ZyXEL Communications P-2302R-P1 - Manual (Page 114)

P2302R-P1 Support Notes
All contents Copyright

2007 ZyXEL Communications Corporation.
114
Can H.323 and SIP interoperate with one another?
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 an 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 a algorithm which converts analog signal into digital signal and vice versa. There are three main type
of waveform codec, source codec, and hybrid codec. Each consume different amount of bandwidth and provide
different voice quality level.
What is the relation of codec and VoIP?
As VoIP is a general term send voice information in digital form in discrete packets over digital network and
this digital network is public network, thus there maybe other packet such data packet uses network at the same
time. The codec choose is related to how much bandwidth voice packet will consume. In bandwidthwise
aspect the smaller amount of bandwidth used the better. But in voice aspect the higher quality the better.
What codec does the ZyXEL Device support?
The ZyXEL Device supports the following commonly used codec.

G.729 voice codec

G.711u-law voice codec

G.711a-law voice codec