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Chapter Goals
• Explain IP multicast addressing.
• Learn the basics of Internet Group Management Protocol (IGMP).
• Explain how multicast in Layer 2 switching works.
• Define multicast distribution trees.
• Learn how multicast forwarding works.
• Explain the basics of protocol-independent multicast (PIM).
• Define multiprotocol BGP.
• Learn how Multicast Source Discovery Protocol (MSDP) works.
• Explain reliable multicast: PGM.
Internet Protocol Multicast
Background
Internet Protocol (IP) multicast is a bandwidth-conserving technology that reduces traffic by
simultaneously delivering a single stream of information to thousands of corporate recipients and homes.
Applications that take advantage of multicast include videoconferencing, corporate communications,
distance learning, and distribution of software, stock quotes, and news.
IP Multicast delivers source traffic to multiple receivers without adding any additional burden on the
source or the receivers while using the least network bandwidth of any competing technology. Multicast
packets are replicated in the network by Cisco routers enabled with Protocol Independent Multicast
(PIM) and other supporting multicast protocols resulting in the most efficient delivery of data to multiple
receivers possible. All alternatives require the source to send more than one copy of the data. Some even
require the source to send an individual copy to each receiver. If there are thousands of receivers, even
low-bandwidth applications benefit from using Cisco IP Multicast. High-bandwidth applications, such
as MPEG video, may require a large portion of the available network bandwidth for a single stream. In
these applications, the only way to send to more than one receiver simultaneously is by using IP
Multicast. Figure 43-1 demonstrates how data from one source is delivered to several interested
recipients using IP multicast.
43-1
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Chapter 43
Internet Protocol Multicast
Multicast Group Concept
Fig