VoIP System Design Considerations

When installing and configuring the VoIP System, it is necessary to analyze and meet some design considerations to ensure the best quality and user experience. The design considerations cover available bandwidth and quality of service.

Bandwidth Requirements and Call Capacity

The available connection bandwidth determines the maximum number of simultaneous calls that the system can support with the appropriate audio quality. Before installing and configuring the LVS components, use this information to determine the maximum number of simultaneous VoIP connections that the system can support. For asymmetric connections, such as ADSL, the maximum number of calls is determined by the upstream bandwidth.

For more information about bandwidth calculation, refer to the following web sites:

Wide Area Network (WAN) Quality of Service (QoS)

You can choose from several types of broadband access technologies to provide symmetric or asymmetric connectivity to a small business. These technologies vary on the available bandwidth and on the quality of service. It is generally recommended that you use broadband access with a Service Level Agreement that provides quality of service. If there is not a Service Level Agreement with regard to the broadband connection quality of service, the downstream audio quality may be affected negatively under heavy load conditions (bandwidth utilization beyond 80%). To eliminate or minimize this effect, Linksys recommends one of the following actions:

  • For broadband connections with a bandwidth lower than 2 Mbps, perform the call capacity

calculations by assuming a bandwidth value of 50% of the existing broadband bandwidth. For example, in the case of a 2 Mbps broadband connection, assume 1 Mbps. Limit the uplink bandwidth in the Integrated Access Device to this value. This setting helps to maintain the utilization levels below 60%, thus reducing jitter and packet loss.

  • Use an additional broadband connection for voice services only. A separate connection is required

when the broadband connection services do not offer quality of service and when it is not possible to apply the above mentioned utilization mechanism.

Echo Elimination & DTMF Problems

The easiest echo to fix is:

  1. Echo that you or the person at the other end of the call always hears on a VoIP phone system when you’re talking on an analog line or trunk
  2. Echo that you or the person at the other end of the call always hears on a regular phone system connected to a VoIP phone line (adapter), and where you don’t hear the echo when you connect your butt-set directly on the line (with the phone system disconnected). Continue reading “Echo Elimination & DTMF Problems”

Smokeping

Here is a great tool that I’ve used over the years to help troubleshoot ISP latency issues and QoS issues when working with VoIP lines, but it can be used to troubleshoot all sorts of issues: Smokeping

You can use this wonderful tool at DSL Reports: http://www.dslreports.com/smokeping

What does SmokePing do?

SmokePing generates flexible graphs that, within hours, contain actual information about the quality & reachability of your IP address from several distributed locations.

Continue reading “Smokeping”

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