Keeping a router cool is hot

Bob Pank#

Author: Bob Pank#

Published 1st September 2012


To mangle a metaphor: The more things stay the same, the more they need to change.
A significant percentage of the global installed base of broadcast routers has stayed, more or less, the same – many for more than a decade.
We think that needs to change, not entirely because of ultra new technology, but because many of the fundamental elements common to all routers are struggling to meet the contemporary demands placed on them.
The ever-increasing mandate to deliver multiple video formats and, just as important, complicated multichannel audio, are pushing these old warhorses to the edge of their performance limits.
Notwithstanding the emerging new features and functionality that customers should be looking for as they replace ageing routers, there are fundamental issues that are as relevant today as they were when routers were young.
Those issues are space, power and temperature control. They’re interrelated, but let’s take them in turn.
It’s true that routers have gradually reduced in size over the years. Initially, they sequestered a lot of valuable real estate. Many still do. A lot of that had to do with, for example, connectivity requirements.
Routers historically used BNC connectors, which were fine for a number of years. What sustained BNCs as the accepted standard for so long was that the integrated circuit (ICs) boards that fed those connectors were, when compared to today’s standards, quite large, and required BNCs to make the connection to external devices.
Circuit board technology nevertheless succumbed to Moore’s Law of capabilities and became smaller and smaller, which enabled Miranda and other router manufacturers to deploy a new type of connector, the DIN 1.0./2.3. (We’d be remiss if we didn’t mention that Miranda was first. Just sayin’.)
Miranda standardised on the DIN 1.0/2.3, which is primarily what has enabled routers in general to become much smaller. A decade ago, a router with a 128 square matrix could take up twice the amount of space that the same configuration does today, and that’s a good thing.
What’s not as good is that the condensed size doesn’t diminish the power requirements. It does, however, change a router’s design requirements in terms of how power is distributed to the cards enclosed within it. Some use a high amp/low voltage, single connection to a router frame. That’s fine if your router operates in a perfect environment, but the facility is wholly dependant on that one single point of failure connection. If anything happens to that connection, it will take the whole router down, even if redundant power supplies are in place.
We’ve found ways to distribute power more effectively and efficiently. We’re not prepared to divulge the details, but let’s just say that a design that includes a half-million hour MTBF specification vastly reduces the likelihood of a router taking a facility down completely.
So long as we’re talking about power, let’s take a moment to talk about its first cousin, heat.
We’ve talked about routers shrinking size, which in many instances, particularly for OB applications, provides the opportunity to achieve higher density. But add power to density in a compressed environment and you significantly raise the temperature in the room. Cooling, therefore, becomes a major issue.
Cooling may sound like a trivial matter in routing design, but it’s not. For manufacturers, it’s the number one design parameter that can maximise the life and reliability of a router, and it’s not easy. More than one crosspoint has been toasted as a result of an ill-conceived temperature control design.
Many manufacturers have wrestled with the cooling problem and some have - in their minds – resolved it by loading a router with fans. We don’t believe that’s enough. Small industrial fans are prone to failure. Some have even mounted fans directly over crosspoint modules, which are typically hotter than any other component. If that crosspoint fan fails, you can’t service it without pulling the crosspoint, which of course kills that crosspoint’s output.
We’ve thought about this a lot and have taken a different approach in the form of a single-sled, plug-in blower assembly. The assembly draws air through the front of the router frame, keeps the entire unit cool to specified parameters and exits straight out the back.Importantly, we’ve also made it extremely serviceable. Just slide the assembly out from the front and swap it out. No crosspoints are harmed in the process.
There is simply too much that could be covered when talking about router design, but this back-to-basics overview does cover the core considerations. We haven’t even touched on the advent of fibre connectivity, which makes things even hotter inside a router. Perhaps we’ll give that a thorough discussion in a subsequent issue.
For now, “Keep cool and carry on” – if you can.

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