At the risk of being anal retentive ( quiet, Rodgers :-> ) we mustn't forget
the MTU, window size, TCP and IP headers, and ack's. I believe we have done
a couple of threads along these lines over time. Memory probably doesn't
serve, but I believe one can count on a 10-15% overhead cost.
Also, it looks to me like the calculation below lost a couple of zeros along
the way. My fingers and toes tell me that 230 Mbytes=1840mbits, which
divided by 1.54 mbits per second comes out to 1195 seconds, or close to 20
minutes.
That would bring the actual file transfer speed come to about 164 seconds,
if everything works the way it is supposed to.
Chuck
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]] On Behalf Of
Brian
Sent: Saturday, November 04, 2000 7:23 PM
To: SH Wesson
Cc: [EMAIL PROTECTED]
Subject: Re: transfer rate
On Sun, 5 Nov 2000, SH Wesson wrote:
> How do we go about calculating how long it takes to calculate something
and
> the speed at which it is transferring. For instance, if we have a T1
> circuit (full 1.544MB) or a 128KB link, how long will it take to transfer
a
> 230MB file and how fast does it transfer per second, minute, etc. I can't
> seem to find anything that deals with calculating this sort of thing on
> Cisco's site. Thanks.
Its just basic mathmatics really. If a circuit is transmitting at
1.544Mbps, you can break it down as follows:
Convert to bytes
1544000 bits per second = 193000 bytes per second
193000 bytes per second / 1024 = 188.47656 kbytes per second
2300kbytes per second / 188.47656 = 12.203 seconds
Assuming ideal conditions (full wire speed etc)
Also realistically you need to back out the framing bits and recalculate
at 1536000 since the framing bits are unusable........but its not going to
move that figure much. With ISDN it would go like
128000 bites per second = 16000 bytes per second
16000 bytes per second / 1024 = 15.625 kbytes per second
2300kbytes per second / 15.625 = 147.2 seconds
And this jives, since a T1 is 12 times faster than a 128k isdn line.
Brian
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-----------------------------------------------
Brian Feeny, CCNP, CCDP [EMAIL PROTECTED]
Network Administrator
ShreveNet Inc. (ASN 11881)
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