Numbers & trunks
DODAlso known as Direct Outward Dialing, Outbound caller ID
Definition
DOD (Direct Outward Dialing) is the ability of users on a PBX to place external calls directly, usually by dialling an access code or a full number, with the call leaving over a trunk and presenting a caller ID. On SIP trunks, DOD also refers to the outbound numbers a carrier authorises you to present.
How DOD works
When a user dials an external number, the PBX matches it against outbound routes (for example, numbers starting with 9 or +), strips or adds prefixes, and sends the call to the chosen SIP trunk. The caller ID is set in the From or P-Asserted-Identity header.
Carriers only let you present numbers you own or are authorised to use. In many markets this is enforced by law and technology: the US and Canada require STIR/SHAKEN caller-ID attestation, and regulators elsewhere block calls with invalid or spoofed numbers.
DOD vs DID
| DID | DOD | |
|---|---|---|
| Direction | Inbound | Outbound |
| Main purpose | Route a number to a destination | Place external calls with a valid caller ID |
| Configured in | Inbound routes | Outbound routes / trunk caller ID |
More in SIP trunks, DIDs and DOD explained.
Outbound calls over mobile lines
Outbound routes also decide which trunk carries each call. A PBX can send local calls to one provider, international calls to another and emergency calls to a trunk that supports caller location, falling back to a second trunk if the first is unavailable.
When a call leaves through a GSM gateway, the mobile network presents the SIM’s own number, as with any mobile call. GSMCalls routes outbound calls by prefix and failover rules to the right site and device; see features. Using mobile lines outbound must respect operator terms and the acceptable-use policy.
Frequently asked questions
Can I show any caller ID on outbound calls?
No. You may only present numbers you own or are authorised to use; carriers and regulators block or penalise spoofed caller IDs.
Is DOD the same as outbound calling?
Essentially yes; DOD is the traditional telecom term for users dialling out directly without an operator.
What is STIR/SHAKEN?
A North American framework in which carriers digitally sign the caller ID of outbound calls to show how confident they are that the caller may use that number.