Understanding fiber-optic network technology for SCADA

Supervisory control and data acquisition (SCADA) networks have undergone significant changes, and the technological developments have made fiber-optic technology a viable solution for users looking to build a network.

02/25/2016


Example of substation data connectivity. Courtesy: Transition NetworksSupervisory control and data acquisition (SCADA) networks have undergone significant changes since the start of the decade as companies move to modernize their systems, improve security, and reduce networking costs. But as these networks need more bandwidth to support security, Internet of Things (IoT) sensor data, and other application data traffic, many organizations are considering moving to fiber-optic networks for their next-generation SCADA networks.

While several other contributors to this magazine have covered issues related to fiber-optic cables and optics (see, for example, "Fiber optics: A backbone for advanced building design" in sister publication Consulting-Specifying Engineer), there is still a need to know more about network technology choices for building out these new networks.

One of the biggest changes in SCADA networking has been the evolution from serial networking protocols to the Internet protocol (IP), the ubiquitous networking technology for the rest of enterprise networks. Adopting IP for SCADA networks means equipment costs can be less expensive, and bandwidth can scale up to 10 Gbps for end stations and up to 100G bps for backbone networks.

Moving to IP also has provided a means to better integrate SCADA-based operational transformation (OT) systems with an organization's information technology (IT) systems to set the stage for IoT, facilitate better and lower-cost tracking of network conditions, and provide access to better data analysis tools for operational data management.

Still, not every organization has moved to IP, and even some of those that have done so have not made a wholesale shift. Some are still cautious about the ability of a packet-oriented technology like Ethernet to replace deterministic serial networks that are based on time-division multiplexor (TDM) technology with guaranteed data delivery. Most SCADA applications have real-time data needs that require 99.999% network reliability and low end-to-end delay.

But only recently, with the introduction of ITU G.8032 (an International Telecom Union standard) has Ethernet had a standard for 50 ms failover that delivers levels of reliability that match serial protocols. Many industrial network managers are just now becoming comfortable with this technology. 

Video, IoT are increasing bandwidth requirements

Another network evolution is the need for SCADA backbone networks to support other data flows from equipment in the substation. Surveillance video data transport is an immediate need. There is a growing demand for better physical security at substations, which typically means increased video surveillance-leveraging the SCADA backbone network to backhaul the video data to a central location for monitoring.

In the not too distant future, these networks will require greater capacity to support sensors that monitor a wide range of industrial processes as part of the emerging IoT applications. Some pundits are predicting that networks could support thousands of sensors that will be monitoring processes and equipment and reporting back into a central console over the network.

Not only is IoT driving more bandwidth, it is also driving a consolidation of OT and IT systems to better process valuable production data and enable faster decision making based on this information. 

Moving to fiber optics

Even though all fiber-optic networks provide bandwidth, transmission distance, security, and electromagnetic interference (EMI) advantages, it is important to choose the right network technology as well.

Network technology decisions can provide added reliability, manageability, and redundancy. However, each network technology implementation will have its own cost considerations involving the total capital costs required to build the network in addition to ongoing operating expenses.

Networks can be built in a wide variety of topologies, but the two main topologies that should be considered for a fiber-optic SCADA network are:

  1. Ring: A ring topology is a network in which each network node (i.e. remote facility) is connected to its adjacent nodes in a logical ring fashion so that data travels around the ring until it reaches its destination. Ring networks are the easiest to build and to scale-a new node must simply connect to its peers in any part of the ring-as long as the distance that packets travel around the circumference of the ring is within the latency requirements of the network protocol. Cable redundancy must be built into a ring network to protect against node failures or cable breaks.
  2. Mesh: In a fully connected mesh network, each node is directly connected to every other node, and data can be routed to any node on the network with very low delay. Mesh networks are complex and costly to scale though, because each new node added to the network requires a quadratic increase in connections for every node in the network.

There are three main network technologies to consider in building a fiber-optic SCADA network.

Learn more about the three technologies for building a fiber-optic SCADA network.


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