Dear All , I have enabled TLS and SRTP for internal profile meant only for internal calls. In Vars.xml , i made rtp_secure_media = true. Also in directory default.xml , i modified the following param. <param name="dial-string" value="{rtp_secure_media=${regex(${sofia_contact(${dialed_user}@ ${dialed_domain})}|(transport=(?i)TLS))},presence_id=${dialed_user}@ ${dialed_domain}}${sofia_contact(${dialed_user}@${dialed_domain})}" /> Internal calls are working well with these changes and internal calls between 2 end points are established using TLS / SRTP . For outbound gateway based calls , we opted to make it without TLS / SRTP by disabling tls <param name="tls" value="$${external_ssl_enable}"/> where external_ssl_enable is false. The late negotiation is true. It was noticed that any outbound calls made through the external gateway is also going out with RTP/SAVP in SDP and hence our ITSP is rejecting the calls with error 488 "Not acceptable here" Is there any way to resolve this issue. Any help in this regard is highly appreciated. Thanks and Regards Abdul Rasheed