Implementation details of altq hfsc scheduler in pf 4.5

RW rwmaillists at
Tue Dec 13 13:15:53 UTC 2011

On Mon, 12 Dec 2011 21:51:39 -0500
Maxim Khitrov wrote:

> I've read everything I could find on the topic of configuring hfsc
> altq in pf (4.5, FreeBSD 9), but I still have no clear idea of how it
> is actually implemented. I even started looking through the source
> code, but that might take a while. My main questions are:
> 1. Difference between 'realtime' and 'linkshare'?

It's about latency, realtime has priority over non-realtime.

> 2. In service curve configuration (m1, d, m2), what is 'd' relative
> to?

It looks like it's a leaky-bucket algorithm. It's not really relative
to anything except for special cases like a traffic step-function.

> 3. Are priorities actually used for anything?

Priority determines which queue is serviced next when more than one is
under its limit.

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