IETF R. Price, Ed. Internet-Draft Network UPS Tools Project Intended status: Informational 26 February 2022 Expires: 30 August 2022 Uninterruptible Power Supply (UPS) Management Protocol -- Commands and Responses draft-rprice-ups-management-protocol-07 Abstract This document describes the command/response protocol currently used in the management of Uninterruptible Power Supply (UPS) units and other power devices often deployed in small offices, and in IT installations subject to an erratic public power supply. The UPS units typically interface to an Attachment Daemon in the system they protect. This daemon is in turn polled by a Management Daemon which notifies users and system administrators of power supply incidents, and automates system shutdown decisions. The commands and responses described by this document are exchanged between the UPS Attachment Daemon and the Management Daemon. Current practice when this text was written risks weak security and this is addressed in the Security Considerations sections of this document. 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 https://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 30 August 2022. Copyright Notice Copyright (c) 2022 IETF Trust and the persons identified as the document authors. All rights reserved. Price Expires 30 August 2022 [Page 1] Internet-Draft UPS management protocol February 2022 This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/ license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Revised BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Revised BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4 1.1. How to Read this Document . . . . . . . . . . . . . . . . 4 1.2. Current Practice . . . . . . . . . . . . . . . . . . . . 5 1.3. Requirements Language . . . . . . . . . . . . . . . . . . 5 1.4. Additional Information . . . . . . . . . . . . . . . . . 5 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 2.1. Attachment Daemon . . . . . . . . . . . . . . . . . . . . 5 2.2. Administrative User . . . . . . . . . . . . . . . . . . . 6 2.3. Driver . . . . . . . . . . . . . . . . . . . . . . . . . 6 2.4. Event . . . . . . . . . . . . . . . . . . . . . . . . . . 6 2.5. Instant Command . . . . . . . . . . . . . . . . . . . . . 6 2.6. Management Daemon . . . . . . . . . . . . . . . . . . . . 7 2.7. NUT (Network UPS Tools) Software Project . . . . . . . . 7 2.8. Primary . . . . . . . . . . . . . . . . . . . . . . . . . 7 2.9. Secondary . . . . . . . . . . . . . . . . . . . . . . . . 7 2.10. Session . . . . . . . . . . . . . . . . . . . . . . . . . 8 2.11. UPS Status . . . . . . . . . . . . . . . . . . . . . . . 8 2.12. UPS Variable . . . . . . . . . . . . . . . . . . . . . . 8 3. Protocol Overview . . . . . . . . . . . . . . . . . . . . . . 8 4. Protocol Specification . . . . . . . . . . . . . . . . . . . 11 4.1. Notation Used in this Specification . . . . . . . . . . . 11 4.2. Commands . . . . . . . . . . . . . . . . . . . . . . . . 12 4.2.1. ATTACH . . . . . . . . . . . . . . . . . . . . . . . 12 4.2.2. DETACH . . . . . . . . . . . . . . . . . . . . . . . 13 4.2.3. FSD . . . . . . . . . . . . . . . . . . . . . . . . . 13 4.2.4. GET . . . . . . . . . . . . . . . . . . . . . . . . . 14 4.2.4.1. GET CMDDESC . . . . . . . . . . . . . . . . . . . 14 4.2.4.2. GET DESC . . . . . . . . . . . . . . . . . . . . 14 4.2.4.3. GET NUMATTACH . . . . . . . . . . . . . . . . . . 14 4.2.4.4. GET TYPE . . . . . . . . . . . . . . . . . . . . 15 4.2.4.5. GET UPSDESC . . . . . . . . . . . . . . . . . . . 16 4.2.4.6. GET VAR . . . . . . . . . . . . . . . . . . . . . 16 4.2.5. HELP . . . . . . . . . . . . . . . . . . . . . . . . 16 4.2.6. INSTCMD . . . . . . . . . . . . . . . . . . . . . . . 17 4.2.7. LIST . . . . . . . . . . . . . . . . . . . . . . . . 17 4.2.7.1. LIST CLIENT . . . . . . . . . . . . . . . . . . . 18 4.2.7.2. LIST CMD . . . . . . . . . . . . . . . . . . . . 18 Price Expires 30 August 2022 [Page 2] Internet-Draft UPS management protocol February 2022 4.2.7.3. LIST ENUM . . . . . . . . . . . . . . . . . . . . 19 4.2.7.4. LIST RANGE . . . . . . . . . . . . . . . . . . . 19 4.2.7.5. LIST RW . . . . . . . . . . . . . . . . . . . . . 20 4.2.7.6. LIST UPS . . . . . . . . . . . . . . . . . . . . 21 4.2.7.7. LIST VAR . . . . . . . . . . . . . . . . . . . . 21 4.2.8. PASSWORD . . . . . . . . . . . . . . . . . . . . . . 22 4.2.9. PRIMARY . . . . . . . . . . . . . . . . . . . . . . . 22 4.2.10. PROTVER . . . . . . . . . . . . . . . . . . . . . . . 23 4.2.11. SET . . . . . . . . . . . . . . . . . . . . . . . . . 23 4.2.12. STARTTLS . . . . . . . . . . . . . . . . . . . . . . 24 4.2.13. USERNAME . . . . . . . . . . . . . . . . . . . . . . 24 4.2.14. VER . . . . . . . . . . . . . . . . . . . . . . . . . 24 4.3. Summary of Responses . . . . . . . . . . . . . . . . . . 25 4.3.1. Response when Command Succeeds . . . . . . . . . . . 25 4.3.2. Error Responses . . . . . . . . . . . . . . . . . . . 26 5. Statuses and Events . . . . . . . . . . . . . . . . . . . . . 30 5.1. Status Symbols . . . . . . . . . . . . . . . . . . . . . 30 5.2. Events . . . . . . . . . . . . . . . . . . . . . . . . . 32 6. Security Considerations . . . . . . . . . . . . . . . . . . . 34 6.1. Agent Verification . . . . . . . . . . . . . . . . . . . 35 6.2. Current Encryption Practice . . . . . . . . . . . . . . . 35 6.2.1. Secure Tunnels . . . . . . . . . . . . . . . . . . . 35 6.3. Current General Security Practice . . . . . . . . . . . . 36 6.4. Security Needs . . . . . . . . . . . . . . . . . . . . . 36 6.4.1. Shims . . . . . . . . . . . . . . . . . . . . . . . . 37 6.4.1.1. Attachment Daemon Shim . . . . . . . . . . . . . 37 6.4.1.2. Management Daemon Shim . . . . . . . . . . . . . 37 6.4.2. TLS Tunnels . . . . . . . . . . . . . . . . . . . . . 38 6.4.3. VPN . . . . . . . . . . . . . . . . . . . . . . . . . 38 6.4.4. VLAN . . . . . . . . . . . . . . . . . . . . . . . . 38 6.4.5. Long Term: Enforced Secure Communication . . . . . . 38 6.4.6. Firewalls . . . . . . . . . . . . . . . . . . . . . . 39 6.5. Administrative Security . . . . . . . . . . . . . . . . . 39 6.5.1. Management of Administrative Users . . . . . . . . . 40 6.5.2. An Administrative User of a Client Management Daemon . . . . . . . . . . . . . . . . . . . . . . . 41 6.5.2.1. An Administrative User Logs into a Short Session . . . . . . . . . . . . . . . . . . . . . . 42 6.5.2.2. An Administrative User Logs into a Long Session . . . . . . . . . . . . . . . . . . . . . . 42 7. Codepoint Management . . . . . . . . . . . . . . . . . . . . 42 7.1. Namespaces used by Command, Responses, Statuses and Variables . . . . . . . . . . . . . . . . . . . . . . . . 43 7.2. Port Name and Number used to Manage UPS Units . . . . . . 43 7.2.1. Port nut/3493 . . . . . . . . . . . . . . . . . . . . 43 7.2.2. Port ups/401 . . . . . . . . . . . . . . . . . . . . 44 7.2.3. NUT Project Requirement . . . . . . . . . . . . . . . 44 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 45 Price Expires 30 August 2022 [Page 3] Internet-Draft UPS management protocol February 2022 8.1. Port Name ups: Reference to this Document . . . . . . . . 45 8.2. Change of Registrant . . . . . . . . . . . . . . . . . . 45 9. Implementation Status . . . . . . . . . . . . . . . . . . . . 45 9.1. An Implementation of the Attachment Daemon . . . . . . . 46 9.2. Implementations of the Management Daemon . . . . . . . . 46 9.3. Inclusion in Software Distributions . . . . . . . . . . . 46 9.4. Recommended Minimum Support . . . . . . . . . . . . . . . 47 9.4.1. Desktop PC Variables . . . . . . . . . . . . . . . . 47 9.4.2. Unattended Servers, Additional Variables . . . . . . 47 9.4.3. Commands . . . . . . . . . . . . . . . . . . . . . . 47 10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 48 11. Normative References . . . . . . . . . . . . . . . . . . . . 48 12. Informative References . . . . . . . . . . . . . . . . . . . 48 Appendix A. Variables . . . . . . . . . . . . . . . . . . . . . 50 A.1. Typical UPS Variables . . . . . . . . . . . . . . . . . . 51 A.2. Typical UPS Readable and Writable Variables . . . . . . . 54 A.3. Typical UPS Instant Commands . . . . . . . . . . . . . . 56 Appendix B. The Shutdown Story for System and UPS . . . . . . . 56 Appendix C. Technical Terms: Historical Differences . . . . . . 58 Appendix D. Change Log . . . . . . . . . . . . . . . . . . . . . 59 D.1. Changes in Version 01 . . . . . . . . . . . . . . . . . . 59 D.2. Changes in Version 02 . . . . . . . . . . . . . . . . . . 59 D.3. Changes in Version 03 . . . . . . . . . . . . . . . . . . 59 D.4. Changes in Version 04 . . . . . . . . . . . . . . . . . . 60 D.5. Changes in Version 05 . . . . . . . . . . . . . . . . . . 60 D.6. Changes in Version 06 . . . . . . . . . . . . . . . . . . 63 D.7. Changes in Version 07 . . . . . . . . . . . . . . . . . . 63 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 64 1. Introduction 1.1. How to Read this Document The editor recommends that you read the HTML version of this document. It renders the protocol symbols such as OL correctly without quotation marks. To lighten the text, the term "UPS" is used when "Managed Power Device" would be more complete. The reader should understand the simple "UPS" to include other managed power devices. The statuses and events appearing in this document are named with short text-form names, some of which are abbreviations. A full list of the statuses can be found in section Status Symbols (5.1) while the events are listed in section Events (5.2). Price Expires 30 August 2022 [Page 4] Internet-Draft UPS management protocol February 2022 This document refers to the "public power supply". Other texts frequently refer to "utility power", "input source power" or even "wall power". 1.2. Current Practice This document describes UPS management techniques and current UPS management practice published by the NUT Project (2.7) which has been operational since 1998. Appendix The Shutdown Story (B) describes the current UPS management practice for performing a managed shutdown of unattended infrastructure after an unscheduled failure of the public power supply to minimise the risk of corruption to data processed by this infrastructure. Since May 2002, the protocol described by this document has been operating on IANA port nut/3493 running over TCP. 1.3. Requirements Language The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 [RFC2119]. 1.4. Additional Information Additional information about the NUT Project (2.7) is available in the project documentation [Documentation]. Requests for further information about this protocol and related technical matters may be addressed to the mailing list [nut-upsuser] of the NUT Project (2.7). 2. Terminology The following technical terms appear in this document. They are listed in alphabetical order. 2.1. Attachment Daemon The Attachment Daemon retrieves status from the UPS and sends commands to it often through a Driver (2.3) specific to the hardware model and the connection medium, e.g., USB, serial. It maintains an abstracted view of the hardware through the use of hardware statuses (2.11). A Management Daemon (2.6) may consult the abstracted view using the commands described in this document. An Attachment Daemon is launched as system user "root" to allow direct access to the hardware (e.g. /proc, /dev). For better security, the daemon then drops privilege to run as a detached software service for a dedicated system user. Price Expires 30 August 2022 [Page 5] Internet-Draft UPS management protocol February 2022 See section (9.4) for details of the recommended minimum support of variables which calls for Attachment Daemon support of statuses (2.11) OB, OL, LB and FSD. 2.2. Administrative User In current practice, the commands and other functions offered by the Attachment Daemon (2.1) to each Management Daemon (2.6) are made available to a set of Management Daemon (2.6) users which authenticate to the Attachment Daemon (2.1) with basic credentials (username and password). These users are not system users, they are specific to an Attachment Daemon (2.1) and are listed in a text file (currently upsd.users) which is read by the Attachment Daemon (2.1) and which assigns to each of them the password, instant commands (2.5) and actions which are allowed, together with the Primary (2.8) or Secondary (2.9) status of the Management Daemon (2.6). For details, see section (6.5.1). Typically a high-level user will be able to send command FSD (4.2.3) but a low-level user might only be allowed to access the test panel. The security provisions for administrative users are discussed in section 6.5. 2.3. Driver A Driver is that part of an Attachment Daemon which is specific to the UPS hardware, the connection medium and the connection protocol, e.g., USB, serial. In current practice the Attachment Daemon has a driver for each hardware interface type it supports. Although this document considers the driver to be part of the Attachment Daemon, current practice is to see it as a separate software unit running as a daemon "in front of" the Attachment Daemon. The protocol for data exchange between the Driver and the Attachment Daemon is outside the scope of this document. 2.4. Event A UPS Event occurs in the Management Daemon (2.6) when a change in UPS status (2.11) is received from the Attachment Daemon (2.1). This event is internal to the Management Daemon (2.6). See Section 5.2, Paragraph 1. 2.5. Instant Command A command which when sent to the Attachment Daemon (2.1) is passed to the driver and sent to the hardware without any configured delay to perform a function. For example INSTCMD su700 test.panel.start . See INSTCMD (4.2.6). Price Expires 30 August 2022 [Page 6] Internet-Draft UPS management protocol February 2022 2.6. Management Daemon The Management Daemon is primarily responsible for managing the hardware and orchestrating system-wide actions after a power event. Using commands sent to the Attachment Daemon (2.1) it follows the status of the UPS and determines when UPS events occur. It takes decisions based on the events, such as calling for a system shutdown (B). Although the term includes the word "daemon" nothing requires that it be implemented as a detached software service. The Management Daemon may also provide administrative functions such as a graphic interface to view the hardware activity. 2.7. NUT (Network UPS Tools) Software Project The primary goal of the NUT software project [NUT] is to provide support for Power Devices, such as Uninterruptible Power Supplies. The Project has been in operation since 1998 with a major rework in 2003. It operates through a user mailing list [nut-upsuser], a developer mailing list [nut-upsdev], a web site [NUT] and a GitHub repository [nut-repository]. See the history of the project [History]. 2.8. Primary When a power device such as a UPS unit supplies power to more than one system, the computer running the driver is known as the primary. The others are secondaries. See figure 4. Common current practice for system administrators is to consider the Management Daemon (2.6) in the primary to be the Primary Management Daemon which is in charge of the shutdown of all the systems powered by the UPS. The Primary Management Daemon sets status symbol FSD to order the secondaries to shut down. Note: Historically, the primary was known as the "Master". 2.9. Secondary When a hardware device such as a UPS unit supplies power to more than one system, the system which communicates directly with the UPS unit e.g. using a USB, RS232, or network connection, is known as the Primary (2.8). The other are secondaries. There is no Attachment Daemon (2.1) in a secondary. See figure 4. Common current practice for system administrators is to consider the Management Daemon (2.6) in a secondary to be a Secondary Management Daemon which understands status symbol FSD as an order to shut down. Note: Historically, the secondary was known as the "Slave". Price Expires 30 August 2022 [Page 7] Internet-Draft UPS management protocol February 2022 2.10. Session The Management Daemon (2.6) may initiate a TCP session with a specified device such as a UPS known to the Attachment Daemon (2.1). The session structure provides for audit and security as well as access to mission critical UPS functions. For example good practice requires a password protection for an instant command (2.5) which turns off a UPS outlet. Other than the commands and responses used, the details of session management are outside the scope of this document. 2.11. UPS Status The status of a hardware device such as a UPS unit is a symbolic description of the state of the unit. It consists of a space separated list of symbols from the set {ALARM BOOST BYPASS CAL CHRG COMM DISCHRG FSD LB NOCOMM OB OFF OL OVER RB TEST TRIM}. The symbols TICK and TOCK are experimental additions to the statuses and are not in common current practice. See section Status Symbols (5.1) which specifies each of these symbols. See section (9.4) for details of the recommended minimum support of status symbols OB, OL, LB and FSD. 2.12. UPS Variable The metrics and identifiers provided by each UPS are represented by variables giving the value representing that metric or identifier, The UPS variable is an abstraction of the UPS hardware configuration and activity maintained by the Attachment Daemon (2.1). See the appendix (Appendix A, Paragraph 1) which provides examples of variables. For example the variable battery.charge contains the current charge of the UPS battery as a percentage value. Note: Some variables are constants, e.g. battery type, manufacturer. See section (9.4) for details of the recommended minimum support of variables. A full list of possible variables is available in source code file docs/nut-names.txt [gitvars] which serves as the Recording Document. 3. Protocol Overview Figure 1 shows a reference configuration in which the command/ response protocol applies. The UPS shown is representative of all managed power devices, Price Expires 30 August 2022 [Page 8] Internet-Draft UPS management protocol February 2022 "The client" ,--------------, ,--------------, ,-----, | UPS | <-Commands | UPS | | UPS |---| Attachment |---------------| Management | | |===| Daemon | Responses-> | Daemon | /-----\ '--------------' '--------------' UPS Attachment UPS Management System Network System Figure 1: Reference Configuration The reference configuration in figure 1 shows a single UPS unit which has a power supply link (===) and a data link (---) attached to a system running an Attachment Daemon (2.1). The UPS provides power supply protection to the system running the Attachment Daemon. In practice there may be more than one UPS unit, and a unit may provide power protection to more than one system. The figure also shows a single Management Daemon (2.6). In practice there may be more than one Management Daemon, and any one Management Daemon may manage more than one UPS Attachment Daemon. The protocol applies to connections between the Attachment Daemon and the Management daemon which act as *server* and *client* respectively. The Management daemon sends commands over TCP to the Attachment Daemon and receives responses over TCP from that daemon. The two daemons may run in the same system, or may be connected through a local or wide area network. In simple cases, as shown in figure 2, the Attachment Daemon (2.1) and the Management Daemon (2.6) are in the same system, the one protected by the UPS. The commands and responses are exchanged through an internal loopback interface. "The client" ,--------------------,---------------------, ,-----, | UPS <-Commands UPS | | UPS |---| Attachment | Management | | |===| Daemon Responses-> Daemon | /-----\ '--------------------'---------------------' Internal loopback UPS Attachment and Management System Figure 2: Simplified single-system configuration The reference configuration does not require any specific design. For example figure 3 shows an arrangement in which the Attachment Daemon (2.1) is closely associated with, or even included in the UPS Price Expires 30 August 2022 [Page 9] Internet-Draft UPS management protocol February 2022 system setup. This is becoming more prevalent with the availability of low cost processors able to run the Attachment Daemon (2.1) thereby effectively creating a network attached UPS running a published protocol. "The client" ,-----,------------, ,--------------, | | UPS | <-Commands | UPS | | UPS - Attachment |---------------| Management | | | Daemon | Responses-> | Daemon | /-----'------------\ '--------------' UPS Attachment UPS Management System Network System Figure 3: UPS and Attachment Daemon integration As the power requirements for processors decrease, it is becoming increasingly common to use a single UPS to protect multiple systems as shown in figure 4. However there is only one data line (---) from the UPS to the Primary (2.8) system. The others have only power connections (===) to the UPS, and are known as Secondaries (2.9). A Secondary (2.9) does not run an Attachment Daemon (2.1), it connects over a network to the Attachment Daemon (2.1) in the primary. Figure 4 shows the Attachment Daemon (2.1) and the primary Management Daemon (2.6) in the same system. This is common practice but it is not a technical requirement. "The client" ,--------------------,---------------------, ,-----, | UPS <-Commands Primary | | |---| Attachment | Management | Primary | |===| Daemon Responses-> Daemon | | | '--------------------'---------------------' | UPS | ^ | | '<-Commands---Responses->, | | v | | ,--------------,-----------------, | |============| | Secondary | /-----\ | | Management | Secondary | | Daemon | '--------------'-----------------' Figure 4: UPS protects multiple systems Price Expires 30 August 2022 [Page 10] Internet-Draft UPS management protocol February 2022 | Note: Should the Primary fail or go off-line, the fate of the | Secondaries depends on the UPS status (2.11) when the Primary | failed. If the UPS had status OL the Secondary continues | operation, but if the UPS had status OB the Secondary may | choose to shut down as a precaution. 4. Protocol Specification This specification includes only the commands and their responses. An implementation of the Attachment Daemon (2.1) has an internal state machine, and some complex implementations of the Management Daemon (2.6) include an internal state machine; for example to assist the system shutdown of a complex installation. The Management Daemon (2.6) is required to remember the previous ups.status value it received from the Attachment Daemon (2.1) and compare it with the next. Other than that the management protocol used between them is effectively stateless. See for example table (5.2) which maps the new ups.status response and the previous ups.status response to an Event (5.2) which is taken as the basis for Management Daemon (2.6) action. 4.1. Notation Used in this Specification The character set used for commands and responses is UTF-8 but current practice is to limit the character set used to the single byte UTF-8 characters 0-127. | Historical note: UTF-8 characters 0-127 were originally known | as the American Standard Code for Information Interchange, US- | ASCII, first published in 1963. Multi-word elements are contained within U+0022 QUOTATION MARK characters for easier parsing. E.g., "UPS on fire". Embedded quotation marks are escaped with U+005C REVERSE SOLIDUS \ often known as backslashes. Embedded backslashes are also escaped by representing them as \\. Commands and responses have no leading or trailing whitespace, and are terminated with a single new line character U+000A LINE FEED (LF). White space within commands and responses is reduced to one U+0020 SPACE (SP). Price Expires 30 August 2022 [Page 11] Internet-Draft UPS management protocol February 2022 4.2. Commands The commands address the UPS to which they apply by where * ::= [@[:]] * is defined by the Attachment Daemon (2.1) configuration files. * The default is localhost * The is the number of the TCP port on which the Attachment Daemon (2.1) is listening. The default is 3493. This is supported by all current Management Daemons (2.6). Examples: myups, UPS-97B@bigserver.example.com Note: Experimental Management Daemons (2.6) use an extended form of in configuration files and in program parameters, where * ::= [:][@[:]] * is an experimental extension to provide for groups of UPSs. It is not in common current practice. * is defined by the Attachment Daemon (2.1) configuration files. * The default is localhost Examples: ups-1@example.com:3493, HB:heartbeat1@example.com:3493 In current usage, the names of commands and subcommands are not case sensitive. For example GET VAR may be written as Get var, but in this specification they are always written in upper case. Similarly, and are not case sensitive. For example UPS341 ups.id may be written as ups341 Ups.Id, but in this specification is always written in lower case. 4.2.1. ATTACH In a configuration such as Figure 4 in which a UPS protects more than one system, the Primary (2.8) Management Daemon (2.6) needs to know how many Secondaries (2.9) are currently "_active_", i.e., powered by the UPS, either from the public power supply or from battery power. The Attachment Daemon (2.1) supports this by keeping a count of all the "_active_" systems powered by a UPS. The count is initialised, one secondary at a time by the ATTACH command, which should be understood as "_count this secondary as active_". ATTACH is one of three commands for Secondary (2.9) counting: command DETACH (4.2.2) decrements the count and a Management Daemon (2.6) may read the count at any time using command NUMATTACH (4.2.4.3). Price Expires 30 August 2022 [Page 12] Internet-Draft UPS management protocol February 2022 The ATTACH command is also sent to the Attachment Daemon (2.1) for the primary so during normal, fully protected operation, the count is 1 for the primary + the number of secondaries. During a full system shutdown, the count drops as each secondary Management Daemon (2.6) executes command DETACH (4.2.2) during its own shutdown. When the count drops to 1, only the primary is "_active_" and it knows that all the secondaries have shut down. Command: ATTACH If the command succeeds, the response is OK, otherwise see the error responses (4.3.2). Note: Historically, this command was known as LOGIN. Since that LOGIN was not the conventional user access to a shell or program the name was changed to avoid confusion. 4.2.2. DETACH This companion command to ATTACH (4.2.1) reduces the count of "active" Secondaries (2.9). It should be understood as "_this secondary is no longer active_", and is usually used during system shutdown to decrement a count of how many Secondaries (2.9) are still "active". Command: DETACH If the command succeeds, the response is OK Goodbye, otherwise see the error responses (4.3.2). Note: Historically, this command was known as LOGOUT. 4.2.3. FSD A Management Daemon (2.6) which is Primary (2.8) and has the required authority, uses this command to set status symbol FSD meaning "Forced Shutdown" in the Attachment Daemon (2.1). In current practice the Primary (2.8) Management Daemon (2.6) uses the symbol to tell the Secondaries (2.9) to shut down. Command: FSD If the command succeeds, the response is OK FSD-SET, otherwise see the error responses (4.3.2). Price Expires 30 August 2022 [Page 13] Internet-Draft UPS management protocol February 2022 In current practice, commands such as FSD are made available only to a privileged administrative user (2.2) authorized to send such a mission critical command. The security provisions for administrative users are discussed in section 6.5. 4.2.4. GET Retrieve a single response from the Attachment Daemon (2.1). The possible sub-commands are: 4.2.4.1. GET CMDDESC Retrieve a text description of a command. Command: GET CMDDESC Response: CMDDESC "" For example: GET CMDDESC su700 load.on and response CMDDESC su700 load.on "Turn on the load immediately" This is like DESC (4.2.4.2), but it applies to an instant command (2.5). 4.2.4.2. GET DESC Retrieve a text description of a variable. Command: GET DESC Response: DESC "" where is a string that gives a brief explanation of the named variable. The Attachment Daemon (2.1) may return "Unavailable" if the file which provides this description is not installed. For example command GET DESC su700 ups.status and response DESC su700 ups.status "UPS status" 4.2.4.3. GET NUMATTACH Retrieve the count kept by the Attachment Daemon (2.1) of all the "_active_" systems protected by this UPS. Command: GET NUMATTACH Response: NUMATTACH Price Expires 30 August 2022 [Page 14] Internet-Draft UPS management protocol February 2022 where is a count of the Primary (2.8) and the number of Secondaries (2.9) currently powered by this UPS. For example command GET ATTACH su700 and response NUMATTACH su700 1 This information is needed by the Management Daemon (2.6) to determine how many Secondaries (2.9) are still connected during the system shutdown process. Note: Historically, this sub-command was known as NUMLOGINS. Since LOGIN was not the conventional user access to a shell or program the name was changed to avoid confusion. 4.2.4.4. GET TYPE Retrieve the type of a UPS variable (2.12). Command: GET TYPE Response: TYPE ... where can be one or more of the following tokens. Multiple types may be returned. For example command GET TYPE su700 input.transfer.low and response TYPE su700 input.transfer.low ENUM +==============+================================================+ | Type | Meaning | +==============+================================================+ | RW | This is a read/write variable. It may be read | | | with command GET VAR (4.2.4.6) and set to a | | | different value with command SET (4.2.11) | +--------------+------------------------------------------------+ | ENUM | An enumerated type, which supports specific | | | predetermined values | +--------------+------------------------------------------------+ | STRING:n | This is a string of maximum length n | +--------------+------------------------------------------------+ | RANGE | This is a number, either integer or float, | | | comprised in the range which may be seen with | | | the command LIST RANGE (4.2.7.4) | +--------------+------------------------------------------------+ | NUMBER | This is a single numeric value, either integer | | | or float | +--------------+------------------------------------------------+ Table 1: Variable Types Price Expires 30 August 2022 [Page 15] Internet-Draft UPS management protocol February 2022 Notes: * ENUM, STRING:n and RANGE are usually associated with RW, but not always. The default , when omitted, is numeric, so either integer or float. Each Driver (2.3) is then responsible for handling values as either integer or float. * Current practice is to represent floating point values using locale C.utf8 which is a decimal (base 10) US English-based representation. Hexadecimal, exponents, and comma for thousands separator are not allowed. For example: "1200.20" is valid, while "1,200.20" and "1200,20" are not valid. 4.2.4.5. GET UPSDESC Retrieve a text description of a UPS. Command: GET UPSDESC Response: UPSDESC "" where is defined by the Attachment Daemon (2.1) configuration. If it is not set, current practice is for the Attachment Daemon (2.1) to return "Unavailable". For example command GET UPSDESC su700 and response UPSDESC su700 "Development box" This can be used to provide human-readable descriptions instead of a cryptic ups@hostname string. 4.2.4.6. GET VAR Retrieve the value of a UPS variable (2.12). Command: GET VAR Response: VAR "" For example command GET VAR su700 ups.status and response VAR su700 ups.status "OB LB" 4.2.5. HELP Return a list of the commands supported by the Attachment Daemon (2.1). This command is intended for human as well as program use. Command HELP Price Expires 30 August 2022 [Page 16] Internet-Draft UPS management protocol February 2022 For example, the following command line sequence executed on an Attachment Daemon (2.1): netcat localhost 3493 HELP Commands: HELP VER GET LIST SET INSTCMD ATTACH DETACH USERNAME PASSWORD STARTTLS Note: Historically, this command also returned LOGIN and LOGOUT. Since LOGIN was not the conventional user access to a shell or program, the command names were changed to ATTACH and DETACH to avoid confusion. 4.2.6. INSTCMD Send an instant command (2.5) to the UPS. Command: INSTCMD where is the name of the UPS and is the instant command (2.5) to be issued to that UPS. If the command succeeds, the response is OK, otherwise see the error responses (4.3.2). For example the command: INSTCMD su700 test.panel.start and the response OK 4.2.7. LIST All the LIST commands produce a response with a common format. The response will begin with BEGIN LIST and then repeat the initial query. A list then follows, with as many lines as are necessary. The response ends with END LIST followed by the initial query. The formatting may seem a bit redundant, but it makes a different form of client possible. A client can send a LIST (4.2.7) query and then wait for the response. When it arrives, the Management Daemon (2.6) doesn't need a complicated state machine to remember which list is which. Note: The current NUT Project (2.7) implementation of the Attachment Daemon (2.1), upsd, sends back the response to a LIST (4.2.7) command as a sequence of messages. The Management Daemon (2.6) should continue reading these messages until it receives the line beginning END LIST. The possible subcommands are: Price Expires 30 August 2022 [Page 17] Internet-Draft UPS management protocol February 2022 4.2.7.1. LIST CLIENT The command calls for the Attachment Daemon (2.1) to report all the current Management Daemon (2.6) clients of a given UPS. Command: LIST CLIENT The response is BEGIN LIST CLIENT CLIENT ... END LIST CLIENT For example, the command LIST CLIENT ups1 and the response: BEGIN LIST CLIENT ups1 CLIENT ups1 ::1 CLIENT ups1 198.51.100.2 END LIST CLIENT ups1 4.2.7.2. LIST CMD The command calls for the Attachment Daemon (2.1) to report a list of the instant commands (2.5) which the Management Daemon (2.6) may send to the Attachment Daemon (2.1). This instant command (2.5) list is the abstracted view of the UPS hardware capabilities. An economical UPS will support few or no instant commands (2.5) but a professional model should support more. Command: LIST CMD The response is: BEGIN LIST CMD CMD ... END LIST CMD where is the name of the UPS, and is the name of the command which may be issued to the UPS. For example the command: LIST CMD su700 and the response: Price Expires 30 August 2022 [Page 18] Internet-Draft UPS management protocol February 2022 BEGIN LIST CMD su700 CMD su700 load.on CMD su700 test.panel.start ... END LIST CMD su700 4.2.7.3. LIST ENUM The command calls for the Attachment Daemon (2.1) to report the set of possible values of a UPS variable (2.12) which has predetermined values. Command: LIST ENUM The response is: BEGIN LIST ENUM ENUM "" ... END LIST ENUM where is the name of the UPS, is the UPS variable (2.12) and is one of the possible values of that UPS variable (2.12). Note that in current practice the output is an unordered list. Note also that the U+0022 QUOTATION MARK characters are part of the response. For example the command: LIST ENUM su700 input.transfer.low and the response: BEGIN LIST ENUM su700 input.transfer.low ENUM su700 input.transfer.low "103" ENUM su700 input.transfer.low "100" ... END LIST ENUM su700 input.transfer.low 4.2.7.4. LIST RANGE The command calls for the Attachment Daemon (2.1) to report the interval in which valid values of UPS variable (2.12) lie. Command: LIST RANGE The response is: Price Expires 30 August 2022 [Page 19] Internet-Draft UPS management protocol February 2022 BEGIN LIST RANGE RANGE "" "" ... END LIST RANGE where is the name of the UPS, is the UPS variable (2.12) and {,} is the interval of valid values of that UPS variable (2.12). Note that the U+0022 QUOTATION MARK characters are part of the response. For example, the command LIST RANGE su700 input.transfer.low and the response: BEGIN LIST RANGE su700 input.transfer.low RANGE su700 input.transfer.low "90" "105" END LIST RANGE su700 input.transfer.low 4.2.7.5. LIST RW The command calls for the Attachment Daemon (2.1) to report a list of the UPS variables (2.12) associated with a given UPS which may be read and written by the Management Daemon (2.6). These variables are the abstracted view of the UPS hardware capabilities. An economical UPS may support few variables but a professional model should support at least the variables which are needed for an automatic shutdown and restart (B). See Section (9.4) for details of the recommended minimum support of variables. A full list of variables is available in source code file docs/nut-names.txt [gitvars] which serves as the Recording Document. Command: LIST RW The response is: BEGIN LIST RW RW "" ... END LIST RW where is the name of the UPS, is the UPS variable (2.12) and is the value of that UPS variable (2.12). Note that the U+0022 QUOTATION MARK characters are part of the response. For example the command: LIST RW su700 and the response: Price Expires 30 August 2022 [Page 20] Internet-Draft UPS management protocol February 2022 BEGIN LIST RW su700 RW su700 output.voltage.nominal "115" RW su700 ups.delay.shutdown "020" ... END LIST RW su700 4.2.7.6. LIST UPS The command calls for the Attachment Daemon (2.1) to report a list of the UPS units to which it is attached. Command: LIST UPS The response is: BEGIN LIST UPS UPS "" ... END LIST UPS where is the name of a UPS, and is the description maintained by the Attachment Daemon (2.1) if available. It is set to "Unavailable" otherwise. Note that the U+0022 QUOTATION MARK characters are part of the response. This command can also be used to determine what values of are valid before calling other functions on the server. This is also a good way to handle situations where a single Attachment Daemon (2.1) supports multiple UPS's. It is also useful for clients which perform a UPS discovery process. For example, the response: BEGIN LIST UPS UPS su700 "Development box" END LIST UPS 4.2.7.7. LIST VAR The command calls for the Attachment Daemon (2.1) to report a list of all the UPS variables (2.12) which it maintains for a given UPS, and the values of those variables. Command: LIST VAR The response is: Price Expires 30 August 2022 [Page 21] Internet-Draft UPS management protocol February 2022 BEGIN LIST VAR VAR "" ... END LIST VAR where is the name of the UPS, is the UPS variable (2.12) and is the value of that variable. Note that the U+0022 QUOTATION MARK characters are part of the response. The response to this command lists the UPS variables (2.12) available for this UPS and their current values. For example the command LIST VAR su700 and the response: BEGIN LIST VAR su700 VAR su700 ups.mfr "Example Mfg" VAR su700 ups.mfr.date "10/17/96" ... END LIST VAR su700 See Section (9.4) for details of the recommended minimum support of variables. A full list of variables is available in source code file docs/nut-names.txt [gitvars] which serves as the Recording Document. 4.2.8. PASSWORD This command is a companion to USERNAME (4.2.13), and is used by a Management Daemon (2.6) to specify the password required to enter a Session (2.10) with the Attachment Daemon (2.1). Command: PASSWORD If the command succeeds, the response is OK, otherwise see the error responses (4.3.2). For examples of the use of commands USERNAME (4.2.13) and PASSWORD by administrative users (2.2) see Section 6.5.2, Paragraph 1. 4.2.9. PRIMARY In current practice, an administrative user (2.2) is recorded by the Attachment Daemon (2.1) in local file upsd.users as being a Primary (2.8). See Management of Administrative Users (6.5.1) for an example. When a Management Daemon (2.6) starts up and opens a Session (2.10) with the Attachment Daemon (2.1), it lays claim to being a Primary (2.8) by sending command PRIMARY to the Attachment Daemon (2.1), thus claiming that it has the required authority to perform such critical actions as setting status symbol FSD. Price Expires 30 August 2022 [Page 22] Internet-Draft UPS management protocol February 2022 Command: PRIMARY where is the name of the UPS. If the Attachment Daemon (2.1) has the authority, the response is OK, otherwise see the error responses (4.3.2). Note: Historically, this command was known as MASTER. 4.2.10. PROTVER Return the implementation version of the command/response protocol used by the Attachment Daemon (2.1). This command is intended for human as well as program use. Command PROTVER For example, the following command line sequence in the Attachment Daemon (2.1): netcat localhost 3493 PROTVER 1.2 Notes: 1. There are no U+0022 QUOTATION MARK characters in the response. 2. Historically, this command was known as NETVER and current practice is to use NETVER instead of PROTVER. 3. The implementation version of the protocol returned by PROTVER is different to the implementation version of the Attachment Daemon (2.1) returned by VER (4.2.14). 4.2.11. SET The command calls for the Attachment Daemon (2.1) to set a UPS variable (2.12) to a given value. Whether this has an effect on the UPS hardware is specific to the Driver (2.3) and the UPS model. Some variables are read-only due to the design of the UPS or its driver. Command: SET VAR "" where is the name of the UPS, is the UPS variable (2.12) and is the value to be assigned to that variable. Note that the U+0022 QUOTATION MARK characters are part of the command. Price Expires 30 August 2022 [Page 23] Internet-Draft UPS management protocol February 2022 If the command succeeds, the response is OK, otherwise see the error responses (4.3.2). For example the command: SET VAR su700 ups.id "My UPS" and the response OK 4.2.12. STARTTLS The client tells the Attachment Daemon (2.1) to switch to TLS encrypted communication. When the client receives OK it also switches to TLS encryption. The parameters and versions of cryptographic libraries are those of the Attachment Daemon's underlying OS and are outside the scope of this document. Command: STARTTLS If the command succeeds, the response is OK STARTTLS, otherwise see the error responses (4.3.2). If the client does not send command STARTTLS to the Attachment Daemon (2.1) communication continues unencrypted, however an Attachment Daemon (2.1) may refuse unencrypted communication. 4.2.13. USERNAME The Attachment Daemon (2.1) limits access to clients whose credentials match those in the file upsd.users. There is no anonymous access. A Management Daemon (2.6) program or script uses command USERNAME and its companion command PASSWORD (4.2.8) to open a Session (2.10) for an administrative user (2.2) with the Attachment Daemon (2.1), Note that this command is for program or script use and is not the familiar login command typed on a command line to gain access to a shell. Command: USERNAME If the command succeeds, the response is OK, otherwise see the error responses (4.3.2). For examples of the use of commands USERNAME and PASSWORD (4.2.8) by administrative users (2.2) see Section 6.5.2, Paragraph 1. 4.2.14. VER Return the implementation version of the Attachment Daemon (2.1). This command is intended for human as well as program use. Command VER Price Expires 30 August 2022 [Page 24] Internet-Draft UPS management protocol February 2022 For example, the following command line sequence: netcat localhost 3493 VER Network UPS Tools upsd 2.7.4 - http://www.networkupstools.org/ Notes: 1. There are no U+0022 QUOTATION MARK characters in the response. 2. The implementation version of the Attachment Daemon (2.1) returned by VER is different to the protocol version returned by PROTVER (4.2.10). 4.3. Summary of Responses 4.3.1. Response when Command Succeeds If the command succeeds, the response has the following command- dependent form: Price Expires 30 August 2022 [Page 25] Internet-Draft UPS management protocol February 2022 +===================+======================+============+ | Command | Response | Note | +===================+======================+============+ | ATTACH (4.2.1) | OK | Was LOGIN | +-------------------+----------------------+------------+ | DETACH (4.2.2) | OK Goodbye | Was LOGOUT | +-------------------+----------------------+------------+ | FSD (4.2.3) | OK FSD-SET | | +-------------------+----------------------+------------+ | GET (4.2.4) | Sub command specific | | +-------------------+----------------------+------------+ | HELP (4.2.5) | List of commands | | +-------------------+----------------------+------------+ | INSTCMD (4.2.6) | OK | | +-------------------+----------------------+------------+ | LIST (4.2.7) | Sub command specific | | +-------------------+----------------------+------------+ | PASSWORD (4.2.8) | OK | | +-------------------+----------------------+------------+ | PRIMARY (4.2.9) | OK | | +-------------------+----------------------+------------+ | PROTVER (4.2.10) | Protocol version | Was NETVER | +-------------------+----------------------+------------+ | SET (4.2.11) | OK | | +-------------------+----------------------+------------+ | STARTTLS (4.2.12) | OK STARTTLS | | +-------------------+----------------------+------------+ | USERNAME (4.2.13) | OK | | +-------------------+----------------------+------------+ | VER (4.2.14) | Program version | | +-------------------+----------------------+------------+ Table 2: Response if command succeeds 4.3.2. Error Responses Error responses have the following format: ERR [] where is a single word token taken from the 27 characters A-Z and U+002D HYPHEN-MINUS. Implementations may if needed add an additional optional . Current practice does not make use of this possibility. The may have one of the following values: Price Expires 30 August 2022 [Page 26] Internet-Draft UPS management protocol February 2022 +==============================+=================================+ | The error name token | Meaning | | | | +==============================+=================================+ | ACCESS-DENIED | The client's host and/or | | | authentication details | | | (username, password) are not | | | sufficient to execute the | | | requested command. | +------------------------------+---------------------------------+ | ALREADY-ATTACHED | The client has already sent a | | | successful ATTACH (4.2.1) | | | command for a given UPS and | | | can't do it again. | | | | | | Note: Historically, this error | | | response was ALREADY-LOGGED-IN. | +------------------------------+---------------------------------+ | ALREADY-SET-PASSWORD | The client has already supplied | | | a PASSWORD and is attempting to | | | repeat the command in the same | | | Session (2.10). | +------------------------------+---------------------------------+ | ALREADY-SET-USERNAME | The client has already supplied | | | a USERNAME, and is attempting | | | to repeat the command within | | | the same Session (2.10). | +------------------------------+---------------------------------+ | CMD-NOT-SUPPORTED | The specified UPS doesn't | | | support the instant command | | | (2.5) command. | +------------------------------+---------------------------------+ | DATA-STALE | The Attachment Daemon (2.1) is | | | connected to the Driver (2.3) | | | for the UPS, but that driver | | | isn't providing regular updates | | | or has specifically marked the | | | data as stale. Current | | | practice is for the Attachment | | | Daemon (2.1) to refuse to | | | provide the Management Daemon | | | (2.6) with variables on stale | | | units to avoid false readings. | | | | | | This generally means that the | | | Driver (2.3) is running, but it | | | has lost communication with the | | | hardware. Check the physical | Price Expires 30 August 2022 [Page 27] Internet-Draft UPS management protocol February 2022 | | connection to the equipment. | +------------------------------+---------------------------------+ | DRIVER-NOT-CONNECTED | The Attachment Daemon (2.1) | | | can't perform the requested | | | command, since the Driver (2.3) | | | for that UPS is not connected. | | | This usually means that the | | | driver is not running, or if it | | | is, is misconfigured. | +------------------------------+---------------------------------+ | FEATURE-NOT-CONFIGURED | This instance of the Attachment | | | Daemon (2.1) hasn't been | | | configured properly to allow | | | the requested feature to | | | operate. In current practice | | | this error response is possible | | | only for command STARTTLS | | | (4.2.12). | +------------------------------+---------------------------------+ | FEATURE-NOT-SUPPORTED | This instance of Attachment | | | Daemon (2.1) does not support | | | the requested feature. In | | | current practice this error | | | response is possible only for | | | command STARTTLS (4.2.12). | +------------------------------+---------------------------------+ | INSTCMD-FAILED | The Attachment Daemon (2.1) | | | failed to deliver the instant | | | command (2.5) request to the | | | Driver (2.3). No further | | | information is available to the | | | client. This typically | | | indicates a dead or broken | | | driver. | +------------------------------+---------------------------------+ | INVALID-ARGUMENT | The client sent an argument to | | | a command which is not | | | recognized or is otherwise not | | | valid in this context. This is | | | typically caused by sending a | | | valid command such as GET | | | (4.2.4) with a subcommand which | | | is not valid. | +------------------------------+---------------------------------+ | INVALID-PASSWORD | The client sent a non valid | | | password. | +------------------------------+---------------------------------+ | INVALID-USERNAME | The client sent an non valid | Price Expires 30 August 2022 [Page 28] Internet-Draft UPS management protocol February 2022 | | username. | +------------------------------+---------------------------------+ | INVALID-VALUE | The value specified in the | | | request is not valid. This | | | usually applies to a SET | | | (4.2.11) of an ENUM (4.2.7.3) | | | type which is using a value not | | | in the list of allowed values. | +------------------------------+---------------------------------+ | PASSWORD-REQUIRED | The command requires a password | | | for authentication, but the | | | client hasn't provided one. | +------------------------------+---------------------------------+ | READONLY | The requested variable in a SET | | | (4.2.11) command is not | | | writable. | +------------------------------+---------------------------------+ | SET-FAILED | The Attachment Daemon (2.1) | | | failed to deliver the set | | | request to the Driver (2.3). | | | This is similar to INSTCMD- | | | FAILED. | +------------------------------+---------------------------------+ | TLS-ALREADY-ENABLED | TLS mode is already enabled on | | | this connection, so the | | | Attachment Daemon (2.1) can't | | | start it again. | | | | | | Note: Historically, this | | | message was ALREADY-SSL-MODE. | +------------------------------+---------------------------------+ | TLS-NOT-ENABLED | TLS mode is required but has | | | not yet been enabled on this | | | connection, so the Attachment | | | Daemon (2.1) can't send | | | commands. | | | | | | Note: This message is | | | experimental and not in current | | | common use. | +------------------------------+---------------------------------+ | TOO-LONG | The requested value in a SET | | | (4.2.11) command is too long. | +------------------------------+---------------------------------+ | UNKNOWN-COMMAND | The Attachment Daemon (2.1) | | | doesn't recognize the command. | +------------------------------+---------------------------------+ | UNKNOWN-UPS | The UPS specified in the | Price Expires 30 August 2022 [Page 29] Internet-Draft UPS management protocol February 2022 | | request is not known to the | | | Attachment Daemon (2.1). This | | | usually means that it didn't | | | match anything in the | | | Attachment Daemon (2.1) | | | configuration. | +------------------------------+---------------------------------+ | USERNAME-REQUIRED | The command requires a username | | | for authentication, but the | | | client hasn't provided one. | +------------------------------+---------------------------------+ | VAR-NOT-SUPPORTED | The specified UPS doesn't | | | support the UPS variable (2.12) | | | in the command. | +------------------------------+---------------------------------+ Table 3: Error responses 5. Statuses and Events 5.1. Status Symbols These symbols resume the abstracted view of the UPS hardware maintained by the Attachment Daemon (2.1). The variable ups.status contains one or more space-separated status symbols which together describe the UPS state at that instant. In current practice the Management Daemon (2.6) will poll variable ups.status every 5 seconds with a command such as GET VAR su700 ups.status and response VAR su700 ups.status "OB LB" to discover changes in the UPS status. These changes will indicate UPS events. +=========+======================================================+ | Status | Meaning | | Symbol | | +=========+======================================================+ | ALARM | The UPS reports that it requires intervention. | +---------+------------------------------------------------------+ | BOOST | The UPS has determined that the voltage level of the | | | public power supply is too low, and is boosting it | | | to the required level. The UPS continues to supply | | | the protected system from the public power supply. | +---------+------------------------------------------------------+ | BYPASS | The UPS is feeding current directly from the public | | | power supply to the protected system. The backup | | | facilities are disconnected. This state allows | | | maintenance personnel to change the batteries | | | without interrupting the protected system. | +---------+------------------------------------------------------+ Price Expires 30 August 2022 [Page 30] Internet-Draft UPS management protocol February 2022 | CAL | The UPS is calibrating itself, for example to | | | determine at what charge the LB status is raised or | | | lowered. | +---------+------------------------------------------------------+ | CHRG | The UPS battery is charging. This usually implies | | | that the UPS also has status OL, but may not be the | | | case if the UPS also has status OFF. | +---------+------------------------------------------------------+ | COMM | The Attachment Daemon (2.1) has effective contact | | | with the UPS. | +---------+------------------------------------------------------+ | DISCHRG | The UPS battery is discharging. This usually | | | implies that the UPS also has status OB, but may not | | | be the case if the UPS also has status OFF. | +---------+------------------------------------------------------+ | FSD | This "Forced Shutdown" status signals that the final | | | shutdown sequence has begun. | +---------+------------------------------------------------------+ | LB | Low Battery. The battery level of the UPS is below | | | a chosen limit. The UPS may be in status OL or OB. | +---------+------------------------------------------------------+ | NOCOMM | The Attachment Daemon (2.1) has no effective contact | | | with the UPS. | +---------+------------------------------------------------------+ | OB | On Battery. The UPS is taking energy from it's | | | battery. The battery is discharging. A UPS must | | | have status OB or OL, otherwise it is deemed dead. | +---------+------------------------------------------------------+ | OFF | The UPS is in state "Off". It does not react to | | | failure in the public power supply. The exact | | | meaning depends on the model. | +---------+------------------------------------------------------+ | OL | Online. The UPS is online, receiving energy from | | | the public power supply. The battery is charging. | | | A UPS must have status OB or OL, otherwise it is | | | deemed dead. | +---------+------------------------------------------------------+ | OVER | Overloaded. The UPS reports that the load on it is | | | beyond it's normal operating maximum. | +---------+------------------------------------------------------+ | RB | Replace battery. The UPS reports that it's battery/ | | | batteries should be replaced. | +---------+------------------------------------------------------+ | TEST | Under test. The UPS is currently undergoing a test, | | | which may have been called for manually or | | | internally. | +---------+------------------------------------------------------+ | TICK | Heartbeat. A software UPS in the Attachment Daemon | Price Expires 30 August 2022 [Page 31] Internet-Draft UPS management protocol February 2022 | | (2.1) provides a regular signal monitored by the | | | Management Daemon (2.6) as a way of verifying | | | effective end-to-end management. TICK and TOCK are | | | companions, they are considered experimental. | +---------+------------------------------------------------------+ | TOCK | Heartbeat. See TICK | +---------+------------------------------------------------------+ | TRIM | The UPS has determined that the voltage level of the | | | public power supply is too high, and is reducing it | | | to the required level. The UPS continues to supply | | | the protected system from the public power supply. | +---------+------------------------------------------------------+ Table 4: UPS Status Symbols 5.2. Events A Management Daemon (2.6) detects the occurrence of a UPS Event from a change in the UPS status (2.11) received from the Attachment Daemon (2.1). The following table summarizes the process. A status of "none" means that the status symbol is not present in the variable ups.status. The Management Daemon (2.6) should retrieve the variable ups.status from the Attachment Daemon (2.1) at regular intervals. If the interval is too short, compute and network resources will be wasted, but if the interval is too large, the Management Daemon (2.6) risks missing short-lived changes in the UPS status. A default value of 5 seconds is recommended, but an implementation may make this value configurable. By default the "old" status is therefore the previous value retrieved 5 seconds ago. Current practice is for the Management Daemon (2.6) to assign names to certain events. These is shown in the table in parentheses. +=======+=========+===============++=========+========+=============+ |Old | New |Event || Old | New |Event | |status | status | || status | status | | +=======+=========+===============++=========+========+=============+ |none | ALARM |Alarm on || ALARM | none |Alarm off | +-------+---------+---------------++---------+--------+-------------+ |none | BOOST |Boosting || BOOST | none |Not boosting | | | |voltage || | | | +-------+---------+---------------++---------+--------+-------------+ |none | BYPASS |Bypass on || BYPASS | none |Bypass off | +-------+---------+---------------++---------+--------+-------------+ |none | CAL |Calibrating || CAL | none |Not | Price Expires 30 August 2022 [Page 32] Internet-Draft UPS management protocol February 2022 | | | || | |calibrating | +-------+---------+---------------++---------+--------+-------------+ |none | CHRG |Charging || CHRG | none |Not charging | +-------+---------+---------------++---------+--------+-------------+ |none | COMM |UPS || COMM | none |See note 4 | | | |communicating || | | | | | |(COMMOK) || | | | +-------+---------+---------------++---------+--------+-------------+ |none | DISCHRG |Discharging || DISCHRG | none |Not | | | | || | |discharging | +-------+---------+---------------++---------+--------+-------------+ |none | FSD |System shutdown|| FSD | none |Shutdown | | | |(FSD) || | |abandoned. | | | |(SHUTDOWN) || | |See note 1 | +-------+---------+---------------++---------+--------+-------------+ |none | LB |Low battery. || LB | none |Battery not | | | |See note 2 || | |low | | | |(LOWBATT) || | | | +-------+---------+---------------++---------+--------+-------------+ |none | NOCOMM |UPS dead? See || NOCOMM | none |See note 4 | | | |note 4 || | | | | | |(COMMBAD) || | | | | | |(NOCOMM) || | | | +-------+---------+---------------++---------+--------+-------------+ |none | OFF |UPS turned off || OFF | none |UPS not | | | | || | |turned off | +-------+---------+---------------++---------+--------+-------------+ |OB | OL |Receiving power|| OL | OB |Power lost | | | |(ONLINE) || | |(ONBATT) | +-------+---------+---------------++---------+--------+-------------+ |none | OVER |UPS overloaded || OVER | none |Overload gone| +-------+---------+---------------++---------+--------+-------------+ |none | RB |Replace battery|| RB | none |Replacement | | | |(REPLBATT) || | |canceled | +-------+---------+---------------++---------+--------+-------------+ |none | TEST |Test starts || TEST | none |Test finished| +-------+---------+---------------++---------+--------+-------------+ |none | TICK |Heartbeat || TICK | none |No heartbeat.| | | |event. See || | |See note 3 | | | |note 3 || | | | +-------+---------+---------------++---------+--------+-------------+ |none | TOCK |Heartbeat || TOCK | none |No heartbeat.| | | |event. See || | |See note 3 | | | |note 3 || | | | +-------+---------+---------------++---------+--------+-------------+ |none | TRIM |Trimming || TRIM | none |Not trimming | | | |voltage || | | | +-------+---------+---------------++---------+--------+-------------+ Price Expires 30 August 2022 [Page 33] Internet-Draft UPS management protocol February 2022 Table 5: Event deduction from status changes Notes 1. Current practice does not include this event. 2. If the status OB is present, current practice takes Management Daemon (2.6) reception of LB as an order to perform an emergency system shutdown. 3. The use of a software defined UPS to provide a heartbeat is experimental and is not part of common current practice. 4. Current practice is: if the UPS has not responded for 15 seconds, the Management Daemon (2.6) assumes that the UPS is "_dead_" (NOCOMM), and if the last known OL/OB status was OB a system shutdown (FSD) is called for. 6. Security Considerations The security issues raised by UPS management are those of the power industry in general: they are addressed in detail in Technical Specification IEC 62351-1 [IEC62351-1]. In addition to equipment security, cyber security is now an essential consideration. Quoting from IEC 62351-1 clause 5.2.3.5 [IEC62351-1]: | With the computer systems for power operations presumably kept | isolated from the Internet, many utility personnel do not see any | reason for adding security measures to these systems. However, as | clearly seen from these Subclauses, this may not be true anymore | as networking becomes more prevalent and additional information | access requirements grow. Clause 5.3.5 [IEC62351-1] lists the typical security attacks: | Eavesdropping, Masquerade, Man-in-the-Middle, Replay, Resource | Exhaustion Additionally the UPS management protocol provides means for a Management Daemon (2.6) to shut down a working system and it's power supply as described in The Shutdown Story (B). A malicious client acting as a Management Daemon (2.6) could turn off the UPS power outlets causing the system to fail. Most of these issues are well known IT issues concerning system protection and disaster recovery, and are beyond the scope of this document, however the protocol itself has security considerations: Price Expires 30 August 2022 [Page 34] Internet-Draft UPS management protocol February 2022 1. It should not be possible for non-authorized agents to open sessions and send mission-critical commands such as FSD (4.2.3) to the Attachment Daemon (2.1). 2. It should not be possible to intercept the traffic between the Attachment Daemon (2.1) and the Management Daemon (2.6). Let's look more closely at these requirements. 6.1. Agent Verification The protocol provides commands USERNAME (4.2.13) and PASSWORD (4.2.8) which allow an administrative user (2.2) in a Management Daemon (2.6) to authenticate itself to the Attachment Daemon (2.1). The administrative user (2.2) name and password need protection from sniffing and local malicious users. This is done by encrypting the traffic and properly restricting access to the configuration files. 6.2. Current Encryption Practice The protocol provides command STARTTLS (4.2.12) which calls on the Attachment Daemon (2.1) to support TLS encryption of the communication. If this command is accepted, the Management Daemon (2.6) also encrypts. At present the command STARTTLS (4.2.12) is too frequently refused, and traffic proceeds unencrypted, with plain text transmission of passwords and status values. In current NUT Project (2.7) practice, the use of TLS is optional, however a Management Daemon (2.6) may refuse to accept unencrypted communication. This is done by setting declarations FORCESSL to 1 and CERTVERIFY to 1 in the Management Daemon (2.6) configuration file. A further weakness is that the FORCESSL and CERTVERIFY declarations are in the Management Daemon (2.6) configuration file and not in the Attachment Daemon (2.1). Secure practice requires enforcement by the Attachment Daemon (2.1) rather than a possibly rogue Management Daemon (2.6) out on the Internet. 6.2.1. Secure Tunnels Some system administrators currently use techniques such as stunnel [stunnel] to encrypt the commands and responses, but the NUT Project (2.7) has no procedure to enforce this on sites. Price Expires 30 August 2022 [Page 35] Internet-Draft UPS management protocol February 2022 6.3. Current General Security Practice Experience over the last 20 years shows that new UPS management software releases are not frequent, and when installed, stay unmodified for some years. This is probably because UPS management is a mature hardware dependent activity. A limited number of system administrators have access to the UPS hardware and software and tend to assume a certain "security by obscurity" since many installations have a configuration as shown in figure 5 which uses port nut/3493 between the two daemons running in the same system. The traffic is often not encrypted, and when encrypted uses deprecated early versions of SSL/TLS. ,-----, ,--------------------,---------------------, | UPS |---| Attachment <-Commands Management | | |===| Daemon Responses-> Daemon | /-----\ '--------------------'---------------------' Listens on port nut/3493 for localhost Figure 5: Common single-system configuration This situation is now changing as low cost processors become available, costing significantly less than a UPS unit. This evolution makes it interesting to shift to a configuration as shown in figure 6, but it also exacerbates the security weakness of figure 5 since the traffic between the daemons is now over an exposed network. ,-----,------------, ,--------------, | UPS - Attachment | <-Commands | Management | | | Daemon | Responses-> | Daemon | /-----'------------\ '--------------' Listens on port nut/3493 Figure 6: Integration of UPS and Attachment Daemon 6.4. Security Needs UPS management needs to move to a more secure practice in which all traffic is encrypted, but this cannot be imposed by a wave of the hand: it cannot be implemented quickly and without impact to many deployed systems. The ideal would be an easy-to-follow migration plan which provides the required encryption but tolerates the slow moving updates of the UPS software. Price Expires 30 August 2022 [Page 36] Internet-Draft UPS management protocol February 2022 Here are four examples of possible temporary solutions. 6.4.1. Shims A possible technique introduces shims between the Attachment Daemon (2.1) and the network, and between the network and the Management Daemon (2.6) as shown in figure 7. These shims provide TLS support [RFC8446], allowing the Attachment Daemon (2.1) and Management Daemon (2.6) to continue temporarily without native TLS. The technique has been successfully tested, but the principal difficulty is that the shims make use of a second port which is not currently available. TLS shim listens TLS shim listens on port TBD1 on port 3493 ,-----,------------,----, ,----,--------------, | UPS - Attachment |TLS | <-STARTTLS | TLS| Management | | | Daemon |shim| OK--> |shim| Daemon | /-----'------------'----\ '----'--------------' Listens on port nut/3493 Figure 7: Shims provide TLS support during migration 6.4.1.1. Attachment Daemon Shim The shim in front of the Attachment Daemon (2.1) listens to incoming traffic on a port to be specified. When it receives the command STARTTLS (4.2.12) it 1. Returns OK to the client and sets up TLS encapsulation. 2. Does not send STARTTLS (4.2.12) to the Attachment Daemon (2.1) port nut/3493. All other commands and responses are passed through. 6.4.1.2. Management Daemon Shim The shim in front of the Management Daemon (2.6) listens for incoming traffic on port nut/3493. When it receives the command STARTTLS (4.2.12) it 1. Returns FEATURE-NOT-CONFIGURED to the client. 2. Sends STARTTLS (4.2.12) to the Attachment Daemon (2.1) on a port to be specified. All other commands and responses are passed through. Price Expires 30 August 2022 [Page 37] Internet-Draft UPS management protocol February 2022 6.4.2. TLS Tunnels Another possible technique is the use of TLS tunnels [RFC8446], using a software such as stunnel [stunnel] which adds OpenSSL-based TLS support without modifying the Attachment Daemon (2.1) or Management Daemon (2.6). 6.4.3. VPN A further option to secure communications is very similar to TLS tunnelling [RFC8446] and consists of routing the NUT traffic through a Virtual Private Network, VPN. 6.4.4. VLAN A fourth option is to isolate the UPS management traffic at the network switching level using a Virtual LAN, VLAN technique. ,-------------, ,-------------, ,-----, | Attachment | | Management | | UPS |---| Daemon | | Daemon | | | |-------------| UPS |-------------| | |===| | Management | UPS | /-----\ | Protected |---------------| Management | | Server | VLAN | Client | | | '-------------' '-------------' Production | VLAN ,---|-------, ,-----------,| ,-----------,|' | Clients |' '-----------' Figure 8: UPS Management Protocol runs over its own VLAN In figure (8) there are two VLANS: The main traffic between the protected server and its clients uses the production VLAN. The UPS management traffic between the attachment and management daemons uses the UPS management VLAN. 6.4.5. Long Term: Enforced Secure Communication In the long term, enforcing secure communication requires tightening up the Attachment Daemon (2.1) to require the use of command STARTTLS (4.2.12) for commands sent over the global Internet. In such a situation an Attachment Daemon (2.1) listening for traffic other than from the localhost: Price Expires 30 August 2022 [Page 38] Internet-Draft UPS management protocol February 2022 1. SHOULD require and accept command STARTTLS (4.2.12), 2. MUST encrypt all communication with a Management Daemon (2.6), 3. SHALL refuse all non-encrypted commands except an initial STARTTLS (4.2.12). Notes: * The SHOULD rather than MUST in 1 above allows system administrators to enforce secure communication using other techniques which do not involve the STARTTLS (4.2.12) command. * If an Attachment Daemon (2.1) requires that all commands be encrypted as required by the MUST in 2 above, then automatically each Management Daemon (2.6) MUST encrypt as well, since it has to do so in order to gain access. * The SHALL in 3 above applies to traffic from the global Internet. An Attachment Daemon (2.1) MAY accept unencrypted commands from localhost if the local installation's security practices allow it, for example in a dedicated appliance. * Note that the separate management of strongly secure traffic from the global Internet and weakly secure traffic from localhost can be achieved by using two ports: nut/3493 for the current weakly secure traffic from localhost, and some other port, perhaps ups/ TBD1, for enforced secure communication, much in the manner of http and https. 6.4.6. Firewalls Firewalls SHOULD be used to restrict the communication between the Attachment Daemon (2.1) and the accepted Management Daemons (2.6), prohibiting and discarding traffic from any systems that are not part of the envisioned setup. Note: See note (Section 6.4.5, Paragraph 4, Item 1) above on the use of SHOULD. 6.5. Administrative Security Administrative commands such as FSD (4.2.3), INSTCMD (4.2.6) and SET (4.2.11) are powerful and can have a deep effect on system integrity, For example, the command FSD (4.2.3) is involved in mission critical system shutdown decisions. Access to them needs to be managed and restricted. This clause presents the current practice. Price Expires 30 August 2022 [Page 39] Internet-Draft UPS management protocol February 2022 6.5.1. Management of Administrative Users The Attachment Daemon (2.1) maintains a file (currently upsd.users) defining each administrative user (2.2). Note that these users are independent of those recorded in file /etc/passwd. Each administrative user gets its own section in file upsd.users. The declarations in that section set the parameters which define that user's privileges. The section begins with the name of the user enclosed in square brackets, U+005B LEFT SQUARE BRACKET [ and U+005D RIGHT SQUARE BRACKET ], and continues until the next user name in brackets or EOF. For example the following file declares two administrative users (2.2) admin and pfy: [admin] password = sekret upsmon master actions = SET instcmds = ALL [pfy] password = sekret instcmds = test.panel.start instcmds = test.panel.stop Within each section the administrative user (2.2) declarations are: Price Expires 30 August 2022 [Page 40] Internet-Draft UPS management protocol February 2022 +=============+==========================================+ | Declaration | Meaning | +=============+==========================================+ | actions | Allow the user to do certain things in | | | the Attachment Daemon (2.1). To specify | | | multiple actions, use multiple instances | | | of the declaration. Valid actions are: | | | | | | * FSD Set the "Forced Shutdown" flag | | | for this UPS. See FSD (4.2.3). | | | | | | * SET Change the value of a UPS | | | variable (2.12). See SET (4.2.11). | +-------------+------------------------------------------+ | instcmds | Let a user initiate specific instant | | | commands. See section INSTCMD (4.2.6). | | | Use value ALL to grant all commands | | | automatically. To specify multiple | | | commands, use multiple instances of the | | | instcmds field. For the full list of | | | what a given UPS supports, use client | | | upscmd -l supplied by the NUT Project | | | (2.7). | +-------------+------------------------------------------+ | password | Set the password for this user. _Your | | | password should be more secure than the | | | examples shown._ | +-------------+------------------------------------------+ | upsmon | Add the necessary actions for a | | | Management Daemon (2.6) to process a | | | system shutdown. In current practice | | | the value is still master or slave. | | | Note that there is no U+003D EQUALS SIGN | | | =. | +-------------+------------------------------------------+ Table 6: Administrative user declarations 6.5.2. An Administrative User of a Client Management Daemon The following examples show the current security practices for administrative users (2.2) of a client Management Daemon (2.6) They also illustrate the command pair USERNAME (4.2.13) and PASSWORD (4.2.8). Price Expires 30 August 2022 [Page 41] Internet-Draft UPS management protocol February 2022 6.5.2.1. An Administrative User Logs into a Short Session In this simple example of current practice, the system administrator sets the battery level at which an Attachment Daemon (2.1) will raise the status LB, represented by variable battery.charge.low, to 35% of full charge. A system administrator types the following command to call the client upsrw supplied by the NUT Project (2.7). upsrw -s battery.charge.low=35 -u admin -p sekret UPS-1@example.com The USERNAME (4.2.13) and PASSWORD (4.2.8) commands are issued within the client upsrw and the Session (2.10) is of short duration. 6.5.2.2. An Administrative User Logs into a Long Session In this second example of current practice, the long-running Management Daemon (2.6) upsmon which is responsible for initiating system shutdowns and which is provided by the NUT Project (2.7) issues commands USERNAME (4.2.13) and PASSWORD (4.2.8) when it starts up. The data needed for the USERNAME (4.2.13) and PASSWORD (4.2.8) is provided by a configuration file upsmon.conf which contains the line MONITOR UPS-1@example.com 1 admin secret master This says that the UPS to be monitored is UPS-1@example.com, it provides 1 single power supply, the administrative user (2.2) is admin with password secret. The Management Daemon (2.6) acts as a Primary (2.8), although current practice uses the term master. The USERNAME (4.2.13) and PASSWORD (4.2.8) commands are contained within the client upsmon and the Session (2.10) is of long duration. 7. Codepoint Management This document raises five matters of codepoint management: 1. The namespaces occupied by the protocol commands (4.2) described in this document. 2. The namespaces occupied by the protocol responses (4.3.2) described in this document. 3. The namespace occupied by UPS status (2.11) names, 4. The namespace occupied by UPS variable (2.12) names, Price Expires 30 August 2022 [Page 42] Internet-Draft UPS management protocol February 2022 5. The port name and port number used to manage UPS units. 7.1. Namespaces used by Command, Responses, Statuses and Variables Current NUT Project (2.7) experience after more than 20 years is that the UPS management area advances slowly, and that there are few requests to modify or extend the Commands, Responses, Statuses and Variables. When this does occur, the NUT Project (2.7) has been able to settle the matter without difficulty in the project mailing list. It is therefore proposed to not burden IANA with this namespace management and to continue with the current process in which the project in its mailing list acts as a Working Group. The Commands, Responses, Statuses and Variables are currently recorded as follows: +========================+====================+===================+ | Namespace | Recording document | Reference | +========================+====================+===================+ | Commands and Responses | This document | Commands (4.2), | | | | Responses (4.3) | +------------------------+--------------------+-------------------+ | (Idem, historical | Project Developer | Developer Guide | | record) | Guide Ch 9 | [devguide] | +------------------------+--------------------+-------------------+ | Statuses | This document | Statuses (5.1) | +------------------------+--------------------+-------------------+ | (Idem, historical | Source code | GitHub repository | | record) | clients/status.h | [gitstats] | +------------------------+--------------------+-------------------+ | Variables | Source code file | GitHub repository | | | docs/nut-names.txt | [gitvars] | +------------------------+--------------------+-------------------+ Table 7: Project records of namespace allocation 7.2. Port Name and Number used to Manage UPS Units See the IANA Registry [Registry] for the latest situation. 7.2.1. Port nut/3493 In 2002 IANA assigned port nut/3493 to project lead Russell Kroll, and updated the assignment to the NUT Project (2.7) itself in 2020. Price Expires 30 August 2022 [Page 43] Internet-Draft UPS management protocol February 2022 7.2.2. Port ups/401 In 2008 IANA assigned ups/401 "Uninterruptible Power Supply" to Mr. Charles Bennett as both assignee and contact. We have been unable to find any protocol document or other published activity report for this port other than the One Windows Trojan. Mr. Bennett himself died in 2015, see obituary [Bennett]. Since his email address was registered by IANA as bennettc@ohio.edu it is possible that the University of Ohio is a successor in interest. The editor tried to contact the IT support department of the university by email and telephone but was rejected. // Ed: My non-contact was Mr. Keith Brock, IT Support Senior // Specialist, brock@ohio.edu +1 740 597 2136 7.2.3. NUT Project Requirement The NUT Project (2.7) needs to address the current weak security (6.3) of UPS management deployments, for example * by implementing the "shim" technique (Figure 7) in section (6.4) for providing secure access to the Attachment Daemon (2.1), * or by providing a choice of ports through which an Attachment Daemon (2.1) may receive commands: one for "legacy" traffic, the other for fully secured traffic. The project needs a second registered port. Since ports are a limited resource, it would be better to re-use an existing port rather than request a new one, and the project is interested in using existing port ups/TBD1. Let's look more closely at this: * The port name "ups" satisfies the Principle of Least Surprise. It is not surprising for a port called "ups" to be used to manage UPSs. It is unlikely to be used for anything else. * There are no other known users of this port and no other published protocols or usage reports. * The currently assigned port number 401 is for a system port. The project has no imperative need for such a port; a user port, TBD1, would be sufficient. The Attachment Daemon (2.1) is a system activity, but it can be launched by root and dropped to a non- privileged user perfectly well on a user port. Note: In Unix-like systems a port with a number below 1024 is privileged and requires elevated permissions to manage. * System ports are more likely to attract malicious scans than user ports. * The project does not need to be assigned this port. The need is to be able to use port "ups". Price Expires 30 August 2022 [Page 44] Internet-Draft UPS management protocol February 2022 8. IANA Considerations 8.1. Port Name ups: Reference to this Document The NUT Project (2.7) has a requirement to use a second port (7.2.3), and would like to use port name ups as well as port nut. The project requests that IANA authorise such use, perhaps by updating the Service Name and Transport Protocol Port Number Registry [Registry] for ports ups and nut/3493 to include a reference to this document. UPS management does not need a system port (7.2.3). If port number 401 were freed and the name ups assigned to user port TBD1, that would be equally effective. // The document shepherd is requested to replace the port number TBD1 // by any number that IANA assigns to port name ups. 8.2. Change of Registrant The NUT Project (2.7) advises IANA that port ups/401 has no effective registrant (7.2.2). The project does not have an imperative need to be the registrant but will accept to become the registrant if IANA deems such change desirable. Such a change in registrant could be accompanied by an allocation of a user port number TBD1. 9. Implementation Status This section presents a very short report on the status of the Network UPS tools project * May 1996: The first hack as a cron job. * September 1997: The first server-client code. * March 1998: First public release. * June 1999: Code rewrite with a UPS driver smartups, an Attachment Daemon (2.1) upsd and a simple Management Daemon (2.6). * September 1999: The project became "Network UPS Tools". The Management Daemon (2.6) upsmon supported primary/secondary configurations. * June 2001: Common core for multiple drivers. Arnaud Quette took over the project lead from Russell Kroll. * May 2002: IANA granted port nut/3493. August: release 1.0.0. November: OpenSSL support. * April 2003: The initial set of command and variable names was designed. * March 2016: Version 2.7.4 released, supported over 100 device manufacturers and hundreds of UPS models. Price Expires 30 August 2022 [Page 45] Internet-Draft UPS management protocol February 2022 * November 2020: Evgeny "Jim" Klimov took over project lead from Arnaud Quette. For a much more detailed history of the NUT Project (2.7) see the User Manual, Appendix J [History] 9.1. An Implementation of the Attachment Daemon The NUT Project (2.7) implemented an Attachment Daemon (2.1) as program upsd and a set of hardware specific drivers, all written in K&R C. upsd supported all of the protocol commands and responses defined by this document. An experimental program written in Python3 provided a TLS 1.3 [RFC8446] shim daemon as shown in figure (7) which ran in front of upsd, making it appear that upsd supported TLS 1.3. 9.2. Implementations of the Management Daemon There are several examples of a Management Daemon (2.6): the NUT Project (2.7) provided upsmon which takes the system shutdown decision when the public power supply fails. Further configuration options such as timers were provided by helper program upssched. Other programs representing the Management Daemon (2.6): * upsc reported the values of the variables (8) defined for a given UPS. * upsrw reported on and changed the values of the readable and writable configuration variables (A.2) defined for a given UPS. * upscmd reported on and executed the instant action commands (4.2.6) defined for a given UPS. * UPSmon.py was an experimental Python3 rewrite of upsmon and upssched which included support for TLS 1.3 [RFC8446]. 9.3. Inclusion in Software Distributions The programs upsd, upsmon, upssched, upsc, upscmd and upsrw have been included in the package known as "nut" in the package systems of many distributions: all the major Linux distributions, and Unix distributions such as OpenBSD and OpenSolaris. A Microsoft Windows version has been developed but was not maintained. Price Expires 30 August 2022 [Page 46] Internet-Draft UPS management protocol February 2022 9.4. Recommended Minimum Support The features provided by current UPS units vary widely. However experience shows that a minimum feature set is needed for satisfactory use of the NUT Project software. A full list of variables is available in source code file docs/nut-names.txt [gitvars] which serves as the Recording Document. 9.4.1. Desktop PC Variables The following variables form a minimum set suitable for Desktop PC. It is expected that on public power supply failure, the PC will be halted. It will not restart automatically when power returns. * battery.charge * battery.charge.low * device.mfr * device.model * ups.status with the minimum status symbol (5.1) set OL OB LB FSD 9.4.2. Unattended Servers, Additional Variables The following additional variables are needed in a minimum set suitable for an unattended server. It is expected that on public power supply failure, the server will be halted. It will restart automatically when power returns. * battery.date * device.serial * ups.delay.shutdown * ups.delay.start 9.4.3. Commands Satisfactory use of the NUT Project software requires support for all commands. Price Expires 30 August 2022 [Page 47] Internet-Draft UPS management protocol February 2022 10. Acknowledgments This document is based on the NUT Project (2.7) documentation [devguide]. The editor acknowledges the work of Charles Lepple, Arjen de Korte, Arnaud Quette, Jim Klimov, Russell Kroll, Manuel Wolfshant, Mark Hansen and many others who contribute to the nut-upsuser [nut-upsuser]. and nut-upsdev [nut-upsdev] mailing lists. The source for this document is marked up using an SGML DTD [SGML] and an XML meta-DTD as defined by HyTime Annex A [HyTimeA]. The sgmlnorm [sgmlnorm] program generates XML which program xml2rfc [RFC7991] uses to prepare the HTML and text renderings. The editor acknowledges the help received from Carsten Bormann and Julian Reschke in the xml2rfc mailing list. The editor thanks Adrian Farrel for advice received during the preparation of this document. Many helpful comments were received from Bart Smit, David Zomaya, Joyce Norris and Ted Mittelstaedt. 11. 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, . 12. Informative References [Bennett] "Charles Bennett Obituary", Publisher: Jagers and Sons Funeral Home, 24 Morris Ave., Athens OH, . [devguide] "Network UPS Tools (NUT) Project Developer Guide", . [Documentation] "Network UPS Tools Documentation", . [gitstats] "GitHub Network UPS Tools code repository, status names", . Price Expires 30 August 2022 [Page 48] Internet-Draft UPS management protocol February 2022 [gitvars] "GitHub Network UPS Tools code repository, variable names", . [History] "Network UPS Tools User Manual, Appendix J Project history", . [HyTimeA] "International Standard ISO/IEC 10744 -- Hypermedia/Time- based Structuring Language, Annex A, SGML Extended Facilities", ISO/IEC JTC 1/SC 34 Document description and processing languages, 1997. [IEC62351-1] "IEC TS 62351-1 Power systems management and associated information exchange -- Data and communications security. Part 1: Communication network and system security -- Introduction to security issues", IEC Technical Specification Reference number IEC/TS 62351-1:2007(E), 35 pages, CHF 205, Technical Committee TC 57 - Power systems management and associated information exchange, 15 May 2007, . [Library] "GitHub Network UPS Tools, Devices Dumps Library", . [NUT] "Network UPS Tools (NUT) Project", . [nut-repository] "GitHub Repository for the Network UPS Tools (NUT) Project", . [nut-upsdev] "Network UPS Tools (NUT) Project Mailing List for developers", . [nut-upsuser] "Network UPS Tools (NUT) Project Mailing List for users", . Price Expires 30 August 2022 [Page 49] Internet-Draft UPS management protocol February 2022 [Registry] "Service Name and Transport Protocol Port Number Registry", Publisher: IANA, . [RFC7942] Sheffer, Y. and A. Farrel, "Improving Awareness of Running Code: The Implementation Status Section", BCP 205, RFC 7942, DOI 10.17487/RFC7942, July 2016, . [RFC7991] Hoffman, P., "The "xml2rfc" Version 3 Vocabulary", RFC 7991, December 2016, . [RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018, . [SGML] Goldfarb, Charles F., "The SGML Handbook", ISBN 0-19-853737-9, 1990. [sgmlnorm] Clark, James., "SGMLNORM An SGML System Conforming to International Standard ISO 8879 -- Standard Generalized Markup Language", . [stunnel] Trojnara, Michal., "Stunnel proxy adds TLS encryption functionality to existing clients and servers", . Appendix A. Variables The UPS variables (2.12) represent the abstracted state of the UPS unit. Certain variables represent not only the state of some hardware feature, but also provide tunable values and instant commands (2.5). The full set of variables is recorded in the reference document for variable names [gitvars]. The number of variables used in a given deployment depends on the sophistication of the UPS product: this annex shows a typical example of the subset of variables used for a reasonably complete "consumer grade" UPS. The NUT Project (2.7) maintains a large library of the variable subsets [Library] used by different UPS models. Note that successive versions of a given product may add or delete features causing a change in the subset of variables used. An example is the removal of ups.delay.start from a "consumer grade" UPS. The manufacturer reserves the feature for the "professional" product. Price Expires 30 August 2022 [Page 50] Internet-Draft UPS management protocol February 2022 An implementation of a Management Daemon (2.6) acting as a utility program may provide a listing of the variables available for a given product, for example utility program upsc as included in the NUT package (9.2). The following sections illustrate the use of variables by taking the values associated with a typical product example of a 1600Va 1000W UPS. A.1. Typical UPS Variables +===============================+============+====================+ | Variable | Typical | Default | | | value | description | +===============================+============+====================+ | battery.charge | 100 | "Battery charge | | | | (percent of full)" | +-------------------------------+------------+--------------------+ | battery.charge.low | 20 | "Remaining battery | | | | level when UPS | | | | switches to LB | | | | (percent)" | +-------------------------------+------------+--------------------+ | battery.runtime | 1481 | "Battery runtime | | | | (seconds)" | +-------------------------------+------------+--------------------+ | battery.type | PbAc | "Battery | | | | chemistry" | +-------------------------------+------------+--------------------+ | device.mfr | Example | "" | | | Mfg | | +-------------------------------+------------+--------------------+ | device.model | Economy | "" | | | 1600 | | +-------------------------------+------------+--------------------+ | device.serial | 1234567890 | "" | +-------------------------------+------------+--------------------+ | device.type | ups | "" | +-------------------------------+------------+--------------------+ | driver.name | usbhid-ups | "Driver name" | +-------------------------------+------------+--------------------+ | driver.parameter.lowbatt | 37 | "Driver parameter: | | | | " | +-------------------------------+------------+--------------------+ | driver.parameter.offdelay | 30 | "Driver parameter: | | | | " | +-------------------------------+------------+--------------------+ | driver.parameter.ondelay | 40 | "Driver parameter: | Price Expires 30 August 2022 [Page 51] Internet-Draft UPS management protocol February 2022 | | | " | +-------------------------------+------------+--------------------+ | driver.parameter.pollfreq | 30 | "Driver parameter: | | | | " | +-------------------------------+------------+--------------------+ | driver.parameter.pollinterval | 2 | "Driver parameter: | | | | " | +-------------------------------+------------+--------------------+ | driver.parameter.port | auto | "Driver parameter: | | | | " | +-------------------------------+------------+--------------------+ | driver.parameter.synchronous | no | "Driver parameter: | | | | " | +-------------------------------+------------+--------------------+ | driver.parameter.vendorid | 0999 | "Driver parameter: | | | | " | +-------------------------------+------------+--------------------+ | driver.version | 2.7.4 | "Driver version - | | | | NUT release" | +-------------------------------+------------+--------------------+ | driver.version.data | HID 1.39 | "" | +-------------------------------+------------+--------------------+ | driver.version.internal | 0.41 | "Internal driver | | | | version" | +-------------------------------+------------+--------------------+ | input.transfer.high | 264 | "High voltage | | | | transfer point | | | | (V)" | +-------------------------------+------------+--------------------+ | input.transfer.low | 184 | "Low voltage | | | | transfer point | | | | (V)" | +-------------------------------+------------+--------------------+ | outlet.1.desc | PowerShare | "Outlet | | | Outlet 1 | description" | +-------------------------------+------------+--------------------+ | outlet.1.id | 2 | "Outlet system | | | | identifier" | +-------------------------------+------------+--------------------+ | outlet.1.status | on | "Outlet switch | | | | status" | +-------------------------------+------------+--------------------+ | outlet.1.switchable | no | "Outlet switch | | | | ability" | +-------------------------------+------------+--------------------+ | outlet.2.desc | PowerShare | "Outlet | | | Outlet 2 | description" | +-------------------------------+------------+--------------------+ Price Expires 30 August 2022 [Page 52] Internet-Draft UPS management protocol February 2022 | outlet.2.id | 3 | "Outlet system | | | | identifier" | +-------------------------------+------------+--------------------+ | outlet.2.status | on | "Outlet switch | | | | status" | +-------------------------------+------------+--------------------+ | outlet.2.switchable | no | "Outlet switch | | | | ability" | +-------------------------------+------------+--------------------+ | outlet.desc | Main | "Outlet | | | Outlet | description" | +-------------------------------+------------+--------------------+ | outlet.id | 1 | "Outlet system | | | | identifier" | +-------------------------------+------------+--------------------+ | outlet.power | 25 | "" | +-------------------------------+------------+--------------------+ | outlet.switchable | no | "Outlet switch | | | | ability" | +-------------------------------+------------+--------------------+ | output.frequency.nominal | 50 | "Nominal output | | | | frequency (Hz)" | +-------------------------------+------------+--------------------+ | output.voltage | 230.0 | "Output voltage | | | | (V)" | +-------------------------------+------------+--------------------+ | output.voltage.nominal | 230 | "Nominal output | | | | voltage (V)" | +-------------------------------+------------+--------------------+ | ups.beeper.status | enabled | "UPS beeper | | | | status" | +-------------------------------+------------+--------------------+ | ups.delay.shutdown | 20 | "Interval to wait | | | | after shutdown | | | | with delay command | | | | (seconds)" | +-------------------------------+------------+--------------------+ | ups.delay.start | 30 | "Interval to wait | | | | before | | | | (re)starting the | | | | load (seconds)" | +-------------------------------+------------+--------------------+ | ups.firmware | 02 | "UPS firmware" | +-------------------------------+------------+--------------------+ | ups.load | 20 | "Load on UPS | | | | (percent of full)" | +-------------------------------+------------+--------------------+ | ups.mfr | Example | "UPS manufacturer" | Price Expires 30 August 2022 [Page 53] Internet-Draft UPS management protocol February 2022 | | Mfg | | +-------------------------------+------------+--------------------+ | ups.model | Economy | "UPS model" | | | 1600 | | +-------------------------------+------------+--------------------+ | ups.power.nominal | 1600 | "UPS power rating | | | | (VA)" | +-------------------------------+------------+--------------------+ | ups.productid | ffff | "Product ID for | | | | USB devices" | +-------------------------------+------------+--------------------+ | ups.serial | 000000000 | "UPS serial | | | | number" | +-------------------------------+------------+--------------------+ | ups.status | OL | "UPS status" | +-------------------------------+------------+--------------------+ | ups.temperature | 27 | "UPS temperature | | | | (C)" | +-------------------------------+------------+--------------------+ | ups.timer.shutdown | 0 | "Time before the | | | | load will be | | | | shutdown | | | | (seconds)" | +-------------------------------+------------+--------------------+ | ups.timer.start | 0 | "Time before the | | | | load will be | | | | started (seconds)" | +-------------------------------+------------+--------------------+ | ups.vendorid | 0999 | "Vendor ID for USB | | | | devices" | +-------------------------------+------------+--------------------+ Table 8: Typical UPS Variables A.2. Typical UPS Readable and Writable Variables Some of the features of a UPS are represented by variables which may be tuned by the user. The following variables are typical of such tunable features. The precise list depends on the model of UPS. An implementation of a Management Daemon (2.6) acting as a utility program may provide a listing of the variables available, as well as acting on them, for example utility program upsrw as included in the NUT package (9.2). Price Expires 30 August 2022 [Page 54] Internet-Draft UPS management protocol February 2022 +========================+============+=========================+ | Variable | Typical | Default description | | | value | provided as response to | | | | the command GET DESC | +========================+============+=========================+ | battery.charge.low | 20 | "Remaining battery | | | | level when UPS switches | | | | to LB (percent)" | +------------------------+------------+-------------------------+ | input.transfer.high | 264 | "High voltage transfer | | | | point (V)" | +------------------------+------------+-------------------------+ | input.transfer.low | 184 | "Low voltage transfer | | | | point (V)" | +------------------------+------------+-------------------------+ | outlet.1.desc | PowerShare | "Outlet description" | | | Outlet 1 | | +------------------------+------------+-------------------------+ | outlet.2.desc | PowerShare | "Outlet description" | | | Outlet 2 | | +------------------------+------------+-------------------------+ | outlet.2.switchable | no | "Outlet switch ability" | +------------------------+------------+-------------------------+ | outlet.desc | Main | "Outlet description" | | | Outlet | | +------------------------+------------+-------------------------+ | outlet.power | 25 | "Description | | | | unavailable" | +------------------------+------------+-------------------------+ | output.voltage.nominal | 230 | "Nominal output voltage | | | | (V)" | +------------------------+------------+-------------------------+ | ups.delay.shutdown | 20 | "Interval to wait after | | | | shutdown with delay | | | | command (seconds)" | +------------------------+------------+-------------------------+ | ups.delay.start | 30 | "Interval to wait | | | | before (re)starting the | | | | load (seconds)" | +------------------------+------------+-------------------------+ Table 9: Typical readable and writable UPS Variables Price Expires 30 August 2022 [Page 55] Internet-Draft UPS management protocol February 2022 A.3. Typical UPS Instant Commands Some of the features of a UPS are actions known as instant commands (2.5) which may be ordered by the user. The following variables represent such instant commands. The precise list depends on the model of UPS. An implementation of a Management Daemon (2.6) acting as a utility program may provide a listing of the variables available, as well as acting on them, for example utility program upscmd as included in the NUT package (9.2). +==================+==========================================+ | Command | Meaning | +==================+==========================================+ | beeper.disable | Disable the UPS beeper | +------------------+------------------------------------------+ | beeper.enable | Enable the UPS beeper | +------------------+------------------------------------------+ | beeper.mute | Temporarily mute the UPS beeper | +------------------+------------------------------------------+ | load.off | Turn off the load immediately | +------------------+------------------------------------------+ | load.off.delay | Turn off the load with a delay (seconds) | +------------------+------------------------------------------+ | load.on | Turn on the load immediately | +------------------+------------------------------------------+ | load.on.delay | Turn on the load with a delay (seconds) | +------------------+------------------------------------------+ | shutdown.return | Turn off the load and return when power | | | is back | +------------------+------------------------------------------+ | shutdown.stayoff | Turn off the load and remain off | +------------------+------------------------------------------+ | shutdown.stop | Stop a shutdown in progress | +------------------+------------------------------------------+ Table 10: Typical Instant Commands Appendix B. The Shutdown Story for System and UPS This appendix provides background material helpful for a general understanding of the relation between system and UPS. It does not define any feature of the command-response protocol. We consider the steps involved in the shutdown and restart of a long- running unattended server protected by a single UPS. The Management Daemon (2.6) runs in the server as shown in figure Figure 9. Price Expires 30 August 2022 [Page 56] Internet-Draft UPS management protocol February 2022 ,------------------SERVER------------------, | | | ,-----, | UPS <-Commands UPS | | UPS |---| Attachment | Management | | |===| Daemon Responses-> Daemon | /-----\ '--------------------'---------------------' Internal loopback Figure 9: Long-running unattended server 1. _The public power supply is on_ -- The system runs normally. Every 5 seconds, variable ups.status reports OL. -- _Days, weeks, months go by..._ 2. _Winter storm. Tree falls on power lines. The public power supply fails_ -- The server remains operational running on the UPS battery. The Management Daemon (2.6) polls the Attachment Daemon (2.1), and detects status change OL->OB. 3. The Management Daemon (2.6) logs warning messages. The server is still operational running on the UPS battery. -- _Minutes go by..._ 4. The battery discharges below the level specified by variable battery.charge.low. The server remains operational, but the UPS battery will not last much longer. The Management Daemon (2.6) polls the Attachment Daemon (2.1), and detects status change OB->OB+LB. 5. The Management Daemon (2.6) logs the low battery event. 6. The Management Daemon (2.6) decides to call for a system shutdown. It sets status FSD in the Attachment Daemon (2.1) to call on any secondaries to shut down and waits for command GET (4.2.4) NUMATTACH (4.2.4.3) to report one single attachment, i.e. the primary itself. The Management Daemon (2.6) then issues the system shutdown command for itself. 7. The operating system's shutdown process takes over. During the system shutdown, a NUT Project (2.7) specific script or an equivalent systemd service unit runs the command upsdrvctl shutdown. This tells the UPS that it is to shut down N seconds later where the default is N=20. Note that the "shutdown" of a UPS removes power from the outlet sockets, but may not turn the UPS off completely. A delayed shutdown is sometimes audible, and the characteristic beeping of the UPS stops. Price Expires 30 August 2022 [Page 57] Internet-Draft UPS management protocol February 2022 8. The system shuts down and powers down, hopefully before the N=20 seconds have passed. 9. _N seconds after item 7_ -- The UPS shuts down, i.e., it turns off its outlet sockets when N=20 seconds have passed. With some UPS units, there is an audible "clunk". What if the public power supply returns before the UPS shuts down? The UPS unit should be able to wait a configurable time with default 30 seconds. These two timers start from the moment the UPS receives the upsdrvctl shutdown command. -- _Minutes, hours, days go by..._ 10. _Some time later, maybe much later, the public power supply returns_ -- The UPS reconnects it's outlets to send power to the protected system. 11. The system BIOS option "Restore power on AC return" or "Restore to previous state" has hopefully been selected and the system powers up. The bootstrap process of the operating system begins. 12. The operating system starts the Attachment Daemon (2.1) and the Management Daemon (2.6). The Attachment Daemon (2.1) starts the Driver (2.3) and scans the UPS. The UPS status becomes OL+LB. 13. After some time, the battery charges above the battery.charge.low threshold and the Attachment Daemon (2.1) declares the status change OL+LB->OL. We are now back in the same situation as 1 above. Appendix C. Technical Terms: Historical Differences This appendix lists the major differences between the technical terms used in this document and those used in version 2.7.4 of the NUT Project (2.7). Price Expires 30 August 2022 [Page 58] Internet-Draft UPS management protocol February 2022 +===================+===============================+ | Term in NUT 2.7.4 | Term in this document | +===================+===============================+ | ALREADY-LOGGED-IN | ALREADY-ATTACHED (Table 3) | +-------------------+-------------------------------+ | ALREADY-SSL-MODE | TLS-ALREADY-ENABLED (Table 3) | +-------------------+-------------------------------+ | LOGIN | ATTACH (4.2.1) | +-------------------+-------------------------------+ | LOGOUT | DETACH (4.2.2) | +-------------------+-------------------------------+ | Master | Primary (2.8) | +-------------------+-------------------------------+ | NETVER | PROTVER (4.2.10) | +-------------------+-------------------------------+ | NUMLOGINS | NUMATTACH (4.2.4.3) | +-------------------+-------------------------------+ | Slave | Secondary (2.9) | +-------------------+-------------------------------+ Table 11 Appendix D. Change Log This section is to be removed before publishing as an RFC. // Ed: To be removed on publication. D.1. Changes in Version 01 1. There is exactly one newline (4.1) at the end of commands and responses. 2. Added descriptions to variables in Annex (A). 3. Added clause Events (5.2). D.2. Changes in Version 02 1. Extended acknowledgments. 2. Added reference to possible use of RFC1628 between driver and Attachment Daemon (2.1). 3. Clarified response to command LIST CLIENT. D.3. Changes in Version 03 1. Clarified description of Attachment Daemon (2.1). 2. Added Implementation status section as recommended by RFC 7942 [RFC7942]. Price Expires 30 August 2022 [Page 59] Internet-Draft UPS management protocol February 2022 3. Rewrote Section 7.2.3, Paragraph 1. 4. Clarified Appendix A, Paragraph 1 as being merely an example of variables used for a specific UPS product. 5. Added definition of in Section 4.2, Paragraph 1. D.4. Changes in Version 04 There are many changes in this version following the ISE review. See reply to ISE review: http://rogerprice.org/NUT/ISE-comments- 2021-06-14.reply.html Among other changes are: 1. Section (7) becomes "Codepoint Management". 2. Editorial cleanup. All