Re: [reSIProcate] Mapping SipMessage to TransactionState

[Alan Hawrylyshen <alan@xxxxxxxxxx>]

On 17-Sep-05, at 01:45 , Sandeep Sharma wrote:

> Hi,
>
> I figured a way to solve the transaction id mapping issue. I  
> changed the
> code in BranchParameter to call getCryptoRandomHex() instead of
> getRandomHex() and also changed the calls in Helper.cxx for computing
> callid and tag to use cryptorandom, and saw the asserts disappear.
>
> What I concluded is that you cannot guarantee unique transaction ids
> using random(), but using the openssl RAND functions is much better in
> that regard. Any comments?


Yes, you will get more entropy, but at the expense of your entropy  
pool. When getCryptoRandom runs out of entropy, it will typically  
wait for more, assuring that you get high entropy randomness. This  
will cause problems in high performance systems as the stack will  
block waiting for more entropy. If you happen to have an atomic or  
reliable high-entropy source (most of us do not) your approach is  
mathematically better. On fast, high volume systems using crypto  
random can be a real problem. I've seen order of magnitude slow-downs  
and this is why we were using the other random interface.

> Earlier I would see assert in 10 minutes consistently, now I have run
> fore more than an hour and have not seen the assert. (duplicate
> transaction id)

On what platform are you seeing this? (OS, Processor Type and Speed)  
I have done a LARGE amount of testing with resiprocate and not had a  
self-generated tid collision in many billions of messages.

> Question: Is it common to tinker with the timer values in os/ 
> Timers.cxx?
> Basically I doubled all the timers since I was seeing timeout (408)
> getting generated under load and the response would arrive after the
> timeout. So the timer for SUBSCRIBE now is 64 seconds instead of  
> 32. Can
> these be changed from the application code (at run time) or they  
> have to
> be hardcoded in the Timers.cxx file?


Common to tinker? Not sure, but you can just set them. They are  
global variables (ugh) and they are referenced as the timers are  
created so changing them will affect only subsequent transactions.


Alan Hawrylyshen
reSIProcate Project Administrator
http://sipfoundry.org/reSIProcate/
a l a n a t j a s o m i d o t c o m