H - Definitions

  • H

    H.323

    H.323 is a standard approved by the International Telecommunication Union (ITU) in 1996 to promote compatibility in videoconference transmissions over IP networks.

  • half-duplex

    Half-duplex data transmission means that data can be transmitted in both directions on a signal carrier, but not at the same time.

  • handshaking

    In telephone communication, handshaking is the exchange of information between two modems and the resulting agreement about which protocol to use that precedes each telephone connection.

  • hardware

    In information technology, hardware is the physical aspect of computers, telecommunications, and other devices.

  • hardware load-balancing device (HLD)

    A hardware load-balancing device (HLD), also known as a layer 4-7 router, is a physical unit that directs computers to individual servers in a network, based on factors such as server processor utilization, the number of connections to a server, or the overall server performance.

  • hardware VPN

    A hardware VPN is a virtual private network ( VPN) based on a single, stand-alone device.

  • HDLC (High-level Data Link Control)

    HDLC (High-level Data Link Control) is a group of protocols or rules for transmitting data between network points (sometimes called nodes).

  • HDSL (High bit-rate Digital Subscriber Line)

    Also see our Fast guide to DSL. HDSL (High bit-rate Digital Subscriber Line), one of the earliest forms of DSL, is used for wideband digital transmission within a corporate site and between the telephone company and a customer.

  • HELLO packet

    In the Open Shortest Path First (OSPF) communications protocol - which enables network routers to share information with each other, a HELLO packet is a special packet (message) that is sent out periodically from a router to establish and confirm network adjacency relationships.

  • High-Speed Circuit-Switched Data (HSCSD)

    High-Speed Circuit-Switched Data (HSCSD) is circuit-switched wireless data transmission for mobile users at data rates up to 38.4 Kbps, four times faster than the standard data rates of the Global System for Mobile (GSM) communication standard in 1999. HSCSD is comparable to the speed of many computer modems that communicate with today's fixed telephone networks.

  • high-speed dialup

    High-speed dialup, sometimes advertised as broadband dialup, is an Internet service provider (ISP) feature that speeds up data transfer by using a special server, called an acceleration server, to act as a bridge between the user's dialup connection and a Web page.

  • High-Speed Serial Interface (HSSI)

    High-Speed Serial Interface (HSSI) is a short-distance communications interface that is commonly used to interconnect routing and switching devices on local area networks (LANs) with the higher-speed lines of a wide area network (WAN).

  • home address

    In the Mobile Internet Protocol (Mobile IP), a home address is the relatively permanent IP address given to a mobile node.

  • home agent

    In Mobile Internet Protocol (Mobile IP), a home agent is a router on a mobile node's home network that maintains information about the device's current location, as identified in its care-of address.

  • Home Location Register (HLR)

    The Home Location Register (HLR) is the main database of permanent subscriber information for a mobile network.

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