[standards-jig] VoIP, JEP-0065 and UDP?

Krzysztof Szyntar criss at poczta.neostrada.pl
Sun Jan 25 15:55:21 UTC 2004


Hello Matthias,

Friday, January 23, 2004, 11:36:07 PM, you wrote:

MW> SOCKS5 has still a TCP connection on the local side of the SOCKS proxy.
MW> If your connection to the JEP-proxy is TCP and your application works
MW> with that, I guess you should be able to transfer the entire protocol on
MW> TCP.
Yes, I thought about it and indeed, in desperate cases such a solution
seems possible.

MW> I don't say, that audio/video should be done over TCP ... no, I really
MW> advise everyone to use UDP for that. But I guess a JEP-proxy supporting
MW> UDP on the remote side and TCP on the local side won't help you in this
MW> case either.

MW> I guess it was on this list where it has been discussed how to pass NAT
MW> with UDP packets.

MW> (As UDP is connectionless, you won't get any benefit by using a proxy
MW> that speaks UDP on both sides, you would just have the case where you
MW> directly communicate with someone else using UDP.)

If I understand correctly, you say that it's imposible to get an answer to
your UDP packets if you are connected through a NAT?
That's not quite true. Most NATs, after someone sends a UDP datagram,
leave the port it went through open (for a minute or so) and listen
for some result.
That's why services such as ping are possible.
So if we take advantage of this behaviour, we can definitely construct
a UDP proxy.

MW> <a-little-bit-joking>
MW> ... yes ... NAT is horrible and only neccessary because there are far to
MW> few IPv4 addresses. Why can't the internet just kick IPv4 and only use
MW> protocols with at least 2^128 addresses (e.g. IPv6) ...
MW> </a-little-bit-joking>

I wish the life was that easy ;)

-- 
Best regards,
Krzysztof                            mailto:criss at poczta.neostrada.pl




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