Modbus TCP vs. EtherNet/IP: An Engineer's Guide

Control Engineers have a lot of decisions to make, such as those surrounding the design and layout of the factory floor, machine placement, the flow of information and materials. These decisions are made with the goal of increasing efficiency and production. To do so, they must also make educated choices regarding the correct industrial protocols. Two of the most common protocols used in manufacturing are Modbus TCP and EtherNet/IP. This guide is designed to help you analyze nine factors so you can make the right decision for your operation.

Vendor Support

Perhaps the first question you should ask when choosing between Modbus TCP and EtherNet/IP is this: what other types of devices are on my network? Furthermore, consider the manufacturers of these devices. If you have a wide variety of both domestic and foreign devices, Modbus TCP is probably right for you. On the other hand, if your devices are mostly US-made, then EtherNet/IP is probably right for you.

Modbus TCP

Modbus is one of the oldest and most widely-used protocols for two reasons. First, it is an open protocol, which has led to widespread adoption in factories. Many companies offer Modbus TCP-compatible devices, software libraries, and tools. In other words, there is no shortage of vendors that can provide you support as you build and manage an industrial automation system. Secondly, it is the default protocol for many legacy devices. If your operation relies heavily on older devices, then Modbus is probably right for you.

EtherNet/IP

EtherNet/IP is also an open protocol, and is especially popular in devices made by Rockwell Automation (Allen-Bradley), as well as those made by partnered vendors. You can find extensive vendor support for Rockwell Automation PLCs, HMIs, drives, and other automation components. For this reason, EtherNet/IP is usually the way to go for factories located in North America where Rockwell is the most prominent device vendor. 

Overall rating

• Modbus TCP Rating: ★★★★★. Being one of the oldest open protocols, an enormous variety of vendors support this protocol.
• EtherNet/IP Rating: ★★★☆☆. Though Rockwell Automation is the largest vendor in North America, using EtherNet/IP makes it more challenging to use technology from overseas vendors, such as Siemens. 

Compatibility with Existing Devices

As mentioned previously, Modbus TCP is the usual choice for factories using devices from a variety of vendors, as well as old legacy devices. On the other hand, EtherNet/IP is the ideal choice for North American factories utilizing Rockwell Automation devices. To further analyze the compatibility with existing devices, you should consider each protocol’s simplicity and interoperability.

Modbus TCP

Simplicity

In comparison to other industrial protocols, Modbus TCP is rather lightweight and easy to use. For that reason, Modbus TCP is widely accepted and integrated across different types of devices and vendors.

Interoperability

Modbus TCP operates over standard Ethernet networks and uses standard TCP/IP, making it compatible with most Ethernet hardware and infrastructure.

EtherNet/IP

Simplicity

EtherNet/IP is not the most simple protocol, especially when it comes to configuring the devices and understanding the communication model. However, engineers willing to take the time to configure devices using EtherNet/IP are rewarded with added functionality and features, such as Real-Time Communication and Network Redundancy.

Interoperability

While still one of the most popular protocols used in Rockwell Automation devices, many other manufacturers have adapted their devices to accommodate EtherNet/IP. While it might not be as widespread as Modbus TCP, EtherNet/IP does ensure a level of interoperability.

Overall rating

• Modbus TCP Rating: ★★★★★. The ability to operate over standard Ethernet networks make it super compatible with a wide range of devices.
• EtherNet/IP Rating: ★★★★☆. Though an open protocol like Modbus, EtherNet/IP is more complex and requires more time to configure.

Performance 

The performance of your protocol of choice can be determined by multiple factors, including the number of nodes on your network, the amount of traffic, and device loads. 

Modbus TCP

For most industrial applications, Modbus TCP is good enough. However, because it operates over standard ethernet, you can expect limitations when it comes to bandwidth and speed. Compared to other ethernet-based protocols, Modbus TCP pales in comparison.

EtherNet/IP

If you need faster data rates and greater bandwidth, choose EitherNet/IP. Some device vendors offer features that allow you to prioritize certain types of traffic for critical applications, enhancing determinism. EtherNet/IP is also ideal for larger networks with more nodes. 

Overall rating

• Modbus TCP Rating: ★★★☆☆. Operating over standard Ethernet, Modbus TCP can have limited bandwidth and speed.
• EtherNet/IP Rating: ★★★★★. Provides faster data rates and can be used for larger networks and more nodes.

Scalability

Modbus TCP is ideal for small to medium-sized networks and simple applications. Though easy to implement and configure, as your network grows in complexity, performance may begin to suffer. EtherNet/IP is highly scalable and can handle large and intricate industrial networks.

Modbus TCP

Modbus TCP offers unmatched simplicity, allowing engineers to seamlessly configure and implement. However, when used in larger networks, it might become a limiting factor in terms of managing a vast number of devices and addressing complex network topologies efficiently. Modbus TCP supports simple network topologies, such as point-to-point or star configurations, but may not be the most suitable for highly distributed or redundant network architectures.

EtherNet/IP

EtherNet/IP is a highly-scalable industrial protocol which can support complex networks. Without compromising performance, EtherNet/IP can support large and expanding factory networks. Ethernet/IP supports various network topologies, including line, star, ring, and tree structures, which allows for flexible and robust network designs. 

Overall rating

• Modbus TCP Rating: ★★☆☆☆. Modbus TCP can only accommodate a limited number of devices before performance suffers.
• EtherNet/IP Rating: ★★★★☆. Allows you to create a large and diverse network of nodes supported by a variety of topologies.

Security Features

Modbus TCP was not made with modern security features in mind because it is such an old protocol. If your operation requires a little extra security, you may want to consider EtherNet/IP. Let’s take a look at three security features that your factory likely needs.

Modbus TCP

Authentication

Modbus TCP operates without any inherent security features, and lacks authentication mechanisms. That means anyone with network access can potentially send and receive Modbus TCP messages without restrictions.

Encryption

Modbus also lacks encryption, which means that data can be intercepted with relative ease. The likelihood of messages falling into the wrong hands is higher with Modbus than with other more modern protocols.

Access Control

Modbus lacks access control features, which allows connected devices to communicate freely with one another without limitations.

EtherNet/IP

Authentication

EtherNet/IP authentication features allow devices to verify the identity of other devices before establishing a connection. This makes it difficult for unauthorized devices to access your network.

Encryption

Mechanisms such as IPsec (Internet Protocol Security) or TLS (Transport Layer Security) protect the confidentiality of your data during transmission.

Access Control

EtherNet/IP allows administrators to restrict communication between specific devices or groups of devices, enhancing network security.

Overall rating

• Modbus TCP Rating: ★☆☆☆☆. Modbus offers very few security features as it was not designed for modern security threats. 
• EtherNet/IP Rating: ★★★★☆. EtherNet/IP keeps your network safe with encryption, access control, and authentication features.

Costs

To compare the overall costs of using Modbus TCP and EtherNet/IP, we will break costs into two categories--hardware and software costs. 

Modbus TCP

Hardware costs

There are a multitude of industrial devices and equipment that support Modbus TCP are available at competitive prices. It can also be implemented on low-cost hardware components, making it an affordable option.

Software costs

It is unlikely that you will have to purchase additional proprietary software components or licensing. There are various open-source and commercial software libraries available to implement Modbus TCP in custom applications, many of which are affordable or free.

EtherNet/IP

Hardware costs

EtherNet/IP is a more complex protocol and requires additional features and processing power to be used at its maximum potential. You can typically expect devices that support EtherNet/IP to be more expensive as they require higher-end components.

Software costs

You may have to purchase additional licensing to use certain features and software components. In fact, many custom applications will require you to purchase software development kits, which can become pricey very quickly. 

Overall rating

• Modbus TCP Rating: ★★★★★. No additional licensing or proprietary software components are required.
• EtherNet/IP Rating: ★★★☆☆.: You can expect hidden costs associated with licensing and softwares to access all the functions of this protocol.

Ease of Integration 

Modbus TCP is known for its simplicity and ease of integration. It is a straightforward protocol with a simple messaging structure. Ethernet/IP can be more complex to integrate compared to Modbus TCP. It has a more intricate messaging structure and additional layers for device-level communication.

Modbus TCP

Many industrial devices and controllers have built-in Modbus TCP support, which simplifies integration. Modbus TCP's popularity and widespread adoption mean that there is ample documentation, tutorials, and community support available.

EtherNet/IP

Ethernet/IP often requires more configuration and setup, especially when implementing advanced features such as Device Level Ring (DLR) or Quality of Service (QoS). While many vendors provide software development kits (SDKs) and tools for Ethernet/IP integration.

Overall rating

• Modbus TCP Rating: ★★★★★. Simplified integration through community support and documentation.
• EtherNet/IP Rating: ★★☆☆☆. Additional configuration is required for the enablement of certain features.

Interoperability

The choice between the two protocols should be based on the specific requirements of your application, the existing infrastructure, and the level of interoperability needed for your automation system.

Modbus TCP

As an open protocol, Modbus TCP is known for its high level of interoperability. Many device vendors offer Modbus compatibility, and this broad adoption means that devices from different vendors have an easy time communicating with one another. 

EtherNet/IP

EtherNet/IP also offers excellent interoperability as a result of its formal standardization and certification by ODVA. Devices that are certified to comply with the Ethernet/IP specifications are expected to work reliably with each other, regardless of the manufacturer. 

Overall rating

• Modbus TCP Rating: ★★★★☆. Modbus only has slight differences in how manufacturers implement the protocol, which offers great interoperability. 
• EtherNet/IP Rating: ★★★★★. EtherNet/IP works regardless of the device manufacturer, thanks to ODVA standardization. 

Application-specific Features

Application-specific features refer to capabilities or functionalities that are tailored to specific types of industrial applications or use cases. 

Modbus TCP

Simplicity

Modbus TCP is perhaps the most simple and straightforward automation protocol. If your network is smaller and has basic communication requirements, Modbus may be a good fit

Legacy Support

Modbus TCP is the perfect protocol for any network that features a lot of legacy devices because it was, as a matter of fact, made for legacy devices.

Lightweight Overhead

Modbus TCP has minimal message overhead due to its simple structure. This is perfect for networks with limited bandwidth. 

EtherNet/IP

Real-time Communication

EtherNet/IP supports real-time communication via both Cyclic I/O and Explicit Messaging. This makes it the ideal choice for situations where precise and fast data exchange is crucial.

Advanced Diagnostics

EtherNet/IP allows users to monitor network health, identify potential issues, and troubleshoot problems efficiently.

Motion Control

Complex automation systems thrive using EtherNet/IP’s motion control features. Systems using robotic arms, servo drives, and motion controllers enjoy better support for synchronized motion.

Overall rating

The features listed here between the two protocols do not trump one another. The value of these features is determined on a case-to-case basis, and are evaluated based on your network needs.

Which Protocol is Right for Me?

Unfortunately, there is not a clear-cut answer to this question as many factors must be considered. For instance, if you have a smaller network with simple requirements and a multitude of legacy devices, you would likely choose Modbus TCP. On the other hand, if your network is in need of more modern security features and has greater bandwidth requirements, you may want to consider EtherNet/IP. However, these decisions are rarely this straightforward. Thankfully, your friends at Grid Connect understand these challenges and have developed solutions to help you stay connected!

Grid Connect Helps You Stay Connected

Unigate CL Fast Ethernet Gateway

The Unigate CL Fast Ethernet Gateway allows you to connect any Modbus TCP or Modbus RTU device to your network using Ethernet. This device is ideal for operations that feature a few legacy devices that cannot justifiably be replaced. Instead, integrate them into your network with ease! We also offer the Unigate CL 2-Port EtherNet/IP Gateway. This device allows you to connect even more legacy devices to your modern Ethernet network with ease, and without losing functionality.