Capacity planning , transit vs last mile

Jean-Francois Mezei jfmezei_nanog at
Fri Apr 1 06:38:03 UTC 2016

On 2016-03-31 19:38, Baldur Norddahl wrote:
> You will find that total data download per month is unrelated to service
> speed except for very slow service.

Yep. Netflix still takes 7mbps even if you are on a 1gbps service.
However, with families, higher speed allow more family members to be
active at same time and this could begin to have visible impact (if not

Note that a rural coop deployed FTTP for their territory, but only offer
40mbps max subscription because they can't afford the transit from the
single incumbent who offers transit in their region. So I assume that
with under 1000, service speed starts to matter when sizing the transit

> If you have too few users the pattern becomes chaotic.

My question has to do with how does one determine that theshold where
you start to get more chaotic patterns and need more  capacity per
customer than if you had over 1000 customers ?

My goal is to suggest some standard to prevent gross underprovisioning
by ISPs who win subsidies to deploy in a region.

>From what I am reading, the old standard (contention ratio of 50:1 for
residential service) is no longer valid as a single metric especially
for smaller deployments with higher speeds.

For the last mile, GPON is easy as it is essentually 32 homes per GPON
link. For cable, the CRTC would have its own numbers for number of homes
per node. (BTW, Australia's NBN V2.0 plans to have 600 homes per node
since they don't have budget to split nodes).

But for fixed wireless and satellite, there needs to be some standard to
provent gross oversubscription.

Say you have a fixed wirelss tower with enough spectrum to broadcast
40mbps. How do you calculate how many customers at average speed of
15mbps can comfortably fit on this antenna ?

I realise existing ISPs use monthly statistics of 95th percentile to see
how much capacity is used and whether the link has reached saturation
and there should be s stop sell or get more spectrum.

But from a regulatory point of view, in evaluating a bid to serve a
region, the regulator would need rules to establish whether the bidder
will be able to serve the population with whatever solution the bidder

Does the FCC have any such rules in the USA, or are its broadband
deployment subsidies only based on the ISP marketing speeds that meet
the FCC's  definition of "broadband" ? (and no concern about whether
those will be delivered or not).

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