Class 4 vs Class 5 Softswitch: What’s the Difference?

Wholesale and retail VoIP operators often hear Class 4 and Class 5 when evaluating a softswitch. The labels come from the traditional telephone network but describe two different roles: carrier transit versus subscriber services.

Class 4 softswitch

A Class 4 (transit/tandem) switch routes high-volume traffic between carriers. It does not serve end subscribers directly.

Typical duties: wholesale termination and origination, LCR, protocol conversion (SIP/H.323), high channel capacity, interconnect billing, and carrier-scale anti-fraud.

Class 5 softswitch

A Class 5 switch connects end users and business customers with features they expect: DIDs, IVR, voicemail, forwarding, hunt groups, and self-service portals.

How they differ

• Users — Class 4: carriers; Class 5: subscribers and SMBs
• Traffic — Class 4: few trunks, high volume; Class 5: many accounts, richer features
• Billing — Class 4: per-minute interconnect; Class 5: retail packages and balances
• Metrics — Class 4: ASR, PDD, margin; Class 5: ARPU, churn, feature use

One platform or two?

• Wholesale-only — Class 4 is essential; Class 5 optional unless you resell with sub-accounts.
• Retail-only — Class 5 is core; some destinations still need wholesale peering behavior.
• Hybrid — Both on one stack avoids duplicate routing tables, CDR silos, and monitoring gaps.

Summary

Class 4 is transit and wholesale economics; Class 5 is subscriber service delivery. Growing operators usually need both capabilities aligned on shared routing, billing, and quality data.