HFSC(8)                              Linux                             HFSC(8)

       HFSC - Hierarchical Fair Service Curve's control under linux

       tc qdisc add ... hfsc [ default CLASSID ]

       tc class add ... hfsc [ [ rt SC ] [ ls SC ] | [ sc SC ] ] [ ul SC ]

       rt : realtime service curve
       ls : linkshare service curve
       sc : rt+ls service curve
       ul : upperlimit service curve

       o at least one of rt, ls or sc must be specified
       o ul can only be specified with ls or sc

       SC := [ [ m1 BPS ] d SEC ] m2 BPS
              m1 : slope of the first segment
              d  : x-coordinate of intersection
              m2 : slope of the second segment

       SC := [ [ umax BYTE ] dmax SEC ] rate BPS
              umax : maximum unit of work
              dmax : maximum delay
              rate : rate

       For  description  of  BYTE,  BPS  and SEC - please see UNITS section of

       HFSC qdisc has only one optional parameter - default. CLASSID specifies
       the  minor part of the default classid, where packets not classified by
       other means (e.g. u32 filter, CLASSIFY  target  of  iptables)  will  be
       enqueued.  If  default  is  not specified, unclassified packets will be

       HFSC class is used to create a class hierarchy for HFSC scheduler.  For
       explanation  of the algorithm, and the meaning behind rt, ls, sc and ul
       service curves - please refer to tc-hfsc(7).

       As you can see in SYNOPSIS, service curve (SC) can be specified in  two
       ways. Either as maximum delay for certain amount of work, or as a band-
       width assigned for certain amount of  time.  Obviously,  m1  is  simply

       Both  m2 and rate are mandatory. If you omit other parameters, you will
       specify linear service curve.

       tc(8), tc-hfsc(7), tc-stab(8)

       Please direct bugreports and patches to: <>

       Manpage created by Michal Soltys (

iproute2                        31 October 2011                        HFSC(8)
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