]> Huawei

101 Software Avenue, Yuhua District Nanjing Jiangsu 210012 China bill.wu@huawei.com

Huawei

101 Software Avenue, Yuhua District Nanjing Jiangsu 210012 China songwei80@huawei.com

China Mobile

32 Xuanwumen West St, Xicheng District Beijing 10053 liupengyjy@chinamobile.com

Huawei

101 Software Avenue, Yuhua District Nanjing Jiangsu 210012 China maqiufang1@huawei.com

China Telecom

32 Xuanwumen West St, Xicheng District Beijing 102209 wangw36@chinatelecom.cn

Microsoft

Zhixiong.Niu@microsoft.com

OPS Area NETCONF Working Group This document defines a YANG data model and associated mechanism that enable adaptive subscription to a publisher's event streams. The periodic update interval for the event streams can be set adaptively. Applying these elements allows servers to automatically adjust the rate and volume of telemetry traffic sent from a publisher to receivers.

YANG-Push subscriptions allow subscriber applications to request a continuous customized stream of updates from a YANG datastore without needing to poll. It defines a mechanism (i.e., update trigger) to determine when an update record needs to be generated. Two types of subscription are introduced in , distinguished by how updates are triggered: periodic and on-change. Periodic subscription allows subscribed data to be streamed to the destination at a configured fixed periodic interval; On-change subscription allows update to be triggered whenever a change in the subscribed information is detected. However, in some large-scale deployments (e.g., massive data collection for wireless network performance monitoring) where an increased data collection rate is used, it becomes more likely that both clients and servers could be temporarily overwhelmed with a burst of streamed data, and that network resources (e.g., bandwidth resource, radio resource) and computation resource could be excessively consumed. Therefore, it may be hard to continuously monitor operational data, especially values that fall outside normal operational ranges. Conversely, if the rate at which we collect a stream of data is set too low or chosen so that low priority telemetry data are dropped, these telemetry data will not be sufficient to detect and diagnose problems and to verify correct network behavior. A client might choose to monitor the operational state and send a request to modify the data collection rate on the server. But how often the client evaluates if the modification of the data collection rate is required highly depends on the current collection rate: collecting a stream of data at a low rate prevents the subscriber from capturing sufficient data for timely decision-making, which may result in service discontinuity. In addition, when tens of thousands of network devices need to be managed, frequent follow-up modification requests are prone to errors. There is a need for a service to balance between data management cost and real-time streaming telemetry. To achieve this, servers can be configured with multiple different period intervals and corresponding subscription update policies which allow servers/publishers to automatically switch to different period intervals according to the network condition changes without the interaction with the client for policy update instructions. E.g., when the wireless signal strength falls below a configured threshold, the subscribed data can be streamed at a higher rate to capture potentially important data and events (e.g., continuous service degeneration); while when the wireless signal strength crosses a configured threshold, the subscribed data can be streamed at a lower rate. This document defines a YANG data model and associated mechanism that enable adaptive subscription to a publisher's event streams. The periodic update interval for the event streams can be set adaptively. Applying these elements allows servers to automatically adjust the rate and volume of telemetry traffic sent from a publisher to receivers.

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 when, and only when, they appear in all capitals, as shown here. The following terms are defined in , , , , , and are not redefined here: Event Client Configuration Configured subscription Configuration datastore Notification message Publisher Receiver Subscriber Subscription On-change subscription Periodic subscription Selection filter This document defines the following term: Apply subscription update policy on the servers and allow servers/publishers to automatically switch to different period intervals according to network condition changes without interacting with the client for update policy instructions.

This document defines a YANG module "ietf-adapt-subscription", which augments the "update-trigger" choice defined in the "ietf-yang-push" module with subscription configuration parameters that are specific to a subscriber's adaptive subscription. In addition to subscription state notifications defined in and notifications for subscribed content defined in , "ietf-adapt-subscription" YANG module also defines "adaptive-period-update" notification to report the update interval change. The following tree diagrams provide an overview of the data model for "ietf-adapt-subscription" module.

module: ietf-adapt-subscription augment /sn:subscriptions/sn:subscription/yp:update-trigger: +--:(adaptive-periodic) +--rw adaptive-periods +--rw adaptive-period* [name] +--rw name yang:yang-identifier +--rw xpath-external-eval yang:xpath1.0 +--rw period yp:centiseconds +--rw anchor-time? yang:date-and-time augment /sn:establish-subscription/sn:input/yp:update-trigger: +--:(adaptive-periodic) +-- adaptive-periods +-- adaptive-period* [name] +-- name yang:yang-identifier +-- xpath-external-eval yang:xpath1.0 +-- period yp:centiseconds +-- anchor-time? yang:date-and-time augment /sn:modify-subscription/sn:input/yp:update-trigger: +--:(adaptive-periodic) +-- adaptive-periods +-- adaptive-period* [name] +-- name yang:yang-identifier +-- xpath-external-eval yang:xpath1.0 +-- period yp:centiseconds +-- anchor-time? yang:date-and-time augment /sn:subscription-started/yp:update-trigger: +--:(adaptive-periodic) +-- adaptive-periods +-- adaptive-period* [name] +-- name yang:yang-identifier +-- xpath-external-eval yang:xpath1.0 +-- period yp:centiseconds +-- anchor-time? yang:date-and-time augment /sn:subscription-modified/yp:update-trigger: +--:(adaptive-periodic) +-- adaptive-periods +-- adaptive-period* [name] +-- name yang:yang-identifier +-- xpath-external-eval yang:xpath1.0 +-- period yp:centiseconds +-- anchor-time? yang:date-and-time notifications: +---n adaptive-period-update +--ro id? sn:subscription-id +--ro period yp:centiseconds +--ro period-update-time? yang:date-and-time +--ro datastore identityref +--ro (selection-filter)? +--:(by-reference) | +--ro selection-filter-ref selection-filter-ref +--:(within-subscription) +--ro (filter-spec)? +--:(datastore-subtree-filter) | +--ro datastore-subtree-filter? <anydata> {sn:subtree}? +--:(datastore-xpath-filter) +--ro datastore-xpath-filter? yang:xpath1.0 {sn:xpath}?

For adaptive subscriptions, triggered updates will occur at the boundaries of specified time intervals when a trigger condition is satisfied. These boundaries can be calculated from the following adaptive periodic parameters: a "name" represents the name of each adaptive period; a "period" defines the duration between push updates, in units of 0.01 seconds. The "period" has the same definition as the yp:period for periodic subscription defined in , while it must be co-exist with an "xpath-external-eval" parameter and can be switched based on trigger conditions indicated by the "xpath-external-eval" parameter; an "anchor-time"; update intervals fall on the points in time that are a multiple of a "period" from an "anchor-time". If an "anchor-time" is not provided, then the "anchor-time" MUST be set with the creation time of the initial update record. an "xpath-external-eval" represents a standard XPath evaluation expression (See section 6.4 of ) that is applied against the targeted data object, which is used to trigger/control the update interval switching within the server. It follows the rules defined in section 3.4 of and contains comparisons of the targeted datastore node with its value to the specific threshold in the XPath format. Different from selection filter defined in , it is applied against a single targeted object rather than a set of target objects. it monitors a specific data object change and evaluates the trigger condition associated with the targeted object to be true or false using XPATH rules and does not influence the event records output generation from a publisher. It is not always trivial for a subscriber to determine the threshold used in an XPath expression criterion. Sometimes the threshold needs to be adjusted during the lifecycle of an adaptive subscription, depending on historical fluctuation range and how fast the targeted data object changes, distribution characteristics of the targeted data object or even the generated volume of telemetry traffic.How often the XPath expression criterion is evaluated to decide whether to switch to another period interval is up to the publisher's implementation. With minimal delay, the expression can be evaluated whenever changes to targeted data object occur, or at the end of each shortest streaming update period. To reduce the frequency of evaluation, the server can choose to check targeted object change at every multiple (e.g.,2 or 3) high-frequency streaming update periods.The represented expression defined in "xpath-external-eval" is evaluated in the following XPath context: The set of namespace declarations is the set of prefix and namespace pairs for all YANG modules implemented by the server, where the prefix is the YANG module name and the namespace is as defined by the "namespace" statement in the YANG module. If the leaf is encoded in XML, all namespace declarations in scope on the "xpath-external-eval" leaf element are added to the set of namespace declarations. If a prefix found in the XML is already present in the set of namespace declarations, the namespace in the XML is used. The set of variable bindings is empty. The function library is the core function library defined in and the function defined in Section 10 in RFC 7950. The context node is the root node. For the cases where the "xpath-external-eval" parameter refers to multiple list instances, XPath abbreviated syntax can be used to identify a particular instance, e.g., to represent a comparison for a leaf in a list entry:

/if:interfaces/if:interface[if:name="eth0"]/if:in-errors>1000.

The server MUST convert the XPath expression defined in "xpath-external-eval" to a boolean value and internally apply the "boolean" function defined in Section 4.3 in [XPATH1.0] if the evaluated result is not a boolean value. Only if the Xpath expression is evaluated as "true", does the publisher switch to the corresponding period with which push updates are reported. Note that the adaptive subscription need not be supported by every YANG datastore node. A publisher MAY decide to simply reject an adaptive subscription with "adaptive-unsupported" (defined in ) if the scope of the subscription contains selected data nodes for which adaptive subscription is not supported.

The augmentation of YANG module "ietf-yang-push" made to RPCs specified in YANG module "ietf-subscribed-notifications" is introduced. This augmentation concerns the "establish-subscription" RPC, which is augmented with parameters that are needed to specify a subscriber's adaptive subscriptions. These parameters are the same as the ones defined in .

As specified in and , RPC error responses from the publisher are used to indicate a rejection of an RPC for any reason. This document introduces three new RPC errors for "establish-subscription" RPC.

establish-subscription ----------------------------- adaptive-unsupported xpath-evaluation-unsupported multi-xpath-criteria-conflict

adaptive-unsupported is used to indicate that the adaptive subscription is not supported for any objects that are selectable by the filter. xpath-evaluation-unsupported is used to indicate that a server failed to parse syntax defined in "xpath-external-eval". The failure can be caused by either a syntax error or some XPath 1.0 syntax not supported against the specific object. multi-xpath-criteria-conflict is used to indicate that the multiple Xpath evaluation criteria represented by "xpath-external-eval" are evaluated as conflicting, i.e., more than one condition expressions are evaluated to "true". However, the publisher should still push updates at the shortest streaming period among multiple corresponding period intervals if multiple Xpath evaluations conflict with each other during the lifecycle of an adaptive subscription. For an example of how the above RPC errors can be returned, see the "xpath-evaluation-unsupported" error response illustrated in . Note that existing RPC errors defined in RFC 8639 and RFC 8641 are still supported by this document. For example, if any configured period for adaptive subscription is not supported by the publisher, a "period-unsupported" error response could be used.

The adaptive update notification is similar to subscription state change notifications defined in . It is inserted into the sequence of notification messages sent to a particular receiver. As stated in RFC 8639, section 2.7, the adaptive update notification cannot be dropped or filtered out, it cannot be stored in replay buffers, and it is delivered only to impacted receivers of a subscription. The identification of the adaptive update notification is easy to separate from other notification messages through the use of the YANG extension "subscription-state-notif". This extension tags a notification as a subscription state change notification. The objects in the 'adaptive-period-update' notification include: a "period" that defines the duration between push updates, the period can be changed based on trigger conditions. a "period-update-time" that designates a timestamp when the server starts to switch to another period interval because the evaluated "xpath-external-eval" expression result changed. A selection filter to identify YANG nodes of interest in a datastore. Filter contents are specified via a reference to an existing filter or via an in-line definition for only that subscription based on XPath Evaluation criteria defined in section 6.4 of . Referenced filters allow an implementation to avoid evaluating filter acceptability during a dynamic subscription request. The "case" statement differentiates the options. Note that filter contents are not affected by the "xpath-external-eval" parameter defined by the update trigger.

YANG-Push subscriptions specify selection filters to identify targeted YANG datastore nodes and/or datastore subtrees for which updates are to be pushed. In addition, it specifies update policies which contain conditions that trigger generation and pushing of new update records. To support a subscriber's adaptive subscription defined in this document, the trigger condition can also use similar selection filters to express a standard XPath Evaluation criterion (section 6.4 of ) against targeted data objects. Similar to on-change subscriptions, adaptive subscriptions are particularly effective for data that changes infrequently, the following complex design choices need to be cautious, although these designs have already been well supported by the section 3.4 of : Support XPath Evaluation criteria against every data object; Support more than one target object selection and operation (e.g., addition, subtraction, division and multiplication) in the XPath evaluation criterion; Support any type of data object in node set in the XPath evaluation criterion, e.g., string, int64, uint64, and decimal64 types; Both objects in the XPath Evaluation criterion to be compared are node-sets; Two objects to be compared are in different data types, e.g., one is an integer, the other is a string As described in section 6.4 of , Numbers in XPath 1.0 are IEEE 754 double-precision floating-point values; some values of int64, uint64, and decimal64 types cannot be exactly represented in XPath expressions. If two objects to be compared are in different data types, a conversion function is needed to convert different data types into numbers. If both objects in XPath Evaluation criteria to be compared are node-sets, more computation resources are required which add complexity. To reduce these complexities, the following design principles are recommended: XPath Evaluation criteria against a minimal set of data objects in the data model, the minimal set of data objects can be advertised using Notification capabilities model defined in . XPath Evaluation criteria only support condition expressions that filter updates based on numbers. One object to be compared in the XPath Evaluation criteria is a leaf/leaf-list data node and the other object is a number data type. If a server receives an XPath Evaluation criterion with some XPath syntax unsupported against the specific object, an RPC error with "xpath-evaluation-unsupported" MUST be returned.

This YANG module makes imports from , and .

<CODE BEGINS> file "ietf-adapt-subscription@2023-05-30.yang" module ietf-adapt-subscription { yang-version 1.1; namespace "urn:ietf:params:xml:ns:yang:ietf-adapt-subscription"; prefix as; import ietf-subscribed-notifications { prefix sn; reference "RFC 8639: Subscription to YANG Notifications"; } import ietf-yang-push { prefix yp; reference "RFC 8641: Subscription to YANG Notifications for Datastore Updates"; } import ietf-yang-types { prefix yang; reference "RFC YYYY: Common YANG Data Types"; } organization "IETF NETCONF (Network Configuration) Working Group"; contact "WG Web: <http://tools.ietf.org/wg/netconf> WG List: <netconf@ietf.org> Editor: Qin Wu <mailto:bill.wu@huawei.com> Editor: Wei Song <mailto: songwei80@huawei.com> Editor: Peng Liu <mailto: liupengyjy@chinamobile.com> Editor: Qiufang Ma <mailto: maqiufang1@huawei.com> Editor: Wei Wang <mailto: wangw36@chinatelecom.cn> Editor: Zhixiong Niu <mailto: Zhixiong.Niu@microsoft.com>"; description "This module extends the YANG data module defined in YANG-push to enable the subscriber's adaptive subscriptions to a publisher's event streams with various different period intervals to report updates. Copyright (c) 2023 IETF Trust and the persons identified as authors of the code. All rights reserved. Redistribution and use in source and binary forms, with or without modification, is permitted pursuant to, and subject to the license terms contained in, the Revised BSD License set forth in Section 4.c of the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info). This version of this YANG module is part of RFC xxxx (https://www.rfc-editor.org/info/rfcxxxx); see the RFC itself for full legal notices. 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 (RFC 2119) (RFC 8174) when, and only when, they appear in all capitals, as shown here."; revision 2023-05-30 { description "Initial revision"; reference "RFC xxxx: Adaptive Subscription to YANG Notification."; } identity adaptive-unsupported { base sn:establish-subscription-error; description "Adaptive-subscription is not supported for any objects that are selectable by the filter."; } identity xpath-evaluation-unsupported { base sn:establish-subscription-error; description "Unable to parse the xpath evaluation criteria defined in 'xpath-external-eval' because of a syntax error or some XPath 1.0 syntax not supported against the specific object."; } identity multi-xpath-criteria-conflict { base sn:establish-subscription-error; base sn:subscription-terminated-reason; description "Multiple Xpath evaluation criteria represented by 'xpath-external-eval' are evaluated as a conflict. I.e., more than one condition expression is evaluated to 'true'."; } grouping adaptive-subscription-modifiable { description "This grouping describes the datastore-specific adaptive subscription conditions that can be changed during the lifetime of the subscription."; container adaptive-periods { list adaptive-period { key "name"; description "An entry in this list represents an adaptive period which defines a push update interval and trigger conditions to switch to the update interval for sending an event record to the subscriber."; leaf name { type yang:yang-identifier; description "The name of adaptive period."; } leaf xpath-external-eval { type yang:xpath1.0; mandatory true; description "An XPath string, representing a logical expression, which can contain comparisons of datastore values and logical operations in the XPath format."; } leaf period { type yp:centiseconds; mandatory true; description "Duration of time that should occur between periodic push updates, in units of 0.01 seconds."; } leaf anchor-time { type yang:date-and-time; description "Designates a timestamp before or after which a series of periodic push updates is determined. The next update will take place at a point in time that is a multiple of a period from the 'anchor-time'. For example, for an 'anchor-time' that is set for the top of a particular minute and a period interval of a minute, updates will be sent at the top of every minute that this subscription is active."; } } description "Container for adaptively periodic subscription."; } } augment "/sn:subscriptions/sn:subscription/yp:update-trigger" { description "This augmentation adds additional subscription parameters that apply specifically to adaptive subscription."; case adaptive-periodic { description "Defines adaptively periodic case for sending an event record to the subscriber."; uses adaptive-subscription-modifiable; } } augment "/sn:establish-subscription/sn:input/yp:update-trigger" { description "This augmentation adds additional establish-subscription parameters that apply specifically to datastore updates to RPC input."; case adaptive-periodic { description "Defines adaptively periodic case for sending an event record to the subscriber."; uses adaptive-subscription-modifiable; } } augment "/sn:modify-subscription/sn:input/yp:update-trigger" { description "This augmentation adds additional modify-subscription parameters that apply specifically to datastore updates to RPC input."; case adaptive-periodic { description "Defines adaptively periodic case for sending an event record to the subscriber."; uses adaptive-subscription-modifiable; } } augment "/sn:subscription-started/yp:update-trigger" { description "This augmentation adds additional adaptive subscription parameters to the notification that a subscription has started."; case adaptive-periodic { description "Defines adaptively periodic case for sending an event record to the subscriber."; uses adaptive-subscription-modifiable; } } augment "/sn:subscription-modified/yp:update-trigger" { description "This augmentation adds additional adaptive subscription parameters to the notification that a subscription has been modified."; case adaptive-periodic { description "Defines adaptively periodic case for sending an event record to the subscriber."; uses adaptive-subscription-modifiable; } } notification adaptive-period-update { sn:subscription-state-notification; description "This notification contains a push update that in turn contains data subscribed to via a subscription. In the case of a periodic subscription, this notification is sent for periodic updates. It can also be used for synchronization updates of an on-change subscription. This notification shall only be sent to receivers of a subscription. It does not constitute a general-purpose notification that would be subscribable as part of the NETCONF event stream by any receiver."; leaf id { type sn:subscription-id; description "This references the subscription that drove the notification to be sent."; } leaf period { type yp:centiseconds; mandatory true; description "New duration of time that should occur between periodic push updates, in units of 0.01 seconds."; } leaf period-update-time { type yang:date-and-time; description "Designates a timestamp when the server starts to switch to another period interval because the evaluated 'xpath- external-eval' expression result changed."; } uses yp:datastore-criteria { refine "selection-filter/within-subscription" { description "Specifies the selection filter and where it originated from. If the 'selection-filter-ref' is populated, the filter in the subscription came from the 'filters' container. Otherwise, it is populated in-line as part of the subscription itself."; } } } } <CODE ENDS>

This document registers one URI in the IETF XML registry . Following the format in , the following registration is requested to be made:

--------------------------------------------------------------------- URI: urn:ietf:params:xml:ns:yang:ietf-adapt-subscription Registrant Contact: The IESG. XML: N/A, the requested URI is an XML namespace. ---------------------------------------------------------------------

This document registers one YANG module in the YANG Module Names registry . Following the format in , the following registration is requested to be made:

--------------------------------------------------------------------- Name: ietf-adapt-subscription Namespace: urn:ietf:params:xml:ns:yang:ietf-adapt-subscription Prefix: as Reference: RFC xxxx ---------------------------------------------------------------------

The YANG module specified in this document defines a schema for data that is designed to be accessed via network management protocols such as NETCONF or RESTCONF . The lowest NETCONF layer is the secure transport layer, and the mandatory-to-implement secure transport is Secure Shell (SSH) . The lowest RESTCONF layer is HTTPS, and the mandatory-to-implement secure transport is TLS . The NETCONF Configuration Access Control Model (NACM) provides the means to restrict access for particular NETCONF or RESTCONF users to a preconfigured subset of all available NETCONF or RESTCONF protocol operations and content. There are a number of data nodes defined in this YANG module that are writable/creatable/deletable (i.e., config true, which is the default). These data nodes may be considered sensitive in some network environments. Write operations (e.g., edit-config) to these data nodes without proper protection can have a negative effect on network operations. These are the subtrees and data nodes and their sensitivity/vulnerability: /sn:subscriptions/sn:subscription/yp:update-trigger/as:adaptive-periods/as:adaptive-period/as:period /sn:subscriptions/sn:subscription/yp:update-trigger/as:adaptive-periods/as:adaptive-period/as:anchor-time /sn:establish-subscription/sn:input/yp:update-trigger/as:adaptive-periods/as:adaptive-period/as:period /sn:establish-subscription/sn:input/yp:update-trigger/as:adaptive-periods/as:adaptive-period/as:anchor-time

Thanks Michael Wang, Liang Geng for their major contributions to the initial modeling and use cases.

Michael Wang Email: wangzitao@huawei.com Liang Geng China Mobile 32 Xuanwumen West St, Xicheng District Beijing 10053 Email: gengliang@chinamobile.com

We would like to thank Rob Wilton, Thomas Graf, Andy Bierman, Michael Richardson, Henk Birkholz, Chong Feng, Adrian Farrel for valuable review on this document, special thanks to Thomas and Michael for organizing the discussion on several relevant drafts and reach the common understanding on the concept and ideas. Thanks Michael for providing CHIP/Matter WIFI statistics reference.

IEEE CSA W3C

This section presents an example YANG module so that can give examples of how the YANG module defined in is used to perform adaptive subscription. The example YANG module used in this section represents a Wi-Fi Network Diagnostics data specified in which can be used by a Node to assist a user or Administrative Node in diagnosing potential problems. YANG tree diagram for the "example-wifi-network-diagnostic" module:

module: example-wifi-network-diagnostic +--ro server | +--ro bssid? yang:mac-address | +--ro security-type? enumeration | +--ro wifi-version? enumeration | +--ro channel-num? int8 | +--ro rssi? int8 | +--ro beacon-lost-count? int8 | +--ro beacon-rx-count? int8 | +--ro packet-multicast-rx-count? int8 | +--ro packet-multicast-tx-count? int8 | +--ro packet-unicast-rx-count? int8 | +--ro packet-unicast-tx-count? int8 | +--ro current-max-rate? int8 | +--ro overrun-count? int8 +--ro events +--ro event* [name] +--ro name string +--ro disconnection? enumeration +--ro association-failure? enumeration +--ro connection-status? enumeration

module example-wifi-network-diagnostic { yang-version 1; namespace "http://example.com/yang/wifi-network-diagnostic"; prefix wnd; import ietf-yang-types { prefix yang; } container server { config false; description "Configuration of the WiFi Server logical entity."; leaf bssid { type yang:mac-address; description "The MAC address of a wireless access point."; } leaf security-type { type enumeration { enum unspecified { value 0; } enum none { value 1; } enum wep { value 2; } enum wpa { value 3; } enum wpa2 { value 4; } enum wpa3 { value 5; } } description "The type of Wi-Fi security used. A value of 0 indicate that the interface is not currently configured or operational."; } leaf wifi-version { type enumeration { enum 80211a { value 0; } enum 80211b { value 1; } enum 80211g { value 2; } enum 80211n { value 3; } enum 80211ac { value 4; } enum 80211ax { value 5; } } description "The highest 802.11 standard version usable by the Node."; } leaf channel-num { type int8; description "The channel that Wi-Fi communication is currently operating on. A value of 0indicates that the interface is not currently configured or operational."; } leaf rssi { type int8; description "The RSSI of the Node's Wi-Fi radio in dBm."; } leaf beacon-lost-count { type int8; description "The count of the number of missed beacons the Node has detected."; } leaf beacon-rx-count { type int8; description "The count of the number of received beacons. The total number of expected beacons that could have been received during the interval since association SHOULD match the sum of BeaconRxCount and BeaconLostCount. "; } leaf packet-multicast-rx-count { type int8; description "The number of multicast packets received by the Node."; } leaf packet-multicast-tx-count { type int8; description "The number of multicast packets transmitted by the Node."; } leaf packet-unicast-rx-count { type int8; description "The number of multicast packets received by the Node."; } leaf packet-unicast-tx-count { type int8; description "The number of multicast packets transmitted by the Node."; } leaf current-max-rate { type int8; description "The current maximum PHY rate of transfer of data in bytes-per-second."; } leaf overrun-count { type int8; description "The number of packets dropped either at ingress or egress, due to lack of buffer memory to retain all packets on the ethernet network interface. The OverrunCount attribute SHALL be reset to 0 upon a reboot of the Node.."; } } container events { config false; description "Configuration of WIFI Network Diagnostic events."; list event { key "name"; description "The list of event sources configured on the server."; leaf name { type string; description "The unique name of an event source."; } leaf disconnection { type enumeration { enum de-authenticated { value 1; } enum dis-association { value 2; } } description "A Node's Wi-Fi connection has been disconnected as a result of de-authenticated or dis-association and indicates the reason."; } leaf association-failure { type enumeration { enum unknown { value 0; } enum association-failed { value 1; } enum authentication-failed { value 2; } enum ssid-not-found { value 3; } } description "A Node has attempted to connect, or reconnect, to a Wi-Fi access point, but is unable to successfully associate or authenticate, after exhausting all internal retries of its supplicant."; } leaf connection-status { type enumeration { enum connected { value 1; } enum notconnected { value 2; } } description "A Node's connection status to a Wi-Fi network has changed. Connected, in this context, SHALL mean that a Node acting as a Wi-Fi station is successfully associated to a Wi-Fi Access Point."; } } } }

The examples within this document use the normative YANG module "ietf-adapt-subscription" defined in and the non-normative example YANG module "example-wifi-network-diagnostic" defined in Appendix A.1. This section shows some typical adaptive subscription and notification message exchanges.

The client configures adaptive subscription policy parameters on the server. The adaptive subscription configuration parameters require the server to support two update intervals (i.e., 5 seconds, 60 seconds) and report updates every 60 seconds if the rssi value is greater than or equal to -65dB; If the rssi value is less than -65dB, switch to 5 seconds period value to report updates.

<rpc message-id="101" xmlns="urn:ietf:params:xml:ns:netconf:base:1.0"> <edit-config> <target> <running/> </target> <config> <subscriptions xmlns="urn:ietf:params:xml:ns:yang:ietf-subscribed-notifications" xmlns:yp="urn:ietf:params:xml:ns:yang:ietf-yang-push"> <subscription> <id>1011</id> <yp:datastore xmlns:ds="urn:ietf:params:xml:ns:yang:ietf-datastores"> ds:operational </yp:datastore> <yp:datastore-xpath-filter xmlns:wnd="http://example.com/yang/wifi-network-diagnostic"> /wnd:server </yp:datastore-xpath-filter> <as:adaptive-periods xmlns:as="urn:ietf:params:xml:ns:yang:ietf-adapt-subscription"> <as:adaptive-period> <as:name>adaptive-period-1</as:name> <as:xpath-external-eval> /wnd:server/wnd:rssi&lt;-65 </as:xpath-external-eval> <as:period>5</as:period> </as:adaptive-period> <as:adaptive-period> <as:name>adaptive-period-2</as:name> <as:xpath-external-eval> /wnd:server/wnd:rssi&gt;=-65 </as:xpath-external-eval> <as:period>60</as:period> </as:adaptive-period> </as:adaptive-periods> <receivers> <receiver> <name>host.example.com</name> </receiver> </receivers> </subscription> </subscriptions> </config> </edit-config> </rpc>

The subscriber sends an "establish-subscription" RPC with the parameters listed in to request the creation of an adaptive subscription. The adaptive subscription configuration parameters require the server to report updates every 5 seconds if the rssi value is less than -65dB; If the rssi value is greater than or equal to -65dB, switch to 60 seconds period value.

<netconf:rpc message-id="101" xmlns:netconf="urn:ietf:params:xml:ns:netconf:base:1.0"> <establish-subscription xmlns="urn:ietf:params:xml:ns:yang:ietf-subscribed-notifications" xmlns:yp="urn:ietf:params:xml:ns:yang:ietf-yang-push"> <yp:datastore xmlns:ds="urn:ietf:params:xml:ns:yang:ietf-datastores"> ds:operational </yp:datastore> <yp:datastore-xpath-filter xmlns:wnd="http://example.com/yang/wifi-network-diagnostic"> /wnd:server </yp:datastore-xpath-filter> <as:adaptive-periods xmlns:as="urn:ietf:params:xml:ns:yang:ietf-adapt-subscription"> <as:adaptive-period> <as:name>adaptive-period-1</as:name> <as:xpath-external-eval> /wnd:server/wnd:rssi&lt;-65 </as:xpath-external-eval> <as:period>5</as:period> </as:adaptive-period> <as:adaptive-period> <as:name>adaptive-period-2</as:name> <as:xpath-external-eval> /wnd:server/wnd:rssi&gt;=-65 </as:xpath-external-eval> <as:period>60</as:period> </as:adaptive-period> </as:adaptive-periods> </establish-subscription> </netconf:rpc>

If the subscriber has authorization to establish the subscription with a server, but the server had not been able to fully satisfy the request from the subscriber, the server should send an RPC error response. For instance, if the XPATH 1.0 syntax against the targeted data object defined in "xpath-external-eval" is not supported by the server' s implementation, the server returns a reply indicating a failure. The following <rpc-reply> illustrates an example:

<?xml version="1.0" encoding="utf-8"?> <rpc-reply message-id="101" 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-adapt-subscription:xpath-evaluation-unsupported </error-app-tag> <error-path xmlns:wnd="http://example.com/yang/wifi-network-diagnostic"> /wnd:server/wnd:rssi </error-path> </rpc-error> </rpc-reply>

Since adaptive subscription allows a server to be configured with multiple different period intervals and corresponding XPath evaluation criteria to trigger update interval switch in the server, it may be possible for the server to return multiple <rpc-error> elements with "xpath-evaluation-unsupported" failure specified by different error paths. The subscriber can use this information in future attempts to establish a subscription.

Upon the server switches from the update interval 5 seconds to the new update interval 60 seconds, before sending event records to receivers, the "adaptive-period-update" notification should be generated and sent to the receivers to inform the receivers that the update interval value is switched to the new value.

<notification xmlns="urn:ietf:params:xml:ns:netconf:notification:1.0" xmlns:yp="urn:ietf:params:xml:ns:yang:ietf-yang-push"> <eventTime>2016-11-21T13:51:00Z</eventTime> <adaptive-period-update xmlns="urn:ietf:params:xml:ns:yang:ietf-adapt-subscription"> <id>1011</id> <period>60</period> <yp:datastore xmlns:ds="urn:ietf:params:xml:ns:yang:ietf-datastores"> ds:operational </yp:datastore> <yp:datastore-xpath-filter xmlns:wnd="http://example.com/yang/wifi-network-diagnostic"> /wnd:server </yp:datastore-xpath-filter> </adaptive-period-update> </notification>

This section is to be removed before publishing as an RFC. v02 -v03 Augment "modify-subscription", "subscription-started", "subscription-modified" to also support adaptive-subscription parameters; Replace the "anchor-time" parameter defined in adaptive-period-update notification with "period-update-time"; Fix the YANG module and XML snippet errors in Appendix sections. v01 -v02 Editorial changes to improve readability Clarify that "period" and "xpath-external-eval" parameters must be co-exist so that the period can be switched based on trigger conditions indicated by "xpath-external-eval" v00 -v01 Clarify what if multiple Xpath condition expressions conflict with each other during the lifecycle of an adaptive subscription Clarify that existing RPC errrors defined in RFC 8639 and 8641 are still supported by this document Refine the YANG module: add contact information, fix IETF Trust Copyright statement, fix yanglint validation error v09 -v10 Change the draft intended status to "experimental" Problem statement refinement v08 -v09 Define two new RPC errors to report when adaptive subscription unsupported or multiple XPath criteria conflict. Remove the "watermark" parameter. Add clarification about how to evaluate the XPath expression defined in "xpath-external-eval". Add clarification about how to compare a targeted data object in a specific list entry. v07 -v08 Define a new RPC error to report when an XPath syntax defined in "xpath-external-eval" is unsupported by a server. Add a new example showing how the RPC error being returned by a publisher. The usage examples fixed in the Appendix. Grammatical errors correction(missing articles, plurality mismatches, etc). v06 -v07 The usage examples typo fixed in the Appendix. Add reference to RFC7950 XPATH Evaluation section and XPATH 1.0 Clarify the definitions of 'xpath-external-eval' and 'selection-filter' by reusing XPATH Evaluation rules in RFC7950. Add a new terminology "adaptive subscription". Add one section to discuss Arbitrary XPath Complexity. v05 -v06 Replace example-wifi-mac module with example-wifi-network-diagnostic using WIFI statistics specified in CHIP specification. Update adaptive subscription Example to align with WIFI example module change. Add one more reference to CHIP Specification. v04 -v05 Remove "modify-subscption" RPC usage. Module update to fix the nits. Update adaptive subscription Example. Other Editorial changes. v03 - v04 Add missing subtrees and data nodes in the security section; Change "adaptive-update" notification into "adaptive-period-update" notification; Other Editorial changes. v02 - v03 Clarify the difference between low priority telemetry data dropping and collection rate switching in the introduction section; Update the abstract and introduction section to focus on collection rate switching in the server without interaction with the remote client; Format usage example and change ssid into rssi in the appendix; Use boilerplate and reuse the terms in the terminology section.