Cisco Systems H.323/SIP Manual De Usuario

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. 

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

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.

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

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