LLC_BUFFER Overview  Group

The LLC_BUFFER union represents the buffer for received data. Specify this structure in the LLC_RECEIVE_PARMS structure.

typedef union _LLC_BUFFER LLC_BUFFER, *PLLC_BUFFER;

union _LLC_BUFFER {



    PLLC_BUFFER pNext;



    LLC_NEXT_BUFFER Next;



    struct LlcNextBuffer {

        LLC_NEXT_BUFFER Header;

        UCHAR auchData[];

    } Buffer;



    LLC_NOT_CONTIGUOUS_BUFFER NotContiguous;



    struct {

        LLC_NOT_CONTIGUOUS_BUFFER Header;

        UCHAR auchData[];

    } NotCont;



    LLC_CONTIGUOUS_BUFFER Contiguous;



    struct {

        LLC_CONTIGUOUS_BUFFER Header;

        UCHAR auchData[];

    } Cont;



};

Members

pNext

Specifies the address of an LLC_BUFFER structure representing the next buffer.

Next

The LLC_NEXT_BUFFER structure representing the next buffer.

Header

The LLC_NEXT_BUFFER structure representing the header.

auchData

Specifies the address of the data.

NotContiguous

The LLC_NOT_CONTIGUOUS_BUFFER structure representing the next buffer.

Header

The LLC_NOT_CONTIGUOUS_BUFFER structure representing the header.

auchData

Specifies the address of the data.

Contiguous

The LLC_CONTIGUOUS_BUFFER structure representing the next buffer.

Header

The LLC_CONTIGUOUS_BUFFER structure representing the header.

auchData

Specifies the address of the data.

Remarks

Media Access Control (MAC) frames consist of a LAN header followed by a data field. Non-MAC frames consist of a LAN header, a DLC header, and a data field. The application provides the data in the data field. The DLC header varies depending on the frame type: frames used by Type 2 protocols have a 4-byte DLC header and frames used by Type 1 protocols have a 3-byte header. The frame type also determines what information the application provides and how it is provided, as shown in the following table.

Frame Type	Description
MAC Frames	The application provides the complete LAN header and the data field. The source address in the LAN header is overwritten with the address used by the adapter.
I-Frames	The application provides only the data. The information used to build the headers is provided by the LLC_DLC_OPEN_STATION and LLC_DLC_CONNECT_STATION commands.
Direct Frames	The application provides the LAN header and the data in its own buffers. It provides the information to build the headers with one of the LLC_TRANSMIT commands. The command overwrites the source address in the LAN header with the address used by the adapter.

When you use more than one buffer to receive a frame, the format for the first buffer is different from the format of the other buffers used to contain the frame.

See Also

AcsLan, LLC_CONTIGUOUS_BUFFER, LLC_NEXT_BUFFER, LLC_NOT_CONTIGUOUS_BUFFER, LLC_RECEIVE_PARMS