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From: rpw3@redwood.UUCP (Rob Warnock)
Newsgroups: net.lan,net.news
Subject: Re: words to live by
Message-ID: <205@redwood.UUCP>
Date: Tue, 16-Jul-85 05:36:19 EDT
Article-I.D.: redwood.205
Posted: Tue Jul 16 05:36:19 1985
Date-Received: Thu, 18-Jul-85 06:47:32 EDT
References: <740@utcs.UUCP>
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Distribution: net
Organization: [Consultant], Foster City, CA
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Xref: watmath net.lan:922 net.news:3646

+------[from net.lan <740@utcs.UUCP>]---------
|        "Never underestimate the bandwidth of a
| 	station wagon full of tapes."
| - some wise words from
| 	Dr. Warren Jackson, Director, UTCS
+---------------

Reminds me of a calculation done a few years ago, on the cost-effectiveness
of 56kb lines for heavy batch transfer cross-country. My numbers may be off
a bit, but you'll get the idea:

	A. One 56kb line (clean, low errors) with fairly large block sizes
	   (say, 90% efficiency) can move about 550 Mbytes per 24 hours,
	   and costs about $1.50/mi/mo (???) or (for 2000 miles) about
	   $3000/mo plus about $1500/end/mo for modems or about $6000/mo
	   or $200/day, which is about $0.37 per megabyte.
	   
	   Average data rate is about 50 kbit/sec; latency for a 1 Mbyte
	   transfer is a little over 2.5 minutes.
	
	B. Using 2400 foot magtapes with large blocks (say, 90% efficiency)
	   at 6250 bpi, you can fit about 180 Mbyte/magtape. Three (3) of
	   those is about 540 Mbyte [same as 56kb line per day]. You can
	   send a parcel of three tapes by Federal Express (or equiv.)
	   every day at less than $50/parcel, or $50/day, or $0.09/Mbyte.

	   Average data rate is 50 kbit/sec; latency (1 Mbyte) is 24 hours.

	   [Open question: What is the shape of the weight/cost curve?
	    How many pounds or cubic feet can you ship in one 24-hour parcel?
	    I.e., is there a better ($$$/Mbyte) size than 3 tapes/parcel?]
	
Adding the case of the station wagon [above], we get:

	C. A medium-small station wagon (say, like my VW dasher) can hold
	   at least 25 cartons of a dozen tapes, or 300 tapes, or 162 Gbyte.
	   With a cross-country travel time of 40-48 hours (55 mph, 2 drivers,
	   minimal stops), running three shifts of station wagons might cost
	   (say) $1600/48hrs (6 salaries @ $30k + $1.50/gal @ 27mpg +
	   depreciation @ $0.20/mi) or about $0.01/Mbyte.

	   Average data rate is 15 Mbit/sec, latency (1 Mbyte) is 48 hours.
	
	D. Use cargo vans, 10 times as many tapes, double the expense, and
	   get roughly $0.002/Mbyte.

	   Average data rate is 150 Mbit/sec, latency (1 Mbyte) is 48 hours.

So the latency/bandwidth tradeoff holds "in the large", as well. I suspect,
however, that using larger packages in a "Federal Express" mode (say, using
some of the "Second Day" delivery services) could be as cost-effective as
the station wagon, with the same latency.

Anybody got any useful (i.e., current) cost numbers on a 2000 mile T-1
circuit, for comparison? It would be interesting to compare both land lines
and satellite circuits vis-a-vis the station wagon or parcel delivery.

Lest this be considered totally a joke, though it is humorous, has anybody
thought about sending USENET traffic via magtape and FedEx? How does it
compare to your phone bill? What is the effect on latency? What is the
effect on Stargate? ;-} I mean, with traffic still under a meg a day,
and with special delivery letters at $2-3 each (depending on weight),
we could USnail FLOPPIES and still win! And you don't have to worry about
your disks filling up while you're on vacation! Your mailbox will hold WEEKS
of floppies! ;-} And you don't have to worry about rnews tying up uuxqt or
(alternatively) flooding your system with inews'es...

Hmmm... maybe that's how we handle the flood of PCs that are about to
hit the net... offer them a cost-effective netnews floppy replication
and distribution service! You receive in the mail; you send with a modem
or (cheaper) just use mail. Make copies for your friends! Or put the
floppies inside the back cover of "NET Magazine: The Weekly Digest of
the Highlights of USENET (with commentaries by noted net authors, critics,
and flamers)"!

I noticed in a bookstore the other day that at least one magazine
is already being published in floppy format. 'S truth!


Rob Warnock
Systems Architecture Consultant

UUCP:	{ihnp4,ucbvax!dual}!fortune!redwood!rpw3
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