1. SDP & RTP & NAT Christian Huitema

2. What NAT do Map ports –TCP connection –UDP stream (activity) Firewall variants –One port, any peer –One port, any “authorized” peer –One port per peer Two problems –Make NAT “UDP friendly”, –Use random port numbers for RTP, RTCP NAT Node S 10.0.0.1:2345 64.5.6.7:8901 “Real” Internet Natted area

3. Recommendation for NAT: draft-huitema-natreq4udp-00.txt draft-huitema-natreq4udp-00.txt Two mapping variants –Same port / Different port Two firewall variants –Accept / Require “activity” Problem –Different ports make “conferencing” very hard –Firewall makes “call transfer” and “signalling” hard –Not secure anyway… Recommendation –Use same mapping, –Don’t “firewall” the user. Can we publish it, please? NAT Node S 10.0.0.1:2345 64.5.6.7:8901 “Real” Internet Natted area T 64.5.6.7:????

4. Document mapping in SDP: draft-huitema-natreq4udp-00.txt draft-huitema-natreq4udp-00.txt NAT map RTP, RTCP –Oddity ? –Sequencing ? Mapping can be learned –Use “echo server” Proposal: document in SDP –Allow RTP > odd port –“a=rtcp=7654” AVT comment –If deviate oddity, document two ports. Decision –Last call ? NAT Node E 10.0.0.1:3456 10.0.0.1:3457 64.5.6.7:8901 64.5.6.7:7654 “Real” Internet Natted area T