DLPI Primitives
Connectionless-mode Service Primitives
This section describes the
DL_UNITDATA_REQ
Conveys one DLSDU from the DLS user to the DLS provider for transmission to a peer DLS user.
Because connectionless data transfer is an unacknowledged service, the DLS provider makes no guarantees of delivery of connectionless DLSDUs. It is the responsibility of the DLS user to do any necessary sequencing or retransmission of DLSDUs in the event of a presumed loss.
Priority messages are currently only supported over 100VG. To send a priority message over 100VG, a user must have superuser capabilities and set the dl_priority fields in the DL_UNITDATA_REQ primitive to the following values:
dl_min must be set to 0.
dl_max must be set to 1.
The dl_priority field will be ignored on interfaces which do not support priority messages.
Format
The message consists of one M_PROTO message block containing the structure shown below, followed by one or more M_DATA blocks containing at least one byte of data. The amount of user data that may be transferred in a single DLSDU is limited. This limit is conveyed by the parameter dl_max_sdu in the DL_INFO_ACK primitive.
typedef struct { |
|
ulong | dl_primitive; |
ulong | dl_dest_addr_length; |
ulong | dl_dest_addr_offset; |
dl_priority_t | dl_priority; |
}dl_unitdata_req_t;
Parameters
dl_primitive
DL_UNITDATA_REQ
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