Netconf B. Lengyel
Internet-Draft Ericsson
Intended status: Standards Track A. Clemm
Expires: December 15, 2018 Huawei USA
June 13, 2018
YangPush Notification Capabilities
draft-lengyel-netconf-notification-capabilities-01
Abstract
This document proposes a YANG module that allows a YANG server to
specify for which data nodes it will send "YANG Datastore
Subscription" on-change notifications. It also proposes to use YANG
Instance Data to document this information in implementation time.
Status of This Memo
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Table of Contents
1. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
3. On-change Notification Capability Model . . . . . . . . . . . 4
3.1. Tree Diagram . . . . . . . . . . . . . . . . . . . . . . 5
3.2. YANG Module . . . . . . . . . . . . . . . . . . . . . . . 5
4. Security Considerations . . . . . . . . . . . . . . . . . . . 8
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
5.1. The IETF XML Registry . . . . . . . . . . . . . . . . . . 8
5.2. The YANG Module Names Registry . . . . . . . . . . . . . 8
6. Open Issues . . . . . . . . . . . . . . . . . . . . . . . . . 8
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
7.1. Normative References . . . . . . . . . . . . . . . . . . 9
7.2. Informative References . . . . . . . . . . . . . . . . . 9
Appendix A. Changes between revisions . . . . . . . . . . . . . 9
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.
On-change Notification Capability: The capability of the YANG server
to send on-change notifications on the change of the value for a
specific data node.
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 immendiately after each
change).
In some cases, a publisher supporting on-change notifications will
not be able to push updates for some object types on-change. Reasons
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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 they
are not supported.
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 and for which ones they
are not supported. YANG models are meant to be used as an interface
contract. Without identification of data nodes supporting on-change,
today this contract only states 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 identify
which data nodes support on-change notification, removing the
uncertainty for on-change notifications.
On-change Notification Capability information will be needed both in
implementation-time and run-time.
Run-time information is needed
o for any "purely model driven" client
o to check that early information about the capability is indeed
what the server supports
o in case the capability might change during run-time e.g. due to
licensing, HW constraints etc.
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, 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 very expensive. (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
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network, so delaying the NMS effectively delays the availability of
the network node as well.
Implementation time information is needed by system integrators.
System integrators will need information about on change notification
capability early. 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.
3. On-change Notification Capability Model
As described above a number of stakeholders need information about
the on change notification capability both in implementation and run-
time. It is a goal to provide this 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
information about the on-change notification capabilities. It is
defined as an extension to the ietf-yang-library module
[I-D.ietf-netconf-rfc7895bis]. For each implemented YANG Module
listed in the ietf-yang-library there is a default notification
capability separately for config false and config true data nodes.
There is also an on-change-notification-capability list containing a
potentially different true/false notification capability for any data
nodes in the schema tree. Unless a node is in the 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.
The instance 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.
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o It SHALL be available via Netconf or Restconf from the live YANG
server during runtime.
If the information retrieved via Netconf/Restconf and the YANG
Instance Data File conflict, the former MUST be considered
authorative.
3.1. Tree Diagram
The following tree diagram [I-D.ietf-netmod-yang-tree-diagrams]
provides an overview of the data model.
module: ietf-notification-capabilities
augment /yanglib:yang-library/yanglib:module-set:
+--ro notification-sent-for-config-default? boolean
+--ro notification-sent-for-state-default? boolean
+--ro on-change-notification-capability* [data-node-selector]
+--ro data-node-selector nacm:node-instance-identifier
+--ro on-change-notification-sent? boolean
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-yang-library {
prefix yanglib;
reference "rfc7895bis";
// at least revision 2018-xx-yy
}
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>
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WG Chair: Mahesh Jethanandani
<mailto:mjethanandani@gmail.com>
Editor: Balazs Lengyel
<mailto:balazs.lengyel@ericsson.com>";
description "This module augments the ietf-yang-library to
specify per module for which data nodes will the YANG server
send 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:
- it is specified in the on-change-notification-capability
list and has a on-change-notification-sent value true or
- notifications are sent for its parent data node and it is
not specified in the on-change-notification-capability list or
- 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.
On-change notifications SHALL be sent for a config=false
data node if one of the following is true:
- it is specified in the on-change-notification-capability
list and has an on-change-notification-sent value 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
- 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.
";
revision 2018-06-12 {
description "Initial version";
reference
"RFC XXX: YangPush Notification Capabilities";
}
augment /yanglib:yang-library/yanglib:module-set/yanglib:module {
description "Extends the ietf-yang-library module with
on-change-notification-capability information";
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leaf notification-sent-for-config-default {
type boolean;
default true;
description "Specifies the default value for this module's
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 for this module's
top level state data nodes for the
on-change-notification-sent capability.";
}
list on-change-notification-capability {
key data-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 data-node-selector {
type nacm:node-instance-identifier;
description data-node-selector;
}
leaf on-change-notification-sent {
type boolean;
description "Specifies whether the YANG server will
send on-change notifications for the selected
data nodes.";
}
}
}
}
<CODE ENDS>
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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.
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
Should we augment the old module-state subtree as well? We could
make it conditional: "when /yanglib:yang-library-change/
yanglib:module-set-id ;
Should type nacm:node-instance-identifier be moved to yang-types?
It is useful for more then just nacm.
7. References
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7.1. Normative References
[I-D.ietf-netconf-rfc7895bis]
Bierman, A., Bjorklund, M., Schoenwaelder, J., Watsen, K.,
and R. Wilton, "YANG Library", draft-ietf-netconf-
rfc7895bis-06 (work in progress), April 2018.
[I-D.ietf-netconf-yang-push]
Clemm, A., Voit, E., Prieto, A., Tripathy, A., Nilsen-
Nygaard, E., Bierman, A., and B. Lengyel, "YANG Datastore
Subscription", draft-ietf-netconf-yang-push-16 (work in
progress), May 2018.
[I-D.lengyel-netmod-yang-instance-data]
Lengyel, B. and B. Claise, "YANG Instance Data Files and
their use for Documenting Server Capabilities", draft-
lengyel-netmod-yang-instance-data-00 (work in progress),
February 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
[I-D.ietf-netmod-yang-tree-diagrams]
Bjorklund, M. and L. Berger, "YANG Tree Diagrams", draft-
ietf-netmod-yang-tree-diagrams-06 (work in progress),
February 2018.
[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>.
Appendix A. Changes between revisions
v00 - v01
o Corrections
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o Augment only the new yanglib
o Correct the condtions for notifying state data
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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