ZyXEL Communications P-2000W V2 - Manual (Page 5)

P2000W V2 Troubleshooting Guide
All contents copyright (c) 2005 ZyXEL Communications Corporation.
1. What is VoIP?
Voice over IP is an emerging technology based on open standards of IEEE,
fundamentally the Internet Protocol that allows voice data to travel across the
Internet. There are many methods to use this technology, the most common
and well known are SIP, and H.323.
2. How does VoIP work?
Basically VoIP is a technique to send voice information in digital form in
discrete packets over digital network rather than by using traditional circuit
switch (PSTN). To do so we will need an analog to digital converter on
sender side to translate the voice (analog signal) to digital than transmit it, and
on the receiver end it will also need an analog to digital converter to covert the
digital signal back to analog to the person being called can heard the voice.
3. Why use IP for voice?
Traditionally telephony carrier use circuit switching for carrying voice traffic. As
circuit switching is designed to carry voice and it does it very well. Than why use IP
for voice? As broadband booms, and technology evolve. People now want to
communicate through various way not just voice such as email, instant messaging,
video and so on. Traditional telephony can not evolve as quickly as the demand and
develop new feature on circuit switch takes much time and money. IP is an already
exist standard and many type of service already runs on IP, by using IP as a platform
integrate service is now possible and low cost where traditional circuit may take long
time to achieve.
4. What is the relationship between codec and VoIP?
In order to transfer voice (analog signal) over IP it first needs to be
digitized. Codec is a technique to digitize analog signal to digital and vice
versa. There are various speech codec available and can be used with VoIP
each with its advantage and disadvantage.
5. What advantage does VoIP can provide?
The advantage of VoIP is it can provide advance services such as joining e-
mail, instant messaging, video, voice mail all together. Where current circuit
switching (PSTN) can not.