tc-strategy.md

Traffic control (tc)

tc in Linux

In Linux, the traffic control for shaping the flow is implemented by the tc command. See details in tc(8)

shaping strategy in Oasis

Fig 1.1 Traffic shaping strategy

tc example

Target:

• Limit the rate from h0 to h1 to 100Mbit/s
• For direction h1 to h0, add 5% packet loss, 10ms delay.

Topology:

h0 (eth0) --- (eth0) h1

on host h0, set the rate limit on eth0:

tc qdisc add dev eth0 root handle 5: tbf rate 100.0Mbit burst 150kb latency 1ms

on host h1, we create an ifb interface ifb0:

ip link add name ifb0 type ifb
ip link set ifb0 up

Then, redirect the ingress ip traffic from eth0 to ifb0:

tc qdisc add dev eth0 ingress
tc filter add dev h1-eth0 parent ffff: protocol ip u32 match u32 0 0 action mirred egress redirect dev ifb0

Finally, apply the traffic shaping(loss, delay, jitter) on ifb0:

tc qdisc add dev ifb0 root netem loss 5% delay 10ms limit 20000000

In order to have a better simulation result for latency, a larger buffer/queue size is preferred(specified by limit 20000000 in tc command) otherwise tc will drop more packets when buffer is overwhelmed.

tc_rules script

./src/tools/tc_rules.sh can be used to apply or unset the above tc rules for a topology H0-H1.

# run `tc_rules.sh eth0 set` on host H0 to apply the tc rules:
sudo ./src/tools/tc_rules.sh eth0 set

# run `tc_rules.sh eth0 set` on host H1 to apply the tc rules:
sudo ./src/tools/tc_rules.sh eth0 set

To unset the rules, run:

sudo ./src/tools/tc_rules.sh eth0 unset