Date: Sat, 09 May 1998 19:20:35 -0500 From: David Kelly <dkelly@HiWAAY.net> To: freebsd-questions@FreeBSD.ORG Subject: slow ftp and possible analysis? Message-ID: <199805100020.TAA11025@nospam.hiwaay.net>
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Got the great idea to download the demo WordPerfect for Linux and try
it on FreeBSD. Many, many megabytes over a 28.8k modem.
Using ncftp 1.9.5 to download the files I notice that its only arriving
at 800 bytes/sec, yet the modem lights are blazing (have been for over
9 hours).
Checked using stty, the serial rate between FreeBSD and the external
modem is 115k. SupraSonic 28.8k modem (upgraded to 33.6k firmware) has
LCD panel telling me I have a "V34 T24.0 R28.8 LAPM V42bis" connection,
so we're up to speed there.
Started checking other things and arrived at "netstat -p tcp". Didn't
like the duplicate packet numbers listed. Here's a summary:
nospam: {874} netstat -p tcp > first; sleep 60 ; netstat -p tcp > second
nospam: {875} diff first second
[...]
15,16c15,16
< 116084 packets (89021819 bytes) received in-sequence
< 33673 completely duplicate packets (46954564 bytes)
---
> 116124 packets (89076243 bytes) received in-sequence
> 33758 completely duplicate packets (47075824 bytes)
[...]
nospam: {876} expr 47075824 - 46954564
121260
Yow! 121k of duplicates in 60 seconds. Doesn't matter much if that
means there was 60k of real data and 60k of dupes or if there was 121k
of wasted bandwidth.
nospam: {877} expr 89076243 - 89021819
54424
Groan. 121k of waste and only 54k thru? Proportionally that agrees with
what ncftp is reporting and what I'd expect out of my modem.
Something is the matter. And I'm fairly certain its not anything on my
end. Right? The remote is ftp.sdcorp.com.
Aborted that download (fortunately I was downloading the 10-parts of
~5MB each, not the 80MB single file) and restarted using /usr/bin/ftp.
Got almost exactly the same numbers.
"sysctl -a" reports:
net.inet.tcp.rfc1323: 1
net.inet.tcp.rfc1644: 1
So I have TCP extensions enabled. Is this part of the problem?
I'm very suspicious the problem is on the other end. Packets wouldn't
be duplicated between here and there, would they? Or wouldn't they?
Hmmm.
--
David Kelly N4HHE, dkelly@nospam.hiwaay.net
=====================================================================
The human mind ordinarily operates at only ten percent of its
capacity -- the rest is overhead for the operating system.
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