Cisco SPA962-EU Administration Guide - Page 37
Establishing Connectivity, Bandwidth Requirements
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Chapter 2 Getting Started Establishing Connectivity Establishing Connectivity This section describes how to connect the SPA900 Series IP phone hardware. It includes the following topics: • Bandwidth Requirements, page 2-9 • Installing the SPA900 Series IP Phone, page 2-10 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 900 Series 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 Approximate bandwidth budget for each side of conversation G.711 110 kbps G.726-40 87 kbps G.726-32 79 kbps G.726-24 71 kbps G.726-16 63 kbps G.729 55 kbps 2 calls 4 calls 6 calls 8 calls 220 kbps 440 kbps 660 kbps 880 kbps 174 kbps 348 kbps 522 kbps 696 kbps 158 kbps 316 kbps 474 kbps 632 kbps 142 kbps 284 kbps 426 kbps 568 kbps 126 kbps 252 kbps 378 kbps 504 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 Document Version 3.0 Linksys 900 Series IP Phone Administrator Guide 2-9