NETCONF Support for Event Notifications
draft-ietf-netconf-netconf-event-notifications-13
The information below is for an old version of the document.
Document | Type |
This is an older version of an Internet-Draft that was ultimately published as RFC 8640.
|
|
---|---|---|---|
Authors | Eric Voit , Alexander Clemm , Alberto Gonzalez Prieto , Einar Nilsen-Nygaard , Ambika Tripathy | ||
Last updated | 2018-10-04 | ||
Replaces | draft-gonzalez-netconf-event-notifications | ||
RFC stream | Internet Engineering Task Force (IETF) | ||
Formats | |||
Reviews |
TSVART Last Call review
(of
-17)
by Wesley Eddy
Ready w/issues
YANGDOCTORS Last Call review
(of
-16)
by Reshad Rahman
Ready w/issues
|
||
Additional resources | Mailing list discussion | ||
Stream | WG state | In WG Last Call | |
Document shepherd | (None) | ||
IESG | IESG state | Became RFC 8640 (Proposed Standard) | |
Consensus boilerplate | Yes | ||
Telechat date | (None) | ||
Responsible AD | (None) | ||
Send notices to | (None) |
draft-ietf-netconf-netconf-event-notifications-13
NETCONF E. Voit Internet-Draft Cisco Systems Intended status: Standards Track A. Clemm Expires: April 7, 2019 Huawei A. Gonzalez Prieto Microsoft E. Nilsen-Nygaard A. Tripathy Cisco Systems October 4, 2018 NETCONF Support for Event Notifications draft-ietf-netconf-netconf-event-notifications-13 Abstract This document provides a NETCONF binding to the dynamic subscription capability of both subscribed notifications and YANG push. RFC Editor note: please replace the four 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. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on April 7, 2019. Copyright Notice Copyright (c) 2018 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info) in effect on the date of Voit, et al. Expires April 7, 2019 [Page 1] Internet-Draft NETCONF-notif October 2018 publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Compatibility with RFC-5277's create-subscription . . . . . . 3 4. Mandatory XML, event stream and datastore support . . . . . . 3 5. NETCONF connectivity and the Dynamic Subscriptions . . . . . 4 6. Notification Messages . . . . . . . . . . . . . . . . . . . . 4 7. Dynamic Subscriptions and RPC Error Responses . . . . . . . . 4 8. Security Considerations . . . . . . . . . . . . . . . . . . . 5 9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 6 10. Notes to the RFC Editor . . . . . . . . . . . . . . . . . . . 6 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 6 11.1. Normative References . . . . . . . . . . . . . . . . . . 6 11.2. Informative References . . . . . . . . . . . . . . . . . 7 Appendix A. Examples . . . . . . . . . . . . . . . . . . . . . . 7 A.1. Event Stream Discovery . . . . . . . . . . . . . . . . . 7 A.2. Dynamic Subscriptions . . . . . . . . . . . . . . . . . . 8 A.3. Subscription State Notifications . . . . . . . . . . . . 12 A.4. Filter Examples . . . . . . . . . . . . . . . . . . . . . 14 Appendix B. Changes between revisions . . . . . . . . . . . . . 15 B.1. v11 to v13 . . . . . . . . . . . . . . . . . . . . . . . 15 B.2. v10 to v11 . . . . . . . . . . . . . . . . . . . . . . . 16 B.3. v09 to v10 . . . . . . . . . . . . . . . . . . . . . . . 16 B.4. v08 to v09 . . . . . . . . . . . . . . . . . . . . . . . 16 B.5. v07 to v08 . . . . . . . . . . . . . . . . . . . . . . . 16 B.6. v06 to v07 . . . . . . . . . . . . . . . . . . . . . . . 16 B.7. v05 to v06 . . . . . . . . . . . . . . . . . . . . . . . 16 B.8. v03 to v04 . . . . . . . . . . . . . . . . . . . . . . . 16 B.9. v01 to v03 . . . . . . . . . . . . . . . . . . . . . . . 17 B.10. v00 to v01 . . . . . . . . . . . . . . . . . . . . . . . 17 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 17 1. Introduction This document provides a binding for events streamed over the NETCONF protocol [RFC6241] for dynamic subscriptions as defined in [I-D.draft-ietf-netconf-subscribed-notifications]. In addition, as [I-D.ietf-netconf-yang-push] is itself built upon [I-D.draft-ietf-netconf-subscribed-notifications], this document Voit, et al. Expires April 7, 2019 [Page 2] Internet-Draft NETCONF-notif October 2018 enables a NETCONF client to request via a dynamic subscription and receive updates from a YANG datastore located on a NETCONF server. 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. 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 cannot support both this specification and a subscription established by [RFC5277]'s "create-subscription" RPC. To protect against any attempts to use a single NETCONF transport session in this way: o A solution must reply with the [RFC6241] error "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] error "operation-not- supported" if an "establish-subscription" request is 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] is mandatory to support. This indicates that XML is a valid encoding for RPCs, state change notifications, and subscribed content. Voit, et al. Expires April 7, 2019 [Page 3] Internet-Draft NETCONF-notif October 2018 A NETCONF publisher supporting event stream subscription via [I-D.draft-ietf-netconf-subscribed-notifications] MUST support the "NETCONF" event stream identified in that draft. 5. NETCONF connectivity and the Dynamic Subscriptions For a dynamic subscription, if the NETCONF session involved with the "establish-subscription" terminates, the subscription MUST be terminated. For a dynamic subscription a "modify-subscription", "delete- subscription", or "resynch-subscription" RPC MUST be sent using same the 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" MUST be populated with the event occurrence time. 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 Management of dynamic subscriptions occurs via RPCs as defined in [I-D.ietf-netconf-yang-push] and [I-D.draft-ietf-netconf-subscribed-notifications]. When an RPC error occurs, 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 of "operation-failed". o an "error-severity" of "error" (this MAY but does not have to 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 for general subscriptions, and [I-D.ietf-netconf-yang-push] Appendix A.1, for datastore subscriptions. The specific identity to use depends on the RPC for which the error occurred. Viable errors for different RPCs are as follows: Voit, et al. Expires April 7, 2019 [Page 4] Internet-Draft NETCONF-notif October 2018 RPC use base identity ---------------------- ---------------------------- establish-subscription establish-subscription-error modify-subscription modify-subscription-error delete-subscription delete-subscription-error kill-subscription kill-subscription-error resynch-subscription resynch-subscription-error Each error identity will be inserted as the "error-app-tag" using JSON encoding following the form <modulename>:<identityname>. An example of such as valid encoding would be "ietf-subscribed- notifications:no-such-subscription". 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 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 "error-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 "resynch-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. 8. Security Considerations If a malicious or buggy 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 Voit, et al. Expires April 7, 2019 [Page 5] Internet-Draft NETCONF-notif October 2018 publisher MAY also suspend or terminate a subset of the active subscriptions on that NETCONF session. 9. 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, and Guangying Zheng. 10. Notes to the RFC Editor This section can be removed by the RFC editor after the requests have been performed. RFC 6241 need to be updated. RFC-6241 refers to RFC-5277 which says that a notification message can only be sent after a successful "create-subscription". This text must be modified to also allow notification messages be sent after a successful "establish- subscription". 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", draft-ietf-netconf-subscribed- notifications-17 (work in progress), September 2018. [I-D.ietf-netconf-yang-push] Clemm, Alexander., Voit, Eric., Gonzalez Prieto, Alberto., Tripathy, A., Nilsen-Nygaard, E., Bierman, A., and B. Lengyel, "YANG Datastore Subscription", September 2018, <https://datatracker.ietf.org/doc/ draft-ietf-netconf-yang-push/>. [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>. Voit, et al. Expires April 7, 2019 [Page 6] Internet-Draft NETCONF-notif October 2018 [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. 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: <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 Voit, et al. Expires April 7, 2019 [Page 7] Internet-Draft NETCONF-notif October 2018 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. +------------+ +-----------+ | 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: Voit, et al. Expires April 7, 2019 [Page 8] Internet-Draft NETCONF-notif October 2018 <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>NETCONF</stream> <stream-xpath-filter xmlns:ds="http://example.com/events"> /ds:foo/ </stream-xpath-filter> <dscp>10</dscp> </establish-subscription> </rpc> Figure 3: establish-subscription request (a) 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>operation-failed</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 Voit, et al. Expires April 7, 2019 [Page 9] Internet-Draft NETCONF-notif October 2018 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. +------------+ +-----------+ | 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.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. Voit, et al. Expires April 7, 2019 [Page 10] Internet-Draft NETCONF-notif October 2018 <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:ds="http://example.com/datastore"> /ds:foo/ds:bar </yp:datastore-xpath-filter> <yp:periodic> <yp:period>500</yp:period> </yp:periodic> </modify-subscription> </rpc> Figure 7: Subscription modification request (c) 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>operation-failed</error-tag> <error-severity>error</error-severity> <error-app-tag> ietf-yang-push:period-unsupported </error-app-tag> <error-info xmlns="urn:ietf:params:xml:ns:yang:ietf-yang-push"> <modify-subscription-datastore-error-info> <period-hint> 3000 </period-hint> </modify-subscription-datastore-error-info> </error-info> </rpc-error> </rpc-reply> Figure 8: Modify subscription failure with Hint (d) Voit, et al. Expires April 7, 2019 [Page 11] Internet-Draft NETCONF-notif October 2018 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. 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>operation-failed</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]). Voit, et al. Expires April 7, 2019 [Page 12] Internet-Draft NETCONF-notif October 2018 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 if 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> <transport xmlns:nsn= "urn:ietf:params:xml:ns:yang:ietf-netconf-subscribed-notifications"> nsn:netconf <transport> <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 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". Voit, et al. Expires April 7, 2019 [Page 13] Internet-Draft NETCONF-notif October 2018 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: <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: Voit, et al. Expires April 7, 2019 [Page 14] Internet-Draft NETCONF-notif October 2018 <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[protocol-error-reason="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: <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. 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 Voit, et al. Expires April 7, 2019 [Page 15] Internet-Draft NETCONF-notif October 2018 B.2. v10 to v11 o Configured removed. B.3. v09 to v10 o Tweaks to examples and text. o Downshifted state names. o Removed address from examples. B.4. 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.5. v07 to v08 o Tweaks and clarification on :interleave. B.6. v06 to v07 o XML encoding and operational datastore mandatory. o Error mechanisms and examples updated. B.7. 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.8. 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 Voit, et al. Expires April 7, 2019 [Page 16] Internet-Draft NETCONF-notif October 2018 B.9. v01 to v03 o Text simplifications throughout o v02 had no meaningful changes B.10. 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 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 Voit, et al. Expires April 7, 2019 [Page 17]