is a technique where the properties of an existing, planned and/or non-ideal network
are simulated in order to assess performance, predict the impact of change, or otherwise optimize technology decision-making.
Methods of emulation
can be accomplished by introducing a device on the LAN
that alters packet flow in a way that imitates the behavior of application traffic in the environment being emulated. This device may be either a general-purpose computer running software
to perform the network emulation or a dedicated emulation device
. The device incorporate a variety of network attributes into its emulation model – including the round-trip time across the network (latency
), the amount of available bandwidth
, a given degree of packet loss
, duplication of packets, reordering packets, and/or the severity of network jitter
. Desktop PCs can be connected to the emulated environment, so that users can experience the performance and behavior of applications in that environment first-hand. Similarly, phones can be connected to the emulated environment so that users can directly assess VoIP
call quality for themselves.
Emulation, simulation and traffic generation
Emulation differs from simulation
in that a network emulator appears to be
a network; end-systems such as computers
can be attached to the emulator and will behave as if they are attached to a network. Network simulators are typically programs which run on a single computer, take an abstract description of the network traffic (such as a flow arrival process) and yield performance statistics (such as buffer occupancy as a function of time).
A network emulator emulates the network which connects end-systems, not the end-systems themselves. Systems which emulate the end-systems are called traffic generators.
- NS-2 is a popular network simulator that can also be used as a limited-functionality emulator. It is currently maintained.
- WANsim is a simple bridged WAN emulator that utilises the Linux NETEM functionality.