> -----Original Message----- > From: Magnus Westerlund [mailto:magnus.westerlund@xxxxxxxxxxxx] > Sent: Tuesday, February 26, 2008 6:01 AM > To: Phelan, Tom > Cc: Dan Wing; gorry@xxxxxxxxxxxxxx; 'dccp' working group; > Colin Perkins > Subject: Re: DCCP-over-UDP [was > draft-phelan-dccp-natencap-00.txt] > > Hi, > > There has been a lot of talk in this thread about DNS. I want > a solution > that works without DNS. If one uses SIP or RTSP to establish > a media pat > using DCCP. In most cases one do include the explicit IP > address rather > than the FQDN. > Thus no DNS queries etc. I think something that makes > this work on the same port is desirable. I agree that we want something that doesn't require DNS. However, SIP and RTSP (which use SDP) don't require DNS. The SDP indicates the transport protocol (today, UDP) and port. I expect with DCCP you could indicate the transport protocol (DCCP-RAW, DCCP-UDP) and port. Syntax would be something vaguely like: v=0 o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com s= c=IN IP4 client.atlanta.example.com t=0 0 m=audio 49170 RTP/AVP/DCCP 0 a=dccp-raw 49172 where the "m=audio" line indicates RTP-over-DCCP-over-UDP is on UDP port 49170 and "a=dccp-raw" indicates that same profile (RTP/AVP) is available on DCCP port 49172. I expect that draft-ietf-mmusic-sdp-capability-negotiation would have a prettier and more useful way of expressing this sort of thing, especially if there is a desire to also fall back to RTP-over-UDP (without any DCCP). Using DNS SRV, the same thing would be expressed as: _foobar._dccp-udp SRV 0 0 49170 client.atlanta.example.com. _foobar._dccp SRV 0 0 49172 client.atlanta.example.com. -d
