Date: Thu, 28 Aug 2008 07:38:54 -0400 From: Randy Stewart <randall@lakerest.net> To: sazzadur rahman <rahman.sazzadur@gmail.com> Cc: freebsd-net <freebsd-net@freebsd.org>, atiq@ou.edu, "Rahman, Md Sazzadur" <sazzad@ou.edu> Subject: Re: A query regarding SCTP congestion control Message-ID: <0ED8CE06-588C-4A04-BE8D-CCD8DA2C945D@lakerest.net> In-Reply-To: <82bdb5ec0807021137m7819153rbc0631ab6f310d0e@mail.gmail.com> References: <7059EA19D7837E44A3BA7DAB464944B37FDA715193@XMAIL5.sooner.net.ou.edu> <48060748.1090807@cisco.com> <82bdb5ec0807021137m7819153rbc0631ab6f310d0e@mail.gmail.com>
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Remember a lot has changed between the book and now. 1) The initial window is now different 2) labc variable may influence how the cwnd responds are just 2 off the top of my head. You also may want to use a local trace buffer (as I mentioned earlier) =20= since turning KTR on really really skew's things time wise.. its a resource =20= pig. We added the local trace buffer for this very reason. Contact me directly if you need guidance on this. Also you may want to pick up the latest update that I just put up on www.sctp.org It gets the 7.0 stack current to 8.0's code.. .and there have been at least 1 CC fix in the last few months.. R On Jul 2, 2008, at 2:37 PM, sazzadur rahman wrote: > Hello, > I need to get SCTP congestion window data for research purpose. I =20 > collected > cwnd data from SCTP sender running on FreeBSD 7.0 machine by using KTR > kernel log. After that, I tried to plot cwnd vs. time and generated =20= > graph. > But I am unable to explain the graph and it is very different =20 > compared to > the graph as shown in the book "Stream Control Transmission Protocol > (SCTP)", a reference guide by Randall R. Stewart, page 187 and TCP > congestion window. An typical entry from the log looks like: > > 749199232185105 Net:0xc7703000 at cwnd_event (SACK) cwnd:25140 =20 > flight:0 pq:0 > atpc:72 needpc:235 (tsn:0,sendcnt:191,strcnt:191) > > I have used 749199232185105 in x axis as time and cwnd:25140 in y =20 > axis. I > have attached the image file of the graph herewith this mail. > >> =46rom the log, I found that cwnd varies very frequently accross =20 >> time. Does > anyone have any idea regarding this issue? > Please let me know if you have any questions further. > > Thanks in advance. > > Best regards, > Md Sazzadur Rahman > Graduate Student, > School of Computer Science, > University of Oklahoma, > Norman, Oklahoma, USA > > Steps for getting kernel log > > ------------------------------------------ > > 1. Add options: > > options KTR > > options KTR_ENTRIES=3D65536 > > options KTR_MASK=3DKTR_SUBSYS > > > 2. Recompile kernel > > config CUSTOM_KERNEL_9_6 > > cd ../compile/ CUSTOM_KERNEL_9_6 > > make cleandepend;make depend; > > make all install > > 3. Tried to enable trace point by: > > Sysctl -w "net.inet.sctp.log_level=3D0x00000004" > > 4. run SCTP sender. > > 5. pull out data: > > Ktrdump =96q =96t =96o file_name > > Prtcwndlog =96l filename > cwnd.txt > > --------------------------------------------------- > > > > On Wed, Apr 16, 2008 at 9:03 AM, Randall Stewart <rrs@cisco.com> =20 > wrote: > >> Rahman, Md Sazzadur wrote: >> >>> Hi, I would like to get the values of SCTP congestion control >>> algorithm variables (cwnd, ssthresh, flightsize and pba) from any >>> SCTP based application in runtime for research purpose. Does any API >>> exist in SCTP for that? Do I need to dig the SCTP code in kernel to >>> get the values? >>> >> >> There is a socket option to get the cwnd. >> >> However, I think what you really want is some of the researchish >> tracing stuff that SCTP provides. >> >> You can actually get a real time trace of the cwnd/flight etc via the >> various logging functions. >> >> You basically must compile this as an option.. have to go look >> at the options.. >> >> And then you can either use ktrace (which I don't recommend since >> it turns on to much overhead in the kernel) or you can >> use SCTP_LOCAL_TRACE_BUF >> >> This will put it into a piece of memory only for SCTP and >> not turn on all the other ktrace points. >> >> After you enable the logging in your compile you must turn >> on the logging level.. >> >> SCTP_CWND_LOGGING_ENABLE >> >> woudl be my recommendation. >> >> It gives you a real time up/down growth of the cwnd/flight/rwnd >> >> I think I wrote a "how to" somewhere.. let me go look.. >> >> R >> >> >> >>> I will appreciate any help in this regard. >>> >>> Best Regards, Md Sazzadur Rahman Graduate Student, School of =20 >>> Computer >>> Science, University of Oklahoma, Norman, Oklahoma, USA >>> >>> _______________________________________________ = freebsd-net@freebsd.orgmailing=20 >>> list >>> http://lists.freebsd.org/mailman/listinfo/freebsd-net To =20 >>> unsubscribe, >>> send any mail to "freebsd-net-unsubscribe@freebsd.org" >>> >>> >> >> -- >> Randall Stewart >> NSSTG - Cisco Systems Inc. >> 803-345-0369 <or> 803-317-4952 (cell) >> >> _______________________________________________ >> freebsd-net@freebsd.org mailing list >> http://lists.freebsd.org/mailman/listinfo/freebsd-net >> To unsubscribe, send any mail to "freebsd-net-=20 >> unsubscribe@freebsd.org" >> > _______________________________________________ > 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" ----- Randall Stewart randall@lakerest.net
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