• Bridges - A bridge is a device that passes data packets between multiple network segments that use the same communications protocol. A bridge passes one signal at a time. If a packet is destined for a computer within the sender's own network segment, the bridge retains the packet within that segment. If the packet is destined for a computer on another segment, the bridge will pass the packet to that segment.
  
  
• CSMA/CD - Carrier Sense Multiple Access with Collision Detection. A set of rules that determines how network devices respond when two devices attempt to send data on the network simultaneously. Used by Ethernet like a token is used in a Token Ring.
  
  
• Domain - refers to a shared security domain wherein a user can log on to a one authentication server that will then introduce the user to all other secure shared resources.
  
  
• Ethernet collision domain - a single Ethernet subnetwork.
  
  
• Frames - Data link equipment transmits information in units called frames, which address data to specific recipients and ensure the integrity of data transmissions.
  
  
• Gateways - Gateways enable communications between different network architectures. A gateway takes the data from one network and repackages it, so that each network can understand the other network's data.
  
  
• Hubs - Hubs are connectivity devices that conenct computers in a star topology. Passive Hubs are simply wiring panels, Active Hubs (aka multiport repeaters) receive incoming signals, process the signals, and retransmit them at their original strengths and definitions.
  
  
• Internetwork - refers to networks that are connected via routers.
  
  
• Internet - refers to the global internetwork of TCP/IP hosts to which most major governements and businesses are now attached.
  
  
• Intranet - refers to TCP/IP internetworks that exists entirely inside an organization but use the software and methods made standard by the global Internet.
  
  
• Internet domain - a logical grouping of TCP/IP hosts on the internet.
  
  
• MSAU - MultiStation Access Unit. Used with token ring networks having a physical topology of a star.
  
  
• Network - refers to a group of similar subnetworks that are bridged or switched together.
  
  
• Packets - Transport protocols work by providing additional addressing embedded in units called packets, which are carried inside frames and tell routers and gateways how to switch the packet onto other data link networks to which the gateway is attached.
  
  
• Repeaters - Repeaters receive signals and retransmit them at their original strength and definition. Both ends of the network must use the same access methods (ethernet, token ring, etc).
  
  
• Routers - A router is a device that acts like a bridge or switch but provides more functionality. In moving data between different network segments, routers examine a packet's header to determine the best path for the packet to travel. A router knows the path to all of the segments on the network by accessing information stored in the router's routing table. Routers enable all users in a network to share a single connection to the Internet or a WAN.
  
  
• Segment - A cable that connects two computers or network components.
  
  
• Subnetwork - refers to a single shared media network such as an Ethernet collision domain or a Token Ring.
  
  
• Switches - Switches are similar to bridges but offer a more direct network connection between the source and destination computers. When a switch receives a data packet, it creates a seperate internal connection, or segment, between any two of its ports and forwards and data packets to the appropriate port of the destination computer only, based on information in each packet's header. The insulates the connection from the other ports and gives the source and destination computers access to the full bandwidth of a network.
  
  
• Transport Protocols - allow data to move between different types of data link equipment and guarantee the delivery of all data between any two nodes on the same internetwork.
  
  
• Digital signaling is also known as discrete state signaling (wire voltage +5/-5 or fiber light pulses on/off).
  
  

• Bus - Computers are connected to a common, shared cable. Requires termination.
  
  
• Star - Computers are connected to cable segments that branch out from a central location, or hub.
  
  
• Ring - Computers are connected to a cable that forms a loop around a central location.
  
  
• Mesh - Computers on the network are connected to every other computer by cable.
  
  
• Hybrid - Two or more topologies are used together (eg. Star-Bus or Star-Ring).
  
  

• Hard disk drive controllers - are high-speed peripherals that connect computers to hard disk drives. Simple hard disk controllers are usually built into motherboards, but servers usually require the installation of more complex disk controllers.
  
  
• Hard disk drives - are the long-term storage areas of a computer. Programs can be stored permanently on hard disk drives and loaded into RAM when they are needed.
  
  
• Input/Output (I/O) devices - provide low-speed connections to simple peripherals such as keyboards, printers, modems, and uninterruptible power supplies. These devices do not need complex high-speed network or disk interfaces.
  
  
• Microprocessor - are the brains of the computer. They perform lists of instructions called programs.
  
  
• Motherboard - is the nervous system of a computer. It connects all the components of a computer into one functional device.
  
  
• Network adapters - attach individual computers to a network of computers.
  
  
• Random access memory (RAM) - is the short-term memory of a computer. Programs are stored in RAM, as is the data upon which programs operate. RAM is erased every time a computer is shut off.
  
  
• Video adapters - create images from image maps stored in RAM and created by the microprocessor. You must have a video adapter to interact with a computer, and most machines will not operate without one.
  
  

• Environment Subsystem - are services of Windows NT that provide a complete shell in which programs written for the MS-DOS, Windows 3.11, and OS/2 1.3 run.
  
  
• POSIX - Portable Open Systems Interface.
  
  
• RAID - Redundant Arrays of Indexpensive Disks.
  
  
• RISC - Reduced Instruction Set Computer.
  
  

Open Systems Interconnection

	Application
	Presentation
	Session
	Transport
	Network
	Data Link
		Logical Link Control (llc)
		Media Access Control (mac)
	Physical