The Gateway Screening and MSU Tracing (GWST) is provisioned using screening table records. These records are indexed by an Entry Point Reference (EPR). Each EPR is a group of one or more records. The DSC - SP2000 Platforms support the following:

  • EPR attributes are alphanumeric strings with a maximum size of 4 characters as well as the digit range 10000 to 19999. The string is automatically capitalized.

  • up to 1024 screening records for each EPR

  • up to 4096 screening records for each NA (Incoming Linksets and App IDs)

  • up to 20000 screening records in all the screening tables

The screening table search results can

  • end the screening process by setting the Next Table as NOT APPLICABLE and the Next EPR to

    • STOP, where the message passes the screening

    • IGNORE or FAIL, where the message fails the screening and is discarded

  • be another screening table along with an existing EPR for further screening

  • be a redirection table along with an existing EPR for traffic redirection

Note

IGNORE and FAIL result in a slightly different behavior for gateway screening. In GWST, IGNORE fails the screening, but the result is not logged. FAIL reports a Discarding MSU paced log with the MSU hexadecimal output and the responsible screening table name and EPR to the debuglog. For more information, see the details below.

All screening tables can access the Redirect to AppIDs table as their next step. Only pre-GTT screening tables (excluding Allowed SCCP CLD PAs and Affected SCCP Mgmts) can access the Redirect to PCs table as their next step.

Discarded MSUs on the debuglog show the table name that caused the discard as well as the relevant EPR value that is associated with the failed table name. The unique combination of the table name and the EPR value is used to control the number of identical failure cases reported in the debuglogs and allows for improved diversity in MSU discards reporting. For an example of a debuglog file, refer to GWST Administration.

The Gateway Screening MSU discard reporting can record up to double the pace limit if enough different table name and EPR value combinations are hit. For example, if the logging limit is ten, then up to twenty discarded MSUs can be logged in an interval, as long as each has a different table name and EPR value. 

The discarded MSUs logging feature is configured by the GWST attributes Max Reporting Per Interval and Reporting Interval on the Logging Configuration screen of the GWST Configuration object.

To fully disable the feature, set the Max Reporting Per Interval attribute to DISABLED (0) or disable the feature on a per record basis by setting the Next EPR attribute to IGNORE.

For more information about logging configuration, refer to Configuring GWST Configuration.

To trace MSUs on the system, MSUs are assigned a unique, internal reference number and are logged accordingly to the debuglog as they are passed through system processes. The MSU Tracing feature uses the screening tables to identify which MSUs are to be traced by setting the associated screening records MSU Tracing attribute to ENABLED on the Feature screen.

  

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