This chapter provides an overview of the 7210 SAS-D, 7210 SAS-Dxp, 7210 SAS-K 2F1C2T, 7210 SAS-K 2F6C4T, and 7210 SAS-K 3SFP+ 8C subscriber services, service model, and service entities. Additional information about the individual subscriber services supported on different 7210 SAS platforms and their configuration options is in subsequent chapters.