AW: [Sip-implementors] Active Passive SDP extensions!

[Christian Stredicke]

Hi Rahul,   No the approach is not standardized at all. That is what we are trying to indicate by the “x-“ in the beginning of the field. However, I think it is the best way to solve a problem and we should standardize it that way.   The algorithm to determine which address to use is like this: the phone starts with the right mode addressed and checks if the shares the same public IP address. If this is a case, but call will obviously go within the same private network, and in that case it will use the other address indicated in the SDP field. this way the media traffic will stay complete local. This is important when you are calling your neighbor, and shares the same private network with you. (Otherwise he will not be able to hear you!)   In the case of 3 tier Nat, things are getting messy. The main problem here is to determine the address of the router in the middle. in the case of STUN it will be necessary to put a STUN server into the private network. In the case of the UPnP I must say I am clueless how this can be achieved. however, you would indicate that the three tiers by providing three addresses in the SDP record.   Best regards,     Christian -- Dr.-Ing. Christian Stredicke sip:[EMAIL PROTECTED]   -----Urspr�ngliche Nachricht----- Von: Rahul Gulati [mailto:[EMAIL PROTECTED]] Gesendet: Montag, 9. Dezember 2002 12:51 An: Christian Stredicke; [EMAIL PROTECTED] Cc: 'Jonathan Rosenberg'; [EMAIL PROTECTED]; [EMAIL PROTECTED]; R. Rajagopalan; [EMAIL PROTECTED]; [EMAIL PROTECTED] Betreff: Re: [Sip-implementors] Active Passive SDP extensions!   Hi, Christian,   Thanks for ur inputs, I need to know if this procedure is standardised i.e. if I send two IP addresses in my SDP which one will the endpoint recognise it will try to open a connection for one IP address if it fails then tries on the other IP address.   Is this procedure standardised/ Do all SIP phones support this "a=x-private:192.168.0.4:10004 217.230.188.194:22339" field?   Also, How does it get the *UDP* NAT-bindings in this case?   Best Regards' Rahul   ----- Original Message ----- From: Christian Stredicke To: 'Rahul Gulati' ; [EMAIL PROTECTED] Cc: 'Jonathan Rosenberg' Sent: Monday, December 02, 2002 1:09 PM Subject: AW: [Sip-implementors] Active Passive SDP extensions!   What we do is sending additional information that indicates both the private address and the public address. This is done both in the SDP part *and* the contact, as there we have the same problem.   For two-tier NAT, there would be three addresses.   I already proposed this to the MIDCOM group months ago, but no feedback so far. I think it’s the only way to do it.     INVITE sip:[EMAIL PROTECTED] SIP/2.0 Via: SIP/2.0/UDP 217.230.188.194:22188;branch=z9hG4bK-zak6pmm81wpf Max-Forwards: 70 From: "Christian Stredicke" <sip:[EMAIL PROTECTED]>;tag=3hdf7b6ynj To: <sip:[EMAIL PROTECTED]> Call-ID: [EMAIL PROTECTED] CSeq: 1 INVITE Contact: <sip:[EMAIL PROTECTED]:22188;srcadr=192.168.0.4%3A5060;transport=udp;line=1> User-Agent: snom200-1.14d Accept-Language: en Accept: application/sdp Allow: INVITE, ACK, CANCEL, BYE, REFER, OPTIONS, NOTIFY, SUBSCRIBE, PRACK, MESSAGE Supported: timer, 100rel, replaces Session-Expires: 7200 Content-Type: application/sdp Content-Length: 322 v=0 o=root 12723 12723 IN IP4 217.230.188.194 s=SIP Call c=IN IP4 217.230.188.194 t=0 0 m=audio 22339 RTP/AVP 0 101 a=rtpmap:0 pcmu/8000 a=rtpmap:101 telephone-event/8000 a=fmtp:101 0-15 a=x-private:192.168.0.4:10004 217.230.188.194:22339     -- Dr.-Ing. Christian Stredicke sip:[EMAIL PROTECTED]   -----Urspr�ngliche Nachricht----- Von: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]] Im Auftrag von Rahul Gulati Gesendet: Montag, 2. Dezember 2002 07:14 An: [EMAIL PROTECTED] Cc: Jonathan Rosenberg Betreff: [Sip-implementors] Active Passive SDP extensions!   Hi, All,   I had a question regarding extensions to SDP to make it NAT friendly, some *drafts* mention using "active" to indicate UAs ( behind NAT ) which want to initiate a bi-directional RTP/TCP connection and using "passive" for UAs at the receiving end.   Is there a procedure in the SIP-SDP *standards* by which we can specify an active side of a TCP connection or an active side of a bi-directional RTP connection?   Best Regards' Rahul