Configure IP Networks for Real-Time Voice Traffic

For more information about Multilink PPP, refer to the “Configuring Media-Independent PPP and Multilink PPP” chapter in the 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

pppmultilink 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 4.

This compression feature is beneficial if you are running Voice over IP over slow links. Enabling compression on both ends of a low-bandwidth serial link can greatly reduce the network overhead if there is a lot of RTP traffic on that slow link.

Typically, an RTP packet has a payload of approximately 20 to 160 bytes for audio applications that use compressed payloads. RTP header compression is especially beneficial when the RTP payload size is small (for example, compressed audio payloads between 20 and 50 bytes).

Figure 4 RTP Header Compression

Before RTP header compression:

 

 

 

 

20 bytes

8 bytes 12 bytes

 

 

 

 

 

 

 

 

 

 

 

 

 

 

IP

UDP

RTP

 

 

 

Payload

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Header

 

 

 

20 to 160 bytes

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

After RTP header compression:

 

2 to 4 bytes

 

 

 

 

 

Payload

IP/UDP/RTP header

 

 

 

 

 

 

 

 

 

 

 

20 to 160 bytes

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

12076

VC-20Voice, Video, and Home Applications Configuration Guide

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Cisco Systems 3600 manual Configure RTP Header Compression, Multilink PPP Configuration Example

3600 specifications

Cisco Systems 3600 is a high-performance modular router series designed for small to medium-sized enterprises and branch offices. Launched in the late 1990s, it has been widely recognized for its flexibility, scalability, and reliability. The series is part of Cisco's extensive networking portfolio and has played a vital role in delivering various services and applications while enhancing operational efficiency.

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The Cisco 3600 series routers utilize advanced routing protocols, such as RIP, OSPF, EIGRP, BGP, and IS-IS, to ensure efficient data transmission and optimal network performance. This capability allows the routers to adapt to varying traffic demands and complexities, thereby optimizing bandwidth utilization and reducing latency in communications. With extensive memory options, including Flash and DRAM, the 3600 series can handle robust data processing and support intricate routing environments.

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In terms of scalability, Cisco 3600 routers can easily accommodate increased workloads and network growth. This is done through the provision of additional modules and cards to increase capacity and performance. The series can also support multiple WAN connections, enabling seamless integration with various telecommunication services.

Additionally, the Cisco 3600 series is designed for ease of management. Utilizing Cisco's IOS software, network administrators can manage and configure the routers efficiently, thanks to a user-friendly interface and extensive command capabilities. This makes troubleshooting simpler and ensures network availability remains high.

In conclusion, Cisco Systems 3600 series routers combine robust performance, security features, and scalability, making them an invaluable asset for businesses looking to maintain a reliable and efficient networking solution.