[sctp-dev] Socket Option SCTP_MAXSEG

[Amit Bhayani]

Hi Chris,

Thanks for your response. My comments in-line

On Thu, May 26, 2016 at 5:10 PM, Chris Hegarty <chris.hegarty at oracle.com>
wrote:

>
> > On 26 May 2016, at 05:19, Amit Bhayani <amit.bhayani at gmail.com> wrote:
> >
> > Thanks Chris,
> >
> > Is there way to set this at OS level?
>
> Looking at the documentation I don’t see any way to do this at the system
> level. Someone on the lksctp mailing list [1] [2] might know better.
>

Let me ask same in lksctp mailing list too.

>
> > The provider is not accepting any packets greater that 1420 Bytes
>
> This seems strange, the SCTP documentation [3] seems at odds with this:
>
>   "An SCTP receiver MUST be able to receive a minimum of 1500 bytes in
>    one SCTP packet.  This means that an SCTP endpoint MUST NOT indicate
>    less than 1500 bytes in its initial a_rwnd sent in the INIT or INIT
>    ACK."
>
> I assume you are trying to set SCTP_MAXSEG as a workaround to the
> issue ( on the receiver side ), rather than attempting to resolve it there?
>

Indeed strange. Well the point is not to control the SCTP packet size but
full size of IP packet. I mean in single IP packet there can be multiple
SCTP packets. I realized that there is VPN between server and client and I
believe this VPN is not taking IP packets greater than 1420 Bytes.

>
> > and lksctp keeps doing re-transmission which obviously keeps failing. An
> finally the  link goes down (Abort)
>
> So this looks like a native issue on the receiver side to me, but I do
> understand your request for SCTP_MAXSEG support at the Java
> level. Have you confirmed, through a native app, that this resolves
> the issue you are seeing?
>
> Now I wonder if I should really try to control the SCTP_MAXSEG or Path
MTU. Is there way to hardcode Path MTU in lksctp?


> I think it would be really useful to bring this up on the lksctp mailing
> list [2].  If you do, can you please include me. I am interested in the
> outcome.
>
> Sure thing. Opening new thread there.

> >
> > Thanks and Regards,
> > Amit.
>
> -Chris.
>
> [1] linux-sctp at vger.kernel.org
> [2] http://lksctp.sourceforge.net
> [3] https://tools.ietf.org/html/rfc4960#section-6
>
> > On Thu, May 5, 2016 at 7:28 PM, Chris Hegarty <chris.hegarty at oracle.com>
> wrote:
> >
> > On 5 May 2016, at 12:50, Amit Bhayani <amit.bhayani at gmail.com> wrote:
> >
> > > Hi Guys,
> > >
> > > I am using lksctp with JDK 7 on top. I was looking for
> SctpScoketOption to set SCTP_MAXSEG, but didn't find it available.
> >
> > This option is currently not supported. There is an issue tracking adding
> > additional options:
> >   https://bugs.openjdk.java.net/browse/JDK-8146626
> >
> > -Chris.
> >
>
>
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