Why Use Voip; What Is The Relationship Between Codec And Voip; What Advantage Does Voice Over Ip Can Provide; What Is The Difference Between H.323 And Sip - ZyXEL Communications Prestige 2304R-P1 Support Notes

Voip station gateway

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Prestige 2304 Support Notes

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.

Why use VoIP?

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.

In order to transfer voice (analog signal) over IP it first need to be digitized. Codec is a technic to digitize

analog signal to digital and vice versa. There are various speech codec available and can be used with VoIP

each with it's advantage and disadvantage.

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.

H.323 and SIP are proposed by different group Session Initiation Protocol (SIP) is a standard introduced by the

Internet Engineering Task Force in 1999 to carry voice over IP. Since it was created by the IETF, it approaches

voice and multimedia from the Internet, or IP, perspective of view. Where as H.323 emerged around 1996, and

as an International Telecommunication Union standard it was designed from a telecommunications perspective.

Both standards have the same objective - to enable voice and multimedia convergence with IP protocols.

In interoperability between the two, the industry is making slow but sure progress. Interoperability must first

happen between vendor implementations of the same protocol (SIP-to-SIP and H.323-to-H.323) and then

between protocols. Currently in order for SIP client to talk to H.323 client the ITSP must have a trunking

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