Carrier Lookup

Prefix-Based vs. LRN-Based Lookup

Prefix-based lookup matches the NPA-NXX against a static table. It's cheap, but reflects the original carrier assignment. When a subscriber ports their number — which happens 40,000–60,000 times per day in the US — a prefix-based lookup still returns the old carrier.

LRN-based lookup queries NPAC to find the current LRN, then maps it to the serving carrier. This reflects where the number actually routes today.

If a T-Mobile subscriber ported from AT&T two weeks ago, a prefix lookup returns AT&T. An LRN lookup returns T-Mobile. Sending to AT&T's SMS aggregator means the message goes to a gateway with no relationship to that subscriber — delivery fails. VRI uses LRN-based lookup exclusively.

Data Fields Returned by VRI Carrier Lookup

Field	Description
carrier.name	Human-readable carrier name (e.g., "T-Mobile USA")
carrier.ocn	4-character Operating Company Number
line_type	wireless, landline, voip, or prepaid
ported	Boolean — has the number ever ported?
messaging_provider.id	Aggregator or gateway ID handling A2P SMS for this number
messaging_provider.name	Human-readable messaging provider name
lrn	Current Local Routing Number
lrn_activation_date	When the current LRN became active (VRI exclusive)

Messaging Provider Is Not the Same as Serving Carrier

The serving carrier is the MNO (AT&T, T-Mobile, Verizon). The messaging provider is the entity that processes A2P SMS for that carrier's subscribers. These are not always the same company.

Getting this wrong produces 30007 (carrier violation) errors on 10DLC campaigns, silent message drops for MVNO-hosted lines, and SHAFT filter triggers from wrong-gateway routing. VRI returns the messaging provider ID alongside carrier data so you can route to the right gateway without guesswork.

Use Cases

• SMS routing: Route A2P messages to the correct messaging provider gateway. Prevents 10DLC campaign registration mismatches.
• Voice routing: Use LRN for correct PSTN routing. Stale prefix data causes SIP 404 errors on ported numbers.
• Fraud screening: VoIP numbers have significantly higher fraud rates for account takeover vectors. A number that looks "wireless" but returns as VoIP is a strong fraud indicator.
• TCPA compliance: TCPA programs require verification that a number is wireless before sending marketing SMS. Prefix-based data is not sufficient — use LRN-based lookup.
• List hygiene: Scrub contact lists to identify disconnected, ported, or line-type-mismatched numbers before campaigns.

Data Freshness Guidance

• Real-time lookup at send time is the gold standard for high-volume A2P messaging
• Lookups older than 7 days should be treated as potentially stale for numbers where ported: true
• Numbers with lrn_activation_date under 30 days should always be re-verified — recent ports mean recent routing table changes

For bulk operations, VRI supports batch lookup of up to 10,000 numbers per request with per-number freshness timestamps.

Accuracy and Latency Benchmarks

Metric	VRI Performance
LRN lookup accuracy	>99.5% for US numbers
Ported number detection	>99.8%
API p50 latency	45ms
API p99 latency	120ms
Batch throughput	10,000 numbers/request
Uptime SLA	99.9%

API Example: Carrier Lookup

curl -s "https://api.verirouteintel.com/v1/lookup" \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -G --data-urlencode "phone=+16505550142" \
  --data-urlencode "fields=carrier,line_type,messaging_provider,lrn,lrn_activation_date,ported"

Response:

{
  "phone": "+16505550142",
  "carrier": { "name": "T-Mobile USA", "ocn": "6529", "type": "wireless" },
  "line_type": "wireless",
  "ported": true,
  "lrn": "6505550001",
  "lrn_activation_date": "2026-03-15T09:12:00Z",
  "messaging_provider": { "id": "TMO", "name": "T-Mobile Messaging", "gateway_type": "direct" }
}

Pricing

VRI carrier lookup is $0.0009 per lookup — LRN-based data by default. Bulk pricing available for volumes above 10M lookups/month.

Related Terms

• CNAM