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3 Benefits of a TAP Fabric in OT Networks

June 11, 2025

3 benefits of network tap in ot networks

Every week, I hear from industrial companies about their cybersecurity tools needing access to the data flowing through their OT networks.

In a previous post, I shared why companies are constantly looking to improve their OT network visibility. That article is a great foundation for this one. Here, we’ll dig into the benefits that come from using a TAP fabric, which is some combination of Network TAPs and Packet Brokers, in your OT environment.

Companies favor
TAPs over SPAN ports for OT traffic access because of these 3 primary benefits: 

  1. Guaranteed unidirectional traffic
  2. No impact on the production environment
  3. A recognized cost savings

Guarantee Unidirectional Traffic

Unidirectional, or one-way data flows, are often required in OT networks. These safeguard the network from external threats while also providing the out-of-band data necessary to monitor the network for cybersecurity purposes.

Many of Garland’s Network TAPs have built-in Data Diode functionality. This sends unidirectional copies of the traffic to out-of-band tools for monitoring purposes, without any effect on the link between the two network elements.

Since there is no physical connection between a Data Diode TAP’s monitoring and network ports, there’s no possibility of intrusion from the destination. These TAPs physically do not send traffic back onto the network, providing “no injection” TAP visibility for 10/100/1000M networks.

 

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No Impact on Production

For industrial companies, it’s critically important to keep the manufacturing lines running, power plants generating power, water treatment facilities providing clean drinking water, etc. Anything that would impact production has serious consequences.

One benefit of using a TAP fabric is the lack of impact on production, which otherwise could be the biggest potential business disruptor. Since Network TAPs are typically passive and deployed out-of-band, they don’t have to be certified by whoever runs the plant, approved by whoever makes the control system decisions or endorsed by whoever certifies the changes to new hardware put in place. Customers are simply putting in a TAP, which is passive and out-of-band. It doesn’t have any impact on the live production network!

A TAP also improves an organization’s resiliency. Should a TAP go down for some reason, or if any of the devices connected to the TAP were to lose power, there wouldn’t be any impact on the organization's operations. But if a switch goes down, that does potentially impact operations.


Cost Savings

Many industrial environments are physically large, often geographically dispersed, and outdated in terms of IT infrastructure. If a company is looking to deploy cybersecurity tools to prevent threats, ransomware attacks, and breaches, there is often a struggle to gain access to the network traffic.

Legacy switching fabrics often lack the ability to configure SPAN ports, or they are running at capacity and there are no available ports to configure. Rather than upgrading the entire switching fabric and enduring the business cost of interrupting operations, organizations are finding another way.

Companies are adding a TAP fabric with passive network TAPs (sometimes also paired with smaller packet brokers) at each location. It is a much more cost-effective solution. A TAP fabric allows you to deploy cybersecurity tools today, while also providing permanent access for more tools in the future.


Want to learn more?

Watch our latest roundtable webinar with Dragos where we discuss tactics and strategies for strengthening your ICS/OT visibility.

 

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Heartbeats Packets Inside the Bypass TAP

If the inline security tool goes off-line, the TAP will bypass the tool and automatically keep the link flowing. The Bypass TAP does this by sending heartbeat packets to the inline security tool. As long as the inline security tool is on-line, the heartbeat packets will be returned to the TAP, and the link traffic will continue to flow through the inline security tool.

If the heartbeat packets are not returned to the TAP (indicating that the inline security tool has gone off-line), the TAP will automatically 'bypass' the inline security tool and keep the link traffic flowing. The TAP also removes the heartbeat packets before sending the network traffic back onto the critical link.

While the TAP is in bypass mode, it continues to send heartbeat packets out to the inline security tool so that once the tool is back on-line, it will begin returning the heartbeat packets back to the TAP indicating that the tool is ready to go back to work. The TAP will then direct the network traffic back through the inline security tool along with the heartbeat packets placing the tool back inline.

Some of you may have noticed a flaw in the logic behind this solution!  You say, “What if the TAP should fail because it is also in-line? Then the link will also fail!” The TAP would now be considered a point of failure. That is a good catch – but in our blog on Bypass vs. Failsafe, I explained that if a TAP were to fail or lose power, it must provide failsafe protection to the link it is attached to. So our network TAP will go into Failsafe mode keeping the link flowing.

Glossary

  1. Single point of failure: a risk to an IT network if one part of the system brings down a larger part of the entire system.

  2. Heartbeat packet: a soft detection technology that monitors the health of inline appliances. Read the heartbeat packet blog here.

  3. Critical link: the connection between two or more network devices or appliances that if the connection fails then the network is disrupted.

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