| NETCONF | B. Lengyel |
| Internet-Draft | Ericsson |
| Intended status: Standards Track | A. Clemm |
| Expires: June 11, 2020 | Futurewei |
| B. Claise | |
| Cisco Systems, Inc. | |
| December 9, 2019 |
YANG-Push Notification Capabilities
draft-ietf-netconf-notification-capabilities-08
This document proposes a YANG module that allows a publisher to specify capabilities related to "Subscription to YANG Datastores" (YANG-Push). It proposes to use YANG Instance Data to document this information and make it already available at implementation-time, but also allow it to be reported at run-time.
The YANG module is also prepared to contain other system capabilities, for future augmentations.
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 June 11, 2020.
Copyright (c) 2019 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.
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 terms YANG-Push, On-change subscription and Periodic subscription are used as defined in [RFC8641]
The terms Subscriber, Publisher and Receiver are used as defined in [RFC8639]
The term Server is used as defined in [RFC8342]
On-change Notification Capability: The capability of the publisher to send on-change notifications for a specific datastore or a specific data node.
Implementation-time information: Information about the publisher's behavior that is made available during the implementation of the publisher, available from a source other then a running server implementing the publisher.
Run-time information: Information about the publisher's behavior that is available from the running server (implementing the publisher) via management protocols such as NETCONF [RFC6241] or RESTCONF [RFC8040].
As defined in [RFC8641] a publisher may allow subscribers to subscribe to updates from a datastore and subsequently push such update notifications to the receiver. Notifications may be sent periodically or on-change (more or less immediately after each change).
A publisher supporting YANG-Push has a number of capabilities defined in [RFC8641] that are often determined during the implementation of the publisher. These include:
If the optional on-change feature is supported, additionally:
Publishers have limitations in how many update notifications and how many datastore node updates they can send out in a certain time-period.
Publishers might not support periodic subscriptions to all datastores.
In some cases, a publisher supporting on-change notifications will not be able to push updates for some object types on-change. Reasons for this might be that the value of the datastore node changes frequently (e.g. in-octets counter), that small object changes are frequent and irrelevant to the receiver (e.g., a temperature gauge changing 0.1 degrees within a predetermined and acceptable range), or that the implementation is not capable of on-change notification for a particular object. In those cases, it will be important for subscriber applications to have a way to identify which objects on-change notifications are supported and for which ones not.
Faced with the reality that support for on-change notification does not mean that such notifications will be sent for any specific data node, subscriber/management applications can not rely on the on-change functionality unless the subscriber has some means to identify which objects on-change notifications are supported. YANG models are meant to be used as an interface contract. Without identification of the data nodes actually supporting on-change, this contract would be incomplete.
This document proposes a YANG module that allows a subscriber to discover YANG-Push related capabilities both at implementation-time and run-time.
Implementation-time information is needed by Network Management System (NMS) implementers. A NMS implementation that wants to support notifications, needs the information about on-change notification capability. If the information is not documented in a way available to the NMS designer, but only as instance data from the network node once it is deployed, the NMS implementation will be delayed, because it has to wait for the network node to be ready. In addition, the assumption that all NMS implementers will have a correctly configured network node available to retrieve data from is an expensive proposition and may not always hold. (An NMS may need to be able to handle many dozens of network node types.) Often a fully functional NMS is a requirement for introducing a new network node type into a network, so delaying NMS readiness effectively also delays the time at which a new network node type can be introduced into the network.
Implementation-time information is needed by system integrators. When introducing a network node type into their network, operators often need to integrate the node type into their own management system. The NMS may have management functions that depend on on-change notifications. The network operator needs to plan his management practices and NMS implementation before he even decides to buy the specific network node type. Moreover the decision to buy the node type sometimes depends on these management possibilities.
Run-time information is needed:
The proposed YANG module is also intended as a base model to be augmented by other YANG modules defining system-capabilities not related to YANG-Push. Other capability defining YANG modules MAY augment the data nodes specifying these capabilites into this model.
It is a goal to provide YANG-Push notification capability information in a format that is:
The YANG module ietf-notification-capabilities is defined to provide the information. It contains:
Capability values can be specified on system/publisher level, datastore level or on specific data nodes (and their contained sub-tree) of a specific datastore. Capability values on a smaller, more specific part of the publisher's data always override more generic values.
Note: The solution is usable for both NMDA and non-NMDA systems. For non-NMDA servers/publishers the config=false data is considered as if it was part of the running datastore.
The information SHOULD be provided in two ways both following the ietf-notification-capabilities module:
The following tree diagram [RFC8340] provides an overview of the data model.
module: ietf-notification-capabilities
+--ro system-capabilities
+--ro subscription-capabilities
| +--ro (update-period)?
| | +--:(minimum-update-period)
| | | +--ro minimum-update-period? uint32
| | +--:(supported-update-period)
| | +--ro supported-update-period* uint32
| +--ro max-objects-per-update? uint32
| +--ro minimum-dampening-period? uint32 {yp:on-change}?
| +--ro on-change-supported? notification-support
| | {yp:on-change}?
| +--ro periodic-notifications-supported? notification-support
| +--ro supported-excluded-change-type* union {yp:on-change}?
+--ro datastore-capabilities* [datastore]
+--ro datastore -> /yanglib:yang-library/datastore/name
+--ro per-node-capabilities* [node-selector]
+--ro node-selector nacm:node-instance-identifier
+--ro subscription-capabilities
+--ro (update-period)?
| +--:(minimum-update-period)
| | +--ro minimum-update-period? uint32
| +--:(supported-update-period)
| +--ro supported-update-period* uint32
+--ro max-objects-per-update? uint32
+--ro minimum-dampening-period? uint32
| {yp:on-change}?
+--ro on-change-supported? notification-support
| {yp:on-change}?
+--ro periodic-notifications-supported?
| notification-support
+--ro supported-excluded-change-type* union
{yp:on-change}?
<CODE BEGINS> file "ietf-notification-capabilities@2019-12-09.yang"
module ietf-notification-capabilities {
yang-version 1.1;
namespace
"urn:ietf:params:xml:ns:yang:ietf-notification-capabilities";
prefix inc;
import ietf-netconf-acm {
prefix nacm;
description
"This module does not require NACM to be implemented, as
only a NACM typedef is used";
}
import ietf-yang-push {
prefix yp;
description
"This module requires ietf-yang-push to be implemented for the
two subscription-capabilities containers.";
}
import ietf-yang-library {
prefix yanglib;
description "This module requires ietf-yang-library to
be implemented. Revision 2019-01-04 or a
revision derived from it is required.";
}
organization
"IETF NETCONF (Network Configuration) Working Group";
contact
"WG Web: <https://datatracker.ietf.org/wg/netconf/>
WG List: <mailto:netconf@ietf.org>
Editor: Balazs Lengyel
<mailto:balazs.lengyel@ericsson.com>";
description
"This module specifies YANG-Push related publisher
capabilities.
The module contains
- capabilities related to the throughput of notification data the
publisher can support. (Note that for a specific subscription
the publisher MAY still allow only longer periods or smaller
updates depending on e.g. actual load conditions.)
- specification of which data nodes support on-change or periodic
notifications.
Capability values can be specified on system/publisher level,
datastore level or on specific data nodes (and their contained
sub-tree) of a specific datastore.
If a capability is specified on multiple levels, the
specification on a more specific level overrides more
generic capability specifications; thus
- a system/publisher level specification is overridden by any
other specification
- a datastore level specification (with a node-selector '/') is
overridden by a specification with a more specific node-selector.
- a specification for a specific datastore and node-selector
is overridden by a specification for the same datastore with
a node-slector that describes more levels of containing lists
and containers.
If, different data nodes covered by a single subscription
have different values for a specific capability, then using values
that are only acceptable for some of these data nodes, but not for
others, may result in the rejection of the subscription.
To find a capability value for a specific node in a
specific datastore the user SHALL
1) consider the system/publisher level capabilities under the
system-capabilities container if the
capability value is specified.
2) search for a datastore-capabilities list entry for
the specific datastore.
3) within that datastore entry search for a
per-node-capabilities entry that specifies the specific
capability and that has the node-selector selecting the
specific data node and that specifies the most levels of
containing containers and lists.
4) If no entries are found in the previous steps the
publisher is not capable of providing a value because
it is unknown, the capability is changing for some reason,
there is no specified limit etc. In this case the
publisher's behavior is unspecified.
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.
Copyright (c) 2019 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 Simplified BSD License
set forth in Section 4.c of the IETF Trust's Legal Provisions
Relating to IETF Documents
(http://trustee.ietf.org/license-info).
This version of this YANG module is part of RFC XXXX; see
the RFC itself for full legal notices.";
revision 2019-12-09 {
description
"Initial version";
reference
"RFC XXX: YANG-Push Notification Capabilities";
}
grouping subscription-capabilities {
description "Capabilities related to Yang-Push notifications";
container subscription-capabilities {
description "Capabilities related to Yang-Push notifications";
typedef notification-support {
type enumeration {
enum no-notifications-supported {
description "The publisher is not capable of sending any
notifications for the relevant scope and subscription
type." ;
}
enum notifications-for-config-changes-supported {
description "The publisher is capable of sending
notifications for config=true nodes, but not
for config=false nodes for the relevant scope
and subscription type." ;
}
enum notifications-for-state-changes-supported {
description "The publisher is capable of sending
notifications for config=false nodes, but not
for config=true nodes for the relevant scope
and subscription type." ;
}
enum notifications-for-all-changes-supported {
description "The publisher is capable of sending
notifications for both config=false and config=true
nodes for the relevant scope and subscription type." ;
}
}
description "Type for defining whether on-change or
periodic notifications are supported for no, only config=true,
only config=false or all data nodes.";
}
choice update-period {
description "Supported update period value or values for
periodic subscriptions.";
leaf minimum-update-period {
type uint32;
units "centiseconds";
description "Indicates the minimal update period that is
supported for a periodic subscription.
A periodic subscription to the selected data nodes must
specify a value that is at least as large or greater than
this";
reference
"The period leaf in RFC 8641 ietf-yang-push YANG module";
}
leaf-list supported-update-period {
type uint32;
units "centiseconds";
description "Supported update period values for a
periodic subscription.
A periodic subscription to the selected data nodes must
specify one of the values in the list; other values
are not supported.";
reference
"The period leaf in RFC 8641 ietf-yang-push YANG module";
}
}
leaf max-objects-per-update {
type uint32 {
range "1..max";
}
description
"Maximum number of objects that can be sent
in an update for the selected data nodes.";
}
leaf minimum-dampening-period {
if-feature yp:on-change;
type uint32;
units "centiseconds";
description
"The minimum dampening period supported for on-change
subscriptions for the selected data nodes.";
}
leaf on-change-supported {
if-feature yp:on-change;
type notification-support;
description
"Specifies whether the publisher is capable of
sending on-change notifications for the selected
data store or data nodes and the subtree below them.";
}
leaf periodic-notifications-supported {
type notification-support;
description
"Specifies whether the publisher is capable of
sending periodic notifications for the selected
data store or data nodes and the subtree below them.";
}
leaf-list supported-excluded-change-type {
if-feature yp:on-change;
type union {
type enumeration {
enum none {
description "None of the change types can be excluded.";
}
enum all {
description
"Any combination of change types can be excluded.";
}
}
type yp:change-type;
}
description "The change types that can be excluded in
YANG-Push subscriptions.";
}
}
}
container system-capabilities {
config false;
description "YANG-Push related publisher capabilities.
Capability values specified here at the publisher level
are valid for all datastores and
are used when the capability is not specified on the
datastore level or for specific data nodes. ";
uses subscription-capabilities {
refine subscription-capabilities/supported-excluded-change-type {
default none;
}
}
list datastore-capabilities {
key datastore;
description "Capabilities values per datastore.
For non-NMDA servers/publishers the config=false data is
considered as if it was part of the running datastore.";
leaf datastore {
type leafref {
path /yanglib:yang-library/yanglib:datastore/yanglib:name;
}
description "The datastore for which capabilities are defined.
Only individual datastores can be specified
e.g. ds:conventional is not allowed.";
}
list per-node-capabilities {
key "node-selector";
description
"Each list entry specifies notification capabilities
for the selected data nodes. The same capabilities apply for
the data nodes in the subtree below them unless another list
entry with a more specific node selector is present.";
leaf node-selector {
type nacm:node-instance-identifier;
description
"Selects the data nodes for which capabilities are
specified. The special value '/' denotes all data nodes
in the datastore.
The system SHOULD order list entries according to
the tree structure of the data models to make
reading/parsing the data model more simple.";
}
uses subscription-capabilities;
}
}
}
}
<CODE ENDS>
Other YANG modules defined in separate documents MAY augment this module to define other capabilities not related to YANG-Push. Every set of such capabilities SHOULD be wrapped in a container similar to the subscription-capabilities container in this YANG module to cleanly separate different groups of capabilities. The "other-capabilities" container SHOULD be augmented as a sibling to the subscription-capabilities container.
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 [RFC6241] or RESTCONF [RFC8040]. The lowest NETCONF layer is the secure transport layer, and the mandatory-to-implement secure transport is Secure Shell (SSH) [RFC6242]. The lowest RESTCONF layer is HTTPS, and the mandatory-to-implement secure transport is TLS [RFC8446].
The Network Configuration Access Control Model (NACM) [RFC8341] 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.
All protocol-accessible data nodes are read-only and cannot be modified. The data in this module is not security sensitive. Access control may be configured, to avoid exposing the read-only data.
When that data is in file format, data should be protected against modification or unauthorized access using normal file handling mechanisms.
This document registers one URI in the IETF XML registry [RFC3688]. Following the format in [RFC3688], the following registrations are requested:
URI: urn:ietf:params:xml:ns:yang:ietf-notification-capabilities Registrant Contact: The NETCONF WG of the IETF. XML: N/A, the requested URI is an XML namespace.
This document registers one YANG module in the YANG Module Names registry [RFC7950]. Following the format in [RFC7950], the the following registrations are requested:
name: ietf-notification-capabilities namespace: urn:ietf:params:xml:ns:yang:ietf-notification-capabilities prefix: inc reference: RFC XXXX
| [I-D.ietf-netmod-yang-instance-file-format] | Lengyel, B. and B. Claise, "YANG Instance Data File Format", Internet-Draft draft-ietf-netmod-yang-instance-file-format-06, December 2019. |
| [RFC6241] | Enns, R., Bjorklund, M., Schoenwaelder, J. and A. Bierman, "Network Configuration Protocol (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011. |
| [RFC6242] | Wasserman, M., "Using the NETCONF Protocol over Secure Shell (SSH)", RFC 6242, DOI 10.17487/RFC6242, June 2011. |
| [RFC7950] | Bjorklund, M., "The YANG 1.1 Data Modeling Language", RFC 7950, DOI 10.17487/RFC7950, August 2016. |
| [RFC8040] | Bierman, A., Bjorklund, M. and K. Watsen, "RESTCONF Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017. |
| [RFC8342] | Bjorklund, M., Schoenwaelder, J., Shafer, P., Watsen, K. and R. Wilton, "Network Management Datastore Architecture (NMDA)", RFC 8342, DOI 10.17487/RFC8342, March 2018. |
| [RFC8446] | Rescorla, E., "The Transport Layer Security (TLS) Protocol Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018. |
| [RFC8639] | Voit, E., Clemm, A., Gonzalez Prieto, A., Nilsen-Nygaard, E. and A. Tripathy, "Subscription to YANG Notifications", RFC 8639, DOI 10.17487/RFC8639, September 2019. |
| [RFC8641] | Clemm, A. and E. Voit, "Subscription to YANG Notifications for Datastore Updates", RFC 8641, DOI 10.17487/RFC8641, September 2019. |
| [RFC2119] | Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997. |
| [RFC3688] | Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688, DOI 10.17487/RFC3688, January 2004. |
| [RFC8174] | Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017. |
| [RFC8340] | Bjorklund, M. and L. Berger, "YANG Tree Diagrams", BCP 215, RFC 8340, DOI 10.17487/RFC8340, March 2018. |
<?xml version="1.0" encoding="UTF-8"?>
<instance-data-set xmlns=
"urn:ietf:params:xml:ns:yang:ietf-yang-instance-data">
<name>acme-switch-notification-capabilities</name>
<yid-version>1</yid-version>
<content-schema>
<module>ietf-notification-capabilities@2019-12-04</module>
</content-schema>
<!-- revision date, contact, etc. -->
<description>Notification capabilities of acme-switch.
Acme-switch implements the running, candidate and operational
datastores. Every change can be reported on-change from running,
nothing from candidate and all config=false data from operational.
Periodic subscriptions are supported for running and
operational, but not for candidate.
</description>
<content-data>
<system-capabilities
xmlns="urn:ietf:params:xml:ns:yang:ietf-notification-capabilities"
xmlns:ds="urn:ietf:params:xml:ns:yang:ietf-datastores">
<subscription-capabilities>
<minimum-update-period>500</minimum-update-period>
<max-objects-per-update>2000</max-objects-per-update>
<minimum-dampening-period>100</minimum-dampening-period>
<periodic-notifications-supported>
notifications-for-all-changes-supported
</periodic-notifications-supported>
</subscription-capabilities>
<datastore-capabilities>
<datastore>ds:operational</datastore>
<per-node-capabilities>
<node-selector>/</node-selector>
<subscription-capabilities>
<on-change-supported>
notifications-for-state-changes-supported
</on-change-supported>
</subscription-capabilities>
</per-node-capabilities>
</datastore-capabilities>
<datastore-capabilities>
<datastore>ds:candidate</datastore>
<per-node-capabilities>
<node-selector>/</node-selector>
<subscription-capabilities>
<on-change-supported>no-notifications-supported
</on-change-supported>
<periodic-notifications-supported>
no-notifications-supported
</periodic-notifications-supported>
</subscription-capabilities>
</per-node-capabilities>
</datastore-capabilities>
<datastore-capabilities>
<datastore>ds:running</datastore>
<per-node-capabilities>
<node-selector>/</node-selector>
<subscription-capabilities>
<on-change-supported>
notifications-for-all-changes-supported
</on-change-supported>
</subscription-capabilities>
</per-node-capabilities>
</datastore-capabilities>
</system-capabilities>
</content-data>
</instance-data-set>
Figure 1: Notification Capabilities with datastore level settings
The following example is instance-data describing the notification capabilities of a hypothetical "acme-switch". The switch implements the running, candidate and operational datastores. Every change can be reported on-change from running, nothing from candidate and all config=false data from operational. Periodic subscriptions are supported for running and operational, but not for candidate.
<?xml version="1.0" encoding="UTF-8"?>
<instance-data-set xmlns=
"urn:ietf:params:xml:ns:yang:ietf-yang-instance-data">
<name>acme-router-notification-capabilities</name>
<yid-version>1</yid-version>
<content-schema>
<module>ietf-notification-capabilities@2019-12-04</module>
</content-schema>
<!-- revision date, contact, etc. -->
<description>Defines the notification capabilities of an acme-router.
The router only has running, and operational datastores.
Every change can be reported on-change from running, but
only config=true nodes and some config=false data from operational.
Statistics are not reported on-change only 2 important counters,
for these a smaller dampening period is possible.
</description>
<content-data>
<system-capabilities
xmlns="urn:ietf:params:xml:ns:yang:ietf-notification-capabilities"
xmlns:ds="urn:ietf:params:xml:ns:yang:ietf-datastores">
<subscription-capabilities>
<minimum-update-period>500</minimum-update-period>
<max-objects-per-update>2000</max-objects-per-update>
<minimum-dampening-period>100</minimum-dampening-period>
<periodic-notifications-supported>
notifications-for-all-changes-supported
</periodic-notifications-supported>
<on-change-supported>
notifications-for-all-changes-supported
</on-change-supported>
<supported-excluded-change-type>
all
</supported-excluded-change-type>
</subscription-capabilities>
<datastore-capabilities>
<datastore>ds:operational</datastore>
<per-node-capabilities>
<node-selector>
/if:interfaces/if:interface/if:statistics</node-selector>
<subscription-capabilities>
<on-change-supported>
no-notifications-supported
</on-change-supported>
</subscription-capabilities>
</per-node-capabilities>
<per-node-capabilities>
<node-selector>
/if:interfaces/if:interface/if:statistics/if:in-octets
</node-selector>
<subscription-capabilities>
<minimum-dampening-period>10</minimum-dampening-period>
<on-change-supported>
notifications-for-all-changes-supported
</on-change-supported>
</subscription-capabilities>
</per-node-capabilities>
<per-node-capabilities>
<node-selector>
/if:interfaces/if:interface/if:statistics/if:out-octets
</node-selector>
<subscription-capabilities>
<minimum-dampening-period>10</minimum-dampening-period>
<on-change-supported>
notifications-for-all-changes-supported
</on-change-supported>
</subscription-capabilities>
</per-node-capabilities>
</datastore-capabilities>
</system-capabilities>
</content-data>
</instance-data-set>
Figure 2: Notification Capabilities with data node specific settings
The following is the instance-data describing the notification capabilities of a hypothetical "acme-router". The router implements the running, and operational datastores. Every change can be reported on-change from running, but only config=true nodes and some config=false data from operational. Interface statistics are not reported on-change only 2 important counters. Datastore subscription capabilities are not reported on-change as they never change on the acme-router during run-time.
v07 - v08
v06 - v07
v05 - v06
v04 - v05
v03 - v04
v02 - v03
v01 - v02
v00 - v01