Hi Aman,
comments in-line.
Best regards
Michael
On Dec 29, 2008, at 6:12 PM, <ajassal....@orange-ftgroup.com> <ajassal....@orange-ftgroup.com
> wrote:
Hello M.Tüxen,
I performed a quick test and at the INIT/INIT-ACK exchange, I
noticed the following :
- In the INIT chunk, the Supported Extensions Parameter field
indicates that ASCONF, ASCONF-ACK, FORWARD-TSN, PKTDROP,
STREAM_RESET and AUTH are supported
OK. That is the FreeBSD box.
- In the INIT-ACK chunk, there is no field indicating that any of
the chunks listed above are supported...
So it does not support ASCONF and AUTH.
At least on a Fedora 9 box you need to enable ADD-IP by setting the
sysctl variable
net.sctp.addip_enable
to 1.
To enable SCTP-AUTH you need to set the sysctl variable
net.sctp.auth_enable
to 1.
I'm not sure whether the Linux box support SCTP-AUTH or not... So the
second step might not work. If this is the case you can disable the
AUTH requirement for ASCONF chunks by setting on the FreeBSD box the
sysctl
variable
net.inet.sctp.asconf_auth_nochk
to 1
Let me know if this works...
I didn't think about looking in this before >_<
Since there is no indication given to my PC, perhaps my PC assumes
that T doesn't support ASCONF, ASCONF-ACK, FORWARD-TSN, PKTDROP,
STREAM_RESET and AUTH.
Correct. At least some of the extension are not enabled.
Could it be that, because it doesn't see any Supported Extensions
Parameter field in the INIT-ACK, my PC doesn't try to send any
ASCONF chunk ?? Do we absolutely need to have the ASCONF, ASCONF-ACK
and AUTH parameters in the Supported Extensions Parameter, in both
the INIT and the INIT-ACK chunks, to have the possibility of sending
an ASCONF chunk ?
In principle, yes! You can work around the AUTH chunks as indicated
above, but this
violates the specification and is only supported to interwork with
legacy implementations.
Kind regards
Aman Jassal
-----Message d'origine-----
De : Michael Tüxen [mailto:michael.tue...@lurchi.franken.de]
Envoyé : lundi 29 décembre 2008 16:49
À : zze-Abac JASSAL A ext RD-RESA-ISS
Cc : freebsd-net@freebsd.org; DAOUD TRIKI Khadija RD-RESA-ISS
Objet : Re: SCTP : problems in sending ASCONF chunks
Hi Aman,
I'm not that familiar with the Linux box configuration. If you look
at the INIT/INIT-ACK exchange, does the Linux box support ASCONF and
the SCTP-AUTH extension? Both are required...
Best regards
Michael
On Dec 29, 2008, at 2:36 PM, <ajassal....@orange-ftgroup.com> <ajassal....@orange-ftgroup.com
> wrote:
Hello M.Tüxen,
No, only the PC is running under FreeBSD 7.0. T is running under
Linux
(kernel version is 2.6.21 and the distribution used is Fedora Core
7).
SCTP is running on T thanks to the lksctp implementation, we loaded
the sctp module on it and made the necessary configurations so that
it
is loaded at boot time.
Also, I enable net.sctp.addip_enable=1 on T, just in case, I'm not
exactly sure if it has an effect on my tests.
Kind regards
Aman Jassal
-----Message d'origine-----
De : Michael Tüxen [mailto:michael.tue...@lurchi.franken.de]
Envoyé : lundi 29 décembre 2008 14:09
À : zze-Abac JASSAL A ext RD-RESA-ISS
Cc : freebsd-net@freebsd.org; DAOUD TRIKI Khadija RD-RESA-ISS Objet :
Re: SCTP : problems in sending ASCONF chunks
Hi,
are both machines (T and you PC) running FreeBSD?
Best regards
Michael
On Dec 29, 2008, at 12:33 PM, <ajassal....@orange-ftgroup.com>
<ajassal....@orange-ftgroup.com
wrote:
Hi all,
I have been working with SCTP and more specifically with the
mobility
features of SCTP at my work. Basically, I have been trying to use
SCTP to perform handover tests between 2 separate Wifi networks. I
use
IPv6
for all my tests.
I have a local LAN (wired-network), on which I have 3 machines, one
of them is the machine I use to communicate with for the tests (I'll
call it T to make things simple), and the other two are used as Wifi
Access Points (say Wifi1 and Wifi2 respectively). Since I work with
IPv6, I set up both Access Points to send Router Advertisement
messages periodically (minimum of 3 seconds, maximum of 4 seconds).
That way I can have automatic address reconfiguration when I connect
to either of the access points.
The aim of my tests is to use a PC, connect to Wifi1 (for example),
launch an SCTP association with T (T sends data to my PC), and then
perform a handover on Wifi2. I do make address reconfiguration
during
the handover process. The important point is that I work with only
ONE address on my network interface. Before I start my tests, I set
the following sysctl parameters :
# sysctl -w net.inet.sctp.mobility_base=1 # sysctl -w
net.inet.sctp.mobility_fasthandoff=1
# sysctl -w net.inet.sctp.debug=0x00f301f0 (that is to dump
messages in /var/log/messages)
net.inet.sctp.auto_asconf is set to 1 by default.
I use FreeBSD 7.0 on my PC, I don't know if that is extremely useful
but I'm trying to be thorough. This is the script I use to perform
handover
:
ifconfig rum0 inet6 <my old address> delete ifconfig rum0 ssid <the
target access point> route del -inet6 default <my old gateway> rtsol
rum0
If I'm not mistaken, the PC should have sent an ASCONF chunk to
perform dynamic address reconfiguration. However what I observed is
that nothing happens. No ASCONF chunks are sent, and therefore, T
doesn't ever know that it should send data on the PC's newly
acquired
address.
I tried to investigate the problem myself, by adding some debug logs
in the sctp source code (to see which functions are called during
the
handover process), and it seems as if the kernel doesn't ever add an
ASCONF chunk to send in its queue... But that's just my
understanding
of the problem...
I looked up in the CVS repository for answers, and to see the
various
changes that were gradually brought on the code. There, I noticed
that on the revision dating 24th July 2007, changes were made for
dynamic address reconfiguration : "Change behaviour so that when the
last address is deleted (auto-asconf on a boudall endpoint) no
action
is taken until an address is added ; at that time an ASCONF
add+delete is sent (if the asoc is still up)"
In my humble opinion, this is exactly the case that corresponds to
my
handover scenario. But I just haven't been able to successfully
perform it because I don't seem to send any ASCONF chunk. I'm
struggling to understand why I do not see any ASCONF chunk sent.
If it can help, I'm also attaching links to the kind of debug logs I
got when performing a handover test. This is the kind of debug logs
that I got :
http://www.divshare.com/download/6200509-560
This is another debug logfile, but with my own debug logs added in
the sctp source code :
http://www.divshare.com/download/6200504-2e9
Many thanks for your work, and I hope someone will be able to help
and shed some light on this problem :-)
Aman Jassal
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