You can emulate the behavior of a wide variety of network infrastructures in your load testing scenario using the Shunra WAN Emulator. WAN emulation provides the ability to simulate and test the effects of Wide Area Networks on end-user response times and performance prior to deployment.
About WAN Emulation
WAN emulation enables you to accurately test point-to-point performance of WAN-deployed products under real-world network conditions in your test environment. By introducing highly probable WAN effects such as latency, packet loss, link faults, and dynamic routing effects over your LAN, you can characterize many aspects of the WAN cloud and efficiently control your emulation in a single network environment. You can observe the effects of your emulation settings on the network performance in the WAN emulation monitoring reports.
Note: WAN Emulation is only available for load generators running on a Windows platform. The WAN Emulation tab is disabled for load generators running on a UNIX platform.
Setting up the WAN Emulator
To use the Shunra WAN Emulator, you must first install the WAN Emulator Driver on the Load Generator machine from the LoadRunner installation CD.
Configuring the WAN Emulator
Select the WAN Emulation tab to configure WAN emulation settings for your load test from the Controller machine.
Enable WAN Emulation on Load Generator: Select the check box to enable WAN emulation to start automatically on scenario execution.
Set Predefined Profile: Select a profile with predefined latency and packet loss settings. The following profile settings are available:
Latency: Displays a value representing the time, in milliseconds, that it takes an IP packet to cross the WAN. This is usually effected by the geographical distance, the available bandwidth, the network load on the route between the two ends, and whether this is a terrestrial link or not. The default setting is 0ms. To set a latency value manually, move the Latency slider to the desired setting or enter a value in the Latency Value box. The default range is 0-400ms.
Note: To extend the WAN emulation latency range to a maximum of 8000ms, open the wlrun7.ini file in a text editor, and enter the desired maximum value in the following format. For example: [WAN_Emulation] MaxLatency=1000
Packet Loss: Displays a value representing the chance of losing IP packets while data travels through a WAN. Packets can get lost due to link faults or due to extreme network load. The default setting is 1%. To set packet loss manually, move the Packet Loss slider to the desired setting.
Apply All: Applies the WAN emulation settings to all load generators listed in the Load Generators dialog box.
Exclude Hosts: Opens the Exclude Hosts dialog box enabling you to exclude certain host names or IP addresses from the emulated WAN. For a list of situations where hosts should be excluded from the emulated WAN,
Advanced: Opens the WAN Emulation Advanced Options dialog box.
Defaults: Restores the default settings.
Note: You cannot change WAN emulation settings while a load generator is connected. To disconnect a load generator, select the load generator in the Load Generators dialog box, and click Disconnect. The load generator status changes to Down, and you can then change the settings. WAN emulation is disabled if the load generator is Localhost.
Configuring the WAN Emulation Advanced Options
You can set packet reordering, packet duplication, packet fragmentation, bit errors, and link disconnections from the WAN Emulation Advanced Options. To set advanced options, click the Advanced button in the WAN Emulation tab.
Note: By default, all the options are enabled. To adjust an option setting, move the slider to the desired value. The profile values are displayed beneath the setting range.
Packet Reordering: The chance of a packet order changing while it travels through the WAN cloud. The default setting is 1%.
Packet Duplication: The chance of a packet duplication occurring while it travels through the WAN cloud. Count is the number of copies of each packet that will be created when duplication occurs. Default Chance setting is 1%. Default Count setting is 1.
Packet Fragmentation: The chance of a packet fragmentation occurring (due to a short Maximum Transmission Unit) while it travels through the WAN cloud. MTU is the largest size packet or frame (specified in bytes), that can be sent in a packet- or frame-based network such as the internet. Default Chance setting is 1%. Default MTU setting is 512 Bytes.
Bit Errors: The frequency at which the emulator toggles one bit. Bit toggling occurs every time the indicated number of bits has crossed the WAN cloud. Default Chance setting is 100,000 Bits.
Link Disconnection: The chance (average frequency) of a network disconnection occurring while a packet travels through the WAN cloud, and the disconnection time span. Default Chance setting is one disconnection every 256 seconds. Default Duration is 1 second.
Defaults: Restores the default settings.
Excluding Hosts from WAN Emulation
In some situations you may want to exclude certain hosts from the WAN emulation. You can do this by setting the WAN emulator to refrain from affecting traffic to specified hosts. Network traffic which is not affected by the emulation will not suffer any WAN effects and will not be included in the WAN emulation monitoring reports. Examples of situations where you should exclude hosts from an emulated WAN include the following:
Understanding the Exclude Hosts Dialog Box
Select Exclude Hosts from the WAN Emulation tab in the Load Generator Information dialog box to exclude specific hosts from the WAN emulation.
Add: Opens the Add Host dialog box. Enter the name or IP address of the machine you want to exclude from WAN emulation.
Note: You do not need to exclude the Controller machine and the network file server (if you have the Network Installation configuration), as they are automatically excluded from the emulated WAN.
Edit: Select the host name or IP address that you want to modify in the Exclude Hosts list, and make changes to the host in the Edit Hosts dialog box.
Remove: Removes an host name or IP address from the Exclude Hosts list.
Note: If you type the name of a machine, LoadRunner resolves the name and replaces it with the machine’s IP address in the Exclude Hosts list.
Stopping and Starting WAN Emulation
You can stop and start WAN emulation at any time during a scenario run.
To stop or start WAN emulation during scenario execution:
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