bionic (8) tc-htb.8.gz

Provided by: iproute2_4.15.0-2ubuntu1.3_amd64 bug

NAME

       HTB - Hierarchy Token Bucket

SYNOPSIS

       tc qdisc ... dev dev ( parent classid | root) [ handle major: ] htb [ default minor-id ]

       tc class ... dev dev parent major:[minor] [ classid major:minor ] htb rate rate [ ceil rate ] burst bytes
       [ cburst bytes ] [ prio priority ]

DESCRIPTION

       HTB is meant as a more understandable and intuitive replacement for the CBQ qdisc in Linux. Both CBQ  and
       HTB  help  you  to  control  the use of the outbound bandwidth on a given link. Both allow you to use one
       physical link to simulate several slower links and to  send  different  kinds  of  traffic  on  different
       simulated  links. In both cases, you have to specify how to divide the physical link into simulated links
       and how to decide which simulated link to use for a given packet to be sent.

       Unlike CBQ, HTB shapes traffic based on the Token Bucket  Filter  algorithm  which  does  not  depend  on
       interface  characteristics  and  so  does  not  need  to  know  the  underlying bandwidth of the outgoing
       interface.

SHAPING ALGORITHM

       Shaping works as documented in tc-tbf (8).

CLASSIFICATION

       Within the one HTB instance many classes may exist. Each of these  classes  contains  another  qdisc,  by
       default tc-pfifo(8).

       When enqueueing a packet, HTB starts at the root and uses various methods to determine which class should
       receive the data.

       In the absence of uncommon configuration options, the process is rather easy.  At each node we  look  for
       an  instruction,  and  then  go to the class the instruction refers us to. If the class found is a barren
       leaf-node (without children), we enqueue the packet there. If it is not yet a leaf node, we do the  whole
       thing over again starting from that node.

       The  following actions are performed, in order at each node we visit, until one sends us to another node,
       or terminates the process.

       (i)    Consult filters attached to the class. If sent to a leafnode, we are done.  Otherwise, restart.

       (ii)   If none of the above returned with an instruction, enqueue at this node.

       This algorithm makes sure that a packet always ends up somewhere, even while you are busy  building  your
       configuration.

       FIXME

QDISC

       The root of a HTB qdisc class tree has the following parameters:

       parent major:minor | root
              This  mandatory  parameter  determines  the  place  of  the HTB instance, either at the root of an
              interface or within an existing class.

       handle major:
              Like all other qdiscs, the HTB can be assigned a handle. Should consist only of  a  major  number,
              followed by a colon. Optional, but very useful if classes will be generated within this qdisc.

       default minor-id
              Unclassified traffic gets sent to the class with this minor-id.

CLASSES

       Classes have a host of parameters to configure their operation.

       parent major:minor
              Place  of  this  class  within  the  hierarchy. If attached directly to a qdisc and not to another
              class, minor can be omitted. Mandatory.

       classid major:minor
              Like qdiscs, classes can be named. The major number must be equal to the major number of the qdisc
              to which it belongs. Optional, but needed if this class is going to have children.

       prio priority
              In  the  round-robin  process, classes with the lowest priority field are tried for packets first.
              Mandatory.

       rate rate
              Maximum rate this class and all its children are guaranteed. Mandatory.

       ceil rate
              Maximum rate at which a class can send, if its parent has bandwidth to  spare.   Defaults  to  the
              configured rate, which implies no borrowing

       burst bytes
              Amount  of  bytes that can be burst at ceil speed, in excess of the configured rate.  Should be at
              least as high as the highest burst of all children.

       cburst bytes
              Amount of bytes that can be burst at 'infinite' speed, in other words, as fast  as  the  interface
              can  transmit them. For perfect evening out, should be equal to at most one average packet. Should
              be at least as high as the highest cburst of all children.

NOTES

       Due to Unix timing constraints, the maximum ceil rate is not infinite and may in fact be  quite  low.  On
       Intel,  there  are  100 timer events per second, the maximum rate is that rate at which 'burst' bytes are
       sent each timer tick.  From this, the minimum burst size for a specified  rate  can  be  calculated.  For
       i386, a 10mbit rate requires a 12 kilobyte burst as 100*12kb*8 equals 10mbit.

SEE ALSO

       tc(8)

       HTB website: http://luxik.cdi.cz/~devik/qos/htb/

AUTHOR

       Martin Devera <devik@cdi.cz>. This manpage maintained by bert hubert <ahu@ds9a.nl>