Dial Plan are set of rules which translate the phone number dialed by user to E.164 format. E.164 is the international telephone numbering plan that ensures each device on the PSTN has globally unique number. This number allows phone calls and text messages can be correctly routed to individual phones in different countries. E.164 numbers are formatted [+] (country code) (subscriber number including area code] and can have a maximum of fifteen digits.
Microsoft Teams dial plans are categorized into 2 types:
- Service-scoped
- Tenant-scoped
Each user will be mapped with default Global (Org Wide) dial plan. Each user is automatically assigned the service country dial plan that matches the usage location assigned to the user. Service country dial plans are being managed by Microsoft and Teams admin cant make any changes onto these dial plans. User dialed a number it will checked against any custom Tenant-scoped dial plan. If there is nothing defined manually then it will fallback onto Service-Country dial plan associated with Usage location. So it’s not mandatory to define all normalization rules in tenant dial plans as they might already exist in the service country dial plan.
Now let’s try to understand it by an example:
User in France tried to dial Emergency number 112 from Teams client. User was checked against assigned Dial plan. In our case user is assigned with Global (Org wide) dial plan and no normalization rules are defined inside this dial plan. So next it will go for service-scoped dial plan which is inbuilt as a part of Microsoft country specific dial plan . And call will get routed to nearby PSAP services based on user Emergency address location specified during number assignment to the user.