When the local node has opened the LINK and STATION LPI connections and received a Station-Contacted message from the SNALink for a remote station, it can exchange data (using the DLC interface) with the PU and associated LUs at the remote station.
Data messages are contained within buffers. The transmission header (TH) of the SNA path information unit is contained within the buffer header. The request/response header (RH), if present, and request/response unit (RU) are contained within one or more buffer elements. The TH is contained in the buffer header for historical reasons. Typically this will be copied by the SNALink into the element before startd, to keep the entire frame in contiguous memory locations. See DLC-Data for a description of the DLC-Data message format.
Note that all data messages to a specified remote station flow on the associated DLC STATION LPI connection, and not on the controlling DLC LINK LPI connection.