[Jack-Devel] a detailed explanation of the jack backends?

Heloo everyone,
in my attempt to learn jack audio server as well as possible,
i am stuck at trying to understand the different backends.
sure alsa, oss, dummy and net are all self -explanatory

but coreaudio? sun? freebob? firewire? portaudio?

things are messed up in my head and there doesn't seem to be a list stating
where should each be used.. and their advantages and differences...

for example. if alsa controls the hw , why do you need portaudio in linux?
portaudio uses alsa either way right?
coreaudio is the "alsa" for macOS?

could someone provide some links or info ?

Thank you all :)

PS: why isn't the net backend visible in qjackctl?

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