iperf question

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If I do a simple iperf test such as this:

iperf -s on machine with IP 10.1.1.2
then
iperf -c 10.1.1.2

What speed is it telling me? The speed from server to the client (Rx
speed on client) or the speed from the client to the server (Tx on client)

The iperf tutorial says:

"By default, the Iperf client connects to the Iperf server on the TCP
port 5001 and the bandwidth displayed by Iperf is the bandwidth from the
client to the server."

Which would seem to be Tx speed on the client? or not?

Re: iperf question
wrote:

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Don't know.  You didn't post the test results.

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Yep.  It's the speed from the client to the server.
However, you can control the direction with various options.  Try
   Iperf -h
for a list.  

These might be useful:  
  -d, --dualtest           Do a bidirectional test simultaneously
  -r, --tradeoff           Do a bidirectional test individually
  -P, --parallel  #        number of parallel client threads to run


--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831-336-2558            jeffl@comix.santa-cruz.ca.us
# http://802.11junk.com jeffl@cruzio.com
# http://www.LearnByDestroying.com               AE6KS

Re: iperf question
Jeff Liebermann wrote:
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Caught me, I was trying to decide whatever result it presented referred
to what direction relative to one of the hosts to help me decide what to
look at.

I am troubleshooting a general speed issue and isolated it to the wired
LAN speed from the server which is highly asymmetrical. iperf reported
300 kbit in one direction and 70 Mbit in the other direction just
working on the wired 100 Mbit LAN using my notebook and also another
server for testing. Updating NIC drivers and turning off scalable
networking brought the low speed up to 5 Mbit which is still lame. The
server has a GigE card and there is a 100Mbit unmanaged switch . Forcing
link speed on the server to various auto/full/half didn't make much
difference. I suggested they replace the switch with a GigE switch which
makes sense because there are two servers with GigE capability. I think
the server NIC just doesn't like talking to the switch. The server had a
second onboard NIC and I switched to it and also tried various switch
ports and it didn't make a difference.


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I have tried switches like -d but it simply gives both results leaving
you to wonder which is what.

Re: iperf question
wrote:

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Good question, but an obvious answer, which you already supplied.

Hint:  If you have a problem that needs solving, then please supply:
1.  What problem are you trying to solve?
2.  What hardware and software do you have to work with?
3.  What have you done so far and what happened?

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I've seen this literally dozens of times.  Lots of causes ranging from
bad NIC's, NWAY negotiation failure, CAT5 cable wiring problems,
connector failure, media converter failure, hung ethernet switch,
full/half duplex problems at the NIC, overly busy server, etc.  I'm
going to be my usual obnoxious self and not offer any more until you
disclose what hardware you're working with and how you're doing the
iperf testing (specific command line incantations).  That's because
UDP and TCP testing often yield very different results.

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Wrong on both numbers.  I consistently get 90-95Mbits/sec from a
10/100baseT ethernet switch.  Obviously, the 300Kbit/sec is also
wrong.  You might try removing the intermediate switch, grab some
known good CAT5 cables, and go directly from the "other" server and
your notebook.  Also, check the settings on the ethernet port on both
machines.  You can sorta create the problem by having one set to full
duplex, and the other to half duplex.

Replace the cables, test server, and/or switch, one at a time, until
the problem evaporates.  It's called troubleshooting by substitution.

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It shouldn't make any difference.  Since updating the driver has such
a derastic effect, you might consider the possibility that the
unspecificed device with the NIC card is having a bad day.  It could
be busy from some errant process.  It could have a bad NIC.

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Any particular model number GigE card?  

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Maker and model?  Yeah, I know I'm demand a lot by asking you to
supply such details.  However, there are some boxes out there that are
little better than defective.

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Forcing it where?  At the server?  At the laptop?  With a mechanical
switch on your unspecified unmanaged switch?

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Yeah, that makes sense if the intermediate wiring is 1000baseT
qualified?  What manner of cable and how long?

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I also don't like talking to people and devices that I know nothing
about.

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Try a 2nd laptop in place of the server.  See if the unspecified model
GigE switch is the problem.

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If you have both directions, does it really matter which is which as
long as they're the same?  Methinks you're avoiding the problem.

Your question has absolutely nothing to do with wireless or wireless
internet.  You might consider asking the same question (with the
missing details supplied) in one of the networking newsgroups.


--
Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558

Re: iperf question
Jeff Liebermann wrote:
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just vanilla TCP using iperf -c <server IP>
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Agree, it is a remote location and I simply ran out of time because of
an ice storm that was closing in. I replaced the cables and have a GigE
switch on order as a replacement.


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Its a Dell Poweredge 1950 with dual onboard Broadcom Net Extreme II
NICs. I configured the other NIC and switched over to it but there was
no difference.

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It is a D-link something (can't read my notes)

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At the server.

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The switch is right above the servers so only short patch cables are needed.

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Yes, thank you much for your interest and suggestions.  I didn't go into
big details initially because I just wanted to understand what iperf was
telling me.

Re: NIC question & troubleshooting
x-posted to some other useful groups -

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