| 摘要 |
In an environment of competitive local and interexchange carriers, offering number portability between local carriers serving a common region and between switches serving that region, each local carrier accesses a regional database to determine the identity of the carrier and switch serving a local customer. In addition, interexchange carriers access a national database to determine the identity of the carrier and switch serving the customer specified by the number dialed by an originating customer. For customers requiring high reliability service, alternate carriers can be used to serve such customers in case the primary carrier is unavailable; the databases identify these alternate carriers. Advantageously, this arrangement allows a high degree of freedom of movement of customers between carriers and geographic relocation without requiring a number change.
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