Native API online documentation, based on the System Informer (formerly Process Hacker) phnt headers
#ifndef _WINSTA_H

// Retrieves transport protocol driver parameters.
typedef struct _PDPARAMS
    SDCLASS SdClass; // Stack driver class. Indicates which one of the union's structures is valid.
        NETWORKCONFIG Network; // Configuration of network drivers. Used if SdClass is SdNetwork.
        ASYNCCONFIG Async; // Configuration of async (modem) driver. Used if SdClass is SdAsync.
        NASICONFIG Nasi; // Reserved.
        OEMTDCONFIG OemTd; // Configuration of OEM transport driver. Used if SdClass is SdOemTransport.


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This type is documented in the [MS-TSTS] specification.