Netconf B. Lengyel
Internet-Draft Ericsson
Intended status: Standards Track A. Clemm
Expires: September 2, 2019 Huawei USA
March 1, 2019
YangPush Notification Capabilities
draft-ietf-netconf-notification-capabilities-01
Abstract
This document proposes a YANG module that allows a YANG server to
specify server capabilities related to "Subscription to YANG
Datastores" (YangPush). It proposes to use YANG Instance Data to
document this information already in implementation time.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on September 2, 2019.
Copyright Notice
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document authors. All rights reserved.
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Table of Contents
1. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
3. Notification Capability Model . . . . . . . . . . . . . . . . 4
3.1. Tree Diagram . . . . . . . . . . . . . . . . . . . . . . 5
3.2. YANG Module . . . . . . . . . . . . . . . . . . . . . . . 6
4. Security Considerations . . . . . . . . . . . . . . . . . . . 9
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
5.1. The IETF XML Registry . . . . . . . . . . . . . . . . . . 9
5.2. The YANG Module Names Registry . . . . . . . . . . . . . 9
6. Open Issues . . . . . . . . . . . . . . . . . . . . . . . . . 9
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 10
7.1. Normative References . . . . . . . . . . . . . . . . . . 10
7.2. Informative References . . . . . . . . . . . . . . . . . 10
Appendix A. Changes between revisions . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
1. Terminology
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 YANG server
to support On-change subscriptions.
Implementation-time information: Information about the YANG server's
behavior that is made available during the implementation of the
server, available from a source other then a running Yang server.
Rutime-information: Information about the YANG server's behavior that
is available from the running YANG server via a protocol like
NETCONF, RESTCONF or HTTPS.
2. Introduction
As defined in [I-D.ietf-netconf-yang-push] a YANG 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).
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A YANG server supporting YANG-Push has a number of capabilities that
are determined during the implementation of the server. These
include:
o Supported dampening periods for on-change subscriptions
o Supported (reporting) periods for periodic subscriptions
o Maximum number of objects that can be sent in an update
o The set of data nodes for which on-change notification is
supported
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 data
nodes supporting on-change, this contract would only state the YANG
server may (or may not) send on-change notifications for a data node
specified in a YANG module.
This document proposes a YANG module that allows a client to discover
YANG-Push related capabilities.
YANG-Push related capability information will be needed both in
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
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the network node, the NMS implementation will be delayed, because it
has to wait for the network node to be ready. Also assuming that all
NMS implementers will have a correctly configured network node
available to retrieve data from, is an expensive proposition. (An
NMS may handle 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 the NMS effectively delays the
availability of the network node as well.
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
o for any "purely model driven" client, e.g. a NETCONF-browser. As
long as it has a valid model to read the capability information,
it does not care which data nodes send notification, it will just
handle what is available.
o in case the capability might change during run-time e.g. due to
licensing, HW constraints etc.
o to check that early, implementation time capability information
about the capabilities is indeed what the server implements (is
the supplied documentation correct?)
3. Notification Capability Model
It is a goal to provide YangPush notification capability information
in a format that is
o vendor independent (standard)
o formal (no freeform English text please)
o the same both in implementation-time and run-time
The YANG module ietf-notification-capabilities is defined to provide
the information. It contains
a set of capabilities related to the amount of notifications the
server can send out
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a default on-change notification capability separately for config
false and config true data nodes
an on-change-notification-capability list containing a potentially
different true/false notification capability for a few data nodes
in the schema tree. Unless a node is in this list with a specific
capability value, it inherits its on-change-notification-
capability from its parent in the data tree, or from the relevant
default values. It is assumed that only a small number of nodes
will be included in this list: special cases where the default
behavior is not followed. For a detailed description of the usage
of this list see the description in the YANG module.
The information SHALL be provided in two ways both following the
ietf-notification-capabilities module:
o It SHALL be provided by the implementer as YANG instance data file
complying to the [I-D.lengyel-netmod-yang-instance-data]. The
file SHALL be available already in implementation time retrievable
in a way that does not depend on a live network node. E.g.
download from product Website.
o It SHALL be available via NETCONF or RESTCONF from the live YANG
server during runtime.
3.1. Tree Diagram
The following tree diagram [RFC8340] provides an overview of the data
model.
module: ietf-notification-capabilities
+--ro yangpush-notification-capabilities
+--ro minimum-dampening-period? uint32
+--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 notification-sent-for-config-default? boolean
+--ro notification-sent-for-state-default? boolean
+--ro on-change-notification-capability* [node-selector]
+--ro node-selector nacm:node-instance-identifier
+--ro on-change-notification-sent boolean
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3.2. YANG Module
<CODE BEGINS> file "ietf-notification-capabilities.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; }
organization
"IETF NETCONF (Network Configuration) Working Group";
contact
"WG Web: <https://datatracker.ietf.org/wg/netconf/>
WG List: <mailto:netconf@ietf.org>
WG Chair: Kent Watsen
<mailto:kwatsen@juniper.net>
WG Chair: Mahesh Jethanandani
<mailto:mjethanandani@gmail.com>
Editor: Balazs Lengyel
<mailto:balazs.lengyel@ericsson.com>";
description "This module specifies YANG-Push related server
capabilities. It contains
- capabilities related to the amount of notifications the
server can send out
- default and schema node specific information specifying
the set of data nodes for which the YANG server is capable
of sending on-change notifications.
On-change notification capability is marked as true or false.
This marking is inherited from the parent down the data tree
unless explicitly marked otherwise.
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
on-change-notification-capability list and the
notification-sent-for-config-default is true; or
- notifications are sent for its parent data node and it is
not specified in the on-change-notification-capability list; or
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- it is specified in the on-change-notification-capability
list and has a on-change-notification-sent 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 or has a config=true parent
data node and is not specified in the
on-change-notification-capability list and the
notification-sent-for-state-default is true; or
- notifications are sent for its parent data node
which is also config=false and it is
not specified in the on-change-notification-capability list; or
- it is specified in the on-change-notification-capability
list and has an on-change-notification-sent value true or
";
revision 2019-02-28 {
description "Initial version";
reference
"RFC XXX: YangPush Notification Capabilities";
}
container yangpush-notification-capabilities {
config false;
description "YANG-Push related server capabilities";
leaf minimum-dampening-period {
type uint32;
units msec;
description "The minimum dampening period supported for on-change
subscriptions.";
}
choice update-period {
description "Supported 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 "Specific supported update period values
for a periodic subscription";
}
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}
leaf max-objects-per-update {
type uint32;
description "Maximum number of objects that can be sent
in an update";
}
leaf notification-sent-for-config-default {
type boolean;
default true;
description "Specifies the default value for
top level configuration data nodes for the
on-change-notification-sent capability.";
}
leaf notification-sent-for-state-default {
type boolean;
default false;
description "Specifies the default value
top level state data nodes for the
on-change-notification-sent capability.";
}
list on-change-notification-capability {
key node-selector ;
description "A list of data nodes that have the
on-change-notification-capability specifically defined.
Should be used when specific data nodes support
on-change notification in a module/subtree that
generally does not support it or when some data nodes
do not support the notification in a module/subtree
that generally supports on-change notifications.";
leaf node-selector {
type nacm:node-instance-identifier;
description "Selects the data nodes for which
on-change capability is specified.";
}
leaf on-change-notification-sent {
type boolean;
mandatory true;
description "Specifies whether the YANG server will
send on-change notifications for the selected
data nodes.";
}
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}
}
}
<CODE ENDS>
4. Security Considerations
The YANG module defined in this document is designed to be accessed
via YANG based management protocols, such as NETCONF and RESTCONF.
Both of these protocols have mandatory-to- implement secure transport
layers (e.g., SSH, TLS) with mutual authentication.
The NETCONF access control model (NACM) provides the means to
restrict access for particular users to a pre-configured subset of
all available protocol operations and content.
The data in this module is not security sensitive.
5. IANA Considerations
5.1. The IETF XML Registry
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.
5.2. The YANG Module Names Registry
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
6. Open Issues
Do we need separate defaults/individual lists for every datastore?
Proposal: no, it would be an overkill.
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Should type nacm:node-instance-identifier be moved to yang-types?
It is useful for more then just nacm.
7. References
7.1. Normative References
[I-D.ietf-netconf-yang-push]
Clemm, A., Voit, E., Prieto, A., Tripathy, A., Nilsen-
Nygaard, E., Bierman, A., and B. Lengyel, "Subscription to
YANG Datastores", draft-ietf-netconf-yang-push-22 (work in
progress), February 2019.
[I-D.lengyel-netmod-yang-instance-data]
Lengyel, B. and B. Claise, "YANG Based Instance Data Files
Format", draft-lengyel-netmod-yang-instance-data-05 (work
in progress), October 2018.
[RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
RFC 7950, DOI 10.17487/RFC7950, August 2016,
<https://www.rfc-editor.org/info/rfc7950>.
7.2. Informative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
DOI 10.17487/RFC3688, January 2004,
<https://www.rfc-editor.org/info/rfc3688>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8340] Bjorklund, M. and L. Berger, Ed., "YANG Tree Diagrams",
BCP 215, RFC 8340, DOI 10.17487/RFC8340, March 2018,
<https://www.rfc-editor.org/info/rfc8340>.
Appendix A. Changes between revisions
v00 - v01
o Add more capabilities: minimum period, supported period max-number
of objects, min dampening period, dampening supported
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Authors' Addresses
Balazs Lengyel
Ericsson
Magyar Tudosok korutja 11
1117 Budapest
Hungary
Email: balazs.lengyel@ericsson.com
Alexander Clemm
Huawei USA
2330 Central Expressway
Santa Clara, CA 95050
USA
Email: ludwig@clemm.org
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