Assigning Telephone URIs

A concept that can seem foreign to traditional voice administrators is that users are assigned a Line URI instead of an extension. These URIs are composed of a Direct Inward Dialing (DID) number, which is unique both internally and across the PSTN, or the URIs can be based on extensions that are unique only to the organization. The point here is that users are not simply an extension attached to a phone; their user account is associated to a Line URI that follows their account and all endpoints.

When assigning URIs to end users, keep in mind that all URIs within the organization must be unique. Typically, organizations with multiple sites have multiple DID ranges per office, or extensions that are unique only within a specific site. To accommodate these scenarios, multiple dial plans and normalization rules can be created to accommodate the expectations of end users. URIs are also assigned in the E.164 format, which resembles tel:+14157773234.