Introduction

The primary reason for implementing multicast in any network environment is to reduce bandwidth consumption when delivering shared advanced technology solutions. Multicast allows a single stream of packets to be distributed to a group of participants rather than creating a packet stream per member. Even though Internet Protocol (IP) multicasting has undergone significant changes, it is still a bit tricky to implement, even in wired local area networks (LANs). Getting it to work right in a wireless LAN (WLAN) environment is even more difficult. Some organizations disallow the use of multicast across their WLANs. Multicast requires a network infrastructure that supports protocols and features such as Protocol-Independent Multicast (PIM), Internet Group Management Protocol (IGMP), Cisco Group Management Protocol (CGMP), and IGMP snooping. Multicast is more complex in a wireless environment due to the half-duplex, shared, carrier sense, multiple access/collision avoidance (CSMA/CA) environment of WLANs. This chapter discusses the issues and configuration elements associated with implementing and optimizing IP multicasting in a WLAN.

There are a few things that must be considered for multicast solutions. If your organization needs to perform network-based video conferencing, real-time news feeds, radio broadcasts, or video on demand, you need to enable multicasting. If you are a home user, you may need multicasting for distance learning, Internet gaming, interactive chat sessions, and Internet jukeboxes. Why is multicasting needed in these situations? Multicasting is a method of sending packets to more than one receiver or interface at a time. The hosts receive the same information but...