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

Joe Hildebrand JHildebrand at jabber.com
Mon Jan 26 23:52:10 UTC 2004

SOCKS 5 does UDP, too, right? (RFC 1928, UDP ASSOCIATE)  I'd suggest a
combination of STUN (to connect if we don't need a proxy) then falling back
on SOCKS5.

Joe Hildebrand


> -----Original Message-----
> From: Krzysztof Szyntar [mailto:criss at poczta.neostrada.pl] 
> Sent: Monday, January 26, 2004 7:29 AM
> To: standards-jig at jabber.org
> Subject: Re[2]: [standards-jig] VoIP, JEP-0065 and UDP?
> >>
> >>> So if we take advantage of this behaviour, we can definitely 
> >>> construct a UDP proxy.
> >>
> >> Why a proxy if it is possible with the same technique without it?
> JH> Take a look at RFC 3489, STUN.  It describes this approach pretty 
> JH> thoroughly.
> OK, let me get back to the matter again. I think most NATs 
> nowadays work as symmetrical NATS, i.e. they map different 
> destinations to different source ports. Moreover, once they 
> create the mapping, they don't allow incoming traffic from a 
> different address and port than the destination.
> In that case it is impossible to transfer datagrams without proxy.
> Using proxy just to help both sides exchange their addresses 
> doesn't help either.
> Let's consider an example:
> - A sends a UDP to PROXY
> - B sends a UDP to PROXY
> - proxy replies, giving B the address and port of A
> - proxy replies, giving A the address and port of B
> In ideal world, A and B would now be able to exchange 
> datagrams, however, a typical NAT will check the source 
> address of incoming datagram against the mapping (it mapped 
> the port to PROXY address), and it just won't let it through.
> So we *do* have to send datagrams through proxy.
> The question remains - is there a need in the Jabber 
> community of decribing the negotiation with UDP proxy and 
> putting it into a JEP?
> --
> Best regards,
>  Krzysztof                            mailto:criss at poczta.neostrada.pl
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