Medianet Reference Guide - Cisco

Challenges of Medianets
Chapter 1
Medianet Architecture Overview
In these simplistic examples, you can see why it is important to understand how different media
applications behave in order to understand how they are likely to impact your network. Start by making
a table with (at least) the above questions in mind and inventory the various media applications in use
today, as well as those being considered for future deployments. Common requirements will emerge,
such as the need to meet “tight” service levels, the need to optimize bandwidth, and the need to optimize
broadcasts, which will be helpful in determining media application class groupings (discussed in more
detail later).
Delivery of Media Applications
A critical challenge the converged IP network needs to address is delivery of media application traffic,
in a reliable manner, while achieving the service levels required by each application. Media applications
inherently consume significant amounts of network resources, including bandwidth. A common
tendency is to add network bandwidth to existing IP networks and declare them ready for media
applications; however, bandwidth is just one factor in delivering media applications.
Media applications, especially those which are real-time or interactive, require reliable networks with
maximum up-time. For instance, consider the loss sensitivities of VoIP compared to high-definition
media applications, such as HD video. For a voice call, a packet loss percentage of even 1% can be
effectively concealed by VoIP codecs; whereas, the loss of two consecutive VoIP packets will cause an
audible “click” or “pop” to be heard by the receiver. In stark contrast, however, video-oriented media
applications generally have a much greater sensitivity to packet loss, especially HD video applications,
as these utilize highly-efficient compression techniques, such as H.264. As a result, a tremendous
amount of visual information is represented by a relatively few packets, which if lost, immediately
become visually apparent in the form of screen pixelization. With such HD media applications, such as
Cisco TelePresence, the loss of even one packet in 10,000 can be noticed by the end user. This represents
a hundred-fold increase in loss sensitivity when VoIP is compared to HD video.
Therefore, for each media application, it is important to understand the delivery tolerances required in
order to deliver a high-quality experience to the end user.
Prioritizing the Right Media Applications, Managing the Rest
With the first stage of IP convergence, the Cisco Architecture for Voice, Video, and Integrated Data
(AVVID) provided the foundation for different applications to effectively and transparently share the
same IP network. One of the challenges to overcome with converged networks is to be able to
simultaneously meet different application requirements, prioritizing network resources accordingly.
Quality of Service (QoS) continues to be a critical set of functions relied upon in the network to provide
differentiated service levels, assuring the highest priority applications can meet their delivery
requirements.
The AVVID model defined best practices for adding Voice-over-IP (VoIP) and Video over IP
applications to the existing data IP network. Most QoS implementations assume a number of data
applications, a single or few VoIP applications, and a single or few video applications.
Today there is a virtual explosion of media applications on the IP network with many different
combinations of audio, video and data media. For example, VoIP streams can be standard IP telephony,
high-definition audio, internet VoIP, or others. Video streams can range from relatively low-definition
webcams to traditional video-over-IP room-to-room conferencing to or high-definition Cisco
TelePresence systems. Additionally, there are new IP convergence opportunities occurring which further
expand the number of media applications and streams on the IP network (see Figure 1-3).
1-8
Medianet Reference Guide
OL-22201-01