UDP traffic, msg size exceeds 9215 Bytes

Meny Yossefi menyy at mellanox.com
Thu Nov 28 13:00:39 UTC 2013

Nope, I wasn't aware of it.
It works now. Thanks!


-----Original Message-----
From: Marc Olzheim [mailto:marcolz at stack.nl] 
Sent: Thursday, November 28, 2013 2:50 PM
To: Meny Yossefi
Cc: freebsd-net at freebsd.org; Oded Shanoon
Subject: Re: UDP traffic, msg size exceeds 9215 Bytes

On Thu, Nov 28, 2013 at 12:43:43PM +0000, Meny Yossefi wrote:
> Hi all,
> We've been running some benchmarks (Netperf, Iperf) on our driver (Mellanox), and witnessed an odd behavior.
> We saw that when running UDP traffic with msg size larger than 9215 bytes, it gets dropped for some reason. MTU is 1500.
> We've spotted the same behavior on different vendors which lead us to believe there's some kernel issue that we are missing here.

Did you meddle with sysctl net.inet.udp.maxdgram yet ? The default value is
6 * 1536 = 9216 bytes...


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