Mitel MiVOICE BUSINESS, Engineering Manualline

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Network Configuration Concepts
209
MAINTAINING VOICE QUALITY OF SERVICE
As discussed in the previous section, the following issues affect voice quality of service over
IP connections:
• End-to-end delay
• Jitter or delay variation
• Packet loss
- Due to link congestion resulting in discarded or out of sequence packets
- Due to lack of or incorrectly configured QoS controls on LAN and WAN connections
- Due to forced discard of packets caused by excessive jitter
The following sections discuss tools, methods, and guidelines to help in assessing the quality
of service:
• “Network Measurement Criteria” on page 210
• “Bandwidth Requirements” on page 210
• “Serialization Delay” on page 211
• “Network Priority Mechanisms” on page 212
• “Full Duplex and Half Duplex Settings” on page 222
VOIP READINESS ASSESSMENT
An assessment of the LAN should be conducted prior to installing VoIP equipment. The
assessment can provide the following information:
• Determine if an IP network is currently capable of handling VoIP traffic and at what capacity.
• Document the tested VoIP call capacity and characteristics of an IP network.
• Determine the cause of voice quality problems encountered within an IP network, locally
or remotely.
Typically, networks are designed to handle peak traffic. It is important to determine how well
VoIP will perform on a network by measuring simulated VoIP traffic and calculating voice quality
based on a Mean Opinion Score (MOS). Some networks only require minor modifications to
deliver reliable, high-quality voice service. Others require more significant overhauls.
There are a number of products in the marketplace that can be used to perform a LAN
assessment. If you are having problems locating tools for conducting an assessment you should
contact Mitel Consultants and Integrators services. Alternatively Mitel Consultants and
Integrator services could carry out an evaluation.
The Mitel Consultants and Integrators can be contacted through the following pages on Mitel
On Line:
• http://domino1.mitel.com/mol/servsol.nsf/ServSolApp?OpenForm
• Or log on to Mitel On Line, > Services > Professional Services > Request a Quote