T310 timer and PROGRESS

[Christian Groves]

G'Day Paul,

I had a look at Q.931 as the precurser to H.225 to see what the 
intention was there. Whilst not in the core specification there was a 
description of the behaviour in an annex described Private Network 
interconnection.


          "M.6.3.1.3    In-band information provided to the physical
          PINX at the originating interface

Any progress indications shall be conveyed towards the physical PINX at 
the originating interface.

On receipt of the Progress description No. 1 or No. 8 in the PROGRESS or 
ALERTING message, the physical PINX at the originating interface shall 
switch through in the backward direction to the allocated B-channel in 
order to enable transfer of in-band tones/information, and stop timer 
T310, if running."


          M.6.3.2.3    In-band information provided by the physical PINX
          at the destination interface

During call establishment, after the first message received in response 
to the SETUP message, on receipt of a Progress indicator information 
element with a Progress description No. 1 or No. 8 in the PROGRESS or 
ALERTING message, the public network shall switch through in the 
backward direction to the allocated B channel in order to enable in-band 
tones/information provided from the physical PINX at the destination 
interface to the calling user, stop timer T310, if running, and if 
progress description No. 1 or No. 8 was received in the PROGRESS message 
while T310 was running, restart timer T310.

The public network shall transfer the Progress indicator information 
element towards the preceding PINX."


Cheers, Christian

Paul E. Jones wrote:

> Experts,
>
>  
>
> Recently, I asked what should happen when an endpoint receives a 
> PROGRESS message indicating that there are in-band tones and 
> announcements.  Should the T310 timer be stopped?  H.225.0 seems to be 
> silent on this, but it would certainly seem that it should be stopped.
>
>  
>
> Should we stop the timer or should the timer continue to run?  It will 
> expire in short order (assuming a default value), which suggests the 
> timer ought to be terminated and T301 started.
>
>  
>
> I would appreciate your input on this.
>
>  
>
> Paul
>
>  
>