Advanced industrial Layer three switches help Ethernet flexibility

Advances in Ethernet help integrate plantwide network architectures. Industrial layer three switches expand Ethernet’s flexibility and security in a more securely designed network. See network design diagrams.

09/21/2010


Was it just over 10 years ago that many engineers scoffed at the idea of using Ethernet in the manufacturing environment for both control and information applications? Industry experts predicted that node cost, determinism issues, and security risks would prohibit Ethernet’s growth into manufacturing. That prediction hasn’t held true. Widespread industry adoption of Ethernet has outpaced its networking counterparts and is a key factor in the adoption rate of the EtherNet/IP industrial Ethernet network.

Rise of Ethernet

Just over a decade ago, the drive to integrate the manufacturing enterprise from the simplest device to the highest-level information system represented a task that no one network could manage.

Consequently, plant floors used multiple networks to transfer different types of data and handle the mix of requirements for discrete, process, batch, motion and safety applications. Meanwhile, standard Ethernet expanded rapidly in the commercial world. With installed nodes in the billions, manufacturers began to see the promise it held for integrating plantwide network architectures, especially as key advances removed barriers to using the technology on the factory floor. Advancements included increasing the network’s speed from 10M to 100Mbs, adding collision detection, and the introduction of full duplex and managed switch technology, to name a few.

Manufacturers began to look into the various industrial Ethernet protocols to linking the plant floor to the business enterprise and found that networks using standard Ethernet and TCP/IP, such as EtherNet/IP, have little difficulty integrating with the commercial/IT environment and can be the technology enabler for the convergence of manufacturing and enterprise-level networks. Also, EtherNet/IP integrates seamlessly with other network technologies from the ODVA organization, such as DeviceNet and ControlNet, to round out the converged network infrastructure.

All three networks share ODVA’s Common Industrial Protocol (CIP). This enables end users to integrate different systems without the need for gateways or proxies, which can increase complexity due to extra configuration and programming. This also permits increased flexibility, assures compatibility and offers ease of device integration into new and legacy systems while giving manufacturers the power to converge their communications architecture for improved operational efficiency.

By leveraging the economies of scale in a proven commercial technology, EtherNet/IP provides users with the tools needed for manufacturing applications while enabling plantwide and enterprise connectivity for data anytime, anywhere. Using common tools, components, and human assets to support a plantwide network architecture helps increase business agility, reduce training, and personnel costs, and improve asset utilization. Ethernet’s expansion into manufacturing enabled the migration from the traditional multitier network model to a more converged model. See the plantwide network diagram.

A converged network model addresses the mix of applications and data types that are transferred within the manufacturing enterprise – namely device, control and large information-based packets. One Ethernet protocol can serve multiple control and information disciplines, including discrete, process, motion, safety, and drive control, and tie the networking infrastructure together – from the device to the enterprise zone – providing countless benefits.

Traditional device- or control-level networks limit the number of network device connections; EtherNet/IP can accommodate virtually an unlimited number of devices on the network. This provides users with flexibility in designing networks that accommodate current requirements and cost-effective expansion. IT professionals prefer EtherNet/IP because it uses standard Ethernet rather than a proprietary variation. Switches, network management tools and training are compatible with what are used in the enterprise space.

Since a network infrastructure is possible with one network technology and common components, the new question is “How can I design my infrastructure to meet my needs for segmentation, security, reliability, maintainability and performance, while allowing for added capacity?”

Network design: Manage traffic effectively

Traditional industrial network models force segmentation and traffic management by function and geographic area based on the limited capacity of each network. Ethernet doesn’t have these limits and enables a mix of industrial, commercial, and business systems, and related devices, on the same network. Users who implement a converged Ethernet network must employ best practices and plan to effectively segment and structure the network. Effective design will help ensure correct traffic flow, network performance, security, and other attributes important in the network’s operation.

Designing and deploying a robust and secure network infrastructure requires protecting the integrity, availability, and confidentiality of control and information data. Establishing smaller LANs helps manage different types of network traffic; creating domains of trust to limit access to authorized personnel. These practices require a new segmentation methodology.

While users traditionally segmented networks by location, they can now segment by function. That’s because VLANs (virtual local area networks) provide traffic segmentation like separate networks did, enabling users to logically segment areas of control to increase performance and minimize network latency and jitter. See the network segmentation diagram.

Once users think beyond traditional geographic boundaries, they can engineer logical network architectures, freeing network design from the constraints of physical layout. Industrial Layer 3 switching technology plays a vital role in communicating and routing traffic. A Layer 3 switch can route traffic between and across VLANs based on IP addresses. Such flexible segmentation model directs traffic only to where it is needed.

A number of routing protocols have been developed to allow Layer 3 switches and routers to reliably route packets to their destination based on IP address. Routing protocols allow various devices to communicate and maintain viable routes between each other so that packets can always be forwarded if a viable path exists, even as connections or devices fail.

Choice of routing protocol and configuration and maintenance of the Layer 3 switches and routers can be a point of contention between manufacturing and IT personnel.

Control engineers require Ethernet switches to meet the functional and environmental requirements of manufacturing, such as ease of use, maintainability and use in harsh or hazardous locations.

IT professionals prefer Ethernet switches that support their infrastructure and security strategies and use familiar software and programming tools. EtherNet/IP doesn’t need special switches or proxies to route data between VLANs and subnets. Control engineers also can work with tools and products they are comfortable using.

Example: IT and automation programming software

Advances in industrial Ethernet switch technology provide functions and tool sets that address the needs of manufacturing and IT. For example, the Allen‑Bradley Stratix 8300 Layer 3 managed industrial switch from Rockwell Automation uses the Cisco Catalyst operating system and can be programmed using Cisco’s command line interface (CLI), providing IT engineers with the same programming and configuration tools they use today.

The Stratix 8300 switch also can be programmed using Rockwell Software’s RSLogix 5000 software, a design environment that is very familiar to manufacturing and control engineers.

With its support of inter-VLAN routing and advanced routing protocols, the industrially hardened Stratix 8300 switch allows users to integrate multiple cell/area zones across the plant and facilitate secure integration with networks at the manufacturing and enterprise levels.

The industrial hardening and modular port count offers more freedom to locate the switch closer to the application and allows for smaller network segments when needed. Cisco technology accommodates existing Cisco switches and routers and Allen-Bradley’s Stratix 8000 layer 2 industrial switches.

A converged EtherNet/IP model provides manufacturers with increased access to plant-floor data, helping them make more accurate, informed decisions while optimizing internal assets and resources. Connecting devices to a common network infrastructure simplifies network security and access management. Having common programming and configuration tools for manufacturing and IT encourages greater collaboration to support common goals and objectives of their business.

Gregory Wilcox, Mike Hannah, and Mark Devonshire, are with Rockwell Automation. www.rockwellautomation.com

www.ab.com/networks/architectures.html

- Also read:

Rockwell Automation, Cisco release EtherNet/IP 'reference architecture' implementation guide;

Is Office Ethernet Hardware Tough Enough for Industrial Use?;

Switch to industrial Ethernet switches, rugged advantages;

Control Engineering industrial networks channel; and

Control Engineering System Integration channel.


- Edited by Mark T. Hoske, Control Engineering, CFE Media, www.controleng.com, www.cfemedia.com &amp



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