Avaya BCM 2.0 IP Telephony Instrukcja Użytkownika Pobierz pdf (Strona 11)

Overview 11

P0911590 Issue 02 Enterprise Edge 2.0 IP Telephony Configuration Guide

The VoIP Gateway monitoring function can take about 3 mins to respond to

marginal changes in the network condition. Fallback can be caused by any of the

following reasons:

• Bad network conditions.

• The remote gateway is out of service.

• No network connection.

• Not enough DSP resources available.

Packet loss

Packet loss is the percentage of packets that do not arrive at their destination.

Transmission equipment problems, and high delay and congestion can cause packet

loss. In a voice conversation, gaps in the conversation represent packet losses. Some

packet loss, less than 5%, can be acceptable without audible degradation in voice

quality. Sporadic loss of small packets can be more acceptable than less frequent

loss of large packets.

Packet delay

Packet delay is the time between when a packet leaves and when a packet arrives at

it’s destination. The total packet delay time includes fixed and variable delay.

Variable delay is the more manageable delay, while fixed delay depends on the

network technology. The distinct network routing of packets are the cause of

variable delays. The gateway must be as close as possible to the network backbone

(WAN) with a minimum number of hops, to minimize packet delay and increase

voice quality.

Delay variation (jitter)

The amount of variation in packet delay is otherwise known as delay variations, or

jitter. Jitter affects the ability of the receiving gateway to assemble voice packets

received at irregular intervals into a continuous voice stream.

Fallback to circuit-switched voice facilities

If the measured Mean Opinion Score (MOS) for all codecs is below the configured

threshold for any monitored gateway, the Fallback to Conventional Circuit-

switched services activates. This feature reroutes calls to different trunks such as the

Public Switched Telephone Network (PSTN) until the network QoS improves.

When the QoS meets or exceeds the threshold, calls route over the IP network.

Disable the fallback feature in the Local Gateway Configuration. With the fallback

feature disabled, calls move across the IP telephony trunks no matter the QoS. The

fallback feature is only active at call setup. A call in progress does not fall back if

the QoS degrades.

Calls fallback if there is no response from the destination, an incorrectly configured

remote gateway table, or if there are not enough DSP resources available to handle

the new call.

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Avaya BCM 2.0 IP Telephony Instrukcja Użytkownika Strona 11