MCSE 514: Communication System and Networking

Computer Science and EngineeringIslamic University, Kushtia.

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Chapter Syllabus

Communication System: Band Width, Data transmission method, Data transmission mode,

Medium of data communication: Co-axial, Twisted pair, Optical fiber, Wireless, Radio wave, Microwave, Wireless communication System: Bluetooth, Wi-Fi, Wi-Max, Mobile communication, Concept and Objectives of Computer Networking, Functions of network,Types of network, Network topology, Network Devices, NIC, Cloud computing.

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Telecommunications Tele (Far) + Communications Early telecommunications

smoke signals and drums visual telegraphy (or semaphore in 1792)

Telegraph and telephone Telegraph (1839) Telephone (1876)

Radio and television Telephony

Voice and Data

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Communications and Networks Basic components

Communication technologies Communication devices Communication Channels

Physical medias Wireless

Communication software Networks of communication systems

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Communication Systems Process describing transfer of information, data,

instructions between one or more systems through some media Examples: people, computers, cell phones, etc. Computer communication systems

Signals passing through the communication channel can be Digital, or analog Analog signals: continuous electrical waves Digital signals: individual electrical pulses (bits)

Receivers and transmitters: desktop computers, mainframe computers, etc.

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Communication Technologies Different technologies allowing us to communicate

Voice mail, fax, email, instant message, chat rooms, news groups, telephony, GPS, and more

Voice mail: Similar to answering machine but digitized Fax: Sending hardcopy of text or photographs between

computers using fax modem Email: electronic mail – sending text, files, images

between different computer networks Must have email software More than 1.3 billion people send 244 billion messages

monthly!

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Communication Technologies Chat rooms: Allows communication in real time when

connected to the Internet voice chat, radio, etc.

Telephony: Talking to other people over the Internet (also called VoIP) Sends digitized audio signals over the Internet Requires Internet telephone software

Groupware: Software application allowing a group of people to communicate with each other (exchange data) A ddress book, appointment book, schedules, etc.

GPS: consists of receivers connected to satellite systems Determining the geographical location of the receiver Used for cars, advertising, hiking, tracking, etc.

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Simplified Communications Model - Diagram

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A Communications Model Source

generates data to be transmitted Transmitter

Converts data into transmittable signals Transmission System

Carries data Receiver

Converts received signal into data Destination

Takes incoming data

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Communication Devices Any type of hardware capable of transmitting data,

instructions, and information between devices Basic characteristics: How fast, how far, how much data! Functioning as receiver, transmitter, adaptor, converter Examples: Dial-up modems, ISDN, DSL modems, network

interface cards Dial-up modem: uses standard phone lines

Converts digital information into analog Consists of a modulator and a demodulator Can be external, internal, wireless Special applications: fax machine

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Communication Devices ISDN and DSL Modem: Allows digital communication

between networks and computers Requires a digital model Digital is better than analog – why?

Cable modem: a modem that transmits and receives data over the cable television (CATV) network Also called broadband modem (carrying multiple signals) The incoming signal is split Requires a cable modem

Network interface cards: Adaptor cards residing in the computer to transmit and receiver data over the network (NIC) Operate with different network technologies (Ethernet,

wireless)

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Communication Protocol (OSI)Application: Provides access to the OSI environment for users and also provides distributed information services.

Presentation: Provides independence to the application processes from differences in data representation (syntax).

Session: Provides the control structure for communication between applications; establishes, manages, and terminates connections (sessions) between cooperating applications.

Transport: Provides reliable, transparent transfer of data between end points; provides end-to-end error recovery and flow control.

Network: Provides upper layers with independence from the data transmission and switching technologies used to connect systems; responsible for establishing, maintaining, and terminating connections.

Data Link: Provides for the reliable transfer of information across the physical link; sends blocks of data (frames) with the necessary synchronization, error control, and flow control.

Physical: Concerned with transmission of unstructured bit stream over physical medium; deals with the mechanical, electrical, functional, and procedural characteristics to access the physical medium.

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Communication Protocol (TCP/IP)

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OSI~TCP/IP

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Communication Software Examples of applications (Layer 7) take advantage of the

transport (Layer 4) services of TCP and UDP Hypertext Transfer Protocol (HTTP): A client/server

application that uses TCP for transport to retrieve HTML pages.

Domain Name Service (DNS): A name-to-address translation application that uses both TCP and UDP transport.

Telnet: A virtual terminal application that uses TCP for transport.

File Transport Protocol (FTP): A file transfer application that uses TCP for transport.

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Communication Software Examples of applications (Layer 7) take advantage of the

transport (Layer 4) services of TCP and UDP Trivial File Transfer Protocol (TFTP): A file transfer

application that uses UDP for transport. Network Time Protocol (NTP): An application that

synchronizes time with a time source and uses UDP for transport.

Border Gateway Protocol (BGP): An exterior gateway routing protocol that uses TCP for transport. BGP is used to exchange routing information for the Internet and is the protocol used between service providers.

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Communication Channels A channel is a path between two communication devices Channel capacity: How much data can be passed through

the channel (bit/sec) Also called channel bandwidth The smaller the pipe the slower data transfer!

Consists of one or more transmission media Materials carrying the signal Two types:

Physical: wire cable Wireless: Air destination

network server

T1 lines

T1 lines

T1 lines

T3 lines

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Physical Transmission Media A tangible media

Examples: Twisted-pair cable, coaxial cable, Fiber-optics, etc.

Twisted-pair cable: One or more twisted wires bundled together Made of copper

Coax-Cable: Consists of single copper wire surrounded by three layers of

insulating and metal materials Typically used for cable TV

Fiber-optics: Strands of glass or plastic used to transmit light Very high capacity, low noise, small size, less suitable to

natural disturbances

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Physical Transmission Media

plastic outer coating

woven or braided metal

insulating material

copper wire

twisted-pair cable twisted-pair wire

protective coating

glass cladding

optical fiber core

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Wireless Transmission Media Broadcast Radio

Distribute signals through the air over long distance Uses an antenna Typically for stationary locations Can be short range

Cellular Radio A form of broadcast radio used for mobile communication High frequency radio waves to transmit voice or data Utilizes frequency-reuse

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Wireless Transmission Media

Microwaves Radio waves providing high speed transmission They are point-to-point (can’t be obstructed) Used for satellite communication

Infrared (IR) Wireless transmission media that sends signals

using infrared light-

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The bandwidth of a channel (medium) is defined to be the range of frequencies that the medium can support. Bandwidth is measured in Hz

With each transmission medium, there is a frequency range of electromagnetic waves that can be transmitted:

Twisted pair cable: 0 to 109 Hz (BW: 109 Hz) Coax cable: 0 to 1010 Hz (BW: 1010 Hz) Optical fiber: 1014 to 1016 Hz (BW: 1016 -1014 = 9.9x1015 Hz)

Optical fibers have the highest bandwidth (they can support electromagnetic waves with very high frequencies, such as light waves)

The bandwidth of the channel dictates the information carrying capacity of the channel

This is calculated using Shannon’s channel capacity formula

Channel Bandwidth:

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Shannon’s Theorem (Shannon’s Limit for Information Capacity) Claude Shannon at Bell Labs figured out how much information

a channel could theoretically carry:I = B log2 (1 + S/N) Where I is Information Capacity in bits per second (bps) B is the channel bandwidth in Hz S/N is Signal-to-Noise ratio (SNR: unitless…don’t make into

decibel: dB) Signal-to-noise ratio (often abbreviated SNR or S/N) is a

measure used in science and engineering that compares the level of a desired signal to the level of background noise. It is defined as the ratio of signal power to the noise power, often expressed in decibels.

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Transmission Media

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Twisted Pair Wires Consists of two insulated copper wires arranged in a regular

spiral pattern to minimize the electromagnetic interference between adjacent pairs

Often used at customer facilities and also over distances to carry voice as well as data communications

Low frequency transmission medium Types of Twisted Pair Wire

STP (shielded twisted pair) the pair is wrapped with metallic foil or braid to insulate

the pair from electromagnetic interference UTP (unshielded twisted pair)

each wire is insulated with plastic wrap, but the pair is encased in an outer covering

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Twisted-pair cable

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UTP connector

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Twisted Pair Advantages and LimitationsAdvantages Inexpensive and readily available Flexible and light weight Easy to work with and installLimitations Susceptibility to interference and noise Attenuation problem

For analog, repeaters needed every 5-6km For digital, repeaters needed every 2-3km

Relatively low bandwidth (3000Hz)

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Coaxial Cable (or Coax) Used for cable television, LANs, telephony Has an inner conductor surrounded by a braided mesh Both conductors share a common center axial, hence the term “co-

axial” Advantages

Higher bandwidth 400 to 600Mhz up to 10,800 voice conversations

Can be tapped easily (pros and cons) Much less susceptible to interference than twisted pair

Disadvantages High attenuation rate makes it expensive over long distance Bulky

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Coax Layers

copper or aluminum conductor

insulating material

shield(braided wire)

outer jacket(polyethylene)

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Coaxial cable

Categories of coaxial cables

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Fiber optics: Bending of light ray

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Fiber Optic Cable Relatively new transmission medium used by telephone

companies in place of long-distance trunk lines Also used by private companies in implementing local

data communications networks Require a light source with injection laser diode (ILD) or

light-emitting diodes (LED)

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plastic jacket glass or plasticcladding fiber core

Fiber Optic Layers

consists of three concentric sections

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Fiber Optic Advantages and DisadvantagesAdvantages greater capacity (bandwidth of up to 2 Gbps) smaller size and lighter weight lower attenuation immunity to environmental interference highly secure due to tap difficulty and lack of signal radiationDisadvantages expensive over short distance requires highly skilled installers adding additional nodes is difficult

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Optical fiber

Propagation modes

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Fiber Optic Types multimode step-index fiber

the reflective walls of the fiber move the light pulses to the receiver

multimode graded-index fiber acts to refract the light toward the center of the fiber by

variations in the density single mode fiber

the light is guided down the center of an extremely narrow core

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Modes

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Fiber construction

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UNGUIDED MEDIA: WIRELESS Unguided media transport electromagnetic waves without

using a physical conductor. Radio Waves Microwaves Infrared

transmission and reception are achieved by means of an antenna directional

transmitting antenna puts out focused beam transmitter and receiver must be aligned

omnidirectional signal spreads out in all directions can be received by many antennas

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Electromagnetic spectrum for wireless communication

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Bands

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Wireless transmission waves

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Wireless transmission wavesRadio radio is omnidirectional and microwave is directional Radio is a general term often used to encompass frequencies in

the range 3 kHz to 300 GHz. Mobile telephony occupies several frequency bands just under

1 GHz.Infrared Uses transmitters/receivers (transceivers) that modulate

noncoherent infrared light. Transceivers must be within line of sight of each other

(directly or via reflection ). Unlike microwaves, infrared does not penetrate walls.

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Wireless transmission waves

Radio waves are used for multicast communications, such as radio and television, and paging systems. They can penetrate through walls. Highly regulated. Use omni directional antennas

Microwaves are used for unicast communication such as cellular telephones, satellite networks, and wireless LANs. Higher frequency ranges cannot penetrate walls. Use directional antennas - point to point line of sight

communications. Infrared signals can be used for short-range communication in

a closed area using line-of-sight propagation.

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Terrestrial Microwave

used for long-distance telephone service uses radio frequency spectrum, from 2 to 40 Ghz parabolic dish transmitter, mounted high used by common carriers as well as private networks requires unobstructed line of sight between source and

receiver curvature of the earth requires stations (repeaters) ~30

miles apart

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dish dish

uplink station downlink station

satellitetransponder

22,300 miles

Satellite Transmission Process

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Satellite Transmission Process Satellite Microwave Transmission a microwave relay station in space can relay signals over long distances geostationary satellites

remain above the equator at a height of 22,300 miles (geosynchronous orbit)

travel around the earth in exactly the time the earth takes to rotate

Satellite Transmission Links earth stations communicate by sending signals to the satellite on

an uplink the satellite then repeats those signals on a downlink the broadcast nature of the downlink makes it attractive for

services such as the distribution of television programming

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Satellite MicrowaveSatellite Transmission Bands C band: 4(downlink) - 6(uplink) GHz

the first to be designated Ku band: 12(downlink) -14(uplink) GHz

rain interference is the major problem Ka band: 19(downlink) - 29(uplink) GHz

equipment needed to use the band is still very expensiveApplications Television distribution Long-distance telephone transmission Private business networksDisadvantages line of sight requirement expensive towers and repeaters subject to interference such as passing airplanes and rain

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Fiber vs Satellite

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Advantages of Wireless Communication Mobility: Because radio waves travel freely through the air, wireless

modes of communication give you a great deal of mobility. Convenience: Wireless devices have no cables to connect; if the signal has

sufficient strength, the device will work. This is also true for mobile computing devices; as long as user have the password for the local wireless data network, wireless devices connects automatically. When you leave a location, your mobile device automatically drops the connection and picks up the next strong network signal it finds.

Flexibility: A wired communications system is limited to the number of physical connections on the equipment; if these run out, user must replace the equipment to support more users. A typical Ethernet router for home use, for example, offers only eight sockets, even though its network software can handle 254 users.

Lower Cost: Wireless communications networks are less expensive to install and maintain than equivalent wired systems. Any changes to the wiring plan add to these costs. Although even wireless systems need some cabling, the amount involved is a small fraction of that needed for wired equipment.

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Simplified Data Communications Model

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Transmission Modes We use the term transmission mode to refer to the manner in

which data is sent over the underlying medium Transmission modes can be divided into two fundamental

categories: Serial — one bit is sent at a time

Serial transmission is further categorized according to timing of transmissions

Parallel — multiple bits are sent at the same time

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Taxonomy of Transmission Modes

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PARALLEL TRANSMISSION In parallel transmission, all the bits of data are transmitted

simultaneously on separate communication lines. Parallel transmission is used for short distance communication. In order to transmit n bit, n wires or lines are used. More costly. Faster than serial transmission. Data can be transmitted in less time.

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SERIAL TRANSMISSION In serial transmission , the various bits of data are transmitted

serially one after the other. It requires only one communication line rather than n lines to

transmit data from sender to receiver. Thus all the bits of data are transmitted on single lines in serial fashion. Less costly. Long distance transmission.

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SERIAL TRANSMISSION

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Timing of Serial Transmission Serial transmission mechanisms can be divided into three

broad categories (depending on how transmissions are spaced in time):

Asynchronous transmission can occur at any time with an arbitrary delay between the transmission of two

data items Synchronous transmission occurs continuously

with no gap between the transmission of two data items Isochronous transmission occurs at regular intervals

with a fixed gap between the transmission of two data items

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ASYNCHORONOUS TRANSMISSION Sends only one character at a time (one byte of data at a time) Synchronize two devices using Start Bit and Stop Bit. Start bit refers to the start of the data. Usually 0 is used for

start bit. Stop bit indicates the end of data.more than one bit can be

used for end.

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SYNCHRONOUS TRANSMISSION Data sent at one time multiple bytes. Start and stop bit not used. Gap between data units not present. Data transmission speed fast. Cost high. Transfer of data between two computer. Synchronization between sender and receiver required.

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SYNCHRONOUS TRANSMISSION

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Isochronous Transmission Isochronous transmission

is designed to provide steady bit flow for multimedia applications Delivering such data at a steady rate is essential

because variations in delay known as jitter can disrupt reception (cause pops or clicks in audio/make video freeze for a short time)

Isochronous network is designed to accept and send data at a fixed rate, R Network interface is such that data must be handed to the

network for transmission at exactly R bits per second For example, an isochronous mechanism designed to transfer voice

operates at a rate of 64,000 bits per second A sender must generate digitized audio continuously A receiver must be able to accept and play the stream

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TRANSMISSION MODE The term transmission mode defines the direction of the flow

of information between two communication devices i .e , It tells the direction of signal flow between the two devices.

1. SIMPLEX TRANSMISSION MODE.2. HALF DUPLEX TRANSMISSION MODE3. FULL DUPLEX TRANSMISSION MODE

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SIMPLEX MODE In simplex mode transmission information sent in only one

direction. Device connected in simplex mode is either sent only or

received only that is one device can only send, other device can only receive.

Communication is unidirectional.

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HALF DUPLEX

In half duplex transmission data can be sent in both the directions, but only in one direction at a time.

Both the connected device can transmit and receive but not simultaneously.

When one device is sending the other can only receive and vice-versa.

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FULL DUPLEX

In full duplex transmission, data can be sent in both the directions simultaneously.

Both the connected devices can transmit and receive at the same time.

Therefore it represents truly bi-directional system. In full duplex mode, signals going in either Direction share the full capacity of link.

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Unicast, Broadcast and Multicast Unicast: Unicast is the term used to describe communication

where a piece of information is sent from one point to another point. In this case there is just one sender, and one receiver

Broadcast: Broadcast is the term used to describe communication where a piece of information is sent from one point to all other points. In this case there is just one sender, but the information is sent to all connected receivers.

Multicast: Multicast is the term used to describe communication where a piece of information is sent from one or more points to a set of other points. In this case there is may be one or more senders, and the information is distributed to a set of receivers (theer may be no receivers, or any other number of receivers).

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Types of network Computer networks can be characterized by their size as well

as their purpose. The size of a network can be expressed by the geographic area

they occupy and the number of computers that are part of the network. Networks can cover anything from a handful of devices

within a single room to millions of devices spread across the entire globe.

Some of the different networks based on size are: Personal area network, or PAN Local area network, or LAN Metropolitan area network, or MAN Wide area network, or WAN

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Personal Area Network A personal area network, or PAN, is a computer network

organized around an individual person within a single building. This could be inside a small office or residence. A typical PAN would include one or more computers,

telephones, peripheral devices, video game consoles and other personal entertainment devices.

This type of network provides great flexibility. For example, it allows you to: Send a document to the printer in the office upstairs while

you are sitting on the couch with your laptop. Upload the photo from your cell phone to desktop

computer. Watch movies from an online streaming service to your TV.

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Local Area Network A local area network, or LAN, consists of a computer network at a

single site, typically an individual building. A LAN is very useful for sharing resources, such as data storage and

printers. LANs can be built with relatively inexpensive hardware, such as hubs, network adapters and Ethernet cables.

The smallest LAN may only use two computers, while larger LANs can accommodate thousands of computers. A LAN typically relies mostly on wired connections for increased

speed and security, but wireless connections can also be part of a LAN.

High speed and relatively low cost are the defining characteristics of LANs.

LANs are typically used for single sites where people need to share resources among themselves but not with the rest of the outside world.

If a local area network, or LAN, is entirely wireless, it is referred to as a wireless local area network, or WLAN.

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MANMetropolitan Area Network A metropolitan area network, or MAN, consists of a

computer network across an entire city, college campus or small region.

A MAN is larger than a LAN, which is typically limited to a single building or site.

Depending on the configuration, this type of network can cover an area from several miles to tens of miles.

A MAN is often used to connect several LANs together to form a bigger network.

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WAN A wide area network, or WAN, occupies a very large area,

such as an entire country or the entire world. A WAN can contain multiple smaller networks, such as LANs

or MANs. The Internet is the best-known example of a public WAN A WAN is a geographically-dispersed collection of LANs. A network device called a router connects LANs to a WAN. In IP networking, the router maintains both a LAN address and

a WAN address.

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Comparison of LAN MAN and WANLocal Area Network Metropolitan Area Network Wide Area Network

1.LAN is a group of computers and other network devices which are connected together.

MAN is a larger network of computers and other network devices which are connected together usually spans several buildings or large geographical area.

WAN is a group of computers and other network devices which are connected together which is not restricted to a geographical location. Internet is WAN

All the devices that are part of LAN are within a building or multiple building.

All the devices that are part of MAN are span across buildings or small town.

All the devices that are part of WAN have no geographical boundaries.

LAN network has very high speed mainly due to proximity of computer and network devices.

MAN network has lower speed compared to LAN.

WAN speed varies based on geographical location of the servers. WAN connects several LANs

LAN connection speeds can be 10Mbps/ 100Mbps/ 1000Mpbs

MAN connection speeds can be 10Mbps or 100Mbps.

WAN connection speeds can be 10Mbps or 100Mbps.

LAN uses Guided Media MAN uses Guided Media or Unguided media.

WAN mainly uses Guided Media or Unguided media. Its long distance communications, which may or may not be provided by public packet network.

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Other Types of Area Networks While LAN and WAN are by far the most popular network

types mentioned, you may also commonly see references to these others:

Wireless Local Area Network - a LAN based on Wi-Fi wireless network technology

Campus Area Network - a network spanning multiple LANs but smaller than a MAN, such as on a university or local business campus.

Storage Area Network - connects servers to data storage devices through a technology like Fibre Channel.

System Area Network - links high-performance computers with high-speed connections in a cluster configuration. Also known as Cluster Area Network.

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Topology in NetworkNetwork topologies are categorized into the

following basic types: bus ring star tree mesh

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Topology in Network Various configurations, called topologies, have been used to administer

LANs Ring topology A configuration that connects all nodes in a closed loop on

which messages travel in one direction. Star topology A configuration that centers around one node to which all

others are connected and through which all messages are sent. A star network features a central connection point called a "hub node" that may be a network hub , switch or router .

Bus topology All nodes are connected to a single communication line that carries messages in both directions. A single cable, the backbone functions as a shared communication medium that devices attach or tap into with an interface connector.

Tree Topology Tree topologies integrate multiple star topologies together onto a bus. In its simplest form, only hub devices connect directly to the tree bus, and each hub functions as the root of a tree of devices.

Mesh Topology Mesh topologies involve the concept of routes. Unlike each of the previous topologies, messages sent on a mesh network can take any of several possible paths from source to destination.

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Tree

Mesh

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Wireless LAN: BluetoothBluetooth A short-range communication system intended to replace the

cables connecting devices Key Features: Robustness, low power, and low cost Provides a way to connect and exchange information between

devices such as mobile phones, PCs, printers, such as mobile phones, PCs, printers, GPS receivers, digital cameras, and video game consoles

Speed of upto 1 Mbps

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Wireless LAN: Wi-Fi Typically called wireless LAN or Wireless Ethernet More powerful than Bluetooth and used in corporate settings

to connect PCs to PCs, corporate settings to connect PCs to PCs, printers, servers, etc

Supported by most PC OS, game consoles, smartphones, printers, etc

A Wi-Fi enabled device can connect to the Internet when within range of a wireless network connected to the Internet

Interconnected access points popularly called hotspots Hotspot - can comprise an area as small as a single room with

wireless-opaque walls or as large as many square miles covered by overlapping access points.

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Internetworking devicesIncreasing power and complexity Hubs Bridges Switches Routers

Computers within a LAN are often connected using a hub LAN to LAN connections are often performed with a bridge. Segments of a LAN are usually connected using a switch. LAN to WAN connections are usually performed with a

router.

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Hubs

A hub interconnects two or more workstations into a local area network.

When a workstation transmits to a hub, the hub immediately resends the data frame to all connecting links.

Hubs expand one Ethernet connection into many. For example, a four-port hub connects up to four machines

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Hubs

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Bridge A bridge connects networks and forwards

frames from one network to another.

BRIDGE

A B

C D

E F

G H

PORTS

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Selective Forwarding

If A sends a frame to E - the frame must be forwarded by the bridge.

If A sends a frame to B - there is no reason to forward the frame.

BRIDGE

A B

C D

E F

G H

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Bridge interconnection

Identical LANs

dissimilar LANs

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Bridges vs RoutersBridge: A bridge is a

device that connects two segments of the same network. The two networks being connected can be alike or dissimilar.

Bridges are protocol-independent. They simply forward packets without analyzing and re-routing messages.  

Router: A router is a device that connects two distinct networks. Routers are similar to bridges, but provide additional functionality, such as the ability to filter messages and forward them to different places based on various criteria.

The Internet uses routers extensively to forward packets from one host to another.

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Switches A switch is a combination of a hub and a bridge. It can interconnect two or more workstations, but like a bridge,

it observes traffic flow and learns. When a frame arrives at a switch, the switch examines the

destination address and forwards the frame out the one necessary connection.

Major role: isolating traffic patterns and providing multiple access. This design is usually done by the network manager.

Switches are easy to install and have components that are hot-swappable.

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Routers

The device that connects a LAN to a WAN or a WAN to a WAN (the INTERNET! – uses IP addresses).

A router accepts an outgoing packet, removes any LAN headers and trailers, and encapsulates the necessary WAN headers and trailers.

Because a router has to make wide area network routing decisions, the router has to dig down into the network layer of the packet to retrieve the network destination address.

Thus, routers are often called “layer 3 devices”. They operate at the third layer, or OSI network layer, of the packet.

Routers often incorporate firewall functions. An example of a router’s operation is shown on the next slide.