Tuesday, December 4, 2007

VoIP, QoS and PLCs...hugh?

So I'm sitting here at my desk. In my home. Gazing at the traffic going by out my 26th story window. My lightning fast Internet connection no longer seems impressive. The building sits on a true 100 megabit pipe, but the novelty's quickly worn. Don't get me wrong, I'd be devastated without it. But when it's here, what do I do? Check email, type, read web sites, and post to forms - and blogs.

But my VoIP phone, complements a la Vonage, provides an invaluable service that I continue to appreciate. The technology is simple - send that voice stream over our worldwide routed network just like we would have with the monopolized circuit switched network. The fiber under the ocean has much greater capacity than satellite voice channels. Back to reality - answering a US cell phone call on a normal physical phone at home in Korea, then talking about nothing for an hour and not worrying about billing! Sweet! The only reality check comes in when you forget that you're 17 hours ahead. I made one accidental call to a friend on a weekend at 2:00AM. Luckily she was out somewhere (scratches head...).

Along with VoIP comes the importance of QoS. I still haven't purchased a home ("gaming") QoS router. My coworker claims it worked wonders for his VoIP and gaming rig - particularly when downloading large files. He brings a good point - VoIP creates "chatty" low bandwidth, high frequency, traffic where latency really matters. Quality of Service prioritizes the delivery of such packets. With QoS, your VoIP will seem uninterrupted, while your high bandwidth download will still transfer quickly. This same concept applies to HMI/SCADA traffic to PLCs. They require rapid polling of little bits of data so that the system feels responsive on a change. The last thing you want is Bob From Accounting to download his end of the month spreadsheet and slow down your control system. PC/PLC traffic can be thought of like typical time intensive UDP streams. Tell your IT department to prioritize the traffic like they would a VoIP phone or important webcam.


Lrac said...

Hey cool, I always wondered what QoS was. This might deserve a more lengthy post if you're up for it. How can various traffic packets be differentiated from each other?

surferb said...

Lrac - thanks for the suggestion. I'll post another entry about QoS in more detail.