Software Components
Just like any other network, voip technology requires (besides physical devices) software to make it work properly.
In the voip technology software domain, two protocols have stood up to the challenge:
Just as important in the voip technology race are:
Most importantly, SIP doesn't provide for redundancy (making it unsuitable for carrier applications), doesn't support the emerging Differentiated Services/Policy Management approach to QOS and is rather limited interoperability testing track record (largely because the protocol is new, having only been ratified in February 1999).
Waveform CODECs are compression methods that use the redundant characteristics of the waveform itself.
In addition to waveform CODECs, you will find source CODECs. They compress your voice signal by sending only simplified parametric information about voice transmission; these CODECs require less bandwidth, than if it the whole voice was transmitted over the Internet. Source CODECs include linear predictive coding (LPC), code-excited linear prediction (CELP) and multipulse-multilevel quantization (MP-MLQ).
Each CODEC has a specific task that it does; in fact every voip technology CODEC provides a certain quality of speech. The quality of the speech signal transmitted is a subjective response of the receiver. A common benchmark used to decide the quality of sound produced by specific CODECs is the mean opinion score (MOS). What is MOS? With MOS, a wide range of listeners decide upon the quality of a voice sample (corresponding to a particular CODEC) on a scale of 1 (bad) to 5 (excellent). The scores are averaged to provide the MOS for that specific sample.
Voip technology is not that easy to implement. Mainly because of the fact that technology is still new and specialists are relatively hard to found. This also causes protocols to evolve rather slow, compared to other IT protocols.
In the voip technology software domain, two protocols have stood up to the challenge:
- H.323 and
- SIP.
Just as important in the voip technology race are:
- Quality of Service (QOS),
- Scalability/Flexibility and
- Interoperability.
Most importantly, SIP doesn't provide for redundancy (making it unsuitable for carrier applications), doesn't support the emerging Differentiated Services/Policy Management approach to QOS and is rather limited interoperability testing track record (largely because the protocol is new, having only been ratified in February 1999).
Codecs
VOIP technology also uses codecs so that it can transmit data to the destination a lot faster and securely. Pulse code modulation (PCM) and adaptive differential PCM (ADPCM) are examples of "waveform" CODEC techniques.Waveform CODECs are compression methods that use the redundant characteristics of the waveform itself.
In addition to waveform CODECs, you will find source CODECs. They compress your voice signal by sending only simplified parametric information about voice transmission; these CODECs require less bandwidth, than if it the whole voice was transmitted over the Internet. Source CODECs include linear predictive coding (LPC), code-excited linear prediction (CELP) and multipulse-multilevel quantization (MP-MLQ).
Each CODEC has a specific task that it does; in fact every voip technology CODEC provides a certain quality of speech. The quality of the speech signal transmitted is a subjective response of the receiver. A common benchmark used to decide the quality of sound produced by specific CODECs is the mean opinion score (MOS). What is MOS? With MOS, a wide range of listeners decide upon the quality of a voice sample (corresponding to a particular CODEC) on a scale of 1 (bad) to 5 (excellent). The scores are averaged to provide the MOS for that specific sample.
Voip technology is not that easy to implement. Mainly because of the fact that technology is still new and specialists are relatively hard to found. This also causes protocols to evolve rather slow, compared to other IT protocols.
