Glossary

OT terms explained for people who already know networks. Each one ends with why it matters for the wireless design.

A

AFC (automated frequency coordination): A database service that tells a 6 GHz standard-power access point which channels and how much power it may use at its surveyed location, so it does not interfere with licensed microwave links.
AGV (automated guided vehicle): A driverless vehicle that moves material under automatic control, classically along a predefined path.
AMR (autonomous mobile robot): A driverless mobile robot that navigates on its own within its environment to reach specified locations, rather than following a fixed path.

B

Black channel: The principle that a safety protocol treats everything between two safety devices, including switches, routers, and radios, as unproven, and detects transmission errors end to end itself.

C

Cell/area zone: A term from the Converged Plantwide Ethernet (CPwE) design guides for one functional area of the plant floor, spanning Purdue Levels 0 through 2, where IACS devices exchange control traffic.
CIP (Common Industrial Protocol): ODVA's media-independent, object-oriented application protocol for industrial automation, carried by EtherNet/IP, DeviceNet, ControlNet, and CompoNet.
CIP Safety: ODVA's functional safety extension to CIP, which carries safety data between safety devices over standard networks, wired or wireless, under the black channel principle.
CRTL (connection reaction time limit): In CIP Safety, the maximum age a safety packet may reach before the consuming device declares a connection fault and places the connection's data in the safe state.
Cycle time: The period of a repeating control activity, such as one execution of a controller task or one round of cyclic I/O exchange on the network.

D

Determinism: The property of a network or system that delivers within a guaranteed worst-case time, every time, rather than fast on average.
DFS (dynamic frequency selection): The rule that requires a 5 GHz access point on radar-shared channels to listen for radar before using a channel, leave it when radar is detected, and stay off it for a set period.

E

EAP and 802.1X (Extensible Authentication Protocol and IEEE 802.1X): 802.1X is the port access control framework that keeps a client off the network until it authenticates, and EAP is the step-by-step exchange it carries between the client, the access point and the RADIUS server.
Emergency stop (E-stop): A stop function started by a single human action, usually a latching red mushroom button, for use when the normal stop is not enough.
EtherNet/IP: ODVA's adaptation of CIP to standard Ethernet and TCP/IP, used for cyclic I/O, controller-to-controller data, and configuration traffic.

F

Fast BSS transition, FT (802.11r): A roaming method in which a client reuses key material it already holds, so moving to the next access point needs only a short authentication and reassociation exchange instead of a full 802.1X login.
Fleet manager (fleet control): The central software that assigns orders to a fleet of AGVs or mobile robots, plans their routes, manages traffic between them, and tracks their state.

H

HMI (human-machine interface): The screen, panel, or software an operator uses to watch a machine or process and adjust its controller.

I

I/O (input/output): The sensors, actuators, and modules that connect a controller to the physical process, and the data exchanged with them.
IACS (industrial automation and control system): The IEC 62443 umbrella term for the control systems, their networks, and the associated systems that run industrial processes, from PLCs and SCADA to safety instrumented systems.
IDMZ (industrial demilitarized zone): A buffer network between the plant's industrial zone and the enterprise network, where traffic from each side terminates instead of passing straight through.
ISA/IEC 62443: The series of standards that defines requirements and processes for securing industrial automation and control systems, addressed to asset owners, integrators, service providers, and product suppliers.

J

Jitter (packet delay variation): Variation in delay from one packet to the next; in industrial control, how far the arrival of cyclic data wanders from its nominal interval.

L

Line stop: A halt of a production line, either triggered on purpose so a problem is fixed before it spreads, or forced by a failure somewhere along the line.
Loss-of-comms behavior (loss of communication behavior): What a device, vehicle, or controller does when its connection times out: which state its outputs take, whether it stops or carries on, and how it recovers.

M

MES (manufacturing execution system): Plant-level software that manages manufacturing operations, sitting between business planning systems and the control layer at ISA-95 Level 3.
Modbus TCP (Modbus TCP/IP): The Modbus request/response messaging protocol carried over a TCP connection between a client and a server.

O

OPC UA (OPC Unified Architecture): A platform-independent standard from the OPC Foundation for exchanging industrial data with information models, built-in security, and both client/server and publish/subscribe communication.
OT (operational technology): Programmable systems and devices that monitor or control physical equipment and processes, as opposed to IT, which handles data for people.

P

PLC (programmable logic controller): A solid-state industrial controller with user-programmable memory that runs logic, timing, counting, and control functions against its inputs and outputs.
PROFINET: PI's industrial Ethernet standard for cyclic IO data exchange between IO controllers and IO devices, standardized in IEC 61158 and IEC 61784.
PROFIsafe: PI's functional safety profile, standardized as IEC 61784-3-3, that carries safety data over PROFINET or PROFIBUS under the black channel principle.
Protective stop: A stop triggered automatically by a safeguard, such as an interlocked gate or a safety sensor, rather than by a person pressing an emergency stop.
Purdue model (Purdue Enterprise Reference Architecture): A layered reference model that sorts industrial systems into levels, from the physical process and field devices at the bottom to business systems at the top, widely used to plan OT network segmentation.

R

RPI (requested packet interval): The rate, set per connection, at which an EtherNet/IP controller and a device exchange cyclic I/O data.

S

Safe state: The predefined condition a safety function drives a machine or process into when it detects a hazard or a fault; on most machines, de-energized outputs.
Safety PLC (safety controller): A controller designed and certified to execute safety functions to a stated SIL or PL, often running standard control alongside in the same device.
Safety reaction time (system reaction time): The worst-case time from a safety-related event, or a fault, until the system is in its safe state.
SCADA (supervisory control and data acquisition): Systems that gather data from and send supervisory commands to dispersed field sites, such as pipelines and power grids, over long-distance links.
SIL (safety integrity level) and PL (performance level): Two rating scales for how reliably a safety function must perform: SIL under IEC 61508 and its sector standards, and PL under ISO 13849-1.
Stopping distance (safety distance): How far a hazard keeps moving after a stop is demanded; for fixed machines it drives the minimum distance between a safeguard and the hazard.

T

Timeout multiplier: The factor that, multiplied by a connection's packet interval, sets how long the connection may go without a valid packet before it times out.
TSN (Time-Sensitive Networking): A set of IEEE 802.1 standards that give Ethernet deterministic service: bounded latency, low packet delay variation, and low loss for scheduled traffic.

U

Update time (PROFINET): In PROFINET, the configured interval at which an IO controller and an IO device exchange cyclic IO data, set per device.

W

Watchdog (watchdog time): A timer that declares a connection or task failed when the expected data or completion does not arrive before it expires.
WMM access category (AC): One of four transmit queues in Wi-Fi Multimedia (voice, video, best effort, background), each with its own channel-contention settings that make winning the channel more or less likely.
WMS (warehouse management system): Software that directs and records warehouse work, such as receiving, putaway, picking, counting, and shipping, much of it executed by workers on mobile devices.