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

   * at least one of rt, ls or sc must be specified
   * 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
   bandwidth 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 (


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