The CDN Model
Until now, we have only brie³y covered the major reasons for having a content delivery system and a few of the methods that could facilitate the operation of a content delivery network (CDN). In this chapter we will probe more deeply into the content delivery model, examining so-called edge operations that move the content of customers to the edges of the Internet. In actuality, the term edge, while appropriate, can mean di‘erent things to di‘erent persons with respect to their physical location. However, prior to discussing edge operations, we will ›rst build upon information previously presented in this book to obtain a better appreciation for the rationale for CDN. In doing so, we will view the Internet as a large transmission facility that has a series of critical links. Such a view will allow us to better understand bottlenecks and how a distributed content delivery network can overcome such bottlenecks. Because this author believes that both sides of a coin need to be shown, as we discuss edge operations we will also examine some of the limitations associated with the distribution of content across the Internet.