Illustrated TCP/IP by Matthew G. Naugle Wiley Computer Publishing, John Wiley & Sons, Inc. ISBN: 0471196568   Pub Date: 11/01/98

Part Five
IP Multicast

Chapter 247
Introduction

With addressing, as I have mentioned before, there are three types with IPv4: point-to-point (unicast), point-to-multipoint (multicast), and point-to-all-multipoints (broadcast). But multicast as it pertains to IP is much more than a simple address; it’s what enables IP to deliver multimedia over a packet switched network with very little bandwidth consumption (relative to pushing the data to the same recipients using unicast).

You will often hear the pseudo-technical term push or pull technology. This means you have to go and get the information off the Internet (pull), or the information comes to you (push). There is a vast array of information in the Internet and finding it can be a daunting task. Push technology means that information is sent to you. An example of this can be an information news service that retrieves information on certain subjects throughout the day. A lot of readers have probably heard of PointCast. This is an example of a pseudo-push technology that will eventually be a full-blown push technology. Whenever information changes on that news server, stories related to your requests are pushed down to your workstation, saving you the trouble of finding and downloading the information.

Another exciting evolution is the ability to have voice and video run over an IP network. I know, it can be accomplished today, but I am not fond of viewing a 2" × 2" fuzzy screen that has incredible delay and non-lip sync audio. It is like watching an old Japanese movie that has been converted to English. Frame reception at 5 fps is not great. It is fun to experiment, but until it appears like CATV (cable TV), users will not consider it as a serious requirement for the LAN infrastructure.

Introduction

Another advancement on the Internet is voice and video over IP. Replicating a separate stream of data for every user request to a single video source would easily overload the Internet. The ability to transmit one packet and have it replicated at certain points along the many paths to separate destinations is a much more efficient system of distributing data, voice, and video. Multicasting allows this as well.