First-Mile Ethernet Enters Home Stretch
Equipment tailored for Ethernet in the First Mile (EFM) could be ready to roll this summer, as the specification is approaching a critical milestone within the Institute of Electrical and Electronics Engineers Inc. (IEEE).
Participants in the IEEE 802.3ah task force say their draft standard is almost ready for a working-group vote in July. At that point, the standard would be solid enough to build products on, even though formal ratification would be at least six months away.
EFM is part of the near-religious effort to simplify networks by extending the reach of Ethernet beyond the LAN. One particular target of the standard seems to be digital subscriber lines (DSLs) that are currently carried on Asynchronous Transfer Mode (ATM).
"Getting rid of all those protocol conversions and transitions is what we're really after here," says Craig Easley, president of the Ethernet in the First Mile Alliance (EFMA) marketing cooperative and a technology director at Extreme Networks Inc. (Nasdaq: EXTR).
(By the way, "first mile" means the same as "last mile." EFM proponents decided to change the vernacular to "first mile" to show they were putting the customer "first." Seriously.)
One complication is that 802.3ah has grown. Various special-interest groups have wedged their way into the standard, creating subgroups that don't necessarily have anything to do with each other but could benefit from EFM standardization. Here's a rundown of what's inside the 802.3ah spec:
- Short reach: 750 meters at up to 10 Mbit/s
- Long reach: 2,700 meters, but at only 2 Mbit/s. This part was added later to accommodate more outside-plant deployments.
- Original goal: 1-Gbit/s speeds on single- or dual-strand fiber. In the dual-strand case, one strand is used for upstream traffic and the other for downstream. For single-strand installations, both directions share the strand and are kept separate by frequency-division multiplexing.
- Added: Provisions for 100 Mbit/s as well, to open the possibility for much cheaper switches, Easley says.
- A fancy term for Ethernet passive optical networks (EPONs). This wasn't part of the original charter but was added by PON vendors who crashed the 802.3ah meetings. Their proposal caused a stir at first, because it uses time-division multiplexing to combine users' upstream traffic. "That whole TDM upstream is seen by IEEE purists as Not Ethernet. There was a lot of fighting early on to throw these guys out," Easley says.
- OAM would provide the ability to do remote bit-error-rate testing and other remote management. "Ethernet right now is a link-layer technology. It has no intrinsic management. When carriers talk about deploying Ethernet, the thing holding them back is management," says Matt Squire, a Hatteras Networks representative who is chairing the OAM effort.
The standard has reached a point where it's closed to major additions, so there won't be any extra copper or fiber variants added between now and IEEE ratification.
The fiber and EPON work has gone smoothly, but two skirmishes erupted on the copper side. First, vendors bickered over which flavor of DSL should be used to transport Ethernet across long distances (see 'First Mile' Ethernet Hits Snags). The G.SHDSL standard eventually won that fight.
For short distances, the copper group settled on VDSL for transport. But that led to the second battle, involving which line-coding scheme to use. Other standards bodies are mulling the same question, and they might all follow the lead of the T1E1 group, which is expected to decide next month (see High Noon Arrives in VDSL Battle).
The next 802.3ah meeting will take place in July during the IEEE plenary meeting in San Francisco. Assuming the working group gets the VDSL issue settled at that meeting, they'll be ready to submit the current draft for a working-group vote, putting 802.3ah on a pace for full ratification six months later.
As usual, products will appear long before then, because the draft spec is close enough to the real thing. Excepting that line-code issue, any further revisions should be minor enough to be covered in firmware.
"People are starting to build along the lines of the standard," Hatteras's Squire says. "In our case, we know we'll be able to upgrade our products in firmware."
Those products won't receive the urgent response they would have gotten 18 months ago, however. First-mile Ethernet is a big deal in Korea and Japan right now, but in North America, Ethernet-based carriers such as Telseon Inc. and Yipes Enterprise Services Inc. have seen their fortunes sag.
Easley says North American ILECs (incumbent local exchange carriers) are fans of the Ethernet concept, particularly for its ease of provisioning. But the weakened CLEC (competitive LEC) competition has stifled the ILECs' urge to research things like Ethernet. "They don't have to be as risky," he says.
— Craig Matsumoto, Senior Editor, Light Reading