sent to the emulation server (where the virtual network is simulated). The real packet gets 'modulated' into a simulation packet. The simulation packet gets demodulated into a real packet after experiencing effects of loss, errors, delay, jitter etc., thereby transferring these network effects into the real packet. Thus it is as-if the real packet flowed through a real network but in reality it flowed through the simulated network. Emulation is widely used in the design stage for validating communication networks prior to deployment. List of network simulators There are both free/open-source and proprietary network simulators available. Examples of notable network simulators / emulators include: NS simulator OPNET (Riverbed) NetSim (Tetcos) GloMoSim All of these are open source code editable while some of these are commercial. Uses of network simulators Network simulators provide a cost-effective method for 5G-NR capacity, throughput and latency analysis Network R & D (More than 70% of all Network Research paper reference a network simulator) Defense applications such as HF / UHF / VHF Radio based MANET Radios, Tactical data links etc. IOT, VANET simulations UAV network/drone swarm communication simulation Machine Learning: Testing ML algorithms for optimizing network parameters, generating synthetic data training ML algorithms on networks Education: Online courses, Lab experimentation, and R & D. Most universities use a network simulator for teaching / R & D since it is too expensive to buy hardware equipment There are a wide variety of network simulators, ranging from the very simple to the very complex. Minimally, a network simulator must enable a user to Model the network topology specifying the nodes on the network and the links between those nodes Model the application flow (traffic) between the nodes Providing network performance metrics as output Visualization of the packet flow Technology/protocol evaluation and device designs Logging of packet/events for drill-down analyses/debugging See also Network emulation Traffic generation model References Computer networking Telecommunications engineering Computer network analysis Simulation Military radio systems