computer networks

• A computer network is a collection of computers and devices connected together via communication devices and transmission media
• Communication describes a process in which two or more computer or devices transfer data, instructions, and information
• Network devices are components used to connect to a computers or other electronic devices so that they can share files or resources
• Network devices are also known as communicating devices
• Hub is a network using a star topology require a central point for the device to connect.
• Hub is originally called as concentrator since it consolidated the cable runs from all network devices
• Switches are a special type of hub that offers additional layer of intelligence to basic, physical-layer repeater hubs
• In digital communication systems, a repeater is a device that receives a digital signal on an electromagnetic or optical transmission medium and regenerates the signal along the next leg of the mission
• A bridge is used to join two network segments together, it allows computers on either segment to access resources on the other
• Routers are networking devices used to extend or segment networks by forwarding packets from one logical network to another
• A modem is a device that makes it possible for a computers to communicate over telephone lines
• modem comes from modulate and demodulate
• a firewall is a piece of hardware and/or software which functions in a networked environment to prevent some communications forbidden by the security policy
• PAN - personal area network

  CAN - campus area network

  WLAN - wireless local are network

  MAN - metropolitan area network

  WAN - wide area network
• the internet is the world's largest WAN
• WAN is a network that covers a large geographical are such country or the world
• LAN is a network that connects computers and devices in a limited geographical area such as a home, school computer laboratory, office building
• MAN is a high speed network that connects LAN that connects are such as city or town and handles bulk of communication activity across the region
• LAN MAN WAN

  COST LOW HIGH HIGHER

  SIZE SMALL LARGER LARGEST

  SPEED FASTEST SLOWER SLOWEST

  NO. OF COMPUTER SMALLEST LARGE LARGEST
• star topology is a topology for a LAN in which all nodes are individually connected to a central connection point like a hub or a switch
• ring topology is a network topology in which each node connects to exactly two other nodes, forming a single continuous pathway for signals through each node
• bus topology is a network topology in which nodes are directly connected to a common half-duplex link
• topology - the cabling layout used to link devices is the physical topology of the network
• network architecture focuses on the design of the entire computer network
• intranet is a computer network for sharing information, easier communication, collaboration tools, operational systems, and other computing services within an organization, usually to the exclusion of access by outsiders
• extranet is a private network but typically open to external parties, such as business partners, suppliers, key costumers, etc.
• internet is a vast network that connects computers all over the world