Internet DRAFT - draft-ietf-netconf-netconf-event-notifications
draft-ietf-netconf-netconf-event-notifications
NETCONF E. Voit
Internet-Draft Cisco Systems
Intended status: Standards Track A. Clemm
Expires: November 20, 2019 Huawei
A. Gonzalez Prieto
Microsoft
E. Nilsen-Nygaard
A. Tripathy
Cisco Systems
May 19, 2019
Dynamic subscription to YANG Events and Datastores over NETCONF
draft-ietf-netconf-netconf-event-notifications-22
Abstract
This document provides a Network Configuration Protocol (NETCONF)
binding to the dynamic subscription capability of both subscribed
notifications and YANG-Push.
RFC Editor note: please replace the references to pre-RFC normative
drafts with the actual assigned RFC numbers.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Compatibility with RFC-5277's create-subscription . . . . . . 3
4. Mandatory XML, event stream and datastore support . . . . . . 4
5. NETCONF connectivity and the Dynamic Subscriptions . . . . . 4
6. Notification Messages . . . . . . . . . . . . . . . . . . . . 4
7. Dynamic Subscriptions and RPC Error Responses . . . . . . . . 5
8. Security Considerations . . . . . . . . . . . . . . . . . . . 7
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 7
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
11.1. Normative References . . . . . . . . . . . . . . . . . . 7
11.2. Informative References . . . . . . . . . . . . . . . . . 8
Appendix A. Examples . . . . . . . . . . . . . . . . . . . . . . 8
A.1. Event Stream Discovery . . . . . . . . . . . . . . . . . 8
A.2. Dynamic Subscriptions . . . . . . . . . . . . . . . . . . 9
A.3. Subscription State Notifications . . . . . . . . . . . . 14
A.4. Filter Examples . . . . . . . . . . . . . . . . . . . . . 15
Appendix B. Changes between revisions . . . . . . . . . . . . . 17
B.1. v21 to v22 . . . . . . . . . . . . . . . . . . . . . . . 17
B.2. v20 to v21 . . . . . . . . . . . . . . . . . . . . . . . 17
B.3. v19 to v20 . . . . . . . . . . . . . . . . . . . . . . . 17
B.4. v17 to v19 . . . . . . . . . . . . . . . . . . . . . . . 17
B.5. v16 to v17 . . . . . . . . . . . . . . . . . . . . . . . 17
B.6. v15 to v16 . . . . . . . . . . . . . . . . . . . . . . . 18
B.7. v14 to v15 . . . . . . . . . . . . . . . . . . . . . . . 18
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B.8. v13 to v14 . . . . . . . . . . . . . . . . . . . . . . . 18
B.9. v11 to v13 . . . . . . . . . . . . . . . . . . . . . . . 18
B.10. v10 to v11 . . . . . . . . . . . . . . . . . . . . . . . 18
B.11. v09 to v10 . . . . . . . . . . . . . . . . . . . . . . . 18
B.12. v08 to v09 . . . . . . . . . . . . . . . . . . . . . . . 18
B.13. v07 to v08 . . . . . . . . . . . . . . . . . . . . . . . 18
B.14. v06 to v07 . . . . . . . . . . . . . . . . . . . . . . . 19
B.15. v05 to v06 . . . . . . . . . . . . . . . . . . . . . . . 19
B.16. v03 to v04 . . . . . . . . . . . . . . . . . . . . . . . 19
B.17. v01 to v03 . . . . . . . . . . . . . . . . . . . . . . . 19
B.18. v00 to v01 . . . . . . . . . . . . . . . . . . . . . . . 19
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 19
1. Introduction
This document specifies the binding of a stream of events which form
part of a dynamic subscription to the NETCONF protocol [RFC6241].
Dynamic subscriptions are defined in
[I-D.draft-ietf-netconf-subscribed-notifications]. In addition, as
[I-D.draft-ietf-netconf-yang-push] is itself built upon
[I-D.draft-ietf-netconf-subscribed-notifications], this document
enables a NETCONF client to request via a dynamic subscription and
receive updates from a YANG datastore located on a NETCONF server.
This document assumes that the reader is familiar with the
terminology and concepts defined in
[I-D.draft-ietf-netconf-subscribed-notifications].
2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
The following terms are defined in
[I-D.draft-ietf-netconf-subscribed-notifications]: dynamic
subscription, event stream, notification message, publisher,
receiver, subscriber, subscription. No additional terms are defined.
3. Compatibility with RFC-5277's create-subscription
A publisher is allowed to concurrently support dynamic subscription
RPCs of [I-D.draft-ietf-netconf-subscribed-notifications] at the same
time as [RFC5277]'s "create-subscription" RPC. However a single
NETCONF transport session MUST NOT support both this specification
and a subscription established by [RFC5277]'s "create-subscription"
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RPC. To protect against any attempts to use a single NETCONF
transport session in this way:
o A solution MUST reply with the [RFC6241] "rpc-error" element
containing the "error-tag" value of "operation-not-supported" if a
"create-subscription" RPC is received on a NETCONF session where
an [I-D.draft-ietf-netconf-subscribed-notifications] established
subscription exists.
o A solution MUST reply with the [RFC6241] "rpc-error" element
containing the "error-tag" value of "operation-not-supported" if
an "establish-subscription" request has been received on a NETCONF
session where the "create-subscription" RPC has successfully
[RFC5277] created a subscription.
If a publisher supports this specification but not subscriptions via
[RFC5277], the publisher MUST NOT advertise
"urn:ietf:params:netconf:capability:notification:1.0".
4. Mandatory XML, event stream and datastore support
The "encode-xml" feature of
[I-D.draft-ietf-netconf-subscribed-notifications] MUST be supported.
This indicates that XML is a valid encoding for RPCs, state change
notifications, and subscribed content.
A NETCONF publisher supporting event stream subscription via
[I-D.draft-ietf-netconf-subscribed-notifications] MUST support the
"NETCONF" event stream identified in that document.
5. NETCONF connectivity and the Dynamic Subscriptions
Management of dynamic subscriptions occurs via RPCs as defined in
[I-D.draft-ietf-netconf-yang-push] and
[I-D.draft-ietf-netconf-subscribed-notifications]. For a dynamic
subscription, if the NETCONF session involved with the "establish-
subscription" terminates, the subscription MUST be terminated.
For a dynamic subscription, any "modify-subscription", "delete-
subscription", or "resync-subscription" RPCs MUST be sent using the
same NETCONF session upon which the referenced subscription was
established.
6. Notification Messages
Notification messages transported over the NETCONF protocol MUST be
encoded in a <notification> message as defined within [RFC5277],
Section 4. And per [RFC5277]'s "eventTime" object definition, the
"eventTime" is populated with the event occurrence time.
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For dynamic subscriptions, all notification messages MUST use the
NETCONF transport session used by the "establish-subscription" RPC.
7. Dynamic Subscriptions and RPC Error Responses
When an RPC error occurs as defined in
[I-D.draft-ietf-netconf-subscribed-notifications] Section 2.4.6 and
[I-D.draft-ietf-netconf-yang-push] Appendix A, the NETCONF RPC reply
MUST include an "rpc-error" element per [RFC6241] with the error
information populated as follows:
o An "error-type" node of "application".
o An "error-tag" node with the value being a string that corresponds
to an identity associated with the error. For the mechanisms
specified in this document, this "error-tag" will come from one of
two places. Either it will correspond to the error identities
within [I-D.draft-ietf-netconf-subscribed-notifications] section
2.4.6 for general subscription errors:
error identity uses error-tag
---------------------- --------------
dscp-unavailable invalid-value
encoding-unsupported invalid-value
filter-unsupported invalid-value
insufficient-resources resource-denied
no-such-subscription invalid-value
replay-unsupported operation-not-supported
Or this "error-tag" will correspond to the error identities within
[I-D.draft-ietf-netconf-yang-push] Appendix A.1 for subscription
errors specific to YANG datastores:
error identity uses error-tag
---------------------- --------------
cant-exclude operation-not-supported
datastore-not-subscribable invalid-value
no-such-subscription-resync invalid-value
on-change-unsupported operation-not-supported
on-change-sync-unsupported operation-not-supported
period-unsupported invalid-value
update-too-big too-big
sync-too-big too-big
unchanging-selection operation-failed
o an "error-severity" of "error" (this MAY be included).
o an "error-app-tag" node with the value being a string that
corresponds to an identity associated with the error, as defined
in [I-D.draft-ietf-netconf-subscribed-notifications] section 2.4.6
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for general subscriptions, and [I-D.draft-ietf-netconf-yang-push]
Appendix A.1, for datastore subscriptions. The specific identity
to use depends on the RPC for which the error occurred. Each
error identity will be inserted as the "error-app-tag" following
the form <modulename>:<identityname>. An example of such as valid
encoding would be "ietf-subscribed-notifications:no-such-
subscription". Viable errors for different RPCs are as follows:
RPC have base identity
---------------------- ----------------------------
establish-subscription establish-subscription-error
modify-subscription modify-subscription-error
delete-subscription delete-subscription-error
kill-subscription delete-subscription-error
resync-subscription resync-subscription-error
o In case of error responses to an "establish-subscription" or
"modify-subscription" request there is the option of including an
"error-info" node. This node may contain XML-encoded data with
hints for parameter settings that might lead to successful RPC
requests in the future. Following are the yang-data structures
from [I-D.draft-ietf-netconf-subscribed-notifications] and
[I-D.draft-ietf-netconf-yang-push] which may be returned:
establish-subscription returns hints in yang-data structure
---------------------- ------------------------------------
target: event stream establish-subscription-stream-error-info
target: datastore establish-subscription-datastore-error-info
modify-subscription returns hints in yang-data structure
---------------------- ------------------------------------
target: event stream modify-subscription-stream-error-info
target: datastore modify-subscription-datastore-error-info
The yang-data included within "error-info" SHOULD NOT include the
optional leaf "reason", as such a leaf would be redundant
with information that is already placed within the
"error-app-tag".
In case of an rpc error resulting from a "delete-subscription",
"kill-subscription", or "resync-subscription" request, no "error-
info" needs to be included, as the "subscription-id" is the only RPC
input parameter and no hints regarding this RPC input parameters need
to be provided.
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8. Security Considerations
This document does not introduce additional Security Considerations
for dynamic subscriptions beyond those discussed in
[I-D.draft-ietf-netconf-subscribed-notifications]. But there is one
consideration worthy of more refinement based on the connection
oriented nature of the NETCONF protocol. Specifically, if a buggy or
compromised NETCONF subscriber sends a number of "establish-
subscription" requests, then these subscriptions accumulate and may
use up system resources. In such a situation, subscriptions MAY be
terminated by terminating the underlying NETCONF session. The
publisher MAY also suspend or terminate a subset of the active
subscriptions on that NETCONF session in order to reclaim resources
and preserve normal operation for the other subscriptions.
9. IANA Considerations
This document has no actions for IANA.
10. Acknowledgments
We wish to acknowledge the helpful contributions, comments, and
suggestions that were received from: Andy Bierman, Yan Gang, Sharon
Chisholm, Hector Trevino, Peipei Guo, Susan Hares, Tim Jenkins,
Balazs Lengyel, Martin Bjorklund, Mahesh Jethanandani, Kent Watsen,
Qin Wu, and Guangying Zheng.
11. References
11.1. Normative References
[I-D.draft-ietf-netconf-subscribed-notifications]
Voit, E., Clemm, A., Gonzalez Prieto, A., Tripathy, A.,
and E. Nilsen-Nygaard, "Customized Subscriptions to a
Publisher's Event Streams", September 2018,
<https://datatracker.ietf.org/doc/
draft-ietf-netconf-subscribed-notifications/>.
[I-D.draft-ietf-netconf-yang-push]
Clemm, Alexander., Voit, Eric., Gonzalez Prieto, Alberto.,
Tripathy, A., Nilsen-Nygaard, E., Bierman, A., and B.
Lengyel, "YANG Datastore Subscription", September 2018,
<https://datatracker.ietf.org/doc/
draft-ietf-netconf-yang-push/>.
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[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[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>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
11.2. Informative References
[RFC8347] Liu, X., Ed., Kyparlis, A., Parikh, R., Lindem, A., and M.
Zhang, "A YANG Data Model for the Virtual Router
Redundancy Protocol (VRRP)", RFC 8347,
DOI 10.17487/RFC8347, March 2018,
<https://www.rfc-editor.org/info/rfc8347>.
[XPATH] Clark, J. and S. DeRose, "XML Path Language (XPath)
Version 1.0", November 1999,
<http://www.w3.org/TR/1999/REC-xpath-19991116>.
Appendix A. Examples
This section is non-normative. Additionally the subscription "id"
values of 22, 23, and 39 used below are just examples. In
production, the actual values of "id" may not be small integers.
A.1. Event Stream Discovery
As defined in [I-D.draft-ietf-netconf-subscribed-notifications] an
event stream exposes a continuous set of events available for
subscription. A NETCONF client can retrieve the list of available
event streams from a NETCONF publisher using the "get" operation
against the top-level container "/streams" defined in
[I-D.draft-ietf-netconf-subscribed-notifications] Section 3.1.
The following example illustrates the retrieval of the list of
available event streams:
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<rpc message-id="101"
xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
<get>
<filter type="subtree">
<streams
xmlns="urn:ietf:params:xml:ns:yang:ietf-subscribed-notifications"/>
</filter>
</get>
</rpc>
Figure 1: Get streams request
After such a request, the NETCONF publisher returns a list of event
streams available, as well as additional information which might
exist in the container.
A.2. Dynamic Subscriptions
A.2.1. Establishing Dynamic Subscriptions
The following figure shows two successful "establish-subscription"
RPC requests as per
[I-D.draft-ietf-netconf-subscribed-notifications]. The first request
is given a subscription "id" of 22, the second, an "id" of 23.
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+------------+ +-----------+
| Subscriber | | Publisher |
+------------+ +-----------+
| |
| Capability Exchange |
|<---------------------------->|
| |
| |
| establish-subscription |
|----------------------------->| (a)
| RPC Reply: OK, id = 22 |
|<-----------------------------| (b)
| |
| notification message (for 22)|
|<-----------------------------|
| |
| |
| establish-subscription |
|----------------------------->|
| notification message (for 22)|
|<-----------------------------|
| RPC Reply: OK, id = 23 |
|<-----------------------------|
| |
| |
| notification message (for 22)|
|<-----------------------------|
| notification message (for 23)|
|<-----------------------------|
| |
Figure 2: Multiple subscriptions over a NETCONF session
To provide examples of the information being transported, example
messages for interactions (a) and (b) in Figure 2 are detailed below:
<rpc message-id="102" xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
<establish-subscription
xmlns="urn:ietf:params:xml:ns:yang:ietf-subscribed-notifications">
<stream-xpath-filter xmlns:ex="http://example.com/events">
/ex:foo/
</stream-xpath-filter>
<stream>NETCONF</stream>
<dscp>10</dscp>
</establish-subscription>
</rpc>
Figure 3: establish-subscription request (a)
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As NETCONF publisher was able to fully satisfy the request (a), the
publisher sends the subscription "id" of the accepted subscription
within message (b):
<rpc-reply message-id="102"
xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
<id
xmlns="urn:ietf:params:xml:ns:yang:ietf-subscribed-notifications">
22
</id>
</rpc-reply>
Figure 4: establish-subscription success (b)
If the NETCONF publisher had not been able to fully satisfy the
request, or subscriber has no authorization to establish the
subscription, the publisher would have sent an RPC error response.
For instance, if the "dscp" value of 10 asserted by the subscriber in
Figure 3 proved unacceptable, the publisher may have returned:
<rpc-reply message-id="102"
xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
<rpc-error>
<error-type>application</error-type>
<error-tag>invalid-value</error-tag>
<error-severity>error</error-severity>
<error-app-tag>
ietf-subscribed-notifications:dscp-unavailable
</error-app-tag>
</rpc-error>
</rpc-reply>
Figure 5: an unsuccessful establish subscription
The subscriber can use this information in future attempts to
establish a subscription.
A.2.2. Modifying Dynamic Subscriptions
An existing subscription may be modified. The following exchange
shows a negotiation of such a modification via several exchanges
between a subscriber and a publisher. This negotiation consists of a
failed RPC modification request/response, followed by a successful
one.
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+------------+ +-----------+
| Subscriber | | Publisher |
+------------+ +-----------+
| |
| notification message (for 23)|
|<-----------------------------|
| |
| modify-subscription (id = 23)|
|----------------------------->| (c)
| RPC error (with hint) |
|<-----------------------------| (d)
| |
| modify-subscription (id = 23)|
|----------------------------->|
| RPC Reply: OK |
|<-----------------------------|
| |
| notification message (for 23)|
|<-----------------------------|
| |
Figure 6: Interaction model for successful subscription modification
If the subscription being modified in Figure 6 is a datastore
subscription as per [I-D.draft-ietf-netconf-yang-push], the
modification request made in (c) may look like that shown in
Figure 7. As can be seen, the modifications being attempted are the
application of a new XPath filter as well as the setting of a new
periodic time interval.
<rpc message-id="303"
xmlns="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">
<id>23</id>
<yp:datastore-xpath-filter xmlns:ex="http://example.com/datastore">
/ex:foo/ex:bar
</yp:datastore-xpath-filter>
<yp:periodic>
<yp:period>500</yp:period>
</yp:periodic>
</modify-subscription>
</rpc>
Figure 7: Subscription modification request (c)
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If the NETCONF publisher can satisfy both changes, the publisher
sends a positive result for the RPC. If the NETCONF publisher cannot
satisfy either of the proposed changes, the publisher sends an RPC
error response (d). The following is an example RPC error response
for (d) which includes a hint. This hint is an alternative time
period value which might have resulted in a successful modification:
<rpc-reply message-id="303"
xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
<rpc-error>
<error-type>application</error-type>
<error-tag>invalid-value</error-tag>
<error-severity>error</error-severity>
<error-app-tag>
ietf-yang-push:period-unsupported
</error-app-tag>
<error-info>
<modify-subscription-datastore-error-info
xmlns="urn:ietf:params:xml:ns:yang:ietf-yang-push">
<period-hint>
3000
</period-hint>
</modify-subscription-datastore-error-info>
</error-info>
</rpc-error>
</rpc-reply>
Figure 8: Modify subscription failure with hint (d)
A.2.3. Deleting Dynamic Subscriptions
The following demonstrates deleting a subscription. This
subscription may have been to either a stream or a datastore.
<rpc message-id="103"
xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
<delete-subscription
xmlns="urn:ietf:params:xml:ns:yang:ietf-subscribed-notifications">
<id>22</id>
</delete-subscription>
</rpc>
Figure 9: Delete subscription
If the NETCONF publisher can satisfy the request, the publisher
replies with success to the RPC request.
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If the NETCONF publisher cannot satisfy the request, the publisher
sends an error-rpc element indicating the modification didn't work.
Figure 10 shows a valid response for existing valid subscription
"id", but that subscription "id" was created on a different NETCONF
transport session:
<rpc-reply message-id="103"
xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
<rpc-error>
<error-type>application</error-type>
<error-tag>invalid-value</error-tag>
<error-severity>error</error-severity>
<error-app-tag>
ietf-subscribed-notifications:no-such-subscription
</error-app-tag>
</rpc-error>
</rpc-reply>
Figure 10: Unsuccessful delete subscription
A.3. Subscription State Notifications
A publisher will send subscription state notifications for dynamic
subscriptions according to the definitions within
[I-D.draft-ietf-netconf-subscribed-notifications].
A.3.1. subscription-modified
As per Section 2.7.2 of
[I-D.draft-ietf-netconf-subscribed-notifications], a "subscription-
modified" might be sent over NETCONF if the definition of a
configured filter changes. A subscription state notification encoded
in XML would look like:
<notification xmlns="urn:ietf:params:xml:ns:netconf:notification:1.0">
<eventTime>2007-09-01T10:00:00Z</eventTime>
<subscription-modified
xmlns="urn:ietf:params:xml:ns:yang:ietf-subscribed-notifications">
<id>39</id>
<stream-xpath-filter xmlns:ex="http://example.com/events">
/ex:foo
</stream-xpath-filter>
<stream>NETCONF</stream>
</subscription-modified>
</notification>
Figure 11: subscription-modified subscription state notification
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A.3.2. subscription-resumed, and replay-complete
A "subscription-resumed" would look like:
<notification
xmlns="urn:ietf:params:xml:ns:netconf:notification:1.0">
<eventTime>2007-09-01T10:00:00Z</eventTime>
<subscription-resumed
xmlns="urn:ietf:params:xml:ns:yang:ietf-subscribed-notifications">
<id>39</id>
</subscription-resumed>
</notification>
Figure 12: subscription-resumed notification in XML
The "replay-complete" is virtually identical, with "subscription-
resumed" simply being replaced by "replay-complete".
A.3.3. subscription-terminated and subscription-suspended
A "subscription-terminated" would look like:
<notification
xmlns="urn:ietf:params:xml:ns:netconf:notification:1.0">
<eventTime>2007-09-01T10:00:00Z</eventTime>
<subscription-terminated
xmlns="urn:ietf:params:xml:ns:yang:ietf-subscribed-notifications">
<id>39</id>
<reason>
suspension-timeout
</reason>
</subscription-terminated>
</notification>
Figure 13: subscription-terminated subscription state notification
The "subscription-suspended" is virtually identical, with
"subscription-terminated" simply being replaced by "subscription-
suspended".
A.4. Filter Examples
This section provides examples which illustrate both XPath and
subtree methods of filtering event record contents. The examples are
based on the YANG notification "vrrp-protocol-error-event" as defined
per the ietf-vrrp.yang model within [RFC8347]. Event records based
on this specification which are generated by the publisher might
appear as:
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<notification xmlns="urn:ietf:params:xml:ns:netconf:notification:1.0">
<eventTime>2018-09-14T08:22:33.44Z</eventTime>
<vrrp-protocol-error-event
xmlns="urn:ietf:params:xml:ns:yang:ietf-vrrp">
<protocol-error-reason>checksum-error</protocol-error-reason>
</vrrp-protocol-error-event>
</notification>
Figure 14: RFC 8347 (VRRP) - Example Notification
Suppose a subscriber wanted to establish a subscription which only
passes instances of event records where there is a "checksum-error"
as part of a VRRP protocol event. Also assume the publisher places
such event records into the NETCONF stream. To get a continuous
series of matching event records, the subscriber might request the
application of an XPath filter against the NETCONF stream. An
"establish-subscription" RPC to meet this objective might be:
<rpc message-id="601" xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
<establish-subscription
xmlns="urn:ietf:params:xml:ns:yang:ietf-subscribed-notifications">
<stream>NETCONF</stream>
<stream-xpath-filter xmlns="urn:ietf:params:xml:ns:yang:ietf-vrrp">
/vrrp-protocol-error-event[
vrrp:protocol-error-reason="vrrp:checksum-error"]
</stream-xpath-filter>
</establish-subscription>
</rpc>
Figure 15: Establishing a subscription error reason via XPath
For more examples of XPath filters, see [XPATH].
Suppose the "establish-subscription" in Figure 15 was accepted. And
suppose later a subscriber decided they wanted to broaden this
subscription cover to all VRRP protocol events (i.e., not just those
with a "checksum error"). The subscriber might attempt to modify the
subscription in a way which replaces the XPath filter with a subtree
filter which sends all VRRP protocol events to a subscriber. Such a
"modify-subscription" RPC might look like:
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<rpc message-id="602" xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
<modify-subscription
xmlns="urn:ietf:params:xml:ns:yang:ietf-subscribed-notifications">
<id>99</id>
<stream-subtree-filter>
<vrrp-protocol-error-event
xmlns="urn:ietf:params:xml:ns:yang:ietf-vrrp"/>
</stream-subtree-filter>
</modify-subscription>
</rpc>
Figure 16
For more examples of subtree filters, see [RFC6241], section 6.4.
Appendix B. Changes between revisions
(To be removed by RFC editor prior to publication)
B.1. v21 to v22
o Added "is".
B.2. v20 to v21
o Including Tom Petch's text to resolve the meaning of 'binding'.
o A few small wording tweaks.
B.3. v19 to v20
o Notes to RFC editor removed, consideration moved under Figure 10
in SN.
B.4. v17 to v19
o Per Benjamin Kaduk's discuss on SN, adjusted IPR to
pre5378Trust200902
B.5. v16 to v17
o During the SN YANG Doctor review, a suggestion was made to update
the error-tags to make the mechanism work with embedded NETCONF
and RESTCONF error reporting.
o Minor text tweaks from review.
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B.6. v15 to v16
o During the shepherd review, two clarifications were requested
which do not impact the technical details of this document. These
clarifications were: (a) further describing that dynamic
subscriptions can have state change notifications, and (b) more
details about the recommended text refinement desired for RFC6241.
B.7. v14 to v15
o Per Kent's request, added name attribute to artwork. This would
be needed for an automated extraction.
B.8. v13 to v14
o Title change.
B.9. v11 to v13
o Subscription identifier renamed to id.
o Appendix A.4 for filter examples
o for v13, Tweak of example to /foo/bar
B.10. v10 to v11
o Configured removed.
B.11. v09 to v10
o Tweaks to examples and text.
o Downshifted state names.
o Removed address from examples.
B.12. v08 to v09
o Tweaks based on Kent's comments.
o Updated examples in Appendix A. And updates to some object names
based on changes in the subscribed-notifications draft.
o Added a YANG model for the NETCONF identity.
B.13. v07 to v08
o Tweaks and clarification on :interleave.
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B.14. v06 to v07
o XML encoding and operational datastore mandatory.
o Error mechanisms and examples updated.
B.15. v05 to v06
o Moved examples to appendices
o All examples rewritten based on namespace learnings
o Normative text consolidated in front
o Removed all mention of JSON
o Call home process detailed
o Note: this is a major revision attempting to cover those comments
received from two week review.
B.16. v03 to v04
o Added additional detail to "configured subscriptions"
o Added interleave capability
o Adjusted terminology to that in draft-ietf-netconf-subscribed-
notifications
o Corrected namespaces in examples
B.17. v01 to v03
o Text simplifications throughout
o v02 had no meaningful changes
B.18. v00 to v01
o Added Call Home in solution for configured subscriptions.
o Clarified support for multiple subscription on a single session.
No need to support multiple create-subscription.
o Added mapping between terminology in yang-push and [RFC6241] (the
one followed in this document).
o Editorial improvements.
Authors' Addresses
Eric Voit
Cisco Systems
Email: evoit@cisco.com
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Alexander Clemm
Huawei
Email: ludwig@clemm.org
Alberto Gonzalez Prieto
Microsoft
Email: alberto.gonzalez@microsoft.com
Einar Nilsen-Nygaard
Cisco Systems
Email: einarnn@cisco.com
Ambika Prasad Tripathy
Cisco Systems
Email: ambtripa@cisco.com
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