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Troubleshooting and analyzing VoIP networks
Speechless
Because of the way people perceive speech, Voice over Internet Protocol (VoIP) is a transmission-sensitive application that requires certain conditions in the network. Finding and fixing network problems on Open Systems Interconnection (OSI) model Layer 2 or 3 is almost trivial compared with VoIP analysis. In Internet telephony, the sources of error migrate to higher OSI Layers 4 through 7. VoIP also requires the correct interaction of all layers and thus increases the complexity of troubleshooting. Of particular importance is the end-to-end assessment of network parameters, such as available bandwidth, packet loss, delay, and jitter. In local area networks (LANs), a VoIP administrator can use a special VoIP analyzer to control the available bandwidth and the quality of voice transmission by monitoring the relevant network parameters (e.g., load, packet loss, and delays).
Effective Bandwidth
Effective bandwidth (EFB) describes the bandwidth available over the entire network path (end-to-end) at a specific point in time for the application or data flow in question. In a network, EFB is continually changing and depends on the number of simultaneous data streams. In most cases, EFB is determined by a few overloaded network connections or coupling elements. EFB is measured in bits per second (bps) and must be sufficient to transport the data successfully from the transmitter to the receiver. A deficit of bandwidth can lead to jitter and packet loss. The required bandwidth also depends on the voice codec selected.
VoIP places high demands on the available bandwidth, so you must know the network and prevailing bandwidth conditions. A VoIP analyzer displays these changes so you can see them at a glance (Figure 1).
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