ScreenOS Cookbook

Chapter 20. Multicast

20.0. Introduction

IP Multicast is a fairly well-defined set of protocols that allows for more efficient distribution of a data stream to many receivers. Although the concept of IP Multicast is not new, the applications to date that have taken advantage of multicast delivery mechanisms are still not commonly deployed. There are a few technical reasons for this, but perhaps the primary factor that has delayed the large-scale deployment of multicast-based applications is the nature of the Internet itself. One of the primary benefits of IP-based communications is the asynchronicity the protocols afford. By taking advantage of the asynchronous nature of IP, many receivers can access the same information “at leisure.” This model has seen tremendous success with applications such as the Web, the File Transfer Protocol (FTP), and email, where information is relatively static. Because the benefit of IP Multicast is the ability to minimize network utilization by sending the same stream of traffic to multiple receivers, it follows that all of the listeners must receive the feed simultaneously. This obviously breaks the traditional asynchronous model of IP, and is a likely contributor to the limited deployment of IP Multicast.

Unfortunately, the Internet itself has seen limited multicast deployment at best, which stems largely from a lack of demand combined with the lack of an interdomain multicast routing protocol. Although the Multicast Source Discovery Protocol (MSDP) ...