Selection Filters . . . . . . . . . . . . . . . 8
3.7. Streaming Updates . . . . . . . . . . . . . . . . . . . . 9
3.8. Subscription Management . . . . . . . . . . . . . . . . . 12
3.9. Receiver Authorization . . . . . . . . . . . . . . . . . 13
3.10. On-change Notifiable YANG objects . . . . . . . . . . . . 14
3.11. Other Considerations . . . . . . . . . . . . . . . . . . 15
4. A YANG data model for management of datastore push
subscriptions . . . . . . . . . . . . . . . . . . . . . . . . 16
4.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . 16
4.2. Subscription configuration . . . . . . . . . . . . . . . 24
4.3. YANG Notifications . . . . . . . . . . . . . . . . . . . 26
Clemm, et al. Expires April 28, 2018 [Page 2]
Internet-Draft YANG-Push October 2017
4.4. YANG RPCs . . . . . . . . . . . . . . . . . . . . . . . . 26
5. YANG module . . . . . . . . . . . . . . . . . . . . . . . . . 31
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 46
7. Security Considerations . . . . . . . . . . . . . . . . . . . 47
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 47
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 47
9.1. Normative References . . . . . . . . . . . . . . . . . . 47
9.2. Informative References . . . . . . . . . . . . . . . . . 48
Appendix A. Changes between revisions . . . . . . . . . . . . . 49
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 51
1. Introduction
Traditional approaches to remote visibility have been built on
polling. With polling, data is periodically requested and retrieved
by a client from a server to stay up-to-date. However, there are
issues associated with polling-based management:
o Polling incurs significant latency. This latency prohibits many
application types.
o Polling cycles may be missed, requests may be delayed or get lost,
often when the network is under stress and the need for the data
is the greatest.
o Polling requests may undergo slight fluctuations, resulting in
intervals of different lengths. The resulting data is difficult
to calibrate and compare.
o For applications that monitor for changes, many remote polling
cycles place ultimately fruitless load on the network, devices,
and applications.
A more effective alternative to polling is for an application to
receive automatic and continuous updates from a targeted subset of a
datastore. Accordingly, there is a need for a service that allows
applications to subscribe to updates from a YANG datastore and that
enables the publisher to push and in effect stream those updates.
The requirements for such a service have been documented in
[RFC7923].
This document defines a corresponding solution that is built on top
of "Custom Subscription to Event Streams"
[I-D.draft-ietf-netconf-subscribed-notifications]. Supplementing
that work are YANG data model augmentations, extended RPCs, and new
datastore specific update notifications. Transport options for
[I-D.draft-ietf-netconf-subscribed-notifications] will work
seamlessly with this solution.
Clemm, et al. Expires April 28, 2018 [Page 3]
Internet-Draft YANG-Push October 2017
2. Definitions and Acronyms
The terms below supplement those defined in
[I-D.draft-ietf-netconf-subscribed-notifications].
Data node: An instance of management information in a YANG datastore.
Data node update: A data item containing the current value/property
of a Data node at the time the data node update was created.
Datastore: A conceptual store of instantiated management information,
with individual data items represented by data nodes which are
arranged in hierarchical manner.
Data subtree: An instantiated data node and the data nodes that are
hierarchically contained within it.
Update record: A representation data node update(s) resulting from
the application of a selection filter for a subscription. An update
record will include the value/property of one or more data nodes at a
point in time. It may contain the update type for each data node
(e.g., add, change, delete). Also included may be metadata/headers
such as a subscription-id.
Selection filter: Evaluation and/or selection criteria, which may be
applied against a targeted set of objects.
Update trigger: A mechanism that determines when an update record
needs to be generated.
YANG-Push: The subscription and push mechanism for YANG datastores
that is specified in this document.
3. Solution Overview
This document specifies a solution for a push update subscription
service. This solution supports the dynamic as well as configured
subscriptions to information updates from YANG datastores.
Subscriptions specify when notification messages should be sent and
what data to include in update records. YANG objects are
subsequently pushed from the publisher to the receiver per the terms
of the subscription.
3.1. Subscription Model
YANG-push subscriptions are defined using a data model that is itself
defined in YANG. This model enhances the subscription model defined
in [I-D.draft-ietf-netconf-subscribed-notifications] with
Clemm, et al. Expires April 28, 2018 [Page 4]
Internet-Draft YANG-Push October 2017
capabilities that allow subscribers to subscribe to data node
updates, specifically to specify the triggers defining when to
generate update records as well as what to include in an update
record. Key enhancements include:
o Specification of selection filters which identify targeted YANG
data nodes and/or subtrees within a datastore for which updates
are to be pushed.
o An encoding (using anydata) for the contents of periodic and on-
change push updates.
o Specification of update policies contain conditions which trigger
the generation and pushing of new update records. There are two
types of triggers for subscriptions: periodic and on-change.
* For periodic subscriptions, the trigger is specified by two
parameters that define when updates are to be pushed. These
parameters are the period interval with which to report
updates, and an anchor time which can be used to calculate at
which point in time updates need to be assembled and sent.
* For on-change subscriptions, a trigger occurs whenever a change
in the subscribed information is detected. Included are
additional parameters such as:
+ Dampening period: In an on-change subscription, the first
change that is detected results in an update to be sent
immediately. However, sending successive updates whenever
further changes are detected might result in quick
exhaustion of resources in case of very rapid changes. In
order to protect against that, a dampening period is used to
specify the interval which must pass before successive
update records for the same subscription are generated. The
dampening period collectively applies to the set of all data
nodes of a single subscription. This means that when there
is a change to a subscribed object, an update record
containing that object is created either immediately when no
dampening period is already in effect, or at the end of a
dampening period.
+ Change type: This parameter can be used to reduce the types
of datastore changes for which updates are sent (e.g., you
might only send when an object is created or deleted, but
not when an object value changes).
+ No Synch on start: defines whether or not a complete push-
update of all subscribed data will be sent at the beginning
Clemm, et al. Expires April 28, 2018 [Page 5]
Internet-Draft YANG-Push October 2017
of a subscription. Such early synchronization establishes
the frame of reference for subsequent updates.
3.2. Negotiation of Subscription Policies
A dynamic subscription request SHOULD be declined if a publisher's
assessment is that it may be unable to provide update records meeting
the terms of the request. In this case, a subscriber may quickly
follow up with a new subscription request using different parameters.
Random guessing at different parameters by a subscriber is to be
discouraged. Therefore, in order to minimize the number of
subscription iterations between subscriber and publisher, dynamic
subscriptions SHOULD support a simple negotiation between subscribers
and publishers for subscription parameters. This negotiation is in
the form of a no-success response to a failed establish or modify
subscription request. The no-success message SHOULD include in the
returned error response information that, when considered, increases
the likelihood of success for subsequent requests. However, there
are no guarantees that subsequent requests for this subscriber will
be accepted.
[I-D.draft-ietf-netconf-subscribed-notifications] contains several
negotiable subscription parameters. Additional yang-push negotiation
information defined in this specification includes hints at
acceptable time intervals, size estimates for the number or objects
which would be returned from a filter, and the location of an error
in a provided filter.
3.3. On-Change Considerations
On-change subscriptions allow subscribers to receive updates whenever
changes to targeted objects occur. As such, on-change subscriptions
are particularly effective for data that changes infrequently, yet
for which applications need to be quickly notified whenever a change
does occur with minimal delay.
On-change subscriptions tend to be more difficult to implement than
periodic subscriptions. Accordingly, on-change subscriptions may not
be supported by all implementations or for every object.
Whether or not to accept or reject on-change subscription requests
when the scope of the subscription contains objects for which on-
change is not supported is up to the publisher implementation. A
publisher MAY accept an on-change subscription even when the scope of
the subscription contains objects for which on-change is not
supported. In that case, updates are sent only for those objects
within the scope that do support on-change updates whereas other
Clemm, et al. Expires April 28, 2018 [Page 6]
Internet-Draft YANG-Push October 2017
objects are excluded from update records, whether or not their values
actually change. In order for a subscriber to determine whether
objects support on-change subscriptions, objects are marked
accordingly on a publisher. Accordingly, when subscribing, it is the
responsibility of the subscriber to ensure it is aware of which
objects support on-change and which do not. For more on how objects
are so marked, see Section 3.10.
Alternatively, a publisher MAY decide to simply reject an on-change
subscription in case the scope of the subscription contains objects
for which on-change is not supported. In case of a configured
subscription, the subscription MAY be suspended.
To avoid flooding receivers with repeated updates for subscriptions
containing fast-changing objects, or objects with oscillating values,
an on-change subscription allows for the definition of a dampening
period. Once an update record for a given object is generated, no
other updates for this particular subscription will be created until
the end of the dampening period. Values sent at the end of the
dampening period are the current values of all changed objects which
are current at the time the dampening period expires. Changed
objects include those which were deleted or newly created during that
dampening period. If an object has returned to its original value
(or even has been created and then deleted) during the dampening-
period, the last change will still be sent. This will indicate churn
is occurring on that object.
In cases where a subscriber wants to have separate dampening periods
for different objects, multiple subscriptions with different objects
in a selection filter can be created.
On-change subscriptions can be refined to let users subscribe only to
certain types of changes. For example, a subscriber might only want
object creations and deletions, but not modifications of object
values.
3.4. Promise-Theory Considerations
A subscription to updates from a YANG datastore is intended to
obviate the need for polling. However, in order to do so, it is
critical that subscribers can rely on the subscription and have
confidence that they will indeed receive the subscribed updates
without having to worry updates being silently dropped. In other
words, a subscription constitutes a promise on the side of the
publisher to provide the receivers with updates per the terms of the
subscription.
Clemm, et al. Expires April 28, 2018 [Page 7]
Internet-Draft YANG-Push October 2017
Now, there are many reasons why a publisher may at some point no
longer be able to fulfill the terms of the subscription, even if the
subscription had been entered into with good faith. For example, the
volume of data objects may be larger than anticipated, the interval
may prove too short to send full updates in rapid succession, or an
internal problem may prevent objects from being collected. If for
some reason the publisher of a subscription is not able to keep its
promise, receivers MUST be notified immediately and reliably. The
publisher MAY also suspend the subscription.
A publisher SHOULD reject a request for a subscription if it is
unlikely that the publisher will be able fulfill the terms of that
subscription request. In such cases, it is preferable to have a
subscriber request a less resource intensive subscription than to
deal with frequently degraded behavior. Please see [promise] for
more on the transactional basis underlying the publisher and
subscriber interactions within this document.
3.5. Data Encodings
A publisher MUST support XML encoding and MAY support other encodings
such as JSON encoding.
3.5.1. Periodic Subscriptions
In a periodic subscription, the data included as part of an update
corresponds to data that could have been simply retrieved using a get
operation and is encoded in the same way.
3.5.2. On-Change Subscriptions
In an on-change subscription, updates need to indicate not only
values of changed data nodes but also the types of changes that
occurred since the last update. Therefore encoding rules for data in
on-change updates will follow YANG-patch operation as specified in
[RFC8072]. The YANG-patch will describe what needs to be applied to
the earlier state reported by the preceding update, to result in the
now-current state. Note that contrary to [RFC8072], objects
encapsulated are not restricted to configuration objects only.
3.6. Datastore Selection Filters
Subscription policy specifies both the selection filters and the
datastores against which these selection filters will be applied.
The result is the push of information necessary to remotely maintain
an extract of the publisher's datastore.
Clemm, et al. Expires April 28, 2018 [Page 8]
Internet-Draft YANG-Push October 2017
Only a single selection filter can be applied to a subscription at a
time. The following selection filter types are included in the yang-
push data model, and may be applied against a datastore:
o subtree: A subtree selection filter identifies one or more
subtrees. When specified, updates will only come from the data
nodes of selected YANG subtree(s). The syntax and semantics
correspond to that specified for [RFC6241] section 6.
o xpath: An xpath selection filter is an XPath expression which may
be meaningfully applied to a datastore. It is the results of this
expression which will be pushed.
These filters are intended to be used as selectors that define which
objects are within the scope of a subscription. A publisher MUST
support at least one type of selection filter.
Selection filters are not intended to be used to filter objects based
on a non-key property. Supporting non-key property filtering so
would have a number of implications that would result in significant
complexity. While it is possible to define extensions in the future
that will support selection filtering based on values, this is not
supported in this version of yang-push and a publisher MAY reject a
subscription request that contains a filter for object values.
Xpath itself provides powerful filtering constructs, and care must be
used in filter definition. As an example, consider an xpath filter
with a boolean result; such a result will not provide an easily
interpretable subset of a datastore. Beyond the boolean example, it
is quite possible to define an xpath filter where results are easy
for an application to mis-interpret. Consider an xpath filter which
only passes a datastore object when an interface is up. It is up to
the receiver to understand implications of the presence or absence of
objects in each update.
It is not expected that implementations will support comprehensive
filter syntax and boundless complexity. It will be up to
implementations to describe what is viable, but the goal is to
provide equivalent capabilities to what is available with a GET.
Implementations MUST reject dynamic subscriptions or suspend
configured subscriptions if they include filters which are
unsupportable on a platform.
3.7. Streaming Updates
Contrary to traditional data retrieval requests, datastore
subscription enables an unbounded series of update records to be
streamed over time. Two generic YANG notifications for update
Clemm, et al. Expires April 28, 2018 [Page 9]
Internet-Draft YANG-Push October 2017
records have been defined for this: "push-update" and "push-change-
update".
A push-update notification defines a complete, filtered update of the
datastore per the terms of a subscription. This type of YANG
notification is used for continuous updates of periodic
subscriptions. A push-update notification can also be used for the
on-change subscriptions in two cases. First it will be used as the
initial push-update if there is a need to synchronize the receiver at
the start of a new subscription. It also MAY be sent if the
publisher later chooses to resynch an on-change subscription. The
push-update record contains a data snippet that contains an
instantiated subtree with the subscribed contents. The content of
the update record is equivalent to the contents that would be
obtained had the same data been explicitly retrieved using e.g., a
NETCONF "get" operation, with the same filters applied.
A push-change-update notification is the most common type of update
for on-change subscriptions. The update record in this case contains
a data snippet that indicates the set of changes that data nodes have
undergone since the last notification message. In other words, this
indicates which data nodes have been created, deleted, or have had
changes to their values. In cases where multiple changes have
occurred and the object has not been deleted, the object's most
current value is reported. (In other words, for each object, only
one change is reported, not its entire history. Doing so would
defeat the purpose of the dampening period.)
These new push-update or push-change-update are encoded and placed
within notification messages, and ultimately queued for egress over
the specified transport.
The following is an example of a notification message for a
subscription tracking the operational status of a single Ethernet
port (per [RFC7223]). This notification message is encoded XML over
NETCONF as per [I-D.draft-ietf-netconf-netconf-event-notifications].
Clemm, et al. Expires April 28, 2018 [Page 10]
Internet-Draft YANG-Push October 2017
<notification xmlns="urn:ietf:params:xml:ns:netconf:notification:1.0">
<eventTime>2017-10-25T08:00:11.22Z</eventTime>
<push-update xmlns="urn:ietf:params:xml:ns:yang:ietf-yang-push">
<subscription-id>1011</subscription-id>
<datastore-contents>
<interfaces-state xmlns="http://foo.com/ietf-interfaces">
<interface>
<name>eth0</name>
<oper-status>up</oper-status>
</interface>
</interfaces-state>
</datastore-contents>
</push-change-update>
</notification>
Figure 1: Push example
The following is an example of an on-change notification message for
the same subscription.
<notification xmlns="urn:ietf:params:xml:ns:netconf:notification:1.0">
<eventTime>2017-10-25T08:22:33.44Z</eventTime>
<push-change-update xmlns="urn:ietf:params:xml:ns:yang:ietf-yang-push">
<subscription-id>89</subscription-id>
<datastore-changes>
<yang-patch xmlns="urn:ietf:params:xml:ns:yang:ietf-yang-patch">
<patch-id>null</patch-id>
<edit>
<edit-id>edit1</edit-id>
<operation>merge</operation>
<target>/ietf-interfaces/interfaces-state</target>
<value>
<interfaces-state xmlns="http://foo.com/ietf-interfaces">
<interface>
<name>eth0</name>
<oper-status>down</oper-status>
</interface>
</interfaces-state>
</value>
</edit>
</yang-patch>
</datastore-changes>
</push-change-update>
</notification>
Figure 2: Push example for on change
Clemm, et al. Expires April 28, 2018 [Page 11]
Internet-Draft YANG-Push October 2017
3.8. Subscription Management
The RPCs defined within
[I-D.draft-ietf-netconf-subscribed-notifications] have been enhanced
to support YANG datastore subscription negotiation. Included in
these enhancements are error codes which can indicate why a datastore
subscription attempt has failed.
A datastore subscription can be rejected for multiple reasons. This
includes a too large subtree request, or the inability of the
publisher push update records as frequently as requested. In such
cases, no subscription is established. Instead, the subscription-
result with the failure reason is returned as part of the RPC
response. As part of this response, a set of alternative
subscription parameters MAY be returned that would likely have
resulted in acceptance of the subscription request. The subscriber
may consider these as part of future subscription attempts.
For instance, for the following request:
<netconf:rpc message-id="101"
xmlns:netconf="urn:ietf:params:xml:ns:netconf:base:1.0">
<establish-subscription
xmlns="urn:ietf:params:xml:ns:yang:ietf-subscribed-notifications"
xmlns:yp="urn:ietf:params:xml:ns:yang:ietf-yang-push">
<yp:datastore>
<yp:source xmlns="urn:ietf:params:xml:ns:yang:ietf-datastores">
operational
</yp:source>
<yp:subtree-filter netconf:type="xpath"
xmlns:ex="http://example.com/sample-data/1.0"
select="/ex:foo"/>
</yp:datastore>
<yp:period>500</yp:period>
</establish-subscription>
</netconf:rpc>
Figure 3: Establish-Subscription example
the publisher might return:
Clemm, et al. Expires April 28, 2018 [Page 12]
Internet-Draft YANG-Push October 2017
<rpc-reply message-id="101"
xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
<subscription-result
xmlns="urn:ietf:params:xml:ns:yang:ietf-subscribed-notifications"
xmlns:yp="urn:ietf:params:xml:ns:yang:ietf-yang-push">
yp:period-unsupported
</subscription-result>
<period-hint xmlns:"urn:ietf:params:xml:ns:yang:ietf-yang-push">
2000
</period-hint>
</rpc-reply>
Figure 4: Error response example
As can be seen above the rejected subscription does not result in the
generation of an rpc-reply with an rpc-error element. YANG-push
specific errors and negotiation hints part are returned as part of
normal RPC operations.
3.9. Receiver Authorization
A receiver of subscription data MUST only be sent updates for which
they have proper authorization. A publisher MUST ensure that no non-
authorized data is included in push updates. To do so, it needs to
apply all corresponding checks applicable at the time of a specific
pushed update and if necessary silently remove any non-authorized
data from subtrees. This enables YANG data pushed based on
subscriptions to be authorized equivalently to a regular data
retrieval (get) operation.
A publisher MAY allow subscriptions which select non-existent or
access-protected data. Such a capability permits a receiver the
ability to monitor the entire lifecyle of the data. In this case,
all push-updates must be sent empty, and no push-change-updates will
be sent until the data becomes visible for a receiver.
A publisher MAY alternatively choose not to allow subscriptions which
select non-existent or access-protected data. Such a capability
enables the publisher to avoid having to perform filtering of
authorized content on each update. Relevant scenarios here include:
o the rejecting of a subscription request to access-protected
objects,
o the suspension of a subscription where new access-controlled
objects are selected mid-subscription for which the receiver does
not have the necessary authorization, or
Clemm, et al. Expires April 28, 2018 [Page 13]
Internet-Draft YANG-Push October 2017
o the authorization privileges of a receiver change over the course
of the subscription.
In all these cases, the error identity "data-unavailable" SHOULD be
returned. This reduces the possibility of access permission leakage.
The contextual authorization model for data in YANG datastores is the
NETCONF Access Control Model [RFC6536bis], Section 3.2.4. A
clarification to this is that each of the individual nodes in a
resulting update record MUST also have applied access control to
resulting pushed messages. This includes validating that read access
is ok for any nodes newly selected since the last update record for
each receiver.
+-------------+ +-------------------+
push-update / --> | data node | yes | |
push-change-update | access | ---> | add data node |
| allowed? | | to update message |
+-------------+ +-------------------+
Figure 5: Access control for push updates
If read access into previously accessible nodes has been lost due to
a receiver permissions change, this SHOULD be reported as node
'delete' operations for on-change subscriptions. If not capable of
handling such receiver permission changes with such a 'delete',
publisher implementations MUST force dynamic subscription re-
establishment or configured subscription re-initialization so that
appropriate filtering is installed.
3.10. On-change Notifiable YANG objects
In some cases, a publisher supporting on-change notifications may not
be able to push updates for some object types on-change. Reasons for
this might be that the value of the data node changes frequently
(e.g., [RFC7223]'s in-octets counter), that small object changes are
frequent and meaningless (e.g., a temperature gauge changing 0.1
degrees), or that the implementation is not capable of on-change
notification for a particular object.
Support for on-change notification is usually specific to the
individual YANG model and/or implementation so it is possible to
define in design time. System integrators need this information
(without reading any data from a live node).
The default assumption is that no data nodes support on-change
notification. Schema nodes and subtrees that support on-change
notifications MUST be marked by accordingly with the YANG extension
Clemm, et al. Expires April 28, 2018 [Page 14]
Internet-Draft YANG-Push October 2017
"notifiable-on-change". This extension is defined in the data model
below.
When an on-change subscription is established, data-nodes are
automatically excluded unless they are marked with notifiable-on-
change as true. This also means that authorization checks SHALL NOT
be performed on them. A subscriber can identify which nodes may be
included in on-change updates by retrieving the data nodes in the
subscription's scope and checking for which notifiable-on-change is
marked as true.
In theory, adding notifiable-on-change markings can be done within
corresponding YANG models. But a more extensible way to avoid having
to modify existing module definitions is to add notifiable-on-change
markings within separate module deviations. This means that when a
YANG model designer wants to add a notifiable-on-change marking to
nodes of an existing module without modifying the module definitions,
a new module is introduced that contains deviation statements which
add "notifiable-on-change" statements as applicable.
deviation /sys:system/sys:system-time {
deviate add {
yp:notifiable-on-change false;
}
}
Figure 6: Deviation Example
3.11. Other Considerations
3.11.1. Robustness and reliability
Particularly in the case of on-change push updates, it is important
that push updates do not get lost or, in case the loss of an update
is unavoidable, that the receiver is notified accordingly.
Update messages for a single subscription MAY NOT be resequenced.
It is conceivable that under certain circumstances, a publisher will
recognize that it is unable to include within an update record the
full set of objects desired per the terms of a subscription. In this
case, the publisher MUST take one or more of the following actions.
o A publisher MUST set the updates-not-sent flag on any update
record which is known to be missing information.
o It MAY choose to suspend a subscription as per
[I-D.draft-ietf-netconf-subscribed-notifications].
Clemm, et al. Expires April 28, 2018 [Page 15]
Internet-Draft YANG-Push October 2017
o When resuming an on-change subscription, the publisher SHOULD
generate a complete patch from the previous update record. If
this is not possible and the synch-on-start option is configured,
then the full datastore contents MAY be sent via a push-update
instead (effectively replacing the previous contents). If neither
of these are possible, then an updates-not-sent flag MUST be
included on the next push-change-update.
Note: It is perfectly acceptable to have a series of push-change-
updates (and even push updates) serially queued at the transport
layer awaiting transmission. It is not required to merge pending
update messages. I.e., the dampening period applies to update record
creation, not transmission.
3.11.2. Publisher capacity
It is far preferable to decline a subscription request than to accept
such a request when it cannot be met.
Whether or not a subscription can be supported will be determined by
a combination of several factors such as the subscription trigger
(on-change or periodic), the period in which to report changes (1
second periods will consume more resources than 1 hour periods), the
amount of data in the subtree that is being subscribed to, and the
number and combination of other subscriptions that are concurrently
being serviced.
4. A YANG data model for management of datastore push subscriptions
4.1. Overview
The YANG data model for datastore push subscriptions is depicted in
the following figure. Following YANG tree convention in the
depiction, brackets enclose list keys, "rw" means configuration, "ro"
operational state data, "?" designates optional nodes, "*" designates
nodes that can have multiple instances. Parentheses with a name in
the middle enclose choice and case nodes. New YANG objects defined
here (i.e., beyond those from
[I-D.draft-ietf-netconf-subscribed-notifications]) are identified
with "yp".
module: ietf-subscribed-notifications
+--ro streams
| +--ro stream* [name]
| +--ro name stream
| +--ro description string
| +--ro replay-support? empty {replay}?
| +--ro replay-log-creation-time? yang:date-and-time {replay}?
Clemm, et al. Expires April 28, 2018 [Page 16]
Internet-Draft YANG-Push October 2017
| +--ro replay-log-aged-time? yang:date-and-time {replay}?
+--rw filters
| +--rw stream-filter* [identifier]
| | +--rw identifier filter-id
| | +--rw (filter-spec)?
| | +--:(subtree-filter)
| | | +--rw subtree-filter? {subtree}?
| | +--:(xpath-filter)
| | +--rw xpath-filter? yang:xpath1.0 {xpath}?
| +--rw yp:selection-filter* [identifier]
| +--rw yp:identifier sn:filter-id
| +--rw (yp:filter-spec)?
| +--:(yp:subtree-filter)
| | +--rw yp:subtree-filter? {sn:subtree}?
| +--:(yp:xpath-filter)
| +--rw yp:xpath-filter? yang:xpath1.0 {sn:xpath}?
+--rw subscription-config {configured}?
| +--rw subscription* [identifier]
| +--rw identifier subscription-id
| +--rw encoding encoding
| +--rw (target)
| | +--:(stream)
| | | +--rw (stream-filter)?
| | | | +--:(by-reference)
| | | | | +--rw stream-filter-ref stream-filter-ref
| | | | +--:(within-subscription)
| | | | +--rw (filter-spec)?
| | | | +--:(subtree-filter)
| | | | | +--rw subtree-filter? {subtree}?
| | | | +--:(xpath-filter)
| | | | +--rw xpath-filter? yang:xpath1.0{sn:xpath}?
| | | +--rw stream stream
| | | +--rw replay-start-time? yang:date-and-time {replay}?
| | +--:(yp:datastore)
| | +--rw yp:source identityref
| | +--rw (yp:selected-content)?
| | +--:(yp:by-reference)
| | | +--rw yp:selection-filter-ref selection-filter-ref
| | +--:(yp:within-subscription)
| | +--rw (yp:filter-spec)?
| | +--:(yp:subtree-filter)
| | | +--rw yp:subtree-filter? {sn:subtree}?
| | +--:(yp:xpath-filter)
| | +--rw yp:xpath-filter
| | yang:xpath1.0{sn:xpath}?
| +--rw stop-time? yang:date-and-time
| +--rw receivers
| | +--rw receiver* [address port]
Clemm, et al. Expires April 28, 2018 [Page 17]
Internet-Draft YANG-Push October 2017
| | +--rw address inet:host
| | +--rw port inet:port-number
| | +--rw protocol transport
| | +--rw status? enumeration
| +--rw (notification-message-origin)?
| | +--:(interface-originated)
| | | +--rw source-interface? if:interface-ref
| | +--:(address-originated)
| | +--rw source-vrf? string
| | +--rw source-address? inet:ip-address-no-zone
| +--rw (yp:update-trigger)?
| | +--:(yp:periodic)
| | | +--rw yp:period yang:timeticks
| | | +--rw yp:anchor-time? yang:date-and-time
| | +--:(yp:on-change) {on-change}?
| | +--rw yp:dampening-period yang:timeticks
| | +--rw yp:no-synch-on-start? empty
| | +--rw yp:excluded-change* change-type
| +--rw yp:dscp? inet:dscp
| +--rw yp:weighting? uint8
| +--rw yp:dependency? sn:subscription-id
+--ro subscriptions
+--ro subscription* [identifier]
+--ro identifier subscription-id
+--ro configured-subscription? empty {configured}?
+--ro encoding encoding
+--ro (target)
| +--:(stream)
| | +--ro (stream-filter)?
| | | +--:(by-reference)
| | | | +--ro stream-filter-ref stream-filter-ref
| | | +--:(within-subscription)
| | | +--ro (filter-spec)?
| | | +--:(subtree-filter)
| | | | +--ro subtree-filter? {subtree}?
| | | +--:(xpath-filter)
| | | +--ro xpath-filter? yang:xpath1.0{sn:xpath}?
| | +--ro stream stream
| | +--ro replay-start-time? yang:date-and-time {replay}?
| +--:(yp:datastore)
| +--ro yp:source identityref
| +--ro (yp:selected-content)?
| +--:(yp:by-reference)
| | +--ro yp:selection-filter-ref selection-filter-ref
| +--:(yp:within-subscription)
| +--ro (yp:filter-spec)?
| +--:(yp:subtree-filter)
| | +--ro yp:subtree-filter? {sn:subtree}?
Clemm, et al. Expires April 28, 2018 [Page 18]
Internet-Draft YANG-Push October 2017
| +--:(yp:xpath-filter)
| +--ro yp:xpath-filter?
| yang:xpath1.0 {sn:xpath}?
+--ro stop-time? yang:date-and-time
+--ro (notification-message-origin)?
| +--:(interface-originated)
| | +--ro source-interface? if:interface-ref
| +--:(address-originated)
| +--ro source-vrf? string
| +--ro source-address? inet:ip-address-no-zone
+--ro receivers
| +--ro receiver* [address port]
| +--ro address inet:host
| +--ro port inet:port-number
| +--ro protocol transport
| +--ro pushed-notifications? yang:counter64
| +--ro excluded-notifications? yang:counter64
| +--ro status enumeration
+--ro (yp:update-trigger)?
| +--:(yp:periodic)
| | +--ro yp:period yang:timeticks
| | +--ro yp:anchor-time? yang:date-and-time
| +--:(yp:on-change) {on-change}?
| +--ro yp:dampening-period yang:timeticks
| +--ro yp:no-synch-on-start? empty
| +--ro yp:excluded-change* change-type
+--ro yp:dscp? inet:dscp
+--ro yp:weighting? uint8
+--ro yp:dependency? sn:subscription-id
rpcs:
+---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)?
| | | | | +--:(subtree-filter)
| | | | | | +---w subtree-filter? {subtree}?
| | | | | +--:(xpath-filter)
| | | | | +---w xpath-filter? yang:xpath1.0 {xpath}?
| | | | +---w stream stream
| | | | +---w replay-start-time? yang:date-and-time {replay}?
| | | +--:(yp:datastore)
Clemm, et al. Expires April 28, 2018 [Page 19]
Internet-Draft YANG-Push October 2017
| | | +---w yp:source identityref
| | | +---w (yp:selected-content)?
| | | +--:(yp:by-reference)
| | | | +---w yp:selection-filter-ref selection-filter-ref
| | | +--:(yp:within-subscription)
| | | +---w (yp:filter-spec)?
| | | +--:(yp:subtree-filter)
| | | | +---w yp:subtree-filter? {sn:subtree}?
| | | +--:(yp:xpath-filter)
| | | +---w yp:xpath-filter?
| | | yang:xpath1.0 {sn:xpath}?
| | +---w stop-time? yang:date-and-time
| | +---w (yp:update-trigger)?
| | | +--:(yp:periodic)
| | | | +---w yp:period yang:timeticks
| | | | +---w yp:anchor-time? yang:date-and-time
| | | +--:(yp:on-change) {on-change}?
| | | +---w yp:dampening-period yang:timeticks
| | | +---w yp:no-synch-on-start? empty
| | | +---w yp:excluded-change* change-type
| | +---w yp:dscp? inet:dscp
| | +---w yp:weighting? uint8
| | +---w yp:dependency? sn:subscription-id
| +--ro output
| +--ro subscription-result subscription-result
| +--ro (result)?
| +--:(no-success)
| | +--ro filter-failure? string
| | +--ro replay-start-time-hint? yang:date-and-time
| | +--ro yp:period-hint? yang:timeticks
| | +--ro yp:error-path? string
| | +--ro yp:object-count-estimate? uint32
| | +--ro yp:object-count-limit? uint32
| | +--ro yp:kilobytes-estimate? uint32
| | +--ro yp:kilobytes-limit? uint32
| +--:(success)
| +--ro identifier subscription-id
+---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)?
| | | | +--:(subtree-filter)
Clemm, et al. Expires April 28, 2018 [Page 20]
Internet-Draft YANG-Push October 2017
| | | | | +---w subtree-filter? {subtree}?
| | | | +--:(xpath-filter)
| | | | +---w xpath-filter? yang:xpath1.0 {xpath}?
| | | +--:(yp:datastore)
| | | +---w (yp:selected-content)?
| | | +--:(yp:by-reference)
| | | | +---w yp:selection-filter-ref selection-filter-ref
| | | +--:(yp:within-subscription)
| | | +---w (yp:filter-spec)?
| | | +--:(yp:subtree-filter)
| | | | +---w yp:subtree-filter? {sn:subtree}?
| | | +--:(yp:xpath-filter)
| | | +---w yp:xpath-filter?
| | | yang:xpath1.0 {sn:xpath}?
| | +---w stop-time? yang:date-and-time
| | +---w (yp:update-trigger)?
| | +--:(yp:periodic)
| | | +---w yp:period yang:timeticks
| | | +---w yp:anchor-time? yang:date-and-time
| | +--:(yp:on-change) {on-change}?
| | +---w yp:dampening-period yang:timeticks
| +--ro output
| +--ro subscription-result subscription-result
| +--ro (result)?
| +--:(no-success)
| +--ro filter-failure? string
| +--ro yp:period-hint? yang:timeticks
| +--ro yp:error-path? string
| +--ro yp:object-count-estimate? uint32
| +--ro yp:object-count-limit? uint32
| +--ro yp:kilobytes-estimate? uint32
| +--ro yp:kilobytes-limit? uint32
+---x delete-subscription
| +---w input
| | +---w identifier subscription-id
| +--ro output
| +--ro subscription-result subscription-result
+---x kill-subscription
+---w input
| +---w identifier subscription-id
+--ro output
+--ro subscription-result subscription-result
notifications:
+---n replay-completed {replay}?
| +--ro identifier subscription-id
+---n subscription-completed
| +--ro identifier subscription-id
Clemm, et al. Expires April 28, 2018 [Page 21]
Internet-Draft YANG-Push October 2017
+---n subscription-started {configured}?
| +--ro identifier subscription-id
| +--ro encoding encoding
| +--ro (target)
| | +--:(stream)
| | | +--ro (stream-filter)?
| | | | +--:(by-reference)
| | | | | +--ro stream-filter-ref stream-filter-ref
| | | | +--:(within-subscription)
| | | | +--ro (filter-spec)?
| | | | +--:(subtree-filter)
| | | | | +--ro subtree-filter? {subtree}?
| | | | +--:(xpath-filter)
| | | | +--ro xpath-filter? yang:xpath1.0 {xpath}?
| | | +--ro stream stream
| | | +--ro replay-start-time? yang:date-and-time {replay}?
| | +--:(yp:datastore)
| | +--ro yp:source identityref
| | +--ro (yp:selected-content)?
| | +--:(yp:by-reference)
| | | +--ro yp:selection-filter-ref selection-filter-ref
| | +--:(yp:within-subscription)
| | +--ro (yp:filter-spec)?
| | +--:(yp:subtree-filter)
| | | +--ro yp:subtree-filter? {sn:subtree}?
| | +--:(yp:xpath-filter)
| | +--ro yp:xpath-filter? yang:xpath1.0{sn:xpath}?
| +--ro stop-time? yang:date-and-time
| +--ro (yp:update-trigger)?
| | +--:(yp:periodic)
| | | +--ro yp:period yang:timeticks
| | | +--ro yp:anchor-time? yang:date-and-time
| | +--:(yp:on-change) {on-change}?
| | +--ro yp:dampening-period yang:timeticks
| | +--ro yp:no-synch-on-start? empty
| | +--ro yp:excluded-change* change-type
| +--ro yp:dscp? inet:dscp
| +--ro yp:weighting? uint8
| +--ro yp:dependency? sn:subscription-id
+---n subscription-resumed
| +--ro identifier subscription-id
+---n subscription-modified {configured}?
| +--ro identifier subscription-id
| +--ro encoding encoding
| +--ro (target)
| | +--:(stream)
| | | +--ro (stream-filter)?
| | | | +--:(by-reference)
Clemm, et al. Expires April 28, 2018 [Page 22]
Internet-Draft YANG-Push October 2017
| | | | | +--ro stream-filter-ref stream-filter-ref
| | | | +--:(within-subscription)
| | | | +--ro (filter-spec)?
| | | | +--:(subtree-filter)
| | | | | +--ro subtree-filter? {subtree}?
| | | | +--:(xpath-filter)
| | | | +--ro xpath-filter? yang:xpath1.0 {xpath}?
| | | +--ro stream stream
| | | +--ro replay-start-time? yang:date-and-time {replay}?
| | +--:(yp:datastore)
| | +--ro yp:source identityref
| | +--ro (yp:selected-content)?
| | +--:(yp:by-reference)
| | | +--ro yp:selection-filter-ref selection-filter-ref
| | +--:(yp:within-subscription)
| | +--ro (yp:filter-spec)?
| | +--:(yp:subtree-filter)
| | | +--ro yp:subtree-filter? {sn:subtree}?
| | +--:(yp:xpath-filter)
| | +--ro yp:xpath-filter? yang:xpath1.0{sn:xpath}?
| +--ro stop-time? yang:date-and-time
| +--ro (yp:update-trigger)?
| | +--:(yp:periodic)
| | | +--ro yp:period yang:timeticks
| | | +--ro yp:anchor-time? yang:date-and-time
| | +--:(yp:on-change) {on-change}?
| | +--ro yp:dampening-period yang:timeticks
| | +--ro yp:no-synch-on-start? empty
| | +--ro yp:excluded-change* change-type
| +--ro yp:dscp? inet:dscp
| +--ro yp:weighting? uint8
| +--ro yp:dependency? sn:subscription-id
+---n subscription-terminated
| +--ro identifier subscription-id
| +--ro error-id subscription-errors
| +--ro filter-failure? string
+---n subscription-suspended
+--ro identifier subscription-id
+--ro error-id subscription-errors
+--ro filter-failure? string
module: ietf-yang-push
rpcs:
+---x resynch-subscription {on-change}?
+---w input
| +---w identifier sn:subscription-id
+--ro output
+--ro subscription-result sn:subscription-result
Clemm, et al. Expires April 28, 2018 [Page 23]
Internet-Draft YANG-Push October 2017
notifications:
+---n push-update
| +--ro subscription-id? sn:subscription-id
| +--ro time-of-update? yang:date-and-time
| +--ro updates-not-sent? empty
| +--ro datastore-contents?
+---n push-change-update {on-change}?
+--ro subscription-id? sn:subscription-id
+--ro time-of-update? yang:date-and-time
+--ro updates-not-sent? empty
+--ro datastore-changes?
Figure 7: Model structure
Selected components of the model are summarized below.
4.2. Subscription configuration
Both configured and dynamic subscriptions are represented within the
list subscription. But only configured subscriptions are listed
within list subscription-config. In both lists, each subscription
has own list elements. New and enhanced parameters extending the
basic subscription data model in
[I-D.draft-ietf-netconf-subscribed-notifications] include:
o The targeted datastore from which the selection is being made.
The potential datastores include those from
[I.D.draft-ietf-netmod-revised-datastores]. A platform may also
choose to support a custom datastore.
o A selection filter identifying yang nodes of interest within a
datastore. Filter contents are specified via a reference to an
existing filter, or via an in-line definition for only that
subscription. Referenced filters allows an implementation to
avoid evaluating filter acceptability during a dynamic
subscription request. The case statement differentiates the
options.
o For periodic subscriptions, triggered updates will occur at the
boundaries of a specified time interval. These boundaries many be
calculated from the periodic parameters:
* a "period" which defines duration between period push updates.
* an "anchor-time"; update intervals always fall on the points in
time that are a multiple of a period from an anchor time. If
Clemm, et al. Expires April 28, 2018 [Page 24]
Internet-Draft YANG-Push October 2017
anchor time is not provided, then the anchor time MUST be set
with the creation time of the initial update record.
o For on-change subscriptions, assuming the dampening period has
completed, triggering occurs whenever a change in the subscribed
information is detected. On-change subscriptions have more
complex semantics that is guided by its own set of parameters:
* a "dampening-period" specifies the interval that must pass
before a successive update for the subscription is sent. If no
dampening period is in effect, the update is sent immediately.
If a subsequent change is detected, another update is only sent
once the dampening period has passed for this subscription.
* an "excluded-change" flag which allows restriction of the types
of changes for which updates should be sent (e.g., only add to
an update record on object creation).
* a "no-synch-on-start" flag which specifies whether a complete
update with all the subscribed data is to be sent at the
beginning of a subscription.
o Optional QoS parameters to indicate the treatment of a
subscription relative to other traffic between publisher and
receiver. These include:
* A "dscp" QoS marking which MUST be stamped on notification
messages to differentiate network QoS behavior.
* A "weighting" so that bandwidth proportional to this weighting
can be allocated to this subscription relative to other
subscriptions destined for that receiver.
* a "dependency" upon another subscription. Notification
messages MUST NOT be sent prior to other notification messages
containing update record(s) for the referenced subscription.
o A subscription's weighting MUST work identically to stream
dependency weighting as described within RFC 7540, section 5.3.2.
o A subscription's dependency MUST work identically to stream
dependency as described within RFC 7540, 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
removed.
Clemm, et al. Expires April 28, 2018 [Page 25]
Internet-Draft YANG-Push October 2017
4.3. YANG Notifications
4.3.1. State Change Notifications
Subscription state notifications and mechanism are reused from
[I-D.draft-ietf-netconf-subscribed-notifications]. Some have been
augmented to include the YANG datastore specific objects.
4.3.2. Notifications for Subscribed Content
Along with the subscribed content, there are other objects which
might be part of a push-update or push-change-update
A subscription-id MUST be transported along with the subscribed
contents. An [RFC5277] Section 4 one-way notification MAY be used
for encoding updates. Where it is, the relevant subscription-id MUST
be encoded as the first element within each push-update or push-
change-update. This allows a receiver to differentiate which
subscription resulted in a particular push.
A "time-of-update" which represents the time an update record
snapshot was generated. A receiver MAY assume that a publisher's
objects have these pushed values at this point in time.
An "updates-not-sent" object, which indicates that the update record
is incomplete. If the application detects an informational
discontinuity in either notification, the notification message MUST
include "updates-not-sent". This object indicates that not all
changes which have occurred since the last update are actually
included with this update. In other words, the publisher has failed
to fulfill its full subscription obligations. (For example a
datastore missed a window in providing objects to a publisher
process.) To facilitate re-synchronization of on-change
subscriptions, a publisher MAY subsequently send a push-update
containing a full selection snapshot of subscribed data.
4.4. YANG RPCs
YANG-Push subscriptions are established, modified, and deleted using
RPCs augmented from
[I-D.draft-ietf-netconf-subscribed-notifications].
4.4.1. Establish-subscription RPC
The subscriber sends an establish-subscription RPC with the
parameters in section 3.1. An example might look like:
Clemm, et al. Expires April 28, 2018 [Page 26]
Internet-Draft YANG-Push October 2017
<netconf:rpc message-id="101"
xmlns:netconf="urn:ietf:params:xml:ns:netconf:base:1.0">
<establish-subscription
xmlns="urn:ietf:params:xml:ns:yang:ietf-subscribed-notifications"
xmlns:yp="urn:ietf:params:xml:ns:yang:ietf-yang-push">
<yp:datastore>
<yp:source xmlns="urn:ietf:params:xml:ns:yang:ietf-datastores">
operational
</yp:source>
<xpath-filter
xmlns:ex="http://example.com/sample-data/1.0"
select="/ex:foo"/>
</yp:datastore>
<yp:period>500</yp:period>
</establish-subscription>
</netconf:rpc>
Figure 8: Establish-subscription RPC
The publisher MUST respond explicitly positively (i.e., subscription
accepted) or negatively (i.e., subscription rejected) to the request.
Positive responses include the identifier of the accepted
subscription. In that case a publisher MAY respond:
<rpc-reply message-id="101"
xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
<subscription-result
xmlns="urn:ietf:params:xml:ns:yang:ietf-subscribed-notifications">
ok
</subscription-result>
<identifier
xmlns="urn:ietf:params:xml:ns:yang:ietf-subscribed-notifications">
52
</identifier>
</rpc-reply>
Figure 9: Establish-subscription positive RPC response
A subscription can be rejected for multiple reasons, including the
lack of authorization to establish a subscription, no capacity to
serve the subscription at the publisher, or the inability of the
publisher to select datastore content at the requested cadence.
If a request is rejected because the publisher is not able to serve
it, the publisher SHOULD include in the returned error hints ar what
subscription parameters might have been accepted for the request.
However, there are no guarantee that subsequent requests using this
info will in fact be accepted.
Clemm, et al. Expires April 28, 2018 [Page 27]
Internet-Draft YANG-Push October 2017
For example, for the following request:
<netconf:rpc message-id="101"
xmlns:netconf="urn:ietf:params:xml:ns:netconf:base:1.0">
<establish-subscription
xmlns="urn:ietf:params:xml:ns:yang:ietf-subscribed-notifications"
xmlns:yp="urn:ietf:params:xml:ns:yang:ietf-yang-push">
<yp:datastore>
<yp:source xmlns="urn:ietf:params:xml:ns:yang:ietf-datastores">
operational
</yp:source>
<yp:xpath-filter
xmlns:ex="http://example.com/sample-data/1.0"
select="/ex:foo"/>
</yp:datastore>
<yp:dampening-period>10</yp:dampening-period>
</establish-subscription>
</netconf:rpc>
Figure 10: Establish-subscription request example 2
a publisher that cannot serve on-change updates but periodic updates
might return the following:
<rpc-reply message-id="101"
xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
<subscription-result
xmlns="urn:ietf:params:xml:ns:yang:ietf-subscribed-notifications"
xmlns:yp="urn:ietf:params:xml:ns:yang:ietf-yang-push">
yp:period-unsupported
</subscription-result>
<period-hint xmlns:"urn:ietf:params:xml:ns:yang:ietf-yang-push">
100
</period-hint>
</rpc-reply>
Figure 11: Establish-subscription error response example 2
4.4.2. Modify-subscription RPC
The subscriber MAY invoke the modify-subscription RPC for a
subscription it previously established. The subscriber will include
newly desired values in the modify-subscription RPC. Parameters not
included MUST remain unmodified. Below is an example where a
subscriber attempts to modify the period of a subscription.
Clemm, et al. Expires April 28, 2018 [Page 28]
Internet-Draft YANG-Push October 2017
<netconf:rpc message-id="102"
xmlns:netconf="urn:ietf:params:xml:ns:netconf:base:1.0">
<modify-subscription
xmlns="urn:ietf:params:xml:ns:yang:ietf-subscribed-notifications"
xmlns: yp="urn:ietf:params:xml:ns:yang:ietf-yang-push">
<yp:datastore>
<yp:source xmlns="urn:ietf:params:xml:ns:yang:ietf-datastores">
operational
</yp:source>
<xpath-filter
xmlns:ex="http://example.com/sample-data/1.0"
select="/ex:bar"/>
</yp:datastore>
<identifier>
1011
</identifier>
<yp:period>250</yp:period>
</modify-subscription>
</netconf:rpc>
Figure 12: Modify subscription request
The publisher MUST respond explicitly positively or negatively to the
request. A response to a successful modification might look like:
<rpc-reply message-id="102"
xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
<subscription-result
xmlns="urn:ietf:params:xml:ns:yang:ietf-subscribed-notifications">
ok
</subscription-result>
</rpc-reply>
Figure 13: Modify subscription response
If the subscription modification is rejected, the publisher MUST send
a response like it does for an establish-subscription and maintain
the subscription as it was before the modification request.
Responses MAY include hints. A subscription MAY be modified multiple
times.
A configured subscription cannot be modified using modify-
subscription RPC. Instead, the configuration needs to be edited as
needed.
Clemm, et al. Expires April 28, 2018 [Page 29]
Internet-Draft YANG-Push October 2017
4.4.3. Delete-subscription RPC
To stop receiving updates from a subscription and effectively delete
a subscription that had previously been established using an
establish-subscription RPC, a subscriber can send a delete-
subscription RPC, which takes as only input the subscription's
identifier.
Configured subscriptions cannot be deleted via RPC, but have to be
removed from the configuration. This RPC is identical to the RPC
from [I-D.draft-ietf-netconf-subscribed-notifications].
4.4.4. Resynch-subscription RPC
This RPC is only applicable only for on-change subscriptions
previously been established using an establish-subscription RPC. On
receipt, a publisher must either reply 'ok' and quickly follow with a
push-update, or send an appropriate error such as on-change-synch-
unsupported. For example:
<netconf:rpc message-id="103"
xmlns:netconf="urn:ietf:params:xml:ns:netconf:base:1.0">
<resynch-subscription
xmlns="urn:ietf:params:xml:ns:yang:ietf-yang-push">
xmlns:sn="urn:ietf:params:xml:ns:yang:ietf-subscribed-notifications">
<sn:identifier>
1011
</sn:identifier>
</resynch-subscription>
</netconf:rpc>
<rpc-reply message-id="103"
xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
<subscription-result
xmlns="urn:ietf:params:xml:ns:yang:ietf-subscribed-notifications">
ok
</subscription-result>
</rpc-reply>
Resynch subscription
4.4.5. YANG Module Synchronization
To make subscription requests, the subscriber needs to know the YANG
module library available on the publisher. The YANG 1.0 module
library information is sent by a NETCONF server in the NETCONF
'hello' message. For YANG 1.1 modules and all modules used with the
RESTCONF [RFC8040] protocol, this information is provided by the YANG
Clemm, et al. Expires April 28, 2018 [Page 30]
Internet-Draft YANG-Push October 2017
Library module (ietf-yang-library.yang from [RFC7895]. This YANG
library information is important for the receiver to reproduce the
set of object definitions used within the publisher.
The YANG library includes a module list with the name, revision,
enabled features, and applied deviations for each YANG module
implemented by the publisher. The receiver is expected to know the
YANG library information before starting a subscription. The
"/modules-state/module-set-id" leaf in the "ietf-yang-library" module
can be used to cache the YANG library information.
The set of modules, revisions, features, and deviations can change at
run-time (if supported by the publisher implementation). In this
case, the receiver needs to be informed of module changes before data
nodes from changed modules can be processed correctly. The YANG
library provides a simple "yang-library-change" notification that
informs the subscriber that the library has changed. The receiver
then needs to re-read the entire YANG library data for the replicated
publisher in order to detect the specific YANG library changes. The
"ietf-netconf-notifications" module defined in [RFC6470] contains a
"netconf-capability-change" notification that can identify specific
module changes. For example, the module URI capability of a newly
loaded module will be listed in the "added-capability" leaf-list, and
the module URI capability of an removed module will be listed in the
"deleted-capability" leaf-list.
5. YANG module
<CODE BEGINS>; file "ietf-yang-push.yang"
module ietf-yang-push {
yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang:ietf-yang-push";
prefix yp;
import ietf-inet-types {
prefix inet;
}
import ietf-yang-types {
prefix yang;
}
import ietf-subscribed-notifications {
prefix sn;
}
import ietf-datastores {
prefix ds;
}
organization "IETF";
Clemm, et al. Expires April 28, 2018 [Page 31]
Internet-Draft YANG-Push October 2017
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: Ambika Prasad Tripathy
<mailto:ambtripa@cisco.com>
Editor: Einar Nilsen-Nygaard
<mailto:einarnn@cisco.com>
Editor: Andy Bierman
<mailto:andy@yumaworks.com>
Editor: Balazs Lengyel
<mailto:balazs.lengyel@ericsson.com>";
description
"This module contains conceptual YANG specifications
for YANG push.";
revision 2017-10-23 {
description
"Initial revision.";
reference
"YANG Datastore Push, draft-ietf-netconf-yang-push-11";
}
/*
* EXTENSIONS
*/
extension notifiable-on-change {
argument "value";
description
"Indicates whether changes to the data node are reportable in
on-change subscriptions.
The statement MUST only be a substatement of the leaf, leaf-list,
container, list, anyxml, anydata statements. Zero or One
Clemm, et al. Expires April 28, 2018 [Page 32]
Internet-Draft YANG-Push October 2017
notifiable-on-change statement is allowed per parent statement.
NO substatements are allowed.
The argument is a boolean value indicating whether on-change
notifications are supported. If notifiable-on-change is not
specified, the default is the same as the parent data node's
value. For top level data nodes the default value is false.";
}
/*
* FEATURES
*/
feature on-change {
description
"This feature indicates that on-change triggered subscriptions
are supported.";
}
/*
* IDENTITIES
*/
/* Error type identities for datastore subscription */
identity period-unsupported {
base sn:error;
description
"Requested time period is too short. This can be for both
periodic and on-change dampening.";
}
identity qos-unsupported {
base sn:error;
description
"Subscription QoS parameters not supported on this platform.";
}
identity dscp-unavailable {
base sn:error;
description
"Requested DSCP marking not allocatable.";
}
identity on-change-unsupported {
base sn:error;
description
"On-change not supported.";
}
Clemm, et al. Expires April 28, 2018 [Page 33]
Internet-Draft YANG-Push October 2017
identity on-change-synch-unsupported {
base sn:error;
description
"On-change synch-on-start and resynchonization not supported.";
}
identity reference-mismatch {
base sn:error;
description
"Mismatch in filter key and referenced yang subtree.";
}
identity data-unavailable {
base sn:error;
description
"Referenced yang node or subtree doesn't exist, or read
access is not permitted.";
}
identity datatree-size {
base sn:error;
description
"Resulting periodic or on-change push updates may exceed a size
limit during normal conditions.";
}
identity synchronization-size {
base sn:error;
description
"The resulting Synch-on-start or resynchronization would push a
datatree which exceeds size limit for a one-time update.";
}
identity no-such-datastore {
base sn:error;
description
"This is not a subscribable datastore.";
}
/* Datastore identities */
identity custom-datastore {
base ds:datastore;
description
"A datastore with boundaries not defined within
draft-ietf-netmod-revised-datastores";
}
Clemm, et al. Expires April 28, 2018 [Page 34]
Internet-Draft YANG-Push October 2017
/*
* TYPE DEFINITIONS
*/
typedef change-type {
type enumeration {
enum "create" {
description
"Create a new data resource if it does not already exist. If
it already exists, replace.";
}
enum "delete" {
description
"Delete a data resource if it already exists. If it does not
exists, take no action.";
}
enum "insert" {
description
"Insert a new user-ordered data resource";
}
enum "merge" {
description
"merge the edit value with the target data resource; create
if it does not already exist";
}
enum "move" {
description
"Reorder the target data resource";
}
enum "replace" {
description
"Replace the target data resource with the edit value";
}
enum "remove" {
description
"Remove a data resource if it already exists ";
}
}
description
"Specifies different types of datastore changes.";
reference
"RFC 8072 section 2.5, with a delta that it is ok to receive
ability create on an existing node, or receive a delete on a
missing node.";
}
typedef selection-filter-ref {
type leafref {
Clemm, et al. Expires April 28, 2018 [Page 35]
Internet-Draft YANG-Push October 2017
path "/sn:filters/yp:selection-filter/yp:identifier";
}
description
"This type is used to reference a selection filter.";
}
/*
* GROUP DEFINITIONS
*/
grouping datastore-criteria {
description
"A grouping to define criteria for which selected objects from
a targeted datastore should be included in push updates.";
leaf source {
type identityref {
base ds:datastore;
}
mandatory true;
description
"Datastore from which to retrieve data.";
}
uses selection-filter-objects;
}
grouping selection-filter-types {
description
"This grouping defines a selector for objects from a
datastore.";
choice filter-spec {
description
"The content filter specification for this request.";
anydata subtree-filter {
description
"This parameter identifies the portions of the
target datastore to retrieve.";
reference "RFC 6241, Section 6.";
}
leaf xpath-filter {
type yang:xpath1.0;
description
"This parameter contains an XPath expression identifying the
portions of the target datastore to retrieve.";
reference "http://www.w3.org/TR/1999/REC-xpath-19991116";
}
}
}
Clemm, et al. Expires April 28, 2018 [Page 36]
Internet-Draft YANG-Push October 2017
grouping selection-filter-objects {
description
"This grouping defines a selector for objects from a
datastore.";
choice selected-content {
description
"The source of the selection filter applied to the subscription.
This will come either referenced from a global list, or be
provided within the subscription itself.";
case by-reference {
description
"Incorporate a filter that has been configured separately.";
leaf selection-filter-ref {
type selection-filter-ref;
mandatory true;
description
"References an existing selection filter which is to be
applied to the subscription.";
}
}
case within-subscription {
description
"Local definition allows a filter to have the same lifecycle
as the subscription.";
uses selection-filter-types;
}
}
}
grouping update-policy-modifiable {
description
"This grouping describes the datastore specific subscription
conditions that can be changed during the lifetime of the
subscription.";
choice update-trigger {
description
"Defines necessary conditions for sending an event record to
the subscriber.";
case periodic {
description
"The agent is requested to notify periodically the current
values of the datastore as defined by the selection filter.";
leaf period {
type yang:timeticks;
mandatory true;
description
"Duration of time which should occur between periodic
Clemm, et al. Expires April 28, 2018 [Page 37]
Internet-Draft YANG-Push October 2017
push updates. Where the anchor-time is
available, the push will include the objects and their
values which exist at an exact multiple of timeticks
aligning to this start-time anchor.";
}
leaf anchor-time {
type yang:date-and-time;
description
"Designates a timestamp before or after which a series of
periodic push updates are determined. The next update will
take place at a whole multiple interval from the anchor
time. For example, for an anchor time is set for the top
of a particular minute and a period interval of a minute,
updates will be sent at the top of every minute this
subscription is active.";
}
}
case on-change {
if-feature "on-change";
description
"The agent is requested to notify changes in values in the
datastore subset as defined by a selection filter.";
leaf dampening-period {
type yang:timeticks;
mandatory true;
description
"The shortest time duration which is allowed between the
creation of independent yang object update messages.
Effectively this is the amount of time that needs to have
passed since the last update. Zero indicates no delay.";
}
}
}
}
grouping update-policy {
description
"This grouping describes the datastore specific subscription
conditions of a subscription.";
uses update-policy-modifiable {
augment "update-trigger/on-change" {
description
"Includes objects not modifiable once subscription is
established.";
leaf no-synch-on-start {
type empty;
description
"The presence of this object restricts an on-change
Clemm, et al. Expires April 28, 2018 [Page 38]
Internet-Draft YANG-Push October 2017
subscription from sending push-update notifications. When
present, pushing a full selection per the terms of the
selection filter MAY NOT be done for this subscription.
Only updates about changes, i.e. only push-change-update
notifications are sent. When absent (default behavior),
in order to facilitate a receiver's synchronization, a full
update is sent when the subscription starts using a
push-update notification, just like in the case of a
periodic subscription. After that, push-change-update
notifications are exclusively sent unless the publisher
chooses to resynch the subscription via a new push-update
notification.";
}
leaf-list excluded-change {
type change-type;
description
"Use to restrict which changes trigger an update.
For example, if modify is excluded, only creation and
deletion of objects is reported.";
}
}
}
}
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 {
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 {
type uint8 {
range "0 .. 255";
}
description
"Relative weighting for a subscription. Allows an underlying
transport layer perform informed load balance allocations
between various subscriptions";
reference
"RFC-7540, section 5.3.2";
}
Clemm, et al. Expires April 28, 2018 [Page 39]
Internet-Draft YANG-Push October 2017
leaf dependency {
type sn: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 update-error-hints {
description
"Allow return additional negotiation hints that apply
specifically to push updates.";
leaf period-hint {
type yang:timeticks;
description
"Returned when the requested time period is too short. This
hint can assert an viable period for both periodic push
cadence and on-change dampening.";
}
leaf error-path {
type string;
description
"Reference to a YANG path which is associated with the error
being returned.";
}
leaf object-count-estimate {
type uint32;
description
"If there are too many objects which could potentially be
returned by the selection filter, this identifies the estimate
of the number of objects which the filter would potentially
pass.";
}
leaf object-count-limit {
type uint32;
description
"If there are too many objects which could be returned by the
selection filter, this identifies the upper limit of the
publisher's ability to service for this subscription.";
}
leaf kilobytes-estimate {
type uint32;
description
Clemm, et al. Expires April 28, 2018 [Page 40]
Internet-Draft YANG-Push October 2017
"If the returned information could be beyond the capacity of
the publisher, this would identify the data size which could
result from this selection filter.";
}
leaf kilobytes-limit {
type uint32;
description
"If the returned information would be beyond the capacity of
the publisher, this identifies the upper limit of the
publisher's ability to service for this subscription.";
}
}
/*
* RPCs
*/
rpc resynch-subscription {
if-feature "on-change";
description
"This RPC allows a subscriber of an active on-change
subscription to request a full push of objects in there current
state. A successful result would be the set of YANG objects
equivalent to a Get using the existing selection criteria. This
request may only come from the same subscriber using the
establish-subscription RPC.";
input {
leaf identifier {
type sn:subscription-id;
mandatory true;
description
"Identifier of the subscription that is to be resynched.";
}
}
output {
leaf subscription-result {
type sn:subscription-result;
mandatory true;
description
"Indicates whether the request for the subscription resynch
has been accepted, or why it has been denied.";
}
}
}
/*
* DATA NODES
*/
Clemm, et al. Expires April 28, 2018 [Page 41]
Internet-Draft YANG-Push October 2017
augment "/sn:establish-subscription/sn:input" {
description
"This augmentation adds additional subscription parameters that
apply specifically to datastore updates to RPC input.";
uses update-policy;
uses update-qos;
}
augment "/sn:establish-subscription/sn:input/sn:target" {
description
"This augmentation adds the datastore as a valid parameter object
for the subscription to RPC input. This provides a target for
the filter.";
case datastore {
uses datastore-criteria;
}
}
augment "/sn:establish-subscription/sn:output/"+
"sn:result/sn:no-success" {
description
"This augmentation adds datastore specific error info
and hints to RPC output.";
uses update-error-hints;
}
augment "/sn:modify-subscription/sn:input" {
description
"This augmentation adds additional subscription parameters
specific to datastore updates.";
uses update-policy-modifiable;
}
augment "/sn:modify-subscription/sn:input/sn:target" {
description
"This augmentation adds the datastore as a valid parameter object
for the subscription to RPC input. This provides a target for
the filter.";
case datastore {
uses selection-filter-objects;
}
}
augment "/sn:modify-subscription/sn:output/"+
"sn:result/sn:no-success" {
description
"This augmentation adds push datastore error info and hints to
RPC output.";
uses update-error-hints;
}
notification push-update {
description
Clemm, et al. Expires April 28, 2018 [Page 42]
Internet-Draft YANG-Push October 2017
"This notification contains a push update, containing data
subscribed to via a subscription. This notification is sent for
periodic updates, for a periodic subscription. It can also be
used for synchronization updates of an on-change subscription.
This notification shall only be sent to receivers of a
subscription; it does not constitute a general-purpose
notification.";
leaf subscription-id {
type sn:subscription-id;
description
"This references the subscription which drove the notification
to be sent.";
}
leaf time-of-update {
type yang:date-and-time;
description
"This leaf identifies the generation time of the datastore
selection within a push-update.";
}
leaf updates-not-sent {
type empty;
description
"This is a flag which indicates that not all data nodes
subscribed to are included with this update. In other words,
the publisher has failed to fulfill its full subscription
obligations. The result is intermittent loss of
synchronization of data at the receiver.";
}
anydata datastore-contents {
description
"This contains the updated data. It constitutes a snapshot
at the time-of-update of the set of data that has been
subscribed to. The format and syntax of the data
corresponds to the format and syntax of data that would be
returned in a corresponding get operation with the same
selection filter parameters applied.";
}
}
notification push-change-update {
if-feature "on-change";
description
"This notification contains an on-change push update. This
notification shall only be sent to the receivers of a
subscription; it does not constitute a general-purpose
notification.";
leaf subscription-id {
type sn:subscription-id;
Clemm, et al. Expires April 28, 2018 [Page 43]
Internet-Draft YANG-Push October 2017
description
"This references the subscription which drove the notification
to be sent.";
}
leaf time-of-update {
type yang:date-and-time;
description
"This leaf identifies the generation time of the datastore
changes extract. If a dampening-period was in effect before
the notification message was generated, this may not be the
time any of the datastore-changes were actually made.";
}
leaf updates-not-sent {
type empty;
description
"The presence of this object indicates not all changes which
have occurred since the last update are included with this
update. In other words, the publisher has failed to
fulfill its full subscription obligations, for example in
cases where it was not able to keep up with a change burst.";
}
anydata datastore-changes {
description
"This contains an incremental set of datastore changes needed
to update a remote datastore starting at the time of the
previous update, per the terms of the subscription. Changes
are encoded analogous to the syntax of a corresponding yang-
patch operation, i.e. a yang-patch operation applied to the
YANG datastore implied by the previous update to result in the
current state.";
reference
"RFC 8072 section 2.5, with a delta that it is ok to receive
ability create on an existing node, or receive a delete on a
missing node.";
}
}
augment "/sn:subscription-started" {
description
"This augmentation adds many yang datastore specific objects to
the notification that a subscription has started.";
uses update-policy;
uses update-qos;
}
augment "/sn:subscription-started/sn:target" {
description
"This augmentation allows the datastore to be included as part
of the notification that a subscription has started.";
Clemm, et al. Expires April 28, 2018 [Page 44]
Internet-Draft YANG-Push October 2017
case datastore {
uses datastore-criteria;
}
}
augment "/sn:filters" {
description
"This augmentation allows the datastore to be included as part
of the selection filtering criteria for a subscription.";
list selection-filter {
key "identifier";
description
"A list of pre-positioned filters that can be applied
to datastore subscriptions.";
leaf identifier {
type sn:filter-id;
description
"An identifier to differentiate between selection filters.";
}
uses selection-filter-types;
}
}
augment "/sn:subscription-modified" {
description
"This augmentation adds many yang datastore specific objects to
the notification that a subscription has been modified.";
uses update-policy;
uses update-qos;
}
augment "/sn:subscription-modified/sn:target" {
description
"This augmentation allows the datastore to be included as part
of the notification that a subscription has been modified.";
case datastore {
uses datastore-criteria;
}
}
augment "/sn:subscription-config/sn:subscription" {
description
"This augmentation adds many yang datastore specific objects
which can be configured as opposed to established via RPC.";
uses update-policy;
uses update-qos;
}
augment "/sn:subscription-config/sn:subscription/sn:target" {
description
"This augmentation adds the datastore to the selection filtering
criteria for a subscription.";
case datastore {
Clemm, et al. Expires April 28, 2018 [Page 45]
Internet-Draft YANG-Push October 2017
uses datastore-criteria;
}
}
augment "/sn:subscriptions/sn:subscription" {
yp:notifiable-on-change true;
description
"This augmentation adds many datastore specific objects to a
subscription.";
uses update-policy;
uses update-qos;
}
augment "/sn:subscriptions/sn:subscription/sn:target" {
description
"This augmentation allows the datastore to be included as part
of the selection filtering criteria for a subscription.";
case datastore {
uses datastore-criteria;
}
}
/* YANG Parser Pyang crashing on syntax below, due to fixed bug
https://github.com/mbj4668/pyang/issues/300
deviation "/sn:subscriptions/sn:subscription/sn:receivers/"
+ "sn:receiver/sn:pushed-notifications" {
deviate add {
yp:notifiable-on-change false;
}
}
deviation "/sn:subscriptions/sn:subscription/sn:receivers/"
+ "sn:receiver/sn:excluded-notifications" {
deviate add {
yp:notifiable-on-change false;
}
}
YANG Parser Pyang crashing on syntax above */
}
<CODE ENDS>
6. IANA Considerations
This document registers the following namespace URI in the "IETF XML
Registry" [RFC3688]:
URI: urn:ietf:params:xml:ns:yang:ietf-yang-push
Registrant Contact: The IESG.
XML: N/A; the requested URI is an XML namespace.
Clemm, et al. Expires April 28, 2018 [Page 46]
Internet-Draft YANG-Push October 2017
This document registers the following YANG module in the "YANG Module
Names" registry [RFC6020]:
Name: ietf-yang-push
Namespace: urn:ietf:params:xml:ns:yang:ietf-yang-push
Prefix: yp
Reference: draft-ietf-netconf-yang-push-08.txt (RFC form)
7. Security Considerations
All security considerations from
[I-D.draft-ietf-netconf-subscribed-notifications] are relevant for
datastores. In addition there are specific security considerations
for receivers defined in Section 3.9
If the access control permissions on subscribed YANG nodes change
during the lifecycle of a subscription, a publisher MUST either
transparently conform to the new access control permissions, or must
terminate or restart the subscriptions so that new access control
permissions are re-established.
The NETCONF Authorization Control Model SHOULD be used to restrict
the delivery of YANG nodes for which the receiver has no access.
8. Acknowledgments
For their valuable comments, discussions, and feedback, we wish to
acknowledge Tim Jenkins, Kent Watsen, Susan Hares, Yang Geng, Peipei
Guo, Michael Scharf, Sharon Chisholm, and Guangying Zheng.
9. References
9.1. Normative References
[I-D.draft-ietf-netconf-subscribed-notifications]
Voit, E., Clemm, A., Gonzalez Prieto, A., Tripathy, A.,
and E. Nilsen-Nygaard, "Custom Subscription to Event
Streams", draft-ietf-netconf-subscribed-notifications-06
(work in progress), October 2017.
[I.D.draft-ietf-netmod-revised-datastores]
Bjorklund, M., Schoenwaelder, J., Shafer, P., Watsen, K.,
and R. Wilton, "Network Management Datastore
Architecture", draft-ietf-netmod-revised-datastores-04
(work in progress), August 2017.
Clemm, et al. Expires April 28, 2018 [Page 47]
Internet-Draft YANG-Push October 2017
[RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
DOI 10.17487/RFC3688, January 2004,
<https://www.rfc-editor.org/info/rfc3688>.
[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>.
[RFC6470] Bierman, A., "Network Configuration Protocol (NETCONF)
Base Notifications", RFC 6470, DOI 10.17487/RFC6470,
February 2012, <https://www.rfc-editor.org/info/rfc6470>.
[RFC6536bis]
Bierman, A. and M. Bjorklund, "Network Configuration
Protocol (NETCONF) Access Control Model", draft-ietf-
netconf-rfc6536bis-05 (work in progress), September 2017.
[RFC7895] Bierman, A., Bjorklund, M., and K. Watsen, "YANG Module
Library", RFC 7895, DOI 10.17487/RFC7895, June 2016,
<https://www.rfc-editor.org/info/rfc7895>.
[RFC8072] Bierman, A., Bjorklund, M., and K. Watsen, "YANG Patch
Media Type", RFC 8072, DOI 10.17487/RFC8072, February
2017, <https://www.rfc-editor.org/info/rfc8072>.
9.2. Informative References
[I-D.draft-ietf-netconf-netconf-event-notifications]
Gonzalez Prieto, A., Clemm, A., Voit, E., Nilsen-Nygaard,
E., and A. Tripathy, "NETCONF Support for Event
Notifications", September 2017.
[promise] Burgess, M., "Some notes about promise theory", 2015,
<http://markburgess.org/PromiseMethod.pdf>.
[RFC5277] Chisholm, S. and H. Trevino, "NETCONF Event
Notifications", RFC 5277, DOI 10.17487/RFC5277, July 2008,
<https://www.rfc-editor.org/info/rfc5277>.
[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>.
[RFC7223] Bjorklund, M., "A YANG Data Model for Interface
Management", RFC 7223, DOI 10.17487/RFC7223, May 2014,
<https://www.rfc-editor.org/info/rfc7223>.
Clemm, et al. Expires April 28, 2018 [Page 48]
Internet-Draft YANG-Push October 2017
[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)
v10 - v11
o Promise model reference added.
o Error added for no-such-datastore
o Inherited changes from subscribed notifications (such as optional
feature definitions).
o scrubbed the examples for proper encodings
v09 - v10
o Returned to the explicit filter subtyping of v00-v05
o identityref to ds:datastore made explicit
o Returned ability to modify a selection filter via RPC.
v08 - v09
o Minor tweaks cleaning up text, removing appendicies, and making
reference to revised-datastores.
o Subscription-id optional in push updates, except when encoded in
RFC5277, Section 4 one-way notification.
o Finished adding the text descibing the resynch subscription RPC.
o Removed relationships to other drafts and future technology
appendicies as this work is being explored elsewhere.
o Deferred the multi-line card issue to new drafts
o Simplified the NACM interactions.
Clemm, et al. Expires April 28, 2018 [Page 49]
Internet-Draft YANG-Push October 2017
v07 - v08
o Updated YANG models with minor tweaks to accommodate changes of
ietf-subscribed-notifications.
v06 - v07
o Clarifying text tweaks.
o Clarification that filters act as selectors for subscribed data
nodes; support for value filters not included but possible as a
future extension
o Filters don't have to be matched to existing YANG objects
v05 - v06
o Security considerations updated.
o Base YANG model in [subscribe] updated as part of move to
identities, YANG augmentations in this doc matched up
o Terms refined and text updates throughout
o Appendix talking about relationship to other drafts added.
o Datastore replaces stream
o Definitions of filters improved
v04 to v05
o Referenced based subscription document changed to Subscribed
Notifications from 5277bis.
o Getting operational data from filters
o Extension notifiable-on-change added
o New appendix on potential futures. Moved text into there from
several drafts.
o Subscription configuration section now just includes changed
parameters from Subscribed Notifications
o Subscription monitoring moved into Subscribed Notifications
Clemm, et al. Expires April 28, 2018 [Page 50]
Internet-Draft YANG-Push October 2017
o New error and hint mechanisms included in text and in the yang
model.
o Updated examples based on the error definitions
o Groupings updated for consistency
o Text updates throughout
v03 to v04
o Updates-not-sent flag added
o Not notifiable extension added
o Dampening period is for whole subscription, not single objects
o Moved start/stop into rfc5277bis
o Client and Server changed to subscriber, publisher, and receiver
o Anchor time for periodic
o Message format for synchronization (i.e. synch-on-start)
o Material moved into 5277bis
o QoS parameters supported, by not allowed to be modified by RPC
o Text updates throughout
Authors' Addresses
Alexander Clemm
Huawei
Email: ludwig@clemm.org
Eric Voit
Cisco Systems
Email: evoit@cisco.com
Clemm, et al. Expires April 28, 2018 [Page 51]
Internet-Draft YANG-Push October 2017
Alberto Gonzalez Prieto
VMware
Email: agonzalezpri@vmware.com
Ambika Prasad Tripathy
Cisco Systems
Email: ambtripa@cisco.com
Einar Nilsen-Nygaard
Cisco Systems
Email: einarnn@cisco.com
Andy Bierman
YumaWorks
Email: andy@yumaworks.com
Balazs Lengyel
Ericsson
Email: balazs.lengyel@ericsson.com
Clemm, et al. Expires April 28, 2018 [Page 52]
