The SECURITY_QUALITY_OF_SERVICE structure defines information used to support client impersonation as specified in [MS-LSAD] section 2.2.3.7.

 typedef struct _SECURITY_QUALITY_OF_SERVICE {
   unsigned long Length;
   SECURITY_IMPERSONATION_LEVEL ImpersonationLevel;
   SECURITY_CONTEXT_TRACKING_MODE ContextTrackingMode;
   unsigned char EffectiveOnly;
 } SECURITY_QUALITY_OF_SERVICE,
  *PSECURITY_QUALITY_OF_SERVICE;

Individual member semantics are specified in [MS-LSAD] section 2.2.3.7.