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Dialing transformations allow the call-routing component to modify either the calling
(initiator) or called (destination) digits of a call. Transformations that modify the calling
number (automatic number identification, ANI) are calling-party transformations; transformations
that modify the dialed digits (dialed number identification system, DNIS) are
called-party transformations.
Transformation masks use mask operations that allow the suppression of leading digits, the
modification or preservation of digits, and the insertion of digits.
A mask operation requires two pieces of information: the number to mask and the mask
itself.
In the mask operation, CUCM overlays and aligns the number with the mask so that the last
character of the mask aligns with the last digit of the number. CUCM uses the corresponding
digit of the number wherever the mask contains an X. If the number is longer than the
mask, the mask obscures the extra digits.
Figure 12-9 illustrates an approach typically used to change the ANI of internal callers
when they make calls to the PSTN. In this example, the five-digit extension of 45000 is
changed to a ten-digit pattern for the purposes of caller ID on the PSTN. Caller ID refers
to the presentation of the calling-party name and number, whereas ANI refers only to the
calling number. Caller ID is being used in this book to represent the presentation of the
calling-party number. In the example, the mask applied to 45000 has changed the 45 of
the calling party to 36, and five digits are prefixed before the number so that users
connected to the PSTN can return phone calls to the presented number.
CUCM
User Dials:
9101028812145551212
Called Party:
1 214 555-212
Match: 9.@
Discard:
PreDot 10-10-Dialing
IP
PSTN
292 Chapter 12: Digit Manipulation
Figure 12-9 Transformation Mask Operation
Figure 12-10 illustrates a process in which a ten-digit phone number is being changed into
an internal five-digit extension. When a mask is applied to either a calling- or called-party
number, the digits are matched from right to left. If a ten-digit pattern has a five-digit mask
applied to it, the resulting number will include only five digits. The example is changing the
65 to a 45. If a digit is provided in a mask, it will override the original digits. The X
character will allow the original digit to be preserved.
Figure 12-10 Transformation Mask Operation
Transformation masks are configurable at route patterns, translation patterns, and route lists
(per route group).
The calling- and called-party transformation settings that are assigned to route groups in a
route list override the corresponding transformation settings that are assigned to a route
pattern. Route-pattern transformations apply only when a route pattern is pointed directly
to a gateway. Route patterns are normally pointed to a route list. Multiple route patterns can
point to the same route list, but multiple route patterns cannot point directly to the same
gateway. Inserting gateways into route groups allows the gateways to be used for many
different route patterns.
Transformation masks are usually applied at the route-list level. In this way, a different
transformation mask can be assigned for each route group in the route list.
Most calls between clusters of the same company have two route groups: a PSTN route
group and an IP WAN route group. The IP WAN route group includes one or more
intercluster or SIP trunks, and the PSTN route group may contain one or more gateways
An X in a Mask Lets Digits Pass Through 45000
Mask 8086236XXX
8086236000
Digits in Masks Replace Number Digits
Blanks Block Number Digits
8082365000
Mask 45XXX
45000
Translation Patterns 293
that connect to the PSTN. When CUCM uses a trunk from the IP WAN route group, CUCM
forwards the internal extension number (five digits if the internal dial plan is using five-digit
dialing). When CUCM forwards a call to a gateway in the PSTN route group, the network
administrator applies a mask that transforms the number into an E.164-compliant phone
number that can be routed over the PSTN.