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  • Writer's pictureVoIP Express

What Is Voip Or Voice Over Internet Protocol?

Updated: Mar 15, 2021

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OK while the above statement is a little dramatic, the fact remains that the Telephony Network (dial-tone calling), started in the 1800s, was the largest machine ever until the end of the Millennium.

The PSTN, or Public Switched Telephone Network, is made up of circuit switched, older Bell-Labs technology, it actually still works quite well and, in part, it does still exist today. T1, PRI, FXS, FXO, E&M are still practiced technologies. Analog is in fact alive still.

However, there are significant benefits of moving the PSTN (circuit switched network) onto the all-consuming Internet. In order to do this, it must be made to look like computer traffic. Voice has to be processed or digitized, compressed, and packetized in order to be passed on to the Internet. It must be made into the “language” or protocol defined for VoIP (Voice Over Internet Protocol).

VoIP Infographic
VoIP Infographic

Voice Over IP: This is the means and methodology for digitizing, compressing, and packetizing voice to run over IP (Internet Protocol).

Voice Digitization: The process of turning voice into 1s and 0s. By taking an analog waveform (your voice) and sampling the input amplitude and frequency and creating a binary digital representation of your voice. Many people still remember the reverse effect of this which is having 1s and 0s turned into an analog waveform, or the wobble of the old dial up modems.

Compression: To be made to be smaller. Voice is highly compressible. The nature of voice is that only one person speaks at a time and we have pauses in between words, sentences, and phrases. Voice compression became prevalent in the 1990s when businesses were using 56K and Frame Relay WAN lines to transmit voice with their WAN data traffic. They did this in order to bypass heavy 90s long distance toll charges between their branch locations, lowering their phone bills sometimes by $1000s/month. This would lay the groundwork for enhancements in IP based voice which had the same challenges with latency, jitter, sequencing and bandwidth.

Packetization: To be made to traverse a network. The digitized-compressed voice is broken up and encapsulated, framed, and addressed in network packets or more specifically, Ethernet and Internet Protocol (IP) packets. Doing this allows for voice traffic to cross your Local Area Network and sometimes the public Internet the same way your computers and other network devices do.

Whenever VoIP is established at 2 endpoints (a phone conversation) this digitization, compression, and packetization occurs at both locations. VoIP endpoints can be IP Phones, PBXs, or VoIP modems. Along the path between the two endpoints, controlling network devices are involved in the assuring the transmission of the VoIP packets in a timely manner.

IP PBXs and VoIP modems are often described by different terms, Cisco refers to them as ISRs (Integrated Services Routers) using CUBE (Cisco Unified Border Element)… that’s a mouthful of acronym.


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