For forty years Utah Scientific has been tackling the challenges presented to the broadcast industry, while improving quality, boosting efficiency, and lowering costs. With every new technology introduced, there is a great deal of “science” behind getting working product to market and then continually improving it. This is the first in our new series examining “The Science Of … ” looking at the “hows” and “whys” of what we do every day, so our customers are equipped to give their audiences the best experience possible. Enjoy.
“The Science of …” Series: Episode 1 “The Science of Routing”
The Inefficiency of Crosspoints, and How to Improve It and Save Money at the Same Time
By Tom Harmon, President and CEO of Utah Scientific
Traditional x/y video routers have been around for decades. This design has proven to be highly reliable. There is no blocking in x/y routers, and they are capable of many time-accurate, simultaneous switches. These systems are very robust, but highly inefficient in terms of harnessing total capacity. For instance, a 576 x 576 traditional configuration SDI video router requires a total of 331,776 crosspoints to ensure that any input can be switched to any output. This number is necessary to guarantee 100 percent availability of all sources and satisfy the nonblocking architectural nature of the product. However, only 576 of these crosspoints are utilized at any given time. Given these two numbers, it’s easy to see how much we must over-build to ensure that all specifications are met.
Over the years, a number of manufacturers have tried to use a technique referred to as tertiary or three-stage routing. This is a design that incorporates three different routing stages and is derived from the telco industry. Telco traditionally had the advantage of needing only slightly more than a 50 percent capacity to satisfy its switching needs. This is because in the early days of Telco switching, the industry could count on a one-to-one connection. If someone called an individual, only one switch was required to make the connection. If another party tried to call either of these individuals they would get a busy signal, ensuring that the call could not be interrupted. Note: this changed over the years, with the advent of three-way calling, conference calling, and products like Skype. But the point is that this type of design does not lend itself to the demands of a fully functional SDI router.
The quest to lower crosspoint count, increase efficiency, and meet all of today’s requirements continues. The use of multiple smaller routers to satisfy this requirement is also an approach that has been used to accomplish these needs. This design necessitates the use of tie lines, which are difficult to manage and introduce a blocking architecture to the system design. But what if we could utilize four 144 x 144 routers to build an array that accomplishes the same in/out capacity as a 576 x 576 x/y router? This would lower the crosspoint count from 331,776 to 82,944, making it a much more desirable solution in terms of cost and efficiency.
How can we accomplish this desired design? IT technology is the obvious answer. As Ethernet switches have increased capacity and bandwidth, it is now possible to utilize COTS products to transport full bandwidth 1080P (3G) signals as Ethernet-packetized streams. So, with these developments the combination of traditional x/y routers and high-speed Ethernet switches (the hybrid IP router approach) can be used to meet the above design requirements.
How this might be accomplished is for a future discussion.
(photo credit: By I, Daniel Schwen, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=3076712)