Wandering Thoughts archives


The physical versus the virtual approach to network wiring

I was recently reading Matt Simmons' The Cyclical Nature of Academia, where he talks a bit about the network wiring that they do. This sparked a thought about the two different ways to do network wiring (or at least the two main ways).

If you have a collection of VLANs and a collection of ports and a set of mappings between these two that stubbornly keeps changing, you can set up your wiring closet in what I'll call physically or virtually. The physical approach is simpler to describe; you have a collection of single-network switches and as a wall jack changes VLAN membership you physically rewire it from switch to switch by moving its patch cable. In the virtual approach you have a great big switch stack that carries all VLANs, wire each wall jack to a fixed port on the switch stack, and to 'rewire' a wall jack you change the switch's VLAN configuration for that port; the physical patch cable never moves.

From the brief description in Simmons' entry it sounds like his organization has gone for the virtual wiring approach. For a collection of reasons we have gone for the physical one (as I implied in an earlier entry on how our network is implemented).

My feeling is that you inevitably wind up with a network snarl in both cases once enough time has gone by. The difference between the two is where that network snarl is. In the physical case the snarl is physical, created as you run and re-run patch cables between your patch panels and your edge switches. In the virtual case the snarl is in software, in the switch configuration where a mishmash of VLANs goes to a mishmash of ports (you have no physical snarl; since your patch cables never move you can set them up neatly and have them stay that way).

I don't think that there is a universal right answer for whether you should do physical or virtual wiring. In our specific situation physical wiring is clearly the right choice for a complex collection of reasons, even if it creates visible cable messes.

(Trying to explain those reasons is for another entry.)

sysadmin/PhysicalOrVirtualWiring written at 00:15:12; Add Comment

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