DLC FDDI Programming Interfaces

Communications Programming Concepts

DLC FDDI Programming Interfaces

The data link control (DLC) fiber distributed data interface (FDDI) conforms to generic data link control (GDLC) guidelines except where noted below. Additional structures and definitions for DLC FDDI are found in the /usr/include/sys/fdlextcb.h file.

The following entry points are supported by DLC FDDI:

Note: The dlc prefix is replaced with the fdl prefix for the DLC FDDI device manager.

fdlclose	Fully compatible with the dlcclose GDLC interface.
fdlconfig	Fully compatible with the dlcconfig GDLC interface. No initialization parameters are required.
fdlmpx	Fully compatible with the dlcmpx GDLC interface.
fdlopen	Fully compatible with the dlcopen GDLC interface.
fdlread	Compatible with the dlcread GDLC interface with the following conditions: The readx subroutines may have DLC FDDI data link header information prefixed to the information field (I-field) being passed to the application. This is optional based on the readx subroutine data link header length extension parameter in the gdl_io_ext structure. If this field is nonzero, DLC FDDI copies the data link header and the I-field to user space, and sets the actual length of the data link header into the length field. If the field is 0, no data link header information is copied to user space. See the DLC FDDI Frame Encapsulation figure for more details. Kernel receive packet function handlers always have the DLC FDDI 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.
fdlselect	Fully compatible with the dlcselect GDLC interface.
fdlwrite	Compatible with the dlcwrite GDLC interface, with the exception that network data can only be written as an unnumbered information (UI) packet and must have the complete data link header prefixed to the data. DLC FDDI verifies that the local (source) service access point (SAP) is enabled and that the control byte is UI (0x03). See the DLC FDDI Frame Encapsulation figure for more details.
fdlioctl	Compatible with the dlcioctl GDLC interface. The following ioctl operations contain FDDI-specific conditions on GDLC operations: DLC_ENABLE_SAP DLC_START_LS DLC_ALTER DLC_ENTER_SHOLD DLC_EXIT_SHOLD DLC_ADD_GRP DLC_ADD_FUNC_ADDR DLC_DEL_FUNC_ADDR DLC_DEL_GRP DLC_QUERY_SAP DLC_QUERY_LS IOCINFO The following sections describe these conditions.

DLC_ENABLE_SAP

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

The grp_addr (group address) field contains the full six-byte group address with the individual control bits, group control bits, universal control bits, and local control bits located in the most significant bit positions of the first (leftmost) byte.
The func_addr_mask (functional address mask) field is not supported.
The max_ls (maximum link stations) field cannot exceed a value of 255.

The following common SAP flags are not supported:

NTWK	Indicates a teleprocessing network type.
LINK	Indicates a teleprocessing link type.
PHYC	Represents 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 or name) field and its associated length are only used for name discovery when the common SAP flag ADDR is set to 0. When resolve procedures are used (the ADDR flag set to 1), DLC FDDI 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 DLC FDDI to enable an SAP.

DLC_START_LS

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

The following 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) field can be set to any value greater than 0. The DLC FDDI device manager adjusts this value to a maximum of 4077 bytes if set too large. See the DLC FDDI frame encapsulation figure for more details.
The rcv_wind (receive window) field can be set to any value from 1 to 127, inclusive. The recommended value is 127.
The xmit_wind (transmit window) field can be set to any value from 1 to 127, inclusive. The recommended value is 26.
The rsap (remote SAP) 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.
The max_repoll field can be set to any value from 1 to 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 from 1 to 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 from 1 to 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 from 1 to 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 from 1 to 16383, inclusive. The recommended value is 120, giving a time-out duration of approximately 2 minutes.

A protocol-specific data area must be appended to the generic start link station (LS) argument (dlc_sls_arg). This structure provides DLC FDDI with additional protocol-specific configuration parameters:

struct fdl_start_psd
{
 uchar_t       pkt_prty;        /* ring access packet priority */
 uchar_t       dyna_wnd;        /* dynamic window increment    */
 ushort_t      reserved;        /* currently not used          */
};

The protocol-specific parameters are:

pkt_prty

Specifies the ring-access priority that the user wishes to reserve on transmit packets. Values of 0 to 7 are supported, where 0 is the lowest priority and 7 is the highest priority.

dyna_wnd

Network congestion causes the local transmit window count to automatically drop to a value of 1. The dynamic window increment specifies the number of consecutive sequenced packets that must be acknowledged by the remote station before the local transmit window count can be increment. This allows a gradual increase in network traffic after a period of congestion. This field can be set to any value from 1 to 255; the recommended value is 1.

DLC_ALTER

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

The following common alter flags are not supported:
SM1, SM2 Sets SDLC control mode.

RTE Alters routing.

A protocol-specific data area must be appended to the generic alter link station argument structure (dlc_alter_arg). This structure provides DLC FDDI with additional protocol-specific alter parameters.

#define FDL_ALTER_PRTY 0x80000000 /* alter packet priority   */
#define FDL_ALTER_DYNA 0x40000000 /* alter dynamic window incr*/
struct fdl_alter_psd
{
ulong_t        flags;     /* specific alter flags           */
uchar_t        pkt_prty;  /* ring access packet priority value */
uchar_t        dyna_wnd;  /* dynamic window increment value */
ushort_t       reserved;  /* currently not used     */
};

Specific alter flags include:

FDL_ALTER_PRTY	Specifies alter priority. If set to 1, the `pkt_prty` value field replaces the current priority value being used by the link station. The link station must be started for this alter command to be valid.
FDL_ALTER_DYNA	Specifies alter dynamic window. If set to 1, the `dyna_wnd` value field replaces the current dynamic window value being used by the link station. The link station must be started for this alter command to be valid.

The protocol-specific parameters are:

`pkt_prty`	Specifies the new priority reservation value for transmit packets.
`dyna_wnd`	Specifies the new dynamic window value to control network congestion.

DLC_ENTER_SHOLD

The enter_short_hold option is not supported.

DLC_EXIT_SHOLD

The exit_short_hold option is not supported.

DLC_ADD_GROUP

The add_group, or multicast address, option is supported by DLC FDDI as a six-byte value as described above in DLC_ENABLE_SAP (group address).

The grp_addr (group address) field for FDDI contains the full six-byte group address with the individual/group and universal/local control bits located in the most significant bit positions of the first (leftmost) byte.

DLC_ADD_FUNC_ADDR

The add_functional_address option is not supported.

DLC_DEL_FUNC_ADDR

The delete_functional_address option is not supported.

DLC_DEL_GRP

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

DLC_QUERY_SAP

The device driver-dependent data returned from DLC FDDI for this ioctl operation is the fddi_ndd_stats_t structure defined in the /usr/include/sys/cdli_fddiuser.h file.

DLC_QUERY_LS

There is no protocol-specific data area supported by DLC FDDI for this ioctl operation.

IOCINFO

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

Asynchronous Function Calls

DLC FDDI is fully compatible with the GDLC interface concerning asynchronous function calls to the kernel mode user.

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

SM1, SM2	Sets SDLC control mode.
RTE	Alters routing.