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VeriSign® Number Portability

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How It Works: Ported Number Call Flow

1. Customer dials a number that is ported.
2. The Service Switching Point queries an internal table that identifies all NPA-NXXs that are portable.
3. If the number dialed is portable, the SSP will determine if a query should be launched by analyzing call conditions.
4. If query conditions are met, the SSP formulates and launches an SS7 TCAP query to the Number Portability Databases.
5. The originating switch receives the NPDB response, analyzes and translates the number using NP routing tables, and determines an ISUP route out of the switch.
6. The call is routed to the recipient switch.
7. The call is completed to the ported number.

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