Common Industrial Protocol
The Common Industrial Protocol (CIP) is a media-independent, object-oriented communication protocol designed for industrial automation, enabling the integration of control, safety, motion, synchronization, energy management, and information services across diverse devices and networks.[1][2] Developed by the Open DeviceNet Vendors Association (ODVA), CIP uses a producer-consumer messaging model to facilitate efficient, real-time data exchange via explicit (request-response) and implicit (connection-based) messaging, supporting interoperability through a standardized object library that defines device attributes, services, and behaviors.[1][2] Originating in 1994 as the foundation for DeviceNet and evolving through ODVA's efforts since its founding in 1995, CIP has expanded to underpin a family of networks including EtherNet/IP (introduced in 2000 over standard Ethernet), ControlNet (1997, for deterministic control), DeviceNet (over CAN bus), and CompoNet (2010, for high-density I/O).[2] This architecture allows seamless bridging and routing between networks, protecting investments in existing systems while scaling to enterprise-level Ethernet infrastructures.[1] Key advantages include reduced engineering costs via device profiles and electronic data sheets (EDS), support for up to thousands of nodes depending on the medium, and conformance testing by ODVA to ensure reliability.[2] CIP's extensibility is evident in specialized profiles such as CIP Safety (for fail-safe communication compliant with IEC 61508 SIL 3), CIP Sync (IEEE 1588-based time synchronization with sub-microsecond accuracy), CIP Motion (for coordinated multi-axis control), and CIP Security (enhanced in 2025 with pull models for secure configuration data exchange).[1][3] These features enable CIP to address modern demands like cybersecurity and energy optimization, with native translations for protocols including Modbus, HART, and IO-Link, fostering broad adoption by hundreds of vendors worldwide.[1][2]Introduction
Definition and Purpose
The Common Industrial Protocol (CIP) is an open, media-independent, object-oriented application layer protocol designed for industrial automation applications, providing a unified communication architecture across manufacturing enterprises.[4] As the upper-layer protocol for networks such as EtherNet/IP, ControlNet, DeviceNet, and CompoNet, CIP enables consistent data exchange regardless of the underlying physical or data-link layers, supporting both real-time and non-real-time communications in diverse industrial environments.[2] The primary purpose of CIP is to enable seamless integration of control, safety, information, and network management functions, supporting interoperability among devices from multiple vendors.[1] By standardizing object behaviors across devices, CIP ensures that the same object or group of objects functions identically regardless of the manufacturer, thereby reducing integration challenges and promoting vendor-neutral systems in industrial settings.[5] This interoperability focus addresses the limitations of proprietary protocols, allowing for consistent messaging in diverse industrial networks and avoiding isolated silos that hinder cross-vendor compatibility.[1] At its core, CIP emphasizes real-time data exchange, device abstraction through objects, and scalability from field devices to enterprise systems.[6] The protocol's object-oriented design abstracts device functionalities into reusable components, facilitating efficient configuration and control, while its scalable architecture accommodates simple sensors without excessive overhead and extends to complex enterprise integrations.[2] This structure supports a coherent framework for I/O control, data collection, and safety communications across multiple networks.[1]Scope and Applications
The Common Industrial Protocol (CIP) serves as an application-layer protocol that is media-independent, allowing it to adapt to various physical and data link layers while supporting both real-time control and non-real-time information exchange within industrial automation hierarchies.[2] This adaptability enables CIP to facilitate efficient communication across diverse devices, from low-level sensors and actuators to higher-level systems, promoting interoperability in complex automation environments.[1] CIP finds primary applications in manufacturing for device-level control, such as connecting programmable logic controllers (PLCs) to sensors and actuators in assembly lines for precise monitoring and operation.[2] It also supports process automation, motion control for synchronized operations, and enterprise integration, where it enables data flow from shop-floor equipment to business systems via standard Ethernet infrastructure.[1] These uses leverage CIP's capabilities in areas like safety, energy management, and synchronization to optimize industrial processes.[5] In industry sectors, CIP is widely deployed in discrete manufacturing for assembly and packaging operations, process industries for continuous production flows, and utilities for monitoring and control of infrastructure.[1] For instance, in utilities, it supports real-time data exchange between control units and field devices to ensure reliable energy distribution.[2] A key aspect of CIP's scope is its role in enabling "information-enabled manufacturing" by bridging operational technology (OT) with information technology (IT), allowing seamless integration of plant-floor data into enterprise-level analytics and decision-making.[5] This convergence has been demonstrated through over 30 million deployed nodes across global installations as of 2020.[2]History
Origins and Development
The Common Industrial Protocol (CIP), originally known as the Control and Information Protocol, was developed in the early 1990s by Allen-Bradley, a division of Rockwell Automation at the time, as the application layer for DeviceNet to address the limitations of proprietary communication systems in factory automation.[7][8] DeviceNet, released in March 1994, marked CIP's initial implementation, enabling interoperable connections among sensors, actuators, and controllers in industrial environments.[8][9] This development was driven by the need for a unified, cost-effective protocol to replace vendor-specific networks that hindered multi-vendor integration in manufacturing.[2] In 1995, the Open DeviceNet Vendors Association (ODVA) was founded by industry leaders, including Rockwell Automation, to manage and promote open standards for DeviceNet and its underlying CIP protocol.[10][2] ODVA's establishment formalized CIP as a vendor-neutral foundation, facilitating broader adoption and ensuring compliance through certification programs.[11] By transferring oversight from Allen-Bradley to ODVA shortly after DeviceNet's launch, the organization emphasized interoperability across diverse automation hardware.[8] CIP's early design drew significant influence from the Controller Area Network (CAN), a robust physical and data-link layer protocol developed by Bosch in the 1980s for automotive applications, which provided a low-cost, reliable backbone for DeviceNet's implementation.[2][12] Positioned as a vendor-neutral alternative to proprietary fieldbus systems like Profibus, CIP aimed to standardize device profiles and messaging for enhanced compatibility in industrial settings.[13] The protocol's evolution began with conceptual work in the 1980s at Rockwell Automation to integrate control and information exchange, culminating in its formalization during the mid-1990s for multi-vendor environments.[2]Key Milestones
The development of the Common Industrial Protocol (CIP) began with its initial incorporation as the application layer in DeviceNet, which was released in 1994 to enable cost-effective networking for simple industrial devices such as sensors and actuators using Controller Area Network (CAN) technology.[2] In 1997, CIP was adapted to ControlNet for high-speed, deterministic applications supporting up to 99 nodes at 5 Mbaud.[2] In 1999, ODVA declared DeviceNet an official standard, solidifying CIP's role in open industrial networking.[14] The early 2000s marked a significant expansion with the adaptation of CIP to Ethernet, culminating in the EtherNet/IP specification's release in June 2001 and its commercial introduction later that year, enabling industrial automation over standard Ethernet TCP/IP at data rates up to 1 Gbit/s.[15] CIP Safety was introduced in 2005 to provide functional safety communication up to Safety Integrity Level 3 (SIL 3) per IEC 61508 across CIP networks like DeviceNet and EtherNet/IP.[16] During the 2010s, CIP saw further expansions, including the initial specification of CIP Security in 2015 for securing EtherNet/IP communications via Transport Layer Security (TLS) and Datagram Transport Layer Security (DTLS), with broader commercial adoption by 2018; the development of CIP Energy for optimizing energy usage through device-level monitoring and reporting; and the integration of Time-Sensitive Networking (TSN) standards, starting with IEEE 1588 synchronization enhancements and progressing to full TSN support in EtherNet/IP by the early 2020s for deterministic real-time performance.[17][18] As of 2025, ODVA continues to update CIP specifications with a focus on cybersecurity enhancements, such as the March 2025 release of a pull model for CIP Security configuration data in JSON format to support secure integration of non-CIP devices, alongside efforts toward IoT convergence and edge computing compatibility through expanded device profiles and conformance testing.[3]Technical Overview
Object-Oriented Design
The Common Industrial Protocol (CIP) employs an object-oriented design paradigm to model industrial devices as hierarchical collections of objects, where each object represents a distinct functional component of the device. This approach structures devices logically by encapsulating related data, behaviors, and interfaces within objects, allowing for modular representation of physical and logical elements such as sensors, actuators, or communication interfaces. Each object consists of attributes, which store data values; services, which define methods or commands for interacting with the object; and behaviors, which govern how the object responds to services.[2][5] CIP's object model follows a class-instance architecture, where classes serve as blueprints or templates defining the structure and supported services for a category of objects, identified by unique class identifiers (e.g., hexadecimal codes in predefined ranges). Predefined classes, established by the Open DeviceNet Vendors Association (ODVA), provide standardized functionality for common industrial operations, ensuring consistency across devices from different vendors. Instances, on the other hand, are specific realizations of these classes, enabling customization; for example, vendors can create user-defined instances within predefined classes (using instance IDs in ranges like 0x0064–0x00C7) to accommodate proprietary device features while adhering to the core class definition. This structure supports inheritance, where instances inherit attributes and services from their parent class, promoting reusability and reducing development overhead.[2][1] Among the core objects in CIP, the Identity Object (Class ID: 0x01) is mandatory for all devices and provides essential identification details, including vendor ID, product code, serial number, revision, and status information, facilitating device discovery and management. The Assembly Object (Class ID: 0x04) handles input/output (I/O) data by mapping attributes from multiple objects into a single, contiguous data block, optimizing real-time exchanges in producer-consumer scenarios. The Parameter Object (Class ID: 0x0F), available in full or stub variants, manages device-specific configuration parameters, allowing controlled access to attributes for setup and diagnostics without exposing the entire object model.[2][5] The object-oriented design of CIP offers significant advantages, including abstraction that conceals implementation complexities behind standardized interfaces, inheritance for consistent behavior across similar device types, and extensibility through vendor-specific extensions that integrate seamlessly with predefined elements. These features enable high interoperability among diverse industrial devices, eliminating the need for custom coding tailored to individual hardware and allowing plug-and-play integration across CIP-compatible networks.[2][1][5]Producer-Consumer Model
The producer-consumer model in the Common Industrial Protocol (CIP) enables efficient data exchange in industrial automation networks by allowing a producing device, such as a sensor, to generate data like readings or status updates and transmit it once via multicast for consumption by multiple receiving devices, such as programmable logic controllers (PLCs). This paradigm shifts from traditional point-to-point polling to a broadcast-style mechanism where the produced message is not directed to a specific consumer but made available to any subscribed device, thereby minimizing redundant transmissions and optimizing bandwidth usage.[2][4] CIP supports two primary connection types within this model: implicit connections for cyclic input/output (I/O) data exchanges and explicit connections for acyclic request-response messaging. Implicit connections facilitate periodic, real-time data transfers using predefined paths and triggers, while explicit connections handle on-demand interactions, such as configuration or diagnostics, both managed through unique connection IDs (CIDs) assigned during establishment via services like ForwardOpen. These CIDs ensure reliable identification and isolation of data flows between producers and consumers, preventing interference in multi-device environments.[2][4][5] Data flow in the producer-consumer model accommodates both deterministic and flexible patterns, with cyclic exchanges supporting real-time control loops through regular, time-based transmissions of produced data, often triggered by change-of-state (COS) events or fixed intervals. Event-driven flows complement this by enabling diagnostics and non-critical updates, where consumers receive notifications only when relevant data changes, sourced from object attributes without requiring constant polling. This dual approach ensures timely delivery for critical operations while conserving resources for ancillary information.[2][4] The model's efficiency stems from its elimination of polling overhead, as producers transmit data once regardless of consumer count, allowing multicast delivery to scale across networks with hundreds of devices without proportional bandwidth increases. This design promotes deterministic access and predictable performance, making CIP suitable for large-scale industrial systems where traditional methods would lead to congestion and latency issues.[2][4][5]Messaging Types
The Common Industrial Protocol (CIP) employs two primary messaging types to facilitate communication in industrial automation networks: explicit messaging and implicit messaging. Explicit messaging supports non-time-critical operations, such as device configuration, diagnostics, and data retrieval, operating on a request-response basis where a client device sends a request to a target object and awaits a reply. This type is typically unconnected or connected via explicit connections and is routed through the Message Router object to reach application-specific objects.[2] The structure of an explicit message includes a service code identifying the requested action, a path segment specifying the target (comprising segments for port, logical addressing of class, instance, and attribute), optional request data, and reply data or error information in the response. Service codes are standardized, with common values such as 0x0E for Get_Attribute_Single, which retrieves the value of a specified attribute from an object, such as device identity details from the Identity Object. Other services include 0x10 for Set_Attribute_Single to modify attribute values. In the reply, the service code is the request code with the most significant bit set (e.g., 0x0E becomes 0x8E for success), followed by a general status code (0x00 indicates success) and an extended status code if needed; errors, such as invalid paths, are reported with status 0x20 and corresponding extended codes.[2][19] Implicit messaging, in contrast, enables time-critical, cyclic transfer of I/O data with minimal overhead, relying on pre-established connections rather than per-message addressing. It uses a connection-based approach where data meaning is predefined during connection setup via assemblies—collections of object attributes—and transported using a Connection ID (CID) without explicit service codes or paths in the payload. This type supports real-time producer-consumer data exchange, often via multicast for efficiency in distributing inputs to multiple consumers or collecting outputs from producers.[2][19] To initiate implicit messaging connections, the Forward_Open service is invoked on the Connection Manager Object, specifying parameters such as the target connection path, output-to-target (O->T) data size for produced data, target-to-output (T->O) data size for consumed data, timeouts, and transport class triggers (e.g., for cyclic or change-of-state triggering). The service establishes the CID and routes data according to the producer-consumer model, ensuring deterministic delivery for applications like motion control. Replies to Forward_Open include the new CID and confirm connection parameters, with errors handled via status codes similar to explicit messaging.[2]| Service Example | Service Code | Purpose | Key Parameters (for Forward_Open) |
|---|---|---|---|
| Get_Attribute_Single | 0x0E | Retrieve single attribute value | Path to object/attribute; no data |
| Set_Attribute_Single | 0x10 | Modify single attribute value | Path; new attribute data |
| Forward_Open | 0x54 (request), 0xD4 (reply) | Establish explicit/implicit connection | Connection timeout, O->T size, T->O size, target path, CID generation |