Linksys SPA922 Cisco Small Business IP Phone SPA9X1 Administration Guide - Page 33
Bandwidth Requirements1, Installing the SPA900 Series IP Phone, Codec
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Establishing Connectivity • Installing the SPA900 Series IP Phone, page 2-10 Chapter 2 Getting Started 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 2-1 illustrates the bandwidth budget using different codecs. Table 2-1 Ethernet Bandwidth Budget for Off-Net VoIP Calling Codec G.711 G.726-40 G.726-32 G.726-24 G.726-16 G.729 Approximate bandwidth budget for each side of conversation 110 kbps 87 kbps 79 kbps 71 kbps 63 kbps 55 kbps 2 calls 220 kbps 174 kbps 158 kbps 142 kbps 126 kbps 110 kbps 4 calls 440 kbps 348 kbps 316 kbps 284 kbps 252 kbps 220 kbps 6 calls 660 kbps 522 kbps 474 kbps 426 kbps 378 kbps 330 kbps 8 calls 880 kbps 696 kbps 632 kbps 568 kbps 504 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) 2-10 Linksys IP Phone Administrator Guide Firmware Version 5.1