Hello Prem, These functions were moved from 'nathelper' to a separate 'rtpproxy' module, but otherwise largely unchanged in nomenclature. http://kamailio.org/docs/modules/4.0.x/modules/rtpproxy.html The 'rtpproxy_sock' parameter is still there: http://kamailio.org/docs/modules/4.0.x/modules/rtpproxy.html#idp16978832 -- Alex -- Alex Balashov - Principal Evariste Systems LLC 235 E Ponce de Leon Ave Suite 106 Decatur, GA 30030 United States Tel: +1-678-954-0670 Web: http://www.evaristesys.com/, http://www.alexbalashov.com/