carriers need topology hiding , its an important feature for both security and also to hide you business partners from each other freeSwitch talks about it and also does a good job in hiding the signalling topology there is however a hole in the SDP manipulation that I am trying to plug and would love to get some help , obviously once resolved I am also happy to add documentation for all to use I was thinking that the best way would be to build the SDP message from scratch based on the incoming info , and maybe in special cases have the SDP copied over from the original message. is there a way to have FS build a clean SDP message ? see and example of Bria softphone making a call via freeswitch , note that the SDP to leg B contains original addresses and even internal ones incoming Invite message ------------------- INVITE sip:442078562101@pbx.rilcomm.com SIP/2.0 Via: SIP/2.0/UDP 82.80.130.222:26762;branch=z9hG4bK-d8754z-8fba35a96b6d949f-1---d8754z-;rport Max-Forwards: 70 Contact: <sip:44558678567378@82.80.130.222:26762> To: <sip:442078562101@pbx.rilcomm.com> From: <sip:44558678567378@pbx.rilcomm.com>;tag=47360c64 Call-ID: YTY4NjMwMjg4MWRmODY5NDlhOWQ4MDg5MWIwN2Y3MTY. CSeq: 1 INVITE Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY, MESSAGE, SUBSCRIBE, INFO Content-Type: application/sdp User-Agent: Bria release 2.5.4 stamp 53956 Content-Length: 325 v=0 o=- 0 2 IN IP4 82.80.130.222 s=CounterPath Bria c=IN IP4 82.80.130.222 t=0 0 m=audio 27848 RTP/AVP 18 101 a=sendrecv a=rtpmap:18 G729/8000 a=fmtp:18 annexb=yes a=rtpmap:101 telephone-event/8000 a=fmtp:101 0-15 a=alt:1 2 : XlhJjZhm LLmd1Kyz 192.168.1.50 24514 a=alt:2 1 : GOsgLipv VjRq6zYk 192.168.1.60 24514 ------------------- message to leg B see the original IP addresses in the SDP ( anything that is not 81.89.136.231) note 82.80.130.222 which is the original address being visible in the SDP fields ------------------- INVITE sip:1001@82.80.130.222:20014 SIP/2.0 Via: SIP/2.0/UDP 81.89.136.231:5080;rport;branch=z9hG4bKBBgvK7Sap23tN Max-Forwards: 67 From: "44558678567378" <sip:44558678567378@81.89.136.231>;tag=1FUrD0t1gF55a To: <sip:1001@82.80.130.222:20014> Call-ID: 8eed1cbc-9030-11de-87e7-27e3a7b5c9da CSeq: 119414118 INVITE Contact: <sip:mod_sofia@81.89.136.231:5080> User-Agent: FreeSWITCH-mod_sofia/1.0.4-hacked Allow: INVITE, ACK, BYE, CANCEL, OPTIONS, PRACK, MESSAGE, SUBSCRIBE, NOTIFY, REFER, UPDATE, REGISTER, INFO, PUBLISH Supported: timer, precondition, path, replaces Allow-Events: talk, presence, dialog, call-info, sla, include-session-description, presence.winfo, message-summary, refer Content-Type: application/sdp Content-Disposition: session Content-Length: 331 Remote-Party-ID: "44558678567378" <sip:44558678567378@81.89.136.231>;party=calling;screen=yes;privacy=off v=0 o=- 2301954626585387485 2 IN IP4 82.80.130.222 s=CounterPath Bria c=IN IP4 81.89.136.231 t=0 0 m=audio 25974 RTP/AVP 18 101 a=rtpmap:18 G729/8000 a=fmtp:18 annexb=yes a=rtpmap:101 telephone-event/8000 a=fmtp:101 0-15 a=alt:1 2 : XlhJjZhm LLmd1Kyz 192.168.1.50 24514 a=alt:2 1 : GOsgLipv VjRq6zYk 192.168.1.60 24514 ------------------- thank you Ori