Cisco WS-X4604-GWY - VoIP Gateway Especificaciones descargar pdf (Pagina 175)

CHAPTER

8-1

Cisco IP Telephony Network Design Guide

78-11103-03

Quality of Service

This chapter addresses the Quality of Service (QoS) requirements for

implementations of IP telephone solutions over an enterprise network. By

applying the prerequisite tools, you can achieve excellent quality voice, video,

and data transmissions over an IP infrastructure, irrespective of media and even at

low data rates.

For more detailed information on designing Quality of Service

networks for AVVID deployments, please see

the Cisco AVVID QoS Design

Guide at

http://www.cisco.com/univercd/cc/td/doc/product/voice/ip_tele/index.htm

This chapter includes the following major sections:

• Campus QoS Model, page 8-1

• WAN QoS Model, page 8-4

Campus QoS Model

Until recently, conventional wisdom stated that Quality of Service would never be

an issue in the enterprise campus due to the bursty nature of data traffic and the

capability to withstand buffer overflow and packet loss. When applications such

as voice and video, which are sensitive to loss and delay, began to traverse the data

network, network designers gradually came to understand that buffers and not

bandwidth are the issue in the campus. Buffers can fill instantaneously. When this

occurs, packets can be dropped when attempting to enter the interface buffer. For

applications like voice, which are extremely drop intolerant, this results in voice

quality degradation. QoS tools are required to manage these buffers to minimize

loss, delay, and delay variation.

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Cisco WS-X4604-GWY - VoIP Gateway Especificaciones Pagina 175