 the pri- vately held company has raised >$420M in funding with >$110M from the capital markets and $310M in private equity funding Note that 60 paying customers at $12,000 a year only generate $0.7 million in annual revenue. 5. Streams such as DS1s are first bit- or byte-multiplexed into VTs. 6. Nortel Corporation, "SONET 101," White Paper, Document 56118.11, Ottawa, Canada. 7. In an asynchronous DS3 frame, the DS1s have gone through a number of levels of multiplexing that include the addition of stuffing and framing bits. The DS1 signals are mixed somewhere in the information bit fields and cannot be easily identified without completely demultiplexing the entire frame. 8. Clocking implies using a series of repetitive pulses to keep the bit rate of data constant and indicate where the ones and zeros are located in a data stream. 9. A comprehensive discussion of TMN was provided in D. Minoli et al., Planning and Managing Corporate ATM-Based Networks, Greenwich, CT: Prentice-Hall/Manning, 1997. 10. FOTS stands for fiber-optic transmission system. 11. SONET can be considered a subset of SDH. 12. CI is the arrangement of equipment and wiring on the customer premises (owned and maintained by the customer). 13. Nortel, "Introduction to SONET Networking-A Tutorial Handbook of Advanced SONET Networking Concepts," October 1996. 14. Nortel's S/DMS TransportNode enables up to 11 point-to-point systems to share a common protection channel (1:11 protection). 15. ATM's overhead: 5-byte tax for every 48 bytes of data sent. CHAPTER Next- Generation SONET and Optical Architectures Chapter 4 4.1 Motivations for Next- Generation Technology Although traditional Synchronous Optical Network (SONET) approaches to packet data transport can handle connectivity needs in some midspeed situations (for example, 10 to 100 Mbps), they generally do not adequately address the full requirements of emerging data-centric high-capacity net- works (for example, 1 to 10 Gbps). Such requirements can be better served by new technologies. Observers cont