This article was originally published in October of 2008 at 10GbE.net.
Last week Cisco jumped behind something called Twinax, Why? Three likely reasons:- Flexibility – Cisco and Juniper both selected SFP+ as the PHY for their new line of 10GbE switches. Offering an SFP+ cable with a connector on the end that enables you to use a single SFP+ port for all your connection needs is a stroke of genius. Say you need a short run from one switch to a server, plug a Twinax cable with SFP+ connectors on each end in and you’re good to go, up to 10 meters. Suppose later you need to move that server another 50 meters away then pop in SR optics on both ends and use fiber. No changes to the servers or switches, just swap in optics.
- Cost – there has been a run up recently in the price for copper, while the cost of Twinax coax cable remains fairly fixed.
- Power – SFP+ is rated at 1W/port, the Twinax solution typically draws 1/4W. CX4 is similar but compared to 10GBase-T at 10W (current generation) or even 2W for the next generation (under 30M) this is a huge power saving.
- Latency over 10GBase-T – Current 10GBase-T uses a DSP at each end to separate the signal from the noise. This DSP adds roughly two micro seconds on each end of the connection, compared to under 200ns for the Twinax conversion.
We are closely watching how Twinax plays out over the next few months, and we’ll let you know what we learn.
UPDATE JANUARY 2012 – Twinax, otherwise known as Direct Attach or DA has won. In the past year, we’ve seen a significant drop off in requests for CX4 NICs since their height in 2008.
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