My company is developing a network software and its network stability is very important. So my supervisor want me to set up the testing environment for our QA team.

I can take care of almost everything to set it up except the network latency test. I need to find a tool that can control the network latency but I couldn't able to find one. My supervisor have mentioned that there is a tool which create a virtual NIC to control network latency or something.

Please let me know if you've seen any of network latency control tool or something helpful information.

Thank you..

  • *p.s. - I need a WIN based tool since we only use WIN in the company. – Sam Jun 5 '09 at 6:49
  • Did any of the answers on this question help? serverfault.com/questions/2014/… – Zoredache Jun 5 '09 at 7:25
  • @Zoredache Tmurgent might have a funtion I want. Thank you!! – Sam Jun 5 '09 at 8:50
  • You mention that it has to be a Windows tool, but could you use Linux in a virtual machine running on a Windows box? – Andy May Jun 5 '09 at 12:31

If it has to be windows.. its not going to be easy and free i think. If you got some budget for this, go Shunra. No budget, go linux and use Qdisc.

Ive tried some free linux WAN simulators to emulate 4 hostingsites with delays and bandwidthlimits.. all just crashed with my config so i ended up setting up Qdisc manually.

If you decide to go with the linux option i could assisst in the Qdisc config.

For more opinions youve got a link from Zoredache in you questionpost.

  • I'll look into Shunra. Thank you for information! – Sam Jun 5 '09 at 8:48

Basically, you need a switch/bridge/router, which slows down your traffic. I would strongly recommend to not use a tool on client or server, but between them on your network equipment.

Namely, you need a WAN emulator. These pieces of software let you configure bandwidth, delay/latency and random packet loss. Therefor, you can simulate connections over slow uplinks or just see how your application performs with some delay.

If you have some money to spend for an appliance, have a look at networknightmare's WAN emulator appliances. The free solution I prefer is WANem. It comes with a nice WebGUI (easy to configure) for layer 3 operation, if you need to slow down layer 2 traffic, just create a bridged interface with two network cards.


Marionette may be able to help you out here, and possibly simplify your life with creating other network configurations for testing as well.

  • Thank you for information.. However, I'm not able to run a tool based on linux.. – Sam Jun 5 '09 at 8:47

Somebody ask the same question on Slashdot


If your network software is TCP based TMnetSim Network Simulator from TMurgent Technologies is a great tool to do exactly what you are looking for and best of all it's free. We use it a great deal in development and testing, mainly to introduce delay. Of course it can also simulate packet loss and/or out-of-order delivery of packets. The new version also has packet capturing built in, which can be handy.


Cisco has created a CD-ROM based on NIST NET that, when booted on a pc with two network interfaces, can emulate a WAN connection. I have used this in the past with both physical and VMware virtual machines to simulate long distance links adding latency and limiting speed.

NIST Net by default is used to add latency, bandwidth limitations, packet loss or duplication, and other WAN characteristics on all IP traffic moving between the Ethernet ports of the system, while exclusions to this directive can be added on a per system basis. -- NIST Net WAN Emulation Software Installation and Configuration Note

The NIST Net home page is www-x.antd.nist.gov/nistnet/ and the ISO file for the CD-ROM can be found on cisco.com (wan-bridge_v1.07.iso). An account may be required to download it from cisco.


dummynet and ipfw is what you need. it can also simulate packet % loss for ex.

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