What is a Class 4 softswitch?
A Class 4 softswitch routes wholesale, carrier-to-carrier voice traffic using least-cost routing and high call-per-second capacity, with no end-user features like voicemail or extensions.
What's the difference between a Class 4 and Class 5 softswitch?
A Class 4 softswitch handles wholesale routing between carriers. A Class 5 softswitch provides retail, end-user telephony features such as voicemail, IVR, and conferencing. CelloIP builds both, often on the same FreeSWITCH cluster for smaller carriers.
Class 4 Softswitch Development
Wholesale, carrier-to-carrier VoIP routing built on FreeSWITCH and Kamailio — least-cost routing, high-CPS signalling, billing/CDR settlement, and fraud protection for carriers and transit operators.
What We Build
Least-Cost Routing (LCR) Engine
Rules-based LCR routing that selects the cheapest viable carrier route per call, with real-time rate table updates, failover chains, and quality-based (ASR/ACD) route scoring.
High-CPS SIP Routing
Sofia-SIP (FreeSWITCH) or Kamailio-based routing engineered for high calls-per-second wholesale traffic, with load balancing across multiple media/signalling nodes.
Wholesale Billing & CDR
Real-time CDR ingestion for carrier settlement, rate-per-destination billing, margin reporting, and reconciliation against upstream carrier invoices.
Fraud & Traffic Pumping Prevention
Real-time anomaly detection on call volume, destination patterns, and ASR/ACD ratios to catch fraud and traffic pumping before it becomes a carrier dispute.
SBC & Carrier Interconnect
Kamailio/OpenSIPS session border controllers handling SIP trunk interconnects with multiple upstream and downstream carriers, protocol normalization, and codec negotiation.
Route & Margin Analytics
Real-time dashboards for route performance, per-carrier margin, ASR/ACD trending, and capacity planning across your entire wholesale voice traffic footprint.
Class 4 vs Class 5 Softswitch
The distinction that determines your architecture — wholesale routing vs retail telephony features.
| Aspect | Class 4 Softswitch | Class 5 Softswitch |
|---|---|---|
| Primary function | Wholesale, carrier-to-carrier call routing | Retail, end-user telephony features |
| Typical users | Carriers, wholesale VoIP providers, transit operators | Businesses, hosted PBX subscribers, call centers |
| Core logic | Least-cost routing (LCR), failover, rate arbitrage | Voicemail, IVR, conferencing, extensions |
| Billing model | Per-minute settlement between carriers | Per-seat or per-extension subscriber billing |
| Typical CPS | High — hundreds to thousands of calls/second | Lower — bounded by subscriber count |
| End-user features | None — no voicemail, no extensions | Rich — voicemail, IVR, call queues, conferencing |
Class 4 Softswitch FAQ
What is a Class 4 softswitch?
A Class 4 softswitch routes wholesale, carrier-to-carrier voice traffic — it handles least-cost routing (LCR) and high call-per-second volume between carriers, but has no end-user features like voicemail, extensions, or IVR.
What's the difference between a Class 4 and Class 5 softswitch?
A Class 4 softswitch routes wholesale traffic between carriers using least-cost routing logic and has no retail features. A Class 5 softswitch provides retail, end-user telephony features — voicemail, IVR, conferencing, extensions — for individual subscribers or businesses. Many carrier platforms run both layers together, with Class 4 handling transit traffic and Class 5 serving hosted subscribers.
What technology is used to build a Class 4 softswitch?
CelloIP builds Class 4 softswitches on FreeSWITCH or Kamailio for the routing/signalling layer, paired with a custom or open-source LCR engine, real-time CDR ingestion for billing, and a Kamailio/OpenSIPS SBC for carrier interconnect and fraud protection.
How much does Class 4 softswitch development cost?
A Class 4 softswitch with LCR routing, basic billing, and carrier interconnect for a small wholesale operation starts around $30,000–$60,000. A full carrier-grade platform with fraud detection, margin analytics, and high-availability clustering ranges $80,000–$250,000+ depending on scale and redundancy requirements.
Can a single platform run both Class 4 and Class 5 softswitch functions?
Yes — many CelloIP deployments run Class 4 wholesale routing and Class 5 retail features on the same underlying FreeSWITCH cluster, logically separated by routing rules and subscriber provisioning, which is more cost-effective than operating fully separate platforms for smaller and mid-size carriers.
Building a Wholesale VoIP Platform?
Book a free technical assessment with a CelloIP carrier VoIP engineer.