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Network simulation vs. emulation: What's the difference?

Network engineers use simulation and emulation to test changes, which ensures reliable post-change performance. Network simulators create models, while emulators mimic networks.

Network engineers can't -- and shouldn't -- always work directly on the production network. To prepare for network changes, network engineers need to test how those changes can affect network function. However, experiments on the production network can result in service problems and create downtime, necessitating the use of network testing labs.

In some cases, engineers test in network labs built with the same equipment used in the production network but not always. When network engineers can't use a real replica of their network, they turn to network simulation and network emulation.

While network simulation and network emulation are similar in that they both replicate network environments, they use different approaches. Additionally, network validation is a subsequent process that ensures the simulated or emulated networks accurately reflect real-world changes in the environment.

What is network simulation?

Network simulation tools create models of a network's full stack of technologies, including network devices, like routers and switches. Network simulation tools configure these models in different methods and deal with different traffic protocols in specified ways.

Simulation tools enable engineers to test network configuration and topology changes, as well as their effect on other devices and application traffic flows. Simulators can touch all network layers, from Layer 1, the physical layer, to Layer 7, the application layer.

Simulators typically create an event queue and then calculate the state of each simulated device, link and data stream as events play out into the network, one after another. For example, the first event might be the arrival of a packet at an edge switch, the second might be a replication of that packet on the upstream link interface for the switch and the third might be a collision at the router.

A queue might populate with completely synthesized events, with events captured from a real-world network or with a mixture of the two. Network simulators determine the state of each network device and the fate of each packet. In addition, they also provide information on link and protocol performance.

What is network emulation?

Network emulation tools are boxes that pretend to be entire physical networks. Systems, often one or two test servers and a test client, connect to emulators to test how applications work when faced with the performance artifacts inherent to any production network.

Areas of analysis network administrators need to test include the following:

  • Latency.
  • Jitter.
  • Packet loss.
  • Congestion.
  • Packet collisions.

These tools touch Layer 1 and Layer 2, the data link layer.

Network engineers and developers can tune the emulation to test against a range of network performance profiles, whether excellent or poor. They can also configure emulators to mimic the characteristics of different kinds of networks, such as internet-based WANs that run on asymmetrical cable links, data centers with low-latency switching or a legacy three-tier network.

Specialized emulator hardware might be necessary to mimic some kinds of network components, such as ultralow-latency data center switches. Different emulators support different kinds of connections, such as copper, like Cat6e, optical fiber or wireless -- usually Wi-Fi, as cellular options like 5G are less common.

Emulation is complementary to simulation, and some simulators include emulators.

Network simulation vs. emulation: Use both for network validation

It's not network simulation versus emulation, but network simulation and emulation. Both processes enable teams to test how changes to a network affect performance.

Network changes include the following:

  • The addition of a new service in the data center.
  • A change to an existing server or service.
  • Network device installation, upgrade or retirement.

Network engineers might also administer changes to fix an existing network problem.

Whatever the reason for the change, the process of testing changes before rolling them out, with or without emulators or simulators, is part of network validation. The other part is the confirmation that the production network behaves and performs as expected after the rollout. The network must operate with speed and reliability after a change has been made.

Network engineers and architects need the right tools to properly design, build and maintain an enterprise network. Network simulators and emulators are a crucial pair of tools that test and validate designs and changes.

John Burke is CTO and principal research analyst with Nemertes Research. With nearly two decades of technology experience, he has worked at all levels of IT, including end-user support specialist, programmer, system administrator, database specialist, network administrator, network architect and systems architect. His focus areas include AI, cloud, networking, infrastructure, automation and cybersecurity.

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