Linux QOS and monitoring

I implemented QOS for inter-office phone calls for a client today using tc and diffserv. The phones and phone systems were configured by the supplier to set “Diffserv 46”, as their technician called it, which is also known as the EF PHB, or Expedited Forwarding Per-Hop Behaviour. This was made slightly trickier by having to re apply the DSCP on outbound packets due to tunnel traversal. In the end I decided it was easier to use iptables to do this, rather than trying to get tc to do it via dsmark:

[code] /sbin/iptables -t mangle -A OUTPUT -d a.b.c.d -j DSCP –set-dscp-class EF
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Actually applying the shaping is relatively straight forward using dsmark and tcindex:[code]
#!/bin/sh
# Create root DiffServ qdisc, attach to proper network interface
# This also uses any existing DSCP flags within the packet as the tcindex
tc qdisc add dev eth2 handle 1:0 root dsmark indices 64 set_tc_index
tc filter add dev eth2 parent 1:0 protocol ip prio 1 tcindex mask 0xfc shift 2
#
# Create class-based queuing discipline to hold the two classes
tc qdisc add dev eth2 parent 1:0 handle 2:0 cbq bandwidth 10Mbit cell 8 avpkt 1000 mpu 64
#
#Create EF class, create queuing discpline for EF, create filters
tc class add dev eth2 parent 2:0 classid 2:1 cbq bandwidth 10Mbit rate 5Mbit avpkt 40000 prio 1 bounded isolated allot 1514 weight 1 maxburst 30
tc qdisc add dev eth2 parent 2:1 tbf rate 5Mbit burst 2Mbit limit 5Mbit
tc filter add dev eth2 parent 2:0 protocol ip prio 1 handle 0x2e tcindex classid 2:1 pass_on
#
# Create BE class, create queuing discipline for BE, create filters
tc class add dev eth2 parent 2:0 classid 2:2 cbq bandwidth 10Mbit rate 3Mbit avpkt 1000 prio 7 allot 1514 weight 1 maxburst 21 borrow split 2:0 defmap 0xffff
tc qdisc add dev eth2 parent 2:2 red limit 50Kbit min 10Kbit max 30Kbit burst 20 avpkt 1000 bandwidth 3Mbit probability 0.4
tc filter add dev eth2 parent 2:0 protocol ip prio 2 handle 0 tcindex mask 0 classid 2:2 pass_on
[/code]

I then decided I needed a way to monitor whether this was actually working. A quick google search unveiled http://www.docum.org/docum.org/monitor/, which had a couple of different tc monitors. The author states he is no longer working on them, but they work well enough, and the iproute2+tc suite hasn’t exactly changed much lately anyway
[code]
./monitor_tc_top_bis.pl
18:52:18 up 30 min, 3 users, load average: 0.10, 0.08, 0.08
Interval Monitor Monitor Total
Dev Classid Priority Speed Bytes Speed Bytes Comment
——————————————————————————–
eth2 2: N/A 64.18Kbps 2.47MB 36.69Kbps N/A
eth2 2:1 1 6.03Kbps 86.27KB 1.25Kbps N/A
eth2 2:2 7 64.18Kbps 2.47MB 36.69Kbps N/A
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