[VoiceOps] Maximum latency

[Alex Balashov]

What is it that makes people think you need a special application or
tool to do these things?

Here's my default gateway on my home LAN:

sasha at mouse ~> ping -c 5 172.30.105.1
PING 172.30.105.1 (172.30.105.1) 56(84) bytes of data.
64 bytes from 172.30.105.1: icmp_seq=1 ttl=64 time=0.238 ms
64 bytes from 172.30.105.1: icmp_seq=2 ttl=64 time=0.618 ms
64 bytes from 172.30.105.1: icmp_seq=3 ttl=64 time=0.457 ms
64 bytes from 172.30.105.1: icmp_seq=4 ttl=64 time=0.474 ms
64 bytes from 172.30.105.1: icmp_seq=5 ttl=64 time=0.382 ms

--- 172.30.105.1 ping statistics ---
5 packets transmitted, 5 received, 0% packet loss, time 4052ms
rtt min/avg/max/mdev = 0.238/0.433/0.618/0.126 ms

And here's my default gateway on my home LAN with 300 ms of latency
"injected":

sasha at mouse ~> sudo tc qdisc add dev enp1s0 root netem delay 300ms

sasha at mouse ~> ping -c 5 172.30.105.1
PING 172.30.105.1 (172.30.105.1) 56(84) bytes of data.
64 bytes from 172.30.105.1: icmp_seq=1 ttl=64 time=300 ms
64 bytes from 172.30.105.1: icmp_seq=2 ttl=64 time=300 ms
64 bytes from 172.30.105.1: icmp_seq=3 ttl=64 time=300 ms
64 bytes from 172.30.105.1: icmp_seq=4 ttl=64 time=301 ms
64 bytes from 172.30.105.1: icmp_seq=5 ttl=64 time=300 ms

--- 172.30.105.1 ping statistics ---
5 packets transmitted, 5 received, 0% packet loss, time 4005ms
rtt min/avg/max/mdev = 300.841/300.902/301.038/0.605 ms

And here's 300ms latency +/- variability of 40ms:

sasha at mouse ~> sudo tc qdisc add dev enp1s0 root netem delay 300ms 40ms
sasha at mouse ~> ping -c 5 172.30.105.1
PING 172.30.105.1 (172.30.105.1) 56(84) bytes of data.
64 bytes from 172.30.105.1: icmp_seq=1 ttl=64 time=299 ms
64 bytes from 172.30.105.1: icmp_seq=2 ttl=64 time=316 ms
64 bytes from 172.30.105.1: icmp_seq=3 ttl=64 time=324 ms
64 bytes from 172.30.105.1: icmp_seq=4 ttl=64 time=321 ms
64 bytes from 172.30.105.1: icmp_seq=5 ttl=64 time=326 ms

--- 172.30.105.1 ping statistics ---
5 packets transmitted, 5 received, 0% packet loss, time 4002ms
rtt min/avg/max/mdev = 299.411/317.749/326.472/9.706 ms

And here's back to normal:

[root at mouse ~]# tc qdisc del dev enp1s0 root netem
[root at mouse ~]# ping 172.30.105.1
PING 172.30.105.1 (172.30.105.1) 56(84) bytes of data.
64 bytes from 172.30.105.1: icmp_seq=1 ttl=64 time=0.342 ms
^C
--- 172.30.105.1 ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 0.342/0.342/0.342/0.000 ms

And here's "loss insertion" of 5%:

sasha at mouse ~> sudo tc qdisc add dev enp1s0 root netem loss 5%
sasha at mouse ~> ping -c 5 172.30.105.1
PING 172.30.105.1 (172.30.105.1) 56(84) bytes of data.
64 bytes from 172.30.105.1: icmp_seq=2 ttl=64 time=0.514 ms
64 bytes from 172.30.105.1: icmp_seq=3 ttl=64 time=0.501 ms
64 bytes from 172.30.105.1: icmp_seq=4 ttl=64 time=0.546 ms
64 bytes from 172.30.105.1: icmp_seq=5 ttl=64 time=0.279 ms

--- 172.30.105.1 ping statistics ---
5 packets transmitted, 4 received, 20% packet loss, time 4056ms
rtt min/avg/max/mdev = 0.279/0.460/0.546/0.105 ms

sasha at mouse ~> ping -c 5 172.30.105.1
PING 172.30.105.1 (172.30.105.1) 56(84) bytes of data.
64 bytes from 172.30.105.1: icmp_seq=1 ttl=64 time=0.732 ms
64 bytes from 172.30.105.1: icmp_seq=2 ttl=64 time=0.471 ms
64 bytes from 172.30.105.1: icmp_seq=3 ttl=64 time=0.474 ms
64 bytes from 172.30.105.1: icmp_seq=4 ttl=64 time=0.334 ms
64 bytes from 172.30.105.1: icmp_seq=5 ttl=64 time=0.367 ms

--- 172.30.105.1 ping statistics ---
5 packets transmitted, 5 received, 0% packet loss, time 4020ms
rtt min/avg/max/mdev = 0.334/0.475/0.732/0.141 ms

No, I'm not that brilliant. I Googled it:

http://stackoverflow.com/questions/614795/simulate-delayed-and-dropped-packets-on-linux

App to inject latency? You people kill me sometimes.

-- Alex

-- 
Alex Balashov | Principal | Evariste Systems LLC

Tel: +1-706-510-6800 / +1-800-250-5920 (toll-free) 
Web: http://www.evaristesys.com/, http://www.csrpswitch.com/