| NETCONF | A. Gonzalez Prieto |
| Internet-Draft | VMware |
| Intended status: Standards Track | E. Voit |
| Expires: August 26, 2018 | Cisco Systems |
| A. Clemm | |
| Huawei | |
| E. Nilsen-Nygaard | |
| A. Tripathy | |
| Cisco Systems | |
| February 22, 2018 |
NETCONF Support for Event Notifications
draft-ietf-netconf-netconf-event-notifications-08
This document provides a NETCONF binding to subscribed notifications and to YANG push.
RFC Editor note: please replace the four references to pre-RFC normative drafts with the actual assigned RFC numbers.
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 August 26, 2018.
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 publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License.
This document provides a binding for events streamed over the NETCONF protocol [RFC6241] as per [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 enables a NETCONF client to request and receive updates from a YANG datastore located on a NETCONF server.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119.
The following terms are defined in [I-D.draft-ietf-netconf-subscribed-notifications]: notification message, stream, publisher, receiver, subscriber, subscription, configured subscription.
To support multiple subscriptions on a single session, a NETCONF publisher MUST support the :interleave capability as defined in [RFC5277]. Such support MUST be indicated by the following capability: "urn:ietf:params:netconf:capability:interleave:1.0". Advertisement of both the :interleave capability and "urn:ietf:params:xml:ns:yang:ietf-subscribed-notifications" within a NETCONF capability exchange MUST indicate that a NETCONF publisher is able to receive, process, and respond to NETCONF requests and [I-D.draft-ietf-netconf-subscribed-notifications] subscription operations.
A publisher is allowed to concurrently support both [I-D.draft-ietf-netconf-subscribed-notifications] and [RFC5277]'s "create-subscription" RPC, however this support MUST NOT happen on a single transport NETCONF session. To accomplish this:
A NETCONF publisher MUST support XML encoding of RPCs and Notifications.
A NETCONF publisher supporting [I-D.draft-ietf-netconf-subscribed-notifications] MUST support the "NETCONF" event stream identified in that draft.
A NETCONF publisher supporting [I-D.ietf-netconf-yang-push] MUST support the operational state datastore as defined by [I.D.draft-ietf-netmod-revised-datastores].
For dynamic subscriptions, if the NETCONF session involved with the "establish-subscription" terminates, the subscription MUST be deleted.
For a configured subscription, there is no guarantee a transport session is currently in place with each associated receiver. In cases where a configured subscription has a receiver in the connecting state and the protocol configured as NETCONF, but no NETCONF transport session exists to that receiver, the publisher MUST initiate a transport session via NETCONF call home [RFC8071], section 4.1 to that receiver. Until NETCONF connectivity is established and a subscription-started state change notification is successfully sent, that receiver MUST remain in a status of either "connecting" or "timeout".
If the call home fails because the publisher receives receiver credentials which are subsequently declined per [RFC8071], Section 4.1, step S5 authentication, then that receiver MUST be assigned a "timeout" status.
If the call home fails to establish for any other reason, the publisher MUST NOT progress the receiver to the "active" state. Additionally, the publisher SHOULD place the receiver into a "timeout" status after a predetermined number of either failed call home attempts or NETCONF sessions remotely terminated by the receiver.
NETCONF Transport session connectivity SHOULD be verified via Section 4.1, step S7.
If an active NETCONF session is disconnected but the stop-time of a subscription has not been reached, the publisher MUST restart the call home process and return the receiver to the "connecting" state.
Notification messages transported over NETCONF will be identical in format and content to those encoded using one-way operations defined within [RFC5277], section 4.
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:
Note that "error-path" does not need to be included with the "rpc-error" element, as subscription errors are generally not associated with nodes in the datastore but with the choice of RPC input parameters.
Notification messages (including state change notifications) are never sent before the NETCONF capabilities exchange has completed.
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 publisher MAY also suspend or terminate a subset of the active subscriptions on that NETCONF session.
The NETCONF Authorization Control Model [rfc6536bis] SHOULD be used to control and restrict authorization of subscription configuration.
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.
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].
The following example illustrates the retrieval of the list of available event streams using the "get" operation.
<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.
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 identifier of 22, the second, an identifier of 23.
+------------+ +-----------+
| Subscriber | | Publisher |
+------------+ +-----------+
| |
| Capability Exchange |
|<---------------------------->|
| |
| |
| establish-subscription |
|----------------------------->| (a)
| RPC Reply: OK, id = 22 |
|<-----------------------------| (b)
| |
| notification message (for 22)|
|<-----------------------------|
| |
| |
| establish-subscription |
|----------------------------->|
| 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 netconf: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>
<name>NETCONF</name>
<xpath-filter xmlns:ex="http://example.com/events">
/ex:foo
</xpath-filter>
</stream>
<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 identifier of the accepted subscription within message (b):
<rpc-reply message-id="102"
xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
<identifier
xmlns="urn:ietf:params:xml:ns:yang:ietf-subscribed-notifications">
22
</identifier>
</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>
dscp-unavailable
</error-app-tag>
<error-info>
<establish-subscription-error-datastore
xmlns="urn:ietf:params:xml:ns:yang:ietf-subscribed-notifications">
<dscp>
100
</dscp>
</error-info>
</rpc-error>
</rpc-reply>
Figure 5: an unsuccessful establish subscription
The subscriber can use this information in future attempts to establish a subscription.
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.
<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">
<yp:datastore>
<yp:xpath-filter xmlns="http://example.com/datastore">
/interfaces-state/interface/oper-status
</yp:xpath-filter>
<yp:periodic>
<yp:period>500</yp:period>
</yp:periodic>
</yp:datastore>
<identifier>
23
</identifier>
</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>
period-unsupported
</error-message>
<error-info
xmlns="urn:ietf:params:xml:ns:yang:ietf-yang-push">
<modify-subscription-error-datastore>
<period-hint>
3000
</period-hint>
</modify-subscription-error-datastore>
</error-info>
</rpc-error>
</rpc-reply>
Figure 8: Modify subscription failure with Hint (d)
The following demonstrates deleting a subscription.
<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">
<identifier>22</identifier>
</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 identifier, but that subscription identifier 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>
no-such-subscription
</error-app-tag>
</rpc-error>
</rpc-reply>
Figure 10: Unsuccessful delete subscription
Configured subscriptions may be established, modified, and deleted using configuration operations against the top-level subtree of [I-D.draft-ietf-netconf-subscribed-notifications] or [I-D.ietf-netconf-yang-push].
In this section, we present examples of how to manage the configuration subscriptions using a NETCONF client.
For subscription creation, a NETCONF client may send:
<rpc message-id="201"
xmlns="urn:ietf:params:xml:ns:netconf:base:1.0"
xmlns:nc="urn:ietf:params:xml:ns:netconf:base:1.0">
<edit-config>
<target>
<running/>
</target>
<subscriptions
xmlns="urn:ietf:params:xml:ns:yang:ietf-subscribed-notifications">
<subscription>
<identifier>22</identifier>
<encoding>encode-xml</encoding>
<stream>
<name>NETCONF</name>
<receiver>
<address>1.2.3.4</address>
<port>1234</port>
</receiver>
</stream>
</subscription>
</subscriptions>
</edit-config>
</rpc>
Figure 11: Create a configured subscription
If the request is accepted, the publisher will indicate this. If the request is not accepted because the publisher cannot serve it, no configuration is changed. In this case the publisher may reply:
<rpc-reply message-id="201"
xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
<rpc-error>
<error-type>application</error-type>
<error-tag>resource-denied</error-tag>
<error-severity>error</error-severity>
<error-message xml:lang="en">
Temporarily the publisher cannot serve this
subscription due to the current workload.
</error-message>
</rpc-error>
</rpc-reply>
Figure 12: Response to a failed configured subscription establishment
After a subscription has been created, NETCONF connectivity to each receiver's IP address and port will be established if it does not already exist. This will be accomplished via [RFC8071].
The following figure shows the interaction model for the successful creation of a configured subscription.
+----------+ +-----------+ +---------+
|Config Ops| | Publisher | | 1.2.3.4 |
+----------+ +-----------+ +---------+
| | |
| Capability Exchange | |
|<-------------------------->| |
| | |
| | |
| Edit-config | |
|--------------------------->| |
| RPC Reply: OK | |
|<---------------------------| |
| | Call Home |
| |<-------------->|
| | |
| | subscription- |
| | started |
| |--------------->|
| | |
| | notification |
| | message |
| |--------------->|
Figure 13: Interaction model for configured subscription establishment
Configured subscriptions can be modified using configuration operations against the top-level container "/subscriptions".
For example, the subscription established in the previous section could be modified as follows, here a adding a second receiver:
<rpc message-id="202"
xmlns="urn:ietf:params:xml:ns:netconf:base:1.0"
xmlns:nc="urn:ietf:params:xml:ns:netconf:base:1.0">
<edit-config>
<target>
<running/>
</target>
<subscriptions
xmlns="urn:ietf:params:xml:ns:yang:ietf-subscribed-notifications">
<subscription>
<identifier>
1922
</identifier>
<receiver>
<address>
1.2.3.5
</address>
<port>
1234
</port>
</receiver>
</subscription>
</subscriptions>
</edit-config>
</rpc>
Figure 14: Modify configured subscription
If the request is accepted, the publisher will indicate success. The result is that the interaction model described in Figure 13 may be extended as follows.
+----------+ +-----------+ +---------+ +---------+
|Config Ops| | Publisher | | 1.2.3.4 | | 1.2.3.5 |
+----------+ +-----------+ +---------+ +---------+
| | notification | |
| | message | |
| |--------------->| |
| Edit-config | | |
|--------------------------->| | |
| RPC Reply: OK | | |
|<---------------------------| | |
| | subscription- | |
| | started | |
| |---------------------------->|
| | | |
| | notification | |
| | message | |
| |--------------->| |
| |---------------------------->|
| | | |
Figure 15: Interaction model for configured subscription modification
Note in the above that in the specific example above, modifying a configured subscription actually resulted in "subscription-started" notification. And because of an existing NETCONF session, no additional call home was needed. Also note that if the edit of the configuration had impacted the filter, a separate modify-subscription would have been required for the original receiver.
Configured subscriptions can be deleted using configuration operations against the top-level container "/subscriptions". Deleting the subscription above would result in the following flow impacting all active receivers.
+----------+ +-----------+ +---------+ +---------+
|Config Ops| | Publisher | | 1.2.3.4 | | 1.2.3.5 |
+----------+ +-----------+ +---------+ +---------+
| | | |
| | notification | |
| | message | |
| |--------------->| |
| |---------------------------->|
| | | |
| Edit-config | | |
|--------------------------->| | |
| RPC Reply: OK | | |
|<---------------------------| | |
| | subscription- | |
| | terminated | |
| |--------------->| |
| |---------------------------->|
| | | |
Figure 16: Interaction model for configured subscription deletion
A publisher will send subscription state notifications according to the definitions within [I-D.draft-ietf-netconf-subscribed-notifications]).
A "subscription-started" over NETCONF 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-started
xmlns="urn:ietf:params:xml:ns:yang:ietf-subscribed-notifications"/>
<identifier>39</identifier>
<encoding>encode-xml</encoding>
<stream>
<name>NETCONF</name>
<xpath-filter xmlns:ex="http://example.com/events">
/ex:foo
</xpath-filter>
</stream>
</subscription-started>
</notification>
Figure 17: subscription-started subscription state notification
The "subscription-modified" is identical to Figure 17, with just the word "started" being replaced by "modified".
A "subscription-completed" would look like:
<notification
xmlns="urn:ietf:params:xml:ns:netconf:notification:1.0">
<eventTime>2007-09-01T10:00:00Z</eventTime>
<subscription-completed
xmlns="urn:ietf:params:xml:ns:yang:ietf-subscribed-notifications">
<identifier>39</identifier>
</subscription-completed>
</notification>
Figure 18: subscription-completed notification in XML
The "subscription-resumed" and "replay-complete" are virtually identical, with "subscription-completed" simply being replaced by "subscription-resumed" and "replay-complete" in both encodings.
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">
<identifier>39</identifier>
<error-id>
suspension-timeout
</error-id>
</subscription-terminated>
</notification>
Figure 19: subscription-terminated subscription state notification
The "subscription-suspended" is virtually identical, with "subscription-terminated" simply being replaced by "subscription-suspended".
(To be removed by RFC editor prior to publication)