Compromise on High-Speed Ethernet

Arthur Cole

If only all disputes could be settled this easily. The IEEE Higher Speed Study Group (HSSG), in a quandary as to whether to pursue a 40 Gbps Ethernet standard or jump straight to 100 Gbps, decided to opt for both.

 

While the move breaks the precedent of boosting each Ethernet standard by a factor of 10, the 40 Gbps rate had the vigorous backing of data center interests looking for a suitable switch-to-server connection, as opposed to a full networking and aggregation backbone.

 

The 802.3ba standard will not be ready until 2010, but it will be the first to offer versions for both multimode fiber optic (more than 100 meters) and copper cable (up to 10 meters). For single-mode fiber, the group has set target distances of 10 and 40 km, although not with multiple wavelength capability as found on most high-speed WANs today. A future spec for a one-meter backplane physical layer is also in the offing.

 

According to this piece in EE Times, one of the bones of contention between the 40 and 100 groups was the fear that the 40 Gbps layer would be too restrictive for use in optical fiber, and that it would fall to individual vendors to ensure their 40Gb wares were compatible with existing optical networks. In the end, the two sides agreed to work through the Ethernet Alliance to ensure the public understands the different functions of the two data rates.

 

Of course, we're not completely out of the woods just yet. There's still the matter of encoding, with enterprise folks using 64b/66b, while carriers prefer the 512b/513b format.


 

Still, the fact that the group came together on a single high-speed Ethernet is nothing less than a miracle to some. At one point, there were groups arguing for everything from 40 to 120 G, and the final compromise came only after it was clear that the 40 and 100 groups were not about to budge.

 

Compromise, of course, is always preferable to open warfare. But let's hope that this one represents true consensus and not a technical fudge that leaves no one happy in the end.



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