[asterisk-users] Incoming side of SIP trunk does not work unless I add "insecure=very"

[Frank Bulk - iName.com]

The incoming (Class 5 switch to Asterisk PBX) side of a SIP trunk does not
work unless I add "insecure=very" to my "Outgoing settings", but I don't
want to do that.  I do want to authenticate.  Outgoing (Asterisk PBX to
Class 5 switch) calls do authenticate and work.

The Nortel CS 1500 I'm using as the PSTN-side of my SIP trunk has a username
and password that it's sending out.  But the INVITE is responded by the
Asterisk with "SIP/2.0 403 Forbidden"

I've changed the INVITE message to mask the real telephone numbers, SIP
server, passwords, and IP addresses, but I did that using search and replace
so the structure is intact.

What do I need to configure in the "Incoming Settings" panel for the CS
1500's INVITE to my Asterisk server to work?  I've tried all kinds of
combinations of user,username,authname using +15552027020,host with IP
and/or DNS name, but nothing appears to work.

Frank

INVITE message from Wireshark packet capture:

INVITE sip:+15552027020 at sip.acme.com SIP/2.0
From:
<sip:5552022441 at 172.16.10.40>;tag=f76c66d0-c7784528-13c4-2dbba4-767e6552-2db
ba4
To: <sip:+15552027020 at sip.acme.com>
Call-ID: f379f62-29173-3895-b14271f5-40802-45378 at 172.16.10.40
CSeq: 5102 INVITE
Via: SIP/2.0/UDP 172.16.10.40:5060;branch=z9hG4bK-2dbba4-b2a4fa3a-7cd7598
User-Agent: Nortel CS1500UA/v02.00.REL01
Accept: application/sdp
P-Asserted-Identity: <sip:5552022441 at 172.16.10.40;user=phone>
Privacy: none
Remote-Party-ID: <sip:5552022441 at 172.16.10.40;user=phone>; party=calling;
privacy=off
Max-Forwards: 70
Supported: 100rel,replaces
Allow: INVITE, ACK, OPTIONS, CANCEL, BYE, REFER, PRACK
Contact: <sip:5552022441 at 172.16.10.40>
Authorization: Digest
username="username",realm="asterisk",nonce="118af2b0",uri="sip:+15552027020@
sip.acme.com",response="111e63ec2a1f3ebabefe4f7dae4087a1",algorithm=MD5
Content-Type: application/SDP
Content-Length: 167

v=0
o=- 2973921782 2973921782 IN IP4 172.16.10.65
s=SIP Call
c=IN IP4 172.16.10.65
t=0 0
m=audio 36224 RTP/AVP 0
a=rtpmap:0 PCMU/8000
a=ptime:20
a=sendrecv