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Re: [SCTP-Discussion] withsctp and FTP: no IPv4 Address Parameters on data connection


Chronological Thread 
  • From: Michael Tuexen <Michael.Tuexen AT micmac.franken.de>
  • To: daniel migault <mglt.public AT gmail.com>
  • Cc: discussion AT sctp.de
  • Subject: Re: [SCTP-Discussion] withsctp and FTP: no IPv4 Address Parameters on data connection
  • Date: Mon, 2 Jan 2012 23:04:26 +0100
  • List-archive: <http://lists.franken.de/pipermail/sctp-discussion>
  • List-id: SCTP Discussions <sctp-discussion.sctp.de>

On Jan 2, 2012, at 10:55 PM, daniel migault wrote:

> Hi Michael,
>
> Thank you for your feed back. I will post it on the LKSTCP mailing list. I
> would have expect the two SCTP associations to be independent with
> different port and different sockets. I don't really see why they behave
> differently. But thank you, I will think about it a bit more.
The control connection does not care about the local address. For the data
connections, this is different.
The addresses/port numbers are negotiated via the control connection. So I
would guess the socket of
the data connection is bound to the address/port negotiated via the control
connection. Since FTP
does not handle multi-homing, it will only use one address, I guess.

Best regards
Michael
>
> Regards,
> Daniel
>
> On Mon, Jan 2, 2012 at 9:29 PM, Michael Tuexen
> <Michael.Tuexen AT micmac.franken.de>
> wrote:
> On Jan 2, 2012, at 7:48 PM, daniel migault wrote:
>
> > Hi,
> >
> > We test SCTP multihoming with FTP. "withsctp tnftpd -4D" starts the
> > server, and "withsctp ftp" starts the client with its two network
> > interfaces. FTP initiates first a SCTP association for the control
> > connection on port 21, followed by a second SCTP association for the data
> > connection on port 20.
> It looks like you are using Linux specific stuff in combination with the
> Linux kernel
> implementation. Is that right?
>
> This list supports the sctplib user land SCTP implementation. So you might
> want to
> ask this question on the LKSCTP mailing list.
> >
> > When establishing its SCTP association for the control connection the
> > INIT has the two IPv4 address parameter payloads. This not the case for
> > the second SCTP association where the client does not announce any IPv4
> > address parameter for the data connection.
> So I guess that the socket is bound to a specific address. Then you
> wouldn't see any address in the INIT chunk.
> So you might need to change the ftp code...
> >
> > We would like the second SCTP association to have two IPv4 address
> > parameters so to measure multihoming during the data transfer. We are
> > running "withsctp" on Fedora for the client and Debian for the server.
> >
> > Has anyone any clue how to force the second SCTP association to have two
> > IPv4 address parameters? Are there any specific values to be set with
> > sysctl?
> >
> > Regards,
> >
> > Daniel
> > _______________________________________________
> > sctp-discussion mailing list
> > sctp-discussion AT sctp.de
> > http://www.sctp.de/mailman/listinfo/sctp-discussion
>
>





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