le II.4, IXth Plenary Assembly, Melbourne, 1988. 7. Functional Criteria for Digital Loop Carrier Systems, Bellcore Technical Reference TR-NWT- 000057, Issue 2, Bellcore, Piscataway, NJ, 1993. 8. J. C. McDonald, ed., Fundamentals of Digital Switching, 2nd ed., Plenum Press, New York, 1990. 9. Digital Network Synchronization Plan, Bellcore Generic Requirements, GR-435-CORE, Bell- core, Piscataway, NJ, 1994. 10. Timing Requirements at the Outputs of Reference Clocks and Network Nodes Suitable for Ple- siochronous Operation of International Digital Links, CCITT Rec. G.811, Fascicle III.5, IXth Plenary Assembly, Melbourne, 1988. 11. Transport Systems Generic Requirements (TSGR): Common Requirements, Bellcore GR-499- CORE, Issue 1, Bellcore, Piscataway, NJ, Dec. 1995. 12. Error Performance of an International Digital Connection Forming Part of an ISDN, CCITT Rec. G.821, Fascicle III.5, IXth Plenary Assembly, Melbourne, 1988. 13. BOC Notes on the LEC Networks-1994, Special Report SR-TSV-002275, Issue 2, Bellcore, Piscataway, NJ, 1994. 14. Controlled Slip Rate Objectives on an International Digital Connection, CCITT Rec. G.822, Fascicle III.5, IXth Plenary Assembly, Melbourne, 1988. 15. R. L. Freeman, Telecommunication Transmission Handbook, 4th ed., Wiley, New York, 1988. 16. Physical/Electrical Characteristics of Hierarchical Digital Interfaces, CCITT Rec. G.703, ITU Geneva, 1991. 17. J. C. McDonald, ed., Fundamentals of Digital Switching, 2nd ed., Plenum Press, New York, 1990. SIGNALING 7.1 WHAT IS THE PURPOSE OF SIGNALING? The IEEE (Ref. 1) defines signaling as the exchange of information specifically concerned with the establishment and control of connections and the transfer of user-to-user and management information in a telecommunication network. Conventional signaling has evolved with the telephone network. Many of the tech- niques we deal with in this chapter are applicable to a telecommunication network that is principally involved with telephone calls. With telephony, signaling is broken down in three functio