Specifications

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Catalyst 4224 Access Gateway Switch Software Configuration Guide
OL-2031-02
Chapter 6 Configuring VoIP
Configure IP Networks for Real-Time Voice Traffic
Enable RTP Header Compression on a Serial Interface
You need to enable compression on both ends of a serial connection. To enable
RTP header compression, use the following interface configuration command:
c4224(config-if)# ip rtp header-compression [passive]
If you include the passive keyword, the software compresses outgoing RTP
packets only if incoming RTP packets on the same interface are compressed. If
you use the command without the passive keyword, the software compresses all
RTP traffic.
Change the Number of Header Compression Connections
By default, the software supports a total of 16 RTP header compression
connections on an interface. To specify a different number of RTP header
compression connections, use the following interface configuration command:
c4224(config-if)# ip rtp compression connections number
RTP Header Compression Configuration Example
The following example enables RTP header compression for a serial interface:
c4224(config)# interface serial0
c4224(config-if)# ip rtp header-compression
c4224(config-if)# encapsulation ppp
c4224(config-if)# ip rtp compression-connections 25
For more information about RTP header compression, see the “Configuring IP
Multicast Routing” section of the Network Protocols Configuration Guide, Part 1
for Cisco IOS Release 12.0 T.
Configure Custom Queuing
Some QoS features, such as IP RTP reserve and custom queuing, are based on the
transport protocol and the associated port number. Real-time voice traffic is
carried on UDP ports ranging from 16384 to 16624. This range is derived from
the following formula:
16384 + (4 x number of voice ports in the c4224)