Please don't confuse latency (ping) for bandwidth

[Christopher Chavez]

In https://trac.macports.org/ticket/60509 it is explained that MacPorts
uses pings to find nearby servers, and it is claimed nearby servers will
likely be the fastest.

I'm not a network engineer, but can say this claim is a myth. The
purpose of ping is to measure latency, not bandwidth. Yes, sufficiently
low bandwidth will increase ping time. But measuring bandwidth directly
involves something else besides pings, such as transferring a
sufficiently large amount of data and timing how long it takes to do so.

I'm fine with MacPorts claiming to use pings to find nearby servers, but
it should not make or repeat the claim that doing so will do a good job
of finding the fastest server.


Anecdote: for some time, even though I typically use a 60Mbps+ Internet
connection (Spectrum) and live ~100km (>30ms) away from the MacPorts
servers in Austin, TX, I've opted to not use the UT Austin servers
(~1MiBps) because other MacPorts servers such as ykf.ca.*.macports.org
(>60ms away) are far faster (~6MiBps, or about as fast as my connection
can go). I've also configured MacPorts to prefer downloading distfiles
from often-faster CDNs for projects on SourceForge, etc., even though
they may be several times farther away than my regional MacPorts
distfile mirror, and some of which aren't pingable. (I wonder if
MacPorts should even be in the business of defeating the purpose of
these CDNs, but I would expect to be told MacPorts has learned to
distrust upstream projects with hosting distfiles properly.)


Christopher A. Chavez