Networking

9 Pages 2362 Words

100 milliseconds to sustain the Quality of Service (QoS) that users are accustomed to from the Public Switched Telephone Network (PSTN). Now let’s take a walk on the more detailed side of what VoIP is and how it works. First and foremost, VoIP is an emerging technology still in the early stages. A personal computer (PC) must capture an analog voice and convert it to a digital signal, compress the audio with a compression-decompression (codec) device and then move it into the IP protocol stack. The codecs are at the heart of any IP telephony software. It is an algorithm that transforms analogue signals into digital ones and vice versa. The next step is to access the network, which is the premise modem connected to the PSTN and channeled to the Internet Service Provider (ISP) modem. The next link in the chain of events is the IP network itself or the Internet. The current structure of the Internet can make it an unstable and unpredictable carrier. Finally, the voice packet must transition back from the IP network to the PSTN, to the receivers’ modem for conversion back into analog. Each of these steps adds more delay to the voice packets. A delay approximately of over 550 milliseconds, which is 400 msecs over the QoS acceptable limit, is found to occur. These delays and other issues are just some of the challenges facing the future of VoIP. WHY IS VoIP AN ISSUE? Between 1994 and 1997 ISP revenue grew from about $189 million to over $4.75 billion dollars, making it the telecommunications success story of the nineties. This extraordinary growth, coupled with relatively inexpensive connectivity for the typical user has helped drive the emergence of VoIP. To the typical personal user, this technology will mean nothing more than the ability to make “free” long distance phone calls. However, to the business world, this technology holds some very profound promises. It’s the ability to avoid long distance phone charges that has many sc...