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Dell: May the Force 10 (Gigabit Ethernet) be with your CAT6 cables

Embeds OpenFlow control freakage in two 10GE switches

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By acquiring Force 10 Networks back in July 2011, privatizing IT giant Dell moved itself from a maker of low-end switches to a contender for a slice of the top-end market for 10 and 40 Gigabit Ethernet switches that are ever so slowly becoming the backbone of data centers. But you have to keep up with the times, and that means providing a 10GBaseT port alternative to SFP+ ports and cables that are commonly required on 10GE gear, and it also means adding OpenFlow management to the switches.

To that end, Dell has just kicked out a new top-of-racker, the S4820T, a variant of the existing S4810 switch that swaps out the 48 10GE SFP+ ports for 48 10GBaseT ports that can use CAT6 cables instead of the more expensive SFP+ cables that you might not have in your data center. It sits next to the similar S4820 switch int eh Force 10 lineup, which also sports a combination of 10GE and 40GE ports.

Both the plain-vanilla S4820 and the CAT6-capable S4820T have ASICs that deliver 960 million packets per second of forwarding; the aggregate switching bandwidth on the S4820 and the S4820T is 1.28Tb/sec, just like many other switches in the 1U top-of-rack space. There are only a handful of different ASICs on the market, and this one looks like the Trident+ ASIC from Broadcom.

Both the S4820 and S4820T are stackable machines, and you can glue up to six together and manage them as a single domain. These two switches also come in variants that can blow air front-to-back or back-to-front, allowing you to mount the switches with different orientations in your racks and not mess up your hot and cold aisles in the data center. (It doesn't make much sense to suck in hot air across the switch, warm it further, and blow it into the cold aisle.)

The S4820 is different from the S4820T in one big way: those SFP+ ports allow for an 800 nanosecond port-to-port hop, while the 10BaseT ports take 3.3 microseconds. So as El Reg readers point out all the time, you have to look at your bandwidth and latency needs as well as port counts and types to pick your switches.

And you have to remember that the copper-based 10GBaseT cables don't have the same kind of range that the optical cables have. It is about 100 meters for CAT6, CAT6A, and CAT7 cables running in Gigabit or 10GE modes.

Both the existing S4820 and the new S4820T have four QSFP+ ports running at 40GE speeds that you can use as uplinks to the backbone or that you can cut down with cable splitters to add another sixteen 10GE ports to the switch, saving those 40GE ports as uplinks later.

The S4820T OpenFlow-capable 10GE switch, sporting 10GBaseT cabling

The S4820T OpenFlow-capable 10GE switch, sporting 10GBaseT cabling

You may save money by sticking with your CAT6 Ethernet cabling, but you are going to pay Dell for the premium to do so. The S4820 costs $31,165 or around $649 per port if you use those four 40GE ports as uplinks and don't split them down to 10GE ports. The S4820T, however, costs $35,372. And that works out to $737 per port if you divide it by the 48 10GBaseT ports and use those 40GE ports as uplinks.

The cost per port will come down quite a bit if you use cable splitters, but if you do, you end up with SFP+ ports off the 40GE ports, not 10GBaseT ports. And that defeats the purpose of keeping cheap copper cables. The issue here is that if you want to stick with CAT6 cabling (or CAT7 if you have it), then you will pay a 13.5 per cent premium for the switch, and in this case, that is $4,207 and that is also real money.

Sometimes you can't win, and you can't quit, either.

In other Dell networking news, the company has added support for the OpenFlow v1.0 protocol to its FTOS 9.1 and higher releases of its switch operating system in the Force10 S4810 and Z9000.

The S4810 was way out in front on the 10GE wave, launched by Force 10 back in November 2010 when it was still a separate company from Dell. The Z9000 distributed core switch debuted in April 2011 and is based on two Trident+ ASICs.

The combination of these two switches are what Force 10 was pitching as a leaf/spine network that could scale to 24,000 servers running at 10GE speeds or 160,000 servers at Gigabit Ethernet speeds. If there ever was a network that might need some OpenFlow traffic shaping, it is something like that.

No word on when other Dell Force 10 switches will get OpenFlow support. The S4820T mentioned above will eventually get it, as will its sibling, the plain-vanilla S4820. ®

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