netem and iproute2 with tc

traffic control of tc in linux and netem

Test

	tc qdisc change dev eth0 root netem loss 10% delay 100ms alpine:~# tc qdisc show qdisc netem 8003: dev eth0 root refcnt 2 limit 1000 delay 100ms loss 10%
	sudo -i for i in {1..10}; do echo "Ping attempt $i:"; ping -c 100 -f -q 8.8.8.8; echo -e "\n"; done
Result
on Alpine

add package	apk update apk add iproute2
	apk for alpine based on busybox
kernel module
load	modprobe sch_netem modprobe cls_u32
check	lsmod \| grep netem
permanent	Not needed !!!
create file	vi /etc/local.d/netem.start tc qdisc change dev eth0 root netem xxxxxxxx
	chmod +x /etc/local.d/netem.start rc-update add local
latency
+ 100 ms	tc qdisc add dev eth0 root netem delay 100ms
remote it	tc qdisc del dev eth0 root
packet loss
+ 10%	tc qdisc add dev eth0 root netem loss 10%
	tc qdisc change dev eth0 root netem loss 10%
	tc qdisc del dev eth0 root
duplication
	sudo tc qdisc add dev eth0 root netem duplicate 10%

reordering
	sudo tc qdisc add dev eth0 root netem reorder 25% 50%
	`reorder 25%`: Specifies that 25% of packets will be reordered. `50%`: Correlation value, meaning that once reordering starts, there is a 50% chance it continues.
show
	alpine:~# tc qdisc show qdisc noqueue 0: dev lo root refcnt 2 qdisc netem 8001: dev eth0 root refcnt 2 limit 1000 loss 10% qdisc pfifo_fast 0: dev eth1 root refcnt 2 bands 3 priomap 1 2 2 2 1 2 0 0 1 1 1 1 1 1 1 1
	`qdisc netem 8001: dev eth0 root refcnt 2 limit 1000 loss 10%` `qdisc netem`: A qdisc implementing network emulation. This is commonly used to simulate network conditions like delay, loss, duplication, or reordering. `8001:`: A unique handle identifying this qdisc. `dev eth0`: Applied to the `eth0` interface. `root`: This is the root qdisc for the `eth0` interface. `refcnt 2`: Two users or instances depend on this qdisc. `limit 1000`: Specifies the maximum number of packets that can be queued. `loss 10%`: Simulates a 10% packet loss rate on traffic passing through `eth0`.
	qdisc pfifo_fast 0: dev eth1 root refcnt 2 bands 3 priomap 1 2 2 2 1 2 0 0 1 1 1 1 1 1 1 1 `qdisc pfifo_fast`: A default qdisc for many Linux setups, implementing a priority FIFO (First In, First Out) queue. `0:`: A handle identifying this qdisc. `dev eth1`: Applied to the `eth1` interface. `root`: This is the root qdisc for the `eth1` interface. `refcnt 2`: Two users or instances rely on this qdisc. `bands 3`: Traffic is divided into 3 bands (queues), each with a different priority. ( Band 0=HightP, 1=MPriority and 2=LowP ) `priomap 1 2 2 2 1 2 0 0 1 1 1 1 1 1 1 1`: Defines how packets are classified into these bands based on their Type of Service (ToS) field. Lower-priority packets are placed in higher-numbered bands, and higher-priority packets (like VoIP) are placed in lower-numbered bands. Each number corresponds to a ToS value (0–7) and maps it to one of the priority bands: `0`: Band 1 (lower priority) `1`: Band 2 (medium priority) `2`: Band 2 (medium priority) `3`: Band 2 (medium priority) `4`: Band 1 (lower priority) `5`: Band 2 (medium priority) `6`: Band 0 (high priority) `7`: Band 0 (high priority)

netem and iproute2 with tc

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