CVOICE Chapter2 まとめ

■ Because of the nature of IP networking, voice packets sent via IP are subject to certain transmission problems.

■ Sevaral methods can be used to determine audio quality in a VoIP network.

■ QoS is used to help meet the strict requrements concerning packet loss, delay, and delay variation in a VoIP network.

■ Some challenges exist to transporting modulated data, including fax and modem calls, over IP networks.

■ Features to support fax and modem traffic include
　 ■ Fax and Modem Pass-Through
　 ■ Fax and Modem Relay
　 ■ Store-and-Forward Fax

■ T.38, pass-through, and relay use special protocol enhancements available in the H.323, SIP, and MGCP call signaling protocols.

■ DTMF support is provided by Cisco IOS gateways.

■ Codecs are used to compress and decompress various types of data that would otherwise use up large amounts of bandwidth.

■  Voice sample size is a variable that can affect the total bandwidth used.

■  Several factors must be included in calculating the overhead of a VoIP call.

■  Codec choice, data-link overhead, sample size, and compressed RTP have positive and negative impacts on total bandwidth.

■  Codec complexity affects the call density.

■  DSPs enalbe CCisco platforms to efficiently process digital voice traffic.

■  The number of DSPs required is a key factor when deploying media resources using DSPs.

■  The configuration of transcoding and conferencing on a voice gateway involves several componetnts.

■  DSP farm services are enabled on the voice card, and DSP profiles create the actual media resource.

■  You can verify DSP media resources using show dspfarm commands.