The WAN emulator (wan-emu) is a network research/development toolkit that builds network testbed in a easy, efficient, cheap, and realistic way. It is suitable for conducting switched LAN-to-WAN experiments with delay/loss/jitter emulations. Wan-emu can support 100 simultaneous routes per interface, with each one containing independent impairments and modifiers. Also it can construct asymetric links.

Some vendors, such as PacketStorm, modify Linux kernel (open source) as their platforms and use the same queuing disciplines as those in tc (Traffic Control for Linux), but never do they open their patches. Related vendors are listed at the vendor page.

Many networking researches use the dumbbell (single bottleneck) scenario to perform their simulations. Simulation may be the fatest way to implement their ideas because various conditions, such as link bandwidth, RTT, loss probability, and queuing delay (delay jitter) can be easily specified. However, simulations are often too simplified and ignore some details that may influence the results. Some well-know algorithms, such as TCP congestion control algorithms (Tahoe, Reno, NewReno, Sack, Fack, and Vegas), has a lot of implementations deployed at various operating systems, and has some different assumptions from the original versions, which implements in simulators such as NS, and xkernel. We have no efficient way verifying their effectiveness against their original simulation results. After all, the purpose of networking researches is to deployed their ideas. We thus develop an efficient/cheap/realistic tool to make things easier.

Some companies may also find useful using this tool for developing their products. For example, Zyxel have used wan-emu to test their VoIP solutions and find it useful when customizing delay, loss, and jitter. Merely 4 PCs and wan-emu facilitate the development process of most networking equipments, such as debugging, testing, and benchmarking.

The testbed (see the figure below) consists of cascaded machines with statically configured routes. To emulate multiple competing sources and their sinks, we utilize the IP-aliasing; to emulate the dynamics of the Internet, we write the wan-emu virtual interface driver (a Linux kernel module). We describe them as follows:

We write a Linux kernel virtual network interface card (NIC) device driver to implement the RTT/loss/QueueDelay, together with IP-aliasing and interface-aliasing support, so that a specfied route path can have the desired path properties. In such a way each physical NIC can emulate 100 NICs with different IP addresses attached on them, thus emulating the dumbbell scenario. Each path can have a wan-emu cascaded to characterize the path. This method is verified through the results compared with live-experiment connections from our site to UCLA. Flows through wan-emu resembles the real-life connections in Internet.

If you have any comment or find bugs, please contact .