Network emulation 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.
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Network 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 incorporates 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 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.