Greg says, "This leaves the problems of mechanical and electrical performance over time. The basic problem I have is that Cat6A is close to the limit of what can be achieved with copper in terms of electrical performance. It was originally believed that 10GBaseT wouldn’t even be possible."
Now, Greg has a point that eventually we just won’t be able to squeeze higher and higher data rates through a twisted pair cable and 8 by 8 modular jacks. I myself once predicted that we’d never see Gigabit Ethernet. Since collision detection requires that the first bits of a packet reach the most distant node before the last bits are transmitted, a gigabit network could only be a few meters end to end. I was of course proven wrong as we adopted switching, and collision detection became a historical artifact.
However, I remember hearing almost exactly that same "twisted pair isn’t up to carrying our really cool new fast tech" line when Synoptics introduced LattisNet Ethernet over twisted pair. People were so concerned that two twisted pairs couldn’t securely carry 100Mbps Ethernet that a four-pair standard 100Base-T4 was ratified just in case. The pattern during the past several Ethernet speed upgrades has been for fiber to come first and for truly widespread acceptance to occur when twisted pair made it cost-effective.
Greg worries that twisted pair cable is delicate, that the cable is weak where it enters a modular plug (more frequently referred to as RJ-45), that over-insertion of cables during cable assembly can cause problems, and that a kinked cable can cause data reflections. Having spent 20 years in data centers where twisted pair was the norm, I’ve always had the impression it was fiber, not twisted pair, that was fragile and hard to terminate. Maybe Greg thinks it’s better that the fiber in an optical cable snaps when slammed in a cabinet door so the problem is permanent not intermittent. I’ll just dress my cables so they can’t slam in the door.
Finally, Greg quotes a no-longer-available blog post that implied that 10Gbase-T has lower bit error rate specs than optical or DAC connections. I spent some time researching this and found not only that all 10 Gigabit Ethernet PHYs (physical layer implementations), and Fibre Channel have the same worst case BER of 1 in 10^12. My research shows real world BERs of more like one in 10^15 in the field. While some Fibre Channel folks have lobbied for higher standards, they’ve never made it into the spec.
When 10 Gigabit Ethernet becomes standard on servers, it will almost certainly be 10Gbase-T because 10GBase-T ports can auto-negotiate down to 1GBase-T. Server vendors can sell 10GBase-T servers into data centers that haven’t yet upgraded their network gear but would have a smaller market for SFP+ on the motherboard. Now, if there were 10Gbase-T SFP+ modules like there are for 1GBase-T ... But that would just get us into SFP+ checking again.
Disclaimer: I really do believe in fat guys with beards that give my kids presents.
