Linksys SPA 900 SERIES Bandwidth Requirements1, Installing the SPA900 Series IP Phone, Codec

Chapter 2 Getting Started

Establishing Connectivity

•Installing the SPA900 Series IP Phone, page 2-10

Bandwidth Requirements1

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 IP phone 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 2-1illustrates the bandwidth budget using different codecs.

Table 2-1 Ethernet Bandwidth Budget for Off-Net VoIP Calling

Codec	Approximate bandwidth budget for	2 calls	4 calls	6 calls	8 calls
	each side of conversation
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

This table is based on the following assumptions:

•Bandwidth Calculated with No Silence Suppression

•20 Millisecond 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:

http://www.erlang.com/calculator/lipb/

http://www.packetizer.com/voip/diagnostics/bandcalc.html

Installing the SPA900 Series IP Phone

This section describes how to install and verify operation of SPA900 Series IP phones.

Check to make sure that you have the following package contents:

•Linksys 900 Series phone

•Ethernet cable

•Power adapter (must be ordered separately for PoE units: SPA922, SPA942, and SPA962)

	Linksys IP Phone Administrator Guide
2-10	Firmware Version 5.1