| NETCONF | A. Gonzalez Prieto |
| Internet-Draft | VMware |
| Intended status: Standards Track | E. Voit |
| Expires: May 3, 2018 | Cisco Systems |
| A. Clemm | |
| Huawei | |
| E. Nilsen-Nygaard | |
| A. Tripathy | |
| Cisco Systems | |
| October 30, 2017 |
NETCONF Support for Event Notifications
draft-ietf-netconf-netconf-event-notifications-06
This document provides a NETCONF binding for [I-D.draft-ietf-netconf-subscribed-notifications]. Included are:
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This Internet-Draft will expire on May 3, 2018.
Copyright (c) 2017 IETF Trust and the persons identified as the document authors. All rights reserved.
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This document defines a binding for notification message delivery for [I-D.draft-ietf-netconf-subscribed-notifications] transported over the NETCONF protocol [RFC6241]. 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 maintain a subset/extract of an actively changing YANG datastore located on a NETCONF server.
This document is broken into two main parts. The first contains normative requirements which are incremental to [I-D.draft-ietf-netconf-subscribed-notifications] when NETCONF transport is used. The second are examples and are included as appendices.
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 this capability along with support [I-D.draft-ietf-netconf-subscribed-notifications] will 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 on a session with active subscriptions.
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 "running" 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 associated receiver(s). So where a configured subscription has a receiver in the connecting state, but no NETCONF transport exists to that receiver, the publisher MUST be able to initiate a NETCONF 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 its status of a "connecting".
If the call home fails because the publisher receives receiver credentials which are subsequently declined as part [RFC8071], Section 4.1, step S5 authentication, then that receiver MUST be assigned a "suspended" status.
If the call home fails to establish for any other reason, the publisher MAY leave the receiver in a "connecting" status, and retry the call home at a future time. Alternatively, the publisher MAY place the receiver into a "suspended" status after a predetermined number of call home attempts.
NETCONF Transport session connectivity SHOULD be verified via Section 4.1, step S7.
Failure of an active NETCONF session MUST reset the restart the call home process, and return the receiver to "connecting".
Notification messages transported over NETCONF will be identical in format and content to those encoded using one-way operations defined within [RFC5277], section 4.
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 suspect underlying NETCONF sessions. The publisher MAY also suspend or terminate a subset of the active subscriptions on the NETCONF session.
The NETCONF Authorization Control Model [RFC6536] 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, Kent Watsen, and Guangying Zheng.
| [I.D.draft-ietf-netconf-notification-messages] | Voit, Eric., Clemm, Alexander., Bierman, A. and T. Jenkins, "YANG Notification Headers and Bundles", September 2017. |
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]. Any reply will include the stream identities supported on the NETCONF publisher which may be available to that client.
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. In the example reply below, the list contains just the NETCONF stream.
<rpc-reply message-id="101"
xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
<data>
<streams
xmlns="urn:ietf:params:xml:ns:yang:ietf-subscribed-notifications">
<name>NETCONF</name>
</streams>
</data>
</rpc-reply>
Figure 2: Get streams response
The dynamic subscription RPCs and interactions operation are defined in [I-D.draft-ietf-netconf-subscribed-notifications] and enhanced in [I-D.ietf-netconf-yang-push].
An example of establish-subscription interactions over NETCONF transport for a sample subscription is described 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>
</establish-subscription>
</rpc>
Figure 3: establish-subscription over NETCONF
If the NETCONF publisher can satisfy the request, the publisher sends a positive "subscription-result" element, and the subscription-id of the accepted subscription.
<rpc-reply message-id="102"
xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
<subscription-result
xmlns="urn:ietf:params:xml:ns:yang:ietf-subscribed-notifications">
ok
</subscription-result>
<identifier
xmlns="urn:ietf:params:xml:ns:yang:ietf-subscribed-notifications">
22
</identifier>
</rpc-reply>
Figure 4: Successful establish-subscription
If the NETCONF publisher cannot satisfy the request, or subscriber has no authorization to establish the subscription, the publisher will send a negative "subscription-result" element. For instance:
<rpc-reply message-id="101"
xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
<subscription-result
xmlns="urn:ietf:params:xml:ns:yang:ietf-subscribed-notifications">
stream-unavailable
</subscription-result>
</rpc-reply>
Figure 5: Unsuccessful establish subscription
To get an idea of the interaction model, the following figure shows two separate establish subscriptions RPC being made. The first is given subscription id 22, the second, id 23.
+------------+ +-----------+
| Subscriber | | Publisher |
+------------+ +-----------+
| |
| Capability Exchange |
|<---------------------------->|
| |
| |
| Establish Subscription |
|----------------------------->|
| RPC Reply: OK, id = 22 |
|<-----------------------------|
| |
| notification message (for 22)|
|<-----------------------------|
| |
| |
| Establish Subscription |
|----------------------------->|
| RPC Reply: OK, id = 23 |
|<-----------------------------|
| |
| |
| notification message (for 22)|
|<-----------------------------|
| notification message (for 23)|
|<-----------------------------|
| |
Figure 6: Multiple subscription establishments over a single NETCONF session
In the example above, it is important to note that the subscription ids of 22 and 23 are not included in the notification messages of [I-D.draft-ietf-netconf-subscribed-notifications]. However because [I-D.ietf-netconf-yang-push] has defined its own notifications, subscription identifiers are available within those notification messages. With the availability of [I.D.draft-ietf-netconf-notification-messages], all notification messages will be able to transport a subscription identifier.
The following demonstrates modifying a dynamic subscription. Consider a subscription from [I-D.ietf-netconf-yang-push]. An established may have a new filter applied. The desired modification is the application of a new filter.
<rpc message-id="102"
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:datastore>
<identifier>
22
</identifier>
</modify-subscription>
</rpc>
Figure 7: Subscription modification
If the NETCONF publisher can satisfy the request, the publisher sends a positive "subscription-result". This response is like that to an establish-subscription request, but without the subscription identifier.
<rpc-reply message-id="102"
xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
<subscription-result
xmlns="urn:ietf:params:xml:ns:yang:ietf-subscribed-notifications">
ok
</subscription-result>
</rpc-reply>
Figure 8: Successful modify-subscription
If the NETCONF publisher cannot satisfy the request, the publisher sends a negative "subscription-result" element. Its contents and semantics match those from an establish-subscription request.
To get an idea of the interaction model, the following figure shows a successful RPC modification request to subscription with an identifier of 22.
+------------+ +-----------+
| Subscriber | | Publisher |
+------------+ +-----------+
| |
| notification message |
|<-----------------------------|
| |
| Modify Subscription |
|----------------------------->|
| RPC Reply: OK |
|<-----------------------------|
| |
| notification message |
|<-----------------------------|
| |
Figure 9: Interaction model for successful subscription modification
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 10: Delete subscription
If the NETCONF publisher can satisfy the request, the publisher sends an OK element. For example:
<rpc-reply message-id="103"
xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
<ok/>
</rpc-reply>
Figure 11: Successful delete subscription
If the NETCONF publisher cannot satisfy the request, the publisher sends an error-rpc element indicating the modification didn't work. One way this could happen is if an existing valid subscription identifier was given, but that subscription 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-path
xmlns:sn="urn:ietf:params:xml:ns:yang:ietf-subscribed-notifications">
sn:identifier
</error-path>
<error-message xml:lang="en">
no-such-subscription
</error-message>
</rpc-error>
</rpc-reply>
Figure 12: 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. Key differences from dynamic subscriptions over NETCONF is that subscription lifetimes are decoupled from NETCONF sessions.
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>
<subscription-config
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>
</subscription-config>
</edit-config>
</rpc>
Figure 13: Create a configured subscription
If the request is accepted, the publisher would reply:
<rpc-reply message-id="201"
xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
<ok/>
</rpc-reply>
Figure 14: Response to a successful configuration subscription establishment
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 15: 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].
To get an idea of the interaction model, the following figure shows a successful configuration based creation of a subscription.
+----------+ +-----------+ +---------+
|Config Ops| | Publisher | | 1.2.3.4 |
+----------+ +-----------+ +---------+
| | |
| Capability Exchange | |
|<-------------------------->| |
| | |
| | |
| Edit-config | |
|--------------------------->| |
| RPC Reply: OK | |
|<---------------------------| |
| | Call Home |
| |<-------------->|
| | |
| | Subscription |
| | Started |
| |--------------->|
| | |
| | notification |
| | message |
| |--------------->|
Figure 16: Interaction model for configured subscription establishment
Configured subscriptions can be modified using configuration operations against the top-level subtree subscription-config.
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>
<subscription-config
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>
</subscription-config>
</edit-config>
</rpc>
Figure 17: Modify configured subscription
If the request is accepted, the publisher would reply:
<rpc-reply message-id="202"
xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
<ok/>
</rpc-reply>
Figure 18: A successful configured subscription modification
And the previous interaction model would be extended as follows.
+----------+ +-----------+ +---------+ +---------+
|Config Ops| | Publisher | | 1.2.3.4 | | 1.2.3.5 |
+----------+ +-----------+ +---------+ +---------+
| | | |
| | | |
| | notification | |
| | message | |
| |--------------->| |
| | | |
| Edit-config | | |
|--------------------------->| | |
| RPC Reply: OK | | |
|<---------------------------| | |
| | Call Home | |
| |<--------------------------->|
| | Subscription | |
| | Started | |
| |---------------------------->|
| | | |
| | notification | |
| | message | |
| |--------------->| |
| |---------------------------->|
| | | |
Figure 19: 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. If the edit of the configuration had also added a filter, a separate modify-subscription would have gone to the original receiver.
Configured subscriptions can be deleted using configuration operations against the top-level subtree subscription-config. Deleting the subscription above would result in the following flow impacting all receivers.
+----------+ +-----------+ +---------+ +---------+
|Config Ops| | Publisher | | 1.2.3.4 | | 1.2.3.5 |
+----------+ +-----------+ +---------+ +---------+
| | | |
| | notification | |
| | message | |
| |--------------->| |
| |---------------------------->|
| | | |
| Edit-config | | |
|--------------------------->| | |
| RPC Reply: OK | | |
|<---------------------------| | |
| | Subscription | |
| | Terminated | |
| |--------------->| |
| |---------------------------->|
| | | |
Figure 20: 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 21: subscription-started subscription state notification
The subscription-modified is identical, 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 22: 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>
unsupportable-volume
</error-id>
</subscription-terminated>
</notification>
Figure 23: 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)