Kevin,
Thanks for the reply. I think you have answered most of my doubts. But I would
like to be clear that, is there a very strong reason why you run this in
production even it often causes unnecessary lower MSS with lower performance?
Thanks,
Cheng Cui
On 3/7/18, 3:35 PM, "Kevin Bowling" wrote:
Cheng,
We run this in production at Limelight Networks (i.e toward a broad
spectrum of Internet hosts) and must to deal with some uncommon
network topology. There are currently some limitations as you point
out.
Like you say the signaling is not perfect and we do often clamp MSS
unnecessarily. There is also no probing to see if we can expand the
MSS later.
I think those issues should be fixed up before it's enabled by default
and I don't know anyone working on it at the moment.
Regards,
On Wed, Mar 7, 2018 at 8:35 AM, Cui, Cheng wrote:
> Dear all,
>
> Reading through the tcp blackhole detection code (support RFC 4821) in
FreeBSD including the recent bug fixes, I am wondering why is it still not
enabled in default? Given the fact that this implementation was a merge from
xnu, and the xnu has enabled it in default, do we have a plan to enable it in
default? Or is there any concern about the side-effect from it as performance
regression against some false positive blackhole event like a temporary link
flap, which is long enough to trigger a lower MSS but shorter than 6 RTO?
>
>
https://opensource.apple.com/source/xnu/xnu-1456.1.26/bsd/netinet/tcp_timer.c.auto.html
<< enabled in macOS 10.6
> https://reviews.freebsd.org/rS322967 << bug fixes
> https://reviews.freebsd.org/rS272720 << merge from xnu
>
> Thanks,
> --Cheng Cui
> NetApp Scale Out Networking
> https://netapp-meeting.webex.com/meet/chengc
>
>
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