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What Is a Softswitch?

A softswitch (short for software switch) is software that is used for a purpose similar to that of a traditional voice circuit switch. Telecommunications companies used this software in their core network to control calls and process media streams. Unlike traditional switches, which used dedicated hardware to control calls, a softswitch functions in virtual space.

Softswitch History

Softswitches are part of an evolution of call switching:

  1. Switchboard operators. Human operators  manually routed calls in the first era of telephony. These operators routed calls by plugging the caller’s line into the recipient’s line.
  2. Strowger Switch. This early form of an electromechanical switch was the first automatic switchboard. An electromechanical switch uses electromagnetic energy to open and close its switches.
  3. Crossbar Switch. This is another form of the electromechanical switch. It connects several inputs and outputs in a grid comprising 10 horizontal and 10 or 20 vertical paths that connect at cross-points.
  4. Stored Program Control (SPC) Analog. Located in a system’s memory, this telephone exchange system provided advanced calling capabilities. Centralized SPCs use a single processor to manage 10‒100 calls per second. Distributed SPCs are more reliable and widely used.
  5. Digital Switches. A digital switch routes a telephone company’s digital signals across the backbone of its network. These switches receive converted analog signals from users and route them to the wide area network (WAN). They connect two or more digital circuits.
  6. VoIP Softswitch. The advent of VoIP technology brought with it softswitches that route VoIP calls and traffic across carriers. VoIP softswitches enable services such as call center services, IP PBX features, calling card platforms and various types of authorization.

How Does a Softswitch Work?

One of the main components of a softswitch is the call agent. Keep in mind that, in this case, the term “call agent” does not refer to a human customer service/support agent. Rather, it is a piece of technology that controls routing and signaling. The call agent manages functions like call routing, transferring, and bilking.  

Types of Softswitches

Softswitches are available in different classes, each providing certain applications. The first three classes (classes 1, 2 and 3) are used for large-scale applications. Class 1 softswitches are international gateways, whereas softswitches in classes 2 and 3 can link cities and, in some cases, states.

Class 4 and class 5 softswitches are the most commonly used among telecommunication companies, especially VoIP service providers. A class 4 softswitch can route traffic volumes across two destinations. Large corporations use these switches to deliver VoIP traffic and services across multiple networks.

Together, class 4 and 5 softswitches enable VoIP providers to route international calls. Hybrid versions of class 4 and 5 softswitches are also available.

Examples Use Cases

Softswitches play a central role in several telecommunications solutions. Here are some examples of use cases for VoIP softswitches.

  • GSM termination (e.g., systems that filter out spam and junk calls)
  • SIM management software
  • VoIP retail business (e.g., billing, routing, unconditional forwarding)
  • Prerecorded interactive voice responses (IVRs)
  • Other VoIP applications (e.g., conference servers, virtual attendants)


Softswitches provide the following benefits.

  1. They are easily scalable. Compared to traditional switches, softswitches are relatively easy to scale up or down, depending on the size of the network. A VoIP softswitch can grow with the business, which can upgrade its softswitch via download.
  2. They are versatile. A VoIP softswitch can perform several functions, including routing, reporting, billing and monitoring. Businesses can integrate softswitches with other software to further streamline operations.
  3. They enable accurate billing. VoIP softswitches enable providers to customize call rates and generate precise invoices for each of their customers. Softswitches therefore free up time and resources, which businesses can direct to their core operations.
  4. They are cost-effective. Unlike traditional switches, softswitches do not require additional hardware. Implementing and upgrading the software occurs in virtual space.

Softswitch Technology

The calling agent in a softswitch coordinates with gateways, which in turn interface with various networks. For example, media gateways interact with IP (Internet Protocol) servers, ATM (Asynchronous Transfer Mode) networks, PBXs (Private Branch Exchanges), IAD (Integrated Access Devices), cellular networks and (in some cases) satellite phones.

These networks play different roles. IP servers transmit data such as VoIP and SIP (Session Initiation Protocol) Trunking on the internet. ATM networks carry voice, data and video in cells instead of packets. Cellular networks wirelessly retrieve voice and data.

Softswitches do not directly interface with end users as switching occurs in central locations. For example, a softswitch may be located near a VoIP service provider’s server. Separate networks rely on softswitches for coordination. (More on that later.)

VoIP softswitches coordinate with other VoIP or PSTN softswitches. When an internet user needs a VoIP softswitch to make a call, the softswitch starts by searching its database for the recipient’s IP address. If the address is not in the database, the softswitch relays the request to other softswitches until the recipient’s IP address is located. The call is then transferred to the PSTN.

How Bandwidth is Involved with Softswitches

Bandwidth is considered to provision softswitch software on a large scale. Our Points of Presence (POPs) are essentially massive switches that our customers can use to obtain the functions of traditional voice circuit switches. This enables our customers to control and process calls over a communications network. These capabilities are a part of Bandwidth’s UC Voice Product overview which allows UC providers to wrap voice, 911 access, and messaging into their offering. Bandwidth makes this transition easy with our private label SIP Trunking solution.

What Are the Benefits of Bandwidth’s Softswitch Services

Since Bandwidth owns and operates one of the largest All-IP Voice Networks in the nation. Our customers are able to enjoy fast, reliable communication services, scalability, and cost savings. Bandwidth offers our customers world class support with a 24/7 Network Operations Center (NOC) that is there to address issues as soon as they arise. In addition, Bandwidth’s communication services are built to scale. Whether you are a small start-up or an enterprise giant, Bandwidth services can scale to meet your needs. In addition, partnering with Bandwidth lets you avoid dealing with a middleman. This means more cost savings for your business while connecting with a service you can trust. Bandwidth has mastered unified communications (UC) voice services, so you can focus on what matters most to you.

Frequently Asked Questions

What are the applications of class 4 and class 5 softswitches?

A class 4 softswitch features an intelligent call routing component that helps to minimize latency, congestion and cost. The component also has several elements, including VoIP call quality. Another component that a class 4 softswitch may include is a billing feature. VoIP providers use class 4 softswitches to generate reports of incoming and outgoing calls.

A class 5 softswitch (also called an IP switch) routes calls between end users over relatively small areas. This switch routes calls to a specified IP address, Session Initiation Protocol (SIP) address or Direct Inward Dialing (DID) number.

Which softswitch should I use for my small/midsized business?

Class 5 switches are the most widely used among small and midsize businesses. These softswitches offer advanced features such as blind call transfer, auto-attendant, caller ID, call forwarding, audio/video conferencing support and interactive voice response (IVR). These switches allow VoIP providers to meter minutes and automatically bill consumers. Moreover, class 5 softswitches support authorization by number, IP number and prefix or log-in credentials in the case of SIP authorization.