Reading your carrier's rate deck for outbound dialing

A rate deck is the price list your carrier hands you: a spreadsheet of destinations and the per-minute cost to call each one. If you dial outbound at any volume, this file decides your monthly bill, so it is worth learning to read.

What a rate deck actually contains

Every row in a rate deck maps a destination to a price. Your Carrier sells you minutes over a Trunk, and the deck tells you what each minute costs depending on where the call lands. The columns vary by provider, but you will almost always see these:

• Destination prefix or NPA-NXX. In North America the deck breaks pricing down by area code and the first three digits of the local number (NPA-NXX), so calls to one region can cost more than another.
• Rate per minute. The headline number, usually in fractions of a cent for domestic US/Canada.
• Billing increment. How the carrier rounds call duration, written as initial/subsequent, for example 6/6 (six-second blocks) or 60/60 (full-minute rounding).
• Effective date. Carriers reprice routes often, so always check you are looking at the current deck.

NPA-NXX, LRN, and why the math is not obvious

The number you dial is not always the number you pay for. Many North American numbers have been ported between carriers, so the destination's real owning switch is found by an LRN (Location Routing Number) lookup. Your carrier dips a database, finds the LRN behind the dialed number, and rates the call on that LRN's NPA-NXX rather than the original. A call that looks like a cheap local number can rate to an expensive route once the LRN resolves it. This is normal, not a billing error.

Here is the lookup path a single number takes from dial to cost:

flowchart LR
  A[Dialed number] --> B[LRN lookup]
  B --> C[Owning NPA-NXX]
  C --> D[Rate-deck row]
  D --> E[Per-minute rate]
  E --> F[Apply billing increment]
  F --> G[Call cost]

Billing increments add up faster than the rate

On a predictive dialer most connects are short. With 60/60 rounding, a 12-second call bills a full minute; with 6/6 rounding it bills 12 seconds. At thousands of short calls a day the increment can matter more than a fraction of a cent on the rate itself.

Why this feeds least-cost routing

Once you can read a deck, you can compare two carriers row by row and send each destination down whichever trunk is cheapest for it. That is exactly what least-cost routing does: it uses Least-cost routing logic in the Dialplan to pick a route per number. Without rate decks you are guessing; with them you route on real prices. Carriers usually quote rates against E.164-formatted numbers, so normalize your leads to E.164 before you compare destinations.

Reading the deck is one piece of getting carriers right. For the full picture, see our VICIdial carrier integration guide, which covers trunks, dialplans, and routing end to end.

You bring your own carrier and rate deck; we give you a dedicated VICIdial server to point them at, provisioned in under 40 seconds. See our plans to get started.