By: Datacom Systems Inc.

Choosing a Physical Layer Matrix Switch

The first step to selecting the right matrix switch for your network is to make sure you match the topology of the switch with the topology of your network.

Matrix switch technology is available for most major topologies - currently, 10/100 Ethernet, 10/100/1000, Gigabit Ethernet, Token Ring, DS3, E3, T1, and E1.

In-Line or SPAN Matrix Switch?

Choosing an In-Line or SPAN matrix switch depends on how you are currently doing your network analysis and monitoring and ultimately what data you need to see.

Connecting a network device to a network switch's SPAN port is an excellent way to get an overall view of your network. However, pinpointing the source of actual network problems may require an In-Line solution.

In-Line analysis of your network is possible by creating a direct access port in between two network devices, using network taps or In-Line matrix switches. In-Line access allows you to receive all full-duplex network traffic, including all the errors. In contrast, a monitoring device connected to a SPAN port does not see all traffic. Network switches eliminate Layer 1 and some Layer 2 errors, making it impossible to troubleshoot physical layer problems, bad frames, and corrupt packets.

If you already have network taps deployed in your network, and you'd like to perform roving analysis on mutiple tapped links, an In-Line matrix switch provides an excellent solution to allow you to leverage your existing infrastructure and save money.

There are also several other some other considerations you must make when choosing whether to use a SPAN matrix switch or an In-Line matrix switch. The following table provides more information:

In-Line Fiber Matrix Switches

If deploying an In-Line fiber switch, there are also two other items consider - the switch's split ratio and the switch's light source.

A fiber switch's split ratio is mainly determined by the switch's receiver sensitivity, its' transmitter strength, and cabling.

Each time an optical link is switchped, the link suffers from insertion loss. With each new access port that is created on a fiber link, more light gets "switchped out" of the network. This degrades the nework signal. In other words, the more "light" a fiber network has the better. Therefore, when deploying a fiber switch, you should choose a switch with the highest split ratio that will provide the adequate amount of light to the connected monitoring device.

The fiber splitters in the switch also need to support the light source used on the network. For instance a 1000Base-LX monitoring device will transmit data using 1300-nm lasers over single-mode fiber. If splitters are used that support lower-intensity LED transmission on this link, laser light intensity could cause network performance to degrade, so you'll want to ensure you select an LX switch with compatible fiber splitters. This ensures the insertion loss that is dictated by the chosen split ratio will be accurate.

PERMAlink™ - In-Line Matrix Switches with Built-in Passive Taps

Unlike In-Line fiber switches or network taps, copper technology does not split the network signal; it regenerates it. Regenerating the network signal means the signal gets amplified to a level where it can be received by the network devices connected to the switch. To regenerate the network signal, copper devices must normally have power.

Datacom Systems invented patented technology called PERMAlink™ to address this very issue and provide total fault tolerance for both copper and fiber In-Line matrix switch solutions.

In a PERMAlink™ protected matrix switch, the passive, non-intrusive taps are permanently affixed to the rear of the switch chassis and connect to the active portion of the switch by means of internalized connectors. If power is lost to the switch, network traffic continues to flow uninterrupted.

Additionally, if the switch ever requires service or upgrade, the user simply removes a slide-out tray containing the active components (after disconnecting the power and control cables). No service window is required and the network links are never interrupted after initial installation.

With PERMAlink™ every network manager can rest assured that using an In-Line matrix switch solution will never affect network integrity.