QoS Changes in Windows Server 2003 and Windows XP (318602)

MORE INFORMATION

Windows XP and Windows Server 2003 turn off the RSVP signaling in their QoS implementation. Windows Server 2003 also removes the QoS Admission Control Service (ACS) component.

Effects on QoS Program Developers

• The Winsock GQoS semantic remains fully supported and unchanged. However, no RSVP message exchange is generated from GQoS calls. As soon as the GQoS semantics and parameter checks are passed, the program enters a state as if the RSVP signaling were completed successfully. The conforming outgoing packets are marked according to the service level that is specified in the requesting FLOWSPEC structure.
• No QoS events are posted to the program. For example, asynchronous SIO_GET_QOS never completes. However, asynchronous SIO_SET_QOS completes after the traffic-control functionality has been completed. This is the same as in Windows 2000. Because RSVP messages are turned off, program logic must not depend on receiving any specific RSVP messages. For the same reason, "Application-ID" and "Sub-Application-ID" are not useful.
• On Windows Server 2003, synchronous SIO_GET_QOS returns immediately with success and 0 bytes of data. Asynchronous SIO_GET_QOS is pending until the socket is closed. At this time, it is completed with an "abort" error.
• IP_TOS is deprecated as a way to mark packets by GQoS. Developers can continue to use GQoS for new programs if they must mark packets.
• There is no change from Windows 2000 in the Traffic Control API implementation. Only local administrators can run Traffic Control APIs. This is the same requirement as on Windows 2000.
• If RSVP messages are received on Windows XP, they are silently dropped; no ICMP error message is returned. If RSVP messages are received on Windows Server 2003, ICMP error messages are returned.

Effects on QoS Administrators

• ACS no longer exists on Windows Server 2003. The RSVP service still runs on the host as a conduit between program and traffic-control components. However, no RSVP messages are generated.
• GQoS programs can mark packets without ACS policy approval. Note that traffic-control programs can mark packets on Windows 2000, Windows XP, and Windows Server 2003. Older programs that use the IP_TOS socket option can mark packets on Microsoft Windows NT 4.0. Administrators must manage these types of programs in their networks appropriately for their network and program requirements.