14
40-400-00001, Rev. A
Service Profile ID (SPID) Assignment
Normally, each telephone line is assigned a single Directory Number. When a
customer orders services or features, they are programmed into a
Service Profile
stored at the switch. Any call associated with that line can be assumed to apply only
to that customer’s Directory Number and Service Profile. When a single ISDN
device is connected and serviced this way, the configuration is said to be
point-to-
point.
However, ISDN also supports
point-to-multipoint configurations, with multiple but
dissimilar devices connected to a single line. In many cases, is not desirable to
share the same Directory Number and Service Profile. Consequently, ISDN relies on
an initialization procedure for associating Service Profiles with individual Terminating
Equipment, rather than lines.
Terminating Equipment that support this procedure are said to be
Auto-Initializing.
The phone company gives an ISDN customer a Service Profile ID (SPID) up to
twenty digits long. The customer programs the number into the Terminating Equip-
ment, which sends it to the switch. The switch associates the SPID with a specific
Service Profile and Directory Number, and returns a corresponding
Endpoint ID to
the Terminating Equipment. When the switch sends SETUP Messages to a line
configured point-to-multipoint, it includes the Endpoint ID, and only matching Termi-
nating Equipment respond.
NOTE: NI-1 Switch Types are always configured for multi-point operation.
