Subject: RE: Overlap signaling to INVITE

From: "Schroeder, Tim" <[email-masked]>
Date: Tue, 23 Nov 1999 16:25:54 -0600

> Anyone know how this is handled in the phone network? How does a switch
> know when it has enough digits to make a routing decision?

In the US, the switches are provisioned with "forms" that describe the
dialing plan.  The basic plan is pretty straightforward (7 digits, 1 + 10
digits, etc.).  By looking at the dialed number, the switch can tell whether
to route the call to an (error) announcement server or to another carrier
(where it may complete or fail).  There are also the CACs (carrier access
codes, the 101xxx and 1010xxxx strings), x11 calls, etc., that complicate
the dialing plan -- but still the switch is provisioned with enough
information to know how many digits to expect.

In the case of a call from the US to somewhere else (011+), we know only the
minimum and maximum length of a generic international number.  If the caller
dials at least the minimum number, the switch will wait (on the order of
5-10 seconds, depending on provisioning) to see if more digits might be
forthcoming, so that much delay is introduced.  After the timeout (or the
maximum number of digits are received), the number is sent, and any
subsequently dialed digits are ignored.

Tim Schroeder

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From: "Tu Do" <[email-masked]>
Date: Thu, 25 Nov 1999 11:36:25 -0500

> -----Original Message-----
> From: [email-masked]
> [mailto:[email-masked]]On Behalf Of Schroeder,
> Tim
> Sent: Tuesday, November 23, 1999 5:26 PM
> To: [email-masked]
> Subject: RE: Overlap signaling to INVITE
>
>
>

I thought that the switch would try to route the call as soon as the minimum
number digits were collected.  The downstream switch could return and say
that more digits were needed to route the call, then more digits would be
collected.  This process is what's called "Overlap Outpulsing", isn't it?
Can someone from Europe confirm this?  Still the question is what does SIP
do to collect more digits?  If this is done in the Body using SDP, then how
would Proxy/Redirect servers do this?

Tu Do