Date: Mon, 29 Dec 2008 14:09:12 +0100 From: =?ISO-8859-1?Q?Michael_T=FCxen?= <Michael.Tuexen@lurchi.franken.de> To: <ajassal.ext@orange-ftgroup.com> <ajassal.ext@orange-ftgroup.com> Cc: freebsd-net@freebsd.org, khadija.daoud@orange-ftgroup.com Subject: Re: SCTP : problems in sending ASCONF chunks Message-ID: <2C67145C-C26B-4666-B7A5-6EC1C4ABA1E5@lurchi.franken.de> In-Reply-To: <3418F3471F1CA4409901547349FFAE2E0910679F@ftrdmel2> References: <3418F3471F1CA4409901547349FFAE2E0910679F@ftrdmel2>
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Hi, are both machines (T and you PC) running FreeBSD? Best regards Michael On Dec 29, 2008, at 12:33 PM, <ajassal.ext@orange-ftgroup.com> <ajassal.ext@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 > > _______________________________________________ > freebsd-net@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-net > To unsubscribe, send any mail to "freebsd-net-unsubscribe@freebsd.org" >
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