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.

Communication services that support voice, video, and data are provided by a variety of carriers and service providers: "last-mile" local access services, metropolitan area services, or wide area services. The types of providers that sell these services include the following:

• ILECs (incumbent local exchange carriers)    The traditional telephone carriers that are usually the RBOCs (Regional Bell Operating Companies), although some areas have carriers that were never part of AT&T.


• CLECs (competitive local exchange carriers)    Carriers that compete with the ILECs within the same geographic area.


• IXCs (interexchange carriers)    These are the traditional long-distance carriers such as MCI Worldcom, Sprint, and AT&T, as well as new players.


• ICPs (integrated communications providers)    CLECs are morphing into ICPs, which provide a variety of "NPN (New Public Network)" services, including Web hosting and Internet access.


• Integrated voice-video-data service providers    Service providers that have built infrastructure in local, metropolitan, or wide areas to provide a full range of voice, video, and data services.


• CATV    The traditional television cable networks, now providing voice, video, and high-speed data services over hybrid copper/fiber networks.


• ISPs (Internet service providers)    Traditional Internet service providers, some of which may offer local access in the form of fiber cables into buildings or wireless access systems.


• WSPs (wireless service providers)    A whole new breed of service providers that use radio or optical wireless systems to provide local access to homes and businesses. In addition, cellular phone system providers are boosting their data rates with new protocols and technologies.


• HALO (High Altitude Long Operation)    These are the newest local access providers that offer wireless services relayed from balloons or circling planes.


• Satellite systems    There are a number of satellite systems in place to deliver voice, video, and data services, including the LEO (low earth orbit) and geosynchronous systems.

Organizations build wide area enterprise networks to link remote users and create LAN-to-LAN links that allow users in one geographic area to use resources on LANs in other areas. A variety of carrier services are available to create these links:

• Circuit switching (analog)    Provides dial-up lines with relatively low throughput for point-to-point connections. This type of service is best for occasional traffic between two points, such as a single-user connection or file transfer.


• Circuit switching (digital)    Provides temporary connections between two points with rapid setup times. This type of service is preferred for periodic connections among a number of different points where speeds higher than dial-up lines is required. Circuits are usually virtual.


• Dedicated line    Provides a permanent connection between two points on a leased, month-to-month basis, usually with an initial setup charge. These lines are suitable for handling constant traffic between two sites.


• Packet switching    Provides the most flexible service for companies that need to connect with many different sites. A packet-switched network provides simultaneous connections to many points and bandwidth on demand in most cases. See "Packets and Packet-Switching Networks" for more information.

The following describes services available from the local and long-distance carriers. For additional information about the services provided by specific providers, refer to their Web sites. The Web sites listed on the related entries page provide links to carriers and service providers. Also see "Service Providers and Carriers." Many of these services can be defined as either access services for enterprise wide area networking and/or Internet access services for home and small business users. Refer to either "WAN (Wide Area Network)" or "Network Access Services."

• Dial-up analog lines    Connections are made only when needed for file transfers, e-mail connections, and remote users' sessions. See "Modems."


• Permanent leased lines    These analog lines provide the same data rates as dial-up lines, except that customers contract with the carrier to keep the lines available for immediate use when necessary. See "Leased Line," "T Carriers," and "TDM Networks."


• Circuit switched ISDN (Integrated Services Digital Network)    ISDN is a point-to-point voice and data service with two switchable channels that provide a data rate of 64 Kbits/sec. See "ISDN (Integrated Services Digital Network)" for more details.


• Dedicated digital TDM (time division multiplexing) services    With TDM, data is transmitted across circuits that are divided into time slots, with individual users getting a regular repeating time slot. The traditional TDM digital line service is the T1 channel. See "T Carriers" and "TDM Networks."


• DSL (Digital Subscriber Line) services    These are emerging services that use the existing twisted-pair copper wire in the local loop to provide data rates up to the megabits-per- second range. DSL is an always-on circuit service for home and business use.


• Cable (CATV)    Existing CATV network providers are now offering Internet connection services over their networks, primarily to home users. See "Cable (CATV) Data Networks."


• X.25 packet switching services    This is a standard, well-tested, protocol that has been a workhorse packet-switching service since 1976. It is suitable for light loads and was commonly used to provide remote terminal connections to mainframe systems. However, frame relay and ATM services are more suitable for network traffic.


• Frame relay frame switching services    This service provides many enhancements over X.25. It is an excellent choice for organizations that need any-to-any connections on an as-needed or permanent basis. See "Frame Relay" for more details.


• ATM (Asynchronous Transfer Mode)    This service provides cell-switching services that can transmit data at megabit- and potentially gigabit-per-second rates. Most carriers already use ATM switching internally. Customers can take advantage of this service by installing ATM access devices on-site to route voice, video, and data across the carriers network. See "ATM (Asynchronous Transfer Mode)."


• Metro Ethernet and Ethernet WAN services    Gigabit Ethernet and 10 Gigabit Ethernet are proving useful in the MAN (metropolitan area network) and WAN environments. A number of service providers are building mesh networks with these technologies and separating customer traffic with VLAN techniques. See "MAN (Metropolitan Area Network)," "Network Access Services," and "WAN (Wide Area Network)."


• Wireless mobile services    The cellular phone service providers are extending their existing networks and frequency allocation rights with new protocols and technology that boost the data rates for which mobile users. Refer to "Wireless Mobile Communications" for more information.


• Wireless broadband    A whole range of new high-speed wireless services is emerging that can provide access services in the gigabit-per-second range. See "Wireless Broadband Access Technologies" for more details.

Copyright (c) 2001 Tom Sheldon and Big Sur Multimedia.
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