Network Hardware and Physical Media l Network hardware

Network Hardware and Physical Media l Network hardware includes: – – Computers Peripherals Interface cards and Other equipment needed to perform data processing and communications within the network

File servers l l A very fast computer with a large amount of RAM and storage space along with a fast network interface card The network operating system software resides on this computer

Workstations l All computers connected to the file server on a network are called workstations

Network interface cards l l l The network interface card (NIC) provides the physical connection between the network and the computer workstation. Most NICs are internal with the card fitting into an expansion slot in the computer. Three common network interface connections are Ethernet cards, Local Talk connectors and Token Ring cards

Ethernet cards l l The most common Network Interface Cards are Ethernet cards They contain connections for either coaxial or twisted pair cables, or both Co-axial cable Twisted pair cable

Concentrators / Hubs l l A concentrator is a device that provides a central connection point for cables from workstations, servers and peripherals Hubs are multi-slot concentrators

Switches l l hubs provide an easy way to scale up and shorten the distance that the packets must travel to get from one node to another they do not break up the actual network into discrete segments. That is where switches come in.

Switches (continued) l A vital difference between a hub and a switch is – all the nodes connected to a hub share the bandwidth among themselves. – l while a device connected to a switch port has the full bandwidth all to itself. Think of a switch as a ‘clever’ hub

Repeaters l l A signal loses strength as it passes along a cable, so it is often necessary to boost the signal with a device called a repeater A repeater might be a separate device, or might be part of a concentrator

Bridges l A bridge is a device that allows you to segment a large network into two smaller, more efficient networks

An example of a network with a bridge Router Hub Bridge Hub Internet Segment Node

Routers l l l A router translates information from one network to another The router directs traffic to prevent “head-on” collisions If you have a LAN that you want to connect to the Internet, you will need a router to serve as the translator between information on your LAN and the Internet

Routers (continued)

Physical Media l l Physical media provide the connections between network devices that make networking possible There are four main types of physical media in widespread use today: – – Coaxial Cable Twisted Pair Fiber Optic Cable Wireless Media

LAN Technologies Ethernet Physical Media : 10 Base 5 10 Base 2 10 Base. T 10 Base. FL - Thick Co-axial Cable with Bus Topology Thin Co-axial Cable with Bus Topology UTP Cat 3/5 with Tree Topology Multimode/Singlemode Fiber with Tree Topology Maximum Segment Length 10 Base 5 10 Base 2 10 Base. T - 500 m with at most 4 repeaters (Use Bridge to extend the network) - 185 m with at most 4 repeaters (Use Bridge to extend the network) - 100 m with at most 4 hubs (Use Switch to extend the network)

Thick Coaxial Cable l l l l l Used in the first Ethernet networks Type RG-11 / 10 Base 5 Usually orange/black Thickness of a small garden hose Very expensive and heavy cable Two strands along the axis Conductor down the center Insulator surrounds conductor Shielded mesh serves as outside

Thin Coaxial Cable l l l l Alternative to Thick Ethernet Cable Type RG-58 / 10 Base 2 / “Cheapnet” Usually black Thickness of a pencil More flexible than thick Ethernet Reduced the cost of the cabling Flexible

Coaxial cable connectors l The most common type of connector used with coaxial cables is the BNC connector

Twisted Pair Cable l l l Phone Systems Twisted Pair Cable consists of two copper wires, usually twisted around each other to cancel out any noise in the circuit Two main type of Twisted Pair Cabling – – Shielded Twisted Pair (STP) Unshielded Twisted Pair (UTP)

Shielded Twisted Pair (STP) l l STP is the original media used for token ring networks STP can be used for high-speed networks, such as FDDI or ATM, where shielding is important. RJ-45

Unshielded Twisted Pair (UTP) l l UTP has four pairs of wires inside the jacket Each pair is twisted with a different number of twists per inch to help eliminate interference from adjacent pairs

UTP (Continued) l l Most commonly used twisted pair cable Uses common telephone wire UTP was standardized by the IEEE 802. 3 committee in October of 1990 UTP for LANs is now classified as: – – – Category 3 - used for LANs up to 10 Mbps Category 4 - used for LANs up to 16 Mbps Category 5 - used for LANs up to 100 Mbps

Fiber Optic Cable l l l Fiber optic cabling consists of a center glass core surrounded by several layers of protective materials It transmits light rather than electronic signals It is the standard for connecting networks between buildings, due to its immunity to the effects of moisture and light

Fiber Optic (continued) l l l Fiber optic cable has the ability to transmit signals over much longer distances than coaxial or twisted pair It can also carry information at vastly greater speeds Fiber optic cable is more difficult to install than other cabling

Wireless LANS – – Wireless networks use high frequency radio signals to communicate between the workstations and the fileserver or hubs. Disadvantages of wireless networks are: l l they are expensive (relatively), provide poor security, are susceptible to interference and are slower than cabled networks