WAN Emulator

WAN Emulator is a simple console application for Windows based on Windows Packet Filter. It is also known as Long Fat Network (LFN) Emulator which primary task is simulating Long Fat Network behavior over normal Local Area Network by adding packets delays and drops.

System Requirements

WAN Emulator supports the following operating systems:

Windows XPWindows 7Windows 8.1
Windows Server 2003Windows Server 2008 R2Windows Server 2012 R2
Windows VistaWindows 8Windows 10
Windows Server 2008Windows Server 2012Windows Server 2016
Windows 11Windows Server 2019Windows Server 2022

Note: WAN Emulator binaries are built with VC++ 2012 run-time and can’t be used on Windows versions before Windows XP; however, source code can be rebuilt (an example, with Visual Studio 6.0) to support earlier versions of Windows.

How it works

WAN Emulator is a user mode Windows console application based on Windows Packet Filter. It utilizes Windows Packet Filter library to capture packets from the all network interfaces and delays or/and drops selected packets depending on command line parameters.


WAN Emulator executable is included within samples binaries archive available for the download from Windows Packet Filter homepage. The source code alongside other samples is on GitHub.

How to use

Command line:
LFNEMU.EXE idc idt id odc odt od

idc: IncomingDropCount. How many incoming packets will be dropped in a row.
idt: IncomingDropThreshold. Incoming packets that will not be dropped.
id: IncomingDelay. How long incoming packets will be delayed, in ms.
idc: OutgoingDropCount. How many outgoing packets will be dropped in a row.
idt: OutgoingDropThreshold. Outgoing packets that will not be dropped.
od: OutgoingDelay. How long outgoing packets will be delayed, in ms.
All parameters are required. A zero (0) disables the function

Example: LFNEMU 2 8 0 0 0 100.

This setting will drop to 2 incoming packets, then 8 will be let through. All outgoing packets will be delayed 100 ms.

Price & licensing

Freeware for personal (non-commercial), or educational (including non-profit organization) use.


WAN Emulator software is supplied AS-IS, without warranties of any kind.