[asterisk-users] ZAP inbound/outbound connection taking too long

[Stephen Bosch]

Gordon Henderson wrote:
> On Fri, 1 Jun 2007, Gavin Henry wrote:
> 
>> Dear all,
>>
>> I think this is common, or at least how it is supposed to be, but
>> whening dialing over a ZAP channel, it's taking around 5~ seconds to
>> ring on the over end, likewise inbound.
>>
>> This is just with a normal Dial command.
> 
> It's "normal" for an analogue Zap channel.

Not exactly. Explanation follows.

> Asterisk has to "sieze" the line (after a basic check to make sure the
> channel is free), that may entail a delay of a second or so while it
> makes sure there there is a dial-tone (actually, I'm not sure it waits
> for a dial-tone)

Zap does not do dial tone detection.

>, then it sends the digits out via DTMF - that might
> take a second or 2 for a long number - then it's up to the PSTN switch
> at the other end to connect the call - depending on the technology, this
> might take several seconds.

This depends on multiple factors -- you can tweak your DTMF output to
speed up dialing. You'll have to use some trial and error to confirm
that the PSTN is receiving the DTMF properly.

I have another theory, though -- are you dialing from a SIP extension?

The biggest delay, in my experience, is the time it takes for the SIP
extension to recognize that a full number has been dialed. It doesn't
pass the number to Asterisk until it has interpreted it as a complete
number.

Many SIP devices let you configure this behaviour.

You should also compare how long it takes to complete a call from an
analog extension that is directly on the line, so that you have a
baseline for reference.

You will also find that many key systems introduce delay like this. In
any case, this is all tweakable to make it faster.

-Stephen