Configuring Advanced QoS Settings

You can also configure advanced QoS settings for computers using Group Policy. Within the Group Policy Object Editor, right-click the Computer Configuration\Windows Settings\Policybased QoS node and then click Advanced QoS Settings. You can use the Advanced QoS Settings dialog box to configure the following settings:

• Specify The Inbound TCP Throughput Level Most QoS policies relate to outbound traffic that the client computer sends. You can use this setting on the Inbound TCP Traffic tab to configure Windows so that it will attempt to throttle incoming traffic. Although Windows has direct control over the throughput of outbound traffic, it has indirect control only over the rate of incoming traffic. For TCP connections, you can configure a Windows client computer to limit incoming traffic by specifying the maximum size of the TCP receive window. The TCP receive window is the amount of data that a receiver allows a sender to send before having to wait for an acknowledgment. A larger maximum window size means that the sender can send more data at a time, increasing network utilization and throughput. By limiting the maximum size of the TCP receive window, a receiver can indirectly control the incoming throughput for a TCP connection. Level 3 (Maximum Throughput) is for a 16-megabyte (MB) TCP receive window. Level 2 is for a 1-MB TCP receive window. Level 1 is for a 256-kilobyte (KB) TCP receive window. Level 0 is for a 64-KB TCP receive window. Unlike Policy-based QoS settings for outgoing traffic, this setting cannot control the rate of incoming traffic on a per-application, per-address, or per-port basis.
  Note Because UDP traffic is not acknowledged, you cannot throttle UDP traffic from the receiving computer.
• Control DSCP Marking Requests From Applications DSCP marking adds information to outgoing packets to identify the priority of the packet. If your network infrastructure supports DSCP-differentiated delivery, the infrastructure can use the DSCP value to select a priority for traffic. Use this setting to allow applications to specify their own DSCP values or to ignore application-specified values and only allow QoS policies to specify DSCP values.

For more information about Policy-based QoS, visit the "Quality Of Service" home page at http://technet.microsoft.com/en-us/network/bb530836.aspx.