ONTs

Thu Jan 13 05:59:08 UTC 2022

On 1/12/22 4:15 PM, Josh Luthman wrote:
> I would have to imagine any QOS/traffic shaping is done in the OMCI and 
> hence would probably be in the GPON spec, g.984.  I would look there.
> 
> Just guessing it would hold true with XG/s/PON, NGPON, etc.

The way at least my gear (Adtran) works is that you configure 
shaping/policing as part of the provisioned service.  That information 
is communicated to the ONTs via the OMCI.

AFAIK, the ONT enforces admission control on the upstream (and 
coordinates for timeslot assignments with the OLT since upstream 
oversubscription is supported and common), and the OLT enforces 
downstream egress control.

You can configure whether you want rate control to be based on hard 
policers (instantaneous drop once CIR+CBS+EIR+EBS is exceeded) or 
whether you want it to "shape" the traffic by delaying things.  The 
latter is usually more user-friendly and certainly easier to set up, but 
it can result in bufferbloat, and they don't provide very friendly knobs 
to tune the maximum queue length.  I haven't heard any real complaints 
from folks.  DSLReports gives me like a C for bufferbloat but doesn't 
really make it clear why.  The queue is, at most, a few ms in depth.

You can tell it to honor 802.1p CoS, IP ToS, or IP DSCP in various ways 
and map them to separate queues with separate policers/shapers and WRR 
priority.  This is semi-automated if you are doing voice/video via their 
provisioning environment.

YMMV on other vendors' gear.