NETCONF A. Clemm
Internet-Draft Huawei
Intended status: Standards Track E. Voit
Expires: February 21, 2018 Cisco Systems
A. Gonzalez Prieto
VMware
A. Tripathy
E. Nilsen-Nygaard
Cisco Systems
A. Bierman
YumaWorks
B. Lengyel
Ericsson
August 20, 2017
Subscribing to YANG datastore push updates
draft-ietf-netconf-yang-push-08
Abstract
Providing rapid 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
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on February 21, 2018.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Definitions and Acronyms . . . . . . . . . . . . . . . . . . 4
3. Solution Overview . . . . . . . . . . . . . . . . . . . . . . 5
3.1. Event Subscription Model . . . . . . . . . . . . . . . . 5
3.2. Negotiation of Subscription Policies . . . . . . . . . . 6
3.3. On-Change Considerations . . . . . . . . . . . . . . . . 6
3.4. Promise-Theory Considerations . . . . . . . . . . . . . . 8
3.5. Data Encodings . . . . . . . . . . . . . . . . . . . . . 8
3.6. Datastore filters . . . . . . . . . . . . . . . . . . . . 9
3.7. Streaming updates . . . . . . . . . . . . . . . . . . . . 10
3.8. Subscription management . . . . . . . . . . . . . . . . . 13
3.9. Receiver Authorization . . . . . . . . . . . . . . . . . 14
3.10. On-change notifiable YANG objects . . . . . . . . . . . . 15
3.11. Other considerations . . . . . . . . . . . . . . . . . . 16
4. A YANG data model for management of datastore push
subscriptions . . . . . . . . . . . . . . . . . . . . . . . . 18
4.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . 18
4.2. Subscription configuration . . . . . . . . . . . . . . . 24
4.3. YANG Notifications . . . . . . . . . . . . . . . . . . . 25
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4.4. YANG RPCs . . . . . . . . . . . . . . . . . . . . . . . . 26
5. YANG module . . . . . . . . . . . . . . . . . . . . . . . . . 31
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 46
7. Security Considerations . . . . . . . . . . . . . . . . . . . 46
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 47
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 47
9.1. Normative References . . . . . . . . . . . . . . . . . . 47
9.2. Informative References . . . . . . . . . . . . . . . . . 48
Appendix A. Relationships to other drafts . . . . . . . . . . . 48
A.1. ietf-netconf-subscribed-notifications . . . . . . . . . . 49
A.2. ietf-netconf-netconf-event-notif . . . . . . . . . . . . 49
A.3. ietf-netconf-restconf-notif . . . . . . . . . . . . . . . 49
A.4. voit-notifications2 . . . . . . . . . . . . . . . . . . . 49
Appendix B. Technologies to be considered for future iterations 50
B.1. Proxy YANG Subscription when the Subscriber and Receiver
are different . . . . . . . . . . . . . . . . . . . . . . 50
B.2. OpState and Filters . . . . . . . . . . . . . . . . . . . 50
B.3. Splitting push updates . . . . . . . . . . . . . . . . . 51
B.4. Potential Subscription Parameters . . . . . . . . . . . . 52
Appendix C. Changes between revisions . . . . . . . . . . . . . 52
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 54
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
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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 Notifications" [subscribe].
Supplementing that work are YANG data model augmentations, extended
RPCs, and new datastore specific update notifications. Transport
options for [subscribe] will work seamlessly with this solution.
2. Definitions and Acronyms
The terms below supplement those defined in [subscribe].
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.
Notification message: A transport encapsulated update record(s) and/
or event notification(s) intended to be sent to a receiver.
Update notification message: A notification message that contains an
update record.
Update record: A representation data node update(s) resulting from
the application of a 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.
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.
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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 update 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. Event Subscription Model
YANG-push subscriptions are defined using a data model that is itself
defined in YANG. This model enhances the event subscription model
defined in [subscribe] with capabilities that allow subscribers to
subscribe to data node updates, specifically to specify the triggers
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 that specify the conditions that
trigger the generation and pushing of new update records. There
are two types of 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
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dampening period collectively applies to the set of all data
nodes of a single subscription. This means that on change
of an object being subscribed to, 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
of a subscription. Such synchronization establishes the
frame of reference for subsequent updates.
3.2. Negotiation of Subscription Policies
A dynamic subscription request SHOULD be declined based on
publisher's assessment that it may be unable to provide update
records that would meet the terms of the request. However 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
in fact be accepted.
Such negotiation information returned from a publisher beyond that
from [subscribe] includes hints at acceptable time intervals, size
estimates for the number or objects which would be returned from a
filter, and the names of targeted objects not found in the
publisher's YANG tree.
3.3. On-Change Considerations
On-change subscriptions allow subscribers to subscribe to updates
whenever changes to objects occur. As such, on-change subscriptions
are particularly effective for data that changes infrequently, yet
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that requires applications to be 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 server implementation: A server
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 objects are
excluded from update records, whether or not their values actually
change. In order for a client to determine whether objects support
on-change subcriptions, objects are marked accordingly by a server.
Accordingly, when subscribing, it is the responsibility of the client
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 server 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 subsription can be marked as suspended respectively
inoperational.
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 includes 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 occuring on that object.
In cases where a client wants to have separate dampening periods for
different objects, multiple subscriptions with different objects in
subscription scope can be created.
On-change subscriptions can be refined to let users subscribe only to
certain types of changes, for example, only to object creations and
deletions, but not to modifications of object values.
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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 of
utmost importance 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 server
to provide the receivers with updates per the terms of the
subscription.
Now, there are many reasons why a server 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 updates from being collected. If for
some reason the server of a subscription is not able to keep its
promise, receivers MUST be notified immediately and reliably. The
server MUST also update the state of the subscription to indicate
that the subscription is in a detrimental state.
A server SHOULD reject a request for a subscription if it is unlikely
that the server will be able fulfill the terms of the subscription.
In such cases, it is preferable to have a client request another
subscription that is less resource intensive (for example, a
subscription with longer periodic update intervals), than to
subsequently frustrate the receiver with `frequent subscription
suspensions.
3.5. Data Encodings
Subscribed data is encoded in either XML or JSON format. A publisher
MUST support XML encoding and MAY support 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. XML encoding rules for
data nodes are defined in [RFC7950]. JSON encoding rules are defined
in [RFC7951].
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
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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 filters
Subscription policy specifies both the filters and the datastores
against which the filters will be applied. The result is the push of
information necessary to remotely maintain an extract of publisher's
datastore.
Only a single 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 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 filter is an XPath expression which may be
meaningfully applied to a datastore. It is the results of this
expression which will be pushed.
Filters are intended to be used as selectors that define which
objects are within the scope of a subscription. Filters are not
intended to be used to store objects based on their current value.
Doing so would have a number of implications that would result in
significant additional complexity. For example, withough extending
encodings for on-change subscriptions, a receiver would not be able
to distinguish cases in which an object is no longer included in an
update because it was deleted, as opposed to its value simply no
longer meeting the filter criteria. While it is possible to define
extensions in the future that will support filtering based on values,
this is not supported in this version of yang-push and a server 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 interface=up. It is up to the
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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 notifications for update 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 notification
is used for continuous updates of periodic subscriptions. A push-
update notification can also used be 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 of YANG objects. 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 YANG notifications are encoded and placed within
notification messages, which are then queued for egress over the
specified transport. The following is an example of an XML encoded
notification message over NETCONF transport as per [netconf-notif].
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<notification
xmlns="urn:ietf:params:xml:ns:netconf:notification:1.0">
<eventTime>2015-03-09T19:14:56Z</eventTime>
<push-update
xmlns="urn:ietf:params:xml:ns:yang:ietf-yang-push:1.0">
<subscription-id>1011</subscription-id>
<time-of-update>2015-03-09T19:14:56.233Z</time-of-update>
<datastore-contents>
<foo>
<bar>some_string</bar>
</foo>
</datastore-contents>
</push-update>
</notification>
Figure 1: Push example
The following is an example of an on-change notification. It
contains an update for subscription 89, including a new value for a
leaf called beta, which is a child of a top-level container called
alpha:
<notification
xmlns="urn:ietf:params:xml:ns:netconf:notification:1.0">
<eventTime>2015-03-09T19:14:56Z</eventTime>
<push-change-update xmlns=
"urn:ietf:params:xml:ns:yang:ietf-yang-push:1.0">
<subscription-id>89</subscription-id>
<time-of-update>2015-03-09T19:14:56.233Z</time-of-update>
<datastore-changes>
<alpha xmlns="http://example.com/sample-data/1.0" >
<beta>1500</beta>
</alpha>
</datastore-changes>
</push-change-update>
</notification>
Figure 2: Push example for on change
The equivalent update when requesting json encoding:
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<notification
xmlns="urn:ietf:params:xml:ns:netconf:notification:1.0">
<eventTime>2015-03-09T19:14:56Z</eventTime>
<push-change-update xmlns=
"urn:ietf:params:xml:ns:yang:ietf-yang-push:1.0">
<subscription-id>89</subscription-id>
<time-of-update>2015-03-09T19:14:56.233Z</time-of-update>
<datastore-changes>
{
"ietf-yang-patch:yang-patch": {
"patch-id": [
null
],
"edit": [
{
"edit-id": "edit1",
"operation": "merge",
"target": "/alpha/beta",
"value": {
"beta": 1500
}
}
]
}
}
</datastore-changes>
</push-change-update>
</notification>
Figure 3: Push example for on change with JSON
When the beta leaf is deleted, the publisher may send
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<notification
xmlns="urn:ietf:params:xml:ns:netconf:notification:1.0">
<eventTime>2015-03-09T19:14:56Z</eventTime>
<push-change-update xmlns=
"urn:ietf:params:xml:ns:yang:ietf-yang-push:1.0">
<subscription-id>89</subscription-id>
<time-of-update>2015-03-09T19:14:56.233Z</time-of-update>
<datastore-changes-xml>
<alpha xmlns="http://example.com/sample-data/1.0" >
<beta urn:ietf:params:xml:ns:netconf:base:1.0:
operation="delete"/>
</alpha>
</datastore-changes-xml>
</push-change-update>
</notification>
Figure 4: 2nd push example for on change update
3.8. Subscription management
[subscribe] has been enhanced to support YANG datastore subscription
negotiation. These enhancements provide information on why a
datastore subscription attempt has failed.
A datastore subscription can be rejected for multiple reasons. This
includes the lack of read authorization on a requested data node, 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.
It should be noted that a rejected subscription does not result in
the generation of an rpc-reply with an rpc-error element, as neither
the specification of YANG-push specific errors nor the specification
of additional data parameters to be returned in an error case are
supported as part of a YANG data model.
For instance, for the following request:
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<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-yang-push:1.0">
<datastore>push-update</datastore>
<filter netconf:type="xpath"
xmlns:ex="http://example.com/sample-data/1.0"
select="/ex:foo"/>
<period>500</period>
<encoding>encode-xml</encoding>
</establish-subscription>
</netconf:rpc>
Figure 5: Establish-Subscription example
the publisher might return:
<rpc-reply message-id="101"
xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
<subscription-result
xmlns="http://urn:ietf:params:xml:ns:yang:ietf-yang-push:1.0">
error-insufficient-resources
</subscription-result>
<period>2000</period>
</rpc-reply>
Figure 6: Error response example
3.9. Receiver Authorization
A receiver of subscription data MUST only be sent updates for which
they have proper authorization. A server 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.
Alternatively, a server that wants to avoid having to perform
filtering of authorized content on each update MAY instead simply
reject a subscription request that contains non-authorized data. It
MAY subsequently suspend a subscription in case new objects are
created during the course of the subscription for which the receiver
does not have the necessary authorization, or in case the
authorization privileges of a receiver change over the course of the
subscription.
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The contextual authorization model for data in YANG datastores is the
NETCONF Access Control Model [RFC6536bis], Section 3.2.3. However,
there are some differences.
One of these clarifications is that datastore selection MUST NOT
return continuous errors as part of an on-change subscription. This
includes errors such as when there is not read access to every data
node specifically named within the filter. Non-authorized data needs
to be either simply dropped or, alternatively, the subscription
SHOULD be suspended.
+-------------+ +-------------+
establish / | protocol | | filter |
modify --> | operation | -------------> | data node |
subscription | allowed? | datastore | access |
+-------------+ objects | allowed? |
+-------------+
Figure 7: Access control for subscription
Another clarification to [RFC6536bis] 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 into new nodes added since the last update record. If
read access into previously accessible nodes not explicitly named in
the filter are lost mid-subscription, that can be treated as a
'delete' for on-change subscriptions. If not capable of handling
such permission changes for dynamic subscriptions, publisher
implementations MAY choose to terminate the subscription and to force
re-establishment with appropriate filtering.
+-------------+ +-------------------+
push-update / --> | data node | yes | |
push-change-update | access | ---> | add data node |
| allowed? | | to update message |
+-------------+ +-------------------+
Figure 8: Access control for push updates
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
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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
"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 client can identify which nodes will be
included in on-change updated by retrieving the data nodes in the
subscription's scope and checking for which notifiable-on-change is
marked as true.
Adding notifiable-on-change markings will in general require updating
the corresponding YANG models. A simple way to avoid having to
modify existing module definitions is to add notifiable-on-change
markings by defining 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 appicable.
deviation /sys:system/sys:system-time {
deviate add {
yp:notifiable-on-change false;
}
}
Figure 9: 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.
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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 [subscribe].
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 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. Update size and fragmentation
Depending on the subscription, the volume of updates can become quite
large. Additionally, based on the platform, it is possible that
update records for a single subscription are best sent independently
from different line-cards. Therefore, it may not always be practical
to send the entire update record in a single chunk. Implementations
may therefore choose, at their discretion, to "chunk" update records,
breaking one subscription's objects across several update records.
In this case the updates-not-sent flag will indicate that no single
update record is complete, and it is permissible for multiple updates
to come into a receiver for a single periodic interval or on-change
dampening period.
Care must be taken in chunking as problems may arrise for objects
that have containment or referential dependencies. The publisher
must consider these issues if chunking is provided.
3.11.3. Publisher capacity
It is far preferable to decline a subscription request than to accept
such a request when it cannot be met.
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Whether or not a subscription can be supported will be determined by
a combination of several factors such as the subscription policy (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 [subscribe]) are identified with "yp".
module: ietf-subscribed-notifications
+--ro streams
| +--ro stream* [stream]
| | +--ro stream stream
| | +--ro description string
| | +--ro replay-support? empty
| | +--ro replay-log-creation-time? yang:date-and-time
| | +--ro replay-log-aged-time? yang:date-and-time
| +--ro yp:datastores
| +--ro yp:datastore* datastore
+--rw filters
| +--rw filter* [identifier]
| +--rw identifier filter-id
| +--rw (filter-type)?
| +--:(event-filter)
| +--rw event-filter-type event-filter-type
| +--rw event-filter <anyxml>
+--rw subscription-config {configured-subscriptions}?
| +--rw subscription* [identifier]
| +--rw identifier subscription-id
| +--rw encoding? encoding
| +--rw (target)
| | +--:(event-stream)
| | | +--rw stream stream
| | +--:(yp:datastore)
| | +--rw yp:datastore datastore
| | +--rw yp:selection-filter-type selection-filter-type
| | +--rw yp:selection-filter <anyxml>
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| +--rw (applied-filter)
| | +--:(by-reference)
| | | +--rw filter-ref filter-ref
| | +--:(within-subscription)
| | +--rw (filter-type)?
| | +--:(event-filter)
| | +--rw event-filter-type event-filter-type
| | +--rw event-filter <anyxml>
| +--rw stop-time? yang:date-and-time
| +--rw receivers
| | +--rw receiver* [address port]
| | +--rw address inet:host
| | +--rw port inet:port-number
| | +--rw protocol? transport-protocol
| +--rw (notification-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-subscriptions}?
+--ro encoding? encoding
+--ro (target)
| +--:(event-stream)
| | +--ro stream stream
| | +--ro replay-start-time? yang:date-and-time
| | {replay}?
| +--:(yp:datastore)
| +--ro yp:datastore datastore
| +--ro yp:selection-filter-type selection-filter-type
| +--ro yp:selection-filter <anyxml>
+--ro (applied-filter)
| +--:(by-reference)
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| | +--ro filter-ref filter-ref
| +--:(within-subscription)
| +--ro (filter-type)?
| +--:(event-filter)
| +--ro event-filter-type event-filter-type
| +--ro event-filter <anyxml>
+--ro stop-time? yang:date-and-time
+--ro (notification-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-protocol
| +--ro pushed-notifications? yang:counter64
| +--ro excluded-notifications? yang:counter64
| +--ro status subscription-status
+--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)
| | | +--:(event-stream)
| | | | +---w stream stream
| | | | +---w replay-start-time? yang:date-and-time
| | | | {replay}?
| | | +--:(yp:datastore)
| | | +---w yp:datastore datastore
| | | +---w yp:selection-filter-type selection-filter-type
| | | +---w yp:selection-filter <anyxml>
| | +---w (applied-filter)
| | | +--:(by-reference)
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| | | | +---w filter-ref filter-ref
| | | +--:(within-subscription)
| | | +---w (filter-type)?
| | | +--:(event-filter)
| | | +---w event-filter-type event-filter-type
| | | +---w event-filter <anyxml>
| | +---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 (applied-filter)
| | | +--:(by-reference)
| | | | +---w filter-ref filter-ref
| | | +--:(within-subscription)
| | | +---w (filter-type)?
| | | +--:(event-filter)
| | | +---w event-filter-type event-filter-type
| | | +---w event-filter <anyxml>
| | +---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
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| | +--:(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-complete
| +--ro identifier subscription-id
+---n notification-complete
| +--ro identifier subscription-id
+---n subscription-started
| +--ro identifier subscription-id
| +--ro encoding? encoding
| +--ro (target)
| | +--:(event-stream)
| | | +--ro stream stream
| | | +--ro replay-start-time? yang:date-and-time
| | | {replay}?
| | +--:(yp:datastore)
| | +--ro yp:datastore datastore
| | +--ro yp:selection-filter-type selection-filter-type
| | +--ro yp:selection-filter <anyxml>
| +--ro (applied-filter)
| | +--:(by-reference)
| | | +--ro filter-ref filter-ref
| | +--:(within-subscription)
| | +--ro (filter-type)?
| | +--:(event-filter)
| | +--ro event-filter-type event-filter-type
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| | +--ro event-filter <anyxml>
| +--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
| +--ro identifier subscription-id
| +--ro encoding? encoding
| +--ro (target)
| | +--:(event-stream)
| | +--ro stream stream
| | +--ro replay-start-time? yang:date-and-time {replay}?
| +--ro (applied-filter)
| | +--:(by-reference)
| | | +--ro filter-ref filter-ref
| | +--:(within-subscription)
| | +--ro (filter-type)?
| | +--:(event-filter)
| | +--ro event-filter-type event-filter-type
| | +--ro event-filter <anyxml>
| +--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
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+--ro error-id subscription-errors
+--ro filter-failure? string
module: ietf-yang-push
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? <anydata>
+---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? <anydata>
Figure 10: 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-config. Each subscription has own list elements.
New and enhanced parameters extending the basic subscription data
model in [subscribe] include:
o An update filter identifying yang nodes of interest. Filter
contents are specified via a reference to an existing filter, or
via an in-line definition for only that subscription. This
facilitates the reuse of filter definitions, which can be
important in case of complex filter conditions. Referenced
filters can also allow 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 after the anchor time. If
anchor time is not provided, then the anchor time MUST be set
with the creation time of the initial update record.
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o For on-change subscriptions, assuming the dampening period has
completed, triggered 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 others 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.
4.3. YANG Notifications
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4.3.1. Monitoring and OAM Notifications
OAM notifications and mechanism are reused from [subscribe]. Some
have been augmented to include the YANG datastore specific objects.
4.3.2. New Notifications for update records
The data model introduces two YANG notifications to encode
information for update records: "push-update" and "push-change-
update".
"Push-update" is used to send a complete snapshot of the filtered
subscription data. This type of notification is used to carry the
update records of a periodic subscription. The "push-update"
notification is also used with on-change subscriptions for the
purposes of allowing a receiver to "synch" on a complete set of
subscribed datastore contents. This synching may be done the start
of an on-change subscription, and then later in that subscription to
force resynchronization. If the "updates-not-sent" flag is set, this
indicates that the update record is incomplete.
"Push-change-update" is used to send datastore changes that have
occurred in subscribed data since the previous update. This
notification is used only in conjunction with on-change
subscriptions. This will be encoded as yang-patch data.
If the application detects an informational discontinuity in either
notification, the notification MUST include a flag "updates-not-
sent". This flag which 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
synchronization, a publisher MAY subsequently send a push-update
containing a full snapshot of subscribed data.
4.4. YANG RPCs
YANG-Push subscriptions are established, modified, and deleted using
RPCs augmented from [subscribe].
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:
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<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-yang-push:1.0">
<filter netconf:type="xpath"
xmlns:ex="http://example.com/sample-data/1.0"
select="/ex:foo"/>
<period>500</period>
<encoding>encode-xml</encoding>
</establish-subscription>
</netconf:rpc>
Figure 11: 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 subscription-id 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-yang-push:1.0">
ok
</subscription-result>
<subscription-id
xmlns="urn:ietf:params:xml:ns:yang:ietf-yang-push:1.0">
52
</subscription-id>
</rpc-reply>
Figure 12: Establish-subscription positive RPC response
A subscription can be rejected for multiple reasons, including the
lack of authorization to establish a subscription, the lack of read
authorization on the requested data node, or the inability of the
publisher to provide a stream with the requested semantics.
When the requester is not authorized to read the requested data node,
the returned information indicates the node is unavailable. For
instance, if the above request was unauthorized to read node "ex:foo"
the publisher may return:
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<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-yang-push:1.0">
subtree-unavailable
</subscription-result>
<filter-failure
xmlns="urn:ietf:params:xml:ns:yang:ietf-yang-push:1.0">
/ex:foo
</filter-failure>
</rpc-reply>
Figure 13: Establish-subscription access denied response
If a request is rejected because the publisher is not able to serve
it, the publisher SHOULD include in the returned error what
subscription parameters would have been accepted for the request.
However, there are no guarantee that subsequent requests using this
info will in fact be accepted.
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-yang-push:1.0">
<datastore>running</datastore>
<filter netconf:type="xpath"
xmlns:ex="http://example.com/sample-data/1.0"
select="/ex:foo"/>
<dampening-period>10</dampening-period>
<encoding>encode-xml</encoding>
</establish-subscription>
</netconf:rpc>
Figure 14: Establish-subscription request example 2
a publisher that cannot serve on-change updates but periodic updates
might return the following:
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<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-yang-push:1.0">
period-unsupported
</subscription-result>
<period-hint>100</period-hint>
</rpc-reply>
Figure 15: 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.
<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-yang-push:1.0">
<datastore>running</datastore>
<subscription-id>
1011
</subscription-id>
<period>250</period>
</modify-subscription>
</netconf:rpc>
Figure 16: 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-yang-push:1.0">
ok
</subscription-result>
</rpc-reply>
Figure 17: Modify subscription response
If the subscription modification is rejected, the publisher MUST send
a response like it does for an establish-subscription and maintain
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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.
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-id. For
example:
<netconf:rpc message-id="103"
xmlns:netconf="urn:ietf:params:xml:ns:netconf:base:1.0">
<delete-subscription
xmlns="urn:ietf:params:xml:ns:yang:ietf-yang-push:1.0">
<subscription-id>
1011
</subscription-id>
</delete-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-yang-push:1.0">
ok
</subscription-result>
</rpc-reply>
Figure 18: Delete subscription
Configured subscriptions cannot be deleted via RPC, but have to be
removed from the configuration.
4.4.4. 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
Library module (ietf-yang-library.yang from [RFC7895]. The YANG
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library information is important for the receiver to reproduce the
set of object definitions used by the replicated datastore.
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 server 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
client that the library has changed. The receiver then needs to re-
read the entire YANG library data for the replicated server 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@2017-08-20.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;
}
organization "IETF";
contact
"WG Web: <http://tools.ietf.org/wg/netconf/>
WG List: <mailto:netconf@ietf.org>
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WG Chair: Mahesh Jethanandani
<mailto:mjethanandani@gmail.com>
WG Chair: Kent Watsen
<mailto:kwatsen@juniper.net>
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 2017-08-20 {
description
"Initial revision.";
reference
"YANG Datastore Push, draft-ietf-netconf-yang-push-08";
}
/*
* EXTENSIONS
*/
extension notifiable-on-change {
argument "value";
description
"Indicates whether changes to the data node are reportable in
on-change subscriptions.
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The statement MUST only be a substatement of the leaf, leaf-list,
container, list, anyxml, anydata statements. Zero or One
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 updates 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
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"On-change not supported.";
}
identity synch-on-start-unsupported {
base sn:error;
description
"On-change synch-on-start not supported.";
}
identity synch-on-start-datatree-size {
base sn:error;
description
"Synch-on-start would push a datatree which exceeds size limit.";
}
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 push updates would exceed size limit.";
}
/* Datastore identities */
identity datastore {
description
"Abstract base identity for datastore identities. More are in the
process of being defined within
draft-ietf-netmod-revised-datastores. ";
}
identity candidate {
base datastore;
description
"The candidate datastore per RFC-6241.";
reference "RFC-6241, #5.1";
}
identity running {
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base datastore;
description
"The running datastore per RFC-6241.";
reference "RFC-6241, #5.1";
}
identity startup {
base datastore;
description
"The startup datastore per RFC-6241.";
reference "RFC-6241, #5.1";
}
identity operational {
base datastore;
description
"The operational datastore contains all configuration data
actually used by the system, including all applied configuration,
system-provided configuration and values defined by any supported
data models. In addition, the operational datastore also
contains state data.";
reference
"the original text came from draft-ietf-netmod-revised-datastores
-01, section #4.3. This definition is expected to remain stable
meaning later reconciliation between the drafts unnecessary.";
}
identity intended {
base datastore;
description
"The intended datastore per draft-ietf-netmod-revised-datastores.";
reference
"draft-ietf-netmod-revised-datastores";
}
identity custom-datastore {
base datastore;
description
"Another datastore not defined via an identity in this model";
}
/* Selection filter identities */
identity selection-filter {
description
"Evaluation criteria encoded in a syntax which allows the
selection of nodes from a target. If the filter is applied
against a datastore for periodic extracts, the resulting node-set
result is passed along. If the filter is applied against a
datastore looking for changes, deltas from the last update in the
form of a patch result are passed along. An empty node set is a
valid result of this filter type.";
}
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identity subtree-selection-filter {
base selection-filter;
description
"An RFC-6241 based selection-filter which may be used to select
nodes within a datastore.";
reference "RFC-6241, #5.1";
}
identity xpath-selection-filter {
base selection-filter;
description
"A selection-filter which may be applied to a datastore which
follows the syntax specified in yang:xpath1.0. Nodes that evaluate
to true are included in the selection.";
reference "XPATH: http://www.w3.org/TR/1999/REC-xpath-19991116";
}
/*
* 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";
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}
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 recieve a delete on a
missing node.";
}
typedef datastore {
type identityref {
base datastore;
}
description
"Specifies a system-provided datastore. May also specify ability
portion of a datastore, so as to reduce the filtering effort.";
}
typedef selection-filter-type {
type identityref {
base selection-filter;
}
description
"Specifies a known type of selection filter.";
}
/*
* GROUP DEFINITIONS
*/
grouping datastore-criteria {
description
"A grouping to define criteria for which objects from which
datastore to include in push updates.";
leaf datastore {
type datastore;
mandatory true;
description
"Datastore against which the subscription has been
applied.";
}
uses selection-filter-objects;
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}
grouping selection-filter-objects {
description
"This grouping defines a selector for objects from a
datastore.";
leaf selection-filter-type {
type selection-filter-type;
mandatory true;
description
"A filter needs to be a known and understood syntax if it is
to be interpretable by a device.";
}
anyxml selection-filter {
mandatory true;
description
"Datastore evaluation criteria encoded in a syntax of a
supported type of selection filter.";
}
}
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 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
push updates. Where the anchor of a start-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 from which the series of periodic
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push updates are computed. The next update will take place
at the next period interval from the anchor time. For
example, for an anchor time at the top of a minute and a
period interval of a minute, the next update will be sent
at the top of the next minute.";
}
}
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.";
}
}
}
}
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
"This leaf acts as a flag that determines behavior at the
start of the subscription. When present, synchronization
of state at the beginning of the subscription is outside
the scope of the subscription. Only updates about changes
that are observed from the start time, 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 only are sent unless the
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Publisher chooses to resynch the subscription again.";
}
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";
}
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 of
the parent has something ready to push.";
reference
"RFC-7540, section 5.3.1";
}
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}
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
"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.";
}
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}
/*
* DATA NODES
*/
augment "/sn:streams" {
description
"This augmentation adds datastores to the list of items that
can be subscribed.";
container datastores {
config false;
description
"This container contains a leaf list of built-in
streams that are provided by the system.";
leaf-list datastore {
type datastore;
description
"Identifies the built-in datastores that are supported by
the system. Built-in datastores are associated with their
own identities. In case configurable custom datastores are
supported, as indicated by the custom-datastore identity.
The configuration and delivery of those custom datastores is
provided separately.";
}
}
}
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.";
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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: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
"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;
mandatory true;
description
"This references the subscription because of which the
notification is sent.";
}
leaf time-of-update {
type yang:date-and-time;
description
"This leaf contains the time of the 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. This may lead to intermittent loss of
synchronization of data at the client. Synchronization at the
client can occur when the next push-update is received.";
}
anydata datastore-contents {
description
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"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;
mandatory true;
description
"This references the subscription because of which the
notification is sent.";
}
leaf time-of-update {
type yang:date-and-time;
description
"This leaf contains the time of the update, i.e. the time at
which the change was observed.";
}
leaf updates-not-sent {
type empty;
description
"This is a flag which indicates that 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.
To facilitate synchronization, a publisher may subsequently
send a push-update containing a full snapshot of subscribed
data. Such a push-update might also be triggered by a
subscriber requesting an on-demand synchronization.";
}
anydata datastore-changes {
description
"This contains datastore contents that has changed since 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
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current state (and assuming yang-patch could also be applied
to operational data).";
}
}
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.";
case datastore {
uses datastore-criteria;
}
}
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-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 {
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;
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}
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;
}
}
}
<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.
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 [subscribe] are relevant for
datastores. In addition there are specific security considerations
for receviers 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.
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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
[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-04 (work in progress), June 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>.
[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>.
[RFC7951] Lhotka, L., "JSON Encoding of Data Modeled with YANG",
RFC 7951, DOI 10.17487/RFC7951, August 2016,
<https://www.rfc-editor.org/info/rfc7951>.
[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>.
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[subscribe]
Voit, E., Clemm, A., Gonzalez Prieto, A., Tripathy, A.,
and E. Nilsen-Nygaard, "Custom Subscription to Event
Notifications", draft-ietf-netconf-subscribed-
notifications-03 (work in progress), July 2017.
9.2. Informative References
[http-notif]
Voit, E., Gonzalez Prieto, A., Tripathy, A., Nilsen-
Nygaard, E., Clemm, A., and A. Bierman, "Restconf and HTTP
Transport for Event Notifications", August 2017.
[netconf-notif]
Gonzalez Prieto, A., Clemm, A., Voit, E., Nilsen-Nygaard,
E., and A. Tripathy, "NETCONF Support for Event
Notifications", July 2017.
[notifications2]
Voit, E., Bierman, A., Clemm, A., and T. Jenkins, "YANG
Notification Headers and Bundles", July 2017.
[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>.
[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. Relationships to other drafts
There are other related drafts which are progressing in the NETCONF
WG. This section details the relationship of this draft to those
others.
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A.1. ietf-netconf-subscribed-notifications
The draft [subscribe] is the techical foundation around which the
rest of the YANG push datastore specific mechanisms are layered.
A.2. ietf-netconf-netconf-event-notif
The [netconf-notif] draft supports yang-push by defining NETCONF
transport specifics. Included are:
o bindings for RPC communications and Event Notifications over
NETCONF.
o encoded examples
A.3. ietf-netconf-restconf-notif
The [http-notif] draft supports yang-push by defining transport
specific guidance where some form of HTTP is used underneath.
Included are:
o bindings for RPC communications over RESTCONF
o bindings for Event Notifications over HTTP2 and HTTP1.1
o encoded examples
o end-to-end deployment guidance for Call Home and TLS Heartbeat
A.4. voit-notifications2
The draft [notifications2] is not required to implement yang-push.
Instead it defines data plane notification elements which improve the
delivered experience. The following capabilities are specified:
o Defines common encapsulation headers objects to support
functionality such as event severity, message signing, message
loss discovery, message de-duplication, originating process
identification.
o Defines how to bundle multiple event records into a single
notification message.
These capabilities would be delivered by adding the drafts newly
proposed header objects to the push-update and push-change-update
notifications defined here. This draft is not yet adopted by the
NETCONF WG.
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Appendix B. Technologies to be considered for future iterations
B.1. Proxy YANG Subscription when the Subscriber and Receiver are
different
The properties of Dynamic and Configured Subscriptions can be
combined to enable deployment models where the Subscriber and
Receiver are different. Such separation can be useful with some
combination of:
o An operator does not want the subscription to be dependent on the
maintenance of transport level keep-alives. (Transport
independence provides different scalability characteristics.)
o There is not a transport session binding, and a transient
Subscription needs to survive in an environment where there is
unreliable connectivity with the Receiver and/or Subscriber.
o An operator wants the Publisher to include highly restrictive
capacity management and Subscription security mechanisms outside
of domain of existing operational or programmatic interfaces.
To build a Proxy Subscription, first the necessary information must
be signaled as part of the <establish-subscription>. Using this set
of Subscriber provided information; the same process described within
section 3 will be followed.
After a successful establishment, if the Subscriber wishes to track
the state of Receiver subscriptions, it may choose to place a
separate on-change Subscription into the "Subscriptions" subtree of
the YANG Datastore on the Publisher.
B.2. OpState and Filters
Currently the concept of datastores is undergoing a transformation.
A new Network Management Datastore Architecture (NMDA) is currently
being defined that will allow for improved handling and distinction
of intended versus applied configurations. It will also extend the
notion of a datastore to operational data. For implementations that
are NMDA compliant in the future, some of the objects that are
currently defined as operational data will no longer be required
because they will in effect be redundant. Specifically, this
concerns many of the objects in the read-only subscriptions branch of
the tree. By omitting those objects, the model could be optimized
further. However, there is no harm in the redundant objects and they
allow for common management of YANG-Push subscriptions whether or not
the underlying platform is fully NMDA-compliant, as opposed to
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exposing client applications to heterogeneity in platform NMDA
capabilities.
It is conceivable that filters are defined that apply to metadata,
such as data nodes for which metadata has been defined that meets a
certain criteria.
It is also conceivable to define in the future filters that are
applied to actual data node values. Doing so would allow
applications to subscribe to updates that are sent only when object
values meet certain criteria, such as being outside a certain range.
Defining any such subscription filters at this point would be highly
speculative in nature. However, it should be noted that
corresponding extensions may be defined in future specifications.
Any such extensions will be straightforward to accommodate by
introducing a model that defines new filter types, and augmenting the
new filter type into the subscription model.
B.3. Splitting push updates
Push updates may become fairly large and extend across multiple
subsystems in a YANG-Push Server. As a result, it conceivable to not
combine all updates into a single update message, but to split
updates into multiple separate update messages. Such splitting could
occur along multiple criteria: limiting the number of data nodes
contained in a single update, grouping updates by subtree, grouping
updates by internal subsystems (e.g., by line card), or grouping them
by other criteria.
Splitting updates bears some resemblance to fragmenting packets. In
effect, it can be seen as fragmenting update messages at an
application level. However, from a transport perspective, splitting
of update messages is not required as long as the transport does not
impose a size limitation or provides its own fragmentation mechanism
if needed. We assume this to be the case for YANG-Push. In the case
of NETCONF, RESTCONF, HTTP/2, no limit on message size is imposed.
In case of other transports, any message size limitations need to be
handled by the corresponding transport mapping.
There may be some scenarios in which splitting updates might still
make sense. For example, if updates are collected from multiple
independent subsystems, those updates could be sent separately
without need for combining. However, if updates were to be split,
other issues arise. Examples include indicating the number of
updates to the receiver, distinguishing a missed fragment from a
missed update, and the ordering with which updates are received.
Proper addressing those issues would result in considerable
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complexity, while resulting in only very limited gains. In addition,
if a subscription is found to result in updates that are too large, a
publisher can always reject the request for a subscription while the
subscriber is always free to break a subscription up into multiple
subscriptions.
B.4. Potential Subscription Parameters
A possible is the introduction of an additional parameter "changes-
only" for periodic subscription. Including this flag would results
in sending at the end of each period an update containing only
changes since the last update (i.e. a change-update as in the case of
an on-change subscription), not a full snapshot of the subscribed
information. Such an option might be interesting in case of data
that is largely static and bandwidth-constrained environments.
Appendix C. Changes between revisions
(To be removed by RFC editor prior to publication)
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 [sn] 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
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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
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
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o Text updates throughout
Authors' Addresses
Alexander Clemm
Huawei
Email: ludwig@clemm.org
Eric Voit
Cisco Systems
Email: evoit@cisco.com
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
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