[10831] in Commercialization & Privatization of the Internet
Re: Two-way Internet service from Continental Cable?
daemon@ATHENA.MIT.EDU (David Herron)
Fri Mar 11 17:39:37 1994
From: "David Herron" <david@twg.com>
To: "Jeffrey K. MacKie-Mason" <jmm@merit.edu>
Cc: merit.com-priv@merit.edu
Date: Fri, 11 Mar 94 9:52:26 PST
In-Reply-To: Your message of Thu, 10 Mar 1994 15:21:39 -0500.<199403102021.PAA10525@merit.edu>
...
>Continental Cable had announced it was beginning to offer Internet
>connections over its coax cable lines in Cambridge, MA.
> ... claim that the service would be two-way symmetric, that is both
>incoming and outgoing traffic over the cable. In the past I'd only
>heard of asymmetric cable connections: incoming over the coax,
>outgoing over the twisted pair (phone line). What is Continental
>doing differently that enables them to offer symmetric service?
In my former life as a University system administrator (CS Department; we
were the little guys in the good fight against the evil empire at the
computing center ;-)) ...
The campus had purchased and installed a "broadband network" from Ungermann
Bass. This was, so the guys who worked in the campus Communications
department told me, the very same sort of hardware which normal everyday
cable TV systems is built from. Namely:
- Really thick coax which goes everywhere.
- A "head end" box which is a repeater.
- Broadcasting nodes on the network transmitted at one frequency range.
- The "head end" box picked up the signals within the frequency range
designated as the broadcast band. It then repeated those signals
into another frequency range and rebroadcast.
- Any receiving nodes listen on the other frequency range.
- Normal rules for Cable TV was to divide the spectrum into
5 MHz wide chunks.
- Er... 5 MHz might not be right. However UB sold us some boxes
which were ethernet bridges that connected to the Cable TV
system. This provided ethernet-like connectivity over what
was ostensibly a Cable TV system. The bandwidth through the
ethernet bridge boxes which UB sold us was 5 Mbit/second versus
the normal 10 Mbit/second of regular ethernet. The 5 Mb/s need
not require 5 MHz of bandwidth.
- Other companies sold boxes which did 10 Mbit/sec ethernet bridging
onto the same media. (Chipcom comes to mind). Some of them required
allocating a wider chunk of the spectrum to this purpose. Others
somehow squeezed the 10 Mb/s into the normal standard channel spacing.
- These ethernet bridging boxes were, 7-8 years ago, rather expensive.
Many thousands of dollars.
- This still serves the University as it's campus wide network media.
- Since the boxes were just ethernet bridges, any faults within
a departmental LAN were felt everywhere. However my department
somehow wangled to have a box which included a DEC-LANBridge in it
that made sure traffic for our departmental LAN would not get out
into the main network.
Winding that technology forward to today one can see that with greater
levels of integration of features, greater processing power available, etc,
that one can make a box which is an Internet router and also a cable TV
converter and do so at a much better cost than 7-8 years ago. The last time
I had cable some things seemed to indicate the cable TV company could
transmit commands to my converter and get back responses.
So it is certainly possible for Cable TV to be in the business of providing
ethernet to houses. However if there's only one ethernet speed channel for
the whole cable system, it can rather quickly get swamped. Think about
connecting 90,000 nodes to a single ethernet segment. It will quickly fail.
Perhaps since PSI is right here on the mailing list they can give a few
technical bits about what PSICable is and how it's done. If I'm way off
base here it'd be great if they'd say so ...
In any case I've been having ideas about ... "Hmm.. Y'know, if customers can
get directly to me over the network why do I have to work in a company to
sell my software?" .. but there's all sorts of business details to worry
about which bore me to tears and, so ...
<- David Herron <david@twg.com> (work) <david@davids.mmdf.com> (home)
<-
<- Real life involves many economies where the choices and gains
<- are more than some visible exchange involving money.
