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Re: [PATCH 0 of 4] QUIC path MTU discovery

Sergey Kandaurov
July 28, 2023 11:52AM
> On 6 Jul 2023, at 17:57, Roman Arutyunyan <arut@nginx.com> wrote:
>
> Updated PMTUD:
>
> - Eliminated getting local interface MTU. This was too intrusive and platform-
> dependent.

RFC 8899 how the following statement on this:

A DPLPMTUD sender is RECOMMENDED to utilize information about
the maximum size of packet that can be transmitted by the sender
on the local link (e.g., the local link MTU). <..> This avoids
implementations trying to send probe packets that cannot be
transferred by the local link.

I won't insist on keeping this part,
but we can reconsider it in future.

>
> - Added timeout (1 sec) before each PMTUD iteration to reduce PMTUD traffic
> in short connections.

While I understand that this is used to avoid over-utilising paths,
such long deferred probes can cause under-utilisation.
Probably some value derived from path's PTO might have sense, e.g. 3PTO.
The delay as implemented causes delays for subsequent probes as well,
which might be too conservative.

>
> - Size search reimplemented. MTU is increased by 256 bytes until failure,
> after which binary search is used. Real life MTU will be around 1500, while
> initial payload size is 1200. Doing binary search from 65k down to 1500 will
> produce a lot of failed syscalls and useless traffic. Ascending from 1200
> to a first failre will be quick.

I agree that starting from below have more sense.
Further, if multiplying probe MTU, as proposed in addendum,
looks more suitable for benchmarking.
OTOH, 256 byte steps may be more realistic approach,
given that well known PMTUs usually don't exceed 1500 bytes.

>
> --
> Roman Arutyunyan
> _______________________________________________
> nginx-devel mailing list
> nginx-devel@nginx.org
> https://mailman.nginx.org/mailman/listinfo/nginx-devel

--
Sergey Kandaurov
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Subject Author Views Posted

[PATCH 0 of 3] QUIC path MTU discovery

Roman Arutyunyan 939 March 28, 2023 10:52AM

[PATCH 1 of 3] QUIC: changed path validation timeout

Roman Arutyunyan 149 March 28, 2023 10:52AM

Re: [PATCH 1 of 3] QUIC: changed path validation timeout

Sergey Kandaurov 162 April 24, 2023 08:16AM

Re: [PATCH 1 of 3] QUIC: changed path validation timeout

Roman Arutyunyan 129 May 03, 2023 09:02AM

Re: [PATCH 1 of 3] QUIC: changed path validation timeout

Sergey Kandaurov 102 May 09, 2023 06:12AM

Re: [PATCH 1 of 3] QUIC: changed path validation timeout

Sergey Kandaurov 114 May 09, 2023 09:00AM

Re: [PATCH 1 of 3] QUIC: changed path validation timeout

Sergey Kandaurov 112 May 09, 2023 11:08AM

Re: [PATCH 1 of 3] QUIC: changed path validation timeout

Roman Arutyunyan 128 May 09, 2023 11:30AM

[PATCH 2 of 3] QUIC: allowed ngx_quic_frame_sendto() to return NGX_AGAIN

Roman Arutyunyan 153 March 28, 2023 10:52AM

[PATCH 3 of 3] QUIC: path MTU discovery

Roman Arutyunyan 207 March 28, 2023 11:00AM

Re: [PATCH 3 of 3] QUIC: path MTU discovery

Sergey Kandaurov 140 May 01, 2023 01:00PM

Re: [PATCH 3 of 3] QUIC: path MTU discovery

Maxim Dounin 126 May 01, 2023 04:42PM

Re: [PATCH 3 of 3] QUIC: path MTU discovery

Roman Arutyunyan 132 May 08, 2023 08:16AM

Re: [PATCH 3 of 3] QUIC: path MTU discovery

Sergey Kandaurov 112 May 08, 2023 11:12AM

[PATCH 0 of 4] QUIC path MTU discovery

Roman Arutyunyan 86 July 06, 2023 09:58AM

[PATCH 1 of 4] QUIC: removed path->limited flag

Roman Arutyunyan 91 July 06, 2023 09:58AM

Re: [PATCH 1 of 4] QUIC: removed path->limited flag

Sergey Kandaurov 91 July 28, 2023 11:52AM

[PATCH 2 of 4] QUIC: removed explicit packet padding for certain frames

Roman Arutyunyan 90 July 06, 2023 09:58AM

Re: [PATCH 2 of 4] QUIC: removed explicit packet padding for certain frames

Sergey Kandaurov 83 July 28, 2023 11:52AM

[PATCH 3 of 4] QUIC: allowed ngx_quic_frame_sendto() to return NGX_AGAIN

Roman Arutyunyan 90 July 06, 2023 09:58AM

Re: [PATCH 3 of 4] QUIC: allowed ngx_quic_frame_sendto() to return NGX_AGAIN

Sergey Kandaurov 86 July 28, 2023 11:52AM

[PATCH 4 of 4] QUIC: path MTU discovery

Roman Arutyunyan 95 July 06, 2023 09:58AM

Re: [PATCH 4 of 4] QUIC: path MTU discovery

Roman Arutyunyan 96 July 07, 2023 04:00AM

Re: [PATCH 4 of 4] QUIC: path MTU discovery

Sergey Kandaurov 100 July 28, 2023 11:54AM

Re: [PATCH 4 of 4] QUIC: path MTU discovery

Roman Arutyunyan 93 July 31, 2023 01:36PM

Re: [PATCH 4 of 4] QUIC: path MTU discovery

Sergey Kandaurov 122 August 08, 2023 05:50AM

Re: [PATCH 4 of 4] QUIC: path MTU discovery

Roman Arutyunyan 92 August 10, 2023 06:22AM

Re: [PATCH 4 of 4] QUIC: path MTU discovery

Sergey Kandaurov 87 August 10, 2023 10:20AM

Re: [PATCH 4 of 4] QUIC: path MTU discovery

Roman Arutyunyan 105 August 14, 2023 09:54AM

Re: [PATCH 0 of 4] QUIC path MTU discovery

Sergey Kandaurov 86 July 28, 2023 11:52AM



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