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P-2024 Support Notes
What advantage does Voice over IP provide?
VoIP provides advanced integration of text, video and voice in emails. This cannot be done using traditional
circuit switching (PSTN).
What is the difference between H.323 and SIP?
H.323 and SIP are proposed by different groups. 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. Whereas 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.
Can H.323 and SIP interoperate with each other?
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
gateway act as a translator between the two protocols without the truncking gateway the two protocols are not
able to communicate to one another.
What is voice quality?
Voice quality is how well a person can hear the voice on the opposite end.
How are voice quality normally rated?
Voice quality is most commonly rated through a voice quality metric called the Mean Opinion Score (MOS)
which is recommendation by ITU-T. The MOS is a 5-point scale where 5 represent excellent voice quality and
1 represent bad voice quality.
What is codec?
Codec is an algorithm that converts analog signal into digital signal and vice versa. There are three codeec
types: waveform, source, and hybrid codec. Each consume different amount of bandwidth and provide different
voice quality.
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