[asterisk-users] Asterisk 11.Why two NOTIFY while ringing ?

[Olivier]

Hello,

On a Asterisk 11.12.0, I'm studying BLF behaviour with Yealink phones.
My ultimate goal is to present Operator the name and number of every
incoming call so that he/she can if it's worth to pickup a ringing
incoming call.

I've discovered notifycid option in sip.conf.

When a call comes in, I can see that Asterisk is sending two
successive NOTIFY messages while the target is still in Ringing state.

(Unfortunately, Yealink phones display both NOTIFY messages to
Operator but that's another story).

Here is the (anonymized) content of both NOTIFYs:

<?xml version="1.0"?>
<dialog-info xmlns="urn:ietf:params:xml:ns:dialog-info" version="4"
state="full" entity="sip:96 at 172.16.2.1">
<dialog id="96" call-id="pickup-620171529 at 172.16.2.100"
local-tag="387088992" remote-tag="as4677fcde" direction="recipient">
<remote>
<identity display="96">sip:96 at 172.16.2.1</identity>
<target uri="sip:96 at 172.16.2.1"/>
</remote>
<local>
<identity display="96">sip:96 at 172.16.2.1</identity>
<target uri="sip:96 at 172.16.2.1"/>
</local>
<state>early</state>
</dialog>
</dialog-info>


<?xml version="1.0"?>
<dialog-info xmlns="urn:ietf:params:xml:ns:dialog-info" version="5"
state="full" entity="sip:96 at 172.16.2.1">
<dialog id="96" call-id="pickup-620171529 at 172.16.2.100"
local-tag="387088992" remote-tag="as4677fcde" direction="recipient">
<remote>
<identity display="Foo">sip:+33123456789 at 172.16.2.1</identity>
<target uri="sip:+33123456789 at 172.16.2.1"/>
</remote>
<local>
<identity display="Bar">sip:96 at 172.16.2.1</identity>
<target uri="sip:96 at 172.16.2.1"/>
</local>
<state>early</state>
</dialog>
</dialog-info>


What is the purpose of these 2 messages ?
Is there a way to get only one ?

Regards