# phpman > man > tc-hfsc(8)

[HFSC(8)](https://www.chedong.com/phpMan.php/man/HFSC/8/markdown)                                         Linux                                        [HFSC(8)](https://www.chedong.com/phpMan.php/man/HFSC/8/markdown)



## NAME
       HFSC - Hierarchical Fair Service Curve's control under linux

## SYNOPSIS
       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 [**tc**(8)](https://www.chedong.com/phpMan.php/man/tc/8/markdown).

### DESCRIPTION (qdisc)
       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  tar‐
       get  of iptables) will be enqueued. If **default** is not specified, unclassified packets will be
       dropped.

### DESCRIPTION (class)
       HFSC class is used to create a class hierarchy for HFSC scheduler. For explanation of the al‐
       gorithm,  and  the  meaning  behind  **rt**,  **ls**,  **sc**  and  **ul**  service  curves - please refer to
       [**tc-hfsc**(7)](https://www.chedong.com/phpMan.php/man/tc-hfsc/7/markdown).

       As you can see in **SYNOPSIS**, service curve (SC) can be specified in two ways. Either as  maxi‐
       mum  delay for certain amount of work, or as a bandwidth assigned for certain amount of time.
       Obviously, **m1** is simply **umax**/**dmax**.

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

## SEE ALSO
       [**tc**(8)](https://www.chedong.com/phpMan.php/man/tc/8/markdown), [**tc-hfsc**(7)](https://www.chedong.com/phpMan.php/man/tc-hfsc/7/markdown), [**tc-stab**(8)](https://www.chedong.com/phpMan.php/man/tc-stab/8/markdown)

       Please direct bugreports and patches to: <<netdev@vger.kernel.org>>

## AUTHOR
       Manpage created by Michal Soltys (<soltys@ziu.info>)



iproute2                                   31 October 2011                                   [HFSC(8)](https://www.chedong.com/phpMan.php/man/HFSC/8/markdown)