49. - Quais são os retardos que acontecem na voz pacotizada ( VoIP )?
Autor: " Ricardo Prado " | Publicado: 2011-11-17T19:06:00-02:00

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São os seguintes :



• Retardos no
codec - são os retardos de codificação do sinal e de compressão. Embora a linha
VoIP possa usar sinal codificado e sem compressão ( G.711 - PCMU ou PCMA ), dificilmente
ocorrerá esta situação.



• Retardos de
pacotização - ocorrem na criação dos pacotes pela placa de rede Ethernet ou
equivalente do softphone.



• Retardos de
serialização - infelizmente os bits precisam ser colocados em série na linha,
assim como os pacotes inteiros, etc. Os buffers se encarregam de agir como um
funil.&nbsp;



• Retardos de propagação
- devido a propagação do sinal e cerca de 2/3 da velocidade da luz.



• Latência dos
equipamentos - Retardo na passagem do sinal por um roteador, por exemplo, e
calculado como o tempo gasto para o sinal entrar por uma porta e sair por
outra.&nbsp;



• Jitter -
Retardo variável devido as oscilações das condições da rede. O jitter é uma
praga para as redes pois pode acavalar um bit sobre o outro, provocar distorções
de fase, e seu efeito é semelhante a de uma tremura no sinal.

Além disso tudo,
não esquecer que em VoIP temos a atuação de 3 softwares básicos: IP, UDP e RTP,
cujos cabeçalhos empilhados consomem 16 kilobit/s.