james woodyatt skrev:
On Apr 19, 2007, at 12:47, Iljitsch van Beijnum wrote:On 19-apr-2007, at 19:44, james woodyatt wrote:An RTSP server may *also* put any pair of UDP port numbers (starting on an even number) in the client_port attribute of a Transport header, so the ports that would have to be opened to the whole Internet include a very wide range, potentially *all* of them.That seems strange. Wouldn't the client want to have some say in the port number it needs to open up?I wasn't involved in the design of the RTSP protocol.
This is a misunderstanding of how RTSP works. What happens when one configures a media stream is that the client includes the ports and address on which it like to receive the media stream. The server do add an address and port(s), the one it is going to send from.
When it comes to RTSP proxies they can select if they relay the media streams or not. But unless they actually are implemented in the FW/NAT/NAP they do not really provide any benefit the application to traverse the middlebox with filtering behavior. And I have to agree strongly that ALG functions only should be deployed in managed boxes.
Regards Magnus Westerlund IETF Transport Area Director & TSVWG Chair ---------------------------------------------------------------------- Multimedia Technologies, Ericsson Research EAB/TVM/M ---------------------------------------------------------------------- Ericsson AB | Phone +46 8 4048287 Torshamsgatan 23 | Fax +46 8 7575550 S-164 80 Stockholm, Sweden | mailto: magnus.westerlund@ericsson.com ----------------------------------------------------------------------