> > With tongue in cheek, one could say that measured instantaneously, the > load on a link is always either zero or 100% link rate... >
Actually, that's a first-class observation ! On Thu, Aug 13, 2020 at 12:00 PM Simon Leinen <simon.lei...@switch.ch> wrote: > 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.ti...@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. > > -- Ing. Etienne-Victor Depasquale Assistant Lecturer Department of Communications & Computer Engineering Faculty of Information & Communication Technology University of Malta Web. https://www.um.edu.mt/profile/etiennedepasquale