Many EAGLE protocols infer digit string formatting based on a protocol-specific Nature of Address Indicator (NAI) value. NPP uses this same concept to help isolate digit strings. NPP defines NPP-specific FNAI Classes to which services can map service-specific NAI values.

Services that invoke NPP processing provide an incoming NAI value along with the incoming digit string. NPP maps the incoming service-specific NAI value to an appropriate NPP FNAI Class mnemonic value.

NPP supports six different FNAI Classes:

The execution of the NAI-to-FNAI Class algorithm is described in Figure 3-1. Any NAI value not mapped to an FNAI Class is interpreted as UNKN (Unknown). If support is not needed for an FNAI Class, the FNAI Class value is NONE.

Many EAGLE features search for matching digit patterns at the beginning of digit strings to determine if processing is required. NPP provides this function with a Filter Prefix (FPFX).

An FPFX value can be a hexadecimal string of digits that are located at the beginning of an incoming digit string, such as d, 919, 060, or 9090). For example, the incoming digit string 00152558776925 would match a Filter Prefix (FPFX) of 001.

An FPFX value can be a wildcard (*) to match any leading digit string.

When the NPP Unlimited SDWC Chars feature is turned on, an FPFX value can be a series of hexadecimal digits that includes up to 3 single digit wildcard characters (?) in the first 6 digits of the string (except the last digit if the string is less than or equal to six digits). For example, the incoming digit strings 00152559776925 and 00252559886925 would match a Filter Prefix of 00?525.

When the NPP Unlimited SDWC Chars feature is turned off, an FPFX value can be a series of hexadecimal digits that includes single digit wildcard characters (?) in any positions except the last digit of the string. The total number of single digit wildcard characters used in all of the filters in the Service Rule Set for a service cannot exceed 25.

An FPFX value can be a series of hexadecimal digits that includes up to 3 single digit wildcard characters (?) in the first 6 digits of the string. For example, the incoming digit strings 00152559776925 and 00252559886925 would match a Filter Prefix of 00?525.

An FPFX value can be a series of hexadecimal digits that includes single digit wildcard characters (?) in any positions except the last digit of the string. The total number of single digit wildcard characters used in all of the filters in the Service Rule Set for a service cannot exceed 25.

When the FPFX filter parameter is defined in NPP, the leading incoming digit pattern must match the FPFX filter value for further NPP processing. See Searching NPP Filters with Wildcard Values for wildcard descriptions and examples.

NPP provides digit string isolation based on the incoming length of the digit string. The NPP Filter Digit Length (FDL) specifies the number of digits that the incoming digit string must have to match the Filter.

An FDL value can be a wildcard (*) to match a digit string of any length.

Table 3-2 illustrates NPP Filters, some with values for all components and some with wildcard values.

The following examples illustrate some specific NPP Filter scenarios:

• All standard national calls receive the same handling where NAI=NATL, digits XXXXXXXXXX
  • FNAI = NATL
  • FPFX = *
  • FDL = *
• International calls with International Escape Code where NAI=INTL, digits 011+XXXXXXXXXXXX
  • FNAI = INTL
  • FPFX = 011
  • FDL = *
• Collect calls with Operator Code, Area Code following the Operator Code, NAI=Unknown, digits 'b'+AC+9090+XXXXXXXX
  • FNAI = UNKNOWN
  • FPFX = b (or FPFX = b339090 or FPFX=b349090, and so on -- there are many options for this configuration)
  • FDL = 15

Filters can be defined that have wildcard values for the Filter Prefix (FPFX) value, the Filter Digit Length (FDL) value, or both values.

When the FPFX or FDL value is the wildcard character (*) , the value is considered to be categorically wildcarded; it contains no characters other than the * character.

Filters can be defined with specific digit FPFX values that include one or more of the single digit wildcard character "?" along with hexadecimal digits in the value.

Categorical Wildcarding

There are three search cases where categorical wildcard values are used. In each case the search algorithm considers only NPP Filters that have the wildcard value specified for the Filter criteria. If no specific match is found, NPP then searches the NPP Filters that have FDL=*, then the Filters that have FPFX=*. When searching with wildcard values for FDL or FPFX, NPP considers only the NPP Filters that are provisioned with wildcard values. NPP Filters with specific values and no wildcard values for FDL or FPFX, are not considered during wildcard searches.

Table 3-4 indicates the example Filter that is selected for each Filter selection scenario shown in Table 3-3.

Single Digit Wildcarding

When the NPP Unlimited SDWC Chars feature is turned off, a A Filter Prefix can include single digit wildcard characters (?) in any positions except the last digit of the string. The number of single digit wildcard characters used in all of the filters in the Service Rule Set for a service cannot exceed 25.

When the NPP Unlimited SDWC Chars feature is turned on, a Filter Prefix can contain up to 3 single digit wildcard characters (?) in the first 6 digits, but not the last digit if the string is less than or equal to 6 digits. An unlimited number of SDWC characters are allowed for each NPP service.

Based on the presence of the single digit wildcard value “?” in the Filter Prefix (FPFX), the Filter with the larger number of matching leading digits not involving the “?” wildcard will have priority. If the number of matching leading digits is the same for two Filters, then Filter priorities are established as follows: A non-wildcard digit has the highest priority, followed by the “?” wildcard, with the lowest priority assigned to Filters with no further digits to match.

For example, if two Filters exist with FPFX values of 12345678 and 12?45?78. An incoming digit string of 123456789 would be filtered by FPFX=123456789. An incoming digit string of 12a456789 would be filtered by FPFX=12?4.

Table 3-6 indicates the example Rule that is selected for each Filter selection scenario from Table 3-5.