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Posts Tagged ‘wan’

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.

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Dr Ping

What is the purpose? If you are curious to see how your broadband ISP measures up against competition in terms of latency to many different internet destinations, then Doctorping will help. It calculates a latency benchmark, which you can use to compare to others in your ZIP or state.

How to get your score: Please download the windows-only executable, doctorping.exe. Unpack it onto your desktop, find the doctorping program icon (looks like a bullseye with a red cross in it), and run it. Doctorping will check the latency to a class of internet routers spread through the US, and take your browser back to this page, to display your ping score, and your rank.

How is the score calculated?
The score is the MEDIAN of all the millisecond ping results. Those who remember high school stats know that the median is less sensitive to outliers (extreme results at either end of the spectrum).

What is a good score?
The lower the doctorping score the better. A good score is one that is top in your area (US state). A bad score is one that is bottom in your area.

What does it measure?
The measure is the average of the latency from you to many IP addresses, spread fairly evenly around the US. Some routers are near you, others are far away.

I’ve got a terrible score! What does that mean!
It means that your average latency is measured as relatively high. If others in your area, on the same ISP, score much better, it may indicate a problem with your line or setup. If others in your area, on the same ISP, also score badly, your ISP may not be efficiently routing you, compared to competing companies.

You can find out more about this tool at: http://www.dslreports.com/beta/doctorping

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.

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