Data Communication Tranmission Media Notes IMS DAVV Nir

8/3/2019 Data Communication Tranmission Media Notes IMS DAVV Nir

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Notes : Computer Communication IMS-DAVVFaculty : Niranjan shrivastava

What is Computer Network :A network consists of two or more computers that are linked in order to shareresources (such as printers and CD-ROMs), exchange files, or allow electroniccommunications.The computers on a network may be linked through cables, telephone lines,

radio waves, satellites, or infrared light beams.

Why we are using computer networkComputer on its own is referred to as a stand-alone machine, and mostdomestic computer users use their PCs in this way. However even smallcommercial organizations may want to link their computers together. Twocomputers linked together so that they can exchange data form a network.

However when we think of networks, we tend to think of lots of machineslinked together.

Advantagesof linking machines ( Computer on Network or LAN)?

Sharing of resources such as scanners and printers; Common information can be shared.

Easier to install a program on a central computer rather than having to doit individually for each computer.

E-mails can be sent between users.

New users and equipment can be added easily.

Different types of computers can connect to each other.

Disadvantagesare:

If a file server goes down, the users cannot access programs. If the network is not operating properly, hardware and software sources

cannot be accessed.

The networks efficiency depends a lot on the skill of its manager. A poorlymanaged network (or one where the manager is obstructive) becomesfrustrating to use and may be less efficient than stand-alone machines.

Hard to keep secure from hackers. If a network is not well designed, it might not able to manage the network

traffic and performance of network going down ( Slow Network for accessdata ).

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Computer Network TechnologyServer :Server provide services to client. Like internet Server , Mail Server ,Database server, application .

Client :Who get services from server or request services from other computersystems

Client /Server technology Nodes and servers share data roles Nodes are called clients Servers are used to control access Database software Access to data controlled by server

Server is the most important computer

Peer to Peer Technology

All nodes are equal Nodes access resources on other nodes Each node controls its own resources

Distributing computing

How can computers communicate?Actually in quite a similar way to humansThe Hardware (the physical components of the network

Transmitter ( Vocal Cords in humans) Channel (Media) [ Air in humans] Receiver [Ear in humans]

TransceiverTopology

How is the network connected

Protocols

What rules does the network follow to facilitate communication

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Type of Computer Network

Local Area Network - A Local Area Network (LAN) is a network that is confinedto a relatively small area. It is generally limited to a geographic area such as awriting lab, school, or building.

LAN computers more than a mile apart. In a typical LAN configuration, onecomputer is designated as the file server. It stores all of the software that controlsthe network, as well as the software that can be shared by the computersattached to the network.Computers connected to the file server are called workstations.The workstations can be less powerful than the file server, and they may haveadditional software on their hard drives.LANs, cables are used to connect the network interface cards in each computer.

Benefits of LANs: Sharing of hardware resources.

Sharing of software and data. Consolidated wiring/cabling. Simultaneous distribution of information. More efficient person-to-person communication

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MAN (Metropolitan Area Network)A communications network that covers a geographic area such as a cityor suburb.

Consists of many local area networks linked together. Span the distance of just a few miles.

WAN (Wide Area Network) Consists of a number of computer networks including LANs. Connected by many types of links.

Wide Area Networks (WANs) connect larger geographic areas, such as Sirt,Libyaconnected to India or other part of the world. Satellite uplinks may be used toconnect this type of network.

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Network TopologyTopology refers to the way in which the network of computers is connected. Each

topology is suited to specific tasks and has its own advantages and disadvantages. The

choice of topology is dependent upon type and number of equipment being used, plannedapplications and rate of data transfer required, response time, and cost.

Topology can also be defined as the geometrically interconnection pattern by which thestations (nodes/computers) are connected using suitable transmission media

The Bus Topology In Bus Topology, all stations attach through appropriatehardware interfacing known as a tap, directly to a linear transmission medium

A continuous coaxial cable to which all the devices are attached. All nodes can detect all messages sent along the bus.

Key Characteristics of Bus Topology are:

o Flexible

o Expandable

o Moderate Reliability

o Moderate performance

BUS TOPOLOGY

The Ring Topology In the ring topology, the network consists of a set ofrepeaters joined by point-to-point links in a closed loop as shown in Fig. .

Nodes linked together to form a circle.

A message sent out from one node is passed along to each node inbetween until the target node receives the message.

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RING TOPOLOGY

The Star Topology In the star topology, each station is directly connected to acommon central node as shown in Fig.

Each node is linked to a central node. All messages are routed through the central node, who delivers it to the

proper node.

STAR TOPOLOGY

Key features of Star Topology :

High Speed Very Flexible High Reliability High Maintainability

The Tree Topology - (hierarchical Topology)

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Looks like an upside-down tree where end nodes are linked to interiornodes that allow linking through to another end node.

TREE TOPOLOGY

Mesh Topology (fully connected network) In this topology each node or stationis connected to every other station. All nodes are connected to all other nodes. as

shown in Fig.

MASH TOPOLOGY

The key characteristics of this topology are as follows:

Fully connected

Robust Highly reliable

Not flexible

Poor expandability

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Transmission MediaTransmission media can be defined as physical path between transmitter andreceiver in a data transmission system

Simplex

Unidirectional, one device transmitting at a time Half-duplex

Bi-directional, one device transmitting at a time Full duplex

Bi-directional, both devices can simultaneously transmit

The world of computer networks and data communications would not exist ifthere were no medium by which to transfer data.The two major categories of media include:

Conducted media Coaxial Cable

Twisted Pair Cable Fiber Optic Cable

Wireless media Terrestrial Microwave Satellite Microwave Mobile Telephone

Coaxial Cable : A single wire wrapped in a foam insulation surrounded by abraided metal shield, then covered in a plastic jacket. Cable can be thick or thin.Base band coaxial technology uses digital signaling in which the cable carries

only one channel of digital data.Broadband coaxial technology transmits analog signals and is capable ofsupporting multiple channels of data.

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Characteristics of Coaxial Cables

Two types Thin baseband and Think baseband Coaxial cables

1- UTP Category:Thin baseband single channel Typical Use: LANs

Signaling Technique: Digital Maximum Data Rate: 10 Mbps Maximum Range: 100 meters (328 feets) Advantages:

Low noise Disadvantages:

Insecure

2 UTP Category:Thick broadband multi channel Typical Use:

LANs Cable TV Long distance telephone

Signaling Technique: Analog Maximum Data Rate: 10 Mbps Maximum Range: 2-3 miles Advantages:

Low noise Multiple channels

Disadvantages: Insecure

Twisted Pair : In twisted pair technology, two copper wires are strungbetween two points:

Figure CAT5 cable (twisted cable)

In twisted pair technology, two copper wires are strung between two pointsTwo or more pairs of single conductor wires that have been twisted around eachother.Twisted pair wire is classified by category. Twisted pair wire is currentlyCategory 1 (CAT1) through Category 7 (CAT7).Twisting the wires helps to eliminate electromagnetic interference between thetwo wires.

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Shielding can further help to eliminate interference.

Characteristics of Twisted Pair Cables1 - UTP Category:Category 1 (CAT1)

Typical Use: Telephone wire Signaling Technique: Analog and Digital Maximum Data Rate: < 100 Kbps Maximum Range: 3-4 miles Advantages:

Inexpensive Easy to install and interface Widely used

Disadvantages: Insecure Noise

2 - UTP Category:Category 2 (CAT2) Typical Use: T1, ISDN Signaling Technique: Digital Maximum Data Rate: < 2 Mbps Maximum Range: 3-4 miles Advantages:


Disadvantages:

Insecure Noise

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3 - UTP Category:Category 3 (CAT3) Typical Use: LANs Signaling Technique: Digital Maximum Data Rate: 10 Mbps Maximum Range: 100 meters (328 feet)

Advantages: Inexpensive Easy to install and interface Widely used


4- UTP Category:Category 4 (CAT4) Typical Use: LANs Signaling Technique: Digital

Maximum Data Rate: 20 Mbps Maximum Range: 100 meters (328 feet) Advantages:



5- UTP Category:Category 5 (CAT5) Typical Use: LANs Signaling Technique: Digital Maximum Data Rate: 100 Mbps Maximum Range: 100 meters (328 feet) Advantages:



6- UTP Category:Category 6 (CAT6) Typical Use: LANs Signaling Technique: Digital Maximum Data Rate: 200 Mbps Maximum Range: 100 meters (328 feet) Advantages:

Draft standard in early stages

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7- UTP Category:Category 7 (CAT7) Typical Use: LANs Signaling Technique: Digital Maximum Data Rate: 600 Mbps Maximum Range: 100 meters (328 feet)

Advantages: Draft standard in very early stages

Twisted Pair Cable

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Fiber Optic CableA thin glass cable approximately a little thicker than a human hair surrounded bya plastic coating and packaged into an insulated cable.A photo diode or laser generates pulses of light which travel down the fiber opticcable and are received by a photo receptor.

Core Multimode 50 m

Singlemode 812 m

Cladding

Core Multimode 50 m

Singlemode 812 m

Cladding

In fiber optic technology, the medium consists of a hair-width strand of silicon orglass, and the signal consists of pulses of light. For instance, a pulse of lightmeans ``1'', lack of pulse means ``0''. It has a cylindrical shape and consists of

three concentric sections: the core, the cladding, and thejacketas shown inFigure .

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Characteristics of Fiber Optic CableUTP Category:Fiber Optic

Typical Use: LANs Data

Video Audio WANs

Signaling Technique: Light pulses Maximum Data Rate: 10 Gbps Maximum Range: 100 miles Advantages:

Secure High capacity Very low noise

Disadvantages:

Expensive interface, but coming down in cost

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Wireless Media

Radio, satellite transmissions, and infrared light are all different forms ofelectromagnetic waves that are used to transmit data.Note in the following figure how each source occupies a different set of

frequencies

Microwave Tower Land-based, line-of-sight transmission Approximately 20-30 miles maximum between towers Transmits data at billions of bits per second (Gbps) Popular with telephone companies and business to business

transmissionsMicrowave signals commonly used for longer distances (10's of km). Sender andreceiver use some sort of dish antenna as shown in Fig.

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Figure Communication using Terrestrial Microwave Tower

Difficulties:1. Weather interferes with signals. For instance, clouds, rain, lightning, tc.

May adversely affect communication.

2. Radio transmissions easy to tap. A big concern for companies worriedabout competitors stealing plans.

3. Signals bouncing off of structures may lead to out-of-phase signals thatthe receiver must filter out.

Satellite Microwave

Satellite communication is based on ideas similar to those used for line-of-sight.A communication satellite is essentially a big microwave repeater or relay station

in the sky.Microwave signals from a ground station is picked up by a transponder, amplifiesthe signal and rebroadcasts it in another frequency, which can be received byground stations at long distances as shown in Fig. A

Figure A Satellite Microwave Communication: point to- point.

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Figure Satellite Microwave Communication: Broadcast links

Similar to terrestrial microwave except the signal travels from a ground station onearth to a satellite and back to another ground station.

Satellites can be classified by how far out into orbit each one is (LEO, MEO, andGEO).

LEO - Low Earth Orbit - 100 miles to 1000 miles. Used for pagers, wireless e-mail, special mobile telephones, spying, videoconferencing.MEO - Middle Earth Orbit - 1000 to 22,300 miles. Used for GPS andgovernment.GEO - Geosynchronous Orbit - 22,300 miles. Used for weather, television, andgovernment operations

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Mobile TelephoneWireless telephone service, such as cellular telephone, cell phone. To support multiple

users in a metropolitan area (market), the market is broken into cells. Each cell has its

own transmission tower and set of assignable channels.

Media Selection Criteria Cost Speed Distance and expandability Environment Security

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What is a Switch? A switch is a network device that selects a path or circuit for sending aunit of data to its next destination a network traffic monitoring device that controls the flow of trafficbetween multiple network nodes

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Data Communication Tranmission Media Notes IMS DAVV Nir