There's an overview video here specifically aimed at game developers, but it shows what it's about. Different impairments can be configured for the up and downlink so you could have a really good uplink but a really bad downlink experience, great for seeing how the app handles TCP queuing because the acks don't come back in a timely manner and the overall latency therefore increases! Take a look at the NE-ONE Network Emulator which allows you to configure bandwidth, latency, packet loss, packet reordering, packet duplication, packet fragmentation, network congestion and many more impairments so that you can create real-world network conditions in the lab. You can invoke the ipfw commands directly from the terminal and get the same effects. I've done the same thing by routing network traffic over the Airport and through the ethernet, setting it up so that anything coming over the airport has the same characteristics as whatever I'm trying to emulate. If you happen to be working from a Macintosh, that OS has ipfw built into it by default. Reboot, and you've got yourself a 56K bridge! With firewall_type='/etc/rc.firewall.56k' For just simulating a different IP connection, you could (for example) do the following:Ĭreate a file /etc/rc.firewall.56k which contains the following: ipfw add pipe 1 ip from any to any outĪnd change /etc/rc.conf. In step 5 of the above instructions, you're enabling a firewall.

There's an excellent writeup of setting up a FreeBSD machine to do just this - take your standard old desktop, toss in an additional NIC, and build.

How to use netbalancer 2016