Date: Thu, 6 Aug 1998 15:01:07 -0500 From: "sysadmin@mfn.org" <sysadmin@mfn.org> To: "'freebsd-questions@freebsd.org'" <freebsd-questions@FreeBSD.ORG> Subject: FTP Symptom of Network Problem... Message-ID: <01BDC14B.144DE880@noc.mfn.org>
next in thread | raw e-mail | index | archive | help
Greetings...
Before I go any further, here's the map:
________ _____________ _________
(coax) | | (coax) | | (coax) | segment |
-------| bridge |----------| 12 Stn. Hub |----------| monitor |
| | | (10 Base T) | | wkstn |
-------- ------------- ---------
"Gate" |... | ... | "monitor"
| | |
-----------------| | |-----------------
| | |
| | |
____________ ____________ ____________
| | | NIS/NFS | | |
| wkstn "A" | | server | | wkstn "L" |
------------ ------------ ------------
"nodeA" "server" "nodeL"
Ok. With that out of the way... This all started because
I was getting calls from angry users on machines in this
segment, all complaining (*loudly*) about "lag that often
runs over 30 seconds". Since these were *users* talking, I
figured I had an actual lag of maybe 30 microseconds, but
did the right thing, and checked it out anyway.
(1) All logs (netstat -i) show no problems: low total
utilization (averages about 5 million packets a day), with
the occassional Ierr (often zero, some as high as 10).
Except for where I specifically note otherwise, the
collision rates run about 1.5%. All machines have an
average cpu utilization of close to zero, with the peak
being on "server" of about 60%. Except for "server",
all machines are 486 hardware, with from 16mb to 128mb
of ram. "Server" is a P200 with 128mb of ram. There is no
"X" in use anywhere (not even loaded - I double checked).
(2) after investigating the complaints, the "lag" is
*only* reported when using telnet or ftp, although
I am unable to verify it from personal experience (and
I have *really* tried! - Just like going to the doctor,
as soon as you look for it, it's gone!). At least on
any "user" machine ("A" through "L") - see next paragraph.
(3) In an attempt to get a better look at things, I took
a machine from another segment, and put it on here. The
plan was for this machine to be a full-time monitor (as
the name above shows). Using "monitor", I was finally
able to experience problems myself, although only in FTP.
When logged in to "monitor", FTP speeds in retrieving files
from "server" runs under 10kbps, when it runs at all. Often
it will time out and be "reset by peer". It's not that bad
packets are being sent and resent: there is a packet sent,
and then a *long* pause, and then another, and the cycle
repeats.
(4) I can log in to any workstation and ftp from "monitor"
at full speed (~750kbps). I can log in to "monitor" and
ftp from any workstation at full speed. As far as I can
tell (user complaints aside), I can login to any workstation
("A" - "L") and get files full speed from "server", and
vice-versa. But as long as I am logged in to "monitor"
and trying to get files from "server", I'm in deep trouble.
The *only* thing I see "odd" here is a collision rate of
about 10% on "monitor".
(5) In trying to isolate "monitor"'s problem, I have:
> Replaced cabling for both "monitor" and "server"
> Replaced NIC's for both "monitor" and "server"
> Reloaded the OS for both "M" and "S"
> Both raised and lowered "MAXUSERS" for "server"
> Placed another machine in "monitor's" position
(no effect)
I am completely out of ideas here. I am also completely
out of patience :( I have a dozen angry users that I
can't placate because I can't even verify their problem
(other than on "monitor"), and I have what looks like a
physically impossible interaction between "monitor" and
"server"...
Anyone have *any* (no matter _how_ off the wall) ideas?
J.A. Terranson
sysadmin@mfn.org
(Please send answers direct, as I am no longer subscribed,
thanks!)
, and as far as I
can *prove*, only in 1 very certain configuration: going
from "server" to "
To Unsubscribe: send mail to majordomo@FreeBSD.org
with "unsubscribe freebsd-questions" in the body of the message
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?01BDC14B.144DE880>