There are a few reasons why customers would want to deploy Direct Routing instead of Telstra Calling for Office 365.
- Connect the PSTN trunk – One of the reasons why customers want to use Direct Routing is that the Calling Plans are not available in all regions. And if you have an office outside of Australia then TCO is not an option, unless you want to provide them with an Australian telephone number.The list of Calling Plans is available at the following link: https://github.com/MicrosoftDocs/OfficeDocs-SkypeForBusiness/blob/live/Teams/downloads/country-and-region-availabilty/country-and-region-availability-(v-06252018)-(en-us).xlsx?raw=true)
* Direct Routing can provide access in most countries, except where Microsoft does not sell Office 365.
- Another reason to interconnect the PSTN trunk is that customers might have an existing contract with their telco that they cannot break.
- Interoperability with third-party systems (for example, PBXs, Call Centers) – The second reason is to provide the interoperability between existing telephony entities and Microsoft Phone System. This scenario allows customers to migrate to the cloud gradually, move users to a TCO 365 offering where available, leave users requiring specific functionality, (which Microsoft does not currently support on third-party on-premises voice infrastructure (example: PBXs, Call Centers)) and configure interoperability between the systems.
