[VoiceOps] SIP phone without using local dial plan

Eric Wieling EWieling at nyigc.com
Fri Sep 23 16:52:28 EDT 2011

-----Original Message-----
From: voiceops-bounces at voiceops.org [mailto:voiceops-bounces at voiceops.org] On Behalf Of Stephen Sprunk
Sent: Friday, September 23, 2011 4:41 PM
To: voiceops at voiceops.org
Subject: Re: [VoiceOps] SIP phone without using local dial plan

On 23-Sep-11 09:08, Mark R Lindsey wrote: 

	Normally, the SIP endpoint that device that collects digits is responsible for knowing when a correct and complete number pattern has been dialed. The same is true for MGCP devices when configured to  match a digitmap; they only send off the NTFY when a pattern of digits has been dialed, or else a timeout has occurred.

	I'm almost certain that there is no way in the Cisco 7940/7960 SIP firmware to override this norm. You probably need to configure the digit map in the phone to match the digit map from your switch.

That's the normal expectation.  However, if the client and server correctly implement the 484 (Address Incomplete) error code, that is not required.  Here's how it should work:

1. User dials "9"
2. Client sends INVITE for sip:9 at server (or tel:9)
3. Server responds with 484
4. Client waits for more digits
5. User dials "1"
6. Client sends INVITE for sip:91 at server (or tel:91)
7. Server responds with 484
8. Client waits for more digits
9. User dials "1"
10. Client sends INVITE for sip:911 at server (or tel:911)
11. Server completes call normally

I have no idea whether the Cisco 79xx code does this, but it should be relatively easy to test if your server is known to support it: just give the phone a digit map that accepts any single digit and see what happens.

---------------------------------------- REPLY --------------------

It has been a while, but I think Ciscos (SIP) phones support some kind of "hotline" (aka batphone) feature.  If your PBX has a DISA feature you can hotline to DISA to get a dialtone and have the PBX collect digits.  This is an ugly hack.  The method above is the "right way", but if your  phone does not support 484, this method might work.  Be VERY careful to make sure DISA cannot be accessed from outside your PBX. 

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