Switching
Class 5 SoftswitchAlso known as Local exchange switch, Subscriber switch
Definition
A Class 5 softswitch is a softswitch that serves end subscribers directly, the IP successor to the local exchange or “end office” (Class 5 in the North American hierarchy). It registers users’ phones, provides calling features such as voicemail, call forwarding, conferencing, IVR and hosted PBX, and hands external calls to trunks or Class 4 switches.
Typical Class 5 features
- Subscriber management: user accounts, extensions and device registration.
- Calling features: voicemail, call waiting, transfer, forwarding, do-not-disturb, hunt groups.
- Hosted PBX / multi-tenant: many businesses on one platform, each with its own dial plan.
- [IVR](/glossary/ivr), call queues and conferencing.
- Number management: DIDs, emergency calling and caller ID (DOD).
- Per-subscriber billing: retail rating, bundles and prepaid balances.
How Class 5 relates to Class 4 and PBXs
A Class 4 softswitch moves traffic between carriers; a Class 5 softswitch terminates it at subscribers. A business PBX is effectively a private Class 5 system for one organisation, while a Class 5 softswitch does the same for thousands. See Class 4 vs Class 5 softswitch.
In mobile networks, the equivalent role is played by the IMS core and its telephony application server.
Class 5 platforms and mobile lines
Because a Class 5 platform holds subscriber data, it also carries regulatory duties that transit switches usually do not, such as emergency calling with location, lawful intercept capability and number portability, depending on the country.
Service providers running a Class 5 platform can add mobile lines as a route through a GSM gateway, for example to give hosted-PBX customers local mobile numbers or backup routes where operators permit it. GSMCalls supports multi-site routing and prepaid billing for this model; see multi-site GSM gateway.
Frequently asked questions
What does Class 5 mean in telecom?
Class 5 was the local end office in the AT&T switching hierarchy, the exchange that connected directly to subscribers’ lines.
Is a hosted PBX a Class 5 softswitch?
A multi-tenant hosted PBX platform is a Class 5 softswitch; it provides subscriber features to many businesses.
Does a Class 5 softswitch do least-cost routing?
It can choose between trunks, but large-scale LCR across many vendors is normally a Class 4 function.