study material for networking essentials

8/6/2019 Study Material for Networking Essentials

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Learning Academy


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Learning Academy Notes 2

Networking Essentials

Introduction

A network is a group of systems that are interconnected to allow sharing of filesor sharing of resources (like printers) or for the purpose of sharing services like internet.

Objective

This module will focus on

Understanding computer networks and its importance.

Different ways of classifying computer networks. Transmission Media

Media Access Methods LAN Technologies

Classification of computer networks

Network

Based onfunctional

Relationship

Based on

GeographicalDistance

Based onTopology

LANMAN

WAN

Peer to Peer Client Server

BusStar Ring Mesh

Hybrid


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Computer networks can be classified on various ways based on

Geographical Distance: Computer networks may be classified according to the scale or

extent of reach of the network as Local Area Network (LAN), Metropolitan AreaNetwork (MAN) and Wide Area Network (WAN).

Local Area Network (LAN): A network that is limited to a relatively small

spatial area such as a room, a single building, a ship, or an aircraft is reffered as LAN.They are sometimes called a single location network.eg. A small office network or two

computers is a house connected using a cable.

Metropolitan Area Network (MAN): A network that connects two or moreLocal Area Networks together but does not extend beyond the boundaries of the

immediate town, city, or metropolitan area is called as MAN. eg. A branch office

connected to the main office in the same city.

Wide Area Network (WAN): A WAN is a data communications network that

covers a relatively broad geographic area and that often uses transmission facilities provided by common carriers, such as telephone companies etc. Eg. Internet or a branch

office in India connected to its Corporate office in United States.

Functional Relationship: Based on the relationship that computers share in a networkthey can be classifed as Peer Peer and Client Server architechtures or networks.

Peer to Peer: A peer to peer network (also called as Workgroup by Microsoft) is

built without the use of a central server and each peer computer can share its resourceswith the other computers on the network independently. Special software protocols such

as Microsoft NetBEUI and Apples LocalTalk are used for establishing communicationacross Peer to Peer network.


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Advantages

Low cost as expensive software and hardware are not required. Easy to implement.

Resource sharing controlled by users. No need of a dedicated network administator.

Disadvantages

Low level of security

Heavy load on computers because of resource sharing.

Size of network limited to approximately 10 computers.

Client Server : In Client Server architechure a centralized computer is used to

facilitate the sharing of data and hardware with other computers on the network. Thesecentral computers are called Servers and the computers using the server are called clients.


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Advantages

Strong central security.

Central file storage. Resource sharing controlled by administrators.

Easy management of large number of users.

Disadvantages

Cost of server hardware and software. Dedicated and well trained network administrator is needed to main this

type of architecture.

Network Topology: Network Topology is defined as the way in which computers arearranged in a network. Computer networks may be classified according to the network

topology upon which the network is based, such as Bus network, Star network, Ringnetwork, Mesh network, Hybrid network, etc.

Bus Topology: A bus network topology is a network architecture in which a set

of clients are connected in a linear fashion via a shared communications line (backbone),called a bus.
http://en.wikipedia.org/wiki/Computer_bushttp://en.wikipedia.org/wiki/Client_(computing)http://en.wikipedia.org/wiki/Computer_networkhttp://en.wikipedia.org/wiki/Mesh_networkhttp://en.wikipedia.org/wiki/Ring_networkhttp://en.wikipedia.org/wiki/Star_networkhttp://en.wikipedia.org/wiki/Bus_networkhttp://en.wikipedia.org/wiki/Network_topology


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With a bus topology, when a computer sends out a signal, the signal travels thecable length in both directions from the sending computer. When the signal reaches the

end of the cable length, it bounces back and returns in the direction it came from(signalbounce). Signal bounce is a problem, because if another signal is sent on the cable length

as the same time, the two signals will collide and be destroyed and then must beretransmitted. For this reason, at each end of the cable there is a terminator. The

terminator is designed to absorb the signal when the signal reaches the end, preventingsignal bounce.

Advantages

Easy to implement and extend.

Requires less cable length when compared to star topology. Well suited for temporary or small networks not requiring high speeds

(quick setup). Cost effective that other topologies.

Disadvantages

Difficult to administer/troubleshoot.

Scalability is very low.

Problem with the backbone cable leads to entire network failure. Performance degrades as additional computers are added or on heavy

traffic.( If many computers are attached, the amount of data flowingcauses the network to slow down.)

Bus Topology


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Star Topology: In star topology, all computers are connected through one central device

known as a hub or a switch. All the pheripheral nodes (computers) can thus communicatewith all others by transmitting to and receiving from, the central node (hub/switch) only.

Advantages

Scalable, easy to set up and to expand.

Failure of a single cable or a single computer doesnot affect the entirenetwork.

Easy to a administer/troubleshoot. Data packets are sent quickly as they do not have to travel through any

unnecessary nodes.

Disadvantages

Extra hardware (Hub/Switch) required. Failure of Hub/Switch leads to entire network failure.

Ring Topology: A ring network is a network topology in which each nodeconnects to exactly two other nodes, forming a circular pathway for signals: a ring. Data

travels in one direction from node to node, with each node handling every message.

Star Topology
http://en.wikipedia.org/wiki/Network_topology


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Advantages

Signal degeration is low because each workstation is responsible for

regenerating or boosting the signal.

Disadvantages

The biggest problem with ring topology is that if one computer fails or thecable link is broken the entire network could go down.

When there is a cable change or when a workstation is moved in thenetwork, brief disconnection can interrupt or bring down the entire

network.

Mesh Topology: A mesh topology consists of a network where every device on

the network is physically connected to every other device on the network.

A

B

C

D

Rin To olo

Mesh Topology


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Advantages

Fault Tolerance

Provides great deal of performance and reliability.

Disadvantages

Very hard to administer and manage because of numerous connections.

Costly because of the additional cabling and network interfaces to createmultiple pathways between each system.

Hybrid Topology:A hybrid topology is a combination of any two or morenetwork topologies.For Example, a popular hybrid topology is the star bus topology, in

which a number of star topologies are connected by a central bus topology.

Transmission Media

The foundation of any network is the transmission media or the circuitry used to

interconnect and carry network signals between systems. Transmission media provide thepath for one computer to transfer information to another. The purpose of transmission

media is to transport a raw bit stream from one machine to another.

Transmission Media

Wired Wireless

Radio Waves

Infrared

MicrowaveCopper Cable Fibre Optic Cable

Coaxial Twisted Pair

Thicknet ThinnetSTP UTP


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We can classify transmission media into two broad categories,

Wired Media.

Wireless Media.

Wired Media

The most commoly used wired media are

Copper cable, which carries electrical signals. Fibre optic cable, which carries optic signals.

Copper Cable: Copper cables uses differences in voltage inorder to transmitt andreceive data. The different types of copper cables used in networking are

Co axial cables Twisted pair cables.

Co axial cable: A co axial cable consists of a stiff copper wire as the core, surrounded by an insulating material. The insulator is encased by a mesh of conducting material,woven as a braided mesh.The outer conductor is covered in a protective plastic sheath.

There are two types of co axial cables thicknet and thinnet co axial cables.

Thinnet Co axial Cables (10 Base 2): Thinnet refers to co axial cables that

are lesser in diameter and in which the the braided mesh is loosely oven.


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Thicknet Co axial Cables (10 Base 5): Thickent refers to cables that arethicker and in which the braided mesh is tightly woven.

Thicknet versus Thinnet

Coax Type Cable

Grade

Thickness Maximum

Distance

Transfer

Rate

Connector

Thinknet RG 58 .25 inch 185 m 10 Mbps BNC

Thicknet RG 8 .5 inch 500 m 10 Mbps AUI

Twisted Pair Cables (10 Base T): A twisted pair cable consists of four pairs(eight individual wires), which are twisted one on the top of the other. Each wire is

covered by a unique colour coded plastic sheath, which allows wires to be distinguishedfrom one another. All of the wires are then encapsulated in a plastic sheath.The maximum

distance that twisted pair cables can carry signal effectively is upto 100 meters.


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There are two types of twisted pair cables

Shielded Twisted Pair (STP) Cable: STP cabling includes metal

shielding over each individual pair of copper wires. This type of shielding protects cable from external EMI (electromagnetic interference). Thesecables are often used for Token ring networks.

Unsheilded Twisted Pair (UTP) Cable: UTP cables as the nameindicates are unshielded and lack an additional metal shielding. Based on

the number of twists per inch UTP cables are catetogorised into differentcategories.

Categories of Unshielded Twisted Pair

Type Transfer Rate Use

Category 1 1 Mbps (Voice) Telephone Wire

Category 2 4 Mbps (Data) Local Talk

Category 3 10 Mbps (Data) Ethernet

Category 4 16 Mbps (Data) Token Ring

Category 5 100 Mbps (Data) Fast Ethernet

Category 5e 1000 Mbps (Data) Gigabit Ethernet


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Connectors used for Twisted pair cables: RJ 11 and RJ 45 are theconnectors used for twisted pair cables.RJ, stands for Registerd Jack implying that theconnector follows a standard borrowed from the telephone industry. RJ 11 for four wire

telephone cable and RJ 45 for eight wire network cables.

RJ 11 and RJ 45

Wiring Scheme

CAT 5 UTP cabling usually uses only four wires when sending andreceiving information on the network. The four wires of the eigth that are used are wires

1, 2, 3 and 6.When you configure the wire for the same pin at either end of the cable, this is

known as a straight through cable. This type of cable is used for connecting dissimilardevices. For example, computer and a standard port in a switch.

When you switch wires 1 and 2 with wires 3 and 6 at one end then that type of

cable is called as crossover cable. This type of cable is used for connecting similardevices. For example, connecting two computers directly.

Fibre Optic Cables: Fibre Optic cables use optical fibres that carry digital data

signals in the form of modulated pulses of light. An optical fibre consists of an extremelythin cylinder of glass, called the core, surrounded by a concentric layer of glass known as

the cladding. There are two fibres per cable one to transmit and one to receive. The corealso can be an optical quality clear plastic, and the cladding can be made up of a gel that


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Straight Through & Cross Over Cable Pinouts

reflects signals back into the fibre to reduce signal loss. This type of cable can

carry signal upto and beyond 2 Kilometers at a high speed of 1+ Gbps.

Fiber Optic

There are two types of fibre optic cables: single mode fibre and multimode fibre.

Single mode fibre uses a single ray of light to carry the transmission over long distances.

Multimode fibre uses multiple rays of light simultaneously with each ray of light runningat a different reflection angle to carry the transmission over short distances.

Connectors used for fibre optic cables are Straight Tip (ST) and Subscriber Connector(SC).

Fibre optic cables are by far the expensive of these cabling methods, and are not

desirable for small networks.


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Wireless Media

Wirless media makes use of the atmosphere, hence referred to as unbound medium a

circuit with no formal boundaries. This types of medium doesnot use any physicalconnectors between the two devices that are communicating. Transmissions of waves

take place in the electromagnetic (EM) spectrum. The carrier frequency of the data isexpressed in cycles per second called hertz (Hz). The three broad categories of wireless

media are:

Radio Waves 10 KHz to 1 GHz. The Federal communicationsCommission (FCC) regulates the assignment of these frequencies.

Frequencies for unregulated use are:

902 928 MHz

2.4 GHz

5.72 5.85 GHz

Microwave Used to link networks over long distances but the twomicrowave towers must have a line of sight between them. The frequency

is usually 4 6 GHz or 21 23 GHz. Speed is often 1 10 Mbps. The signalis normally encrypted for privacy.

Infrared Infrared is just below the visible range of light between 100GHz and 1000 THz. A light emitting diode (LED) or laser is used to

transmit the signal. The signal cannot travel through objects and line ofsight is a must.

Media Access Methods

An access method determines how nodes on a network, place the data/packet on the

media. There are three different types of LAN access methods CSMA/CD, CSMA/CA,Token Passing.

Carrier Sense Multiple Access Collision Detection (CSMA/CD) is the protocol used in

Ethernet networks (IEEE 802.3) to ensure that only one network node is transmitting onthe network media at a time. With CSMA/CD, every host has equal access to the media if

a host wishes to transmit the data, it will sense the media (Carrier Sense) and determine
http://www.tech-faq.com/csma-cd.shtml


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whether there is a signal already on the wire if there is, the host will wait to transmit thedata if not it transmits the data immediately. The problem with this process is that, if

there are two systems on the media that sense the media at the same time to see if the

media is free, they will both send the data out at the same time (Multiple Access) leadingto collision which generates a high voltage jam signal making all the hosts in the mediastop sending the data for a random time interval before resending the data frame thereby

preventing a collision the second time (Collision Detection).

Collision

Carrier Sense Multiple Access Collision Avoidance (CSMA/CA) is a network

contention protocol used popularly in Wireless networks (IEEE 802.11) which attemptsto prevent collisions before they happen. With CSMA/CA, before a host sends data on

the media it will sense the media to see if the wire is free of signals once the channel isclear, a station sends a signal telling all other stations not to transmit, and then sends the

packet.

Token Passing is a LAN access method where a "token" is passed around the nodes in around robin fashion that authorizes the node to communicate. Here only the systemwhich has the "token" can communicate. The token is a control mechanism which gives

authority to the system to communicate or use the resources of that network. Once thecommunication is over, the token is passed to the next candidate in a sequential manner.

For example, if Workstation 1 wants to send data on the wire, it would wait for the token,which is circling in the network millions of times per second. Once the token has reached

the Workstation 1, it would take the token off the network, pakage it with data and labelit with the source address and destination address and passess it on to the next


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CSMA/CA

workstation in the network. All systems will look at the token, but will not process it

since it is not destined for them. However, the system that is the intended destination willtake the data and pass the empty token to the next computer in the sequence. This access

method is deployed in Token ring networks (IEEE 802.5).

LAN Technologies

Each computer in a LAN can effectively send and receive any information

addressed to it. This information is in the form of data 'packets'. The standards followed


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to regularize the transmission of packets, are called LAN standards. There are many LANstandards such as Ethernet, Token Ring and FDDI. Usually LAN standards differ due to

their media access technology and the physical transmission medium.

Ethernet

This is the most popular network architecture for local are networks (LAN). Ethernet uses

Carrier Sense Multiple Access with Collision Detection (CSMA/CD) protocol to controlaccess to network. Ethernet specifications define the function that occur at the physical

and data link layer of the OSI reference model and package data into frames fortransmission on the wire. It is available in three speeds:

10 Mbps which is called Ethernet IEEE 802.3100 Mbps which is Fast Ethernet IEEE802.3u

1000 Mbps or 1 Gbps which is called Gigabit Ethernet IEEE802.3ab

Token Ring (IEEE 802.5)

Token ring is a LAN technology that was developed by IBM. This is a 4 Mbps or 16

Mbps token passing method, operating in a ring topology. Devices on a Token Ringnetwork get access to the media through token passing.

FDDI (Fiber Distributed Data Interface)

Its a high speed networking technology used mainly for campus backbones. FDDI

provides data speed at 100Mbps which is faster than Token Ring and Ethernet LANs.FDDI comprise two independent, counter rotating rings: a primary ring and a secondary

ring. Data flows in opposite directions on the rings. The counter rotating ring architecture prevents data loss in the event of a link failure, a node failure, or the failure of both the

primary and secondary links between any two nodes. This technology is usuallyimplemented for a backbone network.


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References

Network+ Gene E. Clarke

Networking Essentials John Nash

Encyclopedia of Networking Mitch Tulloch and Ingrid TullochCCNA Study Guide Todd Lammlewww.microsoft.com/technet

www.firewall.cx

Review

Network refers to the interconnection of computers or networking devices for thepurpose of file sharing and resource sharing.

Networks can be classified based on geographical distance as LAN, MAN andWAN based on functional relationship as peer peer and client server based on

topology as bus, star, ring, mesh and hybrid networks. Transmission media provides the path for one computer to transfer information to

another. This can either be a wired or a wireless medium. Wired mdium usescables copper cables or fibre optic, whereas the wireless uses Radio waves or

infrared or microwave radiation in order to send and receive data. Media access methods: CSMA/CD (IEEE 802.3), CSMA/CA (IEEE 802.11) and

Token Passing (IEEE 802.5). LAN access methods: Ethernet, Token Ring and FDDI.

Review Questions

1. A company has offices in Chennai and Bangalore. Both networks are connected

to allow the two locations to communicate. This is considered as what type ofnetwork?

a. LAN b. CAN

c. MANd. WAN

2. Which network topology requires the use of terminators?

3. The distance limitation of 10 Base 2 is _________ meters.
http://www.firewall.cx/http://www.microsoft.com/technet


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4. ____________ cable sends the signal as pulses of light through a glass core?

5. Which network architecture is defined as the IEEE 802.3 standard?

6. Name the connectors used for connecting twisted pair cables?

7. What type of cable is used for connecting a computer with another computer?

8. Explain how nodes in an Ethernet network detect collision?

9. What are the radio frequencies that are preferred for wireless transmission?

10. Hub and Switch are devices that work in __________ topology.


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LAB

1. From the given cables identify the following and also note down your observation

in the form of a diagram.

a. Straight Through Cable

b. Cross Over Cable

c. Telephone cable

d. Coaxial Cable


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2. From the given connectors identify the following and note down your observationin form of a diagram. Also mention the type of cable for which it ca be used.

a. RJ 11

b. RJ 45

c. BNC

d. AUI

ELO (Expected Learning Outcome)

Network and its importance.

Different ways of classifying networks.

Basic understanding of the different network topologies. Know and appreciate the different types of media, along with their

advantages, disadvantages and their connectors. In depth understanding of the different media access methods, like,

CSMA/CD, CSMA/CA and Token Passing. Awareness about the different LAN technologies.

study material for networking essentials

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