Internet DRAFT - draft-vallin-ccamp-alarm-module
draft-vallin-ccamp-alarm-module
Network Working Group S. Vallin
Internet-Draft Stefan Vallin AB
Intended status: Standards Track M. Bjorklund
Expires: May 3, 2018 Cisco
October 30, 2017
YANG Alarm Module
draft-vallin-ccamp-alarm-module-01
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 RPCs 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 Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
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Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on May 3, 2018.
Copyright Notice
Copyright (c) 2017 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
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include Simplified BSD License text as described in Section 4.e of
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Requirements notation . . . . . . . . . . . . . . . . . . . . 3
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
3. Objectives . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. Alarm Module Concepts . . . . . . . . . . . . . . . . . . . . 5
4.1. Alarm Definition . . . . . . . . . . . . . . . . . . . . 5
4.2. Alarm Type . . . . . . . . . . . . . . . . . . . . . . . 5
4.3. Identifying Resource . . . . . . . . . . . . . . . . . . 7
4.4. Identifying Alarm Instances . . . . . . . . . . . . . . . 7
4.5. Alarm Life-Cycle . . . . . . . . . . . . . . . . . . . . 8
4.5.1. Resource Alarm Life-Cycle . . . . . . . . . . . . . . 8
4.5.2. Operator Alarm Life-cycle . . . . . . . . . . . . . . 9
4.5.3. Administrative Alarm Life-Cycle . . . . . . . . . . . 9
4.6. Root Cause and Impacted Resources . . . . . . . . . . . . 10
4.7. Alarm Shelving . . . . . . . . . . . . . . . . . . . . . 10
5. Alarm Data Model . . . . . . . . . . . . . . . . . . . . . . 10
5.1. Alarm Control . . . . . . . . . . . . . . . . . . . . . . 11
5.1.1. Alarm Shelving . . . . . . . . . . . . . . . . . . . 11
5.2. Alarm Inventory . . . . . . . . . . . . . . . . . . . . . 12
5.3. Alarm Summary . . . . . . . . . . . . . . . . . . . . . . 13
5.4. The Alarm List . . . . . . . . . . . . . . . . . . . . . 13
5.5. The Shelved Alarms List . . . . . . . . . . . . . . . . . 15
5.6. RPCs and Actions . . . . . . . . . . . . . . . . . . . . 15
5.7. Notifications . . . . . . . . . . . . . . . . . . . . . . 15
6. Alarm YANG Module . . . . . . . . . . . . . . . . . . . . . . 15
7. X.733 Alarm Mapping Data Model . . . . . . . . . . . . . . . 40
8. X.733 Alarm Mapping YANG Module . . . . . . . . . . . . . . . 41
9. Security Considerations . . . . . . . . . . . . . . . . . . . 47
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 47
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 47
11.1. Normative References . . . . . . . . . . . . . . . . . . 47
11.2. Informative References . . . . . . . . . . . . . . . . . 47
Appendix A. Vendor-specific Alarm-Types Example . . . . . . . . 48
Appendix B. Alarm Inventory Example . . . . . . . . . . . . . . 49
Appendix C. Alarm List Example . . . . . . . . . . . . . . . . . 50
Appendix D. Alarm Shelving Example . . . . . . . . . . . . . . . 51
Appendix E. X.733 Mapping Example . . . . . . . . . . . . . . . 52
Appendix F. Background and Usability Requirements . . . . . . . 52
F.1. Alarm Concepts . . . . . . . . . . . . . . . . . . . . . 53
F.1.1. Alarm type . . . . . . . . . . . . . . . . . . . . . 53
F.2. Usability Requirements . . . . . . . . . . . . . . . . . 54
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 57
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1. Requirements 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.
2. Introduction
This document defines a YANG [RFC7950] module for alarm management.
The purpose is to define a standardised 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 network management system in a standardised
format is a starting point for performing higher level network
assurance tasks.
This document defines a standardised YANG module for alarm
management. The design of the module is based on experience from
using and implementing available alarm standards.
2.1. Terminology
The following terms are defined in [RFC7950]:
o action
o client
o data tree
o RPC
o server
The following terms are used within this document:
o Alarm (the general concept): An alarm signifies an undesirable
state in a resource that requires corrective action.
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o Alarm Instance: The alarm state for a specific resource and alarm
type. For example (GigabitEthernet0/15, link-alarm). An entry in
the alarm list.
o Alarm Inventory: A list of all possible alarm types on a system.
o Alarm Shelving: Blocking alarms according to specific criteria.
o 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", "high-disk-utilization".
o Management System: The alarm management application that consumes
the alarms, i.e., acts as a client.
o Resource: A fine-grained identification of the alarming resource,
for example: an interface, a process.
o System: The system that implements this YANG alarm module, i.e.,
acts as a server. This corresponds to a network device or a
management application that provides a north-bound alarm
interface.
Tree diagrams used in this document follow the notation defined in
[I-D.ietf-netmod-yang-tree-diagrams].
3. Objectives
The objectives for the design of the Alarm Module are:
o Simple to use. If a system supports this module, it shall be
straight-forward to integrate this into a YANG based alarm
manager.
o View alarms as states on resources and not as discrete
notifications.
o Clear definition of "alarm" in order to exclude general events
that should not be forwarded as alarm notifications.
o Clear and precise identification of alarm types and alarm
instances.
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.
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o Address alarm usability requirements. While IETF has not really
addressed alarm management, telecom standards has addressed it
purely from a protocol perspective. The process industry has
published several relevant standards addressing requirements for a
useful alarm interface; [EEMUA], [ISA182]. This alarm module
defines usability requirements as well as a YANG data model.
o Mapping to X.733, which is a requirement for many alarm systems.
Still, keep some of the X.733 concepts out of the core model in
order to make the model small and easy to understand.
4. Alarm Module Concepts
This section defines the fundamental concepts behind the data model.
This section is rooted in the works of Vallin et. al [ALARMSEM].
4.1. Alarm Definition
An alarm signifies an undesirable state in a resource that requires
corrective action.
See Appendix F for more motivation and consequences around this
definition.
4.2. 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 an 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. For example, a system with digital inputs that allows users to
connects detectors (e.g., smoke detector) to the inputs. In this
case it is a configuration action that says that certain connectors
are fire alarms for example. The drawback of this is that there is a
big risk that alarm operators will receive alarm types as a surprise,
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they do not know how to resolve the problem since a defined alarm
procedure does not necessarily exist.
In order to allow for dynamic addition of alarm types the alarm
module also allows for further qualification of the identity based
alarm type using a string.
A vendor or standard can then 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".
For example:
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// 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 run-time configuration
procedure sets the type of alarm detected. This will
be reported in the alarm-type-qualifier.";
}
4.3. Identifying 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 then an instance-
identifier MUST be used with the full path to the object.
This module also allows for alternate naming of the alarming resource
if it is not available in the data tree.
4.4. Identifying Alarm Instances
A primary goal of this alarm module is to remove any ambiguity in how
alarm notifications are mapped to an update of an alarm instance.
X.733 and especially 3GPP were not really clear on this point. This
YANG alarm module states that the tuple (resource, alarm type
identifier, alarm type qualifier) corresponds to a single alarm
instance. This means that alarm notifications for the same resource
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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";
...
}
4.5. Alarm Life-Cycle
The alarm model clearly separates the resource alarm life-cycle from
the operator and administrative life-cycles of an alarm.
o resource alarm life-cycle: the alarm instrumentation that controls
alarm raise, clearance, and severity changes.
o operator alarm life-cycle: operators acting upon alarms with
actions like acknowledgment and closing. Closing an alarm implies
that the operator considers the corrective action performed.
Operators can also shelf alarms in order to avoid nuisance alarms.
o administrative alarm life-cycle: deleting (purging) alarms and
compressing the alarm status change list. This module exposes
operations to manage the administrative life-cycle. The server
may also perform these operations based on other policies, but how
that is done is out of scope for this document.
4.5.1. Resource Alarm Life-Cycle
From a resource perspective, an alarm can have the following life-
cycle: 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 alarm module defines an rpc
"purge" 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
life-cycle:
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+--ro alarm* [resource alarm-type-id alarm-type-qualifier]
...
+--ro is-cleared boolean
+--ro last-changed yang:date-and-time
+--ro perceived-severity severity
+--ro alarm-text alarm-text
+--ro status-change* [time]
+--ro time yang:date-and-time
+--ro perceived-severity severity
+--ro alarm-text alarm-text
For every status change from the resource perspective a row is added
to the "status-change" list. The last status values are also
represented at leafs for the alarm. Note well that the alarm
severity does not include "cleared", alarm clearance is a flag.
An alarm can therefore look like this: ((GigabitEthernet0/25, link-
alarm,""), false, T, major, "Interface GigabitEthernet0/25 down")
4.5.2. Operator Alarm Life-cycle
Operators can also 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 operator-state
+---w text? string
The operator state for an alarm can be: "none", "ack", "shelved", and
"closed". Alarm deletion (using the rpc "purge-alarms"), can use
this state as a criteria. A closed alarm is an alarm where the
operator has performed any required corrective actions. Closed
alarms are good candidates for being deleted.
4.5.3. Administrative Alarm Life-Cycle
Deleting alarms from the alarm list is considered an administrative
action. This is supported by the "purge-alarms" rpc. The "purge-
alarms" rpc takes a filter as input. The filter selects alarms based
on the operator and resource life-cycle such as "all closed cleared
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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.
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" rpc.
The server may also perform these operations based on other policies,
but how that is done is out of scope for this document.
4.6. Root Cause and Impacted Resources
The general principle of this alarm module is to limit the amount of
alarms. The alarm has two leaf-lists to identify possible impacted
resources and possible root-cause resources. The system should not
send individual alarms for the possible root-cause resources and
impacted resources. These serves as hints only. It is up to the
client application to use this information to present the overall
status.
4.7. 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 this criteria are ignored.
Shelved alarms appear in a dedicated shelved alarm list in order not
to disturb the relevant alarms. Shelved alarms do not generate
notifications.
5. Alarm Data Model
Alarm shelving and operator actions are YANG features so that a
server can select not to support these.
The data model has the following overall structure:
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+--rw alarms
+--rw control
| +--rw max-alarm-status-changes? union
| +--rw notify-status-changes? boolean
| +--rw alarm-shelving {alarm-shelving}?
| ...
+--ro alarm-inventory
| +--ro alarm-type* [alarm-type-id alarm-type-qualifier]
| ...
+--ro 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]
| ...
+--ro shelved-alarms {alarm-shelving}?
+--ro number-of-shelved-alarms? yang:gauge32
+--ro alarm-shelf-last-changed? yang:date-and-time
+--ro shelved-alarm*
[resource alarm-type-id alarm-type-qualifier]
...
5.1. Alarm Control
The "/alarms/control/notify-status-changes" leaf controls if
notifications are sent for all state changes, severity change and
alarm text change, or just for new and cleared alarms.
Every alarm has a list of status changes, this is a circular list.
The length of this list is controlled by "/alarms/control/max-alarm-
status-changes".
5.1.1. Alarm Shelving
The shelving control tree is shown below:
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+--rw alarms
+--rw control
+--rw alarm-shelving {alarm-shelving}?
+--rw shelf* [shelf-name]
+--rw shelf-name string
+--rw resource? resource
+--rw alarm-type-id? alarm-type-id
+--rw alarm-type-qualifier? alarm-type-qualifier
+--rw description? string
Shelved alarms are shown in a dedicated shelved alarm list. The
instrumentation MUST move shelved alarms from the alarm list
(/alarms/alarm-list) to the shelved alarm list (/alarms/shelved-
alarms/). Shelved alarms do not generate any notifications. When
the shelving criteria is removed or changed the alarm list MUST be
updated to the correct actual state of the alarms.
A leaf (/alarms/summary/shelfs-active) in the alarm summary indicates
if there are shelved alarms.
A system can select to not support the shelving feature.
5.2. 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 several reasons:
The system might not instrument all alarm type identities.
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.
The alarm inventory tree is shown below:
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+--rw alarms
+--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* string
+--ro has-clear boolean
+--ro severity-levels* severity
+--ro description string
5.3. Alarm Summary
The alarm summary list summarises alarms per severity; how many
cleared, cleared and closed, and closed. It also gives an indication
if there are shelved alarms.
The alarm summary tree is shown below:
+--rw alarms
+--ro summary
+--ro alarm-summary* [severity]
| +--ro severity severity
| +--ro total? 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}?
5.4. The Alarm List
The alarm list (/alarms/alarm-list) is a function from (resource,
alarm type, alarm type qualifier) to the current alarm state.
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+--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 time-created yang:date-and-time
+--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]
| +--ro resource
| | -> /alarms/alarm-list/alarm/resource
| +--ro alarm-type-id leafref
| +--ro alarm-type-qualifier leafref
+--ro impacted-resource* resource
+--ro root-cause-resource* resource
+--ro is-cleared boolean
+--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 operator-state
+---w text? string
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.
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5.5. The Shelved Alarms List
The shelved alarm list has the same structure as the alarm list
above. It shows all the alarms that matches the shelving criteria
(/alarms/control/alarm-shelving).
5.6. RPCs and Actions
The alarm module supports rpcs and actions to manage the alarms:
"purge-alarms" (rpc): delete alarms according to specific
criteria, for example all cleared alarms older then a specific
date.
"compress-alarms" (rpc): compress the status-change list for the
alarms.
"set-operator-state" (action): change the operator state for an
alarm: for example acknowledge.
5.7. Notifications
The alarm module 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 acknowledge.
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.
6. Alarm YANG Module
<CODE BEGINS> file "ietf-alarms@2017-10-30.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;
}
organization
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"IETF CCAMP Working Group";
contact
"WG Web: <http://tools.ietf.org/wg/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 IRP, ITU-T X.733
and ANSI/ISA-18.2 alarm standards.
Main features of this module include:
* Alarm list:
A list of all alarms. Cleared alarms stay in
the list until explicitly removed.
* 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.
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'.
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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 of the
same alarm, such as clearing an active alarm or changing the
severity of an alarm.
The instrumentation can update 'severity' and 'alarm-text' on an
existing alarm. The above alarm example can therefore look
like:
(('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 acknowledge 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.";
revision 2017-10-30 {
description
"Initial revision.";
reference
"RFC XXXX: YANG Alarm Module";
}
/*
* Features
*/
feature operator-actions {
description
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"This feature means that the systems supports operator states
on alarms.";
}
feature alarm-shelving {
description
"This feature means that the system supports shelving
(blocking) alarms.";
}
feature alarm-history {
description
"This feature means that the alarm list also maintains a
history of state changes for each alarm. For example, if an
alarm toggles between cleared and active 10 times, a list for
that alarm will show those state changes with time-stamps.";
}
/*
* Identities
*/
identity alarm-identity {
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 to be considered to be the same alarm. The alarm
type is a simplification of the different X.733 and 3GPP alarm
IRP alarm 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
textual SNMP Notification var-binds.
Standards and vendors can define sub-identities to clearly
identify specific alarm types.
This identity is abstract and shall not be used for alarms.";
}
/*
* Common types
*/
typedef resource {
type union {
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type instance-identifier {
require-instance false;
}
type yang:object-identifier;
type string;
}
description
"This is an identification of the alarming resource, such as an
interface. It should be as fine-grained as possible both to
guide the operator and to guarantee uniqueness of the
alarms. If a resource has both a config and a state tree
normally this should identify the state tree,
(e.g., /interfaces-state/interface/name).
But if the instrumentation can detect a broken config, this
should be identified as the resource.
If the alarming resource is modelled 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 CIM path, this type will be a string.";
}
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 minor {
value 3;
description
"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
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can be reported, for example, when the detected alarm
condition is not currently degrading the capacity of the
resource.";
}
enum warning {
value 4;
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 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 value 'clear'
is not included. If an alarm is cleared or not is a separate
boolean flag.";
reference
"ITU Recommendation X.733: Information Technology
- Open Systems Interconnection
- System Management: Alarm Reporting Function";
}
typedef severity-with-clear {
type union {
type enumeration {
enum cleared {
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value 1;
description
"The alarm is cleared by the instrumentation.";
}
}
type severity;
}
description
"The severity level of the alarm including clear.
This is used *only* in notifications reporting state changes
for an alarm.";
}
typedef 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 failed";
}
enum closed {
value 3;
description
"Corrective action taken successfully.";
}
enum shelved {
value 4;
description
"Alarm 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.";
}
enum un-shelved {
value 5;
description
"Alarm moved back to alarm-list from shelf.
Alarms 'moved' from /alarms/shelved-alarms/
to /alarms/alarm-list MUST be assigned this
state by the server as the last entry in the
operator-state-change list.";
}
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}
description
"Operator states on an alarm. The 'closed' state indicates
that an operator considers the alarm being resolved. This
is separate from the resource alarm clear flag.";
}
/* Alarm type */
typedef alarm-type-id {
type identityref {
base alarm-identity;
}
description
"Identifies an alarm type. The description of the alarm type
id MUST indicate if the alarm type is abstract or not. 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 can not 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 being part
of the instrumentation and 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
notification representing an alarm state change.";
leaf resource {
type resource;
mandatory true;
description
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"The alarming resource. See also 'alt-resource'.
This could for example be 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
provides 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 OID's, CIM paths or
3GPP Distinguished names for example.";
}
list related-alarm {
key "resource alarm-type-id alarm-type-qualifier";
description
"References to related alarms. Note that the related alarm
might have been removed 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]"
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+ "/alarm-type-id";
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 {
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 {
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
an alarm with the root-cause-resource as 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 {
description
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"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 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 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 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 originates 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-changed {
type yang:date-and-time;
mandatory true;
description
"A timestamp when the alarm status was last changed. Status
changes are changes to 'is-cleared', 'perceived-severity',
and 'alarm-text'.";
}
leaf perceived-severity {
type severity;
mandatory true;
description
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"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 time-stamp in this list MUST
correspond to the leafs 'is-cleared', 'perceived-severity'
and 'alarm-text' for the alarm. The time-stamp for that
entry MUST be equal to the 'last-changed' leaf.
This list is ordered according to the timestamps of
alarm state changes. The last item corresponds to the
latest state change.
The following state changes creates 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;
}
}
/*
* The /alarms data tree
*/
container alarms {
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description
"The top container for this module";
container control {
description
"Configuration to control the alarm behaviour.";
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 boolean;
default false;
description
"This leaf controls whether notifications are sent on all
alarm status updates, e.g., updated perceived-severity or
alarm-text. By default the notifications are only sent
when a new alarm is raised, re-raised after being cleared
and when an alarm is cleared.";
}
container alarm-shelving {
if-feature alarm-shelving;
description
"This list is used to shelve alarms. The server will move
any alarms corresponding to the shelving criteria from the
alarms/alarm-list/alarm list to the
alarms/shelved-alarms/shelved-alarm list. It will also
stop sending notifications for the shelved alarms. The
conditions in the shelf criteria are logically ANDed.
When the shelving criteria is deleted or changed, the
non-matching alarms MUST appear in the
alarms/alarm-list/alarm list according to the real state.
This means that the instrumentation MUST maintain states
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for the shelved alarms. Alarms that match the criteria
shall have an operator-state 'shelved'.";
list shelf {
key shelf-name;
leaf shelf-name {
type string;
description
"An arbitrary name for the alarm shelf.";
}
description
"Each entry defines the criteria for shelving alarms.
Criterias are ANDed.";
leaf resource {
type resource;
description
"Shelve alarms for this resource.";
}
leaf alarm-type-id {
type alarm-type-id;
description
"Shelve alarms for this alarm type identifier.";
}
leaf alarm-type-qualifier {
type alarm-type-qualifier;
description
"Shelve alarms for this alarm type qualifier.";
}
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
"This list contains all possible alarm types for the system.
If the system knows for which resources a a specific alarm
type can appear, this 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.
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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;
mandatory true;
description
"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 string;
description
"Optionally, specifies for which resources the alarm type
is valid. This string is for human consumption but
SHOULD refer to paths in the model.";
}
leaf has-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 not longer active using other
mechanisms. Alarms can lack a corresponding clear due
to missing instrumentation or that there is no logical
corresponding clear state.";
}
leaf-list severity-levels {
type severity;
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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 dynamic state
and not defined statically by the alarm type in order to
provide 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 {
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 {
config false;
description
"This container gives a summary of number of alarms
and shelved alarms";
list alarm-summary {
key severity;
description
"A global summary of all alarms in the system.";
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 cleared {
type yang:gauge32;
description
"For this severity level, the number of alarms that are
cleared.";
}
leaf cleared-not-closed {
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if-feature operator-actions;
type yang:gauge32;
description
"For this severity level, the number of alarms that are
cleared but not closed.";
}
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.";
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}
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.";
}
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, this
is a boolean state in the alarm.
Alarm entries are removed, purged, from the list by an
explicit purge action. For example, delete all alarms
that are cleared and in closed operator-state that are
older than 24 hours. Systems may also remove alarms based
on locally configured policies which is out of scope for
this module.";
leaf time-created {
type yang:date-and-time;
mandatory true;
description
"The time-stamp when this alarm entry was created. This
represents the first time the alarm appeared, it can
also represent that the alarm re-appeared after a purge.
Further state-changes of the same alarm does not change
this leaf, these changes will update the 'last-changed'
leaf.";
}
uses common-alarm-parameters;
uses resource-alarm-parameters;
list operator-state-change {
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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.";
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 operator-state;
mandatory true;
description
"Set this operator state.";
}
leaf text {
type string;
description
"Additional optional textual information.";
}
}
}
}
}
container shelved-alarms {
if-feature alarm-shelving;
config false;
description
"The shelved alarms. Alarms appear here if they match the
criterias 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 can not
be changed.";
leaf number-of-shelved-alarms {
type yang:gauge32;
description
"This object shows the total number of currently
alarms, i.e., the total number of entries
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in the alarm list.";
}
leaf alarm-shelf-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. 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. These changes are reflected in different lists
below the corresponding alarm.";
uses common-alarm-parameters;
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.";
uses operator-parameters;
}
}
}
}
/*
* Operations
*/
rpc compress-alarms {
if-feature alarm-history;
description
"This operation requests the server to compress entries in the
alarm list by removing all but the latest state change for all
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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/alarm-list/alarm/resource";
require-instance false;
}
description
"Compress the alarms with this resource.";
}
leaf alarm-type-id {
type leafref {
path "/alarms/alarm-list/alarm/alarm-type-id";
}
description
"Compress alarms with this alarm-type-id.";
}
leaf alarm-type-qualifier {
type leafref {
path "/alarms/alarm-list/alarm/alarm-type-qualifier";
}
description
"Compress the alarms with this alarm-type-qualifier.";
}
}
output {
leaf compressed-alarms {
type uint32;
description
"Number of compressed alarm entries.";
}
}
}
grouping filter-input {
description
"Grouping to specify a filter construct on alarm information.";
leaf alarm-status {
type enumeration {
enum any {
description
"Ignore alarm clearance status.";
}
enum cleared {
description
"Filter cleared alarms.";
}
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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
"Seconds part";
}
}
case minutes {
leaf minutes {
type uint16;
description
"Minute part";
}
}
case hours {
leaf hours {
type uint16;
description
"Hours part.";
}
}
case days {
leaf days {
type uint16;
description
"Day part";
}
}
case weeks {
leaf weeks {
type uint16;
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description
"Week part";
}
}
}
}
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 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.";
}
description
"Filter based on operator state.";
}
}
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rpc purge-alarms {
description
"This operation requests the server to delete entries from the
alarm list according to the supplied criteria. Typically it
can be 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.";
}
}
}
/*
* 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;
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 if a new
software module is installed, or a new physical card is
inserted";
}
notification operator-action {
if-feature operator-actions;
description
"This notification is used to report that an operator
acted upon an alarm.";
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leaf resource {
type leafref {
path "/alarms/alarm-list/alarm/resource";
require-instance false;
}
description
"The alarming resource.";
}
leaf alarm-type-id {
type leafref {
path "/alarms/alarm-list/alarm"
+ "[resource=current()/../resource]"
+ "/alarm-type-id";
require-instance false;
}
description
"The alarm type identifier for the 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 alarm.";
}
uses operator-parameters;
}
}
<CODE ENDS>
7. X.733 Alarm Mapping Data Model
Many alarm management systems are based on the X.733 alarm standard.
This YANG module allows a mapping from alarm types to X.733 event-
type and probable-cause.
The module augments the alarm inventory, the alarm list and the alarm
notification with X.733 parameters.
The module also supports a feature whereby the alarm manager can
configure the mapping. This might be needed when the default mapping
provided by the system is in conflict with other systems or not
considered good.
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8. X.733 Alarm Mapping YANG Module
This YANG module references [X.733].
<CODE BEGINS> file "ietf-alarms-x733@2017-10-30.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;
}
organization
"IETF CCAMP Working Group";
contact
"WG Web: <http://tools.ietf.org/wg/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 mapping
information. The following structures are augmented with
event type and probable cause:
1) alarm inventory: all possible alarms.
2) alarm: every alarm in the system.
3) alarm notification: notifications indicating alarm state
changes.
The module also optionally allows the alarm management system
to configure the mapping. The mapping does not include a
a corresponding specific problem value. The recommendation is
to use alarm-type-qualifier which serves the same purpose.";
reference
"ITU Recommendation X.733: Information Technology
- Open Systems Interconnection
- System Management: Alarm Reporting Function";
revision 2017-10-30 {
description
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"Initial revision.";
reference
"RFC XXXX: YANG Alarm Module";
}
/*
* Features
*/
feature configure-x733-mapping {
description
"The system supports configurable X733 mapping from
alarm type to 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.";
reference
"ITU Recommendation X.733: Information Technology
- Open Systems Interconnection
- System Management: Alarm Reporting Function";
}
enum quality-of-service-alarm {
value 3;
description
"An alarm of this type is principally associated with a
degradation in the quality of a service.";
reference
"ITU Recommendation X.733: Information Technology
- Open Systems Interconnection
- System Management: Alarm Reporting Function";
}
enum processing-error-alarm {
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value 4;
description
"An alarm of this type is principally associated with a
software or processing fault.";
reference
"ITU Recommendation X.733: Information Technology
- Open Systems Interconnection
- System Management: Alarm Reporting Function";
}
enum equipment-alarm {
value 5;
description
"An alarm of this type is principally associated with an
equipment fault.";
reference
"ITU Recommendation X.733: Information Technology
- Open Systems Interconnection
- System Management: Alarm Reporting Function";
}
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.";
reference
"ITU Recommendation X.733: Information Technology
- Open Systems Interconnection
- System Management: Alarm Reporting Function";
}
enum integrity-violation {
value 7;
description
"An indication that information may have been illegally
modified, inserted or deleted.";
reference
"ITU Recommendation X.736: Information Technology
- Open Systems Interconnection
- System Management: Security Alarm Reporting Function";
}
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.";
reference
"ITU Recommendation X.736: Information Technology
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- Open Systems Interconnection
- System Management: Security Alarm Reporting Function";
}
enum physical-violation {
value 9;
description
"An indication that a physical resource has been violated
in a way that suggests a security attack.";
reference
"ITU Recommendation X.736: Information Technology
- Open Systems Interconnection
- System Management: Security Alarm Reporting Function";
}
enum security-service-or-mechanism-violation {
value 10;
description
"An indication that a security attack has been detected by
a security service or mechanism.";
reference
"ITU Recommendation X.736: Information Technology
- Open Systems Interconnection
- System Management: Security Alarm Reporting Function";
}
enum time-domain-violation {
value 11;
description
"An indication that an event has occurred at an unexpected
or prohibited time.";
reference
"ITU Recommendation X.736: Information Technology
- Open Systems Interconnection
- System Management: Security Alarm Reporting Function";
}
}
description
"The event types as defined by X.733 and X.736. The use of the
term 'event' is a bit confusing. In an alarm context these
are top level alarm types.";
}
/*
* Groupings
*/
grouping x733-alarm-parameters {
description
"Common X.733 parameters for alarms.";
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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.";
}
}
grouping x733-alarm-definition-parameters {
description
"Common X.733 parameters for alarm definitions.";
leaf event-type {
type event-type;
description
"The alarm type has this X.733/X.736 event type.";
}
leaf probable-cause {
type uint32;
description
"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 manager.";
}
}
/*
* Add X.733 parameters to the alarm definitions, alarms,
* and notification.
*/
augment "/al:alarms/al:alarm-inventory/al:alarm-type" {
description
"Augment X.733 mapping information to the alarm inventory.";
uses x733-alarm-definition-parameters;
}
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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 over-ride 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;
}
augment "/al:alarm-notification" {
description
"Augment X.733 information to the alarm notification.";
uses x733-alarm-parameters;
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}
}
<CODE ENDS>
9. Security Considerations
None.
10. Acknowledgements
The author wishes to thank Viktor Leijon and Johan Nordlander for
their valuable input on forming the alarm model.
11. References
11.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, <https://www.rfc-
editor.org/info/rfc2119>.
[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>.
[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>.
[X.733] International Telecommunications Union, "Information
Technology - Open Systems Interconnection - Systems
Management: Alarm Reporting Function",
ITU-T Recommendation X.733, 1992.
11.2. Informative References
[ALARMIRP]
3GPP, "Telecommunication management; Fault Management;
Part 2: Alarm Integration Reference Point (IRP):
Information Service (IS)", 3GPP TS 32.111-2 3.4.0, March
2005.
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[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, John Wiley and Sons, Ltd,
http://dx.doi.org/10.1002/nem.800", March 2012.
[EEMUA] EEMUA Publication No. 191 Engineering Equipment and
Materials Users Association, London, 2 edition., "Alarm
Systems: A Guide to Design, Management and Procurement.",
2007.
[I-D.ietf-netmod-yang-tree-diagrams]
Bjorklund, M. and L. Berger, "YANG Tree Diagrams", draft-
ietf-netmod-yang-tree-diagrams-02 (work in progress),
October 2017.
[ISA182] International Society of Automation,ISA, "ANSI/ISA-
18.2-2009 Management of Alarm Systems for the Process
Industries", 2009.
[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>.
[X.736] International Telecommunications Union, "Information
Technology - Open Systems Interconnection - Systems
Management: Security alarm reporting function",
ITU-T Recommendation X.736, 1992.
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.
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module example-xyz-alarms {
namespace "urn:example:xyz-alarms";
prefix xyz-al;
import ietf-alarms {
prefix al;
}
identity xyz-alarms {
base al:alarm-identity;
}
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;
}
}
Appendix B. Alarm Inventory Example
This shows an alarm inventory, it shows one alarm type defined only
with the identifier, and another 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-identity' to "environmental-alarm".
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<alarms xmlns="urn:ietf:params:xml:ns:yang:ietf-alarms"
xmlns:xyz-al="urn:example:xyz-alarms">
<alarm-inventory>
<alarm-type>
<alarm-type-id>xyz-al:link-alarm</alarm-type-id>
<alarm-type-qualifier/>
<has-clear>true</has-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>
<has-clear>true</has-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>2015-04-08T08:39:50.00Z</last-changed>
<alarm>
<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>2015-04-08T08:39:50.00Z</time-created>
<is-cleared>false</is-cleared>
<alt-resource>1.3.6.1.2.1.2.2.1.1.17</alt-resource>
<last-changed>2015-04-08T08:39:40.00Z</last-changed>
<perceived-severity>major</perceived-severity>
<alarm-text>
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Link operationally down but administratively up
</alarm-text>
<status-change>
<time>2015-04-08T08:39:40.00Z</time>
<perceived-severity>major</perceived-severity>
<alarm-text>
Link operationally down but administratively up
</alarm-text>
</status-change>
<status-change>
<time>2015-04-08T08:30:00.00+00:00</time>
<perceived-severity>cleared</perceived-severity>
<alarm-text>
Link operationally up and administratively up
</alarm-text>
</status-change>
<status-change>
<time>2015-04-08T08:20:10.00+00:00</time>
<perceived-severity>major</perceived-severity>
<alarm-text>
Link operationally down but administratively up
</alarm-text>
</status-change>
<operator-state-change>
<time>2015-04-08T08:39:50.00Z</time>
<state>ack</state>
<operator>joe</operator>
<text>Will investigate, ticket TR764999</text>
</operator-state-change>
</alarm>
</alarm-list>
</alarms>
Appendix D. Alarm Shelving Example
This example shows how to shelf alarms. We shelf alarms related to
the smoke-detectors since they are being installed and tested. We
also shelf all alarms from FastEthernet1/0.
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<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>
<shelf-name>FE10</shelf-name>
<resource>
/dev:interfaces/dev:interface[name='FastEthernet1/0']
</resource>
</shelf>
<shelf>
<shelf-name>detectortest</shelf-name>
<alarm-type-id>xyz-al:environmental-alarm</alarm-type-id>
<alarm-type-qualifier>smoke-alarm</alarm-type-qualifier>
</shelf>
</alarm-shelving>
</control>
</alarms>
Appendix E. X.733 Mapping Example
This example shows how to map a dynamic alarm type (alarm-type-
identity=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. Background and Usability Requirements
This section gives background information regarding design choices in
the alarm module. It also defines usability requirements for alarms.
Alarm usability is important for an alarm interface. A data-model
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will help in defining the format but if the actual alarms is of low
value we have not gained the goal of alarm management.
The telecommunication domain has standardised an alarm interface in
ITU-T X.733 [X.733]. This continued in mobile networks within the
3GPP organisation [ALARMIRP]. Although SNMP is the dominant
mechanism for monitoring devices, IETF did not early on standardise
an alarm MIB. Instead, management systems interpreted the enterprise
specific traps per MIB and device to build an alarm list. When
finally The Alarm MIB [RFC3877] was published, it had to address the
existence of enterprise traps and map these into alarms. This
requirement led to a MIB that is not always easy to use.
F.1. Alarm Concepts
There are two misconceptions regarding alarms and alarm interfaces
that are important to sort out. The first problem is that alarms are
mixed with events in general. Alarms MUST correspond to an
undesirable state that needs corrective action. Many implementations
of alarm interfaces do not adhere to this principle and just send
events in general. In order to qualify as an alarm, there must exist
a corrective action. If that is not true, it is an event that can go
into logs.
The other misconception is that the term "alarm" refers to the
notification itself. Rather, an alarm is a state of a resource in
the system. The alarm notifications report state changes of the
alarm, such as alarm raise and alarm clear.
"One of the most important principles of alarm management is that an
alarm requires an action. This means that if the operator does not
need to respond to an alarm (because unacceptable consequences do not
occur), then it is not an alarm. Following this cardinal rule will
help eliminate many potential alarm management issues." [ISA182]
F.1.1. Alarm type
Since every alarm has a corresponding corrective action, a vendor can
to prepare a list of available alarms and their corrective actions.
We use the term "alarm type" to refer to every possible alarm that
could be active in the system.
Alarm types are also fundamental in order to provide a state-based
alarm list. The alarm list correlates alarm state changes for the
same alarm type and the same resource into one alarm.
Different alarm interfaces use different mechanisms to define alarm
types, ranging from simple error numbers to more advanced mechanisms
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like the X.733 triplet of event type, probable cause and specific
problem.
A common misunderstanding is that individual alarm notifications are
alarm types. This is not correct; e.g., "link-up" and "link-down"
are two notifications reporting different states for the same alarm
type, "link-alarm".
F.2. Usability Requirements
Common alarm problems and the cause of the problems are summarised in
Table 1. This summary is adopted to networking based on the ISA
[ISA182] and EEMUA [EEMUA] standards.
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+------------------+--------------------------------+---------------+
| Problem | Cause | How this |
| | | module |
| | | address the |
| | | cause |
+------------------+--------------------------------+---------------+
| Alarms are | "Nuisance" alarms (chattering | Strict |
| generated but | alarms and fleeting alarms), | definition of |
| they are ignored | faulty hardware, redundant | alarms |
| by the operator. | alarms, cascading alarms, | requiring |
| | incorrect alarm settings, | corrective |
| | alarms have not been | response. |
| | rationalised, the alarms | Alarm |
| | represent log information | requirements |
| | rather than true alarms. | in Table 2. |
| | | |
| When alarms | Insufficient alarm response | The alarm |
| occur, operators | procedures and not well | inventory |
| do not know how | defined alarm types. | lists all |
| to respond. | | alarm types |
| | | and |
| | | corrective |
| | | actions. |
| | | Alarm |
| | | requirements |
| | | in Table 2. |
| | | |
| The alarm | Nuisance alarms, stale alarms, | The alarm |
| display is full | alarms from equipment not in | definition |
| of alarms, even | service. | and 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- | alarm rate |
| flooded with so | based alarming). | requirements |
| many alarms that | | in Table 3 |
| they do not know | | and Table 4 |
| which ones are | | |
| the most | | |
| important. | | |
+------------------+--------------------------------+---------------+
Table 1: Alarm Problems and Causes
Based upon the above problems EEMUA gives the following definition of
a good alarm:
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+----------------+--------------------------------------------------+
| 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. |
| | |
| Prioritised | Indicating the importance that the operator |
| | deals with the problem. |
| | |
| Understandable | Having a message which 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 2: Definition of a Good Alarm
Vendors SHOULD rationalise all alarms according to above. Another
crucial requirement is acceptable alarm 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 over-demanding. |
| | |
| One per 5 minutes | Manageable. |
| | |
| Less than one per 10 minutes | Very likely to be acceptable. |
+-----------------------------------+-------------------------------+
Table 3: Acceptable Alarm Rates, Steady State
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+----------------------------+--------------------------------------+
| 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 to abandon |
| | the use of the alarm system. |
| | |
| 20-100 | Hard to cope with. |
| | |
| Under 10 | Should be manageable - but may be |
| | difficult if several of the alarms |
| | require a complex operator response. |
+----------------------------+--------------------------------------+
Table 4: Acceptable Alarm Rates, Burst
The numbers in Table 3 and Table 4 are the sum of all alarms for a
network being managed from one alarm console. So every individual
system or 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 2
2. Audit the quality of the alarms. Talk with the operators about
how well the alarm information support 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 2?
3. Analyze and benchmark the performance of the system and compare
it to the recommended metrics in Table 3 and Table 4. Start by
identifying nuisance alarms, standing alarms at normal state and
startup.
Authors' Addresses
Stefan Vallin
Stefan Vallin AB
Email: stefan@wallan.se
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Martin Bjorklund
Cisco
Email: mbj@tail-f.com
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