1 2 IFB is intended to replace IMQ. 3 Advantage over current IMQ; cleaner in particular in in SMP; 4 with a _lot_ less code. 5 6 Known IMQ/IFB USES 7 ------------------ 8 9 As far as i know the reasons listed below is why people use IMQ. 10 It would be nice to know of anything else that i missed. 11 12 1) qdiscs/policies that are per device as opposed to system wide. 13 IFB allows for sharing. 14 15 2) Allows for queueing incoming traffic for shaping instead of 16 dropping. I am not aware of any study that shows policing is 17 worse than shaping in achieving the end goal of rate control. 18 I would be interested if anyone is experimenting. 19 20 3) Very interesting use: if you are serving p2p you may wanna give 21 preference to your own localy originated traffic (when responses come back) 22 vs someone using your system to do bittorent. So QoSing based on state 23 comes in as the solution. What people did to achive this was stick 24 the IMQ somewhere prelocal hook. 25 I think this is a pretty neat feature to have in Linux in general. 26 (i.e not just for IMQ). 27 But i wont go back to putting netfilter hooks in the device to satisfy 28 this. I also dont think its worth it hacking ifb some more to be 29 aware of say L3 info and play ip rule tricks to achieve this. 30 --> Instead the plan is to have a contrack related action. This action will 31 selectively either query/create contrack state on incoming packets. 32 Packets could then be redirected to ifb based on what happens -> eg 33 on incoming packets; if we find they are of known state we could send to 34 a different queue than one which didnt have existing state. This 35 all however is dependent on whatever rules the admin enters. 36 37 At the moment this 3rd function does not exist yet. I have decided that 38 instead of sitting on the patch for another year, to release it and then 39 if theres pressure i will add this feature. 40 41 An example, to provide functionality that most people use IMQ for below: 42 43 -------- 44 export TC="/sbin/tc" 45 46 $TC qdisc add dev ifb0 root handle 1: prio 47 $TC qdisc add dev ifb0 parent 1:1 handle 10: sfq 48 $TC qdisc add dev ifb0 parent 1:2 handle 20: tbf rate 20kbit buffer 1600 limit 3000 49 $TC qdisc add dev ifb0 parent 1:3 handle 30: sfq 50 $TC filter add dev ifb0 protocol ip pref 1 parent 1: handle 1 fw classid 1:1 51 $TC filter add dev ifb0 protocol ip pref 2 parent 1: handle 2 fw classid 1:2 52 53 ifconfig ifb0 up 54 55 $TC qdisc add dev eth0 ingress 56 57 # redirect all IP packets arriving in eth0 to ifb0 58 # use mark 1 --> puts them onto class 1:1 59 $TC filter add dev eth0 parent ffff: protocol ip prio 10 u32 \ 60 match u32 0 0 flowid 1:1 \ 61 action ipt -j MARK --set-mark 1 \ 62 action mirred egress redirect dev ifb0 63 64 -------- 65 66 67 Run A Little test: 68 69 from another machine ping so that you have packets going into the box: 70 ----- 71 [root@jzny action-tests]# ping 10.22 72 PING 10.22 (10.0.0.22): 56 data bytes 73 64 bytes from 10.0.0.22: icmp_seq=0 ttl=64 time=2.8 ms 74 64 bytes from 10.0.0.22: icmp_seq=1 ttl=64 time=0.6 ms 75 64 bytes from 10.0.0.22: icmp_seq=2 ttl=64 time=0.6 ms 76 77 --- 10.22 ping statistics --- 78 3 packets transmitted, 3 packets received, 0% packet loss 79 round-trip min/avg/max = 0.6/1.3/2.8 ms 80 [root@jzny action-tests]# 81 ----- 82 Now look at some stats: 83 84 --- 85 [root@jmandrake]:~# $TC -s filter show parent ffff: dev eth0 86 filter protocol ip pref 10 u32 87 filter protocol ip pref 10 u32 fh 800: ht divisor 1 88 filter protocol ip pref 10 u32 fh 800::800 order 2048 key ht 800 bkt 0 flowid 1:1 89 match 00000000/00000000 at 0 90 action order 1: tablename: mangle hook: NF_IP_PRE_ROUTING 91 target MARK set 0x1 92 index 1 ref 1 bind 1 installed 4195sec used 27sec 93 Sent 252 bytes 3 pkts (dropped 0, overlimits 0) 94 95 action order 2: mirred (Egress Redirect to device ifb0) stolen 96 index 1 ref 1 bind 1 installed 165 sec used 27 sec 97 Sent 252 bytes 3 pkts (dropped 0, overlimits 0) 98 99 [root@jmandrake]:~# $TC -s qdisc 100 qdisc sfq 30: dev ifb0 limit 128p quantum 1514b 101 Sent 0 bytes 0 pkts (dropped 0, overlimits 0) 102 qdisc tbf 20: dev ifb0 rate 20Kbit burst 1575b lat 2147.5s 103 Sent 210 bytes 3 pkts (dropped 0, overlimits 0) 104 qdisc sfq 10: dev ifb0 limit 128p quantum 1514b 105 Sent 294 bytes 3 pkts (dropped 0, overlimits 0) 106 qdisc prio 1: dev ifb0 bands 3 priomap 1 2 2 2 1 2 0 0 1 1 1 1 1 1 1 1 107 Sent 504 bytes 6 pkts (dropped 0, overlimits 0) 108 qdisc ingress ffff: dev eth0 ---------------- 109 Sent 308 bytes 5 pkts (dropped 0, overlimits 0) 110 111 [root@jmandrake]:~# ifconfig ifb0 112 ifb0 Link encap:Ethernet HWaddr 00:00:00:00:00:00 113 inet6 addr: fe80::200:ff:fe00:0/64 Scope:Link 114 UP BROADCAST RUNNING NOARP MTU:1500 Metric:1 115 RX packets:6 errors:0 dropped:3 overruns:0 frame:0 116 TX packets:3 errors:0 dropped:0 overruns:0 carrier:0 117 collisions:0 txqueuelen:32 118 RX bytes:504 (504.0 b) TX bytes:252 (252.0 b) 119 ----- 120 121 You send it any packet not originating from the actions it will drop them. 122 [In this case the three dropped packets were ipv6 ndisc]. 123 124 cheers, 125 jamal 126
