The history of telecommunication dates back to 1662, when Robert Hooke discovered that sound could be transmitted over a string into an attached earpiece or mouthpiece.

The telephone was invented two centuries later, in 1876. To understand how the invention of the telephone changed the world, read our blog on the history of the phone.

The history of VoIP (Voice over Internet Protocol) begins a whole century after the telephone was invented. While the telephone was invented to overcome the limitations of the telegraph, VoIP was invented to overcome the limitations of the landline phone.

Limitations of Landline Phones

Telephone systems are extremely reliable. Until the late 1900s, they were the most widely used form of communication. However, they had three big limitations:

1. Long distance calling was expensive.
2. A landline phone only worked from one geographical location.
3. Technology was aging and unsustainable at scale in the modern world.

Internet Calling

The first VoIP solutions used the internet to establish connections and transmit data. Initially, VoIP connections could only be established via a software application installed on both devices. This was called a Peer-to-Peer (P2P) connection. This technology was quite limiting because it meant that in order to connect, both users needed to have access to the same software application and be online at the same time.

Soon after dialup internet became widely available, in 1995, VocalTec Communications came out with the first commercial VoIP solution, and called it the Internet Phone. VocalTec capitalized on the biggest limitation of the telephone — they saved customers big on international and long-distance calling rates.

Interfacing with PSTN

While it was exciting to be able to make voice calls over the internet, it wasn't convenient enough for the widespread adoption of VoIP yet. People still used the telephone and its underlying PSTN (Public Switched Telephone Network) as the primary form of communication.

Hardware Reliance

Initially, a piece of hardware facilitated this analog-digital conversion and acted as a gateway between the PSTN and the internet. In the late 1990s, hardware manufacturers began producing equipment that supported analog-digital conversion. Although this made VoIP technology less reliant on computers, it was still tethered VoIP to physical devices.

For Telephone Service Providers (TSP) who were slowly transitioning their legacy PSTN to VoIP, this was an expensive but inevitable option. TSPs were completely reliant on the vendor's hardware to deliver their service. TSPs could also not afford to build their own features, manufacture their own equipment and install it throughout their network. Essentially, the investment needed put feature creation out of reach for everyone in the telecommunications community except the biggest players.

Interfacing with PSTN

Initially, a piece of hardware facilitated this analog-digital conversion and acted as a gateway between the PSTN and the internet. In the late 1990s, hardware manufacturers began producing equipment that supported analog-digital conversion. Although this made VoIP technology less reliant on computers, it was still tethered VoIP to physical devices.

For Telephone Service Providers (TSP) who were slowly transitioning their legacy PSTN to VoIP, this was an expensive but inevitable option. TSPs were completely reliant on the vendor's hardware to deliver their service. TSPs could also not afford to build their own features, manufacture their own equipment and install it throughout their network. Essentially, the investment needed put feature creation out of reach for everyone in the telecommunications community except the biggest players.

What is SIP and how did it accelerate the adoption of VoIP?

In 1996, a Columbia University professor, Henning Schulzrinne designed the Session Initiation Protocol (SIP). SIP defines a set of protocols using which two or more devices on the internet can initiate an audio or video session.

SIP describes the following elements for a session:

• How to locate the other party
• Which CODEC (piece of software used to convert analog voice into digital signals, and vice versa) to use
• How to construct and send IP signalling packets
• How to manage the call

SIP is an open protocol that's free and available for anyone to use. Because SIP is also hardware and software agnostic, it voids the need for any proprietary VoIP hardware. SIP also allows for easier software upgrades and third-party integrations.

SIP has made VoIP easy to use. It has also made VoIP accessible to the broader telecommunications community, including TSPs, MSPs and ISPs.

The Future of VoIP

Although VoIP has been around for over two decades, the technology is just maturing. The scope of VoIP has exceeded well beyond its original definition. VoIP has become a malleable and resourceful tool that can be employed differently for different use cases.

As VoIP technology continues to evolve at breakneck speeds, we invite the telecommunications community to join SIPSTACK in our mission to uphold the original values that VoIP was founded on — making communication solutions accessible to everyone.