Date: Wed, 18 Jan 2012 10:05:26 +0100 From: Maciej Milewski <milu@dat.pl> To: Matthias Apitz <guru@unixarea.de> Cc: freebsd-net@freebsd.org Subject: Re: PPP to UMTS provider && incoming traffic (TCP, UDP) Message-ID: <7227503.Fd8S0FJ3Ep@snifi> In-Reply-To: <20120118063549.GA2742@tinyCurrent> References: <20120117190847.GA1255@tiny> <1784936.VLDeoQkidl@snifi> <20120118063549.GA2742@tinyCurrent>
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Dnia środa, 18 stycznia 2012 07:35:49 Matthias Apitz pisze: > Thanks for your feedback; I think too, that UDP downstream is blocked if > there is not upstream UDP initialized for the same socket pair; and VoIP > is using different UDP ports for up- and downstream media (audio). > > What I'm wondering is, how does Skype works (which is fine with my UMTS > provider at the same time), have to check this with TCPDUMP... > > matthias Skype according to wikipedia[1] uses such scenario: 1. start 2. send UDP packet(s) to HC 3. if no response within 5 seconds then 4. attempt TCP connection with HC 5. if not connected then 6. attempt TCP connection with HC on port 80 (HTTP) 7. if not connected then 8. attempt TCP connection with HC on port 443 (HTTPS) 9. if not connected then 10. attempts++ 11. if attempts==5 then 12. fail 13. else 14. wait 6 seconds 15. goto step 2 16. Success So it uses TCP and to obey blocked ports uses www traffic ports: 80 and 443. [1] http://en.wikipedia.org/wiki/Skype_protocol -- Maciej Milewskihelp
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