RE: [Serusers] NAT & RTPPRoxy

Thanks Jan, I should have made myself a little bit clearer; I am using the RTC 1.2 API (http://msdn.microsoft.com/library/default.asp?url=/library/en-us/rtcclnt/rt c/real_time_communications_rtc_client_start_page.asp) What I find the most interesting is - http://msdn.microsoft.com/library/default.asp?url=/library/en-us/rtcclnt/rtc /traversal_of_upnp_enabled_nats.asp specifically the last sentence of the third paragraph. Why I can't provide it my external IP address and port on the NAT is annoying! I wonder if it would be possible to modify the REGISTER message on the way to the SIP server and change the IP:Port to my external NAT address mapping - or get NATHelper to do this for me. Gary -----Original Message----- From: Jan Janak [mailto:jan@iptel.org] Sent: 03 September 2003 10:34 To: Gary Brewer Cc: serusers(a)lists.iptel.org Subject: Re: [Serusers] NAT & RTPPRoxy Hello, comments inline. All the NAT stuff is quite complicated and whether it would work or not depends on many factors. On 03-09 09:55, Gary Brewer wrote: symmetric. That depends. It could work even with symmetric NAT if the client you are using does support symmetric signalling and RTP (I am not sure Windows Messenger is). That means the user agent must be ready to receive SIP requests and responses on the same port which was used as the source port for sending SIP messages. Also it must support symmetric RTP to make media work. Also the user agent must create REGISTERs containing public IP of the NAT (can be determined using STUN, for example), or you would have to use nathelper module on the server. to Yes, but Windows Messenger doesn't support STUN. In case of symmetrict RTP, the client in the public internet will ignore what it receives in SDP and will send media back to the same IP and port from which it comes from the other side. That makes the communication through a NAT possible, but the client behind the NAT must send first media package (that packet will open a pinhole in the NAT). Also both sides must support symmetrict RTP and the client behind the NAT must signal that it is using this approach. If the clients do not support symmetric signalling, then some kind of "NAT configuration" would be necesarry. For example, many user agents can be configured to use ports from a specified port range only for RTP (let's say ports 10000-10100). You can then configure your NAT box to forward all the ports from the range back to your user agent. this NAT bind register If both clients are behind NATs then you would probably have to use an RTP proxy which will be placed in the public internet. See the previous insertion. It could help in the case when both clients are behind NATs and it could possibly help in some other cases too. around There is a couple of people who are running their clients behind NATs on the mailing list, so I hope they could give you some advice. Jan. This email may contain material that is confidential and/or privileged. It is for the sole use of the intended recipient. Any review, reliance or distribution by others of the e-mail or its contents or forwarding without express permission is strictly prohibited. No contractual undertakings are accepted by virtue of transmission of this e-mail unless expressly stated otherwise in the text of the e-mail itself. If you are not the intended recipient, please contact the sender and delete all copies. Contact us directly or via our website at www.rawcommunications.com.