Hi, On Fri, Mar 12, 2010 at 4:32 PM, Thomas Gelf <[email protected]> wrote: > All, > > wondering myself where I can find an RFC section stating how an UAC > shall behave, if it discovers itself being behing a symmetric NAT (as of > RFC3489). Shall it fill Via, Contact and SDP with it's internal IP:Port, > or shall it use it's reflective ip:port pair, even if knowing that it > will not be useful for anything (apart from "hiding" internal IPs)? > > I would opt for the former, as this would allow NAT-aware proxies (or > those braindead devices calling themselves ALG) to easily help him. In > the latter case a proxy would still be able to discover that the UAC > needs "some assistance" by comparing source ip:port with what is written > in it's Via/Contact headers, but this alone would usually not help > against location databases filling up with registrations using many > different Contact's. > > Unfortunately out in the wild I've met both behaviours. I would really > like to try explaining some vendor what they are doing wrong - however I > did not find anything "proving" what the correct behaviour would be in > this case. > > Can anyone give me a little hint? >
I'm not an expert myself, but hope this gives you a little hint :) The fact that a user is behind symmetric NAT doesn't mean that it will need assistance 100% of the times (only 99,999% xD). If user A is behind a symmetric NAT and user B is on open internet without NAT and they are using ICE, they will be able to talk to each other directly because of the peer reflexive candidates that user B will guess. Regards, -- /Saúl http://saghul.net | http://sipdoc.net _______________________________________________ Sip-implementors mailing list [email protected] https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
