Fast Net News, DSL Prime, DOCSIS Report

The Senate stimulus bill requires "100 megabit downstream" for the highest subsidy, which the telcos in D.C. believe eliminates DOCSIS 3.0 from the money. Verizon, according to the N.Y. Times, may collect "up to $1.6B" and is the primary beneficiary of the tax credit in the Senate bill. This smells like an earmark from Senator Rockeller to the telco.

Comcast has been modestly promoting DOCSIS 3.0 as "50 megabits," although the equipment they are installing is 160 megabits shared. Perhaps to ensure the subsidy, Comcast is now is calling the same service "100 megabits" in an article by Steve Overbeck in the Salt Lake City Tribune. Since there's no clear method of defining speed in the bill, this will become a crucial "detail" to be established by the FCC/NTIA. The agencies will allocate $billions as they make the rules.

In Japan and France, they are calling 160 megabits shared a "100 megabit service." Most users who have computers fast enough to run at 100 meg actually are measuring close to that speed because the full capacity is rarely in use. Few sites allow you to surf faster than about 1 megabit, no commercial video streams over the net are more than 3 or 4 megabits, and few FTP/download sites can hit that speed. No one knows for sure what speeds will be when the shared 160 has many users. None of the technical people even take a public guess, and there is no public traffic model. 36 megabits shared - today's DOCSIS - nearly always hits ten megabits for me on Time Warner, and a Massachusetts friend writes he almost always gets the 20 megabits in the service he buys in a similar 36 megabit shared service. Multiplexing works better with a higher total, so I think it's reasonable to assume 160 shared will generally deliver a third of that to each home.

I've therefore estimated 160 shared will be "50 meg 95+% of the time." My guess is the actual results will be better, but we won't know until 2010-2011 when we have the data from real networks with hundreds of thousands of customers.

Cable has a second alternative to meet the "100 megabit" standard. TI is now sampling a 320 megabit (shared) version of their Puma cable modem chip, with Broadcom promising similar. DOCSIS 3.0 designers have been thinking ahead, and the standard is designed to reach 1 gigabit in each direction. That's enough to provide the 50 and 100 megabits for many years even with high traffic growth from video over the net.

Upstream is a separate issue. The TI based modems shipping by the hundreds of thousands also bond 4 upstream channels, for a nominal 120 megabits shared. That easily meets the 15 or 20 meg upstream minimum required and is a crucial part of the DOCSIS 3.0 standard. However, only one vendor is certified for upstream by Cablelabs for the other side of the connection, the modem termination system. Top people tell me the technical and cost problems are solved so that could easily be included. That's not yet proven in the field.

The Senate language, incidentally, is "Qualified equipment means equipment that provides current- or next-generation
broadband services at least a majority of the time during periods of maximum demand to each subscriber." But what are "Qualified equipment means equipment that provides current- or next-generation broadband services at least a majority of the time during periods of maximum demand to each subscriber, ?" If "maximum demand" means Katrina or 9/11 style peaks, no one passes. If it means "busiest two hours on an average day" well designed cable systems pass easily.

Perhaps we'll find some answers on February 19th in D.C.