Free Network Simulator

[macrules34]

I’ve been looking for a free network in-line simulator software. I was thinking of simulating the distance between two cities, say Boston to New York City. Something that can be used with 1,10,40gb hardware. I remember using something at my previous job that was installed on a server and used the nic‘s that were installed on the server to simulate the distance.

I have tried googling this but only come up with trials or an appliance.

 

[mattventura]

`netem` maybe? There's some examples here. It should work to just set up both interfaces as a bridge and apply the delay to both of them.

 

[macrules34]

Are there any others?

The one I used (almost 10 years ago) that booted off a CD and you had to set it up every time the server rebooted.

 

[oneplane]

You're looking for a traffic shaper (like the 'tc' program). This can be done at multiple layers, like layer 2 or layers 3 for example.
Using netem as mentioned by matt, you can do all sorts of cool things.

A quick rip at Google gives this:

# create a bridge
sudo brctl addbr br0

# add two interfaces
sudo brctl addif br0 eth1
sudo brctl addif br0 eth2

# bring the bridge up
sudo ip link set dev br0 up

# add a delay to pretend to have a long distance link
sudo tc qdisc add dev br0 root netem delay 45ms

Some jitter for extra fun:

# Add jitter with a range of 5ms to the existing delay of 45ms
sudo tc qdisc add dev br0 parent 1:1 handle 10: netem delay 45ms 5ms

Maybe add some bandwidth limits

# Limit bandwidth to 1 Mbps with a burst of 100KB
sudo tc qdisc add dev br0 parent 10:1 handle 20: tbf rate 1mbit burst 100kbit latency 300ms

The tc program has been around for decades, so it's possible you had some sort of bootable disk that contained a GUI or TUI to control it.

 

[macrules34]

Ohh okay thanks for the clarification.

 

[nexox]

Bear in mind that by default netem will only queue 1000 packets, so you can easily cause yourself some accidental packet loss at higher latency and throughput combinations if you don't set the qlen (or something like that) value higher.

 

[macrules34]

The one I was looking for is WANem.

WANEM : The Wide Area Network Emulator

WANem is a Wide Area Netwrok emulator designed by Performance Engineering Research Centre, TATA Consultancy Services, Mumbai.

wanem.sourceforge.net

 

[piranha32]

I noticed this list today in my HN feed. Maybe will be helpful for someone browsing this thread: Twenty-five open-source network emulators and simulators you can use in 2023