The article uses the term "CCAs" without ever defining it. I followed the links, and googled it, with no useful result.

What is a CCA in this context?

a Congestion Control Algorithm -- which uses various signals (mostly dropped packets) to try to estimate the available bandwidth and avoid network connection.

Thanks! And to @einsteinx2 and @rp8yxmdmr too.

There are so many overlapping TLA we should have moved to 4 letters long time ago.

Twas ever thus.

There was the proposed eTLA namespace extension...

https://www.catb.org/jargon/html/T/TLA.html

After some searching apparently it means “congestion control algorithm”. Definitely should have been defined in the article, especially since they have a whole section dedicated to explaining what it is.

Congestion Control Algorithms