223
6620-3201
1
The unit will
fi
rst look up the Called NUA/NUI in the
Confi gure
>
X25
>
NUA/NUI–>IP address
mapping table to determine the IP address to use in the event that the call ends up being
switched to a TCP or XOT interface. If a match is found on the Called NUA/NUI the unit assigns
the matching IP address from the table to the call. If IP address mapping table does not contain
an entry for the Called NUA/NUI and the call is eventually switched to a TCP or XOT channel
then the default IP address (XOT remote IP address) is used.
2
The unit then determines from the source interface of the incoming call which interface type it
should be switched to (from the
Switch from
parameters on the
Confi gure
>
X25
>
Switch
page). For example, if the call arrived via a LAPB 0 interface and the
Switch from LAPB 0 to
parameter was set to LAPD, then the outgoing interface would LAPD.
3
If the outgoing interface is LAPD the unit changes the Calling NUA
fi
eld of the incoming call to
the D-Channel NUA value (as de
fi
ned on the
Confi gure
>
X25
>
Switch
page). If the outgoing
interface is NOT LAPD processing proceeds as at step 6
4
The unit then searches the X.25 Switch NUA Mappings table to see if there are any matches for
the Called or Calling NUA values on the speci
fi
ed interface. In cases where there is a match, the
NUA In value is substituted by the NUA out value, i.e. the mapping is applied individually to both
the Calling NUA and Called NUA for the packet.
5
The unit then checks the leading characters of the Calling NUA to see if there is a match with the
Call Pre
fi
x parameter. If there is a match then the pre
fi
x digits are removed before the outgoing
X.25 call is made. Otherwise the call is made anyway and the switching process is complete for
this call.
6
If after step 3, the unit has determined that the outgoing interface is not LAPD, it checks if the
outgoing interface is LAPB. If it is, it then checks to see if the Called NUA
fi
eld in the call packet
matches the LAPB 0 NUA parameter and if it does, selects LAPB 0 as the outgoing interface. If
the Called NUA
fi
eld does not match LAPB 0 NUA, it checks for a match with LAPB 1 NUA and if
there is a match, sets the outgoing interface to LAPB 1.
7
If the Called NUA
fi
eld in the calling packet matches neither the LAPB 0 NUA or LAPB 1 NUA
parameters then the outgoing interface is set to the interface speci
fi
ed by the relevant
Switch
from
parameter.
8
If the call is being switched over LAPB 0 the unit then sets the Called NUA to the TE NUA (LAPB
0) value. If the call is being switched over LAPB 1 the unit then sets the Called NUA to the TE
NUA (LAPB 1) value.
Using the Web Page(s)
The
Confi gure
>
X25 Switch
page is used to con
fi
gure the X.25 Switch using the following
parameters:
Switch from XOT (TCP) to:
This parameter controls the switching of incoming X.25 calls received via XOT. Select the interface
to which data should be switched from the drop down list, or select “Off” and the X25 switch will not
respond to any incoming XOT calls.
Switch from LAPD to:
This parameter controls the switching of incoming X.25 calls received via ISDN LAPD. Select the
interface to which data should be switched from the drop down list, or select “Off” and the X25 switch
will not respond to any incoming LAPD calls.
Switch from LAPB 0 to:
This parameter controls the switching of incoming X.25 calls received via LAPB 0. Select the interface
to which data should be switched from the drop down list, or select “Off” and the X25 switch will not
respond to any incoming LAPB 0 calls.
Switch from LAPB 1 to:
This parameter controls the switching of incoming X.25 calls received via LAPB 1. Select the interface
to which data should be switched from the drop down list, or select “Off” and the X25 switch will not
respond to any incoming LAPB 1 calls.
