Operation Manual

Cost Assignment (COSO)
71 NT/MPRI – 4 Special NT/MPRI Settings
For this situation the NT/MPRI also offers the following features to en-
sure that “important” connections are not obstructed, even when few
B channels are available:
l B channels can be reserved for certain call destinations, such as a
certain company office, in the ISDN-Controller settings (“Configu-
ration / Server Settings / ISDN-Controller”). These B channels are
then removed from the pool of shared channels.
l Call destinations can be assigned a priority level in the call desti-
nation settings (high, normal, low). This ensures that high-priority
connections will always find a B channel available. If all B chan-
nels are busy when a connection is requested, a lower-priority
connection is cleared down.
4.4 Cost Assignment (COSO)
The ISDN feature “D-channel Signaling” is provided free of charge by
most ISDN providers and is used in the NT/MPRI for cost assignment
(COSO = Charge One Site Only).
With this function you can specify which end of the link bears the con-
nection charges. For each call destination this may be the local site,
the remote site or whichever site initiates the connection.
Because COSO is a feature for ISDN and not yet incorporated into a PPP
standard, the remote router must also support this function. Remote
sites equipped with the NetWare® MultiProtocol™ Router for ISDN 3.1
by AVM, for instance, allow COSO.
The following figure illustrates how an incoming call is handled when
cost allocation is set to the “Local Site” (NT/MPRI bears the connection
charges):
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