In this chapter, you've explored how to implement multiple-site structures. Various factors mitigating your choice of site hierarchy have been introduced and discussed. We have also examined the concept of parent-child relationships in SMS 2.0 and you've learned how to establish that relationship through addresses and senders. You've also learned how to install a secondary site and the site configuration process involved. Last we looked at defining and implementing SMS senders and traced the sending process. Chapters 5 and 6 will introduce several diagnostic tools that will become invaluable to you as you maintain and troubleshoot your site.