Re: Help with slow transfers from pc to pc
From: Jim Fischer (jfischer_link5809_at_now.here.com)
Date: 07/26/03
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Date: Sat, 26 Jul 2003 11:42:18 -0500
Pepebuho wrote:
> Hi
> I have two computers running RH8.0, connected to a 10Mb hub.
>
> The network cards are 10/100 Mb. I feel that file tranfers between the
> systems are kind of slow.
>
> For example, I did ftp on one of them and a 1474560 byte file took
> 274 seconds (5.3 Kbyte/sec) according to ftp.
>
> Is it "normal"? How can I improve the transfer speed?
> I know I could maybe cook up a direct link cable between the two
> lan cards or get a 100Mb hub. But before I start throwing money
> at hardware I wonder if this is the best I can get with my current software.
FWIW, here are some theoretical values for 10Mb/s Ethernet:
- Time required to transmit a 1518 byte frame over 10Mb/s Ethernet:
Preamble 8 bytes, 64 bits, 6.4 us
MTU 1518 bytes, 12,144 bits, 1,214.4 us
IFG 96 bit times, 9.6 us
-------------------------------------
Time 1.2304 ms / frame (1.2304E-3 sec/frame)
- Theoretical minimum time required to transfer 1,474,560 bytes via
10Mb/s Ethernet:
1,474,560 bytes * (1 frame/1518 bytes) * (1.2304 ms/frame)
= 1.1952 seconds
~ 1.2 seconds
Note that this is a theoretical best value; in the "real world", the
time required to transfer this amount of data will typically require
more than 1.2 seconds. Nevertheless, even if the line utilization on
your 10Mb/s Ethernet connection is only 10% (1Mb/s), this particular
data transfer should finish in approximately 12 seconds. So if your RH8
boxes require 274 seconds to transfer this amount of data, then yeah,
I'd say there's a problem somewhere. ;-)
FWIW, using the 'scp(1)' program, I was able to transfer a 1,474,560
byte file between my RH9 box and an iMac (running OS-X) over an 11Mb/s
802.11b wireless "WiFi" LAN in less than 3 seconds.
To begin trouble-shooting this problem, I recommend you try some file
transfers using other programs -- e.g., scp(1) and wget(1) -- to see if
they too exhibit rediculously slow transfer rates like ftp. If every
file transfer program is rediculously slow, then it's a systemic problem
and not just an FTP problem. OTOH, if these other file transfer programs
are much faster, then you can focus your attention on FTP transfers.
--
Jim
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