Specifications
Configure RTP Header Compression
Voice over IP for the Cisco AS5300 9
Note Multilink PPP should not be used on links greater than 2 Mbps.
Multilink PPP support for interleaving can be configured on virtual templates, dialer interfaces, and
ISDN BRI or PRI interfaces. To configure interleaving, you need to perform the following tasks:
• Configure the dialer interface or virtual template, as defined in the relevant chapters of the
Cisco IOS Release 12.0 Dial Solutions Configuration Guide.
• Configure Multilink PPP and interleaving on the interface or template.
Enable Multilink PPP and Interleaving
To configure Multilink PPP and interleaving on a configured and operational interface or virtual
interface template, use the following commands in interface configuration mode:
Note The ip rtp reserve command can be used instead of configuring RSVP. If you configure
RSVP, this command is not required.
For more information about Multilink PPP, refer to the the Cisco IOS Release 12.0 Dial Solutions
Configuration Guide.
Multilink PPP Configuration Example
The following example defines a virtual interface template that enables Multilink PPP with
interleaving and a maximum real-time traffic delay of 20 milliseconds, and then applies that virtual
template to the Multilink PPP bundle:
interface virtual-template 1
ppp multilink
encapsulated ppp
ppp multilink interleave
ppp multilink fragment-delay 20
ip rtp reserve 16384 100 64
multilink virtual-template 1
Configure RTP Header Compression
Real-Time Transport Protocol (RTP) is used for carrying packetized audio traffic over an IP network.
RTP header compression compresses the IP/UDP/RTP header in an RTP data packet from 40 bytes
to approximately 2 to 4 bytes (most of the time), as shown in Figure 3.
Step Command Purpose
1 ppp multilink Enables Multilink PPP.
2 ppp multilink interleave Enables real-time packet interleaving.
3 ppp multilink fragment-delay milliseconds Optionally, configures a maximum fragment delay.
4 ip rtp reserve lowest-UDP-port range-of-ports
[maximum-bandwidth]
Reserves a special queue for real-time packet flows
to specified destination User Datagram Protocol
(UDP) ports, allowing real-time traffic to have
higher priority than other flows. This command
applies only if you have not configured RSVP.