Testing Network Performance with DP8Sim

The DP8Sim tool is a simulated Microsoft® DirectPlay® 8.1 service provider that allows you to test your DirectPlay application in a variety of network conditions, such as high latency and packet loss. DP8Sim is not a replacement for testing in the real deployment environment, but it can help you predict how your application will perform.

Note  DP8Sim is implemented on top of the existing DirectPlay8 TCP/IP Service Provider. The settings are also applied on top of the existing network characteristics. Therefore, it is intended to be used on a high-speed local area network (LAN) where normal latency and packet loss are negligible.

Path

Executable: (SDK Root)\bin\dp8simui.exe

DLL: (SDK Root)\bin\dp8sim.dll

User's Guide

The configuration utility, dp8simui.exe, is the user interface for controlling dp8sim.dll. Both files must reside in the same directory. When you start the configuration utility, it will automatically register the dp8sim.dll component object model (COM) objects. You can also manually register the dynamic link library (DLL) by typing the following command at your Microsoft MS-DOS® prompt.

regsvr32.exe dp8sim.dll

When you run the configuration utility, it will prompt you to enable the network simulator for the DirectPlay TCP/IP service provider. Any existing DirectPlay sessions will not use the network simulator if the DirectPlay interface was created prior to enabling the simulator.

Once the simulator is enabled, you can control various network options. There are also predefined network settings that may be useful.

The options for sending (receiving) are:

• Bandwidth (bytes/second). The total available outbound (inbound) bandwidth for all players in bytes per second. All packets have their latency increased in proportion to their size according to this value. If the application sends (receives) more than this amount, later packets are queued behind earlier ones. Use 0 (zero) for unlimited bandwidth, up to the real underlying network bandwidth.
• Drop percentage (0 to 100 percent). The random frequency as a percentage for an individual outbound (inbound) packet to be dropped. Each packet stands the same chance of being dropped, regardless of other packets. Note that this does not necessarily model the behavior of all networks. Packet loss on the Internet, for example, tends to be erratic, with packet loss high at some times and low at others. A value of 1 means that an average of 1 out of every 100 packets is dropped. A value of 100 means every packet is dropped. Use 0 if you do not want to drop any packets other than loss due to the real underlying network.
• Minimum latency (milliseconds). The minimum delay in milliseconds for outbound (inbound) packets. The actual delay for an individual packet is chosen randomly between this minimum value and the maximum latency value. Note that the delay is applied on top of any delay imposed by bandwidth limitations. Use 0 if you do not want to have a lower bound for artificial latency beyond the real underlying network.
• Maximum latency (milliseconds). The maximum delay in milliseconds for outbound (inbound) packets. The actual delay for an individual packet is chosen randomly between the minimum latency value and this maximum value. If this value is lower than the minimum latency value, it is automatically set to equal the minimum value. Note that the delay is applied on top of any delay imposed by bandwidth limitations. Use 0 if you do not want to have an upper bound for artificial latency beyond the real underlying network.

Note  These options apply for in-game data only. Host enumerations and responses are not subject to the simulation.

To make modifications, use the Apply and Revert buttons. Click Apply to change the settings and Revert to restore the previous settings.

At the bottom of the configuration utility window, the send and receive statistics for all affected DirectPlay interfaces are displayed. The Refresh button updates the statistics and Clear resets the statistics to 0.

When you close the configuration utility, you will be asked if you want to disable the network simulator. Disabling the simulator prevents subsequent DirectPlay sessions from being affected by DP8Sim, but existing sessions will continue to use the existing network settings. If you leave DP8Sim enabled, subsequent DirectPlay sessions will continue to use the existing network settings even when the configuration utility is not running.

To unregister dp8sim.dll, type the following at the MS-DOS command prompt.

regsvr32.exe /u dp8sim.dll

For more information about network performance, see Optimizing Network Usage.