R: [Serusers] Retransmission problem

Greger V. Teigre greger at teigre.com
Thu Sep 7 09:23:56 CEST 2006


Inline.

Zappasodi Daniele wrote:
>
> Many thanks for the reply, it is very useful but it contains bad news 
> because, if is it possible, it is important for me to preserve the 
> possibility to have the SIP proxy and SIP gateway in the same board.
>
>  
>
> Some other clarification:
>
> 1. I have two ethernet interfaces, if I give different IP address to 
> proxy and gateway, can I leave them on the same hardware?
>
Yes, the trick is to get the listen and alias directives correct in your 
ser.cfg. You can run multiple servers or UAs on the same server, you 
just have to make sure you don't have alias=myip in ser.cfg. This will 
make SER believe messages for another server/UA is to be routed locally.
>
>  
>
> 2. If I correctly understand the transaction creation in SER: SER 
> absorbs the retransmission only if already exists a transaction for 
> the original INVITE and SER creates a new transaction for an INVITE 
> only when is invoked the t_relay.
>
Yes, if not, SER will be transaction stateless and just happily forward 
any message.
>
> Consequently, If a retransmitted INVITE arrives when the elaboration 
> of the original INVITE is still in progress, SER repeats all the 
> elaboration also for the second INVITE.
>
I'm not sure what you mean by "elaboration", but if you mean that the 
script will be executed for retransmitted INVITEs, then yes.
>
> Do you confirm my description?
>
> I have built a function that in heavy load traffic condition could be 
> slow (it does an external query, something similar to an exec) and it 
> is important that I don't invoke it twice for the same INVITE, so I 
> try to use t_newtran to anticipate the transaction creation before 
> invoking this function.
>
> However, as first step, I will remove the t_newtran, 
> t_forward_nonack_uri and I try again.
>
Normally, you should not have to worry about the transaction state, just 
process the INVITE and use t_relay() and let SER handle the 
retransmissions etc. I cannot see that your scenario would require more 
fine-grained control over the transaction state, but then I don't know 
what you are trying to do...
g-)
>
>  
>
> Thanks again.
>
>  
>
>     -----Messaggio originale-----
>     *Da:* Greger V. Teigre [mailto:greger at teigre.com]
>     *Inviato:* mercoledì 6 settembre 2006 9.19
>     *A:* Zappasodi Daniele
>     *Cc:* serusers at lists.iptel.org
>     *Oggetto:* Re: [Serusers] Retransmission problem
>
>     1. DON'T have UA2 and SER on the same server. You are very likely
>     to get problems because SER sees it's own IP address in a message
>     destined for UA2
>     2. Don't use t_newtran and t_forward_nonack_uri unless you know
>     exactly what you do (and probably not then either)
>     3. When having problems like that, use a pretested Getting Started
>     config fil (http://iptel.org/ser/doc/gettingstarted). If you still
>     have the problem, there is something external (like UA2 on same
>     box as SER). Fix it and then compare the logic of your config file
>     with the Getting Started reference config
>     g-)
>
>     Zappasodi Daniele wrote:
>>     Hello, 
>>     I have a big problem with the retransmissions.
>>     In my tests sometimes the retransmission handler doesn't seem to work properly and it resends the INVITE after receiving a final response. 
>>     Moreover it doesn't respect the time-out (instead wait 1 second it resends the packet after few decimal), but this is a minor item.
>>
>>     An example:
>>     INVITE sip:31203
>>     From 32201
>>
>>     	UA1(32201)  ---> SER ---> UA2(31203)	
>>     INVITE 	UA1 ---> SER ---> UA2	
>>     Trying	UA1 <--- SER
>>     183		UA1 <--- SER <--- UA2
>>     480		UA1 <--- SER <--- UA2
>>     ACK	 	UA1 ---> SER ---> UA2	
>>     ...
>>     Other call.
>>
>>     After 0,5 msec SER sends again the first INVITE to UA2:
>>     INVITE 		SER ---> UA2	
>>     183			SER <--- UA2
>>     etc.
>>
>>     In the attached zipped file there are the syslog, the ser config file (only the relevant parts) and the ethereal captures related to this example.
>>
>>
>>     Some additional information:
>>     SER version is 0.9.2, compiled for arm.
>>     In my scenario SER and UA2 are on the same box.
>>     In LAN_capture.cap file there is the message flow between UA1 and SER, in lo_capture.cap between SER and UA2. 
>>
>>     Can someone explain me this behaviour?
>>     Maybe something wrong in my config file? Note that I use t_lookup_request, t_newtran, t_forward_nonack_uri in order to recognize retransmitted INVITE, could it be here the problem?
>>
>>     thanks
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>
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