A query regarding SCTP congestion control

Sun Jan 25 03:14:26 PST 2009

Hi Sazzad,

what is the value of the from field i the structure sctp_cwnd_log?

Best reards
Michael

On Jan 23, 2009, at 1:16 AM, Rahman, Md Sazzadur wrote:

> Hi Randall,
>
> Thanks for your suggestions. I could collect congestion window data  
> from SCTP sender using SCTP_LOCAL_TRACE_BUF on FreeBSD7.1 kernel  
> using the tools you provided (dump_apple_log.c, prtcwndlog.c etc.).  
> Now, in the log, I found that tsn (Transmission Sequence Number)  
> never changes and remains fixed which is not supposed to happen, I  
> believe. Do you have any idea what could go wrong?
>
>
> For example, in the log below, tsn is always 28170ae0.
>
> //-From Log-------------------------------
> 2.162922  1543161849724545 Network:0xc463aaf0 cwnd:13063 flight: 
> 12762 pq:f4f72484 Log from a Send tsn:28170ae0 (sendcnt:191,strcnt: 
> 191)
> 2.200947  1543161849753090 Network:0xc463aaf0 cwnd:13063 flight: 
> 14180 pq:f4f72484 Log from a Send tsn:28170ae0 (sendcnt:191,strcnt: 
> 191)
> ..............
> .............
> 2592.987776  1543168861292865 Network:0xc463aaf0 cwnd:13063 flight: 
> 14180 pq:f4f72484 Log from a Send tsn:28170ae0 (sendcnt:191,strcnt: 
> 191)
>
> //----------------------------------------------
>
> Steps I have followed:
>
> //----------------------------------------------
> 1. Recompiled FreeBSD7.1 kernel by enabling SCTP_LOCAL_TRACE_BUF
> 	#define SCTP_LOCAL_TRACE_BUF 1
>
> 2.	Enalble desired loging using sysctl;
> 	Sysctl -w "net.inet.sctp.log_level=0x00000004
>
> 3.	Run application that sends SCTP data to the network
>
> 4.	./Dump_apple_log > data.txt
>
> 5.	./Prtcwdlog -l data.txt> cwnd.txt
> //----------------------------------------------
>
> I have attached the log file herewith this mail.
>
> It would be great if you can give me any hint to resolve this issue.
>
>
>
> Thanks,
> Sazzad
>
> -----Original Message-----
> From: Randy Stewart [mailto:randall at lakerest.net]
> Sent: Thursday, August 28, 2008 6:39 AM
> To: sazzadur rahman
> Cc: freebsd-net; Atiquzzaman, Mohammed; Rahman, Md Sazzadur
> Subject: Re: A query regarding SCTP congestion control
>
> 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 <rrs at cisco.com>
>> 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
>>>>
>>>> _______________________________________________ freebsd-net at freebsd.orgmailing
>>>> list
>>>> http://lists.freebsd.org/mailman/listinfo/freebsd-net To
>>>> unsubscribe,
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>>>>
>>>>
>>>
>>> --
>>> Randall Stewart
>>> NSSTG - Cisco Systems Inc.
>>> 803-345-0369 <or> 803-317-4952 (cell)
>>>
>>> _______________________________________________
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>
> -----
> Randall Stewart
> randall at lakerest.net
>
>
>
>
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