Network Working Group S. Vallin Internet-Draft Stefan Vallin AB Intended status: Standards Track M. Bjorklund Expires: August 12, 2018 Cisco February 8, 2018 YANG Alarm Module draft-ietf-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 working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on August 12, 2018. Copyright Notice Copyright (c) 2018 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 (http://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 Vallin & Bjorklund Expires August 12, 2018 [Page 1] Internet-Draft YANG Alarm Module February 2018 the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Terminology and Notation . . . . . . . . . . . . . . . . 3 2. Objectives . . . . . . . . . . . . . . . . . . . . . . . . . 4 3. Alarm Module Concepts . . . . . . . . . . . . . . . . . . . . 5 3.1. Alarm Definition . . . . . . . . . . . . . . . . . . . . 5 3.2. Alarm Type . . . . . . . . . . . . . . . . . . . . . . . 5 3.3. Identifying Resource . . . . . . . . . . . . . . . . . . 7 3.4. Identifying Alarm Instances . . . . . . . . . . . . . . . 7 3.5. Alarm Life-Cycle . . . . . . . . . . . . . . . . . . . . 8 3.5.1. Resource Alarm Life-Cycle . . . . . . . . . . . . . . 8 3.5.2. Operator Alarm Life-cycle . . . . . . . . . . . . . . 9 3.5.3. Administrative Alarm Life-Cycle . . . . . . . . . . . 9 3.6. Root Cause and Impacted Resources . . . . . . . . . . . . 10 3.7. Alarm Shelving . . . . . . . . . . . . . . . . . . . . . 10 4. Alarm Data Model . . . . . . . . . . . . . . . . . . . . . . 10 4.1. Alarm Control . . . . . . . . . . . . . . . . . . . . . . 11 4.1.1. Alarm Shelving . . . . . . . . . . . . . . . . . . . 11 4.2. Alarm Inventory . . . . . . . . . . . . . . . . . . . . . 12 4.3. Alarm Summary . . . . . . . . . . . . . . . . . . . . . . 13 4.4. The Alarm List . . . . . . . . . . . . . . . . . . . . . 13 4.5. The Shelved Alarms List . . . . . . . . . . . . . . . . . 15 4.6. RPCs and Actions . . . . . . . . . . . . . . . . . . . . 15 4.7. Notifications . . . . . . . . . . . . . . . . . . . . . . 15 5. Alarm YANG Module . . . . . . . . . . . . . . . . . . . . . . 15 6. X.733 Alarm Mapping Data Model . . . . . . . . . . . . . . . 43 7. X.733 Alarm Mapping YANG Module . . . . . . . . . . . . . . . 43 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 49 9. Security Considerations . . . . . . . . . . . . . . . . . . . 50 10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 51 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 51 11.1. Normative References . . . . . . . . . . . . . . . . . . 51 11.2. Informative References . . . . . . . . . . . . . . . . . 52 Appendix A. Vendor-specific Alarm-Types Example . . . . . . . . 53 Appendix B. Alarm Inventory Example . . . . . . . . . . . . . . 54 Appendix C. Alarm List Example . . . . . . . . . . . . . . . . . 54 Appendix D. Alarm Shelving Example . . . . . . . . . . . . . . . 56 Appendix E. X.733 Mapping Example . . . . . . . . . . . . . . . 56 Appendix F. Background and Usability Requirements . . . . . . . 57 F.1. Alarm Concepts . . . . . . . . . . . . . . . . . . . . . 57 F.1.1. Alarm type . . . . . . . . . . . . . . . . . . . . . 58 F.2. Usability Requirements . . . . . . . . . . . . . . . . . 58 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 61 Vallin & Bjorklund Expires August 12, 2018 [Page 2] Internet-Draft YANG Alarm Module February 2018 1. 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 alarm management application 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 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 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. 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. Vallin & Bjorklund Expires August 12, 2018 [Page 3] Internet-Draft YANG Alarm Module February 2018 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]. 2. 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. o Address alarm usability requirements, see Appendix F. 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 Vallin & Bjorklund Expires August 12, 2018 [Page 4] Internet-Draft YANG Alarm Module February 2018 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 some 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. 3. 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]. 3.1. Alarm Definition An alarm signifies an undesirable state in a resource that requires corrective action. There are two main things to remember from this definition: 1. the definition focuses on leaving out events and logging information in general. Alarms should only be used for undesired states that require action. 2. the definition also focus on alarms as a state on a resource, not the notifications that report the state changes. See Appendix F for more motivation and consequences around this definition. 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 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. Vallin & Bjorklund Expires August 12, 2018 [Page 5] Internet-Draft YANG Alarm Module February 2018 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, 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: Vallin & Bjorklund Expires August 12, 2018 [Page 6] Internet-Draft YANG Alarm Module February 2018 // 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."; } 3.3. 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. 3.4. 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 Vallin & Bjorklund Expires August 12, 2018 [Page 7] Internet-Draft YANG Alarm Module February 2018 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 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 (block/filter) 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. A server SHOULD describe how long it retains cleared/closed alarms: until manually purged or if it has an automatic removal policy. 3.5.1. 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: Vallin & Bjorklund Expires August 12, 2018 [Page 8] Internet-Draft YANG Alarm Module February 2018 +--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") 3.5.2. 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. 3.5.3. 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 Vallin & Bjorklund Expires August 12, 2018 [Page 9] Internet-Draft YANG Alarm Module February 2018 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. 3.6. 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. 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 this criteria are ignored (blocked/filtered). Shelved alarms appear in a dedicated shelved alarm list in order not to disturb the relevant alarms. Shelved alarms do not generate notifications. 4. 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: Vallin & Bjorklund Expires August 12, 2018 [Page 10] Internet-Draft YANG Alarm Module February 2018 +--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] ... 4.1. 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". 4.1.1. Alarm Shelving The shelving control tree is shown below: Vallin & Bjorklund Expires August 12, 2018 [Page 11] Internet-Draft YANG Alarm Module February 2018 +--rw alarms +--rw control +--rw alarm-shelving {alarm-shelving}? +--rw shelf* [name] +--rw name string +--rw resource* resource-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. 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. 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/shelfs-active) in the alarm summary indicates if there are shelved alarms. A system can select to not support the shelving feature. 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 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: Vallin & Bjorklund Expires August 12, 2018 [Page 12] Internet-Draft YANG Alarm Module February 2018 +--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* resource-match +--ro has-clear boolean +--ro severity-levels* severity +--ro description string 4.3. 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}? 4.4. The Alarm List The alarm list (/alarms/alarm-list) is a function from (resource, alarm type, alarm type qualifier) to the current alarm state. Vallin & Bjorklund Expires August 12, 2018 [Page 13] Internet-Draft YANG Alarm Module February 2018 +--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] | +--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 time-created yang:date-and-time +--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 writable-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. Vallin & Bjorklund Expires August 12, 2018 [Page 14] Internet-Draft YANG Alarm Module February 2018 4.5. 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). 4.6. 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. 4.7. 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. 5. Alarm YANG Module This YANG module references [RFC6991]. file "ietf-alarms@2018-02-01.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."; Vallin & Bjorklund Expires August 12, 2018 [Page 15] Internet-Draft YANG Alarm Module February 2018 } organization "IETF CCAMP Working Group"; contact "WG Web: WG List: Editor: Stefan Vallin Editor: Martin Bjorklund "; 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') Vallin & Bjorklund Expires August 12, 2018 [Page 16] Internet-Draft YANG Alarm Module February 2018 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 of the same alarm, e.g., 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. Copyright (c) 2018 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). Vallin & Bjorklund Expires August 12, 2018 [Page 17] Internet-Draft YANG Alarm Module February 2018 The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL', 'SHALL NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED', 'MAY', and 'OPTIONAL' in the module text are to be interpreted as described in RFC 2119 (https://tools.ietf.org/html/rfc2119). This version of this YANG module is part of RFC XXXX (https://tools.ietf.org/html/rfcXXXX); see the RFC itself for full legal notices."; revision 2018-02-01 { description "Initial revision."; reference "RFC XXXX: YANG Alarm Module"; } /* * 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."; } feature alarm-history { description "This feature indicates that 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."; } /* * 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 Vallin & Bjorklund Expires August 12, 2018 [Page 18] Internet-Draft YANG Alarm Module February 2018 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 MUST NOT be used for alarms."; } /* * Common types */ typedef resource { type union { 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 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. If the server supports several models, the presedence should be in the order as given in the union definition."; } typedef resource-match { type union { Vallin & Bjorklund Expires August 12, 2018 [Page 19] Internet-Draft YANG Alarm Module February 2018 type yang:xpath1.0; type yang:object-identifier; type string; } description "This type is used to match resources of type 'resource'. Since the type 'resource' is a union of three different types, the 'resource-match' type is also a union if 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: /if:interfaces/if:interface[if: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 a string, it is interpreted as a W3C regular expression, which matches a resource of type 'string' if the given regular expression matches the resource string. If the type is given as an XPath expressionm it is evaluated in the following XPath context: o The set of namespace declarations are those in scope on the leaf element where this type is used. o The set of variable bindings is empty. o The function library is the core function library Vallin & Bjorklund Expires August 12, 2018 [Page 20] Internet-Draft YANG Alarm Module February 2018 and the functions defined in Section 10 of RFC 7950. o The function library is the core function library o The context node is the root node in the data tree."; } 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 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 { Vallin & Bjorklund Expires August 12, 2018 [Page 21] Internet-Draft YANG Alarm Module February 2018 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 { 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 writable-operator-state { type enumeration { Vallin & Bjorklund Expires August 12, 2018 [Page 22] Internet-Draft YANG Alarm Module February 2018 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."; } } 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 /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 Vallin & Bjorklund Expires August 12, 2018 [Page 23] Internet-Draft YANG Alarm Module February 2018 "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 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 "The alarming resource. See also 'alt-resource'. This could for example be a reference to the alarming Vallin & Bjorklund Expires August 12, 2018 [Page 24] Internet-Draft YANG Alarm Module February 2018 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]" + "/alarm-type-id"; require-instance false; Vallin & Bjorklund Expires August 12, 2018 [Page 25] Internet-Draft YANG Alarm Module February 2018 } 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 "Parameters for an alarm state change. Vallin & Bjorklund Expires August 12, 2018 [Page 26] Internet-Draft YANG Alarm Module February 2018 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 "Timestamp for operator action on alarm."; } Vallin & Bjorklund Expires August 12, 2018 [Page 27] Internet-Draft YANG Alarm Module February 2018 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 "The last severity of the alarm. Vallin & Bjorklund Expires August 12, 2018 [Page 28] Internet-Draft YANG Alarm Module February 2018 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 { description "The top container for this module"; Vallin & Bjorklund Expires August 12, 2018 [Page 29] Internet-Draft YANG Alarm Module February 2018 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 "The alarm-shelving/shelf list is used to shelve (block/filter) 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 for the shelved alarms. Alarms that match the criteria Vallin & Bjorklund Expires August 12, 2018 [Page 30] Internet-Draft YANG Alarm Module February 2018 shall have an operator-state 'shelved'. When the shelf configuration will remove an alarm from the shelf the server shall add an operator state 'unshelved'"; list shelf { key "name"; leaf name { type string; description "An arbitrary name for the alarm shelf."; } description "Each entry defines the criteria for shelving alarms. Criterias are ANDed. If no criteria are specified, all alarms will be shelved."; leaf-list resource { type resource-match; description "Shelve alarms for matching resources."; } 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."; } leaf alarm-type-qualifier-match { type string; description "A W3C regular expression that is used to match an alarm type qualifier. Shelve all alarms that matches this regular expression for the 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 Vallin & Bjorklund Expires August 12, 2018 [Page 31] Internet-Draft YANG Alarm Module February 2018 "This 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, 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. 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 "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 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 Vallin & Bjorklund Expires August 12, 2018 [Page 32] Internet-Draft YANG Alarm Module February 2018 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; 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"; 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."; } Vallin & Bjorklund Expires August 12, 2018 [Page 33] Internet-Draft YANG Alarm Module February 2018 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."; } 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 Vallin & Bjorklund Expires August 12, 2018 [Page 34] Internet-Draft YANG Alarm Module February 2018 "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."; } 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."; uses common-alarm-parameters; 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 Vallin & Bjorklund Expires August 12, 2018 [Page 35] Internet-Draft YANG Alarm Module February 2018 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 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; } 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."; } } } } } container shelved-alarms { if-feature alarm-shelving; config false; description "The shelved alarms. Alarms appear here if they match the Vallin & Bjorklund Expires August 12, 2018 [Page 36] Internet-Draft YANG Alarm Module February 2018 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 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; 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 Vallin & Bjorklund Expires August 12, 2018 [Page 37] Internet-Draft YANG Alarm Module February 2018 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 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 { Vallin & Bjorklund Expires August 12, 2018 [Page 38] Internet-Draft YANG Alarm Module February 2018 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."; } 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 Vallin & Bjorklund Expires August 12, 2018 [Page 39] Internet-Draft YANG Alarm Module February 2018 "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; 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 Vallin & Bjorklund Expires August 12, 2018 [Page 40] Internet-Draft YANG Alarm Module February 2018 "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."; } } 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 Vallin & Bjorklund Expires August 12, 2018 [Page 41] Internet-Draft YANG Alarm Module February 2018 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."; 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."; Vallin & Bjorklund Expires August 12, 2018 [Page 42] Internet-Draft YANG Alarm Module February 2018 } uses operator-parameters; } } 6. 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. 7. X.733 Alarm Mapping YANG Module This YANG module references [X.733]. 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: WG List: Editor: Stefan Vallin Editor: Martin Bjorklund "; Vallin & Bjorklund Expires August 12, 2018 [Page 43] Internet-Draft YANG Alarm Module February 2018 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 "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 { Vallin & Bjorklund Expires August 12, 2018 [Page 44] Internet-Draft YANG Alarm Module February 2018 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 { 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 Vallin & Bjorklund Expires August 12, 2018 [Page 45] Internet-Draft YANG Alarm Module February 2018 - 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 - 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 Vallin & Bjorklund Expires August 12, 2018 [Page 46] Internet-Draft YANG Alarm Module February 2018 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."; 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 Vallin & Bjorklund Expires August 12, 2018 [Page 47] Internet-Draft YANG Alarm Module February 2018 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; } 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; Vallin & Bjorklund Expires August 12, 2018 [Page 48] Internet-Draft YANG Alarm Module February 2018 } } 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; } } 8. IANA Considerations This document registers a URI in the IETF XML registry [RFC3688]. Following the format in RFC 3688, the following registration is requested to be made. URI: urn:ietf:params:xml:ns:yang:ietf-alarms Registrant Contact: The IESG. XML: N/A, the requested URI is an XML namespace. This document registers a YANG module in the YANG Module Names registry [RFC6020]. name: ietf-alarms namespace: urn:ietf:params:xml:ns:yang:ietf-alarms prefix: al reference: RFC XXXX Vallin & Bjorklund Expires August 12, 2018 [Page 49] Internet-Draft YANG Alarm Module February 2018 9. Security Considerations The YANG module specified in this document defines a schema for data that is designed to be accessed via network management protocols such as NETCONF [RFC6241] or RESTCONF [RFC8040]. The lowest NETCONF layer is the secure transport layer, and the mandatory-to-implement secure transport is Secure Shell (SSH) [RFC6242]. The lowest RESTCONF layer is HTTPS, and the mandatory-to-implement secure transport is TLS [RFC5246]. The NETCONF access control model [RFC6536] 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. There are a number of data nodes defined in this YANG module 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 and their sensitivity/vulnerability: /alarms/control/notify-status-change: This leaf controls whether an alarm should notify only raise and clear or all severity level changes. Unauthorized access to 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 and not be part of the alarm list. 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: purge-alarms: This RPC deletes alarms from the alarm list. Unauthorized use of this RPC could jeopardize the alarm management procedures since the deleted alarms may be vital for the alarm management application. Vallin & Bjorklund Expires August 12, 2018 [Page 50] Internet-Draft YANG Alarm Module February 2018 10. 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. 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, . [RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688, DOI 10.17487/RFC3688, January 2004, . [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security (TLS) Protocol Version 1.2", RFC 5246, DOI 10.17487/RFC5246, August 2008, . [RFC6020] Bjorklund, M., Ed., "YANG - A Data Modeling Language for the Network Configuration Protocol (NETCONF)", RFC 6020, DOI 10.17487/RFC6020, October 2010, . [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, . [RFC6242] Wasserman, M., "Using the NETCONF Protocol over Secure Shell (SSH)", RFC 6242, DOI 10.17487/RFC6242, June 2011, . [RFC6991] Schoenwaelder, J., Ed., "Common YANG Data Types", RFC 6991, DOI 10.17487/RFC6991, July 2013, . [RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language", RFC 7950, DOI 10.17487/RFC7950, August 2016, . Vallin & Bjorklund Expires August 12, 2018 [Page 51] Internet-Draft YANG Alarm Module February 2018 [RFC8040] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . [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. [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-05 (work in progress), January 2018. [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, . Vallin & Bjorklund Expires August 12, 2018 [Page 52] Internet-Draft YANG Alarm Module February 2018 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; } } Vallin & Bjorklund Expires August 12, 2018 [Page 53] Internet-Draft YANG Alarm Module February 2018 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". xyz-al:link-alarm /dev:interfaces/dev:interface true Link failure, operational state down but admin state up xyz-al:environmental-alarm smoke-alarm true Connected smoke detector to digital input Appendix C. Alarm List Example In this example we show an alarm that has toggled [major, clear, major]. An operator has acknowledged the alarm. 1 2015-04-08T08:39:50.00Z Vallin & Bjorklund Expires August 12, 2018 [Page 54] Internet-Draft YANG Alarm Module February 2018 /dev:interfaces/dev:interface[name='FastEthernet1/0'] xyz-al:link-alarm 2015-04-08T08:39:50.00Z false 1.3.6.1.2.1.2.2.1.1.17 2015-04-08T08:39:40.00Z major Link operationally down but administratively up major Link operationally down but administratively up cleared Link operationally up and administratively up major Link operationally down but administratively up ack joe Will investigate, ticket TR764999 Vallin & Bjorklund Expires August 12, 2018 [Page 55] Internet-Draft YANG Alarm Module February 2018 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. FE10 /dev:interfaces/dev:interface[name='FastEthernet1/0'] detectortest xyz-al:environmental-alarm smoke-alarm 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. Vallin & Bjorklund Expires August 12, 2018 [Page 56] Internet-Draft YANG Alarm Module February 2018 xyz-al:environmental-alarm smoke-alarm quality-of-service-alarm 777 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 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 Vallin & Bjorklund Expires August 12, 2018 [Page 57] Internet-Draft YANG Alarm Module February 2018 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 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. Vallin & Bjorklund Expires August 12, 2018 [Page 58] Internet-Draft YANG Alarm Module February 2018 +------------------+--------------------------------+---------------+ | 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: Vallin & Bjorklund Expires August 12, 2018 [Page 59] Internet-Draft YANG Alarm Module February 2018 +----------------+--------------------------------------------------+ | 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 Vallin & Bjorklund Expires August 12, 2018 [Page 60] Internet-Draft YANG Alarm Module February 2018 +----------------------------+--------------------------------------+ | 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 Vallin & Bjorklund Expires August 12, 2018 [Page 61] Internet-Draft YANG Alarm Module February 2018 Martin Bjorklund Cisco Email: mbj@tail-f.com Vallin & Bjorklund Expires August 12, 2018 [Page 62]