alized MPLS and Their Application to Optical Networks, with Reference to the Link Management Protocol and Optical UNI," Data Connection Ltd. White Paper, Version 2, www.dataconnection.com, October 2001. DCL is the leading independent developer and supplier of MPLS, ATM, SS7, MGCP/MEGACO, SSCTP, VoIP conferencing, messaging, directory, and SNA portable products. DCL's customers include Alcatel, Cabletron, Cisco, Fujitsu, Hewlett-Packard, Hitachi, IBM Corp., Microsoft, Nortel, SGI, and Sun. DCL is headquartered in London and has U.S. offices in Reston, Virginia, and Alameda, California. It was founded in 1981 and is privately held. In 1999, the company received its second Queen's Award for outstanding export performance. 3. "Link Management Protocol (LMP)," draft-ietf-ccamp-Imp, November 2001. 4. "Fault Tolerance for LDP and CR-LDP," draft-ietf-mpls-ldp-ft, October 2000. 5. RFC 2961, "RSVP Refresh Overhead Reduction Extensions," April 2001. 6. Data Connection Ltd., "Surviving Failures in MPLS Networks-An Examination of the Methods for Protecting MPLS LSPs Against Failures of Network Resources," White Paper, www.dataconnection.com, October 2001. This page intentionally left blank. CHAPTER Free-Space Optics (FSO) Chapter 9 Using free-space optics (FSO) to bridge the last mile and first mile between a local area network (LAN), metropolitan area network (MAN), and wide area network (WAN) in a wireless environment has been seriously pro- pounded as the solution for MANs. Considering the cost of connecting build- ings to core optical networks running in the street below or a block or two away (typically in the range of $75,000 to $200,000 and at times more), FSO is an attractive contender. However, like all radio solutions proposed for this purpose in the past 25 years, starting with Xerox's original mid-1970s pro- posal, it appears to have limited or transient application. This chapter addresses the advantages and disadvantages of FSO and the challenges that FSO faces based on technical, financial, and implementation as