Microsoft KB Archive/315267

= The Advantages of Direct Hosting of SMB over TCP/IP =

Article ID: 315267

Article Last Modified on 1/24/2002

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APPLIES TO


 * Microsoft Windows XP Home Edition
 * Microsoft Windows XP Professional Edition
 * Microsoft Windows XP 64-Bit Edition

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This article was previously published under Q315267



SUMMARY
This article discusses the advantages of the Windows XP strategy of removing NetBIOS transport for file and printer sharing traffic.

Windows XP supports file and printer sharing traffic by using the Server Message Block (SMB) protocol directly hosted on TCP. In earlier operating systems, SMB traffic requires the NetBIOS over TCP (NBT) protocol to work on a TCP/IP transport.



MORE INFORMATION
Removing the NetBIOS transport has several advantages, including:
 * Simplifying the transport of SMB traffic.
 * Removing WINS and NetBIOS broadcast as a means of name resolution.
 * Standardizing name resolution on DNS for file and printer sharing.

If both the direct-hosted and NBT interfaces are enabled, both methods are tried at the same time, and the first to respond is used. This allows Windows to function properly with operating systems that do not support direct hosting of SMB traffic. NetBIOS over TCP traditionally uses the following ports:   nbname            137/UDP nbname           137/TCP nbdatagram       138/UDP nbsession        139/TCP Direct hosted &quot;NetBIOS-less&quot; SMB traffic uses port 445 (TCP and UDP). In this situation, a 4-byte header precedes the SMB traffic. The first byte of this header is always 0x00, and the next three bytes are the length of the remaining data.

Use the following steps if you want to disable NBT and force all SMB traffic to be direct-hosted. However, be careful about implementing this setting because the Windows-based computer will be unable to communicate with earlier operating systems using SMB traffic:
 * 1) Click Start, click Control Panel, and then double-click Network and Dial-up Connection.
 * 2) Right-click Local Area Connection, and then click Properties.
 * 3) Click Internet Protocol (TCP/IP), and then click Properties.
 * 4) Click Advanced.
 * 5) Click the WINS tab, and then click Disable NetBIOS over TCP/IP.
 * 6) Click OK, click OK, and then click Close.

You can also disable NBT by using a DHCP server with Microsoft vendor-specific option code 1 (&quot;Disable NetBIOS over TCP/IP&quot;). Setting this option to a value of 2 disables NBT. For more information about using this method, refer to the DHCP Server Help file in Windows.

To determine whether NBT is enabled on a Windows-based computer, run a net config redirector or net config server command at a command prompt. The output shows bindings for the NetbiosSmb device (which is the &quot;NetBIOS-less&quot; transport) and for the NetBT_Tcpip device (which is the NBT transport). For example, the following sample output shows both the direct-hosted and the NBT transport bound to the adapter:   Workstation active on      NetbiosSmb (000000000000) NetBT_Tcpip_{610E2A3A-16C7-4E66-A11D-A483A5468C10} (02004C4F4F50) NetBT_Tcpip_{CAF8956D-99FB-46E3-B04B-D4BB1AE93982} (009027CED4C2) NetBT_Tcpip is bound to each adapter individually; an instance of NetBT_Tcpip is shown for each network adapter that it is bound to. NetbiosSmb is a global device and is not bound on a per-adapter basis. This means that direct-hosted SMBs cannot be disabled in Windows without completely disabling File and Printer Sharing for Microsoft Networks.

Keywords: kbinfo kbenv kbnetwork KB315267

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