A traffic simulator is typically used to stress the existing local area network to see if it can handle the addition of real-time audio. This might start out by placing 25 simulated voice calls on the local area network. As the number of calls increases, the voice quality tends to decrease, so an optimal balance must be achieved to arrive at the true call handling capacity of the network.
Striking this balance involves introducing Quality of Service into the network during the assessment phase. The objective is to change the behavior of the network so that data and voice traffic can get along over the available bandwidth. If this is not possible, additional bandwidth might be necessary and, if that is not possible, segmenting the network might be the optimal solution. Another solution might be to prioritize voice traffic.
The settings of the LAN switches classify all the network traffic and mark the different traffic types with their own priority levels. Voice should have first crack at the bandwidth, since it is a real-time application. Bursty data applications are usually next in line, starting with database access, followed by HTTP for Internet access and FTP for file transfers, with email getting whatever bandwidth is left for best-effort delivery.
A network assessment will also include the routers at each office location, which handle voice packets over the WAN. This is important because today’s LANs operate at 1,000 Mbps or more, whereas most WAN connections are slower. The number of concurrent voice calls on the LAN can be much greater than the number of concurrent calls that can be supported on the WAN.
As with the LANs at each location, an assessment must be made of the kinds of applications that traverse the WAN, and then adding simulated voice traffic to check its performance against industry standards until satisfactory audio quality is achieved. Like LAN switches, routers can be configured to handle voice traffic over routine data traffic.
Sometimes a firewall will be set to enforce strong security measures to protect the internal network. This may block both phone signals and voice traffic. This issue is overcome by opening specific port ranges to allow signaling and voice traffic to securely pass through the firewall.
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