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)
since
turning KTR on really really skew's things time wise.. its a resource
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
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
graph.
But I am unable to explain the graph and it is very different
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
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
axis. I
have attached the image file of the graph herewith this mail.
From the log, I found that cwnd varies very frequently accross
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=65536
options KTR_MASK=KTR_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=0x00000004"
4. run SCTP sender.
5. pull out data:
Ktrdump –q –t –o file_name
Prtcwndlog –l filename > cwnd.txt
---------------------------------------------------
On Wed, Apr 16, 2008 at 9:03 AM, Randall Stewart <[EMAIL PROTECTED]>
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
Computer
Science, University of Oklahoma, Norman, Oklahoma, USA
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NSSTG - Cisco Systems Inc.
803-345-0369 <or> 803-317-4952 (cell)
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