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     ng_sscfu — netgraph SSCF at the UNI node type


     #include <netnatm/saal/sscopdef.h>
     #include <netnatm/saal/sscfudef.h>
     #include <netgraph/atm/ng_sscfu.h>


     The sscfu netgraph node type implements ITU-T recommendation Q.2130.  This recommendation
     specifies the Service Specific Coordination Function at the UNI.  This is a thin sub-layer
     between the SSCOP (see ng_sscop(4)) and the UNI signalling.  This node does not really
     implement a protocol but provides a mapping between the signals at the upper layer of the
     SSCOP and the signals the UNI expects at its lower layer.  It also provides default values
     for the parameters of the SSCOP.

     After creation of the node, the SSCF instance must be created by sending an “enable” message
     to the node.  If the node is enabled, default SSCOP parameters can be retrieved and set in
     the corresponding SSCOP instance.

     The node is shut down either by a NGM_SHUTDOWN message, or when all hooks are disconnected.


     Each sscfu node has two hooks with fixed names:

     lower  This hook is the interface to the SSCOP.  The interface expected here is exactly that
            which is exported by the ng_sscop(4) node type.

     upper  This is the interface to the UNI.  It uses the following message format:

            struct sscfu_arg {
                    uint32_t sig;
                    u_char   data[];

            The sig field is one of the following signals:

            enum saal_sig {
                SAAL_ESTABLISH_request,     /* U -> SAAL: (UU) */
                SAAL_ESTABLISH_indication,  /* SAAL -> U: (UU) */
                SAAL_ESTABLISH_confirm,     /* SAAL -> U: (UU) */
                SAAL_RELEASE_request,       /* U -> SAAL: (UU) */
                SAAL_RELEASE_confirm,       /* SAAL -> U: */
                SAAL_RELEASE_indication,    /* SAAL -> U: (UU) */
                SAAL_DATA_request,          /* U -> SAAL: (DATA) */
                SAAL_DATA_indication,       /* SAAL -> U: (DATA) */
                SAAL_UDATA_request,         /* U -> SAAL: (UDATA) */
                SAAL_UDATA_indication,      /* SAAL -> U: (UDATA) */

            The arrows in the comment show the direction of the signal, whether it is a signal
            that comes out of the node (‘->’), or is sent by the node user to the node (‘<-’).
            The type of the data expected for the signal is specified in parentheses.  This data
            starts at the data field of the message structure.

     If the lower hook is disconnected and the node is enabled, the protocol state is reset.


     The sscfu node understands the generic messages plus the following:

     NGM_SSCFU_GETDEFPARAM (getdefparam)
          This message returns a sscop_param structure, which contains the default parameters for
          the SSCOP at the UNI.  This structure should be used for a NGM_SSCOP_SETPARAM message
          to the SSCOP node below the SSCF.

     NGM_SSCFU_ENABLE (enable)
          This message creates the actual SSCF instance and initializes it.  Until this is done,
          parameters may neither be retrieved nor set, and all messages received on any hook are

     NGM_SSCFU_DISABLE (disable)
          Destroy the SSCF instance.  After this, all messages on any hooks are discarded.

     NGM_SSCFU_GETDEBUG (getdebug)
          Retrieve the debugging flags in a uint32_t.

     NGM_SSCFU_SETDEBUG (setdebug)
          Set debugging flags.  The argument must be a uint32_t.

     NGM_SSCFU_GETSTATE (getstate)
          Retrieve the current state of the SSCFU instance in a uint32_t.  If the node has not
          been enabled, 0 is returned.


     netgraph(4), ng_atm(4), ng_sscop(4), ngctl(8)


     Harti Brandt <>