Network Hardware

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Network HardwareNetwork Hardware

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Types of Network TopologiesTypes of Network Topologies

BusBus

StarStar

RingRing

MeshMesh

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Bus TopologyBus Topology

1. A Bus Topology Network uses a long cable , called the BACKBONE

2. PC’s are connected to the BACKBONE with Small Cables ( called

DROP Cables ) using T-Connectors & BNC connectors .

3. To avoid Signal- Bouncing , the backbone is “Terminated” both ends

4. BUS is a Passive Topology as there are no Active electronics to

amplify the signal in this type of Network

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Bus TopologyBus Topology

1. Ethernet 10Base2 is a common BUS topology Network ( Thinnet )

Ethernet 10Base5 is known as Thicknet .

2. Cables used are Thick & Thin Co-Axial cable

3. Segment length is 185 metres for Thin Co-axial Cable ( RG-58 )&

500 metres for Thick Co-Axial Cable ( RG-11 )

4. Bandwidth is 10 MBPS

5. To increase the segment length REPEATERS are used .

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Advantages of BUS TopologyAdvantages of BUS Topology

1. The bus is simple, reliable in very small networks, easy to use & install , and easy to understand.

2. The bus requires the least amount of cable to connect the computers together and is therefore less expensive than other cabling arrangements.

3. It is easy to extend a bus. Two cables can be joined into one longer cable with a BNC barrel connector, making a longer cable and allowing more computers to join the network.

4. A repeater can also be used to extend a bus; a repeater boosts the signal and allows it to travel a longer distance.

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Disadvantages of BUS TopologyDisadvantages of BUS Topology

1. If there is any breakage in the BUS the whole network is down .

2. It is difficult to troubleshoot a bus. A cable break or malfunctioning computer anywhere between two computers can cause them not to be able to communicate with each other. A cable break or loose connector will also cause reflections and bring down the whole network, causing all network activity to stop.

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Star TopologyStar Topology

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In a star topology, all the cables run from the computers to a central location, where they are all connected by a device called a hub.

Stars are used in concentrated networks, where the endpoints are directly reachable from a central location; when network expansion is expected; and when the greater reliability of a star topology is needed.

Star TopologyStar Topology

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How a Star Network WorksHow a Star Network Works

Each computer on a star network communicates with a central hub that resends the message either to all the computers (in a broadcast star network) or only to the destination computer (in a switched star network).

An active hub regenerates the electrical signal and sends it to all the computers connected to it. This type of hub is often called a multiport repeater. Active hubs and switches require electrical power to run.

Ethernet 10baseT is a popular network based on the

star topology.

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Advantages of STAR TopologyAdvantages of STAR Topology

It is easy to modify and add new computers to a star network without disturbing the rest of the network.

Provides centralized monitoring and management of the network.

Single computer failures do not necessarily bring down the whole star Network.

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Disadvantages of STAR TopologyDisadvantages of STAR Topology

If the central hub fails, the whole network fails to operate.

It costs more to cable a star network because all network cables must be pulled to one central point, requiring more cable than other networking topologies.

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RING TopologyRING Topology

In a ring topology, each computer is connected to the next computer, with the last one connected to the first.

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How a Ring Network WorksHow a Ring Network Works

1. No terminators read.

2. Signals travels around the loop in one direction and passes through each computer .

3. It is an Active topology , because , each PC acts as a repeater to boost the signal to the next PC.

4. Because the signal passes through each PC , the failure of one PC can impact the entire network .

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5. One method of Transmitting data around the Ring is called Token passing.

6. The sending PC modifies the Token by putting electronic address on the data and sends it around the Ring .

7. The data passes through each PC until it finds the actual destination address PC that is encoded with the data .

8.The receiving PC returns a message to the sending PC indicating the receipt of data . After the acknowledgement is recd by the sending PC , it creates a new token and releases it on the network .

FDDI is a fast fiber-optic network based on the ring topology.

How a Ring Network Works (Cont.)How a Ring Network Works (Cont.)

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Advantages of RING TopologyAdvantages of RING Topology

Because every computer is given equal access to the token, no one computer can monopolize the network.

The fair sharing of the network allows the network to degrade gracefully (continue to function in a useful, if slower, manner rather than fail once capacity is exceeded) as more users are added.

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Failure of one computer on the ring can affect the whole network.

It is difficult to troubleshoot a ring network.

Adding or removing computers disrupts the network.

Advantages of RING TopologyAdvantages of RING Topology

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Mesh TopologyMesh Topology

4+3+2+1 = 10 concatenations

For 5 devices -------a Advantage :

1. Extremely fault tolerant

Disadvantage:

1. Very Complex to install & troubleshoot

2. High Cabling cost.

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Considerations When Choosing aTopology:

Money. A linear bus network may be the least expensive way to

install a network; you do not have to purchase concentrators.

Length of cable needed. The linear bus network uses shorter

lengths of cable.

Future growth. With a star topology, expanding a network is easily

done by adding another concentrator.

Cable type. The most common cable in schools is unshielded

twisted pair, which is most often used with star topologies.

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Summary Chart

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Network Media

Types of Network MediaTypes of Network Media

1. Cable Media

2. Wireless Media

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Cable Media:

1. Coaxial

2. Twisted Pair

3. Fiber-optic

Wireless Media :

1. Radio frequency

2. Microwave

3. Infrared

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CO-AXIALCO-AXIAL

Co-axial Cable (Commonly called “Coax”) is made of Two conductors that common axis , hence the name (“ co,” “axis” ). Typically the center of the cable is relatively stiff solid copper wire or stranded wire incased in insulating plastic foam . The foam is surrounded by the second conductor , a wire meshed tube ( Some include conductive foil wrap ), which serves as a shield from EMI. A tuff, insulating plastic tube forms the cover of the cable .

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1.Thin Ethernet

2.Thick Ethernet

3. Arc net

Types of Coaxial Cable:

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Parameters Thin Ethernet Thick Ethernet Arc net

Cable Code RG-58 RG-8,RG-11 RG-62

Terminator value 50 Ohm 50 Ohm 93 Ohm

Segment Length 185 Mts. 500 Mts. N / A

Connectors used BNC,T-connector AUI BNC

Data transmission rate 10 Mbps 10 Mbps 2.5 Mbps

Topology Bus Bus Star

Comparison between types of Co-axial CablesComparison between types of Co-axial Cables

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2. Twisted Pair2. Twisted Pair

Twisted pair cable uses one or more pairs of two twisted Copper wires. The twists in twisted - pair cable decrease cross talk because radiated signals from the twisted wires tend to cancel each other out.

Types of twisted-pair cables:

1. UTP

2. STP

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1. UTP (Unshielded twisted pair)

2. UTP cable consists of four pairs of twisted solid copper wires. All four pairs are colour coded and is encased in a plastic outer casing.

Normally category 3 and 5 (commonly known as CAT-3 & CAT-5) are used for computer networks . CAT-3 is meant for data transmission rate of 10 Mbps whereas CAT-5 is meant for upto 100 Mbps.

Connectors used is RJ – 45.

Topology is Physical STAR- Logical BUS

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Categories of Unshielded Twisted Pair

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2. STP (Shielded twisted pair)

STP has two pairs of color coded conductors

wrapped in a foil shielding above this shielding a

plastic encasement is provided.

STP cables are made for upto 155 Mbps data

transmission rate.

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3. Fiber optic 3. Fiber optic

Fiber optic cable is made of light-conducting glass or plastic core surrounded by more glass called Cladding, and a tuff outer sheet . The centre core provides the light path or wave-guide while the cladding is composed of varying layers of reflective glass. The Glass cladding is designed to refract light back in to the core. Each core and cladding strand is surrounded by a tight or loose sheath . Current fiber optic technologies allow data rates from 100 Mbps to 2 Gbps. Connectors used is ST connectors

Two types of fiber optic cables are available

1. Single-mode fiber ( Segment length = 40 Kms.)

2. Multi-mode fiber ( Segment length = 2 Kms.)

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SMF (Single-mode Fiber)

Narrow core through which laser-generated light travels over one path, reflecting very little

Accommodates high bandwidths and long distances

Expensive

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MMF (Multimode Fiber)

Benefits over copper cabling:

Nearly unlimited throughput

Very high resistance to noise

Excellent security

Ability to carry signals for much longer distances before

requiring repeaters than copper cable

Industry standard for high-speed networking

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MMF (continued)

Throughput: transmission rates exceed 10 Gigabits per

second

Cost: most expensive transmission medium

Connector: 10 different types of connectors

Typically use ST or SC connectors

Noise immunity: unaffected by EMI

Size and scalability: segment lengths vary from

150 to 40,000 meters

Optical loss: degradation of light signal after it travels a

certain distance away from its source

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Cable Design and Management

Cable plant: hardware making up enterprise-wide cabling

system

Structured cabling: TIA/EIA’s 568 Commercial Building

Wiring Standard

Entrance facilities point where building’s internal cabling

plant begins

Demarcation point: division between service carrier’s

network and internal network

Backbone wiring: interconnection between

telecommunications closets, equipment rooms, and

entrance facilities

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Cable Design and Management (continued)

Structured cabling (continued): Equipment room: location of significant networking

hardware, such as servers and mainframe hosts

Telecommunications closet: contains connectivity for groups of workstations in area, plus cross connections to equipment rooms

Horizontal wiring: wiring connecting workstations to closest telecommunications closet

Work area: encompasses all patch cables and horizontal wiring necessary to connect workstations, printers, and other network devices from NICs to telecommunications closet

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Installing Cable

Many network problems can be traced to poor cable installation

techniques

Two methods of inserting UTP twisted pairs into RJ-45 plugs:

TIA/EIA 568A and TIA/EIA 568B

Straight-through cable allows signals to pass “straight through”

between terminations

Crossover cable: termination locations of transmit and receive wires

on one end of cable reversed

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Wireless Transmission

Networks that transmit signals through the atmosphere via

infrared or RF waves are known as wireless networks or

wireless LANs (WLANs)

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The Wireless Spectrum

Figure : The wireless spectrum

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Characteristics of Wireless Transmission

Figure : Wireless transmission and reception

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Antennas

Radiation pattern describes relative strength over three-

dimensional area of all electromagnetic energy the antenna

sends or receives

Directional antenna issues wireless signals along a single

direction

Omnidirectional antenna issues and receives wireless

signals with equal strength and clarity in all directions

Range: geographical area an antenna or wireless system

can reach

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Signal Propagation

Figure : Multipath signal propagation

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Signal Degradation

Fading: change in signal strength resulting from

electromagnetic energy being scattered, reflected, or

diffracted after being issued by transmitter

Wireless signals experience attenuation

May be amplified and repeated

Interference is significant problem for wireless

communications

Atmosphere saturated with electromagnetic waves

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Narrowband, Broadband, and Spread Spectrum Signals

Narrowband: transmitter concentrates signal energy at

single frequency or in very small range of frequencies

Broadband: uses relatively wide band of wireless spectrum

Offers higher throughputs

Spread spectrum: use of multiple frequencies to transmit a

signal

Frequency hopping spread spectrum (FHSS)

Direct sequence spread spectrum (DSSS)

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Fixed versus Mobile

Fixed wireless system: locations of transmitter and receiver

do not move

Point-to-point link

Efficient use of signal energy

Mobile wireless system: receiver can be located anywhere

within transmitter’s range

More flexible

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Infrared Transmission

Transmitted by frequencies in the 300-GHz to 300,000-GHz

range

Most often used for communications between devices in

same room

Relies on the devices being close to each other

May require line-of-sight path

Throughput rivals fiber-optics

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Wireless LAN (WLAN) Architecture

Figure : An ad-hoc WLAN

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Wireless LAN Architecture (continued)

Figure : An infrastructure WLAN

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Wireless LAN Architecture (continued)

Figure : Wireless LAN interconnection

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NETWORK COMPONENTS OVERVIEW

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Fundamentals of LAN

• Typically Ethernet based• Star topology oriented• UTP (twisted pair) and fiber media• Conforms to IEEE 802.3 standard• Works at 10, 100, 1024 Mbps• Reduced throughput as the nodes

increase (Collision)

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IEEE Standards

An association that promotes engineering and electronic

improvement

IEEE 802 was started in February 1980

IEEE 802 committee defines frames, speed, distances and types of

cabling to use for networking

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Protocols and Procedures

Protocols are set of rules which are used by the nodes on a network to

communicate with each other

Protocols are developed by committees, different companies developed products

confirming to those protocols

Standard Protocols

Ethernet Token Ring ARCnet

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LAN Architecture - I

802.3

Defines a standard for physical layer and data link layer of the Ethernet

architecture that uses wired connection

Ethernet is an architecture that mainly uses bus topology

Defines various cabling used for different types of topologies

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LAN Architecture - II

802.4

Defines a standard for Token Bus architecture

Token bus is similar to token ring, but it uses coaxial cables

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LAN Architecture - III

802.5

Defines a standard for Token ring architecture

Uses the 10 Base T cabling standard

Uses twisted pair cabling to connect devices instead of coaxial cable

Passes data from one computer to another like in a token bus network

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IEEE 802.3 Logical relationship with OSI Reference Model

IEEE 802.3 physical layer

corresponds to the OSI physical

layer

OSI data link layer is divided into two

IEEE 802 sublayers

The Media Access Control

(MAC) sublayer

The MAC-client sublayer

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Ethernet

Defined by IEEE as the 802.3 standard

Most widely adapted LAN technology

Supports data transfer rates of 10 Mbps, 100 Mbps and 1 Gbps

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Introduction to Ethernet

Three data rates currently defined for the operation over optical fiber and

twisted-pair cables

10 Mbps – 10Base-T Ethernet

100 Mbps - Fast Ethernet

1000 Mbps - Gigabit Ethernet

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Working of Ethernet

Ethernet frame is used to transfer data over a network

Each device in an Ethernet network is uniquely identified by a 48 bit

(6 bytes) address called Ethernet address

Ethernet addresses are represented as six pairs of hexadecimal

digits separated by a colon.

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Elements of Ethernet System

Elements of Ethernet System

MediumSet of Medium Access

Control RulesEthernet frame

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Ethernet Medium

Transmits information over the network

Computer D transmits information for

Printer C

Computer B and A also receives the

information

All device inspects the destination

address

If the received frame is not meant for

them, they will reject the frame

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Data Transmission

When a computer wants to transmit, it listens to the cable

(transmission medium)

If two or more devices simultaneously transmit data on an idle

cable, collision may occur

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Example of Collision

Each device decides to broadcast

an Ethernet frame to other device

Devices listens to the Ethernet

medium and detects that no

carrier is present

Devices transmit simultaneously,

causing a collision

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Carrier Sense Multiple Access/ Collision Detection (CSMA/CD)

Permits one device to access to the network media at a time to

avoid collision

Networks using CSMA/CD technology such as Ethernet, network

devices compete for the network media

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Working of CSMA/CD

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Carrier Sensing Multiple Access / Collision Avoidance (CSMA/CA)

Set of rules that can avoid collisions, unlike CSMA/CD that handles network

transmissions once collisions are detected

In CSMA/CA, all devices are forced to wait for a random number of time

slots and sense the medium again

If the medium is sensed to be busy, the device stops the timer until it

becomes free again.

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Token Ring - I

Token Ring is a network architecture developed by IBM

Also known as IEEE 802.5

Uses logical ring topology

Multiple MAUs can be connected to extend the ring

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Token Ring - II

Data transfer is facilitated with the help of token passing mechanism

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Token Ring - III

Speed is either 4 or 16 Mbps Performance is significantly faster than Ethernet networks Uses physical star topology Hides logical ring inside a hub, known as Multistation Access Unit (MAU) Unshielded Twisted Pair (UTP) or Shielded Twisted Pair (STP) cables are

used connect nodes to the hub

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Token Ring - IV

Advantages:

Data collision does not occur

Every station is allowed to

transmit data

Time required to carry the

amount of data can be

calculated

Minimum cable requirement

Disadvantages:

System collapses if links

between nodes are

malfunctioning

No alternative link to transmit the

data

Data transmission is through

single direction

Performance degrades when

junk data is transmitted

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Token Ring Vs Ethernet

Token Ring Ethernet

Token Ring network uses token passing

mechanism.

Ethernet network use CSMA/CD mechanism.

Physical star topology is used. Any topology can be used as physical

topology.

Defined by IEEE 802.5 standard. Defined by IEEE 802.3 standard.

Devices in token ring may transmit only at

specific time.

Devices can transmit as soon as the medium is

free.

Support heavy network traffic and maintains

the network performance.

The performance of the Ethernet network

degrades as network traffic increases.

Token Ring network is deterministic. Ethernet network is not deterministic as token

ring.

Token ring network provides bandwidth

efficiency up to 90%.

Ethernet network provides bandwidth

efficiency up to 40%.

The network setup and maintenance of token

ring is expensive than Ethernet.

The cost of network equipment is lower for

Ethernet.

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Types of Ethernet

Cabling Standards

10Base5 10Base2 10Base-T 10Base-F

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10Base-5

Thick coaxial cable is also referred to as thicknet 10Base5 refers to specifications of thick coaxial cable carrying Ethernet

signals The 5 refers to the maximum segment length being 500 meters RG-8 coaxial cable is used A 15-pin female DB connector called AUI connector is used to connect the

device

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10Base-2

10Base-2 (thin coaxial cable) is also referred to as thinnet In 10Base-2, “2” refers to approximate maximum segment length of the

cable which is 185 meters 10Base2 uses RG-58 coaxial cable with BNC connectors

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10Base-T

Allows stations to be attached via twisted pair cable 10 refers to the transmission speed of 10 Mbps “T” refers to twisted pair cable In a 10BaseT network, each computer (node) is connected to a hub

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10 Base-F

Uses fiber optics

Possesses excellent noise immunity and is the method of choice when

running between buildings or widely separated hubs

10 Base-F is expensive as the connectors and terminators used in 10

Base-F are costly

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5-4-3 Rule - I

Developed to limit the size of an Ethernet collision domain. Implemented by Ethernet (IEEE 802.3) for number of repeaters and

segments on shared access The rule states that: Any two nodes in the network should not be separated

by more than 5 segments, 4 repeaters and 3 populated segments

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Network using 5-4-3 rule

5 – Specifies that maximum 5 segments can be used in the network 4 – Specifies the number of repeaters/concentrators used to connect the

network segments 3 – Specifies the number of populated segments

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Comparing Ethernet Types

Ethernet types 10Base5 10Base2 10BaseT 10BaseF

Media Type Thick coaxial

(RG8)

Thin coaxial

(RG58)

UTP Fiber-optic

Max.segment

length

(meters)

500 185 100 1000

Frequency(MHZ) 10 10 10 10

Max

Nodes/Segme

nt

100 30 1024 1024k

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Extending the network

A computer network can be extended using repeaters, hubs and bridges

In computer networks, a bridge is an Internetworking device

Repeater regenerates signal

Repeaters remove the unwanted noise in an incoming signal

A hub is a multi port repeater which provides a common point for the

connection of network devices

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Introduction to Advanced Ethernet

Ethernet is most widely used network technology

Introduced by IEEE 802.3

Ethernet systems are 10Base-T and 10Base-FL

High speed Ethernet includes

100Base Ethernet

Gigabit Ethernet

Switched Ethernet

Full Duplex Ethernet

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Features of Advanced Ethernet

Advanced Ethernet would use a physical star to match the robustness of

Token ring

It would not use more expensive coaxial cables and adopt inexpensive UTP

cabling

It would use the same frame types and speeds of the older Ethernets so

that new Ethernets will be compatible with older ones

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10BASE-T - I

Ethernet standard known as twisted pair Ethernet

Uses a star bus topology

Stations are connected to a hub using pairs of twisted cables

Features:

Failure of one system does not affect entire network

Easy troubleshooting

Addition and removal of device does not affect network

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10BASE-T Topology

It uses a physical star topology in which each node connects to a central hub The hub is a multiport repeater. It receives the signal from one port, regenerates

it and passes the signal to all the other ports

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Meaning of 10BASE-T

10 refer to 10 Mbps transmission speed, Base is for baseband signaling and

T stands for twisted pair cable

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10Base T Specifications and Limitations

Specifications include:

Fault Tolerant

Easy Troubleshooting

Easy Moves and Changes

Limitations include:

Distance

Sensitive to noise

Number of computers connected

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10BASE-FL

Ethernet standard that operates over fiber optic cable and covers a distance up

to 2 k.m.

Multimode fiber and Straight Tip (ST) connector are used to build 10Base-FL

segment

10Base FL components

Network MediumMedium Attachment

Unit (MAU)

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5-4-3 Rule - I

Developed to limit the size of an Ethernet collision domain. Implemented by Ethernet (IEEE 802.3) for number of repeaters and

segments on shared access The rule states that: Any two nodes in the network should not be separated

by more than 5 segments, 4 repeaters and 3 populated segments

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5-4-3 Rule - II

Categories of physical segments:

User segments used to connect the systems in the network. These

segments are also known as populated segments.

Link segments used to connect repeaters in the network. These segments

are also known as unpopulated segments.

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Network using 5-4-3 rule

5 – Specifies that maximum 5 segments can be used in the network 4 – Specifies the number of repeaters/concentrators used to connect the

network segments 3 – Specifies the number of populated segments

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High Speed Ethernet

Developed to increase connectivity speed between the terminals or computers in a network.

Ethernet Standards

Fast Ethernet(100Base Ethernet)

Gigabit Ethernet 10-Gigabit Ethernet

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100Base Ethernet

Supports data transfer rate up to 100 Mbps Also called as Fast Ethernet Makes use of CAT 5 cable and fiber cable

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Advantages and Disadvantages

Advantages Speed – Ten times faster than regular 10Base-T network Throughput – Faster for video, multimedia, graphics, Internet surfing and

other applications that require high speed Disadvantages Mode of data transfer – 100Base-T4 Ethernet cannot support full duplex

mode of data transfer Wiring – 100Base-T4 requires four pair of wiring for data transfer

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Gigabit Ethernet

Supports data transfer rate up to 1000 Mbit/s

Also called as 1000BASE-T Ethernet

Gigabit Ethernet

Standards

1000Base-SX 1000Base-LX 1000Base-CX 1000Base-T 1000Base-TX

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10-Gigabit Ethernet - I

Was developed by IEEE 802.3ae in 2002.

Supports data transfer rate that is ten times faster than Gigabit ethernet

Compatible with Synchronous Optical Network (SONET)

Supports segment length up to 40 Kms

Uses Media Access Control (MAC) protocol

Uses full-duplex mode of transmission and mostly run on fiber

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10-Gigabit Ethernet - II

Standards included:

10GBASE-CX4

10GBASE-T

10GBASE-SR (Short Range)

10GBASE-LRM (Long Reach Multimode)

10GBASE-LR (Long Range)

10GBASE-ER (Extended Range)

10GBASE-LX4

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Summary of Physical Layer Standard

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Summary of Physical Layer Standard (Contd)

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Switched Ethernet

Employs a switch instead of a repeater or an Ethernet hub to connect

individual hosts or segments

Uses three types of switching:

Cut-through

Store and forward

Fragment-free

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Basic Structure of Switched Ethernet

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Full-Duplex Ethernet

Devices at both ends can send and receive data at the same time

Provides twice the bandwidth of normal (half duplex) Ethernet

Each pairs of wires acts as a separate channel and allows the devices at

each end to communicate with one another in full duplex mode

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Case Study

The MoneyMaker bank has recently upgraded its Ethernet network from 10Base-T to 100Base-T network. It has also changed its cabling from CAT5 to CAT6 straight through cables and 10 Mbps NIC cards are replaced with 10/100 Mbps for future compatibility. After upgradation, some computers in the accounts department of the bank are facing the slower connectivity problems.

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Problem

Identifying problem related to cabling and crimping of RJ-45 jack for new CAT6 cables.

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Suggested Solution

Check the crimping of RJ-45 connector and configure the NIC to operate in 100 Base full duplex mode.

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Summary

Information can be transmitted via two methods: analog or digital

In multiplexing, the single medium is logically separated into multiple channels, or sub channels

Throughput is the amount of data that the medium can transmit during a given period of time

Baseband is a form of transmission in which digital signals are sent through direct current pulses applied to the wire

Noise is interference that distorts an analog or digital signal

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Summary (continued)

Analog and digital signals may suffer attenuation

Cable length contributes to latency, as does the presence

of any intervening connectivity device

Coaxial cable consists of a central copper core surrounded

by a plastic insulator, a braided metal shielding, and an

outer plastic cover (sheath)

Twisted-pair cable consists of color-coded pairs of

insulated copper wires

There are two types of twisted-pair cables: STP and UTP

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Summary (continued)

There are a number of Physical layer specifications for

Ethernet networks

Fiber-optic cable provides the benefits of very high

throughput, very high resistance to noise, and excellent

security

Fiber cable variations fall into two categories: single-mode

and multimode

Structured cabling is based on a hierarchical design that

divides cabling into six subsystems

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Summary (continued)

The best practice for installing cable is to follow the TIA/EIA

568 specifications and the manufacturer’s

recommendations

Wireless transmission requires an antenna connected to a

transceiver

Infrared transmission can be used for short-distance

transmissions

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THANK YOU