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Debugging Windows QoS

How to leverage Windows 2000 features with custom IP Telephony.

Microsoft's Windows 2000 line of operating systems has many QoS features that your VoIP or IP Telephony systems can use. Although there probably aren't many people running custom IP Telephony applications right now, many research groups are predicting that almost everyone will be soon. So understanding how Windows hosts and workstations cooperate with your routers and switches as part of your overall QoS infrastructure will be important in the future, even if it isn't your most pressing concern today.

Unfortunately, by default, you don't get a lot of detailed information about what's actually going on inside your Windows machines, but there is a way to enable it. First, visit Microsoft's support website and look up Knowledge Base Article 244678. This article explains how you can modify the HKEY_LOCAL_MACHINESSystemCurrentControlSetServicesRsvpParameters key to enable detailed logging from the QoS service provider itself, or an application that is using the generic QoS API. Both of these can be extremely useful in troubleshooting, or just understanding how things actually work.

As the article explains, you just have to add a value EnableDebugAid of type REG_DWORD and set the value to 1 to debug information about an application or 0 for debug information about the service provider. The detailed information is stored in two logfiles in the %SystemRoot%System32Logfiles folder. Qossp.aid contains the information about the QoS service provider and Rapilib.aid contains information about an application using the QoS API.

Thomas Alexander Lancaster IV is a consultant and author with over ten years experience in the networking industry, focused on Internet infrastructure.

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