Re: [Sip] Inquiry:SIP sending dialed digits in one-by-one digit format?

["Dale Worley" <[e-mail]>]

On Wed, 2010-01-06 at 06:11 +0000, hadi motamedi wrote:
> Can you please do me favor and let me know if it is technically
> feasible to send the sip dialed digits in one-by-one-digit format ? I
> mean if the subs dials say 6659983 we try to send it as 6,6,5,9,9,8,3
> but not as 6659983 in just one package with sip invite .

This is called "overlapped dialing", and there is a defined technique
for doing this.  The phone, when it receives the first digit, sends an
INVITE:

INVITE sip:6@domain SIP/2.0 -->

The proxy for the domain determines that additional digits are required,
and gives a 484 Address Incomplete response:

<-- SIP/2.0 484 Address Incomplete

When the user dials the second digit, the phone sends the accumulated
digits:

INVITE sip:66@domain SIP/2.0 -->

The proxy responds 484 again:

<-- SIP/2.0 484 Address Incomplete

This continues until the user enters a complete dial string.

However, this technique is not commonly used due to the high signaling
traffic it generates and the general difficulty having the proxy
determine whether or not the dial string is ended for all possible dial
strings.

A more common technique is to program the UA with a "dial pattern",
which is a regular expression that describes all valid dial strings.
E.g., three-digit extensions could be described "xxx", while "9 followed
by 7 digits" could be described "9xxxxxxx".  Also, the dial pattern
language usually allows a way of specifying variable-length strings via
"a series of digits terminated by a time-out":  "9xT".  This method
places the entire burden on the UA, but allows a mixture of fixed- and
variable-length strings in the dial plan.  Of course, the details vary
from one make of UA to another.

Dale