ADTRAN Stub Routing - Manual (Page 2)

IP Multicast Overview IP Multicast Stub Routing in AOS
2 Copyright © 2005 ADTRAN, Inc. 61200890L1-29.3A
IP Multicast Overview
IP multicast has many applications, ranging from video and/or audio program delivery, music-on-hold for
an IP PBX, conferencing applications, and delivery of software updates, data, or other information to
multiple sites and/or devices. This document uses simple example applications to illustrate the various
components of IP multicast.
Satellite Classroom Example
The following example describes a one-to-many application and compares operation in a non-multicast
network to operation in a multicast network. This example is illustrated in Figure 1 on page 3.
A university has opened satellite classrooms in several towns across a large rural portion of the country,
providing local residents access to live classes. Satellite offices connect to the university backbone and
include a small LAN at each location. Students participate in classes using computers connected to the
satellite classroom LAN. Headsets are used since each student may be attending a different class. Classes
are conducted at scheduled times from the central university campus, and the live audio and video streams
are made available via the media server. To join a class, the student logs into a computer at the satellite
classroom and selects a URL, opening a media player and pointing it to the appropriate content on the
media server. The media server configures the media player for the content's stream format (CODECs,
etc.), preparing it to receive and play the selected content.
Satellite Classroom Application on a Non-Multicast Network
Referring to Figure 1 on page 3, PC1 , PC2 , PC4 , and PC6 have subscribed to the same classroom
broadcast. Since the network is not multicast-enabled, the Media Server must send a separate copy of the
content to the IP address of each PC. In this case, there are four copies of the content traversing the
network in four streams. The link from the
Media Server to the University Backbone is a potential
bottleneck. In this backbone layout, the backbone path serving satellite sites 1 and 2 ( Satellite
Router 1/Satellite Router 2 ) is another potential bottleneck. Notice that PC1 and PC2 are on the same
broadcast domain. Even though they are subscribed to the exact same content, that stream is transmitted
twice and consumes twice the bandwidth on that segment. This solution does not scale.