1 .TH FQ_CoDel 8 "4 June 2012" "iproute2" "Linux"
3 CoDel \- Fair Queuing (FQ) with Controlled Delay (CoDel)
5 .B tc qdisc ... fq_codel
23 FQ_Codel (Fair Queuing Controled 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.
32 has the same semantics as
34 and is the hard limit on the real queue size.
35 When this limit is reached, incoming packets are dropped. Default is 10240
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.
46 has the same semantics as
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.
53 has the same semantics as
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.
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.
66 has the same semantics as
68 and can be used to mark packets instead of dropping them. If
72 can be used to turn it off and vice-a-versa. Unlike
74 is turned on by default.
77 #tc qdisc add dev eth0 root fq_codel
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
88 #tc qdisc add dev eth0 root fq_codel limit 2000 target 3ms interval 40ms noecn
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
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>.