Trends in Ethernet Switch Development
Here’s something you probably didn’t know. There is only a small number (maybe four) major suppliers of Ethernet switch fabrics in the world.
And: they’ve
all been going in similar directions recently, following the same sort
of trends as we’re seeing in general CPU silicon. The most notable of
those trends are finer lithography and more integration, and both of
these have made it easier to produce better products for the military.
In particular, these changes have stretched things at both the bottom
end (low speed) and the top end (higher speed) of the product range.ethernet switch design
First, though, some background. The Ethernet switch relies on a piece of silicon referred to as a ‘switch fabric’. The fabric is connected to a set of Ethernet ports. The fabric is the device which decides where to forward each packet, so that it comes in on one port and gets forwarded out on another port (or several other ports.)
Within the military, switches are becoming more and more common, as an increasing number of devices (such as sensors) are now using Ethernet instead of specialist buses, like 1588. The military also has requirements that are not typical of the commercial Ethernet switch market, and some of the trends in Ethernet switch fabric technology have implications for use of the technology within the military.
Improved performance, less power
But to return to those trends… Finer lithography has meant improved performance and a reduced power draw for all levels of switch speed. The most obvious place for this is at the top end, where we’re now able to produce switches capable of large numbers of ports capable of 40 Gigabit per second (Gbps) traffic. The Abaco SWE540, for example, is a fully managed switch with 20 x 40Gbps ports (and 16 x 1Gbps ports) in a single 6U VPX card. This sort of switching capability was impossible to squeeze into a single card a few years ago. And: we’re now looking at putting this sort of capability in a 3U card before later this year.
More integration has brought a related, but different, advantage. Fabric suppliers are now using system on a chip (SoC) techniques to integrate CPUs into the switch fabric chipsets. This means that we can design a managed switch without using a separate CPU. This in turn means we use less board space (and less power) and so can fit more capability into a smaller space. Our favorite example of this is the RES3000 family of switches. These are very rugged switches within a really small enclosure, but still with all the management features required to provide a secure, robust and efficient network. This has been made possible because we have a highly integrated fabric and CPU chipset at the heart of it.
Of course, not all these trends play perfectly for the military. One of the areas where some compromise was made in integrating the CPU was with the processor clock speed – the CPUs that are integrated tend to be something like a little ARM, running at a few hundred Hertz. For most switch management roles, this is not important, as the software isn’t involved in most of the high-speed forwarding of packets. However, the clock speed tends to impact the start-up time. For the military, switch start-up time can be really important: imagine, for instance, if the switch is at the heart of all external vision for a combat vehicle. You are effectively ‘blind’ until the switch is up and running. Therefore, the difference between 30 seconds and two minutes is pretty vital.
