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
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>
>