DLC System Driver Entries

The DLC subkey does not appear unless this service is installed. In Windows NT, the Data Link Control (DLC) protocol only needs to be installed on computers that access IBM mainframes (usually with 3270 applications) or on print servers that print directly to Hewlett-Packard printers. Network printers such as the HP III si use the DLC protocol, for example, because the frames received are easy to take apart.

The DLC driver depends on an having an NDIS group service available and is bound to the network adapter card through the NDIS device driver. Each adapter that supports the DLC protocol has a subkey under the DLC\Parameters subkey. With Registry Editor, you can modify the following parameters for the DLC system driver. The path for these parameters is the following:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services
    \DLC\Parameters\adapter name

The following TxTick parameters are multipliers for the T1, T2, and Ti values, which represent time periods in milliseconds that are used when a station or SAP is opened. If the time period value is between 1 and 5, the time delay is computed as follows:

(time period) * TxTickOne * 40 milliseconds

If the time period value is between 6 and 10, the time delay is computed as follows:

(time period - 5) * TxTickTwo * 40 milliseconds

When computing the short-tick values (_One) and the long-tick values (_Two), the resulting values for T1, T2, and Ti should generally follow this rule: T2 < T1 < Ti.

T1Tick{One|Two} REG_DWORD 1 to 255 milliseconds

Specifies the delay before retransmitting an I frame if not acknowledged.

Default: T1TickOne = 5; T1TickTwo = 25

T2Tick{One|Two} REG_DWORD 1 to 255 milliseconds

Specifies the delay before acknowledging frames in the receive window if the receive window has not been filled.

Default: T2TickOne = 1; T2TickTwo = 10

TiTick{One|Two} REG_DWORD 1 to 255 milliseconds

Specifies the delay before testing an inactive station to determine if it is still active.

Default: TiTickOne = 25; TiTickTwo = 125

Swap REG_DWORD 0 or 1

Used when talking over Ethernet to support certain Token Ring-to-Ethernet bridges in swapping of the Destination Address when using DLC over a Token Ring network. If this value is 0, the adapter addresses presented at the API interface are not bit-flipped before being put online.

Default: 1

UseDixOverEthernet REG_DWORD 0 or 1

Specifies the default mode for the connection-oriented and connectionless 802.2 LLC (Logical Link Control) frames sent on Ethernet. If this value is 1, the DLC driver users DIX encoding in the frames to be transmitted instead of the 802.3 Ethernet format.

Default: 0

Note Additional parameters that were included in the Microsoft LAN Manager COMTOKR utility are not defined for DLC, because Windows NT does not have the same memory limitations as MS-DOS.