Internet dan Jaringan Komputer Komunikasi Data dan Jaringan Komputer (Bagian 1)

Dr. Tb. Maulana Kusuma [email protected]

http://staffsite.gunadarma.ac.id/mkusuma

Magister Manajemen Sistem Informasi 0

Referensi

W. Stallings,

Data and Computer Communications

, 4 ed , Macmillan, 1994.

F. Halsall,

Data Communications, Computer Networks and Open Systems

, Addison Wesley, 1996.

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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 Magister Manajemen Sistem Informasi 2

Simplified Communications Model - Diagram

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Simplified Data Communications Model

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Key Communications Tasks

Transmission System Utilization Interfacing Signal Generation Synchronization Exchange Management Error detection and correction Addressing and routing Recovery Message formatting Security Network Management Magister Manajemen Sistem Informasi 5

Communications Standard

Many types of connection media : telephone lines, optical fibers, cables, radios, etc.

Many different types of machines and operating systems Many different network applications Magister Manajemen Sistem Informasi 6

What “Standard” means?

How many volts pulse is a 0 and 1 ? How to determine the end of a message ? How to handle lost messages ? How many bits for different data types ? Integers/Strings, etc.; are ASCII chars ?

How machines are identified ?

How to find the way to reach a machine ?

How applications speaks together through the network ?

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Standard Bodies

International Telecommunications Union – Telecommunications Sector (ITU-T) Institute of Electrical and Electronics Engineers (IEEE) International Organization for Standardization (ISO) Electronic Industries Alliance (EIA) dll Magister Manajemen Sistem Informasi 8

The ISO/OSI Model

ISO (the International Standards Organization) has developed a reference model for communications, called the OSI (

Open Systems Interconnection

) OPEN SYSTEM means that it can communicate with any other system that follows the specified standards, formats and semantics.

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OSI Networking Model

Program X Application Presentation Session Transport Network Data link Physical Data AH Data LH NH TH SH PH Data unit Data unit Data unit Data unit Data unit Bits LT Physical transmission medium Program Y Application Presentation Session Transport Network Data link Physical Magister Manajemen Sistem Informasi 10

OSI Layers (1)

Physical  Physical interface between devices Mechanical Procedural Data Link  Electrical Functional Means of activating, maintaining and deactivating a reliable link   Error detection and control Higher layers may assume error free transmission Magister Manajemen Sistem Informasi 11

OSI Layers (2)

Network  Transport of information  Higher layers do not need to know about underlying technology  Not needed on direct links Transport    Exchange of data between end systems Error free In sequence    No losses No duplicates Quality of service Magister Manajemen Sistem Informasi 12

OSI Layers (3)

Session   Control of dialogues between applications Dialogue discipline   Grouping Recovery Presentation  Data formats and coding   Encryption Application  Data compression Means for applications to access OSI environment Magister Manajemen Sistem Informasi 13

Transmission Medium

Guided - wire Unguided - wireless Characteristics and quality determined by medium and signal For guided, the medium is more important For unguided, the bandwidth produced by the antenna is more important Key concerns are data rate and distance Magister Manajemen Sistem Informasi 14

Guided Transmission Media

Twisted Pair Coaxial cable Optical fiber Magister Manajemen Sistem Informasi 15

Twisted Pair

Twisted pair -

INEXPENSIVE

 Two wires twisted together.

Makes them less susceptible to acting like an antenna and picking up radio frequency information or appliance noise.

 Telephone company uses twisted-pair copper wires to link telephones.

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Twisted Pair

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Twisted Pair - Applications

Most common medium Telephone network  Between house and local exchange (subscriber loop) Within buildings  To private branch exchange (PBX) For local area networks (LAN)  10Mbps or 100Mbps Magister Manajemen Sistem Informasi 18

Twisted Pair - Pros and Cons

Cheap Easy to work with Low data rate Short range Magister Manajemen Sistem Informasi 19

Twisted Pair - Transmission Characteristics

Analog  Amplifiers every 5km to 6km Digital   Use either analog or digital signals repeater every 2km or 3km Limited distance Limited bandwidth (1MHz) Limited data rate (100MHz) Susceptible to interference and noise Magister Manajemen Sistem Informasi 20

Unshielded and Shielded TP

Unshielded Twisted Pair (UTP)   Ordinary telephone wire Cheapest   Easiest to install Suffers from external EM interference Shielded Twisted Pair (STP)  Metal braid or sheathing that reduces interference   More expensive Harder to handle (thick, heavy) Magister Manajemen Sistem Informasi 21

UTP Categories

Cat 3   up to 16MHz Voice grade found in most offices  Twist length of 7.5 cm to 10 cm Cat 4  up to 20 MHz Cat 5 or Cat 6    up to 100MHz Commonly pre-installed in new office buildings Twist length 0.6 cm to 0.85 cm Magister Manajemen Sistem Informasi 22

Coaxial Cable (1)

Coaxial cable Use this when 1. Long distances 2. Lots of interference

 Also two wires: One of the wires is woven of fine strands of copper forming a tube. The wire mesh surrounds a solid copper wire that runs down the center. Space between has a non-conducting material.

Makes them more impervious to outside noise.

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Coaxial Cable (2)

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Coaxial Cable (3)

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Coaxial Cable Applications

Most versatile medium Television distribution  Aerial to TV  Cable TV Long distance telephone transmission  Can carry 10,000 voice calls simultaneously  Being replaced by fiber optic Short distance computer systems links Local area networks Magister Manajemen Sistem Informasi 26

Coaxial Cable - Transmission Characteristics

Analog  Amplifiers every few km  Closer if higher frequency  Up to 500MHz Digital  Repeater every 1km  Closer for higher data rates Magister Manajemen Sistem Informasi 27

Optical Fiber (1)

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Optical Fiber (2)

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Optical Fiber (3)

Fiber-optic cable (

BIG JOBS + EXPENSIVE)

 Light is electromagnetic.

 Can transmit more information down a single strand. It can send a wider set of frequencies.

 Each cable can send several thousand phone conversations or computer communications.

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Optical Fiber - Spectrum

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Optical Fiber - Benefits

Greater capacity  Data rates of hundreds of Gbps Smaller size & weight Lower attenuation Electromagnetic isolation Greater repeater spacing  10s of km at least Magister Manajemen Sistem Informasi 32

Optical Fiber - Applications

Long-haul trunks Metropolitan trunks Rural exchange trunks Subscriber loops LANs Magister Manajemen Sistem Informasi 33

Optical Fiber - Transmission Characteristics

Act as wave guide for 10 14 to 10 15 Hz  Portions of infrared and visible spectrum Light Emitting Diode (LED)   Cheaper Wider operating temp range  Last longer Injection Laser Diode (ILD)  More efficient  Greater data rate Wavelength Division Multiplexing (WDM) Magister Manajemen Sistem Informasi 34

Optical Fiber Transmission Modes

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Wireless Transmission

Unguided media Transmission and reception via antenna Directional  Focused beam  Careful alignment required Omni-directional  Signal spreads in all directions  Can be received by many antenna Magister Manajemen Sistem Informasi 36

Frequencies

2GHz to 40GHz  Microwave  Highly directional   Point to point Satellite 30MHz to 1GHz  Omni directional  Broadcast radio 3 x 10 11 to 2 x 10 14   Infrared Local Magister Manajemen Sistem Informasi 37

Terrestrial Microwave

Parabolic dish Focused beam Line of sight Long haul telecommunications Higher frequencies give higher data rates Magister Manajemen Sistem Informasi 38

Satellite Microwave

Satellite is relay station Satellite receives on one frequency, amplifies or repeats signal and transmits on another frequency Requires geo-stationary orbit  Height of ±35,784km Television Long distance telephone Private business networks Magister Manajemen Sistem Informasi 39

Broadcast Radio

Omni-directional FM radio UHF and VHF television Line of sight Suffers from multi-path interference Magister Manajemen Sistem Informasi 40

Infrared

Modulate non-coherent infrared light Line of sight (or reflection) Blocked by walls e.g. TV remote control, IRD port Magister Manajemen Sistem Informasi 41

Terminology (1)

Transmitter Receiver Medium  Guided medium e.g. twisted pair, optical fiber  Unguided medium e.g. air, water, vacuum Magister Manajemen Sistem Informasi 42

Terminology (2)

Direct link  No intermediate devices Point-to-point  Direct link  Only 2 devices share link Multi-point  More than two devices share the link Magister Manajemen Sistem Informasi 43

Terminology (3)

Simplex  One direction e.g. Television Half duplex  Either direction, but only one way at a time e.g. police radio Full duplex  Both directions at the same time e.g. telephone Magister Manajemen Sistem Informasi 44

Terminology (4)

Bits per second

(bps).

 The number of bits (0’s and 1’s) that travel down the channel per second.

Baud rate

 The number of bits that travel down the channel in a given interval.

 The number is given in signal changes per second, not necessarily bits per second.

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Terminology (5)

Asynchronous transmission

  Information is sent byte by byte.

Cheaper and more commonly used.

Synchronous transmission

   Data is sent in large blocks rather than in small pieces.

Preceded by special information, concerning error detection and block size.

These modems are expensive but very fast.

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Analog and Digital Data Transmission

Data  Entities that convey meaning Signals  Electric or electromagnetic representations of data Transmission  Communication of data by propagation and processing of signals Magister Manajemen Sistem Informasi 47

Data

Analog  Continuous values within some interval  e.g. sound, video Digital  Discrete values  e.g. text, integers Magister Manajemen Sistem Informasi 48

Data and Signals

Usually use digital signals for digital data and analog signals for analog data Can use analog signal to carry digital data  Modem Can use digital signal to carry analog data  Compact Disc audio Magister Manajemen Sistem Informasi 49

Signals

Type of signal communicated (analog or digital).



Analog:

Those signals that vary with smooth continuous changes.

 A continuously changing signal similar to that found on the speaker wires of a high-fidelity stereo system.

Digital:

Those signals that vary in steps or jumps from value to value. They are usually in the form of pulses of electrical energy (represent 0s or 1s).

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Analog Signals Carrying Analog and Digital Data

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Digital Signals Carrying Analog and Digital Data

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Analog Transmission

Analog signal transmitted without regard to content May be analog or digital data Attenuated over distance Use amplifiers to boost signal Also amplifies noise Magister Manajemen Sistem Informasi 53

Digital Transmission

Concerned with content Integrity endangered by noise, attenuation etc.

Repeaters used Repeater receives signal Extracts bit pattern Retransmits Attenuation is overcome Noise is not amplified Magister Manajemen Sistem Informasi 54

Advantages of Digital Transmission

Digital technology  Low cost LSI/VLSI technology Data integrity  Longer distances over lower quality lines Capacity utilization  High bandwidth links economical  High degree of multiplexing easier with digital techniques Security & Privacy  Encryption Integration  Can treat analog and digital data similarly Magister Manajemen Sistem Informasi 55

Transmission Impairments

Signal received may differ from signal transmitted Analog - degradation of signal quality Digital - bit errors Caused by     Attenuation and attenuation distortion Propagation delay Noise Interference Magister Manajemen Sistem Informasi 56

Attenuation

Signal strength falls off with distance Depends on medium Received signal strength:  must be enough to be detected  must be sufficiently higher than noise to be received without error Attenuation is an increasing function of frequency Magister Manajemen Sistem Informasi 57

Propagation Delay

The time required for a signal to travel from one point to another. Propagation velocity varies with frequency.

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Noise (1)

Additional signals inserted between transmitter and receiver Thermal  Due to thermal agitation of electrons  White noise Inter-modulation  Signals that are the sum and difference of original frequencies sharing a medium Magister Manajemen Sistem Informasi 59

Noise (2)

Crosstalk  A signal from one line is picked up by another Impulse  Irregular pulses or spikes  e.g. External electromagnetic interference  Short duration  High amplitude Magister Manajemen Sistem Informasi 60

Channel Capacity

Data rate  In bits per second  Rate at which data can be communicated Bandwidth  In cycles per second of Hertz  Constrained by transmitter and medium Magister Manajemen Sistem Informasi 61

Modulation Techniques

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Adaptive Modulation

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Data Rate and Bandwidth

Any transmission system has a limited band of frequencies This limits the data rate that can be carried Magister Manajemen Sistem Informasi 64

Multiplexing

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Time Division Multiplexing

Data rate of medium exceeds data rate of digital signal to be transmitted Multiple digital signals interleaved in time May be at bit level of blocks Time slots pre-assigned to sources and fixed Time slots allocated even if no data Time slots do not have to be evenly distributed amongst sources Magister Manajemen Sistem Informasi 66

Time Division Multiplexing

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TDM System

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Frequency Division Multiplexing

FDM Useful bandwidth of medium exceeds required bandwidth of channel Each signal is modulated to a different carrier frequency Carrier frequencies separated so signals do not overlap (guard bands) e.g. broadcast radio Channel allocated even if no data Magister Manajemen Sistem Informasi 69

Frequency Division Multiplexing Diagram

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FDM System

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Increasing Network Capacity Options

More Fibers (SDM) Same bit rate, more fibers Slow Time to Market Expensive Engineering Limited Rights of Way Duct Exhaust W D M Same fiber & bit rate, more

l

s Fiber Compatibility Fiber Capacity Release Fast Time to Market Lower Cost of Ownership Utilizes existing TDM Equipment Faster Electronics (TDM) Higher bit rate, same fiber Electronics more expensive

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Fiber Networks

Time division multiplexing  Single wavelength per fiber  Multiple channels per fiber  4 OC-3 channels in OC-12  4 OC-12 channels in OC-48  16 OC-3 channels in OC-48 Wave division multiplexing  Multiple wavelengths per fiber  4, 16, 32, 64 channels per system  Multiple channels per fiber

Channel 1 Channel n l1 l2 ln

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Single Fiber (One Wavelength) Single Fiber (Multiple Wavelengths)

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Types of WDM

Coarse WDM (CWDM)  Uses 3000GHz (20 nm) spacing.

  Up to 18 channels.

Distance of 50 km on a single mode fiber.

Dense WDM (DWDM)  Uses 200, 100, 50, or 25 GHz spacing.

  Up to 128 or more channels.

Distance of several thousand kilometres with amplification and regeneration.

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TDM and DWDM Comparison

TDM (SONET/SDH)  Takes sync and async signals and multiplexes them to a single higher optical bit rate  E/O or O/E/O conversion

DS-1 DS-3 OC-1 OC-3 OC-12 OC-48 SONET ADM Fiber

(D)WDM  Takes multiple optical signals and multiplexes onto a single fiber  No signal format conversion

OC-12c OC-48c OC-192c

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DWDM OADM Fiber

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Why DWDM —The Business Case

Conventional TDM Transmission —10 Gbps 40km TERM TERM TERM TERM 1310 40km 40km 1310 1310 RPTR RPTR 40km 40km 40km 40km 40km 40km 1310 1310 1310 1310 1310 TERM TERM TERM TERM RPTR RPTR RPTR RPTR RPTR RPTR OC-48 OC-48 OC-48 OC-48 OA DWDM Transmission —10 Gbps 120 km 120 km 120 km OA OA OA OC-48 OC-48 OC-48 OC-48 4 Fibers Pairs 32 Regenerators 1 Fiber Pair 4 Optical Amplifiers

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Optical Transmission Bands

Band “New Band” S-Band C-Band L-Band U-Band Wavelength (nm) 820 - 900 1260 – 1360 1360 – 1460 1460 – 1530 1530 – 1565 1565 – 1625 1625 – 1675 Magister Manajemen Sistem Informasi 77

Characteristics of a WDM Network

Sub-wavelength Multiplexing or MuxPonding

Ability to put multiple services onto a single wavelength Magister Manajemen Sistem Informasi 78

Transmission Effects

Attenuation:  Reduces power level with distance Dispersion and nonlinear effects:  Erodes clarity with distance and speed •

Noise and Jitter: Leading to a blurred image

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