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Date:      Sun, 30 Apr 2000 04:20:30 -0500 (CDT)
From:      Joe Greco <jgreco@ns.sol.net>
To:        chat@freebsd.org, ryan@sasknow.com
Subject:   Re: Max. T1 throughput?
Message-ID:  <200004300920.EAA55001@aurora.sol.net>

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> There seems to be some confusion around our region on what the maximum
> throughput of a T1 is.  (Actually, we are on a 1.544Mbps leased SDSL line
> from a local ISP.  The package was sold to us as a burstable T1).
> 
> My preliminary tests seem to show a segregation between up and
> down... Each maxing out at about 96KB/sec when the other is practically
> idle.  Not the near-198KB/sec that I think I should be getting.
> 
> Is SDSL the key, here?  Perhaps I took "Synchronous" in the wrong
> way.  Does "Synchronous" imply UP = DOWN = 1.54Mbps / 2?

A T1 is 1.544 megabits per second.  Dividing by 8, you get 193 kilobytes
per second, an often-quoted number as being T1 capacity.

By the time you get through with all sorts of odd issues, though, I find
that a T1's peak capacity is about 160K/s.

SDSL may imply that you are being sold a technology whose peak capacity is
the aforementioned T1 data speed.  However, many DSL technologies adapt to
line conditions and distance by providing less overall throughput.  It is
possible that your line is not capable of (much) more than you're getting.
A T1 would be, however, since a T1 line is engineered with appropriate
electronics (such as repeaters) to make the circuit work.  A T1 cannot
vary in speed, since it must be able to bear multiplexed phone circuits.
It may experience errors, however.

-- 
... Joe

-------------------------------------------------------------------------------
Joe Greco - Systems Administrator			      jgreco@ns.sol.net
Solaria Public Access UNIX - Milwaukee, WI			   414/342-4847


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