Definition: Layer-1 Switching

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Layer-1 switching is not a term you hear bandied about by the average networking professional. In fact, I’ve found that it has what I call the twitch effect. The listener, upon hearing the term, does a double-take when they realize they just heard something different from what they initially thought. Then there’s the inevitable chin scratching as they try to figure out if this is some horrible new marketecture or something of substance.

Not only is it substantive, but it is becoming more and more prevalent, with a number of enterprises beginning to take interest. Some have even deployed layer-1 switching in their data centers or lab and test/development environments.

Defining Layer-1 Switching

So it’s substantive, it’s on the move, and gosh darn it people like it. But what is it? Layer-1 switching (also called crosspoint, matrix, or crossbar switching) is roughly analogous to the old circuit-switched phone networks, where operators would manually patch calls end-to-end (for you younger readers, yes, this was really a thing). An electrical signal (layer-1, remember) comes in one side of a crossbar switch (the patch panel) and is electrically connected (patched) to another side of the switch. You can also think of it like a traditional patch panel in a data center, where the entirety of the cable plant terminates on the back side of the panel, and your Layer-2 team makes the connections on the front to a switching fabric.

Benefits of Layer-1 Switching

The main difference and benefit to a Layer-1 switch is that it can operate programmatically. That is to say, you can cable your data center one time, end-to-end, and use something like OpenFlow to programmatically change what is cabled to what. It’s not tagging, or doing something at higher levels. It really is changing the electrical systems path inside the switch in response to software instruction. In a frequently re-cabled environment like a lab, this offers incredible benefits and helps to explain why so many large enterprises are evaluating or installing this gear today.

Photo courtesy of Shutterstock.

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