[LARTC] English translation of article on HFSC

[Patrick McHardy]

Hi Martin,

first of all: thanks alot for your efforts (and sorry for a bit of
silence from my side, I'm busy as usual ..)

Martin A. Brown wrote:
> Greetings Nickola!
> 
>  : Just a question - wasn't Mr. Kenjiro Cho [1] the original writer 
>  : of the HFSC queueing discipline, following the work of Mr. Hui 
>  : Zhang [2], et al.?
> 
> <snip/>
> 
> In fact, I was probably not quite exact enough in my introduction.  
> I meant this remark to be understood specifically with regard to the 
> Linux HFSC implementation.
> 
> You are quite correct to allude to the *BSD altq HFSC implementation 
> which preceded Patrick McHardy's work.
> 
> Thanks for the point of clarification, Nickola.  Other history on 
> HFSC would probably need to be introduced by somebody who knows this 
> topic better than I do.


The first implementation was written by Hui Zhang and his colleagues
at Carnegie Mellon. It wasn't very pretty and IIRC not implemented in
a very efficient way. Kenjiro Cho reimplemented it while he was at
Carnegie Mellon, and incorporated his implementation into ALTQ. It
was later enhanced by Oleg Cherevko, who added upper-limit curves
for non-work-conserving mode. This is the implementation used in
the various BSDs. The Linux version if a port of the ALTQ version,
but includes a few enhancements like rbtrees instead of linked lists
and a couple of O(n) algorithms replaced by O(1) variants, which
increases scalability with many classes greatly.

Hope that clears up this history :)