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       pfifo_fast - three-band first in, first out queue


       pfifo_fast is the default qdisc of each interface.

       Whenever an interface is created, the pfifo_fast qdisc is automatically
       used as a queue. If another qdisc is attached, it preempts the  default
       pfifo_fast,  which  automatically  returns to function when an existing
       qdisc is detached.

       In this sense this qdisc is magic, and unlike other qdiscs.


       The algorithm is very similar to that of the classful tc-prio(8) qdisc.
       pfifo_fast is like three tc-pfifo(8) queues side by side, where packets
       can be enqueued in any of the  three  bands  based  on  their  Type  of
       Service bits or assigned priority.

       Not  all  three  bands  are  dequeued simultaneously - as long as lower
       bands have traffic, higher bands are never dequeued. This can  be  used
       to prioritize interactive traffic or penalize ’lowest cost’ traffic.

       Each   band   can  be  txqueuelen  packets  long,  as  configured  with
       ifconfig(8) or ip(8).  Additional packets coming in  are  not  enqueued
       but are instead dropped.

       See tc-prio(8) for complete details on how TOS bits are translated into


              The  length  of  the  three  bands  depends  on  the   interface
              txqueuelen, as specified with ifconfig(8) or ip(8).


       Does  not maintain statistics and does not show up in tc qdisc ls. This
       is because it is the automatic default in the absence of  a  configured




       Alexey N. Kuznetsov, <>

       This manpage maintained by bert hubert <>