[olug] Network performance analysis

Matthew G. Marsh olug4mgm at paktronix.com
Fri Nov 21 17:08:07 CST 2014

Links internally work fine?

Links to ISP website work fine?

Basically if the "perceived" issue is slowness opening a link, and you 
suspect networkish issues (DNS, Proxy, Inet, etc) then start local and 
work towards remote.

If even local opens up slow then you have either DNS or security software 

Also - try multiple methods:  ; if you suspect DNS

ftp://ftp.kernel.org  ; if you suspect proxy/security setings

and of course you can play around with:


just for kicks...

BTW - better than any speedtest is to download a recent kernel from 
kernel.org and use a watch... seriously provides a real world latency and 
speed test unless of course you are on the 10G direct fiber link...

The other lurking issue is latency. That is best addressed after you rule 
out DNS/security/proxy/routing issues.

in latency some easy tests are:

ping -n -v -M time {your local gateway}

then move outwards (also good for diagnosing ISP traffic patterns)

And of course there is always tracepath if you suspect async routes...


On Thu, 20 Nov 2014, Bill Brush wrote:

> Rob I'm painfully (agonizingly) aware of how many variables I'm
> dealing with here.
> To go into a little more detail, the raw speed seems fine for the most
> part.  We're seeing some traffic spikes on the internet link up to the
> limit, but it's rarely sustained.  A speed test at speedtest.net
> usually comes back at around 90% of our nominal speed for our link.
> The main "symptom" seems to be a lag in things starting to move.  So
> if you click a link it sits there and thinks about it, then moves.
> Sometimes this is a few seconds, sometimes it's over a minute.
> I'm going to set up a 30 day trial of Solarwinds bandwidth analysis
> pack and hopefully it will show me something.  My forays with
> Wireshark have not turned up anything obvious.
> On Thu, Nov 20, 2014 at 2:22 PM, Rob Townley <rob.townley at gmail.com> wrote:
>> Bill,
>> i feel your pain.
>> Keep in mind "slowness" can be caused at many layers of the network.
>> -physical tests to verify Cat6 compliance from (PC) patch cable to wall
>> plate thru cable run back to patch panel thru another patch cable ( network
>> switch).  This could be an electrician with a ~$2500.00? Cat6 tester.  $per
>> wall plate
>> -firmware on NIC / motherboard
>> -device driver version
>> -10Mbps half-duplex vs 1000Mbps FullDuplex
>> -switch
>> -vPro / IPMI
>> -IPv6 vs IPv4 issues
>> -DNS slowness or timing out
>> -router
>> -wireless channel (1 ,6, 11)
>> On Nov 20, 2014 12:20 PM, "Bill Brush" <bbrush at gmail.com> wrote:
>>> Hello all.
>>> I don't post much, but I've been lurking around here for many years.
>>> I'm looking for help investigating complaints that our network is
>>> "slow".  I have a rudimentary knowledge of doing packet captures, and
>>> the basics, but an in-depth investigation is beyond my current skills.
>>> I inherited this network a couple years ago, and I will freely admit
>>> that prior to this I had never had to worry about my infrastructure so
>>> I have not checked for pre-existing issues.
>>> So is anyone in the Omaha area an expert at network analysis?  If it's
>>> your day job we can discuss your hourly rates.
>>> Thanks!
>>> Bill
>>> _______________________________________________
>>> OLUG mailing list
>>> OLUG at olug.org
>>> https://lists.olug.org/mailman/listinfo/olug
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Matthew G. Marsh
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Phone: (402) 932-7250
Email: olug4mgm at paktronix.com
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