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    Command:

    tc-drr

    
    
    

    SYNOPSIS

           tc qdisc ... add drr [ quantum bytes ]
    
    
    

    DESCRIPTION

           The Deficit Round Robin Scheduler is a classful queuing discipline as a
           more flexible replacement for Stochastic Fairness Queuing.
    
           Unlike SFQ, there are no built-in queues -- you need to add classes and
           then  set up filters to classify packets accordingly.  This can be use-
           ful e.g. for using RED qdiscs with different  settings  for  particular
           traffic. There is no default class -- if a packet cannot be classified,
           it is dropped.
    
    
    

    ALGORITHM

           Each class is assigned a deficit counter, initialized to quantum.
    
           DRR maintains an (internal) ''active'' list of classes whose qdiscs are
           non-empty.  This list is used for dequeuing.  A packet is dequeued from
           the class at the head of the list if the  packet  size  is  smaller  or
           equal  to  the  deficit  counter.   If  the counter is too small, it is
           increased by quantum and the scheduler moves on to the  next  class  in
           the active list.
    
    
    

    PARAMETERS

           quantum
                  Amount  of  bytes a flow is allowed to dequeue before the sched-
                  uler moves to the next class.  Defaults to the MTU of the inter-
                  face. The minimum value is 1.
    
    
    

    EXAMPLE & USAGE

           To attach to device eth0, using the interface MTU as its quantum:
    
           # tc qdisc add dev eth0 handle 1 root drr
    
           Adding two classes:
    
           #  tc  class  add dev eth0 parent 1: classid 1:1 drr # tc class add dev
           eth0 parent 1: classid 1:2 drr
    
           You also need to add at least one filter to classify packets.
    
           # tc filter add dev eth0 protocol .. classid 1:1
    
           Like SFQ, DRR is only useful when it owns the queue --  it  is  a  pure
           scheduler  and  does  not delay packets.  Attaching non-work-conserving
           qdiscs like tbf to it does not make sense -- other qdiscs in the active
           tc  filter  add  ..   protocol   ip   ..   $handle   flow   hash   keys
           src,dst,proto,proto-src,proto-dst divisor 1024 perturb 10
    
    
    

    SOURCE

           o      M.  Shreedhar  and George Varghese "Efficient Fair Queuing using
                  Deficit Round Robin", Proc. SIGCOMM 95.
    
    
    

    NOTES

           This implementation does not drop packets from  the  longest  queue  on
           overrun, as limits are handled by the individual child qdiscs.
    
    
    

    SEE ALSO

           tc(8), tc-htb(8), tc-sfq(8)
    
    
    

    AUTHOR

           sched_drr was written by Patrick McHardy.
    
    
    

    iproute2 January 2010 TC(8)

    
    
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