m Taichi writes:
> Just my curiosity. May I ask how we can measure the link capacity
> loading? What does it mean by a 50%, 70%, or 90% capacity loading?
> Load sampled and measured instantaneously, or averaging over a certain
> period of time (granularity)?

Very good question!

With tongue in cheek, one could say that measured instantaneously, the
load on a link is always either zero or 100% link rate...

ISPs typically sample link load in 5-minute intervals and look at graphs
that show load (at this 5-minute sampling resolution) over ~24 hours, or
longer-term graphs where the resolution has been "downsampled", where
downsampling usually smoothes out short-term peaks.

>From my own experience, upgrade decisions are made by looking at those
graphs and checking whether peak traffic (possibly ignoring "spikes" :-)
crosses the threshold repeatedly.

At some places this might be codified in terms of percentiles, e.g. "the
Nth percentile of the M-minute utilization samples exceeds X% of link
capacity over a Y-day period".  I doubt that anyone uses such rules to
automatically issue upgrade orders, but maybe to generate alerts like
"please check this link, we might want to upgrade it".

I'd be curious whether other operators have such alert rules, and what
N/M/X/Y they use - might well be different values for different kinds of
links.
--
Simon.
PS. We use the "stare at graphs" method, but if we had automatic alerts,
    I guess it would be something like "the 95th percentile of 5-minute
    samples exceeds 50% over 30 days".
PPS. My colleagues remind me that we do alert on output queue drops.

> These are questions have bothered me for long. Don't know if I can ask
> about these by the way. I take care of the radio access network
> performance at work. Found many things unknown in transport network.

> Thanks and best regards,
> Taichi

> On Wed, Aug 12, 2020 at 3:54 PM Mark Tinka <mark.tinka@seacom.com> wrote:

>  On 12/Aug/20 09:31, Hank Nussbacher wrote:

>  At what point do commercial ISPs upgrade links in their backbone as well as peering and transit links that are congested?  At 80%
>  capacity?  90%?  95%? 

>  We start the process at 50% utilization, and work toward completing the upgrade by 70% utilization.

>  The period between 50% - 70% is just internal paperwork.

>  Mark.