[Cake] [aqm] [rtcweb] Catching up on diffserv markings

Christian Huitema huitema at microsoft.com
Thu Oct 22 16:02:21 EDT 2015

On Thursday, October 22, 2015 2:14 AM, Colin Perkins wrote:
> On 22 Oct 2015, at 08:48, Pal Martinsen (palmarti) <palmarti at cisco.com> wrote:
>> On 21 Oct 2015, at 18:10, Harald Alvestrand <harald at alvestrand.no> wrote:
>>> Den 21. okt. 2015 17:51, skrev Dave Taht:
> ...
>>> Five questions:
>>> 1) Has anyone implemented or tested putting voice and video on two
>>> different 5-tuples in any running code out there? 
>> All VC systems I know of except WebRTC-based ones do it, AFAIK. 
>> It’s putting them on the same that's unusual.
> That sounds like the world I am living in as well.

Several ports is common, but you have to consider priority issues. In a video conference, you want voice and video to be in sync, so the user sees the lips moving at the same time as the corresponding sound is heard. In fact, you want to see the lip moving slightly before you hear the sound. If voice arrives before video, many systems will delay the playback in order to achieve lip synchronization. There is not a whole lot to be gained by sending real-time voice "faster" than "video."

Dave did not ask the question, but the Cake document also mentions placing game traffic in the voice priority class. Note that Xbox One, the game traffic is encrypted with IPSEC, either natively over IPv6, or often tunneled over a single UDP port for IPv4 (http://www.nanog.org/sites/default/files/wed.general.palmer.xbox_.47.pdf). 

-- Christian Huitema

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