| A | B |
|---|
| Internet | A large network made up of a number of smaller networks. |
| Intranet | An inhouse Web site that serves the employees of the enterprise. Although intranet pages may link to the Internet, an intranet is not a site accessed by the general public. |
| Packet | A block of data used for transmission in packet switched systems. The terms frame, packet and datagram are often used synonymously |
| ISP | An organization that provides access to the Internet. Small Internet service providers (ISPs) provide service via modem and ISDN while the larger ones also offer private line hookups (T1, fractional T1, etc.). Customers are generally billed a fixed rate per month, but other charges may apply. For a fee, a Web site can be created and maintained on the ISP's server, allowing the smaller organization to have a presence on the Web with its own domain name. |
| ISDN | (Integrated Services Digital Network) An international telecommunications standard for providing a digital service from the customer's premises to the dial-up telephone network. |
| IP address | (Internet Protocol address) The address of a computer attached to a TCP/IP network. Every client and server station must have a unique IP address. Client workstations have either a permanent address or one that is dynamically assigned to them each dial-up session. IP addresses are written as four sets of numbers separated by periods; |
| PPP | Point-to-Point Protocol) The communications protocol used to dial up the Internet over a serial link, such as a POTS or IDSN line. Developed by the Internet Engineering Task Force in 1994, it superseded the SLIP protocol. PPP establishes the session between the user's computer and the ISP using the Link Control Protocol (LCP), which also handles authentication (PAP, CHAP, etc.), compression and encryption. |
| Extranet | A Web site for customers rather than the general public. It can provide access to research, current inventories and internal databases, virtually any information that is private and not published for everyone. An extranet uses the public Internet as its transmission system, but requires passwords to gain entrance. Access to the site may be free or require payment for some or all of the services offered. |
| SMTP | Simple Mail Transfer Protocol) The standard e-mail protocol on the Internet. It is a TCP/IP protocol that defines the message format and the message transfer agent (MTA), which stores and forwards the mail. SMTP was originally designed for only ASCII text, but MIME and other encoding methods enable program and multimedia files to be attached to e-mail messages. |
| HTTP | HyperText Transport Protocol) The communications protocol used to connect to servers on the World Wide Web. Its primary function is to establish a connection with a Web server and transmit HTML pages to the client browser. Addresses of Web sites begin with an http:// prefix; however, Web browsers typically default to the HTTP protocol. |
| HTML | HyperText Markup Language) The document format used on the World Wide Web. Web pages are built with HTML tags (codes) embedded in the text. HTML defines the page layout, fonts and graphic elements as well as the hypertext links to other documents on the Web. Each link contains the URL, or address, of a Web page residing on the same server or any server worldwide, hence "World Wide" Web. |
| Protocol | Rules governing transmitting and receiving of data. |
| Router | A device that forwards data packets from one local area network (LAN) or wide area network (WAN) to another. Based on routing tables and routing protocols, routers read the network address in each transmitted frame and make a decision on how to send it based on the most expedient route (traffic load, line costs, speed, bad lines, etc.). Routers work at layer 3 in the protocol stack, whereas bridges and switches work at the layer 2. |
| Proxy server | Also called a "proxy" or "application level gateway," it is an application that breaks the connection between sender and receiver. All input is forwarded out a different port, closing a straight path between two networks and preventing a cracker from obtaining internal addresses and details of a private network. |
| PING command | (Packet INternet Groper) An Internet utility used to determine whether a particular IP address is online. It is used to test and debug a network by sending out a packet and waiting for a response. |
| LAN | Local Area Network- A communications network that serves users within a confined geographical area. It is made up of servers, workstations, a network operating system and a communications link. |
| WAN | Wide Area Network- A communications network that covers a wide geographic area, such as state or country. A LAN (local area network) is contained within a building or complex, and a MAN (metropolitan area network) generally covers a city or suburb. Following is a bandwidth comparison between major LAN and WAN technologies. |
| MAN | (Metropolitan Area Network) A communications network that covers a geographic area such as a city or suburb |
| Peer-to-peer network | A communications network that allows all desktop and laptop computers in the network to act as servers and share their files with all other users on the network. Peer-to-peer networks are quite common in small offices that do not use a dedicated file server. Peer-to-peer networks also exist on the Internet. For example, Napster and Gnutella allow users to access files in other users' computers. |
| Client-server network | A communications network that uses dedicated servers. In this context, the term is used to contrast it with a peer-to-peer network, which allows any client to also be a server. |
| Star Topology | A communications network in which all terminals are connected to a central computer, controller or hub. PBXs and telephone systems are prime examples as well as Token Ring and 10BaseT Ethernet |
| Bus Topology | A network topology that uses a common pathway between all devices. Ethernet 10Base5 and 10Base2 are examples of bus networks. |
| Ring Topology | A communications network that connects terminals and computers in a continuous loop |
| Mesh topology | A net-like communications network in which there are at least two pathways to each node. Since the term network means net-like as well as communications network, the term mesh is used to avoid saying "network communications network." |
| Hybrid topology | In communications, a network made up of equipment from multiple vendors. |
| OSI model | A seven layer model starting at physical layer one, and ending at application layer 7 |
| 10base5 | The original IEEE 10 Mbps Ethernet standard which uses a thick coaxial cable. Network nodes are attached via transceivers that tap into the cable and provide a line to a 15-pin plug in the adapter card known as the AUI interface. Also called "thick Ethernet," "ThickWire" and "ThickNet," 10Base5 has a distance limit of 1,640 feet without repeaters. See Ethernet |
| 10base2 | An earlier 10 Mbps Ethernet standard that uses a thin coaxial cable. Network nodes are attached to the cable via T-type BNC connectors in the adapter cards. Also called "thin Ethernet," "ThinWire," "ThinNet" and "Cheapernet," 10Base2 has a distance limit of 607 feet. |
| 10baseT | A 10 Mbps Ethernet standard that uses twisted wire pairs (telephone wire). All stations connect in a star configuration to a central hub, also known as a "multiport repeater," or to a central switch. 10BaseT has been widely used due to the lower cost and flexibility of installing twisted pair. It has mostly been superseded by 100BaseT, which is 10 times as fast |
| CSMA/CD | (Carrier Sense Multiple Access/Collision Detection) The LAN access method used in Ethernet. When a device wants to gain access to the network, it checks to see if the network is quiet (senses the carrier). If it is not, it waits a random amount of time before retrying. If the network is quiet and two devices access the line at exactly the same time, their signals collide. When the collision is detected, they both back off and each wait a random amount of time before retrying. |
