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WEEK-V

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HARDWARE AND SOFTWARE COMPONENTS OF NETWORK

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INTRODUCTION

• Computer Network components comprise of both physical or hardware parts and also software required for installing computer networks at organizations and at homes also.
• A network is basically used for sharing of information via network components.
• So, the network component plays a major role in designing and maintaining a network.
• The hardware components are NIC, server, client, peer, transmission medium, and connecting devices.
• The software components are operating system and protocols. Figure illustrates some components.

Computer Network Components

COMMON NETWORK DEVICES

The common network devices are hardware and software components.

Hardware Components

• Network hardware, also known as network equipment or computer networking devices, are electronic devices which are required for communication and interaction between devices on a computer network.
• Specifically, they mediate data transmission in a computer network. They are –
• NIC – Network Interface Card
• Computers: Server, Client, Peers

• Transmission Media: Cables with connectors
• Connecting Devices: Repeaters, Hubs/ Switches, Routers, Bridges,

Gateways, Access Point, Modem

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• Connecting devices act as middleware between networks or computers, by binding the network media together.
• Connecting devices can operate in different layers of the Internet model.
• There are three kinds of connecting devices: hubs, link-layer switches, and routers. Hubs today operate in the first layer of the Internet model. Link-layer switches operate in the first two layers.
• Routers operate in the first three layers. Figure shows the categories of connecting devices.

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Three categories of connecting devices

Software Components

Networking Operating System − Network Operating Systems is typically installed in the server and facilitate workstations in a network to share files, database, applications, printers etc.

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Protocol Suite − A protocol is a rule or guideline followed by each computer for data communication. Protocol suite is a set of related protocols that are laid down for computer networks. The two popular protocol suites are −              

a. ISO - OSI Model (Open System Interconnections)

b. TCP / IP Protocol Suite

COMPUTERS

• On the network or internet, computer systems are servers, clients and peers.
• Servers −Servers are high-configuration computers that manage the resources of the network.
• The network operating system is installed in the server and so they give user accesses to the network resources.
• Servers can be of various kinds: file servers, database servers, print servers etc.
• Clients − Clients are computers that request and receive service from the servers to access and use the network resources.
• Peers − Peers are computers that provide and receive services from other peers in a workgroup network.

Computers on Network or Internet

ACCESS POINTS

• The access point connects multiple wireless devices together in a single wireless network.
• Access point supports both type of standards; Ethernet and Wi-Fi.
• Access point uses radio signals to provide the connectivity.

• Based on functionality an access point can be categorized in three types; standalone, multifunction and client.
• A standalone access point works in the wireless network exactly as the switch works in the wired network.
• To control the unauthorized access, Access point uses authorization.
• To extend the coverage area, multiple access points are used together under a Wireless LAN Controller.
• An access point which works under the WLC is known as the LWAP (Lightweight Access Point).
• In WLC-LWAPs setup, the WLC controls and manages all LWAPs.
• A LWAP works as the bridge between the WLC and the end device.

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A Wireless Access Point

Hub

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• A hub is a network connecting device.
• It is used to connect the computers in local area network.
• A hub is a device that splits a network connection among multiple computers.
• It works similarly to a distribution center.
• When a computer requests information from one network or from a specific computer, then it sends the request to the hub through a cable.
• The hub then receives that request and transmits it to the entire network.

• After that, every computer checks whh ether that network belongs to them or not.
• If belongs then it broadcasts if the request doesn’t belong it will be dropped.
• But such network components nowadays are very less in circulation and being replaced by more advanced communication devices such as Routers and Switches.
• This hub is basically a multiport repeater.
• This hub is used to connect multiple connections that come from different branches, For example, the connector in star topology is used to connect different stations for data access.

Fig. A hub

SWITCH

• The switch is another network connecting device.
• It is a component that helps devices to connect the networks so that they can transfer data to other connected devices.
• These network switches are identical to network hubs, but a switch has more advanced features than a hub.
• It doesn’t broadcast entire data on the network like a hub.

• The advanced features of the switch imply that the network switch first inspects the incoming packet and determines its source, destination address, and routes after that sends the data at the correct destination accordingly to that packet.
• A network switch is also called the Switching hub, Bridging hub, and MAC bridge.

Fig.: A switch

ROUTER

• The router is a hardware network component.
• It is used to connect two logically and physical different networks.
• All the communication on the internet is based on the router.
• Routers operate at the network layer of the OSI - Open system interconnection Reference Model, using them to send packets over the network using a logical address.
• Any data which travels from one network to another network is in the form of a Packet.
• The router receives such packet data and forwards it to the destination device after analyzing hidden information in the Data Packet.

• This networking device is used to connect different networks which are either wired or wireless.
• These networks are mainly seen in the house as Wi–Fi from which anyone can access the Internet.

Fig.: A broadband router

REPEATERS

• A Repeater is an electronic device that receives a signal and retransmits it.
• A repeater is a powerful network component that is used to regenerate signals.
• With this, the signal is fixed for a long time, so that the strength of the signal remains stable.
• Repeater takes data signals from the communication medium and amplifies them and sends them back to the communication medium.
• When the signal becomes weak, this device copies the signal bit by bit and then regenerates it to its original strength for making the internet connection stable.

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• A repeater is located in the first layer (physical layer) of the OSI layer. Repeaters are used in cables that have to cover distances of up to 100 meters.
• These components receive signals from cables like optical fibers, coaxial cables, and copper cables.

Fig.: A repeater

NIC - NETWORK INTERFACE CARD (NIC) OR NETWORK ADAPTER CARD

• NIC is a hardware accessory that provides a computer with both a physical interface for accepting a network cable connector and the ability to process low-level network information.

MODEM

• A modem is a hardware device that allows the computer to connect to the internet over the existing telephone line
• A modem is not integrated with the motherboard rather than it is installed on the PCI slot found on the motherboard.
• It stands for Modulator/Demodulator.
• It converts the digital data into an analog signal over the telephone lines.
• Based on the differences in speed and transmission rate, a modem can be classified in the following categories:
• Standard PC modem or Dial-up modem
• Cellular Modem
• Cable modem

Fig. : A modem

• Two more important Network connecting devices are bridge and gateway
• Bridges - Bridge is a device that has such functionality that it filters the content, for which it reads MAC addresses of both source and destination.
• The bridge connects two LANs (Local Area Network) using the same protocol. This device operates in the data link layer of the OSI Model.
• These network components are very useful for filtering the data load of traffic, for which they divide them into segments or packets.
• The bridge controls the data traffic of LANs or other networks.
• These bridges are actually passive devices, as there is no interaction between bridged and paths of bridging.

• Gateways - A gateway is a hardware device that acts as a “gate” within two networks.
• It can also be a router, firewall, server, or any other device that enables traffic to flow in and out of the network.
• Gateways are used to connect networks based on different protocols.
• As a bridge is used to join two similar types of networks, similarly, the gateway is used to join two dissimilar networks.
• This gateway node is located at the edge of the network and all the data flows through it which enters or exits the network.
• In addition, it can also translate received data that is received from outside networks, into a format or protocol that can be identified by devices within the internal network

LAN CABLES AND LAN CONNECTORS

• Transmission media are the channels through which data is transferred from one device to another in a network.
• Transmission media may be guided media like coaxial cable, fibre optic cables etc; or maybe unguided media like microwaves, infra-red waves etc.
• They are also termed as LAN Cables.
• Transmission media are located below the physical layer and are directly controlled by the physical layer.
• Transmission media can be considered to belong to layer zero.

Fig.: Transmission medium and Physical layer

• A transmission medium can be broadly defined as anything that can carry information from a source to a destination.
• For example, the transmission medium for two people having a dinner conversation is the air.
• The air can also be used to convey the message in a smoke signal or semaphore.
• For a written message, the transmission medium might be a mail carrier, a truck, or an airplane.

• In data communications, the definition of the information and the transmission medium is more specific.
• The transmission medium is free space or metallic cable or fiber-optic cable.
• The information is a signal that is the result of a conversion of data from another form.
• In telecommunications, transmission media can be divided into two broad categories:
• guided media
• unguided media.

Guided media include twisted-pair cable, coaxial cable, and fiber-optic cable.

Unguided medium is free space or air

Fig.: Classes of transmission media

WIRED MEDIA - GUIDED MEDIA

• Guided media are those that provide a channel or canal from one device to another.
• The different guided media considered are –
• coaxial cable
• twisted-pair cable
• Fiber optic cable
• A signal traveling along any of these media is directed and contained by the physical limits of the medium.
• Twisted-pair and coaxial cable use metallic or copper conductors that accept and transport signals in the form of electric current.
• Optical fiber is a cable that accepts and transports signals in the form of light.

COAXIAL CABLE

• Coaxial cable or coax carries signals of higher frequency ranges than those in twisted pair cable, in part because the two media are constructed quite differently.
• Instead of having two wires, coax has a central core conductor of solid or stranded wire usually copper, enclosed in an insulating sheath, which is, in turn, encased in an outer conductor of metal foil, braid, or a combination of the two.
• The outer metallic wrapping serves both as a shield against noise and as the second conductor which completes the circuit.
• This outer conductor is also enclosed in an insulating sheath, and the whole cable is protected by a plastic cover.

Figure: Coaxial Cable.

COAXIAL CABLE CONNECTORS

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• To connect coaxial cable to devices, coaxial connectors are needed.
• The most common type of connector used today is the Bayonet Neill-Concelman (BNC) connector.
• Types :BNC connector, BNC T connector, and BNC terminator.

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Figure.: BNC Connectors

• The BNC connector is used to connect the end of the cable to a device, such as a TV set.
• The BNC T connector is used in Ethernet networks to branch out to a connection to a computer or other device.
• The BNC terminator is used at the end of the cable to prevent the reflection of the signal.

TWISTED-PAIR CABLE AND CONNECTOR

• A twisted pair cable consists of two conductors, mainly of copper, each with its own plastic insulation, twisted together, as shown in Figure.

Unshielded Versus Shielded Twisted-Pair Cable

• The most common twisted-pair cable used in communications is referred to as unshielded twisted-pair - UTP.
• IBM has also produced a version of twisted-pair cable for its use, called shielded twisted-pair (STP).
• STP cable has a metal foil or braided mesh covering that encases each pair of insulated conductors.
• Although metal casing improves the quality of cable by preventing the penetration of noise or crosstalk, it is bulkier and more expensive.

Fig.: UTP and STP cables

TWISTED PAIR CONNECTORS

• The most common UTP connector is RJ45 (RJ stands for registered jack)
• The RJ45 is a keyed connector, meaning the connector can be inserted in only one way.

Fig.: UTP Connectors

FIBER OPTIC CABLES

• A fiber-optic cable is made of glass or plastic and transmits signals in the form of light.
• To understand optical fiber, there is a need to explore several aspects of the nature of light.
• Optical fibers use reflection, to guide light through a channel.
• A glass or plastic core is surrounded by a cladding of less dense glass or plastic.

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• The difference in density of the two materials must be such that a beam of light moving through the core is reflected off the cladding instead of being refracted into it.

Fig.: Optical fiber

FIBER-OPTIC CABLE CONNECTORS

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• There are three types of connectors for fiber-optic cables.
• The subscriber channel (SC) connector is used for cable TV.
• It uses a push/pull locking system.
• The straight-tip (ST) connector is used for connecting cable to networking devices.

Fig.: Fiber Optic Cable Connectors

Advantages and Disadvantages of Optical Fiber

Advantages

❑ Higher bandwidth - Fiber-optic cable can support dramatically higher bandwidths than either twisted-pair or coaxial cable. Currently, data rates and bandwidth utilization over fiber-optic cable are limited not by the medium but by the signal generation and reception technology available.

❑ Less signal attenuation - Fiber-optic transmission distance is significantly greater than that of other guided media. A signal can run for 50 km without requiring regeneration. Repeaters are needed at every 5 km for coaxial or twisted-pair cable.

❑ Immunity to electromagnetic interference - Electromagnetic noise cannot affect fiber-optic cables.

❑ Resistance to corrosive materials - Glass is more resistant to corrosive materials than copper.

❑ Light weight - Fiber-optic cables are much lighter than copper cables.

❑ Greater immunity to tapping - Fiber-optic cables are more immune to tapping than copper cables. Copper cables create antenna effects that can easily be tapped.

Disadvantages

❑ Installation and maintenance - Fiber-optic cable is a relatively new technology. Its installation and maintenance require expertise that is not yet available everywhere.

❑ Unidirectional light propagation - Propagation of light is unidirectional. If we need bidirectional communication, two fibers are needed.

❑ Cost - The cable and the interfaces are relatively more expensive than those of other guided media. If the demand for bandwidth is not high, often the use of optical fiber cannot be justified

FIREWALL

• A Firewall is a network security device that monitors and filters incoming and outgoing network traffic based on an organization’s previously established security policies.
• At its most basic, a firewall is essentially the barrier that sits between a private internal network and the public Internet.
• A firewall’s main purpose is to allow non-threatening traffic in and to keep dangerous traffic out.

FIRMWARES

• Firmware is a software program on the hardware device, which perform functions like basic input/output tasks and offers necessary instructions for the device to communicate with other computing devices.
• It is a set of instructions programmed that is permanently fixed into a hardware device like video cards, BIOS, keyboards, or hard drives.
• Without using special programs, it cannot be modifying or deleted by an end-user, unlike normal software.
• It remains on that device whether it is on or off. But firmware is stored in the flash ROM, which is actually a kind of flash memory and allows users to erase and rewrite information.

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ISPs – INTERNET SERVICE PROVIDERS

• An Internet service provider (ISP) is a company that provides customers with Internet access.
• It is often referred to as just “the provider.”
• Data may be transmitted using several technologies, including dial-up, DSL, cable modem, wireless or dedicated high-speed interconnects.
• ISPs also provide their customers with the ability to communicate with one another by providing Internet email accounts, usually with numerous email addresses at the customer’s discretion.
• Other services, such as telephone and television services, or personal websites or home pages may be provided as well.
• The services and service combinations may be unique to each ISP.

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Fig.: Companies providing internet services