Avaya BCM 2.0 IP Telephony Manual de usuario descargar pdf (Pagina 43)

Engineering guidelines 43

P0911590 Issue 02 Enterprise Edge 2.0 IP Telephony Configuration Guide

Set the Tx and Rx thresholds (MOS numbers) for the remote gateway with the

required QoS level as indicated in the Modifying the Remote Gateway

Configuration table on page 66.

The fallback threshold algorithm considers a fixed IP telephony delay of 140 ms.

This delay is based on the default settings and its delay monitoring probe packets.

The fallback mechanism does not adjust when the parameters are modified from

their default values. Users can sense a lower quality of service than the QoS levels

at fallback thresholds when:

• Delay variation in the intranet is important. If the standard deviation of one-way

delay is like the jitter buffer maximum delay, it means that there is a group of

packets that arrive late to be used by the gateway in the playout process.

• The jitter buffer is increased. The real one-way delay is greater than that

estimated by the delay probe.

• The codec is G.711. The voice packets formed by this codec are larger (120 to

280 bytes) than the delay probe packets (60 bytes). This means there is a greater

delay felt per hop. If there are low bandwidth links in the path, then the one-way

delay is higher both in terms of average and variation.

Dialing plan

The dialing plan determines the digits used to make and receive calls over the IP

telephony. Because all the gateways attached to the intranet must work together, the

installer and administrator ensures the control of the configuration of all gateways,

including the dialing plan and codec selections. A local gateway at one location is

a remote gateway from another location and reversed.

IP telephony supports wildcards through the best match algorithm. All calls which

do not have a specific match in the Modifying the Remote Gateway Configuration

table on page 66 route through the generic IP address.

IP telephony and M1 networking

This example shows a private network made of one central Meridian 1, and two

smaller sites with Enterprise Edge systems connected over IP trunks through a

corporate IP network. This example can represent a large head office (with the

Meridian 1) connected to several smaller branch offices.

In this network, only the head office has trunks connected to the public network.

The branch offices access the public network using IP trunks to the head office. This

configuration allows to save costs and to join together public access trunks. Users

at all three locations access the public network by dialing ‘9’, followed by the public

number. For example, a user in the west end branch can dial 9-555-1212 (for a local

call) or 9-1-613-555-1212 (for a long distance call). These public calls routes to the

Meridian 1 by the Enterprise Edge’s routing table. Routing tables at the Meridian 1

select an appropriate public facility for the call.

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Avaya BCM 2.0 IP Telephony Manual de usuario Pagina 43