[asterisk-r2] Overlap dialling with MFC/R2

[Vinícius Fontes]

Hello.

Considering the following setup: 

Legacy PBX --(ISDN)--> Asterisk --(MFC/R2)--> PSTN


When a user dials out, Asterisk receive overlap digits, matches them to an extension and dial the PSTN, completing the call. So far so good.

The issue I'm trying to solve (or at least improve) is the call takes much longer to complete than the users were used to before having Asterisk between the PBX and the PSTN. It happens because the digits are sent to the PSTN only after the extension is matched in the dialplan, and dialing on MFC/R2 takes a few seconds.

Here's the console log. Notice how it takes 6 seconds from the instant the user starts dialing to the instant the dialed number starts to ring. First 3 seconds is the user manually dialing plus Asterisk absolute timeout. Next 3 seconds are the time Asterisk takes to dial the number to the PSTN and the call be accepted.


[Apr 26 10:57:13]     -- Accepting overlap call from '7416' to '<unspecified>' on channel 0/1, span 2
[Apr 26 10:57:13]     -- Starting simple switch on 'DAHDI/32-1'
            
             *** User finished dialing + Asterisk absolute timeout ***

[Apr 26 10:57:16]     -- Executing [0145333114657 at pbx:1] Answer("DAHDI/33-1", "") in new stack
[Apr 26 10:57:16]     -- Executing [0145333114657 at pbx:2] Dial("DAHDI/33-1", "DAHDI/g1/0145333114657") in new stack
[Apr 26 10:57:16]     -- Called g1/0145333114657

             *** Asterisk starts dialing to the PSTN ***

[Apr 26 10:57:19] MFC/R2 call has been accepted on forward channel 1
[Apr 26 10:57:19]     -- DAHDI/1-1 is ringing

             *** Dialed number finally rings ***

So my question is: is there a way to fully overlap the digits from the user's phone on the PBX (ISDN) to the PSTN (MFC/R2), eliminating the need to wait for an extension to be matched? I already have overlapdial=yes in both spans, but that didn't made it. Also googled for it, even searched this list archives but found nothing.


chan_dahdi.conf:

[channels]

signalling=mfcr2
mfcr2_variant=br
mfcr2_get_ani_first=no
mfcr2_max_ani=20
mfcr2_max_dnis=4
mfcr2_category=national_subscriber
mfcr2_logdir=span1
mfcr2_call_files=no
mfcr2_logging=all
mfcr2_mfback_timeout=-1
mfcr2_metering_pulse_timeout=-1
mfcr2_allow_collect_calls=yes
mfcr2_double_answer=no
mfcr2_immediate_accept=no
mfcr2_forced_release=no
mfcr2_charge_calls=yes
language=pt_BR
echocancel=yes
echocancelwhenbridged=no
callgroup=0
pickupgroup=0
group=1
context=telco
overlapdial=yes
channel => 1-15,17-31

switchtype=euroisdn
pridialplan=unknown
prilocaldialplan=unknown
priindication=outofband
signalling=pri_net
busydetect=yes
busycount=5
language=pt_BR
echocancel=yes
echocancelwhenbridged=no
overlapdial=yes
group=2
context=pbx
channel => 32-46,48-62



extensions.conf:

[telco]
exten => _X.,1,Dial(DAHDI/g2/${EXTEN})

[pbx]
exten => _X.,1,Dial(DAHDI/g1/{$EXTEN})


Sample console: