[Serusers] MSRTC DLL Bug with SER

[Jonathan]

Hello Andrew,

It seems im also being troubled by the problem you have perfectly put
into words unlike the one in my email. ^_^

I just want to ask though, because when i use UDP as the protocol in
my rtc profile, this problem does not occur and communication flow
between user A and B goes smoothly.

Do you think there is an explanation behind that? Why would SER/RTCDLL
combination work when it's under UDP and not when using TCP?

I really have no idea, just observations.

Any comments and/or ideas regarding this issue would greatly help.

Thanks alot in advance.

- Jonathan -


On Wed, 18 Aug 2004 09:46:05 +1000, Andrew Mee
<andrew at healthshare.net.au> wrote:
> After much more discovery we have figured out what the issue is with the
> MS RTC 1.2 and SER.
> 
> This isn't so much as a bug with SER but with MS RTC 1.2, it is caused
> by MS RTC sending incorrect Request-URI in the headers. This only occurs
> in request routed mode from the callee end.
> 
> Take the example:
> RTC Client A            SIP Server           RTC Client B
> -----INVITE-------------->
> <----100 Trying-----------
>                              -----INVITE---------------->
>                              <----100 Trying-------------
> <----180 Ringing----------   <----180 Ringing------------
> <----200 OK w/ INVITE-----   <----200 OK w/ INVITE-------
> -----ACK----------------->   -----ACK------------------->
> 
> All is fine at this point, however now lets send a message from A to B:
> RTC Client A            SIP Server           RTC Client B
> ----MESSAGE b at server---->    ----MESSAGE b at server---->
> <----200 OK -------------   <----200 OK --------------
> 
> All is still fine, However if we send a message back from B to A:
> RTC Client A            SIP Server           RTC Client B
>                              <----MESSAGE b at server----
>                              -----MESSAGE b at server---->
>                              <----481 Call Leg/T DNE---
> This is obvious because the SER server sees this message as needing to
> go back to B when it should be forwarded to A as per "8.1.1.1
> Request-URI" of the rfc (as far as my understanding on this). This issue
> occurs with BYE commands and possibly other types of commands.
> 
> I might add the To: and From: header fields are correct.
> 
> Solution to this problem could (or is there an existing way) a
> module/control could be created that checks if the To: field doesn't
> equal the request-uri that the request-uri be changed to the information
> in the To: field?
> 
> Yes I agree that while this is a MS RTC problem, I figure this is going
> to be a better/quicker short term solution. I have not tested if this
> problem exists with other SIP servers.
> 
> I can send some ngrep logs if anyone likes?
> 
> --
> Andrew Mee
> 
> 
> 
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