LCR Routing Explained: How VoIP Carriers Maximize Margin

LCR (Least Cost Routing) is how wholesale VoIP operators pick termination at the lowest cost that still meets quality rules. On a softswitch, LCR is live policy on every call — not a static spreadsheet.

What LCR does

For each destination prefix the switch compares vendors by rate, priority, and constraints (quality, capacity, regulatory rules), then selects a path that minimizes cost within policy.

Typical decision chain

• Normalize the dialed number (prefix rules, A/B-number policies)
• Match customer buy rate and vendor sell rates
• Drop blocked prefixes, exhausted capacity, or failed quality thresholds
• Rank routes by cost, percentage, or quality score
• Place the call with failover if the first choice fails
• Write a CDR for billing and margin analysis

LCR vs simple priority

• Fixed priority — simple but may leave margin on the table
• Load-sharing — spreads capacity; cost may be suboptimal
• Quality-based — favors better ASR/ACD even if slightly more expensive
• Full LCR — dynamic ranking with quality floors and failover

Profitable networks usually combine lowest cost with quality guards.

Data you need

Accurate rate sheets with effective dates, live ASR/ACD/PDD per vendor, CPS/channel limits, and real-time margin by destination.

Common mistakes

• Routing to the cheapest vendor without FAS or ASR checks
• Stale vendor rates until billing shows negative margin
• No failover on single-vendor routes
• Ignoring A-number translation requirements

Summary

LCR drives wholesale margin. Pair cost ranking with quality thresholds, failover, automated rate updates, and route testing before vendors enter the pool.