Avaya 555-245-600 Manual Do Utilizador

The effects of packet loss on VoIP service are multifold: 

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Problems caused by occasional packet loss are difficult to detect because each codec has 
its own packet loss concealment method (PLC). Therefore, it is possible that voice quality 
would be better using a compression codec (G.729A), which includes its own PLC, 
compared to a full bandwidth G.711 codec without PLC. 

●

Packet loss is more noticeable for tones (other than DTMF) than for voice. The human ear 
is less able to detect packet loss during speech (variable-pitch), than during a tone 
(consistent pitch).

●

Packet loss is more noticeable for contiguous packet loss than for random packet loss 
over time. For example, the effect of losing ten contiguous packets is worse than losing ten 
packets evenly spaced over an hour time span.

●

Packet loss is generally more noticeable with larger voice payloads per packet than with 
smaller packets, because more voice samples are lost in a larger payload.

●

In the presence of packet loss, the time for a codec to return to normal operation depends 
on the type of codec.

●

Even small amounts of packet loss can greatly affect a TTY/TDD device's (for 
hearing-impaired people) ability to work properly.

●

Packet loss for signaling traffic increases network traffic substantially when the loss 
exceeds 3%, possibly impacting voice quality.

Like packet delay, Avaya offers customers a tiered approach of recommendations to deal with 
network packet loss to balance new network costs and the constraints of business directives. 
The maximum loss of IP packets (or frames) between endpoints should be:

●

1% or less for best quality.

●

3% or less for Business Communications quality. Again, this quality is much better than 
cell-phone quality.

●

More than 3% may be acceptable for voice but may negatively impact signaling, which 
might degrade voice quality due to increased traffic. More information on signaling 
bandwidth requirements can be found in white papers on the Avaya Support website.

The Converged Network Analyzer (CNA) system is capable of providing continuous 
measurements of network packet loss (see 

on page 254). 

CNA can also generate alarms when network packet loss rises to levels that are detrimental for 
voice quality. For more information on CNA, see 

page 344.
Avaya’s VoIP Monitoring Manager (VMM) can measure packet loss for ongoing calls. The 
Agilent (HP) Internet Advisor, Finisar's Surveyor Explorer, Radcom's Prism, NAI's Sniffer, and 
others also measure packet loss.