Uninterruptible Power Supply (UPS) Management Protocol -- Commands and Responses
draft-rprice-ups-management-protocol-02
The information below is for an old version of the document.
| Document | Type |
This is an older version of an Internet-Draft that was ultimately published as RFC 9271.
|
|
|---|---|---|---|
| Author | Roger Price | ||
| Last updated | 2021-03-06 (Latest revision 2021-02-18) | ||
| RFC stream | (None) | ||
| Formats | |||
| IETF conflict review | conflict-review-rprice-ups-management-protocol, conflict-review-rprice-ups-management-protocol, conflict-review-rprice-ups-management-protocol, conflict-review-rprice-ups-management-protocol, conflict-review-rprice-ups-management-protocol, conflict-review-rprice-ups-management-protocol | ||
| Stream | Stream state | (No stream defined) | |
| Consensus boilerplate | Unknown | ||
| RFC Editor Note | (None) | ||
| IESG | IESG state | Became RFC 9271 (Informational) | |
| Telechat date | (None) | ||
| Responsible AD | (None) | ||
| Send notices to | (None) |
draft-rprice-ups-management-protocol-02
IETF R. Price, Ed.
Internet-Draft Network UPS Tools Project
Intended status: Informational 6 March 2021
Expires: 7 September 2021
Uninterruptible Power Supply (UPS) Management Protocol -- Commands and
Responses
draft-rprice-ups-management-protocol-02
Abstract
This text 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 takes system shutdown decisions. The commands and responses
described by this text are exchanged between the UPS Attachment
Daemon and the Management Daemon. Current practice leads to weak
security and this is addressed in the Security and IANA
Considerations.
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 7 September 2021.
Copyright Notice
Copyright (c) 2021 IETF Trust and the persons identified as the
document authors. All rights reserved.
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This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights
and restrictions with respect to this document. Code Components
extracted from this document must include Simplified BSD License text
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provided without warranty as described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. How to read this text . . . . . . . . . . . . . . . . . . 4
1.2. Current practice . . . . . . . . . . . . . . . . . . . . 4
1.3. Requirements Language . . . . . . . . . . . . . . . . . . 4
1.4. Comments . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.1. Attachment Daemon . . . . . . . . . . . . . . . . . . . . 5
2.2. Driver . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.3. Event . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.4. Instant Command . . . . . . . . . . . . . . . . . . . . . 5
2.5. Management Daemon . . . . . . . . . . . . . . . . . . . . 5
2.6. NUT (Network UPS Tools) Project . . . . . . . . . . . . . 6
2.7. Primary . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.8. Secondary . . . . . . . . . . . . . . . . . . . . . . . . 6
2.9. Session . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.10. UPS status . . . . . . . . . . . . . . . . . . . . . . . 7
2.11. UPS variable . . . . . . . . . . . . . . . . . . . . . . 7
3. Protocol overview . . . . . . . . . . . . . . . . . . . . . . 7
4. Protocol specification . . . . . . . . . . . . . . . . . . . 9
4.1. Notation used in this specification . . . . . . . . . . . 9
4.2. Commands . . . . . . . . . . . . . . . . . . . . . . . . 10
4.2.1. "FSD" . . . . . . . . . . . . . . . . . . . . . . . . 10
4.2.2. "GET" . . . . . . . . . . . . . . . . . . . . . . . . 10
4.2.2.1. "CMDDESC" . . . . . . . . . . . . . . . . . . . . 10
4.2.2.2. "DESC" . . . . . . . . . . . . . . . . . . . . . 11
4.2.2.3. "NUMLOGINS" . . . . . . . . . . . . . . . . . . . 11
4.2.2.4. "TYPE" . . . . . . . . . . . . . . . . . . . . . 11
4.2.2.5. "UPSDESC" . . . . . . . . . . . . . . . . . . . . 12
4.2.2.6. "VAR" . . . . . . . . . . . . . . . . . . . . . . 13
4.2.3. "HELP" . . . . . . . . . . . . . . . . . . . . . . . 13
4.2.4. "INSTCMD" . . . . . . . . . . . . . . . . . . . . . . 13
4.2.5. "LIST" . . . . . . . . . . . . . . . . . . . . . . . 13
4.2.5.1. "CLIENT" . . . . . . . . . . . . . . . . . . . . 14
4.2.5.2. "CMD" . . . . . . . . . . . . . . . . . . . . . . 14
4.2.5.3. "ENUM" . . . . . . . . . . . . . . . . . . . . . 15
4.2.5.4. "RANGE" . . . . . . . . . . . . . . . . . . . . . 15
4.2.5.5. "RW" . . . . . . . . . . . . . . . . . . . . . . 16
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4.2.5.6. "UPS" . . . . . . . . . . . . . . . . . . . . . . 16
4.2.5.7. "VAR" . . . . . . . . . . . . . . . . . . . . . . 17
4.2.6. "LOGIN" . . . . . . . . . . . . . . . . . . . . . . . 17
4.2.7. "LOGOUT" . . . . . . . . . . . . . . . . . . . . . . 18
4.2.8. "PASSWORD" . . . . . . . . . . . . . . . . . . . . . 18
4.2.9. "PRIMARY" . . . . . . . . . . . . . . . . . . . . . . 18
4.2.10. "PROTVER" . . . . . . . . . . . . . . . . . . . . . . 18
4.2.11. "SET" . . . . . . . . . . . . . . . . . . . . . . . . 19
4.2.12. "STARTTLS" . . . . . . . . . . . . . . . . . . . . . 19
4.2.13. "USERNAME" . . . . . . . . . . . . . . . . . . . . . 19
4.2.14. "VER" . . . . . . . . . . . . . . . . . . . . . . . . 20
4.3. Error responses . . . . . . . . . . . . . . . . . . . . . 20
5. Statuses and Events . . . . . . . . . . . . . . . . . . . . . 23
5.1. Status symbols . . . . . . . . . . . . . . . . . . . . . 23
5.2. Events . . . . . . . . . . . . . . . . . . . . . . . . . 26
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 27
6.1. Namespaces used by Command, Responses, Statuses and
Variables . . . . . . . . . . . . . . . . . . . . . . . . 28
6.2. Port name and number used to manage UPS units . . . . . . 28
6.2.1. Current situation . . . . . . . . . . . . . . . . . . 28
6.2.1.1. Port nut/3493 . . . . . . . . . . . . . . . . . . 28
6.2.1.2. Port ups/401 . . . . . . . . . . . . . . . . . . 28
6.2.2. Request to IANA . . . . . . . . . . . . . . . . . . . 29
7. Security Considerations . . . . . . . . . . . . . . . . . . . 29
7.1. Agent verification . . . . . . . . . . . . . . . . . . . 29
7.2. Encryption . . . . . . . . . . . . . . . . . . . . . . . 30
7.3. Current security practice . . . . . . . . . . . . . . . . 30
7.4. Security needs . . . . . . . . . . . . . . . . . . . . . 31
7.4.1. Attachment Daemon shim . . . . . . . . . . . . . . . 31
7.4.2. Management Daemon shim . . . . . . . . . . . . . . . 31
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 32
9. Normative References . . . . . . . . . . . . . . . . . . . . 32
10. Informative References . . . . . . . . . . . . . . . . . . . 32
Appendix A. Variables and Instant Commands . . . . . . . . . . . 33
A.1. UPS variables . . . . . . . . . . . . . . . . . . . . . . 33
A.2. UPS readable and writable variables . . . . . . . . . . . 37
A.3. UPS Instant Commands . . . . . . . . . . . . . . . . . . 39
Appendix B. Change Log . . . . . . . . . . . . . . . . . . . . . 39
B.1. Changes in version 01 . . . . . . . . . . . . . . . . . . 39
B.2. Changes in version 02 . . . . . . . . . . . . . . . . . . 40
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 40
1. Introduction
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1.1. How to read this text
The editor recommends that you read the HTML version of this text.
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.
|
| // Ed: To be removed. The Idnits tool signals false positives
| when
| // reading variable names such as "ups.delay.shutdown". It
| wrongly
| // assumes that they are domain names and applies RFC2606 which
| calls
| // for use of domain names such as "example.com"
1.2. Current practice
This text documents UPS management techniques and current UPS
management practice published by the NUT Project (2.6) which has been
operational since 1998.
Since May 2002, the protocol described by this text has been
operating on IANA port nut/3493 running over TCP.
| Historically, the previous number 3305 was a relic of the
| original code's ancestry, and conflicted with other services.
| UDP support was dropped in July 2003. It had been deprecated
| for some time and was only capable of the simplest query
| commands as authentication is impossible over a UDP socket.
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. Comments
The editor welcomes comments. Technical matters should be addressed
to the NUT Project (2.6)'s mailing list [mailinglist]. Editorial
matters may be addressed directly to the editor, email:
"ietf@rogerprice.org" .
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2. Terminology
The following technical terms appear in this text.
2.1. Attachment Daemon
The Attachment Daemon talks to the UPS units or other power devices
often through a Driver (2.2) 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 2.10. A
Management Daemon (2.5) may consult the abstracted view using the
commands described in this text. Although the term "Attachment
Daemon" includes the word "daemon" nothing requires that it be
implemented as a detached software service. An Attachment Daemon
must support statuses (2.10) OB and OL. It must also support status
LB if the UPS provides such information.
2.2. Driver
A Driver is that part of an Attachment Daemon which is specific to
the 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 text
considers the driver to be part of the Attachment Daemon, current
practice is to see it as a separate software unit running as an
unattached daemon "in front of" the Attachment Daemon. The protocol
between the driver and the attachment daemon may use [RFC1628].
2.3. Event
An Event is a change in UPS status (2.10) detected by the Management
Daemon (2.5)
2.4. Instant Command
A command which when sent to the Attachment Daemon (2.1) causes the
hardware to immediately perform a function. For example "INSTCMD
su700 test.panel.start"
2.5. Management Daemon
The Management Daemon is primarily responsible for managing the
hardware and the system reaction to power loss. 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 a calling for a system shutdown. Although the term
includes the word "daemon" nothing requires that it be implemented as
a detached software service. The Management Daemon may also provide
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administrative functions such as a graphic interface to view the
hardware activity.
2.6. NUT (Network UPS Tools) Project
The primary goal of the NUT 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 mailing list [mailinglist] and a web site [NUT].
2.7. Primary
When a power device such as a UPS unit supplies power to more than
one system, the one to which the data lead is connected is known as
the primary. The others are secondary. See figure 4. Common
current practice for system administrators is to consider the
Management Daemon (2.5) 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".
2.8. Secondary
When a hardware device such as a UPS unit supplies power to more than
one system, the one to which the data lead is connected is known as
the Primary (2.7). 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 (2.5) 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".
2.9. Session
The Management Daemon (2.5) may open a 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 (2.4) which
turns off a UPS outlet. Other than the commands and responses used,
the details of session management are outside the scope of this text.
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2.10. 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" "OVER"
"RB" "RB" "TEST" "TRIM"}. The symbols "TICK" and "TOCK" are
experimental additions to the status and are not in common current
practice. See the appendix (5.1) which specifies each of these
symbols. The statuses "LB", "OB" and "OL" are considered fundamental
and are supported for all units. Other statuses depend on the
feature set of the hardware.
2.11. UPS variable
The features provided by each UPS are represented by variables giving
the current value attached to that feature. The UPS variable is an
abstraction of the UPS hardware configuration and activity maintained
by the Attachment Daemon (2.1). See the appendix (Section A.1,
Paragraph 1) which provides a non exhaustive list of variables. For
example the variable "battery.charge" contains the current charge of
the UPS battery as a percentage value.
3. Protocol overview
Figure 1 shows a reference configuration in which the command/
response protocol applies. The UPS shown is representative of all
power devices,
"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. The
data link may use [RFC1628].
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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 (2.5). 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 Management Daemon and
the Attachment daemon. The Management Daemon is known as the
*client*. It 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 (2.5)
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
system setup. This is becoming more prevalent with the availability
of low cost processors able to run the Attachment Daemon (2.1)
"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
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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 (2.7) system. The others have only power
connections ("===") to the UPS, and each is known as a Secondary
(2.8). A Secondary (2.8) 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 (2.5) 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
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 (2.5) include an internal state machine; for example to assist
the system shutdown of a complex installation. However the
management protocol used between them is effectively stateless. Most
responses received by the Management Daemon (2.5) are sufficient in
themselves, and at most require knowledge of the previous response to
that command. 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 (2.5)
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.
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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
(SP) SPACE.
4.2. Commands
4.2.1. "FSD"
A Management Daemon (2.5) which is Primary (2.7) and has the required
authority, uses this command to set status symbol "FSD" in the
Attachment Daemon (2.1). Current practice uses the symbol to tell
each Secondary (2.8) system to shut down. It has the same value as
the pair of status symbols "OB" "LB".
Command: "FSD <upsname>" The response is: "OK FSD-SET" if
the command is successful.
Current practice requires that an application introduce security
controls in its session management to defend against abusive use of
this command. The details are outside the scope of this text.
4.2.2. "GET"
Retrieve a single response from the server. The possible sub-
commands are:
4.2.2.1. "CMDDESC"
Command: "GET CMDDESC <upsname> <cmdname>"
Response: CMDDESC <upsname> <cmdname> "<description>"
For example: "GET CMDDESC su700 load.on" and response "CMDDESC su700
load.on "Turn on the load immediately""
This is like "DESC", but it applies to an instant command (2.4).
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4.2.2.2. "DESC"
Command: "GET DESC <upsname> <varname>"
Response: "DESC <upsname> <varname> "<description>""
where <description> 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""
4.2.2.3. "NUMLOGINS"
Command: "GET NUMLOGINS <upsname>"
Response: "NUMLOGINS <upsname> <value>"
where <value> is the number of clients which have succeeded in doing
a LOGIN to this UPS.
For example command "GET NUMLOGINS su700" and response "NUMLOGINS
su700 1"
This information may be needed by the Management Daemon (2.5) to
determine how many clients are still connected when starting the
system shutdown process.
4.2.2.4. "TYPE"
Command: "GET TYPE <upsname> <varname>"
Response: "TYPE <upsname> <varname> <type>..."
where <type> 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"
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+==============+============================================+
| Type | Meaning |
+==============+============================================+
| RW | This variable may be set to another value |
| | with command "SET" |
+--------------+--------------------------------------------+
| ENUM | An enumerated type, which supports |
| | specific pre-determined 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 (4.2.5.4) |
+--------------+--------------------------------------------+
| NUMBER | This is a single numeric value, either |
| | integer or float |
+--------------+--------------------------------------------+
Table 1: Variable types
Notes:
* "ENUM", "STRING:n" and "RANGE", are usually associated with "RW",
but not always. The default <type>, when omitted, is numeric, so
either integer or float. Each Driver (2.2) 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 invalid.
4.2.2.5. "UPSDESC"
Command: "GET UPSDESC <upsname>"
Response: "UPSDESC <upsname> "<description>""
where <description> 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""
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This can be used to provide human-readable descriptions instead of a
cryptic "upsname@hostname" string.
4.2.2.6. "VAR"
Command: "GET VAR <upsname> <varname>"
Response: "VAR <upsname> <varname> "<value>""
For example command "GET VAR su700 ups.status" and response "VAR
su700 ups.status "OB LB""
4.2.3. "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"
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 LOGIN LOGOUT
LOGOUT USERNAME PASSWORD STARTTLS
4.2.4. "INSTCMD"
Send an instant command (2.4) to the UPS.
Command: "INSTCMD <upsname> <cmdname>" The response is:
"OK"
where "<upsname>" is the name of the UPS and "<cmdname>" is the
instant command (2.4) to be issued to that UPS.
For example the command: "INSTCMD su700 test.panel.start" and the
response "OK"
4.2.5. "LIST"
The "LIST" commands all produce a response with a common container
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.
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The formatting may seem a bit redundant, but it makes a different
form of client possible. A client can send a "LIST" query and then
go off and wait for the response. When it arrives, the Management
Daemon (2.5) doesn't need a complicated state machine to remember
which list is which.
The possible subcommands are:
4.2.5.1. "CLIENT"
The command calls for the Attachment Daemon (2.1) to report all the
current Management Daemon (2.5) clients of a given UPS. See command
LOGIN (4.2.6).
Command: "LIST CLIENT <upsname>" The response is
BEGIN LIST CLIENT <upsname>
CLIENT <upsname> <client_IP_address>
...
END LIST CLIENT <upsname>
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
4.2.5.2. "CMD"
The command calls for the Attachment Daemon (2.1) to report a list of
each UPS instant command (2.4) which the Management Daemon (2.5) may
sent to the Attachment Daemon (2.1). This instant command (2.4) list
is the abstracted view of the UPS hardware capabilities. An
economical UPS will support few or no instant command (2.4) but a
professional model should support more.
Command: "LIST CMD <upsname>" The response is:
BEGIN LIST CMD <upsname>
CMD <upsname> <cmdname>
...
END LIST CMD <cmdname>
where "<upsname>" is the name of the UPS, and "<cmdname>" is the name
of the command which may be issued to the UPS.
For example the command: "LIST CMD su700" and the response:
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BEGIN LIST CMD su700
CMD su700 load.on
CMD su700 test.panel.start
...
END LIST CMD su700
4.2.5.3. "ENUM"
The command calls for the Attachment Daemon (2.1) to report the set
of possible values of a UPS variable which has predetermined values.
Command: "LIST ENUM <upsname> <varname>" The response is:
BEGIN LIST ENUM <upsname> <varname>
ENUM <upsname> <varname> "<value>"
...
END LIST ENUM <upsname> <varname>
where "<upsname>" is the name of the UPS, "<varname>" is the UPS
variable and "<value>" is one of the possible values of the UPS
variable. Note 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
4.2.5.4. "RANGE"
The command calls for the Attachment Daemon (2.1) to report the
interval in which valid values of a UPS variable lie.
Command: "LIST RANGE <upsname> <varname>" The response is:
BEGIN LIST RANGE <upsname> <varname>
RANGE <upsname> <varname> "<min>" "<max>"
...
END LIST RANGE <upsname> <varname>
where "<upsname>" is the name of the UPS, "<varname>" is the UPS
variable and {"<min>","<max>"} is the interval of valid values of the
UPS variable. Note that the U+0022 QUOTATION MARK characters are
part of the response.
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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" "100"
RANGE su700 input.transfer.low "102" "105"
...
END LIST RANGE su700 input.transfer.low
4.2.5.5. "RW"
The command calls for the Attachment Daemon (2.1) to report a list of
the UPS variables associated with a given UPS which may be read and
written by the Management Daemon (2.5). These variables are the
abstracted view of the UPS hardware capabilities. An economical UPS
will support few variables but a professional model should support at
least the variables which are needed for automatic shutdown and
restart.
Command: "LIST RW <upsname>" The response is:
BEGIN LIST RW <upsname>
RW <upsname> <varname> "<value>"
...
END LIST RW <upsname>
where "<upsname>" is the name of the UPS, "<varname>" is the UPS
variable and "<value>" is the value of the UPS variable. Note that
the U+0022 QUOTATION MARK characters are part of the response.
For example the command: "LIST RW su700" and the response:
BEGIN LIST RW su700
RW su700 output.voltage.nominal "115"
RW su700 ups.delay.shutdown "020"
...
END LIST RW su700
4.2.5.6. "UPS"
Command: "LIST UPS" The response is:
BEGIN LIST UPS
UPS <upsname> "<description>"
...
END LIST UPS
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where <upsname> is the name of a UPS, and <description> is the value
of 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 <upsname>
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
4.2.5.7. "VAR"
Command: "LIST VAR <upsname>" The response is:
BEGIN LIST VAR <upsname>
VAR <upsname> <varname> "<value>"
...
END LIST VAR <upsname>
where "<upsname>" is the name of the UPS, "<varname>" is the UPS
variable and "<value>" is the value of the UPS variable. Note that
the U+0022 QUOTATION MARK characters are part of the response.
The response to this command lists the UPS variables 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 "APC"
VAR su700 ups.mfr.date "10/17/96"
...
END LIST VAR su700
4.2.6. "LOGIN"
The Attachment Daemon (2.1) provides facilities to limit access to
the UPS unit(s) to which it is attached. A system administrator
performs a login to open a Session (2.9) and gain access to a UPS,
and a logout when the Session (2.9) is no longer needed.
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Command: "LOGIN <upsname>" The response is "OK" if the
login is successful.
| Current practice is for the command "LOGIN" to allow connection
| to the Attachment Daemon (2.1). If there are two UPS units
| attached to the Attachment Daemon (2.1) logging into the first
| will automatically log into the second as well.
4.2.7. "LOGOUT"
The Attachment Daemon (2.1) provides facilities to limit access to
the UPS unit(s) to which it is attached. A system administrator
performs a login to open a Session (2.9) and gain access, and a
logout when the Session (2.9) is no longer needed. The command
"LOGOUT" allows the system administrator to disconnect gracefully.
Command: "LOGOUT" with the response "OK Goodbye" if the disconnection
was successful.
4.2.8. "PASSWORD"
The Management Daemon (2.5) specifies a password required to enter a
Session (2.9) with the Attachment Daemon (2.1).
Command: "PASSWORD <password>" The response is: "OK" if the
command is successful.
4.2.9. "PRIMARY"
The Attachment Daemon (2.1) uses this command within a Session (2.9)
to claim that it is a Primary (2.7) and has the required authority to
perform such critical actions as setting status symbol "FSD".
Command: "PRIMARY <upsname>" with response: "OK" if the Attachment
Daemon (2.1) does have such authority.
where "<upsname>" is the name of the UPS.
| 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"
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For example, the following command line sequence in the Attachment
Daemon (2.1):
netcat localhost 3493
PROTVER
1.2
| Note: Historically, this command was known as "NETVER" and
| current practice is to use "NETVER" instead of "PROTVER"
4.2.11. "SET"
The command calls for the Attachment Daemon (2.1) to set a UPS
variable to a given value. Whether this has an effect on the UPS
hardware is specific to the Driver (2.2) and the UPS model.
Command: "SET VAR <upsname> <varname> "<value>"" The
response is: "OK"
where "<upsname>" is the name of the UPS, "<varname>" is the UPS
variable and "<value>" is the value to be assigned to the UPS
variable. Note that the U+0022 QUOTATION MARK characters are part of
the command.
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.
Command: "STARTTLS" The response is: "OK STARTTLS" if the
command is successful.
4.2.13. "USERNAME"
The Session (2.9) may require that the Management Daemon (2.5)
identifies a "UPS management user" who has been authorized to send
commands to the Attachment Daemon (2.1). In current practice, this
"user" is specific to UPS management and is not a user of the
operating system. The technique for specifying this UPS management
user is specific to the implementation, and may be done with a
configuration file.
Command: "USERNAME <username>" The response is "OK" if the
command is successful.
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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"
For example, the following command line sequence:
netcat localhost 3493
VER
Network UPS Tools upsd 2.7.4 - http://www.networkupstools.org/
4.3. Error responses
Error responses have the following format:
ERR <error-name> [<extra>]
where "<error-name>" is a single word token taken from the 27
characters A-Z and HYPHEN-MINUS U+002D. Implementations may if
needed add an additional optional "<extra>". Current practice does
not make use of this possibility.
The "<error-name>" may have one of the following values:
+==============================+=================================+
| The error name token | Meaning |
| "<error-name>" | |
+==============================+=================================+
| ACCESS-DENIED | The client's host and/or |
| | authentication details |
| | (username, password) are not |
| | sufficient to execute the |
| | requested command. |
+------------------------------+---------------------------------+
| ALREADY-LOGGED-IN | The client has already sent a |
| | successful "LOGIN" command for |
| | a given UPS and can't do it |
| | again. |
| | |
| | Note: Current practice is to |
| | impose a limit of one "LOGIN" |
| | record per connection. If |
| | there are two UPS's attached to |
| | the Attachment Daemon (2.1), |
| | logging into one of them |
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| | automatically logs into the |
| | other as well. See command |
| | LOGIN (4.2.6). |
+------------------------------+---------------------------------+
| ALREADY-SET-PASSWORD | The client has already supplied |
| | a PASSWORD and is attempting to |
| | repeat the command in the same |
| | Session (2.9). |
+------------------------------+---------------------------------+
| ALREADY-SET-USERNAME | The client has already supplied |
| | a USERNAME, and is attempting |
| | to repeat the command within |
| | the same Session (2.9). |
+------------------------------+---------------------------------+
| ALREADY-SSL-MODE | TLS/SSL mode is already enabled |
| | on this connection, so the |
| | Attachment Daemon (2.1) can't |
| | start it again. |
+------------------------------+---------------------------------+
| CMD-NOT-SUPPORTED | The specified UPS doesn't |
| | support the instant command |
| | (2.4) command. |
+------------------------------+---------------------------------+
| DATA-STALE | The Attachment Daemon (2.1) is |
| | connected to the Driver (2.2) |
| | 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 |
| | (2.5) with variables on stale |
| | units to avoid false readings. |
| | |
| | This generally means that the |
| | Driver (2.2) is running, but it |
| | has lost communication with the |
| | hardware. Check the physical |
| | connection to the equipment. |
+------------------------------+---------------------------------+
| DRIVER-NOT-CONNECTED | The Attachment Daemon (2.1) |
| | can't perform the requested |
| | command, since the Driver (2.2) |
| | for that UPS is not connected. |
| | This usually means that the |
| | driver is not running, or if it |
| | is, is misconfigured. |
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+------------------------------+---------------------------------+
| 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". |
+------------------------------+---------------------------------+
| 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". |
+------------------------------+---------------------------------+
| INSTCMD-FAILED | The Attachment Daemon (2.1) |
| | failed to deliver the instant |
| | command (2.4) request to the |
| | Driver (2.2). 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 |
| | invalid in this context. This |
| | is typically caused by sending |
| | a valid command such as "GET" |
| | with an invalid subcommand. |
+------------------------------+---------------------------------+
| INVALID-PASSWORD | The client sent an invalid |
| | password. |
+------------------------------+---------------------------------+
| INVALID-USERNAME | The client sent an invalid |
| | username. |
+------------------------------+---------------------------------+
| INVALID-VALUE | The value specified in the |
| | request is not valid. This |
| | usually applies to a "SET" of |
| | an "ENUM" type which is using a |
| | value not in the list of |
| | allowed values. |
+------------------------------+---------------------------------+
| PASSWORD-REQUIRED | The command requires a password |
| | for authentication, but the |
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| | client hasn't provided one. |
+------------------------------+---------------------------------+
| READONLY | The requested variable in a |
| | "SET" command is not writable. |
+------------------------------+---------------------------------+
| SET-FAILED | The Attachment Daemon (2.1) |
| | failed to deliver the set |
| | request to the Driver (2.2). |
| | This is similar to "INSTCMD- |
| | FAILED". |
+------------------------------+---------------------------------+
| TOO-LONG | The requested value in a "SET" |
| | command is too long. |
+------------------------------+---------------------------------+
| UNKNOWN-COMMAND | The Attachment Daemon (2.1) |
| | doesn't recognize the command. |
+------------------------------+---------------------------------+
| UNKNOWN-UPS | The UPS specified in the |
| | 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 (2.11) |
| | in the command. |
+------------------------------+---------------------------------+
Table 2: 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 (2.5) 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.
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+=========+====================================================+
| Symbol | Meaning |
+=========+====================================================+
| ALARM | The UPS reports that it requires intervention. |
+---------+----------------------------------------------------+
| BOOST | The UPS has determined the voltage level of the |
| | public supply is too low, and is boosting it to |
| | the required level. The UPS continues to supply |
| | the protected system from the public supply. |
+---------+----------------------------------------------------+
| BYPASS | The UPS is feeding current directly from the |
| | public supply to the protected system. The backup |
| | facilities are disconnected. This state allows |
| | maintenance personnel to change the batteries |
| | without interrupting the protected system. |
+---------+----------------------------------------------------+
| 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". |
| | |
| | Note: "OL" does not imply "CHRG" if the battery is |
| | floating. |
+---------+----------------------------------------------------+
| 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". |
| | |
| | Note: "OB" does not imply "DISCHRG" if the battery |
| | is floating. |
+---------+----------------------------------------------------+
| FSD | This "Forced Shut Down" 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 offline, taking energy |
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| | 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 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 (2.1) provides a regular signal monitored |
| | by the Management Daemon (2.5) as a way of |
| | verifying effective end-to-end management. "TICK" |
| | and "TOCK" are companions. |
+---------+----------------------------------------------------+
| TOCK | Heartbeat. See "TICK" |
+---------+----------------------------------------------------+
| TRIM | The UPS has determined that the voltage level of |
| | the public supply is too high, and is reducing it |
| | to the required level. The UPS continues to |
| | supply the protected system from the public |
| | supply. |
+---------+----------------------------------------------------+
Table 3: UPS status symbols
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5.2. Events
A Management Daemon (2.5) deduces the occurrence of a UPS Event from
a change in the UPS status (2.10) 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". In current practice, the variable "ups.status" is
retrieved every 5 seconds. The "old" status is therefore the
previous value retrieved 5 seconds ago.
Current practice is for the Management Daemon (2.5) 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 |
| | | || | |calibrating |
+-------+---------+---------------++---------+--------+-------------+
|none | CHRG |Charging || CHRG | none |Not charging |
+-------+---------+---------------++---------+--------+-------------+
|none | COMM |UPS || COMM | none |[Note 5] |
| | |communicating || | | |
| | |("COMMOK") || | | |
+-------+---------+---------------++---------+--------+-------------+
|none | DISCHRG |Discharging || DISCHRG | none |Not |
| | | || | |discharging |
+-------+---------+---------------++---------+--------+-------------+
|none | FSD |System shutdown|| FSD | none |Shutdown |
| | |("FSD") || | |abandoned |
| | |("SHUTDOWN") || | |[Note 1] |
+-------+---------+---------------++---------+--------+-------------+
|none | LB |Low battery || LB | none |Battery not |
| | |[Note 2] || | |low |
| | |("LOWBATT") || | | |
+-------+---------+---------------++---------+--------+-------------+
|none | NOCOMM |UPS dead? || NOCOMM | none |[Note 5] |
| | |[Note 5] || | | |
| | |("COMMBAD") || | | |
| | |("NOCOMM") || | | |
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+-------+---------+---------------++---------+--------+-------------+
|none | OFF |UPS turned off || OFF | none |UPS not |
| | | || | |turned off |
+-------+---------+---------------++---------+--------+-------------+
|OB | OL |Receiving wall || OL | OB |Wall power |
| | |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 event|| TICK | none |No heartbeat |
| | |[Note 4] || | |[Note 4] |
+-------+---------+---------------++---------+--------+-------------+
|none | TOCK |Heartbeat event|| TOCK | none |No heartbeat |
| | |[Note 4] || | |[Note 4] |
+-------+---------+---------------++---------+--------+-------------+
|none | TRIM |Trimming || TRIM | none |Not trimming |
| | |voltage || | | |
+-------+---------+---------------++---------+--------+-------------+
Table 4: 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 (2.5) reception of "LB" as an order to perform an
emergency system shutdown.
3. (For future use)
4. The use of a software defined UPS to provide a heartbeat is
experimental and is not part of common current practice.
5. Current practice is: if the UPS has not responded for 15 seconds,
the Management Daemon (2.5) 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. IANA Considerations
// Ed: See Guidelines for Writing an IANA Considerations Section in
// RFCs [RFC8126]
This text raises five matters which fall within IANA Considerations:
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1. The namespaces occupied by the protocol commands (4.2) described
in this text.
2. The namespaces occupied by the protocol responses (4.3) described
in this text.
3. The namespace occupied by UPS status (2.10) names,
4. The namespace occupied by UPS variable (2.11) names,
5. The port name and port number used to manage UPS units.
6.1. Namespaces used by Command, Responses, Statuses and Variables
Current NUT Project (2.6) 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 (2.6) 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,
6.2. Port name and number used to manage UPS units
6.2.1. Current situation
See the IANA [Registry] for the latest situation.
6.2.1.1. Port nut/3493
In 2002 IANA assigned port nut/3493 to project lead Russell Kroll,
and updated the assignment to the NUT Project (2.6) itself in 2020.
6.2.1.2. 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. 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
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6.2.2. Request to IANA
The NUT Project (2.6) is mindful of IANA's position
| that the applicant MUST NOT use the requested port in
| implementations deployed for use on the public Internet prior to
| the completion of the assignment
in clause 8.1.1 of [RFC6335] and makes the following requests to
assist the security migration strategy described in Section 7.4,
Paragraph 1.
1. The NUT Project (2.6) wishes to use the existing UPS Management
Protocol as described in this text on existing port ups/401 for
full security access to the Attachment Daemon (2.1), i.e. command
"STARTTLS" must be issued, accepted and applied.
2. The NUT Project (2.6) requests that IANA consider transferring
port ups/401 to the NUT Project (2.6) and would appreciate IANA
Expert advice on this matter.
7. Security Considerations
A functioning power supply is vital to a computing system. The
Management Daemon (2.5) is able to shut down a working system and
it's power supply: this raises multiple security issues. Most of
these are well known IT issues concerning system protection and
disaster recovery, and are beyond the scope of this text. However
the protocol itself has security considerations:
1. It should not be possible for non-authorized agents to open
sessions and send mission-critical commands such as "FSD
<upsname>" 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 (2.5).
The following facilities address these requirements.
7.1. Agent verification
The protocol provides commands "LOGIN" and "PASSWORD" which allow a
Management Daemon (2.5) to authenticate itself to the Attachment
Daemon (2.1). The password needs protection from sniffing: This is
done by encrypting the traffic.
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7.2. Encryption
The protocol provides command "STARTTLS" which calls on the
Attachment Daemon (2.1) to support TLS encryption of the
communication. If this command is accepted, the Management Daemon
(2.5) must also encrypt.
At present the command "STARTTLS" is too frequently refused, and
traffic proceeds unencrypted, with for example plain text
transmission of passwords.
7.3. Current 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
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Figure 6: Integration of UPS and Attachment Daemon
7.4. 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. 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. A possible technique introduces shims
between the Attachment Daemon (2.1) and the network, and between the
network and the Management Daemon (2.5) as shown in figure 7. These
shims provide TLS support, allowing the Attachment Daemon (2.1) and
Management Daemon (2.5) 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 ?? 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
7.4.1. 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" it
1. Returns "OK" to the client and sets up TLS encapsulation.
2. Does not send "STARTTLS" to the Attachment Daemon (2.1) port
nut/3493.
All other commands and responses are passed through.
7.4.2. Management Daemon shim
The shim in front of the Management Daemon (2.5) listens for incoming
traffic on port nut/3493. When it receives the command "STARTTLS" it
1. Returns "FEATURE-NOT-CONFIGURED" to the client.
2. Sends "STARTTLS" to the Attachment Daemon (2.1) on a port to be
specified.
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All other commands and responses are passed through.
8. Acknowledgments
This text is based on the NUT Project (2.6) documentation
[developerguide]. The editor acknowledges the work of Charles
Lepple, Arjen de Korte, Arnaud Quette, Jim Klimov, Russell Kroll, and
many others who contribute to the nut-upsuser mailing list
[mailinglist].
The source for the text 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 text. The editor acknowledges the help received
from Carsten Bormann and Julian Reschke in the xml2rfc mailing list.
9. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
10. Informative References
[Bennett] "Charles Bennett Obituary", Publisher: Jagers and Sons
Funeral Home, 24 Morris Ave., Athens OH,
<https://www.legacy.com/obituaries/name/charles-bennett-
obituary?pid=174356861>.
[developerguide]
"Network UPS Tools (NUT) Project Developer Guide",
<https://networkupstools.org/docs/developer-guide.chunked/
ar01s09.html>.
[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.
[mailinglist]
"Network UPS Tools (NUT) Project Mailing List",
<https://alioth-lists.debian.net/cgi-bin/mailman/listinfo/
nut-upsuser>.
[NUT] "Network UPS Tools (NUT) Project",
<https://www.networkupstools.org>.
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[Registry] "Service Name and Transport Protocol Port Number
Registry", Publisher: IANA,
<https://www.iana.org/assignments/service-names-port-
numbers/service-names-port-numbers.xhtml>.
[RFC1628] Case, J., Ed., "UPS Management Information Base",
RFC 1628, DOI 10.17487/RFC1628, May 1994,
<https://www.rfc-editor.org/info/rfc1628>.
[RFC6335] Cotton, M., Eggert, L., Touch, J., Westerlund, M., and S.
Cheshire, "Internet Assigned Numbers Authority (IANA)
Procedures for the Management of the Service Name and
Transport Protocol Port Number Registry", BCP 165,
RFC 6335, DOI 10.17487/RFC6335, August 2011,
<https://www.rfc-editor.org/info/rfc6335>.
[RFC7991] Hoffman, P., "The "xml2rfc" Version 3 Vocabulary",
RFC 7991, December 2016,
<https://www.rfc-editor.org/info/rfc7991>.
[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/info/rfc8126>.
[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", <http://www.jclark.com/sp/sgmlnorm.htm>.
Appendix A. Variables and Instant Commands
A.1. UPS variables
The UPS variables represent the abstracted state of the UPS unit.
The number of variables depends on the sophistication of the product.
Those shown here are a typical example. An implementation of a
Management Daemon (2.5) acting as a utility program may provide a
listing of the variables available, as well as acting on them.
// Ed: NUT: upsc
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+===============================+============+====================+
| 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 | WhizBang | "" |
+-------------------------------+------------+--------------------+
| device.model | Economy | "" |
| | 1700 | |
+-------------------------------+------------+--------------------+
| device.serial | 1234567890 | "" |
+-------------------------------+------------+--------------------+
| device.type | ups | "" |
+-------------------------------+------------+--------------------+
| driver.name | usbhid-ups | "Driver name" |
+-------------------------------+------------+--------------------+
| driver.parameter.lowbatt | 37 | "Driver parameter: |
| | | <name>" |
+-------------------------------+------------+--------------------+
| driver.parameter.offdelay | 30 | "Driver parameter: |
| | | <name>" |
+-------------------------------+------------+--------------------+
| driver.parameter.ondelay | 40 | "Driver parameter: |
| | | <name>" |
+-------------------------------+------------+--------------------+
| driver.parameter.pollfreq | 30 | "Driver parameter: |
| | | <name>" |
+-------------------------------+------------+--------------------+
| driver.parameter.pollinterval | 2 | "Driver parameter: |
| | | <name>" |
+-------------------------------+------------+--------------------+
| driver.parameter.port | auto | "Driver parameter: |
| | | <name>" |
+-------------------------------+------------+--------------------+
| driver.parameter.synchronous | no | "Driver parameter: |
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| | | <name>" |
+-------------------------------+------------+--------------------+
| driver.parameter.vendorid | 0999 | "Driver parameter: |
| | | <name>" |
+-------------------------------+------------+--------------------+
| 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" |
+-------------------------------+------------+--------------------+
| 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" |
+-------------------------------+------------+--------------------+
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| 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 | WhizBang | "UPS manufacturer" |
+-------------------------------+------------+--------------------+
| ups.model | Economy | "UPS model" |
| | 1700 | |
+-------------------------------+------------+--------------------+
| ups.power.nominal | 1700 | "UPS power rating |
| | | (VA)" |
+-------------------------------+------------+--------------------+
| ups.productid | ffff | "Product ID for |
| | | USB devices" |
+-------------------------------+------------+--------------------+
| ups.serial | 000000000 | "UPS serial |
| | | number" |
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+-------------------------------+------------+--------------------+
| ups.status | OL | "UPS status" |
+-------------------------------+------------+--------------------+
| 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 5: Typical UPS Variables
A.2. 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 (2.5) acting as a utility
program may provide a listing of the variables available, as well as
acting on them.
// Ed: NUT: upsrw
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+========================+============+=========================+
| 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 6: Typical readable and writable UPS Variables
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A.3. UPS Instant Commands
Some of the features of a UPS are actions which may be ordered by the
user. The following variables represent such actions. The precise
list depends on the model of UPS. An implementation of a Management
Daemon (2.5) acting as a utility program may provide a listing of the
variables available, as well as acting on them.
// Ed: NUT: upscmd
+==================+==========================================+
| 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 7: Typical Instant Commands
Appendix B. Change Log
This section is to be removed before publishing as an RFC.
// Ed: To be removed on publication.
B.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).
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3. Added clause Event (5.2).
B.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".
Author's Address
Roger Price (editor)
Network UPS Tools Project
La Gaude
France
Phone: +33 493 24 43 57
Email: ietf@rogerprice.org
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