TAP – The Best for Real-time Network Monitoring

TAP – The Best for Real-time Network Monitoring

Posted on by FS.COM

It is known that networks, especially SAN, are the mesh that interconnects all servers, switches, etc. And it carries critical business information and data in constant heavy traffic. With increasing change and growth, the networks are prone to infrastructure failures, which makes real-time monitoring vital for business success. Then the network manager may choose to insert a TAP in the connection link. So What is TAP? This post will give the answer.

TAP Basics

TAP (traffic access point) provides accurate real-time access to traffic flowing on a physical connection/link between two or more points within a network. It offers the exact duplicate of the signal on the network link without any disruption to the network activity, for most accurate real-time and proactive monitoring and analysis. Normally, a TAP resides in the link between network devices.


Types of TAP

Two types of optical TAPs are available—active optical TAP and passive optical TAP. The active TAP uses electricity for operation while the passive TAP does not. The active TAP is mainly used for applications that require manipulation of the signal sent to the monitoring port. This is required only for very specialized applications. Passive TAP is much more common in enterprise data centers and used for applications that require simple monitoring. More detailedly, passive TAP provides a simple and powerful way to monitor optical networks. And because of requiring no power and having no electrical components, it is impossible for passive TAP to be a point of failure when deployed in a production network. And passive TAP is highly reliable and requires no maintenance. In all, passive TAP provides access to data flowing across a network, without creating either a location to corrupt data or a prospective point of failure.

Passive TAP

Split Ratio of TAP

From the picture, we can see that the split ratio of the TAP is 70/30, but what actually the TAP split ratio means? A split ratio is the amount of light that is redirected from the network to the monitor ports on a passive fiber optic network TAP. Or the percentage of the light left in the pass-through link versus the percentage tapped off for the monitoring link is known as the split ratio. Generally, the TAP split ratio is available in 50/50 or 70/30. A 50/50 split ratio would indicate that 50% of the light budget coming into the TAP from the network is passed along to the end device, and 50% of the light budget is diverted to the monitoring device. Whereas in a 70/30 split ratio, 70% of the light budget is passed along to the end device and only 30% of the light budget is passed along to the network monitoring device.

If the path to your monitoring device is short and direct, you might need to maintain more light on your primary link to keep both signals readable. At the edge of readability, you will experience network performance degradation due to retries and errors even if the link does not fail completely. If the TAP does not split off enough light, the monitor link will fail to deliver enough light for the monitoring appliance to register an accurate signal. Low light levels on the monitor link can lead to false conclusions of data errors on the network link, or there may not be enough light for the appliance to register any signal at all.


Allowing access to network traffic in real-time for troubleshooting, analysis, and monitoring without affecting network operation, TAP is a simple, effective, and cost-efficient way to gain access to data within switched networks. Install TAPs during deployment of a SAN to allow future troubleshooting without bringing down the network or breaking links. FS.COM provides a series of TAPs for both 40G and 100G applications. Visit www.fs.com for more details.

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