asterisk users - Jul 2005 - Random Behavior on Trunk Lines with TDM Card

We have implemented * in one of our branch offices and recently ran up
against a very strange issue. On random occasions, when we would dial
out using our trunk lines, we would get a message stating "you do not
have to dial a 1 or 0 when calling this number" even if we didn't dial
a
1 or 0 in the dial sequence at all. After much troubleshooting, we found
users with similar issues that simply put a wait (w$EXTEN) in the dial
sequence and fixed the problems. We did the same and it automagically
fixed itself. This is great, of course, but I was wondering if someone
out there could give me a more detailed explanation of why this works
and why you have to implement this trick with some telecom providers and
not with others. Verison provides our trunks at our branch office, but
this issue has never arisen at our home office where we have SBC. We are
running * v1.0 with a Digium 4 port FXO TDM card.

 

Thanks,

Heath Bowlin

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On Wednesday 27 July 2005 11:51, Heath Bowlin wrote:
> We have implemented * in one of our branch offices and recently ran up
> against a very strange issue. On random occasions, when we would dial
> out using our trunk lines, we would get a message stating "you do not
> have to dial a 1 or 0 when calling this number" even if we didn't
dial a
> 1 or 0 in the dial sequence at all. After much troubleshooting, we found
> users with similar issues that simply put a wait (w$EXTEN) in the dial
> sequence and fixed the problems. We did the same and it automagically
> fixed itself. This is great, of course, but I was wondering if someone
> out there could give me a more detailed explanation of why this works
> and why you have to implement this trick with some telecom providers and
> not with others. Verison provides our trunks at our branch office, but
> this issue has never arisen at our home office where we have SBC. We are
> running * v1.0 with a Digium 4 port FXO TDM card.
I am willing to bet that you dialled a number with '1' or '0' as
the second or
even third digit of the full number, and that your LEC is either overloaded 
and/or running older, slower technology.  

What I believe is happenning is that Asterisk is picking up the line and 
dialing, but the LEC switch isn't fast enough and only begins
"listening" for
DTMF after Asterisk's already played the first few digits.  This is well 
documented and the typical solution is to Dial(Zap/g1/w${EXTEN}) instead of 
just Dial(Zap/g1/${EXTEN}).  

The problem stems from a combination of the LEC switch being slow to begin 
detecting DTMF and from the Zaptel drivers not waiting for dialtone.  You may 
notice that this problem only occurs at certain times of the day and this is 
due to the LEC's call volume.  When you call during busy times it may take a
few seconds for the LEC's switch to "get around" to your line.  Do
you
sometimes notice that you don't hear dialtone (with a normal phone hooked up
to the line) for a second or two?

-A.

Heath Bowlin wrote:
> We have implemented * in one of our branch offices and recently ran up 
> against a very strange issue. On random occasions, when we would dial 
> out using our trunk lines, we would get a message stating ?you do not 
> have to dial a 1 or 0 when calling this number? even if we didn?t dial 
> a 1 or 0 in the dial sequence at all. After much troubleshooting, we 
> found users with similar issues that simply put a wait (w$EXTEN) in 
> the dial sequence and fixed the problems. We did the same and it 
> automagically fixed itself. This is great, of course, but I was 
> wondering if someone out there could give me a more detailed 
> explanation of why this works and why you have to implement this trick 
> with some telecom providers and not with others. Verison provides our 
> trunks at our branch office, but this issue has never arisen at our 
> home office where we have SBC. We are running * v1.0 with a Digium 4 
> port FXO TDM card.
>
> Thanks,
>
> Heath Bowlin
>
Simple
Asterisk with either the X100 or the TDM400 doesn't bother to detect 
dialtone.
It simply starts dialing, regardless if the CO is ready or not.
It also doesn't bother to detect lack of battery on the line, indicating 
a line might be disconnected.
Even very simple telecom devices, such as dial-up modems, for years now 
have had that option.
It escapes me why someone felt this wasn't a necessary provision in Asterisk
Too much time on new bells and whistles, and not enough attention to 
detail , I suppose.

Can someone smarter than I turn this into a bug report please?

John Novack