Specifications

2-14

Linksys ATA Administrator Guide

Document Version 3.1

Chapter 2 Getting Started

Establishing Connectivity

This section describes how to connect the Linksys ATA hardware. It includes the following topics:

• Bandwidth Requirements, page 2-14

• Making the Physical Connections, page 2-15

Bandwidth Requirements

Depending on how you have your IP phones configured, each call requires 55 to 110 kbps in each

direction. Therefore, using G.729 as the voice codec setting, and with an average business-grade

broadband Internet connection supporting 1.5 Mbps downstream and 384 kbps upstream, a total of seven

(7) simultaneous conversations can be reliably supported with adequate bandwidth available for file

downloads.

Linksys recommends using the Linksys ATA with QoS-capable networking equipment that can

prioritize the VoIP application traffic. QoS features are available on many Linksys data networking

switches and routers. A QoS-enabled router prioritizes the packets going upstream to the ISP. Table 1-24

illustrates the bandwidth budget using different codecs.

This table is based on the following assumptions:

• Bandwidth Calculated with No Silence Suppression

• 20 milliseconds of payload per RTP packet

Note The use of silence suppression can reduce the average bandwidth budget by 30% or more.

For more information about bandwidth calculation, refer to the following websites:

Ethernet 1-3 Connect to local IP devices, such as PCs, using an Ethernet cable.

Power Connect to the power supply.

Table 1-23 WRTP54G Back Panel

Port Function

Table 1-24 Ethernet Bandwidth Budget for Off-Net VoIP Calling

Codec

Approximate bandwidth budget for each

side of conversation 2 calls 4 calls 6 calls 8 calls

G.711 110 kbps 220 kbps 440 kbps 660 kbps 880 kbps

G.726-40 87 kbps 174 kbps 348 kbps 522 kbps 696 kbps

G.726-32 79 kbps 158 kbps 316 kbps 474 kbps 632 kbps

G.726-24 71 kbps 142 kbps 284 kbps 426 kbps 568 kbps

G.726-16 63 kbps 126 kbps 252 kbps 378 kbps 504 kbps

G.729 55 kbps 110 kbps 220 kbps 330 kbps 440 kbps