Phone calls coming in from the Public Switched Telephone Network (PSTN) are often called DID or DDI calls. DID stands for Direct Inward Dialing, while DDI means Direct Dial In; both acronyms refer to the same thing. DID numbers are delivered by your telephone service provider. They can be delivered over VoIP connections (such as a SIP trunk) or via traditional telephone circuits, such as PRI lines. These phone numbers are sometimes called DID numbers or external phone numbers.
Routing a call requires two pieces of information: the phone number being routed and a destination for that phone number. In our example, we will use a DID number
8005551212. Our destination will be user
1000. Replace these ...