Re: [rtcweb] draft-jennings-rtcweb-qos: QCI "marking"?

On Sep 18, 2012 1:08 AM, <Markus.Isomaki@nokia.com> wrote:
>
> Hi,
>
> Martin Thomson wrote:
> >
> >On 10 September 2012 07:15, Harald Alvestrand <harald@alvestrand.no>
> >wrote:
> >> - Pointers to documentation on how browsers are expected to be able to
> >> set QCI and WiFI markings would be a good addition. Compared to those,
> >> DSCP codepoint setting is well understood.
> >
> <snip>
> >
> >What do people think about NOT including QCI/WiFi markings?  Is it not
> >possible for a wireless interface to examine DSCP markings in order to
> >determine the markings for the link?  We should endeavour to maintain the
> >proper abstractions.
> >
>
> I'm not even sure if the browser or even the OS can influence much the
QCI or bearer selection in LTE. I think the model is such that the
"network" sets up these special non-best-effort bearers, and gives the
endpoint the classifier rules related to them. The rules tell the endpoint
how to map outgoing packets to the bearers. Typically the rules are based
on source/destination IP and port, and the transport protocol. Someone may
be able to confirm, but I believe DSCP can be used too. But basically the
rules come from the network and the endpoint just follows them.
>
> So, somehow the browser or the JS app would first have to convince the
access network provider to setup the special bearer so that the right flows
get classified to it. In IMS the SIP proxy reads the SDP and tells some
network element what audio or video flows are being setup and what their
5-tuples are, so the network is being able to setup the bearers correctly
for them. The endpoint merely waits for this setup and acts accordingly.
This works as the SIP proxy is run by the access operator. In RTCWeb the
same could work if the calling site had a relationship with the access
operator. I've heard that there is some work by some operators to offer Web
APIs for 3rd party apps to do the bearer setup requests more ad hoc. Most
of this may be outside the scope of RTCWeb but I think the document should
have some explanation on how it works from the OS, browser, JS client,
calling site, and mobile operator perspective.
>
> On the "transport" or "data path" level I don't think the browser needs
to understand anything about QCIs. DSCP marking should be good enough.
>
> Anyone with more LTE/mobile clue that could comment on this?
>
> Markus
>

Your understanding is similar to mine.

Generally speaking, qos in 3gpp networks is network initiated and
controlled by a PCRF. The UEs are generally not trusted, as they may abuse
qos.

I am told that qos is an important differentiator for the operator run
services and consequently will not be generally available to 3rd party apps
such as webrtc.

I am generally sceptical about qos on the internets, and we may be getting
into a dangerous area if we start to assume networks will give anything
more than best effort to webrtc.

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