And while I look over this very old, first presentation at stanford that tried to describe codel and fq_codel, I see multiple places that we have since improved.
1) I have fallen back to saying that instead of TCP-friendly, codel is "RTT-friendly". There's not a good definition of this latter phrase. Matt Mathis suggests I use "window friendly" instead, but I try to think of "RTT-friendly" as "waiting long enough for a congestion signal to reach the other side" and entirely outside of a tcp context... could use a harder definition....
2) My waving hands talking about 1/(sqrt(count) being the inverse of tcp's increases has since been dropped. I still wish we had a better graphic explaining what really goes on than I have in that preso, it requires a lot of talking still to explain it....
3) we have sfq and drr based versions of "fq_codel" in ns2. I've long encouraged QFQ's author to try the same thing (and qfq + codel can be easily played with using the debloat script, but you rapidly run out of memory on teeny routers). There is hfsc + codel in freebsd now (as well as their fairq variant that I don't know anything about.) I have a couple variants of codel and fq_codel in patch form and in cerowrt... as well as a pie still in progress...
Shapers are using (htb or hfsc) + fq_codel... in shapers where people were using sfq and/or red before. I frankly do not understand hfsc well enough to say if this is a good idea.