RFC8632: A YANG Data Model for Alarm Management
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Related keywords:
(fault management)
(Monitoring)
Internet Engineering Task Force (IETF) S. Vallin
Request for Comments: 8632 Stefan Vallin AB
Category: Standards Track M. Bjorklund
ISSN: 2070-1721 Cisco
September 2019
A YANG Data Model for Alarm Management
Abstract
This document defines a YANG module for alarm management. It
includes functions for alarm-list management, alarm shelving, and
notifications to inform management systems. There are also
operations to manage the operator state of an alarm and
administrative alarm procedures. The module carefully maps to
relevant alarm standards.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 7841.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc8632.
Copyright Notice
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.
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RFC 8632 A YANG Data Model for Alarm Management September 2019
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Terminology and Notation . . . . . . . . . . . . . . . . 3
2. Objectives . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Alarm Data Model Concepts . . . . . . . . . . . . . . . . . . 5
3.1. Alarm Definition . . . . . . . . . . . . . . . . . . . . 5
3.2. Alarm Type . . . . . . . . . . . . . . . . . . . . . . . 6
3.3. Identifying the Alarming Resource . . . . . . . . . . . . 8
3.4. Identifying Alarm Instances . . . . . . . . . . . . . . . 9
3.5. Alarm Lifecycle . . . . . . . . . . . . . . . . . . . . . 9
3.5.1. Resource Alarm Lifecycle . . . . . . . . . . . . . . 10
3.5.2. Operator Alarm Lifecycle . . . . . . . . . . . . . . 11
3.5.3. Administrative Alarm Lifecycle . . . . . . . . . . . 11
3.6. Root Cause, Impacted Resources, and Related Alarms . . . 11
3.7. Alarm Shelving . . . . . . . . . . . . . . . . . . . . . 13
3.8. Alarm Profiles . . . . . . . . . . . . . . . . . . . . . 13
4. Alarm Data Model . . . . . . . . . . . . . . . . . . . . . . 13
4.1. Alarm Control . . . . . . . . . . . . . . . . . . . . . . 15
4.1.1. Alarm Shelving . . . . . . . . . . . . . . . . . . . 15
4.2. Alarm Inventory . . . . . . . . . . . . . . . . . . . . . 16
4.3. Alarm Summary . . . . . . . . . . . . . . . . . . . . . . 16
4.4. The Alarm List . . . . . . . . . . . . . . . . . . . . . 17
4.5. The Shelved-Alarm List . . . . . . . . . . . . . . . . . 19
4.6. Alarm Profiles . . . . . . . . . . . . . . . . . . . . . 19
4.7. Operations . . . . . . . . . . . . . . . . . . . . . . . 20
4.8. Notifications . . . . . . . . . . . . . . . . . . . . . . 20
5. Relationship to the ietf-hardware YANG Module . . . . . . . . 20
6. Alarm YANG Module . . . . . . . . . . . . . . . . . . . . . . 21
7. The X.733 Mapping Module . . . . . . . . . . . . . . . . . . 53
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 65
9. Security Considerations . . . . . . . . . . . . . . . . . . . 65
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 67
10.1. Normative References . . . . . . . . . . . . . . . . . . 67
10.2. Informative References . . . . . . . . . . . . . . . . . 68
Appendix A. Vendor-Specific Alarm Types Example . . . . . . . . 70
Appendix B. Alarm Inventory Example . . . . . . . . . . . . . . 71
Appendix C. Alarm List Example . . . . . . . . . . . . . . . . . 71
Appendix D. Alarm Shelving Example . . . . . . . . . . . . . . . 73
Appendix E. X.733 Mapping Example . . . . . . . . . . . . . . . 74
Appendix F. Relationship to Other Alarm Standards . . . . . . . 74
F.1. Definition of "Alarm" . . . . . . . . . . . . . . . . . . 74
F.2. Data Model . . . . . . . . . . . . . . . . . . . . . . . 76
F.2.1. X.733 . . . . . . . . . . . . . . . . . . . . . . . . 76
F.2.2. The Alarm MIB (RFC 3877) . . . . . . . . . . . . . . 77
F.2.3. 3GPP Alarm IRP . . . . . . . . . . . . . . . . . . . 77
F.2.4. G.7710 . . . . . . . . . . . . . . . . . . . . . . . 78
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RFC 8632 A YANG Data Model for Alarm Management September 2019
Appendix G. Alarm-Usability Requirements . . . . . . . . . . . . 78
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 82
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 82
1. Introduction
This document defines a YANG module [RFC7950] for alarm management.
The purpose is to define a standardized alarm interface for network
devices that can be easily integrated into management applications.
The model is also applicable as a northbound alarm interface in the
management applications.
Alarm monitoring is a fundamental part of monitoring the network.
Raw alarms from devices do not always tell the status of the network
services or necessarily point to the root cause. However, being able
to feed alarms to the alarm-management application in a standardized
format is a starting point for performing higher-level network
assurance tasks.
The design of the module is based on experience from using and
implementing available alarm standards from ITU [X.733], 3GPP
[ALARMIRP], and ANSI [ISA182].
1.1. Terminology and Notation
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 following terms are defined in [RFC7950]:
o action
o client
o data tree
o server
The following terms are used within this document:
Alarm (the general concept): An alarm signifies an undesirable state
in a resource that requires corrective action.
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Fault: A fault is the underlying cause of an undesired behavior.
There is no trivial one-to-one mapping between faults and alarms.
One fault may result in several alarms in case the system lacks
root-cause and correlation capabilities. An alarm might not have
an underlying fault as a cause. For example, imagine a bad Mean
Opinion Score (MOS) alarm from a Voice over IP (VOIP) probe and
the cause being non-optimal QoS configuration.
Alarm Type: An alarm type identifies a possible unique alarm state
for a resource. Alarm types are names to identify the state like
"link-alarm", "jitter-violation", and "high-disk-utilization".
Resource: A fine-grained identification of the alarming resource,
for example, an interface and a process.
Alarm Instance: The alarm state for a specific resource and alarm
type, for example, ("GigabitEthernet0/15", "link-alarm"). An
entry in the alarm list.
Cleared Alarm: A cleared alarm is an alarm where the system
considers the undesired state to be cleared. Operators cannot
clear alarms; clearance is managed by the system. For example, a
"linkUp" notification can be considered a clear condition for a
"linkDown" state.
Closed Alarm: Operators can close alarms irrespective of the alarm
being cleared or not. A closed alarm indicates that the alarm
does not need attention because either the corrective action has
been taken or it can be ignored for other reasons.
Alarm Inventory: A list of all possible alarm types on a system.
Alarm Shelving: Blocking alarms according to specific criteria.
Corrective Action: An action taken by an operator or automation
routine in order to minimize the impact of the alarm or resolve
the root cause.
Management System: The alarm-management application that consumes
the alarms, i.e., acts as a client.
System: The system that implements this YANG module, i.e., acts as a
server. This corresponds to a network device or a management
application that provides a northbound alarm interface.
Tree diagrams used in this document follow the notation defined in
[RFC8340].
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2. Objectives
The objectives for the design of the alarm data model are:
o Users find it simple to use. If a system supports this module, it
shall be straightforward to integrate it into a YANG-based alarm
manager.
o Alarms are viewed as states on resources and not as discrete
notifications.
o A precise definition of "alarm" is provided in order to exclude
general events that should not be forwarded as alarm
notifications.
o Precise identification of alarm types and alarm instances is
provided.
o A management system should be able to pull all available alarm
types from a system, i.e., read the alarm inventory from a system.
This makes it possible to prepare alarm operators with
corresponding alarm instructions.
o Alarm-usability requirements are addressed; see Appendix G. While
IETF and telecom standards have addressed alarms mostly from a
protocol perspective, the process industry has published several
relevant standards addressing requirements for a useful alarm
interface; see [EEMUA] and [ISA182]. This document defines
usability requirements as well as a YANG data model.
o Mapping to [X.733], which is a requirement for some alarm systems,
is achievable. Still, keep some of the X.733 concepts out of the
core model in order to make the model small and easy to
understand.
3. Alarm Data Model Concepts
This section defines the fundamental concepts behind the data model.
This section is rooted in the works of Vallin et. al [ALARMSEM].
3.1. Alarm Definition
An alarm signifies an undesirable state in a resource that requires
corrective action.
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There are two main things to remember from this definition:
1. It focuses on leaving out events and logging information in
general. Alarms should only be used for undesired states that
require action.
2. It also focuses on alarms as a state on a resource, not the
notifications that report the state changes.
See Appendix F for information on how this definition relates to
other alarm standards.
3.2. Alarm Type
This document defines an alarm type with an alarm-type id and an
alarm-type qualifier.
The alarm-type id is modeled as a YANG identity. With YANG
identities, new alarm types can be defined in a distributed fashion.
YANG identities are hierarchical, which means that a hierarchy of
alarm types can be defined.
Standards and vendors should define their own alarm-type identities
based on this definition.
The use of YANG identities means that all possible alarms are
identified at design time. This explicit declaration of alarm types
makes it easier to allow for alarm qualification reviews and
preparation of alarm actions and documentation.
There are occasions where the alarm types are not known at design
time. An example is a system with digital inputs that allows users
to connect detectors, such as smoke detectors, to the inputs. In
this case, it is a configuration action that says certain connectors
are fire alarms, for example.
In order to allow for dynamic addition of alarm types, the alarm data
model permits further qualification of the identity-based alarm type
using a string. A potential drawback of this is that there is a
significant risk that alarm operators will receive alarm types as a
surprise. They do not know how to resolve the problem since a
defined alarm procedure does not necessarily exist. To avoid this
risk, the system MUST publish all possible alarm types in the alarm
inventory; see Section 4.2.
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A vendor or standards organization can define their own alarm-type
hierarchy. The example below shows a hierarchy based on X.733 event
types:
import ietf-alarms {
prefix al;
}
identity vendor-alarms {
base al:alarm-type;
}
identity communications-alarm {
base vendor-alarms;
}
identity link-alarm {
base communications-alarm;
}
Alarm types can be abstract. An abstract alarm type is used as a
base for defining hierarchical alarm types. Concrete alarm types are
used for alarm states and appear in the alarm inventory. There are
two kinds of concrete alarm types:
1. The last subordinate identity in the "alarm-type-id" hierarchy is
concrete, for example, "alarm-identity.environmental-
alarm.smoke". In this example, "alarm-identity" and
"environmental-alarm" are abstract YANG identities, whereas
"smoke" is a concrete YANG identity.
2. The YANG identity hierarchy is abstract, and the concrete alarm
type is defined by the dynamic alarm-qualifier string, for
example, "alarm-identity.environmental-alarm.external-detector"
with alarm-type-qualifier "smoke".
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For example:
// Alternative 1: concrete alarm type identity
import ietf-alarms {
prefix al;
}
identity environmental-alarm {
base al:alarm-type;
description "Abstract alarm type";
}
identity smoke {
base environmental-alarm;
description "Concrete alarm type";
}
// Alternative 2: concrete alarm type qualifier
import ietf-alarms {
prefix al;
}
identity environmental-alarm {
base al:alarm-type;
description "Abstract alarm type";
}
identity external-detector {
base environmental-alarm;
description
"Abstract alarm type; a runtime configuration
procedure sets the type of alarm detected. This will
be reported in the alarm-type-qualifier.";
}
A server SHOULD strive to minimize the number of dynamically defined
alarm types.
3.3. Identifying the Alarming Resource
It is of vital importance to be able to refer to the alarming
resource. This reference must be as fine-grained as possible. If
the alarming resource exists in the data tree, an instance-identifier
MUST be used with the full path to the object.
When the module is used in a controller/orchestrator/manager, the
original device resource identification can be modified to include
the device in the path. The details depend on how devices are
identified and are out of scope for this specification.
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Example:
The original device alarm might identify the resource as
"/dev:interfaces/dev:interface[dev:name='FastEthernet1/0']".
The resource identification in the manager could look something
like: "/mgr:devices/mgr:device[mgr:name='xyz123']/dev:interfaces/
dev:interface[dev:name='FastEthernet1/0']"
This module also allows for alternate naming of the alarming resource
if it is not available in the data tree.
3.4. Identifying Alarm Instances
A primary goal of the alarm data model is to remove any ambiguity in
how alarm notifications are mapped to an update of an alarm instance.
The X.733 [X.733] and 3GPP [ALARMIRP] documents were not clear on
this point. This alarm data model states that the tuple (resource,
alarm-type identifier, and alarm-type qualifier) corresponds to a
single alarm instance. This means that alarm notifications for the
same resource and same alarm type are matched to update the same
alarm instance. These three leafs are therefore used as the key in
the alarm list:
list alarm {
key "resource alarm-type-id alarm-type-qualifier";
...
}
3.5. Alarm Lifecycle
The alarm model clearly separates the resource alarm lifecycle from
the operator and administrative lifecycles of an alarm.
o resource alarm lifecycle: the alarm instrumentation that controls
alarm raise, clearance, and severity changes.
o operator alarm lifecycle: operators acting upon alarms with
actions like acknowledging and closing. Closing an alarm implies
that the operator considers the corrective action performed.
Operators can also shelve (block/filter) alarms in order to avoid
nuisance alarms.
o administrative alarm lifecycle: purging (deleting) unwanted alarms
and compressing the alarm status-change list. This module exposes
operations to manage the administrative lifecycle. The server may
also perform these operations based on other policies, but how
that is done is out of scope for this document.
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A server SHOULD describe how long it retains cleared/closed alarms
until they are manually purged or if it has an automatic removal
policy. How this is done is outside the scope of this document.
3.5.1. Resource Alarm Lifecycle
From a resource perspective, an alarm can, for example, have the
following lifecycle: raise, change severity, change severity, clear,
being raised again, etc. All of these status changes can have
different alarm texts generated by the instrumentation. Two
important things to note:
1. Alarms are not deleted when they are cleared. Deleting alarms is
an administrative process. The "ietf-alarms" YANG module defines
an action "purge-alarms" that deletes alarms.
2. Alarms are not cleared by operators; only the underlying
instrumentation can clear an alarm. Operators can close alarms.
The YANG tree representation below illustrates the resource-oriented
lifecycle:
+--ro alarm* [resource alarm-type-id alarm-type-qualifier]
...
+--ro is-cleared boolean
+--ro last-raised yang:date-and-time
+--ro last-changed yang:date-and-time
+--ro perceived-severity severity
+--ro alarm-text alarm-text
+--ro status-change* [time] {alarm-history}?
+--ro time yang:date-and-time
+--ro perceived-severity severity-with-clear
+--ro alarm-text alarm-text
For every status change from the resource perspective, a row is added
to the "status-change" list, if the server implements the feature
"alarm-history". The feature "alarm-history" is optional to
implement, since keeping the alarm history may have an impact on the
server's memory resources.
The last status values are also represented as leafs for the alarm.
Note well that the alarm severity does not include "cleared"; alarm
clearance is a boolean flag.
Therefore, an alarm can look like this: (("GigabitEthernet0/25",
"link-alarm",""), false, 2018-04-08T08:20:10.00Z,
2018-04-08T08:20:10.00Z, major, "Interface GigabitEthernet0/25
down").
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3.5.2. Operator Alarm Lifecycle
Operators can act upon alarms using the set-operator-state action:
+--ro alarm* [resource alarm-type-id alarm-type-qualifier]
...
+--ro operator-state-change* [time] {operator-actions}?
| +--ro time yang:date-and-time
| +--ro operator string
| +--ro state operator-state
| +--ro text? string
+---x set-operator-state {operator-actions}?
+---w input
+---w state writable-operator-state
+---w text? string
The operator state for an alarm can be "none", "ack", "shelved", and
"closed". Alarm deletion (using the action "purge-alarms") can use
this state as a criterion. For example, a closed alarm is an alarm
where the operator has performed any required corrective actions.
Closed alarms are good candidates for being purged.
3.5.3. Administrative Alarm Lifecycle
Deleting alarms from the alarm list is considered an administrative
action. This is supported by the "purge-alarms" action. The "purge-
alarms" action takes a filter as input. The filter selects alarms
based on the operator and resource alarm lifecycle such as "all
closed cleared alarms older than a time specification". The server
may also perform these operations based on other policies, but how
that is done is out of scope for this document.
Purged alarms are removed from the alarm list. Note well that if the
alarm resource state changes after a purge, the alarm will reappear
in the alarm list.
Alarms can be compressed. Compressing an alarm deletes all entries
in the alarm's "status-change" list except for the last status
change. A client can perform this using the "compress-alarms"
action. The server may also perform these operations based on other
policies, but how that is done is out of scope for this document.
3.6. Root Cause, Impacted Resources, and Related Alarms
The alarm data model does not mandate any requirements for the system
to support alarm correlation or root-cause and service-impact
analysis. However, if such features are supported, this section
describes how the results of such analysis are represented in the
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data model. These parts of the model are optional. The module
supports three scenarios:
Root-cause analysis: An alarm can indicate candidate root-cause
resources, for example, a database issue alarm referring to a
full-disk partition.
Service-impact analysis: An alarm can refer to potential impacted
resources, for example, an interface alarm referring to impacted
network services.
Alarm correlation: Dependencies between alarms; several alarms can
be grouped as relating to each other, for example, a streaming
media alarm relating to a high-jitter alarm.
Different systems have varying degrees of alarm correlation and
analysis capabilities, and the intent of the alarm data model is to
enable any capability, including none.
The general principle of this alarm data model is to limit the amount
of alarms. In many cases, several resources are affected for a given
underlying problem. A full disk will of course impact databases and
applications as well. The recommendation is to have a single alarm
for the underlying problem and list the affected resources in the
alarm rather than having separate alarms for each resource.
The alarm has one leaf-list to identify a possible "impacted-
resource" and a leaf-list to identify a possible "root-cause-
resource". These serve as hints only. It is up to the client
application to use this information to present the overall status.
Using the disk-full example, a good alarm would be to use the hard-
disk partition as the alarming resource and add the database and
applications into the "impacted-resource" leaf-list.
A system should always strive to identify the resource that can be
acted upon as the "resource" leaf. The "impacted-resource" leaf-list
shall be used to identify any side effects of the alarm. The
impacted resources cannot be acted upon to fix the problem. The disk
full example above illustrates the principle; you cannot fix the
underlying issue by database operations. However, you need to pay
attention to the database to perform any operations that limit the
impact of the problem.
On some occasions, the system might not be capable of detecting the
root cause, the resource that can be acted upon. The instrumentation
in this case only monitors the side effect and raises an alarm to
indicate a situation requiring attention. The instrumentation still
might identify possible candidates for the root-cause resource. In
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RFC 8632 A YANG Data Model for Alarm Management September 2019
this case, the "root-cause-resource" leaf-list can be used to
indicate the candidate root-cause resources. An example of this kind
of alarm might be an active test tool that detects a Service Level
Agreement (SLA) violation on a VPN connection and identifies the
devices along the chain as candidate root causes.
The alarm data model also supports a way to associate different
alarms with each other using the "related-alarm" list. This list
enables the server to inform the client that certain alarms are
related to other alarms.
Note well that this module does not prescribe any dependencies or
preference between the above alarm correlation mechanisms. Different
systems have different capabilities, and the above described
mechanisms are available to support the instrumentation features.
3.7. Alarm Shelving
Alarm shelving is an important function in order for alarm-management
applications and operators to stop superfluous alarms. A shelved
alarm implies that any alarms fulfilling these criteria are ignored
(blocked/filtered). Shelved alarms appear in a dedicated shelved-
alarm list; thus, they can be filtered out so that the main alarm
list only contains entries of interest. Shelved alarms do not
generate notifications, but the shelved-alarm list is updated with
any alarm-state changes.
Alarm shelving is optional to implement, since matching alarms
against shelf criteria may have an impact on the server's processing
resources.
3.8. Alarm Profiles
Alarm profiles are used to configure further information to an alarm
type. This module supports configuring severity levels overriding
the system-default levels. This corresponds to the Alarm Severity
Assignment Profile (ASAP) functionality in M.3100 [M.3100] and M.3160
[M.3160]. Other standard or enterprise modules can augment this list
with further alarm-type information.
4. Alarm Data Model
The fundamental parts of the data model are the "alarm-list" with
associated notifications and the "alarm-inventory" list of all
possible alarm types. These MUST be implemented by a system. The
rest of the data model is made conditional with these YANG features:
"operator-actions", "alarm-shelving", "alarm-history", "alarm-
summary", "alarm-profile", and "severity-assignment".
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The data model has the following overall structure:
+--rw control
| +--rw max-alarm-status-changes? union
| +--rw notify-status-changes? enumeration
| +--rw notify-severity-level? severity
| +--rw alarm-shelving {alarm-shelving}?
| ...
+--ro alarm-inventory
| +--ro alarm-type* [alarm-type-id alarm-type-qualifier]
| ...
+--ro summary {alarm-summary}?
| +--ro alarm-summary* [severity]
| | ...
| +--ro shelves-active? empty {alarm-shelving}?
+--ro alarm-list
| +--ro number-of-alarms? yang:gauge32
| +--ro last-changed? yang:date-and-time
| +--ro alarm* [resource alarm-type-id alarm-type-qualifier]
| | ...
| +---x purge-alarms
| | ...
| +---x compress-alarms {alarm-history}?
| ...
+--ro shelved-alarms {alarm-shelving}?
| +--ro number-of-shelved-alarms? yang:gauge32
| +--ro shelved-alarms-last-changed? yang:date-and-time
| +--ro shelved-alarm*
| | [resource alarm-type-id alarm-type-qualifier]
| | ...
| +---x purge-shelved-alarms
| | ...
| +---x compress-shelved-alarms {alarm-history}?
| ...
+--rw alarm-profile*
[alarm-type-id alarm-type-qualifier-match resource]
{alarm-profile}?
+--rw alarm-type-id alarm-type-id
+--rw alarm-type-qualifier-match string
+--rw resource resource-match
+--rw description string
+--rw alarm-severity-assignment-profile
{severity-assignment}?
...
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4.1. Alarm Control
The "/alarms/control/notify-status-changes" leaf controls whether
notifications are sent for all state changes, only raise and clear,
or only notifications more severe than a configured level. This
feature, in combination with alarm shelving, corresponds to the ITU
Alarm Report Control functionality; see Appendix F.2.4.
Every alarm has a list of status changes. The length of this list is
controlled by "/alarms/control/max-alarm-status-changes". When the
list is full and a new entry created, the oldest entry is removed.
4.1.1. Alarm Shelving
The shelving control tree is shown below:
+--rw control
+--rw alarm-shelving {alarm-shelving}?
+--rw shelf* [name]
+--rw name string
+--rw resource* resource-match
+--rw alarm-type*
| [alarm-type-id alarm-type-qualifier-match]
| +--rw alarm-type-id alarm-type-id
| +--rw alarm-type-qualifier-match string
+--rw description? string
Shelved alarms are shown in a dedicated shelved-alarm list. Matching
alarms MUST appear in the "/alarms/shelved-alarms/shelved-alarm"
list, and non-matching alarms MUST appear in the "/alarms/alarm-list/
alarm" list. The server does not send any notifications for shelved
alarms.
Shelving and unshelving can only be performed by editing the shelf
configuration. It cannot be performed on individual alarms. The
server will add an operator state indicating that the alarm was
shelved/unshelved.
A leaf, "/alarms/summary/shelves-active", in the alarm summary
indicates if there are shelved alarms.
A system can select not to support the shelving feature.
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RFC 8632 A YANG Data Model for Alarm Management September 2019
4.2. Alarm Inventory
The alarm inventory represents all possible alarm types that may
occur in the system. A management system may use this to build alarm
procedures. The alarm inventory is relevant for the following
reasons:
The system might not implement all defined alarm type identities,
and some alarm identities are abstract.
The system has configured dynamic alarm types using the alarm
qualifier. The inventory makes it possible for the management
system to discover these.
Note that the mechanism whereby dynamic alarm types are added using
the alarm-type qualifier MUST populate this list.
The optional leaf-list "resource" in the alarm inventory enables the
system to publish for which resources a given alarm type may appear.
A server MUST implement the alarm inventory in order to enable
controlled alarm procedures in the client.
A server implementer may want to document the alarm inventory for
offline processing by clients. The file format defined in
[YANG-INSTANCE] can be used for this purpose.
The alarm inventory tree is shown below:
+--ro alarm-inventory
+--ro alarm-type* [alarm-type-id alarm-type-qualifier]
+--ro alarm-type-id alarm-type-id
+--ro alarm-type-qualifier alarm-type-qualifier
+--ro resource* resource-match
+--ro will-clear boolean
+--ro severity-level* severity
+--ro description string
4.3. Alarm Summary
The alarm summary list summarizes alarms per severity: how many
cleared, cleared and closed, and closed. It also gives an indication
if there are shelved alarms.
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The alarm summary tree is shown below:
+--ro summary {alarm-summary}?
+--ro alarm-summary* [severity]
| +--ro severity severity
| +--ro total? yang:gauge32
| +--ro not-cleared? yang:gauge32
| +--ro cleared? yang:gauge32
| +--ro cleared-not-closed? yang:gauge32
| | {operator-actions}?
| +--ro cleared-closed? yang:gauge32
| | {operator-actions}?
| +--ro not-cleared-closed? yang:gauge32
| | {operator-actions}?
| +--ro not-cleared-not-closed? yang:gauge32
| {operator-actions}?
+--ro shelves-active? empty {alarm-shelving}?
4.4. The Alarm List
The alarm list, "/alarms/alarm-list", is a function from the tuple
(resource, alarm type, alarm-type qualifier) to the current composite
alarm state. The composite state includes states for the resource
alarm lifecycle such as severity, clearance flag, and operator states
such as acknowledged. This means that for a given resource and alarm
type, the alarm list shows the current states of the alarm such as
acknowledged and cleared.
+--ro alarm-list
+--ro number-of-alarms? yang:gauge32
+--ro last-changed? yang:date-and-time
+--ro alarm* [resource alarm-type-id alarm-type-qualifier]
| +--ro resource resource
| +--ro alarm-type-id alarm-type-id
| +--ro alarm-type-qualifier alarm-type-qualifier
| +--ro alt-resource* resource
| +--ro related-alarm*
| | [resource alarm-type-id alarm-type-qualifier]
| | {alarm-correlation}?
| | +--ro resource
| | | -> /alarms/alarm-list/alarm/resource
| | +--ro alarm-type-id leafref
| | +--ro alarm-type-qualifier leafref
| +--ro impacted-resource* resource
| | {service-impact-analysis}?
| +--ro root-cause-resource* resource
| | {root-cause-analysis}?
| +--ro time-created yang:date-and-time
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| +--ro is-cleared boolean
| +--ro last-raised yang:date-and-time
| +--ro last-changed yang:date-and-time
| +--ro perceived-severity severity
| +--ro alarm-text alarm-text
| +--ro status-change* [time] {alarm-history}?
| | +--ro time yang:date-and-time
| | +--ro perceived-severity severity-with-clear
| | +--ro alarm-text alarm-text
| +--ro operator-state-change* [time] {operator-actions}?
| | +--ro time yang:date-and-time
| | +--ro operator string
| | +--ro state operator-state
| | +--ro text? string
| +---x set-operator-state {operator-actions}?
| | +---w input
| | +---w state writable-operator-state
| | +---w text? string
| +---n operator-action {operator-actions}?
| +-- time yang:date-and-time
| +-- operator string
| +-- state operator-state
| +-- text? string
+---x purge-alarms
| +---w input
| | +---w alarm-clearance-status enumeration
| | +---w older-than!
| | | +---w (age-spec)?
| | | +--:(seconds)
| | | | +---w seconds? uint16
| | | +--:(minutes)
| | | | +---w minutes? uint16
| | | +--:(hours)
| | | | +---w hours? uint16
| | | +--:(days)
| | | | +---w days? uint16
| | | +--:(weeks)
| | | +---w weeks? uint16
| | +---w severity!
| | | +---w (sev-spec)?
| | | +--:(below)
| | | | +---w below? severity
| | | +--:(is)
| | | | +---w is? severity
| | | +--:(above)
| | | +---w above? severity
| | +---w operator-state-filter! {operator-actions}?
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| | +---w state? operator-state
| | +---w user? string
| +--ro output
| +--ro purged-alarms? uint32
+---x compress-alarms {alarm-history}?
+---w input
| +---w resource? resource-match
| +---w alarm-type-id?
| | -> /alarms/alarm-list/alarm/alarm-type-id
| +---w alarm-type-qualifier? leafref
+--ro output
+--ro compressed-alarms? uint32
Every alarm has three important states: the resource clearance state
"is-cleared", the severity "perceived-severity", and the operator
state available in the operator-state change list.
In order to see the alarm history, the resource state changes are
available in the "status-change" list, and the operator history is
available in the "operator-state-change" list.
4.5. The Shelved-Alarm List
The shelved-alarm list has the same structure as the alarm list
above. It shows all the alarms that match the shelving criteria
"/alarms/control/alarm-shelving".
4.6. Alarm Profiles
Alarm profiles, "/alarms/alarm-profile", is a list of configurable
alarm types. The list supports configurable alarm severity levels in
the container "alarm-severity-assignment-profile". If an alarm
matches the configured alarm type, it MUST use the configured
severity level(s) instead of the system default. This configuration
MUST also be represented in the alarm inventory.
+--rw alarm-profile*
[alarm-type-id alarm-type-qualifier-match resource]
{alarm-profile}?
+--rw alarm-type-id alarm-type-id
+--rw alarm-type-qualifier-match string
+--rw resource resource-match
+--rw description string
+--rw alarm-severity-assignment-profile
{severity-assignment}?
+--rw severity-level* severity
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4.7. Operations
The alarm data model supports the following actions to manage the
alarms:
"/alarms/alarm-list/purge-alarms": Delete alarms from the "alarm-
list" according to specific criteria, for example, all cleared
alarms older than a specific date.
"/alarms/alarm-list/compress-alarms": Compress the "status-change"
list for the alarms.
"/alarms/alarm-list/alarm/set-operator-state": Change the operator
state for an alarm. For example, an alarm can be acknowledged by
setting the operator state to "ack".
"/alarms/shelved-alarm-list/purge-shelved-alarms": Delete alarms
from the "shelved-alarm-list" according to specific criteria, for
example, all alarms older than a specific date.
"/alarms/shelved-alarm-list/compress-shelved-alarms": Compress the
"status-change" list for the alarms.
4.8. Notifications
The alarm data model supports a general notification to report alarm-
state changes. It carries all relevant parameters for the alarm-
management application.
There is also a notification to report that an operator changed the
operator state on an alarm, like acknowledged.
If the alarm inventory is changed, for example, a new card type is
inserted, a notification will tell the management application that
new alarm types are available.
5. Relationship to the ietf-hardware YANG Module
RFC 8348 [RFC8348] defines the "ietf-hardware" YANG data model for
the management of hardware. The "alarm-state" in RFC 8348 is a
summary of the alarm severity levels that may be active on the
specific hardware component. It does not say anything about how
alarms are reported, and it doesn't provide any details of the
alarms.
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The mapping between the alarm YANG data model, prefix "al", and the
"alarm-state" in RFC 8348, prefix "hw", is as follows:
"al:resource": Corresponds to an entry in the list
"/hw:hardware/hw:component/".
"al:is-cleared": No bit set in "/hw:hardware/hw:component/hw:state/
hw:alarm-state".
"al:perceived-severity": Corresponding bit set in
"/hw:hardware/hw:component/hw:state/hw:alarm-state".
"al:operator-state-change/al:state": If the alarm is acknowledged by
the operator, the bit "hw:under-repair" is set in
"/hw:hardware/hw:component/hw:state/hw:alarm-state".
6. Alarm YANG Module
This YANG module references [RFC6991] and [XSD-TYPES].
<CODE BEGINS> file "ietf-alarms@2019-09-11.yang"
module ietf-alarms {
yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang:ietf-alarms";
prefix al;
import ietf-yang-types {
prefix yang;
reference
"RFC 6991: Common YANG Data Types.";
}
organization
"IETF CCAMP Working Group";
contact
"WG Web: <https://trac.ietf.org/trac/ccamp>
WG List: <mailto:ccamp@ietf.org>
Editor: Stefan Vallin
<mailto:stefan@wallan.se>
Editor: Martin Bjorklund
<mailto:mbj@tail-f.com>";
description
"This module defines an interface for managing alarms. Main
inputs to the module design are the 3GPP Alarm Integration
Reference Point (IRP), ITU-T X.733, and ANSI/ISA-18.2 alarm
standards.
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Main features of this module include:
* Alarm list:
A list of all alarms. Cleared alarms stay in
the list until explicitly purged.
* Operator actions on alarms:
Acknowledging and closing alarms.
* Administrative actions on alarms:
Purging alarms from the list according to specific
criteria.
* Alarm inventory:
A management application can read all
alarm types implemented by the system.
* Alarm shelving:
Shelving (blocking) alarms according
to specific criteria.
* Alarm profiles:
A management system can attach further
information to alarm types, for example,
overriding system-default severity
levels.
This module uses a stateful view on alarms. An alarm is a state
for a specific resource (note that an alarm is not a
notification). An alarm type is a possible alarm state for a
resource. For example, the tuple:
('link-alarm', 'GigabitEthernet0/25')
is an alarm of type 'link-alarm' on the resource
'GigabitEthernet0/25'.
Alarm types are identified using YANG identities and an optional
string-based qualifier. The string-based qualifier allows for
dynamic extension of the statically defined alarm types. Alarm
types identify a possible alarm state and not the individual
notifications. For example, the traditional 'link-down' and
'link-up' notifications are two notifications referring to the
same alarm type 'link-alarm'.
With this design, there is no ambiguity about how alarm and
alarm clear correlation should be performed; notifications that
report the same resource and alarm type are considered updates
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of the same alarm, e.g., clearing an active alarm or changing
the severity of an alarm. The instrumentation can update the
severity and alarm text on an existing alarm. The above alarm
example can therefore look like the following:
(('link-alarm', 'GigabitEthernet0/25'),
warning,
'interface down while interface admin state is up')
There is a clear separation between updates on the alarm from
the underlying resource, like clear, and updates from an
operator, like acknowledging or closing an alarm:
(('link-alarm', 'GigabitEthernet0/25'),
warning,
'interface down while interface admin state is up',
cleared,
closed)
Administrative actions like removing closed alarms older than a
given time is supported.
This YANG module does not define how the underlying
instrumentation detects and clears the specific alarms. That
belongs to the Standards Development Organization (SDO) or
enterprise that owns that specific technology.
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
(https://trustee.ietf.org/license-info).
This version of this YANG module is part of RFC 8632; see
the RFC itself for full legal notices.";
revision 2019-09-11 {
description
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RFC 8632 A YANG Data Model for Alarm Management September 2019
"Initial revision.";
reference
"RFC 8632: A YANG Data Model for Alarm Management";
}
/*
* Features
*/
feature operator-actions {
description
"This feature indicates that the system supports operator
states on alarms.";
}
feature alarm-shelving {
description
"This feature indicates that the system supports shelving
(blocking) alarms.
Alarm shelving may have an impact on server processing
resources in order to match alarms against shelf
criteria.";
}
feature alarm-history {
description
"This feature indicates that the server maintains a history
of state changes for each alarm. For example, if an alarm
toggles between cleared and active 10 times, these state
changes are present in a separate list in the alarm.
Keeping the alarm history may have an impact on server
memory resources.";
}
feature alarm-summary {
description
"This feature indicates that the server summarizes the number
of alarms per severity and operator state.";
}
feature alarm-profile {
description
"The system enables clients to configure further information
to each alarm type.";
}
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feature severity-assignment {
description
"The system supports configurable alarm severity levels.";
reference
"ITU-T Recommendation M.3100:
Generic network information model
ITU-T Recommendation M.3160:
Generic, protocol-neutral management information model";
}
feature root-cause-analysis {
description
"The system supports identifying candidate root-cause
resources for an alarm, for example, a disk partition
root cause for a logger failure alarm.";
}
feature service-impact-analysis {
description
"The system supports identifying candidate-impacted
resources for an alarm, for example, an interface state change
resulting in a link alarm, which can refer to a link as being
impacted.";
}
feature alarm-correlation {
description
"The system supports correlating/grouping alarms
that belong together.";
}
/*
* Identities
*/
identity alarm-type-id {
description
"Base identity for alarm types. A unique identification of
the alarm, not including the resource. Different resources
can share alarm types. If the resource reports the same
alarm type, it is considered to be the same alarm. The alarm
type is a simplification of the different X.733 and 3GPP Alarm
IRP correlation mechanisms, and it allows for
hierarchical extensions.
A string-based qualifier can be used in addition to the
identity in order to have different alarm types based on
information not known at design time, such as values in
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textual SNMP Notification varbinds.
Standards and vendors can define sub-identities to clearly
identify specific alarm types.
This identity is abstract and MUST NOT be used for alarms.";
}
/*
* Common types
*/
typedef resource {
type union {
type instance-identifier {
require-instance false;
}
type yang:object-identifier;
type string;
type yang:uuid;
}
description
"This is an identification of the alarming resource, such as an
interface. It should be as fine-grained as possible to both
guide the operator and guarantee uniqueness of the alarms.
If the alarming resource is modeled in YANG, this type will
be an instance-identifier.
If the resource is an SNMP object, the type will be an
'object-identifier'.
If the resource is anything else, for example, a distinguished
name or a Common Information Model (CIM) path, this type will
be a string.
If the alarming object is identified by a Universally Unique
Identifier (UUID), use the uuid type. Be cautious when using
this type, since a UUID is hard to use for an operator.
If the server supports several models, the precedence should
be in the order as given in the union definition.";
}
typedef resource-match {
type union {
type yang:xpath1.0;
type yang:object-identifier;
Vallin & Bjorklund Standards Track [Page 26]
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type string;
}
description
"This type is used to match resources of type 'resource'.
Since the type 'resource' is a union of different types, the
'resource-match' type is also a union of corresponding types.
If the type is given as an XPath 1.0 expression, a resource
of type 'instance-identifier' matches if the instance is part
of the node set that is the result of evaluating the XPath 1.0
expression. For example, the XPath 1.0 expression:
/ietf-interfaces:interfaces/ietf-interfaces:interface
[ietf-interfaces:type='ianaift:ethernetCsmacd']
would match the resource instance-identifier:
/if:interfaces/if:interface[if:name='eth1'],
assuming that the interface 'eth1' is of type
'ianaift:ethernetCsmacd'.
If the type is given as an object identifier, a resource of
type 'object-identifier' matches if the match object
identifier is a prefix of the resource's object identifier.
For example, the value:
1.3.6.1.2.1.2.2
would match the resource object identifier:
1.3.6.1.2.1.2.2.1.1.5
If the type is given as an UUID or a string, it is interpreted
as an XML Schema regular expression, which matches a resource
of type 'yang:uuid' or 'string' if the given regular
expression matches the resource string.
If the type is given as an XPath expression, it is evaluated
in the following XPath context:
o 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 a leaf of this type is encoded in XML, all namespace
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declarations in scope on the 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.
o The set of variable bindings is empty.
o The function library is the core function library, and
the functions are defined in Section 10 of RFC 7950.
o The context node is the root node in the data tree.";
reference
"XML Schema Part 2: Datatypes Second Edition,
World Wide Web Consortium Recommendation
REC-xmlschema-2-20041028";
}
typedef alarm-text {
type string;
description
"The string used to inform operators about the alarm. This
MUST contain enough information for an operator to be able to
understand the problem and how to resolve it. If this string
contains structure, this format should be clearly documented
for programs to be able to parse that information.";
}
typedef severity {
type enumeration {
enum indeterminate {
value 2;
description
"Indicates that the severity level could not be
determined. This level SHOULD be avoided.";
}
enum warning {
value 3;
description
"The 'warning' severity level indicates the detection of a
potential or impending service-affecting fault, before any
significant effects have been felt. Action should be
taken to further diagnose (if necessary) and correct the
problem in order to prevent it from becoming a more
serious service-affecting fault.";
}
enum minor {
value 4;
description
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"The 'minor' severity level indicates the existence of a
non-service-affecting fault condition and that corrective
action should be taken in order to prevent a more serious
(for example, service-affecting) fault. Such a severity
can be reported, for example, when the detected alarm
condition is not currently degrading the capacity of the
resource.";
}
enum major {
value 5;
description
"The 'major' severity level indicates that a service-
affecting condition has developed and an urgent corrective
action is required. Such a severity can be reported, for
example, when there is a severe degradation in the
capability of the resource and its full capability must be
restored.";
}
enum critical {
value 6;
description
"The 'critical' severity level indicates that a service-
affecting condition has occurred and an immediate
corrective action is required. Such a severity can be
reported, for example, when a resource becomes totally out
of service and its capability must be restored.";
}
}
description
"The severity level of the alarm. Note well that the value
'clear' is not included. Whether or not an alarm is cleared
is a separate boolean flag.";
reference
"ITU-T Recommendation X.733: Information Technology
- Open Systems Interconnection
- System Management: Alarm Reporting Function";
}
typedef severity-with-clear {
type union {
type enumeration {
enum cleared {
value 1;
description
"The alarm is cleared by the instrumentation.";
}
}
type severity;
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RFC 8632 A YANG Data Model for Alarm Management September 2019
}
description
"The severity level of the alarm including clear. This is used
only in notifications reporting state changes for an alarm.";
}
typedef writable-operator-state {
type enumeration {
enum none {
value 1;
description
"The alarm is not being taken care of.";
}
enum ack {
value 2;
description
"The alarm is being taken care of. Corrective action not
taken yet or has failed";
}
enum closed {
value 3;
description
"Corrective action taken successfully.";
}
}
description
"Operator states on an alarm. The 'closed' state indicates
that an operator considers the alarm being resolved. This is
separate from the alarm's 'is-cleared' leaf.";
}
typedef operator-state {
type union {
type writable-operator-state;
type enumeration {
enum shelved {
value 4;
description
"The alarm is shelved. Alarms in /alarms/shelved-alarms/
MUST be assigned this operator state by the server as
the last entry in the 'operator-state-change' list. The
text for that entry SHOULD include the shelf name.";
}
enum un-shelved {
value 5;
description
"The alarm is moved back to 'alarm-list' from a shelf.
Alarms that are moved from /alarms/shelved-alarms/ to
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RFC 8632 A YANG Data Model for Alarm Management September 2019
/alarms/alarm-list MUST be assigned this state by the
server as the last entry in the 'operator-state-change'
list. The text for that entry SHOULD include the shelf
name.";
}
}
}
description
"Operator states on an alarm. The 'closed' state indicates
that an operator considers the alarm being resolved. This is
separate from the alarm's 'is-cleared' leaf.";
}
/* Alarm type */
typedef alarm-type-id {
type identityref {
base alarm-type-id;
}
description
"Identifies an alarm type. The description of the alarm type
id MUST indicate whether or not the alarm type is abstract.
An abstract alarm type is used as a base for other alarm type
ids and will not be used as a value for an alarm or be present
in the alarm inventory.";
}
typedef alarm-type-qualifier {
type string;
description
"If an alarm type cannot be fully specified at design time by
'alarm-type-id', this string qualifier is used in addition to
fully define a unique alarm type.
The definition of alarm qualifiers is considered to be part of
the instrumentation and is out of scope for this module. An
empty string is used when this is part of a key.";
}
/*
* Groupings
*/
grouping common-alarm-parameters {
description
"Common parameters for an alarm.
This grouping is used both in the alarm list and in the
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RFC 8632 A YANG Data Model for Alarm Management September 2019
notification representing an alarm-state change.";
leaf resource {
type resource;
mandatory true;
description
"The alarming resource. See also 'alt-resource'. This could
be, for example, a reference to the alarming interface";
}
leaf alarm-type-id {
type alarm-type-id;
mandatory true;
description
"This leaf and the leaf 'alarm-type-qualifier' together
provide a unique identification of the alarm type.";
}
leaf alarm-type-qualifier {
type alarm-type-qualifier;
description
"This leaf is used when the 'alarm-type-id' leaf cannot
uniquely identify the alarm type. Normally, this is not the
case, and this leaf is the empty string.";
}
leaf-list alt-resource {
type resource;
description
"Used if the alarming resource is available over other
interfaces. This field can contain SNMP OIDs, CIM paths, or
3GPP distinguished names, for example.";
}
list related-alarm {
if-feature "alarm-correlation";
key "resource alarm-type-id alarm-type-qualifier";
description
"References to related alarms. Note that the related alarm
might have been purged from the alarm list.";
leaf resource {
type leafref {
path "/alarms/alarm-list/alarm/resource";
require-instance false;
}
description
"The alarming resource for the related alarm.";
}
leaf alarm-type-id {
type leafref {
path "/alarms/alarm-list/alarm"
+ "[resource=current()/../resource]"
+ "/alarm-type-id";
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require-instance false;
}
description
"The alarm type identifier for the related alarm.";
}
leaf alarm-type-qualifier {
type leafref {
path "/alarms/alarm-list/alarm"
+ "[resource=current()/../resource]"
+ "[alarm-type-id=current()/../alarm-type-id]"
+ "/alarm-type-qualifier";
require-instance false;
}
description
"The alarm qualifier for the related alarm.";
}
}
leaf-list impacted-resource {
if-feature "service-impact-analysis";
type resource;
description
"Resources that might be affected by this alarm. If the
system creates an alarm on a resource and also has a mapping
to other resources that might be impacted, these resources
can be listed in this leaf-list. In this way, the system
can create one alarm instead of several. For example, if an
interface has an alarm, the 'impacted-resource' can
reference the aggregated port channels.";
}
leaf-list root-cause-resource {
if-feature "root-cause-analysis";
type resource;
description
"Resources that are candidates for causing the alarm. If the
system has a mechanism to understand the candidate root
causes of an alarm, this leaf-list can be used to list the
root-cause candidate resources. In this way, the system can
create one alarm instead of several. An example might be a
logging system (alarm resource) that fails; the alarm can
reference the file system in the 'root-cause-resource'
leaf-list. Note that the intended use is not to also send
an alarm with the 'root-cause-resource' as an alarming
resource. The 'root-cause-resource' leaf-list is a hint and
should not also generate an alarm for the same problem.";
}
}
grouping alarm-state-change-parameters {
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description
"Parameters for an alarm-state change.
This grouping is used both in the alarm list's status-change
list and in the notification representing an alarm-state
change.";
leaf time {
type yang:date-and-time;
mandatory true;
description
"The time the status of the alarm changed. The value
represents the time the real alarm-state change appeared in
the resource and not when it was added to the alarm
list. The /alarm-list/alarm/last-changed MUST be set to the
same value.";
}
leaf perceived-severity {
type severity-with-clear;
mandatory true;
description
"The severity of the alarm as defined by X.733. Note that
this may not be the original severity since the alarm may
have changed severity.";
reference
"ITU-T Recommendation X.733: Information Technology
- Open Systems Interconnection
- System Management: Alarm Reporting Function";
}
leaf alarm-text {
type alarm-text;
mandatory true;
description
"A user-friendly text describing the alarm-state change.";
reference
"ITU-T Recommendation X.733: Information Technology
- Open Systems Interconnection
- System Management: Alarm Reporting Function";
}
}
grouping operator-parameters {
description
"This grouping defines parameters that can be changed by an
operator.";
leaf time {
type yang:date-and-time;
mandatory true;
description
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"Timestamp for operator action on the alarm.";
}
leaf operator {
type string;
mandatory true;
description
"The name of the operator that has acted on this alarm.";
}
leaf state {
type operator-state;
mandatory true;
description
"The operator's view of the alarm state.";
}
leaf text {
type string;
description
"Additional optional textual information provided by the
operator.";
}
}
grouping resource-alarm-parameters {
description
"Alarm parameters that originate from the resource view.";
leaf is-cleared {
type boolean;
mandatory true;
description
"Indicates the current clearance state of the alarm. An
alarm might toggle from active alarm to cleared alarm and
back to active again.";
}
leaf last-raised {
type yang:date-and-time;
mandatory true;
description
"An alarm may change severity level and toggle between
active and cleared during its lifetime. This leaf indicates
the last time it was raised ('is-cleared' = 'false').";
}
leaf last-changed {
type yang:date-and-time;
mandatory true;
description
"A timestamp when the 'status-change' or
'operator-state-change' list was last changed.";
}
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leaf perceived-severity {
type severity;
mandatory true;
description
"The last severity of the alarm.
If an alarm was raised with severity 'warning' but later
changed to 'major', this leaf will show 'major'.";
}
leaf alarm-text {
type alarm-text;
mandatory true;
description
"The last reported alarm text. This text should contain
information for an operator to be able to understand the
problem and how to resolve it.";
}
list status-change {
if-feature "alarm-history";
key "time";
min-elements 1;
description
"A list of status-change events for this alarm.
The entry with latest timestamp in this list MUST
correspond to the leafs 'is-cleared', 'perceived-severity',
and 'alarm-text' for the alarm.
This list is ordered according to the timestamps of alarm
state changes. The first item corresponds to the latest
state change.
The following state changes create an entry in this
list:
- changed severity (warning, minor, major, critical)
- clearance status; this also updates the 'is-cleared'
leaf
- alarm-text update";
uses alarm-state-change-parameters;
}
}
grouping filter-input {
description
"Grouping to specify a filter construct on alarm information.";
leaf alarm-clearance-status {
type enumeration {
enum any {
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description
"Ignore alarm-clearance status.";
}
enum cleared {
description
"Filter cleared alarms.";
}
enum not-cleared {
description
"Filter not-cleared alarms.";
}
}
mandatory true;
description
"The clearance status of the alarm.";
}
container older-than {
presence "Age specification";
description
"Matches the 'last-status-change' leaf in the alarm.";
choice age-spec {
description
"Filter using date and time age.";
case seconds {
leaf seconds {
type uint16;
description
"Age expressed in seconds.";
}
}
case minutes {
leaf minutes {
type uint16;
description
"Age expressed in minutes.";
}
}
case hours {
leaf hours {
type uint16;
description
"Age expressed in hours.";
}
}
case days {
leaf days {
type uint16;
description
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"Age expressed in days.";
}
}
case weeks {
leaf weeks {
type uint16;
description
"Age expressed in weeks.";
}
}
}
}
container severity {
presence "Severity filter";
choice sev-spec {
description
"Filter based on severity level.";
leaf below {
type severity;
description
"Severity less than this leaf.";
}
leaf is {
type severity;
description
"Severity level equal to this leaf.";
}
leaf above {
type severity;
description
"Severity level higher than this leaf.";
}
}
description
"Filter based on severity.";
}
container operator-state-filter {
if-feature "operator-actions";
presence "Operator state filter";
leaf state {
type operator-state;
description
"Filter on operator state.";
}
leaf user {
type string;
description
"Filter based on which operator.";
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}
description
"Filter based on operator state.";
}
}
/*
* The /alarms data tree
*/
container alarms {
description
"The top container for this module.";
container control {
description
"Configuration to control the alarm behavior.";
leaf max-alarm-status-changes {
type union {
type uint16;
type enumeration {
enum infinite {
description
"The status-change entries are accumulated
infinitely.";
}
}
}
default "32";
description
"The 'status-change' entries are kept in a circular list
per alarm. When this number is exceeded, the oldest
status change entry is automatically removed. If the
value is 'infinite', the status-change entries are
accumulated infinitely.";
}
leaf notify-status-changes {
type enumeration {
enum all-state-changes {
description
"Send notifications for all status changes.";
}
enum raise-and-clear {
description
"Send notifications only for raise, clear, and
re-raise. Notifications for severity-level changes or
alarm-text changes are not sent.";
}
enum severity-level {
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description
"Only send notifications for alarm-state changes
crossing the level specified in
'notify-severity-level'. Always send clear
notifications.";
}
}
must '. != "severity-level" or ../notify-severity-level' {
description
"When notify-status-changes is 'severity-level', a value
must be given for 'notify-severity-level'.";
}
default "all-state-changes";
description
"This leaf controls the notifications sent for alarm status
updates. There are three options:
1. Notifications are sent for all updates, severity-level
changes, and alarm-text changes.
2. Notifications are only sent for alarm raise and clear.
3. Notifications are sent for status changes equal to or
above the specified severity level. Clear
notifications shall always be sent. Notifications
shall also be sent for state changes that make an
alarm less severe than the specified level.
For example, in option 3, assume that the severity level
is set to major and that the alarm has the following state
changes:
[(Time, severity, clear)]:
[(T1, major, -), (T2, minor, -), (T3, warning, -),
(T4, minor, -), (T5, major, -), (T6, critical, -),
(T7, major. -), (T8, major, clear)]
In that case, notifications will be sent at times
T1, T2, T5, T6, T7, and T8.";
}
leaf notify-severity-level {
when '../notify-status-changes = "severity-level"';
type severity;
description
"Only send notifications for alarm-state changes crossing
the specified level. Always send clear notifications.";
}
container alarm-shelving {
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if-feature "alarm-shelving";
description
"The 'alarm-shelving/shelf' list is used to shelve
(block/filter) alarms. The conditions in the shelf
criteria are logically ANDed. The first matching shelf is
used, and an alarm is shelved only for this first match.
Matching alarms MUST appear in the
/alarms/shelved-alarms/shelved-alarm list, and
non-matching /alarms MUST appear in the
/alarms/alarm-list/alarm list. The server does not send
any notifications for shelved alarms.
The server MUST maintain states (e.g., severity
changes) for the shelved alarms.
Alarms that match the criteria shall have an
operator state 'shelved'. When the shelf
configuration removes an alarm from the shelf, the server
shall add the operator state 'un-shelved'.";
list shelf {
key "name";
ordered-by user;
leaf name {
type string;
description
"An arbitrary name for the alarm shelf.";
}
description
"Each entry defines the criteria for shelving alarms.
Criteria are ANDed. If no criteria are specified,
all alarms will be shelved.";
leaf-list resource {
type resource-match;
description
"Shelve alarms for matching resources.";
}
list alarm-type {
key "alarm-type-id alarm-type-qualifier-match";
description
"Any alarm matching the combined criteria of
'alarm-type-id' and 'alarm-type-qualifier-match'
MUST be matched.";
leaf alarm-type-id {
type alarm-type-id;
description
"Shelve all alarms that have an 'alarm-type-id' that
is equal to or derived from the given
'alarm-type-id'.";
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}
leaf alarm-type-qualifier-match {
type string;
description
"An XML Schema regular expression that is used to
match an alarm type qualifier. Shelve all alarms
that match this regular expression for the alarm
type qualifier.";
reference
"XML Schema Part 2: Datatypes Second Edition,
World Wide Web Consortium Recommendation
REC-xmlschema-2-20041028";
}
}
leaf description {
type string;
description
"An optional textual description of the shelf. This
description should include the reason for shelving
these alarms.";
}
}
}
}
container alarm-inventory {
config false;
description
"The 'alarm-inventory/alarm-type' list contains all possible
alarm types for the system.
If the system knows for which resources a specific alarm
type can appear, it is also identified in the inventory.
The list also tells if each alarm type has a corresponding
clear state. The inventory shall only contain concrete
alarm types.
The alarm inventory MUST be updated by the system when new
alarms can appear. This can be the case when installing new
software modules or inserting new card types. A
notification 'alarm-inventory-changed' is sent when the
inventory is changed.";
list alarm-type {
key "alarm-type-id alarm-type-qualifier";
description
"An entry in this list defines a possible alarm.";
leaf alarm-type-id {
type alarm-type-id;
description
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"The statically defined alarm type identifier for this
possible alarm.";
}
leaf alarm-type-qualifier {
type alarm-type-qualifier;
description
"The optionally dynamically defined alarm type identifier
for this possible alarm.";
}
leaf-list resource {
type resource-match;
description
"Optionally, specifies for which resources the alarm type
is valid.";
}
leaf will-clear {
type boolean;
mandatory true;
description
"This leaf tells the operator if the alarm will be
cleared when the correct corrective action has been
taken. Implementations SHOULD strive for detecting the
cleared state for all alarm types.
If this leaf is 'true', the operator can monitor the
alarm until it becomes cleared after the corrective
action has been taken.
If this leaf is 'false', the operator needs to validate
that the alarm is no longer active using other
mechanisms. Alarms can lack a corresponding clear due
to missing instrumentation or no logical
corresponding clear state.";
}
leaf-list severity-level {
type severity;
description
"This leaf-list indicates the possible severity levels of
this alarm type. Note well that 'clear' is not part of
the severity type. In general, the severity level
should be defined by the instrumentation based on the
dynamic state, rather than being defined statically by
the alarm type, in order to provide a relevant severity
level based on dynamic state and context. However, most
alarm types have a defined set of possible severity
levels, and this should be provided here.";
}
leaf description {
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type string;
mandatory true;
description
"A description of the possible alarm. It SHOULD include
information on possible underlying root causes and
corrective actions.";
}
}
}
container summary {
if-feature "alarm-summary";
config false;
description
"This container gives a summary of the number of alarms.";
list alarm-summary {
key "severity";
description
"A global summary of all alarms in the system. The summary
does not include shelved alarms.";
leaf severity {
type severity;
description
"Alarm summary for this severity level.";
}
leaf total {
type yang:gauge32;
description
"Total number of alarms of this severity level.";
}
leaf not-cleared {
type yang:gauge32;
description
"Total number of alarms of this severity level
that are not cleared.";
}
leaf cleared {
type yang:gauge32;
description
"For this severity level, the number of alarms that are
cleared.";
}
leaf cleared-not-closed {
if-feature "operator-actions";
type yang:gauge32;
description
"For this severity level, the number of alarms that are
cleared but not closed.";
}
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leaf cleared-closed {
if-feature "operator-actions";
type yang:gauge32;
description
"For this severity level, the number of alarms that are
cleared and closed.";
}
leaf not-cleared-closed {
if-feature "operator-actions";
type yang:gauge32;
description
"For this severity level, the number of alarms that are
not cleared but closed.";
}
leaf not-cleared-not-closed {
if-feature "operator-actions";
type yang:gauge32;
description
"For this severity level, the number of alarms that are
not cleared and not closed.";
}
}
leaf shelves-active {
if-feature "alarm-shelving";
type empty;
description
"This is a hint to the operator that there are active
alarm shelves. This leaf MUST exist if the
/alarms/shelved-alarms/number-of-shelved-alarms is > 0.";
}
}
container alarm-list {
config false;
description
"The alarms in the system.";
leaf number-of-alarms {
type yang:gauge32;
description
"This object shows the total number of
alarms in the system, i.e., the total number
of entries in the alarm list.";
}
leaf last-changed {
type yang:date-and-time;
description
"A timestamp when the alarm list was last
changed. The value can be used by a manager to
initiate an alarm resynchronization procedure.";
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}
list alarm {
key "resource alarm-type-id alarm-type-qualifier";
description
"The list of alarms. Each entry in the list holds one
alarm for a given alarm type and resource. An alarm can
be updated from the underlying resource or by the user.
The following leafs are maintained by the resource:
'is-cleared', 'last-change', 'perceived-severity', and
'alarm-text'. An operator can change 'operator-state' and
'operator-text'.
Entries appear in the alarm list the first time an alarm
becomes active for a given alarm type and resource.
Entries do not get deleted when the alarm is cleared.
Clear status is represented as a boolean flag.
Alarm entries are removed, i.e., purged, from the list by
an explicit purge action. For example, purge all alarms
that are cleared and in closed operator state that are
older than 24 hours. Purged alarms are removed from the
alarm list. If the alarm resource state changes after a
purge, the alarm will reappear in the alarm list.
Systems may also remove alarms based on locally configured
policies; this is out of scope for this module.";
uses common-alarm-parameters;
leaf time-created {
type yang:date-and-time;
mandatory true;
description
"The timestamp when this alarm entry was created. This
represents the first time the alarm appeared; it can
also represent that the alarm reappeared after a purge.
Further state changes of the same alarm do not change
this leaf; these changes will update the 'last-changed'
leaf.";
}
uses resource-alarm-parameters;
list operator-state-change {
if-feature "operator-actions";
key "time";
description
"This list is used by operators to indicate the state of
human intervention on an alarm. For example, if an
operator has seen an alarm, the operator can add a new
item to this list indicating that the alarm is
acknowledged.";
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uses operator-parameters;
}
action set-operator-state {
if-feature "operator-actions";
description
"This is a means for the operator to indicate the level
of human intervention on an alarm.";
input {
leaf state {
type writable-operator-state;
mandatory true;
description
"Set this operator state.";
}
leaf text {
type string;
description
"Additional optional textual information.";
}
}
}
notification operator-action {
if-feature "operator-actions";
description
"This notification is used to report that an operator
acted upon an alarm.";
uses operator-parameters;
}
}
action purge-alarms {
description
"This operation requests that the server delete entries
from the alarm list according to the supplied criteria.
Typically, this operation is used to delete alarms that
are in closed operator state and older than a specified
time.
The number of purged alarms is returned as an output
parameter.";
input {
uses filter-input;
}
output {
leaf purged-alarms {
type uint32;
description
"Number of purged alarms.";
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}
}
}
action compress-alarms {
if-feature "alarm-history";
description
"This operation requests that the server compress
entries in the alarm list by removing all but the
latest 'status-change' entry for all matching alarms.
Conditions in the input are logically ANDed. If no
input condition is given, all alarms are compressed.";
input {
leaf resource {
type resource-match;
description
"Compress the alarms matching this resource.";
}
leaf alarm-type-id {
type leafref {
path "/alarms/alarm-list/alarm/alarm-type-id";
require-instance false;
}
description
"Compress alarms with this 'alarm-type-id'.";
}
leaf alarm-type-qualifier {
type leafref {
path "/alarms/alarm-list/alarm/alarm-type-qualifier";
require-instance false;
}
description
"Compress the alarms with this
'alarm-type-qualifier'.";
}
}
output {
leaf compressed-alarms {
type uint32;
description
"Number of compressed alarm entries.";
}
}
}
}
container shelved-alarms {
if-feature "alarm-shelving";
config false;
description
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"The shelved alarms. Alarms appear here if they match the
criteria in /alarms/control/alarm-shelving. This list does
not generate any notifications. The list represents alarms
that are considered not relevant by the operator. Alarms in
this list have an 'operator-state' of 'shelved'. This
cannot be changed.";
leaf number-of-shelved-alarms {
type yang:gauge32;
description
"This object shows the total number of current
alarms, i.e., the total number of entries
in the alarm list.";
}
leaf shelved-alarms-last-changed {
type yang:date-and-time;
description
"A timestamp when the shelved-alarm list was last changed.
The value can be used by a manager to initiate an alarm
resynchronization procedure.";
}
list shelved-alarm {
key "resource alarm-type-id alarm-type-qualifier";
description
"The list of shelved alarms. Shelved alarms can only be
updated from the underlying resource; no operator actions
are supported.";
uses common-alarm-parameters;
leaf shelf-name {
type leafref {
path "/alarms/control/alarm-shelving/shelf/name";
require-instance false;
}
description
"The name of the shelf.";
}
uses resource-alarm-parameters;
list operator-state-change {
if-feature "operator-actions";
key "time";
description
"This list is used by operators to indicate the state of
human intervention on an alarm. For shelved alarms, the
system has set the list item in the list to 'shelved'.";
uses operator-parameters;
}
}
action purge-shelved-alarms {
description
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"This operation requests that the server delete entries from
the shelved-alarm list according to the supplied criteria.
In the shelved-alarm list, it makes sense to delete alarms
that are not relevant anymore.
The number of purged alarms is returned as an output
parameter.";
input {
uses filter-input;
}
output {
leaf purged-alarms {
type uint32;
description
"Number of purged alarms.";
}
}
}
action compress-shelved-alarms {
if-feature "alarm-history";
description
"This operation requests that the server compress entries
in the shelved-alarm list by removing all but the latest
'status-change' entry for all matching shelved alarms.
Conditions in the input are logically ANDed. If no input
condition is given, all alarms are compressed.";
input {
leaf resource {
type leafref {
path "/alarms/shelved-alarms/shelved-alarm/resource";
require-instance false;
}
description
"Compress the alarms with this resource.";
}
leaf alarm-type-id {
type leafref {
path "/alarms/shelved-alarms/shelved-alarm"
+ "/alarm-type-id";
require-instance false;
}
description
"Compress alarms with this 'alarm-type-id'.";
}
leaf alarm-type-qualifier {
type leafref {
path "/alarms/shelved-alarms/shelved-alarm"
+ "/alarm-type-qualifier";
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require-instance false;
}
description
"Compress the alarms with this
'alarm-type-qualifier'.";
}
}
output {
leaf compressed-alarms {
type uint32;
description
"Number of compressed alarm entries.";
}
}
}
}
list alarm-profile {
if-feature "alarm-profile";
key "alarm-type-id alarm-type-qualifier-match resource";
ordered-by user;
description
"This list is used to assign further information or
configuration for each alarm type. This module supports a
mechanism where the client can override the system-default
alarm severity levels. The 'alarm-profile' is also a useful
augmentation point for specific additions to alarm types.";
leaf alarm-type-id {
type alarm-type-id;
description
"The alarm type identifier to match.";
}
leaf alarm-type-qualifier-match {
type string;
description
"An XML Schema regular expression that is used to match the
alarm type qualifier.";
reference
"XML Schema Part 2: Datatypes Second Edition,
World Wide Web Consortium Recommendation
REC-xmlschema-2-20041028";
}
leaf resource {
type resource-match;
description
"Specifies which resources to match.";
}
leaf description {
type string;
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mandatory true;
description
"A description of the alarm profile.";
}
container alarm-severity-assignment-profile {
if-feature "severity-assignment";
description
"The client can override the system-default severity
level.";
reference
"ITU-T Recommendation M.3100:
Generic network information model
ITU-T Recommendation M.3160:
Generic, protocol-neutral management information model";
leaf-list severity-level {
type severity;
ordered-by user;
description
"Specifies the configured severity level(s) for the
matching alarm. If the alarm has several severity
levels, the leaf-list shall be given in rising severity
order. The original M3100/M3160 ASAP function only
allows for a one-to-one mapping between alarm type and
severity, but since YANG module supports stateful
alarms, the mapping must allow for several severity
levels.
Assume a high-utilization alarm type with two thresholds
with the system-default severity levels of threshold1 =
warning and threshold2 = minor. Setting this leaf-list
to (minor, major) will assign the severity levels as
threshold1 = minor and threshold2 = major";
}
}
}
}
/*
* Notifications
*/
notification alarm-notification {
description
"This notification is used to report a state change for an
alarm. The same notification is used for reporting a newly
raised alarm, a cleared alarm, or changing the text and/or
severity of an existing alarm.";
uses common-alarm-parameters;
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uses alarm-state-change-parameters;
}
notification alarm-inventory-changed {
description
"This notification is used to report that the list of possible
alarms has changed. This can happen when, for example, a new
software module is installed or a new physical card is
inserted.";
}
}
<CODE ENDS>
7. The X.733 Mapping Module
Many alarm systems are based on the X.733 [X.733] and X.736 [X.736]
alarm standards. This module "ietf-alarms-x733" augments the alarm
inventory, the alarm lists, and the alarm notification with X.733 and
X.736 parameters.
The module also supports a feature whereby the alarm manager can
configure the mapping from alarm types to X.733 "event-type" and
"probable-cause" parameters. This might be needed when the default
mapping provided by the system is in conflict with other management
systems or not considered correct.
Note that the term "resource" in this document is synonymous to the
ITU term "managed object".
This YANG module references [RFC6991], [X.721], [X.733], and [X.736].
<CODE BEGINS> file "ietf-alarms-x733@2019-09-11.yang"
module ietf-alarms-x733 {
yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang:ietf-alarms-x733";
prefix x733;
import ietf-alarms {
prefix al;
}
import ietf-yang-types {
prefix yang;
reference
"RFC 6991: Common YANG Data Types";
}
organization
"IETF CCAMP Working Group";
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contact
"WG Web: <https://trac.ietf.org/trac/ccamp>
WG List: <mailto:ccamp@ietf.org>
Editor: Stefan Vallin
<mailto:stefan@wallan.se>
Editor: Martin Bjorklund
<mailto:mbj@tail-f.com>";
description
"This module augments the ietf-alarms module with X.733 alarm
parameters.
The following structures are augmented with the X.733 event type
and probable cause:
1) alarms/alarm-inventory: all possible alarm types
2) alarms/alarm-list: every alarm in the system
3) alarm-notification: notifications indicating alarm-state
changes
4) alarms/shelved-alarms
The module also optionally allows the alarm-management system
to configure the mapping from the ietf-alarms' alarm keys
to the ITU tuple (event-type, probable-cause).
The mapping does not include a corresponding problem value
specific to X.733. The recommendation is to use the
'alarm-type-qualifier' leaf, which serves the same purpose.
The module uses an integer and a corresponding string for
probable cause instead of a globally defined enumeration, in
order to be able to manage conflicting enumeration definitions.
A single globally defined enumeration is challenging to
maintain.
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
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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 8632; see
the RFC itself for full legal notices.";
reference
"ITU-T Recommendation X.733: Information Technology
- Open Systems Interconnection
- System Management: Alarm Reporting Function";
revision 2019-09-11 {
description
"Initial revision.";
reference
"RFC 8632: A YANG Data Model for Alarm Management";
}
/*
* Features
*/
feature configure-x733-mapping {
description
"The system supports configurable X733 mapping from
the ietf-alarms' alarm-type to X733 event-type
and probable-cause.";
}
/*
* Typedefs
*/
typedef event-type {
type enumeration {
enum other {
value 1;
description
"None of the below.";
}
enum communications-alarm {
value 2;
description
"An alarm of this type is principally associated with the
procedures and/or processes required to convey
information from one point to another.";
}
enum quality-of-service-alarm {
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value 3;
description
"An alarm of this type is principally associated with a
degradation in the quality of a service.";
}
enum processing-error-alarm {
value 4;
description
"An alarm of this type is principally associated with a
software or processing fault.";
}
enum equipment-alarm {
value 5;
description
"An alarm of this type is principally associated with an
equipment fault.";
}
enum environmental-alarm {
value 6;
description
"An alarm of this type is principally associated with a
condition relating to an enclosure in which the equipment
resides.";
}
enum integrity-violation {
value 7;
description
"An indication that information may have been illegally
modified, inserted, or deleted.";
}
enum operational-violation {
value 8;
description
"An indication that the provision of the requested service
was not possible due to the unavailability, malfunction,
or incorrect invocation of the service.";
}
enum physical-violation {
value 9;
description
"An indication that a physical resource has been violated
in a way that suggests a security attack.";
}
enum security-service-or-mechanism-violation {
value 10;
description
"An indication that a security attack has been detected by
a security service or mechanism.";
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}
enum time-domain-violation {
value 11;
description
"An indication that an event has occurred at an unexpected
or prohibited time.";
}
}
description
"The event types as defined by X.733 and X.736.";
reference
"ITU-T Recommendation X.733: Information Technology
- Open Systems Interconnection
- System Management: Alarm Reporting Function
ITU-T Recommendation X.736: Information Technology
- Open Systems Interconnection
- System Management: Security Alarm Reporting Function";
}
typedef trend {
type enumeration {
enum less-severe {
description
"There is at least one outstanding alarm of a
severity higher (more severe) than that in the
current alarm.";
}
enum no-change {
description
"The Perceived severity reported in the current
alarm is the same as the highest (most severe)
of any of the outstanding alarms";
}
enum more-severe {
description
"The Perceived severity in the current alarm is
higher (more severe) than that reported in any
of the outstanding alarms.";
}
}
description
"This type is used to describe the
severity trend of the alarming resource.";
reference
"ITU-T Recommendation X.721: Information Technology
- Open Systems Interconnection
- Structure of management information:
Definition of management information
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Module Attribute-ASN1Module";
}
typedef value-type {
type union {
type int64;
type uint64;
type decimal64 {
fraction-digits 2;
}
}
description
"A generic union type to match the ITU choice of
integer and real.";
}
/*
* Groupings
*/
grouping x733-alarm-parameters {
description
"Common X.733 parameters for alarms.";
leaf event-type {
type event-type;
description
"The X.733/X.736 event type for this alarm.";
}
leaf probable-cause {
type uint32;
description
"The X.733 probable cause for this alarm.";
}
leaf probable-cause-string {
type string;
description
"The user-friendly string matching
the probable cause integer value. The string
SHOULD match the X.733 enumeration. For example,
value 27 is 'localNodeTransmissionError'.";
}
container threshold-information {
description
"This parameter shall be present when the alarm
is a result of crossing a threshold. ";
leaf triggered-threshold {
type string;
description
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"The identifier of the threshold attribute that
caused the notification.";
}
leaf observed-value {
type value-type;
description
"The value of the gauge or counter that crossed
the threshold. This may be different from the
threshold value if, for example, the gauge may
only take on discrete values.";
}
choice threshold-level {
description
"In the case of a gauge, the threshold level specifies
a pair of threshold values: the first is the value
of the crossed threshold, and the second is its
corresponding hysteresis; in the case of a counter,
the threshold level specifies only the threshold
value.";
case up {
leaf up-high {
type value-type;
description
"The going-up threshold for raising the alarm.";
}
leaf up-low {
type value-type;
description
"The going-down threshold for clearing the alarm.
This is used for hysteresis functions for gauges.";
}
}
case down {
leaf down-low {
type value-type;
description
"The going-down threshold for raising the alarm.";
}
leaf down-high {
type value-type;
description
"The going-up threshold for clearing the alarm.
This is used for hysteresis functions for gauges.";
}
}
}
leaf arm-time {
type yang:date-and-time;
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description
"For a gauge threshold, it's the time at which the
threshold was last re-armed; namely, it's the time after
the previous threshold crossing at which the hysteresis
value of the threshold was exceeded, thus again permitting
the generation of notifications when the threshold is
crossed. For a counter threshold, it's the later of the
time at which the threshold offset was last applied or the
counter was last initialized (for resettable counters).";
}
}
list monitored-attributes {
uses attribute;
key "id";
description
"The Monitored attributes parameter, when present, defines
one or more attributes of the resource and their
corresponding values at the time of the alarm.";
}
leaf-list proposed-repair-actions {
type string;
description
"This parameter, when present, is used if the cause is
known and the system being managed can suggest one or
more solutions (such as switch in standby equipment,
retry, and replace media).";
}
leaf trend-indication {
type trend;
description
"This parameter specifies the current severity
trend of the resource. If present, it indicates
that there are one or more alarms ('outstanding
alarms') that have not been cleared and that
pertain to the same resource as this alarm
('current alarm') does. The possible values are:
more-severe: The Perceived severity in the current
alarm is higher (more severe) than that reported in
any of the outstanding alarms.
no-change: The Perceived severity reported in the
current alarm is the same as the highest (most severe)
of any of the outstanding alarms.
less-severe: There is at least one outstanding alarm
of a severity higher (more severe) than that in the
current alarm.";
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}
leaf backedup-status {
type boolean;
description
"This parameter, when present, specifies whether or not the
object emitting the alarm has been backed up; therefore, it
is possible to know whether or not services provided to the
user have been disrupted when this parameter is included.
The use of this field in conjunction with the
'perceived-severity' field provides information in an
independent form to qualify the seriousness of the alarm and
the ability of the system as a whole to continue to provide
services. If the value of this parameter is true, it
indicates that the object emitting the alarm has been backed
up; if false, the object has not been backed up.";
}
leaf backup-object {
type al:resource;
description
"This parameter SHALL be present when the 'backedup-status'
parameter is present and has the value 'true'. This
parameter specifies the managed object instance that is
providing back-up services for the managed object to which
the notification pertains. This parameter is useful, for
example, when the back-up object is from a pool of objects,
any of which may be dynamically allocated to replace a
faulty object.";
}
list additional-information {
key "identifier";
description
"This parameter allows the inclusion of an additional
information set in the alarm. It is a series of data
structures, each of which contains three items of
information: an identifier, a significance indicator,
and the problem information.";
leaf identifier {
type string;
description
"Identifies the data type of the information parameter.";
}
leaf significant {
type boolean;
description
"Set to 'true' if the receiving system must be able to
parse the contents of the information subparameter
for the event report to be fully understood.";
}
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leaf information {
type string;
description
"Additional information about the alarm.";
}
}
leaf security-alarm-detector {
type al:resource;
description
"This parameter identifies the detector of the security
alarm.";
}
leaf service-user {
type al:resource;
description
"This parameter identifies the service-user whose request
for service led to the generation of the security alarm.";
}
leaf service-provider {
type al:resource;
description
"This parameter identifies the intended service-provider
of the service that led to the generation of the security
alarm.";
}
reference
"ITU-T Recommendation X.733: Information Technology
- Open Systems Interconnection
- System Management: Alarm Reporting Function
ITU-T Recommendation X.736: Information Technology
- Open Systems Interconnection
- System Management: Security Alarm Reporting Function";
}
grouping x733-alarm-definition-parameters {
description
"Common X.733 parameters for alarm definitions.
This grouping is used to define those alarm
attributes that can be mapped from the alarm-type
mechanism in the ietf-alarms module.";
leaf event-type {
type event-type;
description
"The alarm type has this X.733/X.736 event type.";
}
leaf probable-cause {
type uint32;
description
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"The alarm type has this X.733 probable cause value.
This module defines probable cause as an integer
and not as an enumeration. The reason being that the
primary use of probable cause is in the management
application if it is based on the X.733 standard.
However, most management applications have their own
defined enum definitions and merging enums from
different systems might create conflicts. By using
a configurable uint32, the system can be configured
to match the enum values in the management application.";
}
leaf probable-cause-string {
type string;
description
"This string can be used to give a user-friendly string
to the probable cause value.";
}
}
grouping attribute {
description
"A grouping to match the ITU generic reference to
an attribute.";
leaf id {
type al:resource;
description
"The resource representing the attribute.";
}
leaf value {
type string;
description
"The value represented as a string since it could
be of any type.";
}
reference
"ITU-T Recommendation X.721: Information Technology
- Open Systems Interconnection
- Structure of management information:
Definition of management information
Module Attribute-ASN1Module";
}
/*
* Add X.733 parameters to the alarm definitions, alarms,
* and notification.
*/
augment "/al:alarms/al:alarm-inventory/al:alarm-type" {
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description
"Augment X.733 mapping information to the alarm inventory.";
uses x733-alarm-definition-parameters;
}
/*
* Add X.733 configurable mapping.
*/
augment "/al:alarms/al:control" {
description
"Add X.733 mapping capabilities. ";
list x733-mapping {
if-feature "configure-x733-mapping";
key "alarm-type-id alarm-type-qualifier-match";
description
"This list allows a management application to control the
X.733 mapping for all alarm types in the system. Any entry
in this list will allow the alarm manager to override the
default X.733 mapping in the system, and the final mapping
will be shown in the alarm inventory.";
leaf alarm-type-id {
type al:alarm-type-id;
description
"Map the alarm type with this alarm type identifier.";
}
leaf alarm-type-qualifier-match {
type string;
description
"A W3C regular expression that is used when mapping an
alarm type and alarm-type-qualifier to X.733 parameters.";
}
uses x733-alarm-definition-parameters;
}
}
augment "/al:alarms/al:alarm-list/al:alarm" {
description
"Augment X.733 information to the alarm.";
uses x733-alarm-parameters;
}
augment "/al:alarms/al:shelved-alarms/al:shelved-alarm" {
description
"Augment X.733 information to the alarm.";
uses x733-alarm-parameters;
}
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augment "/al:alarm-notification" {
description
"Augment X.733 information to the alarm notification.";
uses x733-alarm-parameters;
}
}
<CODE ENDS>
8. IANA Considerations
This document registers two URIs in the "IETF XML Registry"
[RFC3688]. Following the format in RFC 3688, the following
registrations have been made.
URI: urn:ietf:params:xml:ns:yang:ietf-alarms
Registrant Contact: The IESG.
XML: N/A; the requested URI is an XML namespace.
URI: urn:ietf:params:xml:ns:yang:ietf-alarms-x733
Registrant Contact: The IESG.
XML: N/A; the requested URI is an XML namespace.
This document registers two YANG modules in the "YANG Module Names"
registry [RFC6020].
name: ietf-alarms
namespace: urn:ietf:params:xml:ns:yang:ietf-alarms
prefix: al
reference: RFC 8632
name: ietf-alarms-x733
namespace: urn:ietf:params:xml:ns:yang:ietf-alarms-x733
prefix: x733
reference: RFC 8632
9. Security Considerations
The YANG modules specified in this document define 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].
Vallin & Bjorklund Standards Track [Page 65]
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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 list of alarms itself may be potentially sensitive from a
security perspective, in that it potentially gives an attacker an
authoritative picture of the (broken) state of the network.
There are a number of data nodes defined in the YANG modules that are
writable/creatable/deletable (i.e., config true, which is the
default). These data nodes may be considered sensitive or vulnerable
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
in the "ietf-alarms" module and their sensitivity/vulnerability:
"/alarms/control/notify-status-changes": This leaf controls whether
an alarm should notify based on various state changes.
Unauthorized access to this leaf could have a negative impact on
operational procedures relying on fine-grained alarm-state change
reporting.
"/alarms/control/alarm-shelving/shelf": This list controls the
shelving (blocking) of alarms. Unauthorized access to this list
could jeopardize the alarm-management procedures, since these
alarms will not be notified or be part of the alarm list.
"/alarms/control/alarm-profile/alarm-severity-assignment-profile":
This list controls the severity levels of an alarm. Unauthorized
access to this could, for example, downgrade the severity of an
alarm and thereby have a negative impact on the alarm-monitoring
process.
Some of the RPC operations in this YANG module may be considered
sensitive or vulnerable in some network environments. It is thus
important to control access to these operations. These are the
operations and their sensitivity/vulnerability:
"/alarms/alarm-list/purge-alarms": This action deletes alarms from
the alarm list. Unauthorized use of this action could jeopardize
the alarm-management procedures since the deleted alarms may be
vital for the alarm-management application.
"/alarms/alarm-list/alarm/set-operator-state": This action can be
used by the operator to indicate the level of human intervention
on an alarm. Unauthorized use of this action could result in
alarms being ignored by operators.
Vallin & Bjorklund Standards Track [Page 66]
RFC 8632 A YANG Data Model for Alarm Management September 2019
10. References
10.1. Normative References
[M.3100] International Telecommunication Union, "Generic network
information model", ITU-T Recommendation M.3100, April
2005, <https://www.itu.int/rec/T-REC-M.3100-200504-I/en>.
[M.3160] International Telecommunication Union, "Generic,
protocol-neutral management information model",
ITU-T Recommendation M.3100, November 2008,
<https://www.itu.int/rec/T-REC-M.3160-200811-I>.
[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>.
[RFC6020] Bjorklund, M., Ed., "YANG - A Data Modeling Language for
the Network Configuration Protocol (NETCONF)", RFC 6020,
DOI 10.17487/RFC6020, October 2010,
<https://www.rfc-editor.org/info/rfc6020>.
[RFC6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
and A. Bierman, Ed., "Network Configuration Protocol
(NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
<https://www.rfc-editor.org/info/rfc6241>.
[RFC6242] Wasserman, M., "Using the NETCONF Protocol over Secure
Shell (SSH)", RFC 6242, DOI 10.17487/RFC6242, June 2011,
<https://www.rfc-editor.org/info/rfc6242>.
[RFC6991] Schoenwaelder, J., Ed., "Common YANG Data Types",
RFC 6991, DOI 10.17487/RFC6991, July 2013,
<https://www.rfc-editor.org/info/rfc6991>.
[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>.
[RFC8040] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017,
<https://www.rfc-editor.org/info/rfc8040>.
Vallin & Bjorklund Standards Track [Page 67]
RFC 8632 A YANG Data Model for Alarm Management September 2019
[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>.
[RFC8341] Bierman, A. and M. Bjorklund, "Network Configuration
Access Control Model", STD 91, RFC 8341,
DOI 10.17487/RFC8341, March 2018,
<https://www.rfc-editor.org/info/rfc8341>.
[RFC8348] Bierman, A., Bjorklund, M., Dong, J., and D. Romascanu, "A
YANG Data Model for Hardware Management", RFC 8348,
DOI 10.17487/RFC8348, March 2018,
<https://www.rfc-editor.org/info/rfc8348>.
[RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol
Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
<https://www.rfc-editor.org/info/rfc8446>.
[X.721] International Telecommunication Union, "Information
technology - Open Systems Interconnection - Structure of
management information: Definition of management
information", ITU-T Recommendation X.721, February 1992,
<https://www.itu.int/rec/T-REC-X.721-199202-I/en>.
[X.733] International Telecommunication Union, "Information
technology - Open Systems Interconnection - Systems
Management: Alarm reporting function",
ITU-T Recommendation X.733, February 1992,
<https://www.itu.int/rec/T-REC-X.733-199202-I/en>.
[XSD-TYPES]
Malhotra, A. and P. Biron, "XML Schema Part 2: Datatypes
Second Edition", World Wide Web Consortium Recommendation
REC-xmlschema-2-20041028, October 2004,
<http://www.w3.org/TR/2004/REC-xmlschema-2-20041028>.
10.2. Informative References
[ALARMIRP] 3GPP, "Telecommunication management; Fault Management;
Part 2: Alarm Integration Reference Point (IRP):
Information Service (IS)", 3GPP TS 32.111-2, March 2005,
<http://www.3gpp.org/ftp/Specs/html-info/32111-2.htm>.
[ALARMSEM] Wallin, S., Leijon, V., Nordlander, J., and N. Bystedt,
"The semantics of alarm definitions: enabling systematic
reasoning about alarms", International Journal of Network
Management, Volume 22, Issue 3, May 2012,
<http://dx.doi.org/10.1002/nem.800>.
Vallin & Bjorklund Standards Track [Page 68]
RFC 8632 A YANG Data Model for Alarm Management September 2019
[EEMUA] "Alarm systems: a guide to design, management and
procurement", EEMUA Publication No. 191, Engineering
Equipment and Materials Users Association, Second Edition,
2007.
[G.7710] International Telecommunication Union, "SERIES G:
TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND
NETWORKS - Data over Transport - Generic aspects -
Transport network control aspects; Common equipment
management function requirements", ITU-T
Recommendation G.7710/Y.1701, Amendment 1, November 2012.
[ISA182] International Society of Automation, "Management of Alarm
Systems for the Process Industries", ANSI/ISA - 18.2-2016,
March 2016.
[RFC3877] Chisholm, S. and D. Romascanu, "Alarm Management
Information Base (MIB)", RFC 3877, DOI 10.17487/RFC3877,
September 2004, <https://www.rfc-editor.org/info/rfc3877>.
[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>.
[X.736] International Telecommunication Union, "Information
technology - Open Systems Interconnection - Systems
Management: Security alarm reporting function",
ITU-T Recommendation X.736, January 1992,
<https://www.itu.int/rec/T-REC-X.736-199201-I/en>.
[YANG-INSTANCE]
Lengyel, B. and B. Claise, "YANG Instance Data File
Format", Work in Progress, draft-ietf-netmod-yang-
instance-file-format-02, August 2019.
Vallin & Bjorklund Standards Track [Page 69]
RFC 8632 A YANG Data Model for Alarm Management September 2019
Appendix A. Vendor-Specific Alarm Types Example
This example shows how to define alarm types in a vendor-specific
module. In this case, the vendor "xyz" has chosen to define top-
level identities according to X.733 event types.
module example-xyz-alarms {
namespace "urn:example:xyz-alarms";
prefix xyz-al;
import ietf-alarms {
prefix al;
}
identity xyz-alarms {
base al:alarm-type-id;
}
identity communications-alarm {
base xyz-alarms;
}
identity quality-of-service-alarm {
base xyz-alarms;
}
identity processing-error-alarm {
base xyz-alarms;
}
identity equipment-alarm {
base xyz-alarms;
}
identity environmental-alarm {
base xyz-alarms;
}
// communications alarms
identity link-alarm {
base communications-alarm;
}
// QoS alarms
identity high-jitter-alarm {
base quality-of-service-alarm;
}
}
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Appendix B. Alarm Inventory Example
This shows an alarm inventory: one alarm type is defined only with
the identifier and another is dynamically configured. In the latter
case, a digital input has been connected to a smoke detector;
therefore, the "alarm-type-qualifier" is set to "smoke-detector" and
the "alarm-type-id" to "environmental-alarm".
<alarms xmlns="urn:ietf:params:xml:ns:yang:ietf-alarms"
xmlns:xyz-al="urn:example:xyz-alarms"
xmlns:dev="urn:example:device">
<alarm-inventory>
<alarm-type>
<alarm-type-id>xyz-al:link-alarm</alarm-type-id>
<alarm-type-qualifier/>
<resource>
/dev:interfaces/dev:interface
</resource>
<will-clear>true</will-clear>
<description>
Link failure; operational state down but admin state up
</description>
</alarm-type>
<alarm-type>
<alarm-type-id>xyz-al:environmental-alarm</alarm-type-id>
<alarm-type-qualifier>smoke-alarm</alarm-type-qualifier>
<will-clear>true</will-clear>
<description>
Connected smoke detector to digital input
</description>
</alarm-type>
</alarm-inventory>
</alarms>
Appendix C. Alarm List Example
In this example, we show an alarm that has toggled [major, clear,
major]. An operator has acknowledged the alarm.
<alarms xmlns="urn:ietf:params:xml:ns:yang:ietf-alarms"
xmlns:xyz-al="urn:example:xyz-alarms"
xmlns:dev="urn:example:device">
<alarm-list>
<number-of-alarms>1</number-of-alarms>
<last-changed>2018-04-08T08:39:50.00Z</last-changed>
<alarm>
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<resource>
/dev:interfaces/dev:interface[name='FastEthernet1/0']
</resource>
<alarm-type-id>xyz-al:link-alarm</alarm-type-id>
<alarm-type-qualifier></alarm-type-qualifier>
<time-created>2018-04-08T08:20:10.00Z</time-created>
<is-cleared>false</is-cleared>
<alt-resource>1.3.6.1.2.1.2.2.1.1.17</alt-resource>
<last-raised>2018-04-08T08:39:40.00Z</last-raised>
<last-changed>2018-04-08T08:39:50.00Z</last-changed>
<perceived-severity>major</perceived-severity>
<alarm-text>
Link operationally down but administratively up
</alarm-text>
<status-change>
<time>2018-04-08T08:39:40.00Z</time>
<perceived-severity>major</perceived-severity>
<alarm-text>
Link operationally down but administratively up
</alarm-text>
</status-change>
<status-change>
<time>2018-04-08T08:30:00.00Z</time>
<perceived-severity>cleared</perceived-severity>
<alarm-text>
Link operationally up and administratively up
</alarm-text>
</status-change>
<status-change>
<time>2018-04-08T08:20:10.00Z</time>
<perceived-severity>major</perceived-severity>
<alarm-text>
Link operationally down but administratively up
</alarm-text>
</status-change>
<operator-state-change>
<time>2018-04-08T08:39:50.00Z</time>
<state>ack</state>
<operator>joe</operator>
<text>Will investigate, ticket TR764999</text>
</operator-state-change>
</alarm>
</alarm-list>
</alarms>
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Appendix D. Alarm Shelving Example
This example shows how to shelve alarms. We shelve alarms related to
the smoke detectors, since they are being installed and tested. We
also shelve all alarms from FastEthernet1/0.
<alarms xmlns="urn:ietf:params:xml:ns:yang:ietf-alarms"
xmlns:xyz-al="urn:example:xyz-alarms"
xmlns:dev="urn:example:device">
<control>
<alarm-shelving>
<shelf>
<name>FE10</name>
<resource>
/dev:interfaces/dev:interface[name='FastEthernet1/0']
</resource>
</shelf>
<shelf>
<name>detectortest</name>
<alarm-type>
<alarm-type-id>
xyz-al:environmental-alarm
</alarm-type-id>
<alarm-type-qualifier-match>
smoke-alarm
</alarm-type-qualifier-match>
</alarm-type>
</shelf>
</alarm-shelving>
</control>
</alarms>
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Appendix E. X.733 Mapping Example
This example shows how to map a dynamic alarm type (alarm-type-
id=environmental-alarm, alarm-type-qualifier=smoke-alarm) to the
corresponding X.733 "event-type" and "probable-cause" parameters.
<alarms xmlns="urn:ietf:params:xml:ns:yang:ietf-alarms"
xmlns:xyz-al="urn:example:xyz-alarms">
<control>
<x733-mapping
xmlns="urn:ietf:params:xml:ns:yang:ietf-alarms-x733">
<alarm-type-id>xyz-al:environmental-alarm</alarm-type-id>
<alarm-type-qualifier-match>
smoke-alarm
</alarm-type-qualifier-match>
<event-type>quality-of-service-alarm</event-type>
<probable-cause>777</probable-cause>
</x733-mapping>
</control>
</alarms>
Appendix F. Relationship to Other Alarm Standards
This section briefly describes how this alarm data model relates to
other relevant standards.
F.1. Definition of "Alarm"
The table below summarizes relevant definitions of the term "alarm"
in other alarm standards.
+------------+---------------------------+--------------------------+
| Standard | Definition | Comment |
+------------+---------------------------+--------------------------+
| X.733 | error: A deviation of a | The X.733 alarm |
| [X.733] | system from normal | definition is focused on |
| | operation. fault: The | the notification as such |
| | physical or algorithmic | and not the state. |
| | cause of a malfunction. | X.733 defines an alarm |
| | Faults manifest | as a deviation from a |
| | themselves as errors. | normal condition but |
| | alarm: A notification, of | without the requirement |
| | the form defined by this | that it needs corrective |
| | function, of a specific | actions. |
| | event. An alarm may or | |
| | may not represent an | |
| | error. | |
| | | |
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RFC 8632 A YANG Data Model for Alarm Management September 2019
| G.7710 | Alarms are indications | The G.7710 definition is |
| [G.7710] | that are automatically | close to the original |
| | generated by a device as | X.733 definition. |
| | a result of the | |
| | declaration of a failure. | |
| | | |
| Alarm MIB | Alarm: Persistent | RFC 3877 defines the |
| [RFC3877] | indication of a fault. | term alarm as referring |
| | Fault: Lasting error or | back to "a deviation |
| | warning condition. | from normal operation". |
| | Error: A deviation of a | The Alarm YANG data |
| | system from normal | model adds the |
| | operation. | requirement that it |
| | | should require a |
| | | corrective action and |
| | | should be undesired, not |
| | | only a deviation from |
| | | normal. The alarm MIB |
| | | is state oriented in the |
| | | same way as the Alarm |
| | | YANG module; it focuses |
| | | on the "lasting |
| | | condition", not the |
| | | individual |
| | | notifications. |
| | | |
| ISA | Alarm: An audible and/or | The ISA standard adds an |
| [ISA182] | visible means of | important requirement to |
| | indicating to the | the "deviation from |
| | operator an equipment | normal condition state": |
| | malfunction, process | requiring a response. |
| | deviation, or abnormal | |
| | condition requiring a | |
| | response. | |
| | | |
| EEMUA | An alarm is an event to | This is the foundation |
| [EEMUA] | which an operator must | for the definition of |
| | knowingly react, respond, | alarm in this document. |
| | and acknowledge -- not | It focuses on the core |
| | simply acknowledge and | criterion that an action |
| | ignore. | is really needed. |
| | | |
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RFC 8632 A YANG Data Model for Alarm Management September 2019
| 3GPP Alarm | 3GPP v15: An alarm | The latest 3GPP Alarm |
| IRP | signifies an undesired | IRP version uses |
| [ALARMIRP] | condition of a resource | literally the same alarm |
| | (e.g., device, link) for | definition as this alarm |
| | which an operator action | data model. It is worth |
| | is required. It | noting that earlier |
| | emphasizes a key | versions used a |
| | requirement that | definition not requiring |
| | operators [...] should | an operator action and |
| | not be informed about an | the more-broad |
| | undesired condition | definition of deviation |
| | unless it requires | from normal condition. |
| | operator action. | The earlier version also |
| | 3GPP v12: alarm: abnormal | defined an alarm as a |
| | network entity condition, | special case of "event". |
| | which categorizes an | |
| | event as a fault. | |
| | fault: a deviation of a | |
| | system from normal | |
| | operation, which may | |
| | result in the loss of | |
| | operational capabilities | |
| | [...] | |
+------------+---------------------------+--------------------------+
Table 1: Definition of the Term "Alarm" in Standards
The evolution of the definition of alarm moves from focused on events
reporting a deviation from normal operation towards a definition to a
undesired *state* that *requires an operator action*.
F.2. Data Model
This section describes how this YANG alarm data model relates to
other standard data models. Note well that we cover other data
models for alarm interfaces but not other standards such as SDO-
specific alarms.
F.2.1. X.733
X.733 has acted as a base for several alarm data models over the
years. The YANG alarm data model differs in the following ways:
X.733 models the alarm list as a list of notifications. The YANG
alarm data model defines the alarm list as the current alarm
states for the resources, which is generated from the state change
reporting notifications.
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RFC 8632 A YANG Data Model for Alarm Management September 2019
In X.733, an alarm can have the severity level "clear". In the
YANG alarm data model, "clear" is not a severity level; it is a
separate state of the alarm. An alarm can have the following
states, for example, (major, cleared) and (minor, not cleared).
X.733 uses a flat, globally defined enumerated "probable-cause" to
identify alarm types. This alarm data model uses a hierarchical
YANG identity: "alarm-type". This enables delegation of alarm
types within organizations. It also enables management to reason
about abstract alarm types corresponding to base identities; see
Section 3.2.
The YANG alarm data model has not included the majority of the
X.733 alarm attributes. Rather, these are defined in an
augmenting module [X.733] if "strict" X.733 compliance is needed.
F.2.2. The Alarm MIB (RFC 3877)
The MIB in RFC 3877 takes a different approach; rather than defining
a concrete data model for alarms, it defines a model to map existing
SNMP-managed objects and notifications into alarm states and alarm
notifications. This was necessary since MIBs were already defined
with both managed objects and notifications indicating alarms, for
example, "linkUp" and "linkDown" notifications in combination with
"ifAdminState" and "ifOperState". So, RFC 3877 cannot really be
compared to the alarm YANG module in that sense.
The Alarm MIB maps existing MIB definitions into alarms, such as
"alarmModelTable". The upside of that is that an SNMP Manager can,
at runtime, read the possible alarm types. This corresponds to the
"alarmInventory" in the alarm YANG module.
F.2.3. 3GPP Alarm IRP
The 3GPP Alarm IRP is an evolution of X.733. Main differences
between the alarm YANG module and 3GPP are as follows:
3GPP keeps the majority of the X.733 attributes, but the alarm
YANG module does not.
3GPP introduced overlapping and possibly conflicting keys for
alarms, alarmId, and (managed object, event type, probable cause,
specific problem). (See Example 3 in Annex C of [ALARMIRP]). In
the YANG alarm data model, the key for identifying an alarm
instance is clearly defined by ("resource", "alarm-type-id",
"alarm-type-qualifier"). See also Section 3.4 for more
information.
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The alarm YANG module clearly separates the resource/
instrumentation lifecycle from the operator lifecycle. 3GPP allows
operators to set the alarm severity to clear; this is not allowed
by this module. Rather, an operator closes an alarm, which does
not affect the severity.
F.2.4. G.7710
G.7710 is different than the previously referenced alarm standards.
It does not define a data model for alarm reporting. It defines
common equipment management function requirements including alarm
instrumentation. The scope is transport networks.
The requirements in G.7710 correspond to features in the alarm YANG
module in the following way:
Alarm Severity Assignment Profile (ASAP): the alarm profile
"/alarms/alarm-profile/".
Alarm Reporting Control (ARC): alarm shelving "/alarms/control/
alarm-shelving/" and the ability to control alarm notifications
"/alarms/control/notify-status-changes". Alarm shelving
corresponds to the use case of turning off alarm reporting for a
specific resource, which is the NALM (No ALarM) state in M.3100.
Appendix G. Alarm-Usability Requirements
This section defines usability requirements for alarms. Alarm
usability is important for an alarm interface. A data model will
help in defining the format, but if the actual alarms are of low
value, we have not gained the goal of alarm management.
Common alarm problems and their causes are summarized in Table 2.
This summary is adopted to networking based on the ISA [ISA182] and
Engineering Equipment Materials Users Association (EEMUA) [EEMUA]
standards.
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RFC 8632 A YANG Data Model for Alarm Management September 2019
+-----------------+--------------------------------+----------------+
| Problem | Cause | How this |
| | | module |
| | | addresses the |
| | | cause |
+-----------------+--------------------------------+----------------+
| Alarms are | "Nuisance" alarms (chattering | Strict |
| generated, but | alarms and fleeting alarms), | definition of |
| they are | faulty hardware, redundant | alarms |
| ignored by the | alarms, cascading alarms, | requiring |
| operator. | incorrect alarm settings, and | corrective |
| | alarms that have not been | response. See |
| | rationalized; the alarms | alarm |
| | represent log information | requirements |
| | rather than true alarms. | in Table 3. |
| | | |
| When alarms | Insufficient alarm-response | The alarm |
| occur, | procedures and not well- | inventory |
| operators do | defined alarm types. | lists all |
| not know how to | | alarm types |
| respond. | | and corrective |
| | | actions. See |
| | | alarm |
| | | requirements |
| | | in Table 3. |
| | | |
| The alarm | Nuisance alarms, stale alarms, | The alarm |
| display is full | and alarms from equipment not | definition and |
| of alarms, even | in service. | alarm |
| when there is | | shelving. |
| nothing wrong. | | |
| | | |
| During a | Incorrect prioritization of | State-based |
| failure, | alarms. Not using advanced | alarm model |
| operators are | alarm techniques (e.g., state- | and alarm-rate |
| flooded with so | based alarming). | requirements; |
| many alarms | | see Tables 4 |
| that they do | | and 5, |
| not know which | | respectively. |
| ones are the | | |
| most important. | | |
+-----------------+--------------------------------+----------------+
Table 2: Alarm Problems and Causes
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RFC 8632 A YANG Data Model for Alarm Management September 2019
Based upon the above problems, EEMUA gives the following definition
of a good alarm:
+----------------+--------------------------------------------------+
| Characteristic | Explanation |
+----------------+--------------------------------------------------+
| Relevant | Not spurious or of low operational value. |
| | |
| Unique | Not duplicating another alarm. |
| | |
| Timely | Not long before any response is needed or too |
| | late to do anything. |
| | |
| Prioritized | Indicating the importance that the operator |
| | deals with the problem. |
| | |
| Understandable | Having a message that is clear and easy to |
| | understand. |
| | |
| Diagnostic | Identifying the problem that has occurred. |
| | |
| Advisory | Indicative of the action to be taken. |
| | |
| Focusing | Drawing attention to the most important issues. |
+----------------+--------------------------------------------------+
Table 3: Definition of a Good Alarm
Vendors SHOULD rationalize all alarms according to the table above.
Another crucial requirement is acceptable alarm notification rates.
Vendors SHOULD make sure that they do not exceed the recommendations
from EEMUA below:
+-----------------------------------+-------------------------------+
| Long-Term Alarm Rate in Steady | Acceptability |
| Operation | |
+-----------------------------------+-------------------------------+
| More than one per minute | Very likely to be |
| | unacceptable. |
| | |
| One per 2 minutes | Likely to be overdemanding. |
| | |
| One per 5 minutes | Manageable. |
| | |
| Less than one per 10 minutes | Very likely to be acceptable. |
+-----------------------------------+-------------------------------+
Table 4: Acceptable Alarm Rates -- Steady State
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RFC 8632 A YANG Data Model for Alarm Management September 2019
+----------------------------+--------------------------------------+
| Number of alarms displayed | Acceptability |
| in 10 minutes following a | |
| major network problem | |
+----------------------------+--------------------------------------+
| More than 100 | Definitely excessive and very likely |
| | to lead to the operator abandoning |
| | the use of the alarm system. |
| | |
| 20-100 | Hard to cope with. |
| | |
| Under 10 | Should be manageable, but it may be |
| | difficult if several of the alarms |
| | require a complex operator response. |
+----------------------------+--------------------------------------+
Table 5: Acceptable Alarm Rates -- Burst
The numbers in Tables 4 and 5 are the sum of all alarms for a network
being managed from one alarm console. So every individual system or
Network Management System (NMS) contributes to these numbers.
Vendors SHOULD make sure that the following rules are used in
designing the alarm interface:
1. Rationalize the alarms in the system to ensure that every alarm
is necessary, has a purpose, and follows the cardinal rule that
it requires an operator response. Adheres to the rules of
Table 3.
2. Audit the quality of the alarms. Talk with the operators about
how well the alarm information supports them. Do they know what
to do in the event of an alarm? Are they able to quickly
diagnose the problem and determine the corrective action? Does
the alarm text adhere to the requirements in Table 3?
3. Analyze and benchmark the performance of the system and compare
it to the recommended metrics in Tables 4 and 5. Start by
identifying nuisance alarms, as well as standing alarms at normal
state and startup.
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Acknowledgements
The authors wish to thank Viktor Leijon and Johan Nordlander for
their valuable input on forming the alarm model.
The authors also wish to thank Nick Hancock, Joey Boyd, Tom Petch,
and Balazs Lengyel for their extensive reviews and contributions to
this document.
Authors' Addresses
Stefan Vallin
Stefan Vallin AB
Email: stefan@wallan.se
Martin Bjorklund
Cisco
Email: mbj@tail-f.com
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