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Archiver > TMG > 2003-03 > 1046634906


From: Dennis Lee Bieber <>
Subject: Re[2]: [TMG] Backup media
Date: Sun, 02 Mar 2003 11:55:06 -0800
References: <4.3.2.7.2.20030301134614.06246ce0@popd.ix.netcom.com><4.3.2.7.2.20030301134614.06246ce0@popd.ix.netcom.com>
In-Reply-To: <5481471299.20030301214818@comcast.net>


On or about 18:48 03/01/03 a carrier pigeon from Eric Haas delivered:

>Saturday, March 1, 2003, 4:56:56 PM, you wrote:
>
>
>DLB> 28800 * 2 => 57600bps / 8 => 7200 bytes/second.
>
>That 8 should actually be a 10. Each transmitted byte gets a start bit
>and stop bit added to it.

Between the computer and the modem, yes... but that link should be
running at 115K anyway.

These highspeed modems, however, tend to strip the start/stop bits
from the data, perform various compression methods on the remains (BTLZ
used be the common one), and then send the data stream as something closer
to a synchronous packet (which doesn't use the start/stop bits needed by an
asynchronous stream). Yes, there is still some overhead for a CRC check,
and start of packet synchronization... but a few bytes on a 256 byte packet
isn't as much. Between the stripping of start/stop, and the compression
method, the ideal throughput cat reach 4:1 (64 "bytes" transferred over the
line for every 256 bytes are actual data) -- Seldom reached though; 2:1 is
more sustainable (I normally get a 42K connection, and have two large file
transfers in parallel each acheiving 4Kbytes/sec -- which would be 80Kbits
using 10bit characters)

--
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> | Dennis Lee Bieber <
> PGP keys available | RSA keys preferred <
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