[Asterisk-Dev] MWI From tag in SIP message

[Chris A. Icide]

In the following message, there is a tag after the From: header.  What 
is the function of this tag?  The MWI indication comes right after the 
call that left a voicemail, but the tag isn't the same as the tag on the 
previous call.  As you can see the device (a softswitch) receiving the 
MWI indication rejects the notify due to the fact that the 
tag=as1020fb8e exists after the From message.  The softswitch engineer says:

"It looks like the SoftSwitch doesn't like the tag on the end of the From
header. The reason for this is that tags generally indicate that the
message is part of a dialog (such as a subscription or a call), whereas
SoftSwitch only supports unsolicited (out-of-dialog) NOTIFYs on the
voicemail side."


Reliably Transmitting (no NAT) to 10.100.13.10:5060:
NOTIFY sip:5096493804 at x.y.z SIP/2.0
Via: SIP/2.0/UDP 10.100.13.250:5060;branch=z9hG4bK00ed7773
From: "asterisk" <sip:asterisk at 10.100.13.250>;tag=as1020fb8e
To: <sip:5096493804 at x.y.z>
Contact: <sip:asterisk at 10.100.13.250>
Call-ID: 32e1487305ea31126c84151d3d6be316 at 10.100.13.250
CSeq: 102 NOTIFY
User-Agent: Asterisk PBX
Event: message-summary
Content-Type: application/simple-message-summary
Content-Length: 43
                                                                                       

Messages-Waiting: yes
Voice-Message: 5/0
                                                                                       

---
Scheduling destruction of call 
'32e1487305ea31126c84151d3d6be316 at 10.100.13.250' in 15000 ms
asterisk*CLI>
<-- SIP read from 10.100.13.10:5060:
SIP/2.0 403 From: URI not recognized
From: "asterisk" <sip:asterisk at 10.100.13.250>;tag=as1020fb8e
To: <sip:5096493804 at x.y.z>;tag=x.y.z+1+0+c33a772dVia: SIP/2.0/UDP 
10.100.13.250:5060;branch=z9hG4bK00ed7773
Server: DC-SIP/2.0
Organization:
Content-Length: 0
Call-ID: 32e1487305ea31126c84151d3d6be316 at 10.100.13.250
CSeq: 102 NOTIFY