Cisco Systems H.323/SIP manual Audio Quality During a Cisco Unified MeetingPlace Meeting

Chapter 1 Introducing Cisco Unified MeetingPlace H.323/SIP IP Gateway Software Release 5.2.1

Information About Cisco Unified MeetingPlace H.323/SIP IP Gateway Software Release 5.2.1 Components

H.323 clients can use out-of-band DTMF, which carries digitized information on a separate data channel and sends this information directly to Release 5.2.1. Because out-of-band DTMF does not require that the tone be deciphered, distortion and signal loss are minimal.

The Cisco Unified MeetingPlace system also supports RFC 2833: DTMF signals can be sent in the RTP stream by using packets designed to carry the signal characteristics. The DTMF signal is not embedded in the media and, therefore, does not suffer signal loss due to audio compression.

Release 5.2.1 handles both in-band and out-of-band DTMF.

Note Release 5.2.1 does not support out-of-band digit detection with SIP.

Audio Quality During a Cisco Unified MeetingPlace Meeting

The audio quality during a meeting depends upon the architecture of your network. Severe demands on bandwidth, overloading, and latency cause dropped packets, resulting in broken audio, congestion, and disruption of service.

In general, a switched-100 Mbps network handles VoIP traffic efficiently. To alleviate potentially disruptive service and to improve audio quality, consider implementing class of service (CoS) and quality of service (QoS).

When the server handles over 400 ports of IP calls, voice quality degradation can occur because of network congestion. CoS is a technology that helps manage network traffic by assigning a class to similar types of traffic and assigning a priority to each class. Typically in a VoIP environment, voice traffic is set to a high priority while data traffic is set to a low priority, and CoS makes a best effort to provide QoS by managing traffic based upon the assigned class and priority.

Release 5.2.1 implements IP Precedence Level 5 CoS for voice traffic. If your network is set to use this CoS, the resulting QoS maximizes audio quality during your meetings.

Note Release 5.2.1 does not support sending Layer 2 QoS or CoS; therefore, you cannot set priorities at the Layer 2 switch level.

Endpoints That are Supported by Cisco Unified MeetingPlace H.323/SIP IP Gateway Software Release 5.2.1

Release 5.2.1 integrates easily with existing networks to host Cisco Unified MeetingPlace meetings for users through the following supported endpoints:

•Cisco IP Phones

•Cisco SIP IP Phones

•H.323 clients, such as Microsoft NetMeeting

•PSTN phones through a voice gateway

Administrator Guide for Cisco Unified MeetingPlace H.323/SIP IP Gateway Software Release 5.2.1

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