SIP Invite with the corresponding isub parameters:
INVITE sip:9999999@10.10.1.22:5060;user=phone SIP/2.0\r\nVia: SIP/2.0/UDP 10.10.1.162:5060;rport;branch=z9hG4bK-4
7cf--1432701767-4952-259\r\n
Call-ID: 7bca-427-813206014529-HVDPHY-0-10.10.1.162\r\n
CSeq: 1 INVITE\r\n
Max-Forwards: 70\r\n
To: <sip:9999999@10.10.1.22:5060;user=phone>\r\n
From: "7777777"<sip:7777777@10.10.1.162;user=phone;
isub=12345;isub-encoding=nsap-ia5>;tag=95ffcd055e0f78f7d5d397
020e89288d719bf105\r\n
User-Agent: Dialogic-SIP/10.5.3.96 HVDPHY 0\r\n
Contact: <sip:7777777@10.10.1.162:5060>\r\n
Allow: INVITE, BYE, REGISTER, ACK, OPTIONS, CANCEL, SUBS
CRIBE, NOTIFY, INFO, REFER, UPDATE\r\n
Supported: path, replaces, timer, tdialog\r\n
Session-Expires: 1800\r\n
Expires: 300\r\n
Organization: Dialogic\r\n
Content-Type: application/sdp\r\n
Content-Length: 163\r\n
\r\n
v=0\r\n
o=Dialogic_SDP 47 0 IN IP4 10.10.1.162\r\n
s=Dialogic-SIP\r\n
c=IN IP4 10.10.1.199\r\n
t=0 0\r\n
m=audio 8156 RTP/AVP 0\r\n
a=rtpmap:0 PCMU/8000\r\n
a=silenceSupp:off - - - -\r\n