linux-sctp.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Xin Long <lucien.xin@gmail.com>
To: Michael Tuexen <tuexen@freebsd.org>
Cc: "Marcelo Ricardo Leitner" <mleitner@redhat.com>,
	"linux-sctp @ vger . kernel . org" <linux-sctp@vger.kernel.org>,
	"Timo Völker" <timo.voelker@fh-muenster.de>
Subject: Re: add SPP_PLPMTUD_ENABLE/DISABLE flag for spp_flags
Date: Thu, 20 May 2021 11:13:35 -0400	[thread overview]
Message-ID: <CADvbK_eBZo3u90ZXBQuVBVov6V26580yXcXH-HZSFsgGU0OT7w@mail.gmail.com> (raw)
In-Reply-To: <364C37C5-5828-401C-BDD0-F345B288CE81@freebsd.org>

On Thu, May 20, 2021 at 3:06 AM <tuexen@freebsd.org> wrote:
>
> > On 20. May 2021, at 04:05, Xin Long <lucien.xin@gmail.com> wrote:
> >
> > On Wed, May 19, 2021 at 6:24 PM <mleitner@redhat.com> wrote:
> >>
> >> On Tue, May 18, 2021 at 09:19:21PM +0200, Michael Tuexen wrote:
> >>>
> >>>
> >>>> 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.
> >>
> >> With this, Xin, seems we should have a separate timer for the
> >> PROBE_TIMER, other than the heartbeat one.
> >>
> >> Otherwise, converging the two logics into one single timer is not
> >> worth the hassle for saving a timer. For example, we would have to
> >> have it fire on the active transport but to send only the probe.
> >> Also, considering they can and (AFAIU the RFC) should have different
> >> expire timeouts from time to time.
> >>
> >> With a separate timer, we won't have issues converging the
> >> user-selectable heartbeat interval to the recommended 600s
> >> PMTU_RAISE_TIMER, for example.
> >>
> >> Maybe I am missing something. But it seems the hassle for reusing the
> >> timer here is just not worth it. Thoughts?
> > You're right, when I was doing testing, I had to set the hb_interval to 5s.
> > the common value of hb_interval really doesn't fit in the probe_interval.
> > I will try adding a new timer, but at the same time a probe_interval
> > by sysctl/sockopt may be needed, or we can use a value equal to
> > (hb_interval / n) for it?
> Yeah, this is why I did not write a socket API section for RFC 8899. I think
> when implementing it, one will find some parameters which can or should
> be controlled by the application. So I guess there will be more than this
> one.
>
> Timo (CCed) is working on some algorithmic explorations, since RFC 8899, gives
> you some freedom. Right now, his work is done in a simulation environment, but
> once that is finished and he came to some conclusions, we will implement this.
>
> So what about:
>
> * Try to implement PLPMTUD and figure out what you need as user controllable
>   parameters.
> * Bring this up for discussion and we can agree on them and also on how
>   to control them via socket options.
> * Then you get the code into the Linux tree.
>
> That way we would know what parameters are really needed in an implementation
> and we would have a common interface.
Makes sense.

>
> Does that make sense to you and sounds like an acceptable plan?
That sounds a good plan, :-)

Thanks.

>
> Best regards
> Michael
> >
> >>
> >> Best,
> >> Marcelo
> >>
> >>>
> >>> Best regards
> >>> Michael
> >>>>
> >>>>>
> >>>>> Best regards
> >>>>> Michael
> >>>>>>
> >>>>>> Thanks.
> >>>>>
> >>>
> >>
>

  reply	other threads:[~2021-05-20 15:13 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
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 [this message]
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

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=CADvbK_eBZo3u90ZXBQuVBVov6V26580yXcXH-HZSFsgGU0OT7w@mail.gmail.com \
    --to=lucien.xin@gmail.com \
    --cc=linux-sctp@vger.kernel.org \
    --cc=mleitner@redhat.com \
    --cc=timo.voelker@fh-muenster.de \
    --cc=tuexen@freebsd.org \
    --subject='Re: add SPP_PLPMTUD_ENABLE/DISABLE flag for spp_flags' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).