tcp_mtu_probing on by default?
Ritesh Raj Sarraf
rrs at researchut.com
Wed Feb 8 08:51:58 UTC 2012
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On Tuesday 07 February 2012 04:45 AM, Martin Pool wrote:
> I have helped a few people recently who were having path MTU
> discovery problems, causing bulk TCP transfers to hang
> quasi-intermittently. Once you know the likely cause it's fairly
> easy but it's a fairly annoying problem for someone who doesn't
> recognize it.
> There is a kernel sysctl "sudo sysctl -w
> net.ipv4.tcp_mtu_probing=1" that seems fairly effective at
> detecting when the problem is occurring and automatically fixing
> it. This implements RFC 4821. It is off by default in the
> kernel. I haven't seen any reports of problems caused by turning
> it on, but there may be some.
> I wonder if Ubuntu should turn it on in /etc/sysctl.d?
I have tried using it in the past because of my b0rken wireless router
from the ISP which had a different, non-standard, MTU size.
For me, the probing did not work at all and I had to manually set the
MTU every time I was at my home essid.
Will setting it on create trouble? Not sure. This will need testing.
Given the large number of mailing lists I follow, I request you to CC me
in replies for quicker response
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