Last time, we mentioned that there is a lower-speed version of metro Ethernet, commonly called "mid-band" Ethernet, which is starting to be rolled out. The keys to mid-band is that it provides access at rates between T-1 (1.5Mbps) and a full 10Mbps, and that it can be deployed over copper.

As it turns out, our longtime friend and associate, Robbie Forkish, is at the forefront of the mid-band movement. Forkish is currently vice president of software engineering at Hatteras Networks. Those of you who have been around for a while will also remember Forkish from the T-1 multiplexer days as one of the founders of Network Equipment Technologies.

We asked Forkish to provide an update on mid-band, and he graciously shared the following:

"Want metro Ethernet but don't have fiber connectivity? Heard horror stories about the cost and hassle of bringing fiber to your facility? A new service - called mid-band Ethernet - has emerged that extends the reach of metro Ethernet services beyond the fiber footprint. By bonding multiple POTS-grade copper pairs into a single Ethernet link, speeds of up to 45Mbps can be achieved.

"As a result, metro Ethernet can now reach beyond the HQ and regional sites of the Fortune 500 to the now-fortunate 500,000 business sites. This means that the low cost and simplicity of Ethernet is coming to small and midsize businesses as well as remote and branch sites of large enterprises.

"Mid-band Ethernet provides the same services as metro Ethernet, but at lower speeds - typically 2Mbps to 10Mbps, although the technology supports rates up to 45Mbps. By bonding multiple copper pairs into a single Ethernet channel, rates can be achieved beyond what is possible over a single copper pair. The Ethernet over bonded copper interface, called 2BASE-TL, was standardized in IEEE 802.3ah in June 2004. The standard specifies the physical layer, bonding and fragmentation procedures, as well as a link-level OAM channel for enhanced management and diagnostic capabilities - essential for offering business-class services.

"In addition to higher data rates, mid-band Ethernet over bonded copper provides higher resiliency - the failure of one pair does not take the connection out of service.

"Enterprise sites fortunate enough to have fiber connectivity have responded enthusiastically to metro Ethernet services because they could get more bandwidth for less money, with flexibility that allows selection of burstable bandwidth without being limited to facility rates such as 1.5Mbps and 45Mbps. But the fiber footprint covers less than 15% of business sites. Now mid-band Ethernet brings those same services to the rest of us!"

Steve Taylor is president of Distributed Networking Associates and publisher/editor-in-chief of Webtorials. Jim Metzler is vice president of Ashton, Metzler & Associates.