The outgoing SIP with isub and isub encoding parameters in From Header as well as in R-URI and To Header.
INVITE sip:9999999@10.10.1.22:5061;user=phone isub=12345;isub-encoding=nsap-ia5 SIP/2.0\r\n
Via: SIP/2.0/UDP 10.10.1.162:5060;rport;branch=z9hG4bK-26b9-8404302-4981-180\r\n
Call-ID: 355b-412-38197063142-VINN-0-10.10.1.162\r\n
CSeq: 1 INVITE\r\n
Max-Forwards: 70\r\n
To: <sip:9999999@10.10.1.22:5061;user=phone;isub=12345;isub-encoding=nsap-ia5>\r\n
From: <sip:7777777@10.10.1.162;user=phone;isub=12345;isub-encoding=nsap ia5>;tag=95ffcd055e0f78f7d5d397020e89288db79731e6\r\n