Voip Faq - ZyXEL Communications P-2024 Series Support Notes

P-2024 Support Notes

VoIP FAQ

What is Voice over IP?
Voice over IP (VoIP) is an emerging technology based on the open IEEE standards. VoIP refers to the
transmission of voice data over the Internet. Various protocols are available for voice transport. The most
commonly used are SIP and H.323.
Voice over IP (VoIP) is an emerging technology based on open IEEE standards. VoIP refers to the transmission
of voice data over the Internet. Various protocols are available for voice transport. The most commonly used are
SIP and H.323.
How does Voice over IP work?
In VoIP, voice data is sent digitally in discrete packets through the Internet, not through the traditional circuit
switch of PSTN. To do so, an analog-to-digital converter is required at sender side to translate voice (analog
signal) to digital signal before transmission. At the receiver end, an analog-to-digital converter converts the
digital signal back to analog so the voice can be heard on the phone.
Why use VoIP?
Traditionally voice data is transmitted using circuit switching. Since circuit switching is designed to carry
voice, it does it very well. However, as broadband networks become a mainstream for network access and
technologies have evolved, we don＇t want to confine ourselves to just using text-based applications (such as
e-mail, instant messaging, etc.) for communication over the Internet. Thus, the convenience of voice
communication through the Internet has quickly become popular.
In addition, it would take a much longer time, more effort and money to implement new
features using circuit switching. Since the IP technology is a standard and various
applications are available, it is easier and more cost-effective to integrate new services
and applications using IP.
What is the relationship between codec and VoIP?
In order to send voice (analog signal) over IP, it first needs to be digitized. Codec is a technique used to digitize
analog signal into digital signals and vice versa. There are various speech codec available for VoIP. Each codec
has its advantages and disadvantages.
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