mized for? 3. Give at least five examples of digital services that can be transported on SONET. 4. Describe in words the basic SONET frame. Show its apparent payload and then its actual payload and explain the differences. REFERENCES 5. How can we calculate the bit rate of STS-3 if we know that the bit rate of STS-1 is 51.84 Mbps? Explain how STS-Nc concatenation operates and its purpose. 7. What are the two primary uses of the payload pointer? 8. What network impairment is introduced by the payload pointer? What is its cause? 9. What are the three overhead levels of SONET? 10. Name at least three specific functions of the POH. 11. What is payload mapping? 12. If the SONET line rate were OC-48, how could one calculate this bit rate? 13. What is the function of an add-drop multiplexer in the add-drop mode? 14. The SDH STM-1 bit rate equal what SONET line rate? 15. How do we derive higher line rates from the SDH STM-1? 16. What are the two types of pointers used in SDH? 17. When the frame rate of a VC-n is too slow with respect to that of the AUG, what happens to the alignment of the VC-n? What happens to the pointer value in this example? 18. We change the value of an AU pointer. How many frames must go by before changing it again? Why can't we change it right away, right on the next frame? 19. How many AU-3s or AU-4s may be contained in an AUG? SDH was designed to carry the E1 hierarchy. Can it also carry the DS1 hierarchy? REFERENCES 1. Synchronous Optical Network (SONET), Transport Systems, Common Generic Criteria, Bellcore, GR-253-CORE, Issue 1, Bellcore, Piscataway, NJ 1994. 2. Introduction to SONET, seminar, Hewlett-Packard Co., Burlington, MA, Nov. 1993. 3. Curtis A. Siller and Mansoor Shafi, eds., SONET/SDH, IEEE Press, New York, 1996. 4. SONET Add-Drop Multiplex Equipment (SONET ADM) Generic Criteria, Bellcore TR-TSY- 000496, Issue 2, Bellcore, Piscataway, NJ 1989. 5. Synchronous Digital Hierarchy Bit Rates, ITU-T Rec. G.707, ITU Helsinki, 1993. 6. Network Node Interface for the Synchronous Digital Hierar