man/man8/tc-fq_codel.8

   1 .TH FQ_CoDel 8 "4 June 2012" "iproute2" "Linux"
   2 .SH NAME
   3 CoDel \- Fair Queuing (FQ) with Controlled Delay (CoDel)
   4 .SH SYNOPSIS
   5 .B tc qdisc ... fq_codel
   6 [
   7 .B limit
   8 PACKETS ] [
   9 .B flows
  10 NUMBER ] [
  11 .B target
  12 TIME ] [
  13 .B interval
  14 TIME ] [
  15 .B quantum
  16 BYTES ] [
  17 .B ecn
  18 |
  19 .B noecn
  20 ]
  21
  22 .SH DESCRIPTION
  23 FQ_Codel (Fair Queuing Controlled Delay) is queuing discipline that combines Fair
  24 Queuing with the CoDel AQM scheme. FQ_Codel uses a stochastic model to classify
  25 incoming packets into different flows and is used to provide a fair share of the
  26 bandwidth to all the flows using the queue. Each such flow is managed by the
  27 CoDel queuing discipline. Reordering within a flow is avoided since Codel
  28 internally uses a FIFO queue.
  29
  30 .SH PARAMETERS
  31 .SS limit
  32 has the same semantics as
  33 .B codel
  34 and is the hard limit on the real queue size.
  35 When this limit is reached, incoming packets are dropped. Default is 10240
  36 packets.
  37
  38 .SS flows
  39 is the number of flows into which the incoming packets are classified. Due to
  40 the stochastic nature of hashing, multiple flows may end up being hashed into
  41 the same slot. Newer flows have priority over older ones. This parameter can be
  42 set only at load time since memory has to be allocated for the hash table.
  43 Default value is 1024.
  44
  45 .SS target
  46 has the same semantics as
  47 .B codel
  48 and is the acceptable minimum
  49 standing/persistent queue delay. This minimum delay is identified by tracking
  50 the local minimum queue delay that packets experience. Default value is 5ms.
  51
  52 .SS interval
  53 has the same semantics as
  54 .B codel
  55 and is used to ensure that the measured minimum delay does not become too stale.
  56 The minimum delay must be experienced in the last epoch of length .B interval.
  57 It should be set on the order of the worst-case RTT through the bottleneck to
  58 give endpoints sufficient time to react. Default value is 100ms.
  59
  60 .SS quantum
  61 is the number of bytes used as 'deficit' in the fair queuing algorithm. Default
  62 is set to 1514 bytes which corresponds to the Ethernet MTU plus the hardware
  63 header length of 14 bytes.
  64
  65 .SS ecn | noecn
  66 has the same semantics as
  67 .B codel
  68 and can be used to mark packets instead of dropping them. If
  69 .B ecn
  70 has been enabled,
  71 .B noecn
  72 can be used to turn it off and vice-a-versa. Unlike
  73 .B codel, ecn
  74 is turned on by default.
  75
  76 .SH EXAMPLES
  77 #tc qdisc add   dev eth0 root fq_codel
  78 .br
  79 #tc -s qdisc show
  80 .br
  81 qdisc fq_codel 8002: dev eth0 root refcnt 2 limit 10240p flows 1024 quantum 1514
  82  target 5.0ms interval 100.0ms ecn
  83    Sent 428514 bytes 2269 pkt (dropped 0, overlimits 0 requeues 0)
  84    backlog 0b 0p requeues 0
  85     maxpacket 256 drop_overlimit 0 new_flow_count 0 ecn_mark 0
  86     new_flows_len 0 old_flows_len 0
  87
  88 #tc qdisc add dev eth0 root fq_codel limit 2000 target 3ms interval 40ms noecn
  89 .br
  90 #tc -s qdisc show
  91 .br
  92 qdisc fq_codel 8003: dev eth0 root refcnt 2 limit 2000p flows 1024 quantum 1514
  93 target 3.0ms interval 40.0ms
  94  Sent 2588985006 bytes 1783629 pkt (dropped 0, overlimits 0 requeues 34869)
  95  backlog 0b 0p requeues 34869
  96   maxpacket 65226 drop_overlimit 0 new_flow_count 73 ecn_mark 0
  97   new_flows_len 1 old_flows_len 3
  98
  99
 100 .SH SEE ALSO
 101 .BR tc (8),
 102 .BR tc-codel (8),
 103 .BR tc-red (8)
 104
 105 .SH AUTHORS
 106 FQ_CoDel was implemented by Eric Dumazet. This manpage was written
 107 by Vijay Subramanian. Please report corrections to the Linux Networking
 108 mailing list <netdev@vger.kernel.org>.