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From: Michael Tuexen <tuexen@freebsd.org>
To: Xin Long <lucien.xin@gmail.com>
Cc: "linux-sctp @ vger . kernel . org" <linux-sctp@vger.kernel.org>,
	Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Subject: Re: add SPP_PLPMTUD_ENABLE/DISABLE flag for spp_flags
Date: Tue, 18 May 2021 21:19:21 +0200	[thread overview]
Message-ID: <DE8A113C-DF80-412E-A5C1-C0731E1757E2@freebsd.org> (raw)
In-Reply-To: <CADvbK_eKp+1OUT1+DLdv5w5_Azsh7W3F46p=3hCoiP8c13bEFg@mail.gmail.com>



> On 18. May 2021, at 20:33, Xin Long <lucien.xin@gmail.com> wrote:
> 
> On Tue, May 18, 2021 at 1:38 PM Michael Tuexen <tuexen@freebsd.org> wrote:
>> 
>>> On 18. May 2021, at 18:43, Xin Long <lucien.xin@gmail.com> wrote:
>>> 
>>> Hi, Michael,
>>> 
>>> We're implementing RFC8899 (PLPMTUD) on Linux SCTP recently,
>>> and to make this be controlled by setsockopt with
>>> SCTP_PEER_ADDR_PARAMS, as in
>>> 
>>> https://datatracker.ietf.org/doc/html/rfc6458#section-8.1.12:
>>> 
>>> we need another two flags to add for spp_flags:
>>> 
>>> SPP_PLPMTUD_ENABLE
>>> SPP_PLPMTUD_DISABLE
>>> 
>>> Do you think it makes sense? if yes, does the RFC6458 need to update?
>>> if not, do you have a better suggestion for it?
>> It is great new that you want to implement RFC 8899. I plan to do the
>> same for the FreeBSD stack.
>> 
>> In my view, RFC 8899 is the right way to implement PMTU discovery.
>> So I will just use the SPP_PMTUD_ENABLE and SPP_PMTUD_DISABLE. I don't
>> think that the user needs to control which method is used.
>> I you want to support multiple versions, I would make that
>> controllable via a sysctl variable. But I think for FreeBSD, support
>> for RFC 8899 will be the only way of doing PMTU discovery. There
>> might be multiple choices for details like how to do the searching,
>> how long to wait for some events. These will be controllable via
>> sysctl.
>> 
>> So in my view, there is no need to extend the socket API. What do you think?
> OK, that makes sense to me.
> 
> Another thing I want to know your opinion on is:  do you think the HB
> should be created
> separately for PLPMTUD probe, instead of reusing the old HB that
> checks the link connectivity?
Yes. I think testing for connectivity is conceptually different
from testing a particular PMTU. When testing for PMTU, I think
about sending probe packets. Not that they consist of a HB chunk
bundled with a PAD chunk.
> As the HB for PLPMTUD probe might get lost, which we don't want to
> affect the link's
> connectivity.
Yes, I agree completely.

Best regards
Michael
> 
>> 
>> Best regards
>> Michael
>>> 
>>> Thanks.
>> 


  reply	other threads:[~2021-05-18 19:19 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-18 16:43 Xin Long
2021-05-18 17:38 ` Michael Tuexen
2021-05-18 18:33   ` Xin Long
2021-05-18 19:19     ` Michael Tuexen [this message]
2021-05-19 22:24       ` mleitner
2021-05-20  2:05         ` Xin Long
2021-05-20  7:06           ` tuexen
2021-05-20 15:13             ` Xin Long
2021-05-19 16:18     ` Xin Long
2021-05-19 18:15       ` Michael Tuexen
2021-05-19 18:44         ` Xin Long
2021-05-19 22:44           ` mleitner
2021-05-19 23:16             ` Michael Tuexen
2021-05-20  0:45               ` Marcelo Ricardo Leitner
2021-05-20  6:59                 ` tuexen
2021-05-20 19:27                   ` Marcelo Ricardo Leitner
2021-05-19 23:10           ` Michael Tuexen

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