[AusNOG] ADSL2+ line sync data

[Tony]

----- Original Message -----
> From: Mark Newton <newton at atdot.dotat.org>
> 
> On Sep 16, 2013, at 4:01 PM, Tony <td_miles at yahoo.com> wrote:
> 
>>  All video conf & VoIP I've seen uses UDP which means the video 
> conferencing session to the medical professional is not going to care about 
> ACK's at all.
> 
> Skype, Google Hangouts and Apple Facetime use TCP.

Both Skype & Google attempt to use UDP first and only fall back to TCP if UDP is blocked/doesn't work. Most standard home/soho router/firewalls would I imagine allow the preferred UDP option to work. I tested a skype call just now and it used UDP and that works outbound through my firewall which is an old snapgear with a fairly default ruleset (couple of NAT ports inbound to servers, allow anything outbound).

Don't know about Facetime, the FAQ on ports it uses is unclear which is used for what purpose, but something I read suggests that it is much the same and basically uses SIP signalling (which uses TCP of course) with a UDP RTP stream that is wrapped around with some registration, authentication and other Apple stuff. It may also fall back to using TCP for transport of the RTP stream if UDP fails, this wasn't clear to me in anything I read.

I'd also be fairly dissapointed if my medical professional was going to use any of those three video conf solutions for a remote "consultation". Having said that I can see that they are cheap, widely spread, easy to use & easily available to the masses, so maybe they would ?

Aren't we all moving to IPv6 anyway at which point all of these three video conf solutions (Skype, Google, Apple) will be able to use their preferred UDP when NAT ugliness goes away with v6 ?!


regards,
Tony.


http://en.wikipedia.org/wiki/Skype_protocol#Login
http://support.google.com/a/bin/answer.py?hl=en&answer=1279090
http://support.apple.com/kb/HT4245