Communications Programming Concepts

DLCETHER Programming Interfaces

The Standard Ethernet data link control (DLCETHER) conforms to the generic data link control (GDLC) guidelines except as follows:

Note: The dlc prefix is replaced with the edl prefix for the DLCETHER device manager.

The following kernel receive packet subroutines always have the DLCETHER data link header information within the communications memory buffer (mbuf) and can locate it by subtracting the length passed (in the gdl_io_ext structure) from the data offset field of the mbuf structure.

DLC_ENABLE_SAP

The ioctl subroutine argument structure for enabling a SAP (dlc_esap_arg) has the following specifics:

• The grp_addr field is a 6-byte value as specified in the draft IEEE Standard 802.3 specifications. Octet grp_addr[0] specifies the most significant byte and octet grp_addr[5] specifies the least significant byte. Each octet of the address field is transmitted, least significant bit first. Group addresses sometimes are called multicast addresses. An example of an group address follows:

  0x0900_2B00_0004
  

  Note: No checks are made by the DLCETHER device manager as to whether a received packet was accepted by the adapter due to a preset network address or group address.

• The max_ls (maximum link station) field cannot exceed a value of 255.
• The following common SAP flags are not supported:
  

  ENCD	Indicates a synchronous data link control (SDLC) serial encoding.
  NTWK	Indicates a teleprocessing network type.
  LINK	Indicates a teleprocessing link type.
  PHYC	Indicates a physical network call (teleprocessing).
  ANSW	Indicates a teleprocessing autocall and autoanswer.

• Group SAPs are not supported, so the num_grp_saps (number of group SAPs) field must be set to 0.
• The laddr_name (local address and name) field and its associated length are only used for name discovery when the common SAP flag ADDR field is set to 0. When resolve procedures are used (that is, the ADDR flag is set to 1), DLCETHER obtains the local network address from the device handler and not from the dlc_esap_arg structure.
• The local_sap (local service access point) field can be set to any value except the null SAP (0x00) or the name-discovery SAP (0xFC). Also, the low-order bit must be set to 0 (B`nnnnnnn0') to indicate an individual address.
• No protocol-specific data area is required for the DLCETHER device manager to enable a SAP.

DLC_START_LS

The ioctl subroutine argument structure for starting a link station (dlc_sls_arg) has the following specifics:

• These common link station flags are not supported:
  

  STAT	Indicates a station type for SDLC.
  NEGO	Indicates a negotiable station type for SDLC.

• The raddr_name (remote address or name) field is used only for outgoing calls when the DLC_SLS_LSVC common link station flag is active.
• The maxif (maximum I-field) length can be set to any value greater than 0. See the DLCETHER Frame Encapsulation figure for supported byte lengths. The DLCETHER device manager adjusts this value to a maximum of 1493 bytes if set too large.
• The rcv_wind (receive window) field can be set to any value between 1 and 127, inclusive. The recommended value is 127.
• The xmit_wind (transmit window) field can be set to any value between 1 and 127, inclusive. The recommended value is 26.
• The rsap (remote SAP) field can be set to any value except null SAP (0x00) or the name-discovery SAP (0xFC). Also, the low-order bit must be set to 0 (B`nnnnnnn0') to indicate an individual address.
• The max_repoll field can be set to any value between 1 and 255, inclusive. The recommended value is 8.
• The repoll_time field is defined in increments of 0.5 seconds and can be set to any value between 1 and 255, inclusive. The recommended value is 2, giving a time-out duration of 1 to 1.5 seconds.
• The ack_time (acknowledgment time) field is defined in increments of 0.5 seconds and can be set to any value between 1 and 255, inclusive. The recommended value is 1, giving a time-out duration of 0.5 to 1 second.
• The inact_time (inactivity time) field is defined in increments of 1 second, and can be set to any value between 1 and 255, inclusive. The recommended value is 48, giving a time-out duration of 48 to 48.5 seconds.
• The force_time (force halt time) field is defined in increments of 1 second, and can be set to any value between 1 and 16383, inclusive. The recommended value is 120, giving a time-out duration of approximately 2 minutes.
• No protocol-specific data area is required for the DLCETHER device manager to start a link station.

DLC_ALTER

The ioctl subroutine argument structure for altering a link station (dlc_alter_arg) has the following specifics:

• These alter flags are not supported:
  

  RTE	Alters routing.
  SM1, SM2	Sets synchronous data link control (SDLC) control mode.

• No protocol-specific data area is required for the DLCETHER device manager to alter a link station.

DLC_QUERY_SAP

The device driver-dependent data returned from DLCETHER for this ioctl operation is the ent_ndd_stats_t structure defined in the /usr/include/sys/cdli_entuser.h file.

DLC_QUERY_LS

No protocol-specific data area is supported by DLCETHER for this ioctl operation.

DLC_ENTER_SHOLD

The enter_short_hold option is not supported by the DLCETHER device manager.

DLC_EXIT_SHOLD

The exit_short_hold option is not supported by the DLCETHER device manager.

DLC_ADD_GRP

The add_group or multicast address option is supported by the DLCETHER device manager as a six-byte value as described above in DLC_ENABLE_SAP (group address) ioctl operation.

DLC_ADD_FUNC_ADDR

The add_functional_address option is not supported by DLCETHER.

DLC_DEL_FUNC_ADDR

The delete_functional_address option is not supported by DLCETHER.

DLC_DEL_GRP

The delete group or multicast option is supported by the DLCETHER device manager. The address being removed must match an address that was added with a DLC_ENABLE_SAP or DLC_ADD_GRP ioctl operation.

IOCINFO

The ioctype variable returned is defined as DD_DLC definition and the subtype returned is DS_DLCETHER.