Note: Many topics at this site are reduced versions of the text in "The Encyclopedia of Networking and Telecommunications." Search results will not be as extensive as a search of the book's CD-ROM.

Metropolitan area networks connect businesses to businesses, and businesses to WANs and the Internet. A MAN is typically a backbone optical network that spans a metropolitan area, usually in a ring configuration. The telephone companies have provided MAN services in the form of SONET rings for years. These services are based on TDM (time division multiplexing), which is more suitable for voice than data. Customers connect into the ring via ISDN, T1, fractional T1, and even T3 lines. However, even for short distances, these connections are expensive.

A new era of computer networking is emerging with new MAN technologies that extend Ethernet LAN networks across the MAN via fiber-optic links. Most important, these services are being offered by carriers that compete with the incumbent phone companies, and they are cheap. An organization can obtain a 10-Mbit/sec link between its offices in a metropolitan area for under $400 per month. A 100-Mbit/sec link may cost under $1,000 per month. The new networks are also extremely flexible. In some cases, customers can access the provider's Web site and fill out a form to obtain an immediate service upgrade for a special event such as a videoconference.

This topic continues in "The Encyclopedia of Networking and Telecommunications" with a discussion of the following:

• Gigabit Ethernet MANs
• Wireless optical MANs
• SONET comparison
• Resilient packet rings
• WirelessHUMAN (Wireless High-Speed Unlicensed Metropolitan Area Networks)
• DPT (Dynamic Packet Transport)

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