*BSD News Article 39757


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From: macleod@adoc.xerox.com (Peter MacLeod)
Newsgroups: comp.unix.bsd
Subject: Re: How does T1 work?
Date: 20 Dec 1994 03:14:28 GMT
Organization: Xerox Desktop Document Systems, Palo Alto, CA
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Eric Reid (rice@netcom.com) wrote:
: Ok, I've got another question for you all.. I'm interested in setting up 
: an ISP and most likely have an investor... I read in the INET-Acees FAQ 
: that a T1 will carry about 200 simultaneous phone lines (i.e. users)... 
: My investor, however, works in the phone industry (he owns his own 
: private long distance company) and deals a lot with T1s and he says that 
: they will only carry 24 conversations (a T1 only has 24 channels?)... He 
: would like to know if data conversations are different and if the data is 
: compressed.  Also, does anyone know of a reliable service provider in Las 
: Vegas, Nevada that provides T1 Connections to the Inet?

: Any help would be GREATLY appreciated!

: Eric
: -- 

If I understand your question correctly, you and your investor are talking
about two different things. One is the number of simultaneous digital voice
channels you can get on a T1 line, and the other is the number of network
connections a host can support with one T1 line. One can have, more or less,
as many network connections as one wants over a T1 line, or any other line,
for that matter, because net connections are not synchronous (in a packet
transmission sense--not in a low-level bit transfer sense). Voice lines, and
modems connected over voice-grade lines, need guaranteed bandwidth or they
die.

As the number of *active* network connections increases, the responsiveness
goes down. It's all a function of what your users do--whether they're all
doing huge FTPs, browsing stuff, or just sending email. Capacity planning is
hard, whether you're planning the capacity of your host or the capacity of
your network connections...and a lot of people get it wrong, and then have
to scramble to buy more gear before all of their users give up and go
elsewhere. 

-- Peter