# Fun_People Archive 14 Sepdog bandwidth

```Date: Tue, 14 Sep 93 20:14:09 PDT
To: Fun_People
Subject: dog bandwidth

From: bostic@vangogh.CS.Berkeley.EDU (Keith Bostic)
From: Tanenbaum's "Computer Networks", second edition, p.49:

Image that you have trained your St. Bernard, Bernie, to carry a box
fills up, you consider that an emergency.)  These floppy disks each
contain 250,000 bytes.  The dog can travel to your side, wherever you
may be, at 18 km/hour.  For what range of distances does Bernie have
a higher data rate than a 300 bps telephone line?

--- [WARNING!  Some answers are revealed in the following messages.  -psl] ---

______________________________________________________________________________
Subject: Re:  dog bandwidth

Hmm, lets see:

speed of Bernie = 5 m/s  (1.8 * 10^4 / 3600)

speed of modem =  30 bytes/sec

seconds to transfer a 'Bernie load' via 300bps modem
750000 bytes / 30 bytes/sec = 25000 seconds
distance traveled by Bernie in 25000 seconds: 	125000 m

seconds to transfer a 'Bernie load' via V.32bis/V.42 modem
750000 bytes / (14400/8) bytes/sec = 416.6 seconds
distance traveled by Bernie in 416.6 seconds: 	2083 m

seconds to transfer a 3.5" PC disk 'Bernie load' via V.32bis/V.42 modem
1.44 * 1024 * 1024 * 3 diskettes = 1509949 bytes
1509949 bytes / (14400/8) bytes/sec = 839 seconds
distance traveled by Bernie in 839 seconds: 	4195 m

Usenet via Bassett hound, anyone?

Jim

(Please don't embarrass me if I got the math wrong.)
______________________________________________________________________________

From: psl@acm.org (Peter Langston)
Subject: Re: Re:  dog bandwidth

Hmmm.... Gee, Jim, your math is perfect; but you had a couple of typos...

> seconds to transfer a 3.5" PC disk 'Bernie load' via V.32bis/V.42 modem
> 	1.44 * 1024 * 1024 * 3 diskettes = 1509949 bytes
> 	1509949 bytes / (14400/8) bytes/sec = 839 seconds
> 	distance traveled by Bernie in 839 seconds: 	4195 m

That probably should have said:
1.44 * 1024 * 1024 * 3 diskettes = 4529848 bytes (approx)
4529848 bytes / (14400/8) bytes/sec = 2516 seconds
distance traveled by Bernie in 2516 seconds: 	12580 m

But that's nothin'.

Here's the NeXT version (as Steve J. would have once stated it):

seconds to transfer a 'Bernie load' of NeXT Optical disks via 300bps modem
256 * 1024 * 1024 * 3 diskettes = 805306368 bytes
805306368 bytes / (14400/8) bytes/sec = 447392 seconds

distance traveled by Bernie in 447392 seconds: 	2,236,960 m

Note that this is more than one fifth of the way from the Earth's pole to
the equator.  Go Bernie!
-psl

```