| NETCONF | B. Lengyel |
| Internet-Draft | Ericsson |
| Intended status: Standards Track | A. Clemm |
| Expires: March 8, 2020 | Futurewei |
| B. Claise | |
| Cisco Systems, Inc. | |
| September 5, 2019 |
Yang-Push Notification Capabilities
draft-ietf-netconf-notification-capabilities-04
This document proposes a YANG module that allows a server to specify server 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.
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 March 8, 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 [I-D.ietf-netconf-yang-push]
On-change Notification Capability: The capability of the server to support On-change subscriptions.
The term Server is used as defined in [RFC8342]
Implementation-time information: Information about the server's behavior that is made available during the implementation of the server, available from a source other then a running server.
Run-time information: Information about the server's behavior that is available from the running server via management protocols such as NETCONF [RFC6241] or RESTCONF [RFC8040].
As defined in [I-D.ietf-netconf-yang-push] a server may allow clients to subscribe to updates from a datastore and subsequently push such update notifications to the client. Notifications may be sent periodically or on-change (more or less immediately after each change).
A server supporting YANG-Push has a number of capabilities defined in [I-D.ietf-netconf-yang-push] that are often determined during the implementation of the server. These include:
If the optional on-change feature is supported, additionally:
Servers MAY have limitations in how many update notifications and how many datastore node updates they can send out in a certain time-period.
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 meaningless (e.g., a temperature gauge changing 0.1 degrees), or that the implementation is not capable of on-change notification for a particular object. In those cases, it will be important for client applications to have a way to identify for 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, client/management applications can not rely on the on-change functionality unless the client has some means to identify for 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 client to discover YANG-Push related capabilities both at implementation-time and run-time.
Implementation time information is needed by Network Management System (NMS) implementers. During NMS implementation for any functionality that depends on the notifications the information about on change notification capability is needed. If the information is not available early in some document, 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:
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:
The information SHALL 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 datastore-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 datastore-capabilities* [datastore]
+--ro datastore union
+--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-for-config? boolean {yp:on-change}?
+--ro on-change-supported-for-state? boolean {yp:on-change}?
+--ro per-node-capabilities* [node-selector]
+--ro node-selector nacm:node-instance-identifier
+--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 boolean {yp:on-change}?
<CODE BEGINS> file "ietf-notification-capabilities@2019-08-13.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; }
import ietf-yang-push { prefix yp; }
import ietf-yang-library {
prefix yanglib;
description
"Requires revision 2019-01-04 or a revision derived from it.";
}
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 server
capabilities.
The module contains
- capabilities related to the amount of notifications the
server can send out. (Note that for a specific subscription
the server MAY still allow only longer periods or smaller
updates depending on e.g. actual load conditions.)
- specification of which data nodes support on-change
notifications.
Capability values on a
smaller, more specific part of the server's data always override
more generic values. The hierarchy of specifications from generic
to more specific is:
1) top level values valid for all datastores
2) values for a specific datastore (including the special
'all' datastore identifier)
3) Value for a specific data node and its contained sub-tree
in one of the datastores. Such capability values are inherited
down the containment tree unless a more specific value is
provided, as described in 4)
4) A contained, smaller, more specific sub-tree in a specific
datastore (could be a single leaf)
Any capability value MAY be absent if a more generic capability
value is already provided or if the server is not capable of
providing a value.
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 2019-08-13 {
description
"Initial version";
reference
"RFC XXX: Yang-Push Notification Capabilities";
}
container datastore-subscription-capabilities {
config false;
description
"YANG-Push related server capabilities";
grouping datastore-subscription-throughput-capabilities {
description "Capability values that affect the amount of
notifications the server can send out.";
choice update-period {
description
"Supported update-period values.";
leaf minimum-update-period {
type uint32;
units "centiseconds";
description
"Minimum update period supported for a
periodic subscription.";
}
leaf-list supported-update-period {
type uint32;
units "centiseconds";
description "Supported update period values for a
periodic subscription (used if only these specific
values are supported).";
}
}
leaf max-objects-per-update {
type uint32 {
range "1..max";
}
description
"Maximum number of objects that can be sent
in an update.";
}
leaf minimum-dampening-period {
if-feature yp:on-change ;
type uint32;
units "centiseconds";
description
"The minimum dampening period supported for on-change
subscriptions.";
}
}
uses datastore-subscription-throughput-capabilities {
description "Top level throughput capabilities.
These values can be overridden by values provided per
datastore or for individual data nodes in a datastore.";
}
list datastore-capabilities {
key datastore ;
description "Capabilities values per datastore.
For non-NMDA servers the config=false data is considered
as if it was part of the running datastore.
Indicates per datastore throughput capabilities.
Indicates per datastore the data nodes for which the
server is capable of sending on-change notifications.
If a datastore implemented by the server is not specified
in this list and there is no list element for 'all' datastores
the datastore does not support any on-change notifications.
On-change notifications SHALL be sent for a config=true
data node if one of the following is true:
- if it is a top level data-node and is not specified in the
per-node-capabilities list and on-change-supported-for-config
is true; or
- notifications are sent for its parent data node and it is
not specified in the per-node-capabilities list; or
- it is specified in the per-node-capabilities list and has
an on-change-supported value true.
On-change notifications SHALL be sent for a config=false
data node if one of the following is true:
- if it is a top level data-node (a config=false data node with
a config=true parent SHALL be treated as a top level data node)
and is not specified in the per-node-capabilities list and
on-change-supported-for-state is true; or
- notifications are sent for its parent data node
which is also config=false and it is not specified in the
per-node-capabilities list; or
- it is specified in the per-node-capabilities list and has
an on-change-supported value true";
leaf datastore {
type union {
type leafref {
path /yanglib:yang-library/yanglib:datastore/yanglib:name ;
}
type enumeration {
enum all ;
}
}
must '. != "all" or count(..) = "1" ' {
error-message
"If 'all' is present individual datastores cannot be " +
"specified.";
}
description "The datastore for which capabilities are defined.";
}
uses datastore-subscription-throughput-capabilities {
description "Throughput capabilities for a datastore.
These values will override top level values and can be
overridden by values provided for individual data nodes
in a datastore.";
}
leaf on-change-supported-for-config {
if-feature yp:on-change ;
type boolean;
default "true";
description
"Specifies the default value for
top level config=true data nodes for the
on-change-supported capability.";
}
leaf on-change-supported-for-state {
if-feature yp:on-change ;
type boolean;
default "false";
description
"Specifies the default value for
top level config=false data nodes for the
on-change-supported capability.";
}
list per-node-capabilities {
key "node-selector";
description
"A list of data nodes that have either a throughput or
on-change-notification capability specifically defined.
Should be used only when specific data nodes support
capabilities that are different from capabilities
of their parent nodes or the default for the datastore.";
leaf node-selector {
type nacm:node-instance-identifier;
description
"Selects the data nodes for which
a capability is specified.";
}
uses datastore-subscription-throughput-capabilities {
description "Throughput capabilities for a specific data node.
These values will override top level or datastore
specific values.";
}
leaf on-change-supported {
if-feature yp:on-change ;
type boolean;
mandatory true;
description
"Specifies whether the server is capable of
sending on-change notifications for the selected
data nodes.";
}
}
}
}
}
<CODE ENDS>
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.
The data in this module is not security sensitive.
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-netconf-yang-push] | Clemm, A. and E. Voit, "Subscription to YANG Datastores", Internet-Draft draft-ietf-netconf-yang-push-25, May 2019. |
| [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-04, August 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. |
| [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>
<module>ietf-notification-capabilities@2019-08-13.yang</module>
<!-- 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.
</description>
<content-data>
<datastore-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>
<datastore-capabilities>
<datastore xmlns="urn:ietf:params:xml:ns:yang:ietf-datastores">
running
</datastore>
<!-- Neither on-change-supported-for-config nor
on-change-supported-for-state are present as the
default values are in effect. -->
</datastore-capabilities>
<!-- The candidate datastore is implemented, but not present
here as it does not support any on-change notifications. -->
<datastore-capabilities>
<datastore xmlns="urn:ietf:params:xml:ns:yang:ietf-datastores">
operational
</datastore>
<on-change-supported-for-config>
false
</on-change-supported-for-config>
<on-change-supported-for-state>
true
</on-change-supported-for-state>
</datastore-capabilities>
</datastore-subscription-capabilities>
</content-data>
</instance-data-set>
Figure 1: Notification Capabilities with default 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.
<?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>
<module>ietf-notification-capabilities@2019-08-13.yang</module>
<!-- 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>
<datastore-subscription-capabilities
xmlns="urn:ietf:params:xml:ns:yang:ietf-notification-capabilities">
<minimum-update-period>500</minimum-update-period>
<max-objects-per-update>2000</max-objects-per-update>
<minimum-dampening-period>100</minimum-dampening-period>
<datastore-capabilities>
<datastore xmlns="urn:ietf:params:xml:ns:yang:ietf-datastores">
running
</datastore>
</datastore-capabilities>
<datastore-capabilities>
<datastore xmlns="urn:ietf:params:xml:ns:yang:ietf-datastores">
operational
</datastore>
<on-change-supported-for-state>
true
</on-change-supported-for-state>
<per-node-capabilities>
<node-selector>
/inc:datastore-subscription-capabilities</node-selector>
<on-change-supported>false</on-change-supported>
</per-node-capabilities>
<per-node-capabilities>
<node-selector>
/if:interfaces/if:interface/if:statistics</node-selector>
<on-change-supported>false</on-change-supported>
</per-node-capabilities>
<per-node-capabilities>
<node-selector>
/if:interfaces/if:interface/if:statistics/if:in-octets
</node-selector>
<minimum-dampening-period>10</minimum-dampening-period>
<on-change-supported>true</on-change-supported>
</per-node-capabilities>
<per-node-capabilities>
<node-selector>
/if:interfaces/if:interface/if:statistics/if:out-octets
</node-selector>
<on-change-supported>true</on-change-supported>
<minimum-dampening-period>10</minimum-dampening-period>
</per-node-capabilities>
</datastore-capabilities>
</datastore-subscription-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.
v03 - v04
v02 - v03
v01 - v02
v00 - v01