VoIP Test 
| VoIP Test |
|
VoIP ( Voice over Internet Prptocol) system is a Packet Switched System, comparing with Circuit Switched System, VoIP doesn’t have a dedicated circuit for the call you made, and the QOS ( Quality of Service) is a very important issue, there are various factors affect the quality of VoIP Calls, the most important factors are: * Delay : Delay causes two problems: echo and talker overlap. Echo is caused by the signal reflections of the speaker's voice from the far-end telephone equipment back into the speaker's ear. Echo becomes a significant problem when the round-trip delay becomes greater than 50 milliseconds. * Packet Loss : VoIP packet loss takes place when a large amount of traffic hits the network and causes it to drop packets. Packet loss should never exceed 1% and most service providers guarantee service levels with .5% or less packet loss. * Jitter : jitter is the variation of packet interarrival time. Jitter is one issue that exists only in packet-based networks. While in a packet voice environment, the sender is expected to reliably transmit voice packets at a regular interval (for example, send one frame every 20 ms). These voice packets can be delayed throughout the packet network and not arrive at that same regular interval at the receiving station (for example, they might not be received every 20 ms. The difference between when the packet is expected and when it is actually received is jitter. * Echo : echo is caused by the far-end point. The loudness of the echo on VoIP calls is no worse than PSTN calls. The difference is that because of the inherent delay induced by VoIP, echo is much more noticeable. There are many methods to compensate Packet Loss, Jitter and Echo cancellation.
|