And if there are things like NAT or routing over RFC1918 space, then it
breaks PMTUD ( http://en.wikipedia.org/wiki/Path_MTU_Discovery )
--
Josh Reynolds
CIO, SPITwSPOTS
www.spitwspots.com
On 03/05/2015 04:14 PM, Mike Hammett wrote:
My max DNS UDP packet size is 512. I assume that's the default. MTUs
over 1500 wouldn't affect any traffic flowing through as the device on
the other end wasn't able to pass a packet more than 1500 to begin
with. I'd imagine what was happening is that your MT was generating
DNS requests that were larger than could pass through the Intarwebz.
-----
Mike Hammett
Intelligent Computing Solutions
http://www.ics-il.com
<https://www.facebook.com/ICSIL><https://plus.google.com/+IntelligentComputingSolutionsDeKalb><https://www.linkedin.com/company/intelligent-computing-solutions><https://twitter.com/ICSIL>
------------------------------------------------------------------------
*From: *"Glen Waldrop" <[email protected]>
*To: *[email protected]
*Sent: *Thursday, March 5, 2015 7:06:55 PM
*Subject: *Re: [AFMUG] downloads stalling but streaming, speedtests,
etc. OK
I bumped the L2 MTU to 2028, max of that particular unit and set the
other side to match, then DNS stopped working. Traffic worked, I could
ping by IP but not by name. Of course my DNS server was on the other
side of that cable, so a handful of folks were having issues.
I dropped the L2 MTU back to default on MT of 1600, improved, but not
100%.
I had the DNS max packet size set to 4048 or so, dropped it back down
to 1536, started improving.
UDP speed tests were all over the map, then would randomly quit. TCP
was decently reliable, though not as fast as they should be.
----- Original Message -----
*From:* Mike Hammett <mailto:[email protected]>
*To:* [email protected] <mailto:[email protected]>
*Sent:* Thursday, March 05, 2015 6:42 PM
*Subject:* Re: [AFMUG] downloads stalling but streaming,
speedtests, etc. OK
Packet capture?
-----
Mike Hammett
Intelligent Computing Solutions
http://www.ics-il.com
<https://www.facebook.com/ICSIL><https://plus.google.com/+IntelligentComputingSolutionsDeKalb><https://www.linkedin.com/company/intelligent-computing-solutions><https://twitter.com/ICSIL>
------------------------------------------------------------------------
*From: *"CBB - Jay Fuller" <[email protected]
<mailto:[email protected]>>
*To: *[email protected] <mailto:[email protected]>
*Sent: *Thursday, March 5, 2015 5:57:03 PM
*Subject: *Re: [AFMUG] downloads stalling but streaming,
speedtests, etc. OK
wow....how did you figure that out?
----- Original Message -----
*From:* Glen Waldrop <mailto:[email protected]>
*To:* [email protected] <mailto:[email protected]>
*Sent:* Wednesday, March 04, 2015 11:18 PM
*Subject:* Re: [AFMUG] downloads stalling but streaming,
speedtests, etc. OK
I've got one similar to that.
DNS doesn't work.
TCP works okay, but DNS just absolutely fails.
Turns out the Ethernet port is dying on me. I've got extra
hardware in the
air, so quick fix is a wireless shot from the AP to the ground
to the switch
that feeds the PTP shots.
It'll work until I can fix it properly.
What is happening in my case is the Ethernet is dropping
packets, frames,
something. TCP retransmits, UDP just disappears.
Not sure if that will explain your broken download issue, but
it is one of
those odd problems.
Could be the server side is just dropping the connection after
100+
retransmits.
----- Original Message -----
From: "Ken Hohhof" <[email protected] <mailto:[email protected]>>
To: <[email protected] <mailto:[email protected]>>
Sent: Wednesday, March 04, 2015 10:10 PM
Subject: [AFMUG] downloads stalling but streaming, speedtests,
etc. OK
>
> I can't figure this out, but it seems like the sort of thing
someone else
> here will say "oh, I know what causes that".
>
> I've been tracking a smattering of customer complaints about
downloads
> just stopping, and finally was able to reproduce it. I
Googled for large
> file downloads and took the first one that came up:
> https://www.futurehosting.com/network-test-files/
> and found the downloads would stop repeatedly at the same
point.
> Different for each file and server location, but the same
for repeated
> downloads of the same file. For example the 100MB file from
Michigan kept
> stopping at 8MB. It chugged along fine, then slowed
dramatically and
> stopped, with no traffic either direction. Yet a ping to
the same IP
> address never had a problem.
>
> Note it is NOT the computer, the server, or last mile
radios. I was able
> to see it going only through backhaul radios and routers, no
AP/CPE. And
> it works fine with the same computer here at my house on AT&T.
>
> Tomorrow I need to chase it back toward my network border.
I am not
> conversant with Wireshark so have not done that yet, am not
looking
> forward to it. One pesky customer claims to have done that
and seen TCP
> retries and out-of-order packets, maybe he's right, maybe he
is just
> misinterpreting the data.
>
> So .............. what can cause HTTP downloads to stall and
stop, while
> other stuff like Youtube and Hulu and speedtest.net are fine?
>
>
