If you're not already making plans for 10Gig Ethernet, perhaps New Year is the right time to start doing so, according to exhibitors at last month's Enterprise Networks show in London. They predict that the cost of 10Gig should fall considerably once the 10GBase-T spec for 10Gig over copper is finalised some time in the middle of 2006.
Of course, 10Gig is already available over copper in the shape of 10GBase-CX4, alias IEEE 802.3ak, but this only runs up to 15m, whereas 10GBase-T (802.3an) will go 55m over unscreened CAT6c (UTP) cable, and up to 100m over screened (STP) cable.
"We didn't buy into CX4 because we saw it as an interim standard," commented a sales engineer from Force10 Networks, which has instead focused on 10Gig over fibre, using swappable XFP modules to support the various different fibre types. (Standardised as 802.3ae, 10Gig Ethernet can run up to 40km over fibre.)
He said that companies such as Force10 are instead waiting for the T spec, and that this is what will trigger 10Gig's explosion onto the mass market later this year.
"10Gig on copper will be fixed on the box, not swappable by changing XFPs as for fibre," he added. "Fixed ports will be part of what brings the cost down."
Regina Good-Engelhardt, a product manager with Swiss cabling developer RDM, quoted projections from market researcher Dell'Oro which suggest that the average cost of a single 10Gig port will finally fall below the cost of ten 1Gig ports during the first half of 2006, and that 10G will be double the cost of 1Gig by 2008.
"The big advantage of T will be for horizontal distribution in-building, and in server rooms," she said. "The problem for higher data speeds is that signal attentuation worsens as the frequency rises."
10Gig networks will use DSPs [digital signal processors] to win back some capacity, plus a new data coding method that has 16 states (bit values) instead of three or five used in previous generations.
The snag is that there is only 6mv between each of these 16 states, so noise is a big problem, and while the transmission system can compensate for internal noise, it can't cope with external noise such as alien crosstalk - crosstalk from other cable pairs.
Possible techniques to mitigate the effects of alien crosstalk include unbundling cables, using screened patch cords, using only every other port on the patch panel or using screened connecting hardware.
Shielded twisted-pair (STP) cables provide much more protection against crosstalk, but RDM's Good-Engelhardt said that many buyers are prejudiced against STP. They prefer unshielded (UTP), as past generations of STP were more expensive and bulky than UTP.
However, she argued that neither is true of current STP cabling. Indeed, she said that the unshielded pair separation needed to reduce 10Gig crosstalk means that manufacturers have to build in plastic separators, which can make UTP both bulkier and harder to handle than STP. "10Gig screened is currently cheaper," she added.
Still, that market desire for 10Gig UTP is pushing manufacturers such as R&M to come up with new cable designs.
"We are in an uncertain area between CAT5e unshielded and CAT7 shielded - we want to offer both," Good-Engelhardt said.
"We recommend CAT6 STP, but most of the world uses UTP. People are trying new materials to compensate, the distance between the connectors is critical too." Adding a shielded housing to the UTP connector can help too, she noted.
"You can change the size and shape of the cable too, that can cause pulling problems though. All the manufacturers use tighter pair twisting, and we add discontinuous foil wraps every 30cm - because they're discontinuous there is no antenna effect or path for earth signals.
Of course, to some extent all of this is academic. You can install the cabling for 10Gig today, but you won't be able to run 10Gig over it because there are no active components yet for 10GBase-T.
Still, they are definitely on the way - and they will probably be here sooner rather than later.
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