Appendix E: Configuring BITS 2.0 and 3.0 for Download Performance

Applies To: Windows Server 2003 with SP2, Windows Server Update Services

BITS (Background Intelligent Transfer Service) is the service that Windows Update and Microsoft Update use for downloads. BITS 2.0 is available for download on Windows XP and Windows Server 2003 operating systems, and BITS 3.0 is part of the Windows Vista and Windows Server 2008 operating systems. You can optimize the performance of downloads by configuring BITS through Group Policy. BITS 3.0 offers a number of configurable features that do not exist in earlier versions of BITS.

For more information about BITS, see Background Intelligent Transfer Service (https://go.microsoft.com/fwlink/?LinkId=79389).

Throttling

Versions of BITs use the computer's network card to measure network traffic. BITS 3.0 can also use the Internet gateway device to monitor traffic if the computer is correctly configured; see Background Intelligent Transfer Service (https://go.microsoft.com/fwlink/?LinkId=79389) for details. However, in some situations the network card in itself does not give an accurate measurement of the actual state of network traffic. For example, if a computer has a fast network card but a slow network connection (such as a dial-up connection), BITS will give an overly optimistic measurement. It is possible to use Group Policy (in both BITS 2.0 and 3.0) to throttle or limit the network bandwidth that BITS uses for downloads or uploads.

Note

BITS bandwidth limitations are system wide, not application specific. You cannot use this setting to limit only WSUS download bandwidth, because the BITS settings will affect BITS in any application.

To set BITS bandwidth limitations

  1. Start the Group Policy Object Editor (click Start, click Run, and then type gpedit.msc).

  2. Expand Computer Configuration, then Administrative Templates, then Network, then Background Intelligent Transfer Service.

  3. Open the Maximum network bandwidth that BITS uses (BITS 2.0) or Maximum network bandwidth for BITS background transfers (BITS 3.0) setting.

  4. Set the transfer rate in kilobits per second that you want BITS to use (the default is 10).

  5. Set the times at which you want to limit the bandwidth (the default is 8:00 A.M. to 5:00 P.M.).

  6. Set the limitations to be used outside of the designated time (the default is Use all available unused bandwidth, but you may select another limitation).

  7. Click OK.

Note

You must be an administrator to perform this procedure.

Peer caching

Peer caching is a new feature of BITS 3.0 that allows peers (computers within the same subnet of a network that have the peer caching feature enabled) to share files. If peer caching is enabled on a computer, the Automatic Update agent instructs BITS to make downloaded files available to that computer's peers as well.

When the files have been downloaded, BITS caches them. When another (peer caching-enabled) computer tries to download the same update, BITS on that computer sends a multicast request to all of that computer's peers. If one or more of the peers responds to the request, BITS will download the file from the first computer to respond. If the download from the peer fails or take too long, BITS continues the download from the WSUS server or Microsoft Update.

This feature of BITS can optimize the bandwidth used by WSUS in several ways.

  1. Peer caching decreases the amount of data transferred from the WSUS server to its clients, because computers in the same subnet will usually download the updates from each other.

  2. Peer caching decreases the amount of data transferred across the WAN when some or all of the clients of a WSUS server are located in different locations.

  3. Peer caching decreases the amount of data transferred across the Internet if WSUS clients in the same subnet are configured to download updates from Microsoft Update.

Note

BITS peer caching requires computers to be running Windows Vista or Windows Server 2008, and to be part of an Active Directory Domain.

For more information about peer caching and peer servers, see Peer Caching (https://go.microsoft.com/fwlink/?LinkId=79432).

To enable peer caching (on Windows Vista)

  1. Start the Group Policy Object Editor (click Start, click Run, and then type gpedit.msc).

  2. Expand Computer Configuration, then Administrative Templates, then Network, then Background Intelligent Transfer Service.

  3. Enable the Allow BITS Peercaching setting.

  4. Enable the Maximum network bandwidth used for Peercaching setting, and set the maximum bandwidth in bits per second (the default is 104857), then click OK.

  5. Enable the Limit the BITS Peercache size setting, and set the percentage of disk space to be used for the peer cache (the default is 5 percent), and then click OK.

  6. Enable the Limit age of items in the BITs Peercache setting, and set the number of days (the default is 90), and then click OK.

Note

You must be an administrator to perform this procedure.