Voice channels (FTTH, DOCSIS, VoLTE)

Jean-Francois Mezei jfmezei_nanog at vaxination.ca
Mon Nov 21 23:12:09 UTC 2016

On 2016-11-21 15:18, joel jaeggli wrote:

> SRB and URB are the l2 presentation of the tunnels established for user
> and signaling traffic.

OK, so wth LTE, if carrier has 10mhz up and down, this represents a
single chunk of spectrum providing one pipe ? (in fibre terms: a single
light colour through one strand)

The "smoke and mirrors" is accomplished by having different tunnels
inside that one pipe, with some tunnels granted QoS or other
preferential treatment between the IMS/VoiP servers and the RAN ?

When a handset sends a VolTE packet to the "IMS" APN, is there any
preferential treatment given between the handset and the antenna ? Or
does preferential treatment begin at the RAN where the packet is
recognized as going to "IMS" APN and going on the fast track to it ?

or put another way. If everyone uploads a HD selfie movie at the same
time, are handset uploads slowled with normal TCP flow control (drop a
packet, no ack received, handset halves the TCP window size)?

In other words, some router near antenna, to prioriotize packets to the
IMS/VoLTE server, will flow control normal IP traffic to maintain
sufficient upload capacity for VolTE traffic ?

Or are the tunnels fixed in capacity such that unused capacity in one is
never used by the other ?

>From a policy point of view, if I propose a net neutrality policy, I
have to make sure it doesn't prevent normal VoLTE functioning, while
preventing abuse of the ability for an incumbent to prioritize/zero-rate
its own services.

For instance:

AT&T in USA zero rates voice but not video calls over VoLTE.
Rogers in Canada zero rates both voice and video calls over VoLTE.

So if VoLTE video travels to the same IMS as voice, and not through the
normal IP APN, that means AT&T has to count the video traffic separately
and add it. But if Video goes through the normal IP traffic APN, it gets
counted fairly, like Skype packets, but Rogers then captures that
netflow and later deducts it from the total usage.

The issue here is that VoLTE is the new kid on the block with video
capability and incumbents can use their power to displace competitors
such as Skype/Facetime and that may constitute undue preference, unless
the standards are such that they have no choice because that it how it
has to work. (But AT&T shows that it can still count video and treat
video calls fairly compared o skype video calls).

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