| ADSL |
ADSL (Asymmetric Digital Subscriber Line) is a modem technology that converts existing twisted-pair telephone lines into access paths for multimedia and high-speed data communications. ADSL is called asymmetric because most of its two-way or duplex bandwidth is devoted to sending data downstream, to the user. Only a small portion of bandwidth is available for upstream messages.
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| analog |
The principal feature of analog representations is that they are continuous. In contrast, digital representations are measured at discrete intervals.
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| ATM |
The Asynchronous Transfer Mode (ATM) protocol sends information segmented into fixed length cells of 53 bytes. Fixed cells allow the information to be transported in a predictable way, which accommodates different traffic types on the same network. ATM was designed to accommodate the simultaneous transmission of data, audio, and video.
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| bandwidth |
Bandwidth refers to the transmission capacity of an electronic communications line (e.g., a telephone line). Transmission rates are measured by how many bits of data can cross the wire per second. Slower transmission speeds are measured in kilobits per second (1,024 bits, abbreviated Kbps). Faster transmissions are measured in millions of bits, megabits, per second (Mbps) or billions of bits, gigabits, per second (GBps).
Note: For analog devices - as opposed to digital ones - bandwidth is expressed in cycles per second, or Hertz (Hz). |
| BlueTooth |
BlueTooth is a specification for the use of low-power radio communications to wirelessly link phones, computers, and other network devices over short distances. |
| bridge |
A bridge device filters data traffic at a network boundary. Bridges reduce the amount of traffic on a network by dividing it into two segments. |
| broadband |
Generally speaking, broadband is the capability of supporting, in both downstream (provider to consumer) and upstream (consumer to provider) directions, at a speed in excess of 200 Kbps per second.
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| cable modem |
A modem designed to operate over cable TV lines.
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| client-server |
The client-server model of computer communications features a client computer that calls a server computer to request a service (e.g., the download of a file). The client is the machine that initiates contact. The server is the machine that responds to the request.
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| computer virus |
A computer virus is a program that reproduces its own code by attaching itself to other programs in such a way that the virus code is executed when the infected program is executed.
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| DHCP |
The Dynamic Host Configuration Protocol (DHCP) consists of a protocol for delivering host-specific configuration parameters from a DHCP server to an Internet host and a mechanism for allocation of network addresses to hosts.
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| digital |
Digital describes any system based on discontinuous data or events.
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| DNS |
The Domain Name Service (DNS) is a TCP/IP protocol that searches for resources using a database distributed among different name servers. DNS lets you specify a symbolic name - in the format username@domain - instead of a numeric IP address.
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| Ethernet |
Ethernet is one of the most popular protocols for LANs. The terms Ethernet and the IEEE 802.3 standard are often used interchangeably. Ethernet supports data transfer rates of 10 Mbps. A newer version of Ethernet, called 100Base-T (or Fast Ethernet) supports data transfer rates of 100 Mbps. The newest version, Gigabit Ethernet, supports data rates of 1 gigabit (1,000 megabits) per second.
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| FDDI |
The Fiber Distributed Data Interface (FDDI) is a 100 Megabit technology for sending digital data over fiber optic cable.
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| firewall |
A system or combination of systems that enforces a boundary between two or more networks to prevent access by unauthorized persons.
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| FTP |
The File Transfer Protocol (FTP) provides the basic elements of file sharing between hosts. FTP uses TCP (Transmission Control Protocol) to create a virtual connection for control information and then creates a separate TCP connection for data transfers. The control connection uses an image of the TELNET protocol to exchange commands and messages between hosts.
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| HTTP |
The Hypertext Transfer Protocol (HTTP) is an application-level protocol with the speed necessary for distributed, collaborative, hypermedia information systems. Messages are passed in a format similar to that used by Internet Mail and the Multipurpose Internet Mail Extensions (MIME).
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| ICMP |
Internet Control Message Protocol (ICMP) is an extension to the Internet Protocol (IP) defined by RFC 792. ICMP supports packets containing error, control, and informational messages. The PING command, for example, uses ICMP to test an Internet connection.
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| IP |
Internet Protocol (IP) is the routing layer packet (datagram) delivery service of the TCP/IP suite. IP specifies the addressing scheme.
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| IP address |
The thirty-two bit, numeric, Internet Protocol (IP) address is an identifier for a computer or another device on a TCP/IP network. Messages are routed based on the IP address.
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| ISDN |
ISDN (Integrated Services Digital Network) is an all digital communications line that allows for the transmission of voice, data, video, and graphics at very high speeds, over standard communication lines. ISDN may be transmitted via telephone networks, packet switched networks, telex, CATV networks, and more. (Using built-in data compression with a theoretical 4:1 compression ratio, one ISDN line can provide 512 Kbps throughput.)
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| LAN |
A Local Area Network (LAN) is one that spans a relatively small area, and is often confined to a building, or a small group of buildings. LANs can be connected over any distance via telephone lines and radio waves. A system of LANs connected in this way is called a Wide Area Network (WAN).
Characteristics that distinguish one type of LAN from another include differences in topology (i.e., the geometric arrangement of devices on the network), protocols (i.e., the rules and encoding specifications for sending data), and the media (e.g., twisted-pair wire, coaxial cables, or fiber optic cables) by which devices are connected. Some networks do without connecting media altogether, communicating instead via radio waves. |
| MAC address |
The Media Access Control (MAC) address is a hardware address that uniquely identifies each node of a network.
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| network |
A network is a group of two or more computer systems linked together.
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| OC3 |
OC3 is an optical fibre line. OC3 (Optical Carrier) speeds are available from 35 Mbps through 155 Mbps.
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| OSPF |
The OSPF (Open Shortest Path First) protocol is a link-state routing protocol used for routing IP. OSPF is an interior gateway protocol that uses link-state technology for routing within a group of routers.
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PCMCIA
card |
PCMCIA (Personal Computer Memory Card International Association) is a nonprofit trade association (in Sunnyvale, California) that was created to standardize the connection of peripherals to portable computers. PCMCIA developed the PCMCIA card, a lightweight module about the size of a credit card that adds features to a portable computer.
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| PING |
Primarily used to troubleshoot Internet connections, the Packet INternet Groper (PING) is a utility for determining whether a specific IP address is accessible. PING sends a packet to the specified address and waits for a reply.
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| POP3 |
Post Office Protocol version 3 (POP3) permits workstations to dynamically access a maildrop on a server host (TCP/IP).
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| PPP |
PPP (Point-to-Point Protocol) is designed for simple links that transport packets between two peers. PPP provides a common solution for the easy connection of a wide variety of hosts, bridges and routers.
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| protocol |
A protocol is a format for the transmission of data between two devices. The protocol determines the type of error checking to be used, the data compression method (if any), how the sending device will indicate that it has finished sending a message, and how the receiving device will indicate that it has received a message.
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| protocol stack |
Also called the ISO/OSI (International Organization for Standardization/Open System Interconnection) reference model, a protocol stack is a framework consisting of seven layers that work together to transmit data from one network device to another.
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| RFC |
Essentially, RFCs (Requests for Comments) are a collection of notes about many aspects of computing and computer communication.
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| router |
A router is a device that connects any number of LANs (Local Area Networks) and routes data among them. Routers use headers and a forwarding table to determine where data packets go. |
| SMTP |
Modeled on FTP, Simple Mail Transfer Protocol (SMTP) is a protocol for transfering email messages between servers and providing delivery status.
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| T1 |
T1 is a high speed (1.544 Mbps) digital network developed by AT&T to support long-haul pulse-code modulation (PCM) voice transmission. The primary innovation of T1 was to introduce digitized voice and to create a network fully capable of digitally representing what was up until then, a fully analog telephone system. (T1-C operates at 3.152 Mbps, T-2 at 6.312 Mbps, T-3 at 44.736 Mbps, and T-4 at 274.176 Mbps.)
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| TCP |
Transmission Control Protocol (TCP) provides a reliable stream delivery and virtual connection service to applications, through the use of sequenced acknowledgement with retransmission of packets when necessary (TCP/IP).
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| TELNET |
TELNET is the terminal emulation protocol of TCP/IP (Transmission Control Protocol/Internet Protocol). TELNET allows a personal computer to connect to a server or a mainframe and transmit commands as if the PC were a hardwired terminal.
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| throughput |
The amount of data transferred or processed within a specified amount of time. Usually throughput is expressed in terms of Mbps or GBps.
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