[Freeswitch-users] Exchange 2007 UM - DTMF problem

[Steve Underwood]

Hi,

Brian West wrote:
> So if you can tell me where this is wrong as per 2833 and the  
> clarification via 4733 ?
>
> rfc4733 obsoletes  rfc2833 and says this:
>     The special duration value of zero is reserved to indicate that the
>     event lasts "forever", i.e., is a state and is considered to be
>     effective until updated.  A sender MUST NOT transmit a zero duration
>     for events other than those defined as states.  The receiver SHOULD
>     ignore an event report with zero duration if the event is not a
>     state.
> /b
> PS: http://www.rfc-editor.org/rfc/rfc4733.txt
>   
As well as that definition in RFC4733, they also have an example working 
in the way the text describes. They send DTMF with a packet rate of one 
every 50ms. The first packet of the DTMF sequence contains a duration of 
400.

What does FS actually do when a sequence starts at 0? Does it just drop 
the first packet, or the whole sequence? If it just drops the first 
packet, and the far end cares, that's seriously broken on their part. It 
means a single lost packet screws up the whole sequence. Not good. If FS 
drops the whole sequence, that might be a little too aggressive.

Some will argue that a gateway should be totally transparent in these 
situations, but total transparency is only workable in simplistic cases.

In the end, if MS are doing this you can be sure it will not be fixed, 
and must be tolerated.

Regards,
Steve