Net-Modeler

This is an extremely alpha version of a replacement for ModelNet, which is intended to be able to emulate arbitrary network topologies, including their bandwidth and delays.

Why replace ModelNet?

ModelNet is an incredibly useful research tool which unfortunately, as with most things of its ilk, has become tired and crufty. It will, as far as I can tell, only run on FreeBSD 6.3, which prevents use of more modern operating systems. This is important because more modern operating systems have modern network drivers, and thus can support better technology.

How does it work?

Essentially Net-Modeler uses the Netfilter hooks built into modern versions of Linux to yank 'tagged' packets out of the kernels network stack, delay them for a particular period of time, then reinsert them into the network stack.

Try it out

You're welcome to download and try out the current state of affairs. It will almost certainly cause kernel panics so do it in a VM.

# Dependencies 
$ sudo apt-get install build-essential
$ sudo apt-get install linux-kernel-headers-$(uname -r)

# Grab it
$ git clone https://github.com/cwacek/net-modeler.git
$ cd net-modeler

$ # Build it
$ make
$ make module-install

The module is now installed and running. Now you need to configure a topology. This works in a couple of steps:

1. Register a model defining the name of the topology and the number of nodes and links it will have.
2. Register hops which define the characteristics of the link between two virtual points.
3. Register paths which define how IP addresses are connected using those hops.

There's a tool to do just this:

$ cd tools/net-modeler-ctrl

$ # Register a model with 4 hops and 3 paths called 'Test'
$ python net_modeler.py modelinfo set 21 "Test" 4 3

$ # Register two hops with 100KBps bandwidth, 10ms latency, and 
$ # a bufferlength of 100.
$ python net_modeler.py hoptable set 0 100 10 100
$ python net_modeler.py hoptable set 1 100 10 100

$ # Create a path between 10.0.0.1 and 10.0.0.2 using hop 0,
$ # and the reverse using hop 1.
$ python net_modeler.py pathtable set 10.0.0.1 10.0.0.2 0
$ python net_modeler.py pathtable set 10.0.0.2 10.0.0.1 1

You now have links instantiated. You also have to tell the operating system that it should use those IP addresses:

$ sudo ifconfig eth0:1 10.0.0.1
$ sudo ifconfig eth0:2 10.0.0.2

Try it out:

$ ping -I 10.0.0.1 10.0.0.2
PING 10.0.0.2 (10.0.0.2) from 10.0.0.1 : 56(84) bytes of
data.
64 bytes from 10.0.0.2: icmp_req=1 ttl=64 time=19.5 ms
64 bytes from 10.0.0.2: icmp_req=2 ttl=64 time=21.0 ms
64 bytes from 10.0.0.2: icmp_req=3 ttl=64 time=21.0 ms