Mitel 5560 IPT none Specifications download pdf (Page 219)

Network Configuration Concepts

205

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 206

• “Bandwidth Requirements” on page 206

• “Serialization Delay” on page 207

• “Network Priority Mechanisms” on page 209

• “Full Duplex and Half Duplex Settings” on page 218

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

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Mitel 5560 IPT none Specifications Page 219