Connectionless Traffic

For connectionless traffic that requires a response from a remote computer, NBF sends out a certain number of frames, depending on the command. The total number is based on retry Registry value entries, such as NameQueryRetries. The time between sending each frame is determined by timeout Registry entries, such as NameQueryTimeout.

Three types of NetBIOS commands generate connectionless traffic: name claim and resolution, datagrams, and miscellaneous commands. These commands are sent as UI (Unnumbered Information) frames at the LLC sublayer.

To see how Windows NT uses retry and timeout values from the Registry, consider what happens when Windows NT registers computernames via NBF using the NetBIOS Add.Name command. When NBF receives the Add.Name command, it broadcasts ADD_NAME_QUERY frames a total of AddNameQueryRetries times and sends these broadcasts at a time interval of AddNameQueryTimeout. This allows computers on the network enough time to inform the sending computer whether the name is already registered as a unique name on another computer or a group name on the network.

Note

All Registry values discussed in this chapter are found under the following Registry path:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Nbf