Carrier-grade Class 4 routing
Route millions of minutes per day between carriers with least-cost routing, automatic failover and quality-based decisions made in under 12 milliseconds. The wholesale transit and termination engine behind the VOIXYS switch—built on Kamailio, CGRateS and RTPengine.
What a Class 4 softswitch actually does
A Class 4 switch sits between carriers. It handles transit and termination of high call volumes—taking SIP traffic from one operator and handing it to the next at the best price and quality. There are no subscribers, no voicemail and no IVR here: just signalling, routing logic and call detail records, optimised for throughput.
Subscriber-facing features—extensions, queues, voicemail—live in the Class 5 layer. Class 4 is built for one job: moving wholesale minutes reliably and profitably across interconnects.
- Transit & termination between operators, no subscriber features
- SIP & SIP-I interconnect with IP and digest authentication
- Least-cost & quality routing across multiple vendors
- CPS & concurrency policing per carrier and per route
- Per-call CDR for reconciliation, margin and dispute handling
Everything a wholesale carrier needs
Eight routing capabilities that turn raw SIP traffic into a profitable, resilient interconnect.
Least-cost routing (LCR)
Rank every destination by buy rate across all vendors and send each call down the cheapest viable route, with margin protection on every prefix.
Carrier interconnect
Onboard upstream and downstream carriers with IP or digest authentication, codec policy and per-peer capacity in minutes, not days.
Route plans & dial-peers
Build prefix-based route plans and dial-peers with priority, weight and percentage load-balancing across carriers for every destination.
Failover & re-routing
Roll over to the next route automatically on 4xx/5xx responses, timeouts or dead peers—so a failing vendor never costs you a call.
CPS & concurrency limits
Police calls-per-second and simultaneous channels per carrier, customer and route to honour commitments and stop traffic floods.
CLI & number manipulation
Rewrite caller ID and dialled digits per route—prefix stripping, E.164 normalisation, CLI substitution and presentation control.
Quality routing (ASR/ACD)
Weight routes by live answer-seizure ratio and average call duration, demoting low-quality carriers automatically to protect completion rates.
Real-time route testing
Fire test calls through any route plan before it goes live and watch the SIP ladder, codec and timing in real time to validate every change.
Built for wholesale scale
Numbers that hold up when you are routing a nation's worth of traffic.
Built on Kamailio for signalling and routing, CGRateS for real-time rate-aware decisions and RTPengine for media—battle-tested open source trusted by tier-1 operators to route billions of calls.
Route smarter, terminate cheaper
See how the VOIXYS Class 4 engine routes your traffic for the best margin and quality. Book a demo or check transparent wholesale pricing.