File Server

A File server is a high capacity computer that provides various resources to the network.
the heart of a network

• need a very fast computer with a large amount of RAM and storage space, a fast network interface card, and a tape back-up device
• need network operating system such as Novell Netware, Windows NT server, or Apple Share
• control the communication of information between the nodes on a network
  

Workstations

A computer in a network is called workstation or client.

• a computer connected to a network
• need a network interface card
• not necessarily need floppy disk drives or hard disks since files can be saved on the file server
  

Network Interface Cards (NICs)

NIC provides the link between your computer and your network.

• provide the physical connection between the network and the workstation
• most are internal, with the card fitting into an expansion slot inside the computer
• some build on the motherboard
• affect the speed and performance of a network
• three common network interface connections: Ethernet cards, LocalTalk connectors, Token Ring cards

Hubs/Concentrators

A hub is a device whose primary function is to send and receive signals along the network between the nodes connected to it.

• connect multiple devices to the network
• commonly found in star and star-wired ring topology networks
• entire network shuts down if there is a problem on a hub
• serve as a central meeting place for cables from computers, servers and peripherals
• usually configured with 4, 8, 12, or 24 RJ-45 ports

Repeaters

A repeater is a device that regenerates and amplifies signals to create long-distance networks

• simply receive, amplify and rebroadcast the signals
• some repeaters provide basic error-checking
• can be separate devices or they can be incorporated into a concentrator
• inexpensive, used to overcome distance limitations
  

Bridges

A bridge is a device that links two homogenous packet-broadcast local networks. It accepts all packets from each network addressed to devices on the other, buffers them, and retransmits them to the other network.

• connect two or more networks using the same address method or protocol
• can provide some addressing information
• monitor and manage the traffic to maintain optimum performance on both sides of the network
• often used when LANs reach their capacity of nodes

Switches

A switch is a high-speed multiport bridge. Today, switches are replacing multiport repeaters or concentrators in a UTP environment.

• an intelligent hub that maintains a bridging table, keeping track of which hardware addresses are located on which network segment
• more efficient than with any other type of hub
• ability to dedicate bandwidth to each port on the switch

Routers

Routers are similar to bridges in that they link two or more physically separate network segments. The network segments linked by a router, however, remain logically separate and can function as independent networks.

• translate information from one network to another; similar to a super-intelligent bridge
• maintain a map of the network, select the best route for data
• access to more network level knowledge than is available to bridges
• information on source addresses, destination addresses, path distances, and in some cases,
• segment bandwidth and segment status are contained in the router's routing table
• translates local addresses (eg. "spot") into network addresses (eg. 131.44.99.12)
• can translate messages with different addressing methods
• can act as firewalls (many ISP's block traffic at the router level)
• direct signal traffic efficiently
• route messages between any two protocols
• can route messages between linear bus, star, and token ring topologies
• can route messages across fiber optic, coaxial, and twisted-pair cabling