M1X and RR

[richb at pioneer.ci.net (Rich Braun)]

Jerry wrote:
> It would be nice to see some people actually start using DSL services. Where
> DSL is a guaranteed bandwidth to the provider, cable modem is shared over an
> effective LAN. I have yet to experience any slow downs that I could
> attribute to traffic within M1Xs network. And in both cases, once you get up
> to the provider's sites, you are in a shared bandwidth. M1X limits the
> number of cable modem subscribers on a segment. I was told that if that
> number is exceeded, they will split the segment. 

As a fairly major developer of xDSL service, I concur with this.  The
limitation of the rival technology, cable modem, is not in the shared
segment.  AT&T crafted a specification, which apparently most other
companies are adopting, which calls for exactly 420 "passed homes" on
each cable segment.  The DOCSIS standard calls for 40 megabits of raw
capacity on each cable segment.  Doing the math, if 100% of your closest
419 neighbors are (a) subscribing to the 'net, and (b) downloading at the
same time you are, your share of download capacity is 100 kilobits--faster
than today's modems.  And the odds of everyone using it simultaneously are,
well, precisely zero unless you conference everyone together and do
a deliberate test.

The head-end hardware and the monitoring systems are where the bottlenecks
are.  If M1X or RCN or whomever isn't aware of the usage levels on a
segment, they won't bother splitting it; if they don't have a way for
customer service to give feedback to the engineers who build cable segments,
they won't upgrading head end capacity.

All that sits at a cable head-end for Internet service is the cable-modem
head-end devices for each segment served, and some Cisco router hardware to
feed data back to a transit pipe (to companies like UUNET or GTE
Internetworking or perhaps a NAP if the cable company is a member of one).
The Cisco router hardware works the same at RCN or Shore.Net or wherever.
The size of the pipes to each head-end site can range from a single T1 to
multiple OC-3's; if I had to guess, most cable providers use a T-3.  The
monitoring software and procedures differ from one company to the next, which
means they may not keep close track of whether the head-end site pipes are
full.  That's where you'll find the quality differences.

Those quality differences will occur across ISP's regardless of how they
deliver the last mile.

Currently, cable companies are building coax to residential locations, and
traditional ISPs and phone companies are building copper to business
locations.  There is not a lot of activity thus far in building coax to
business locations, so I would assume the telcos and traditional ISPs
will dominate the businesses with T1/T3/xDSL service without much of a
challenge from cable purveyors.  I would also assume that xDSL will only
threaten cable-modem purveyors for a short period until the cable operators
get more of their pricing and physical-plant issues resolved.

-rich


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