# Specifying Virtual Network Types in a Load Test Scenario

Visual Studio 2010

The network mix gives you a way to simulate load more realistically in a load test scenario. Load is generated by using a heterogeneous mix of network types instead of one single network type. You create a closer approximation of how end-users interact with your applications.

A network mix specifies the probability of a virtual user running a given network profile. A network profile is a simulation of network bandwidth at the application layer. It does not simulate latency.

When you create a load test, you might want to simulate that load is being generated through more than one type of network connection. The network mix offers several network types, including the following:

• LAN (default)

• 3G

• Cable-DSL-1.5Mbps

• Cable-DSL-768k

• Cable/DSL-384k

• CDMA

• Dial-up 56k

• Intercontinental slow WAN 300 Kbps

• Intercontinental WAN 1.5 Mbps

• Intercontinental WAN 1.5 Mbps

The different networks are simulated. When you choose an option such as Cable-DSL 1.5Mbps, wait times are injected into the test to simulate the selected bandwidth.

The network mix works like other mix options. A network type is selected randomly associated with a virtual user, based on network mix. That user's tests are run using a particular network type, based on the probability you specified in the mix.

After you have specified a network mix, you can add and remove network types. You can also change the distribution of the network mix using the mix control.

The mix control allows you to easily adjust the distribution of networks in a scenario.

## True Network Emulation

Microsoft Visual Studio 2010 uses software-based true network emulation for all test types including load tests. True network emulation simulates network conditions by direct manipulation of the network packets. The true network emulator can emulate the behavior of both wired and wireless networks by using a reliable physical link, such as an Ethernet. The following network attributes are incorporated into true network emulation:

• Round-trip time over the network (latency)

• The amount of available bandwidth

• Queuing behavior

• Packet loss

• Reordering of packets

• Error propagations.

True network emulation also provides flexibility in filtering network packets based on IP addresses or protocols such as TCP, UDP, and ICMP.

True network emulation can be used by network-based application developers and testers to emulate a desired test environment, assess performance, predict the impact of change, or make decisions about technology optimization. When compared to hardware test beds, true network emulation is a much cheaper and more flexible solution.

Associated Topics

Specifying network mix: When you first create a load test, you specify settings for the load test in the New Load Test Wizard. In the New Load Test Wizard, you choose networks to add to the initial scenario. After you have added networks to the scenario, you specify the network mix for the scenario.

Adding and removing virtual networks in a scenario: You can add and remove virtual networks from your scenario.