Feature Reference
Call-by-call service selection
1410
Administrator’s Guide for Avaya Communication Manager
November 2003
ISDN messages and information elements for
usage allocation
Understanding the technical details of ISDN messages and information elements may help you
implement ISDN.
Call-by-Call Service Selection allows the system to specify one of the preceding service types on a
call-by-call basis. You can specify service types by classifying incoming calls to an ISDN Call-By-Call
trunk group using the called-party’s number.
You can also specify service types with a SETUP message that indicates the intent of the originating
system to initiate a call using the specified service or facility. The SETUP message may contain units
called information elements (IE) that specify call-related information. The IE used with Call-by-Call
Service Selection are:
•
Network-Specific Facility (NSF)
—
Indicates which facilities or services are to be used to
complete the call (typically not used outside the US and Canada).
The system also checks all incoming ISDN trunk calls for the presence of an NSF IE. If an NSF
IE is present, the system makes sure that the requested service is compatible with the trunk
administration before it accepts a call.
For an outgoing call on a Call-By-Call trunk group, the NSF IE is constructed using the
Service/Feature specified on the routing-pattern preference selected for the call.
If the Service/Feature specified does not have an associated NSF, an NSF IE is not sent. For
example, SETUP messages for incoming and outgoing calls classified only by a called-party
number do not contain an NSF IE.
•
Transit Network Selection
—
Indicates which interexchange carrier is to be used on an
inter-LATA call.
If a call requires both the Service/Feature and the interexchange carrier to be specified, the
interexchange carrier information is sent in the NSF IE rather than the Transit Network Selection
IE.
Usage allocation plans
Optional UAPs may be assigned to provide more control over a Call-by-Call Service Selection trunk
group. You can allocate a minimum and maximum number of channels for incoming and outgoing called
numbers, privileged users, and voice and data calls.
A UAP allows the customer to set the following options:
•
Maximum number of trunks that each service can use at any given time.The sum for all services
may exceed the total number of trunk-group members. For example, for a15-member trunk group,
you could administer a maximum of seven MEGACOM service calls, six MEGACOM 800
service calls, and eight SDN calls. This ensures that all trunk-group members are not dominated
by a specific service, yet allows for fluctuations in demand.
•
Minimum number of trunks that always must be available for each service. The sum for all
services may not exceed the total number of trunk-group members. For example, for a 10-member
trunk group that provides access to MEGACOM service, MEGACOM 800 service, and SDN, the
minimum number of trunks to be used for each of these services cannot add up to more than 10.
When these UAP limits are exceeded, the system rejects the call, even if a trunk is available. On outgoing
calls, the calling party receives a reorder tone unless other preferences are available.