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Glossary · Numbering

What is DNIS (dialled number identification service)?

  • Also called: dialed number identification service, dnis number

Reviewed by Sujan ThapaliyaLast updated

Definition

DNIS is the number the caller dialled, passed to the receiving system so it knows which of its own numbers was used. It is what lets one phone system answer dozens of numbers differently — by campaign, by department, by language, or by advertisement.
The three STIR/SHAKEN attestation levels, which underpin how dnis (dialled number identification service) behaves in practice: A asserts both that the carrier knows the customer and that the customer may use the calling number, B asserts the customer only, and C asserts neither. A shared number pool can reach B at best, which is why number ownership keeps recurring in these definitions.
Attestation is the backdrop to most caller-ID and deliverability terms, dnis (dialled number identification service) included.

In practice

How dnis (dialled number identification service) actually works

DNIS is the mechanism underneath call tracking. Give each advertisement, landing page or campaign its own number, and the DNIS on the inbound call tells you which one produced it, before anyone says a word.

It also drives routing. The same team can answer a sales line, a support line and a partner line with a different greeting, queue and priority for each, because the system knows which number was dialled.

ANI answers who is calling; DNIS answers what they are calling about. Most sensible inbound routing uses both.

DNIS also survives transfers and queues, which is what makes campaign attribution hold up end to end. A call that entered on a campaign number and was transferred twice still carries the number it arrived on, so the conversion can be credited to the advertisement rather than to the department that closed it.

Worked example

Ten regional numbers pointing at one queue: the DNIS tells the platform which region the caller responded to, so the greeting, the routing and the attribution all follow the number they dialled.

DNIS (dialled number identification service): common questions

What is DNIS used for?
Telling a phone system which of its numbers was dialled, so it can greet, route and report differently per number. It is the basis of call tracking and of running many campaign numbers into one team.
How is DNIS different from ANI?
ANI is the calling number; DNIS is the number that was called. One identifies the caller, the other identifies the destination they chose.
Do I need a separate number per campaign?
If you want to attribute calls to campaigns, yes — that is what makes the DNIS meaningful. The numbers are cheap; the alternative is asking every caller how they found you and trusting the answer.

Sources

  1. Combating Spoofed Robocalls with Caller ID Authentication — Federal Communications CommissionThe STIR/SHAKEN framework, the attestation levels carriers sign calls with, and the mandate requiring providers to authenticate caller ID.
  2. 47 U.S.C. § 227 — Restrictions on the use of telephone equipment — Cornell Legal Information InstituteThe Telephone Consumer Protection Act itself — the consent requirements, calling-hours limits, and private right of action.
  3. ITU-T Recommendation E.164 — The international public telecommunication numbering plan — International Telecommunication UnionThe international number format, the 15-digit maximum, and how country codes and national numbers compose.

See dnis (dialled number identification service) in the product

Call tracking assigns unique phone numbers to marketing sources, or swaps the number on your website per visitor, so every inbound call is attributed to the campaign, keyword, or ad that produced it. It closes the loop between ad spend and actual phone conversations.

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