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72 Cards in this Set
- Front
- Back
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What is the basic function of a Network Model? |
●To transfer a message from sender to receiver. ●Break the set of communication functions into layers, each with own responsibilities |
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Can hardware, software or both be designed to work on each layer? |
Both hardware and software |
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What are the two Network Models called?
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Open Systems Interconnection (OSI) Model and Internet Model
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What is the purpose of the OSI Model?
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To simplify Networking Concepts (understanding, development, and implementation) and standardize open systems. Independence: layer level competition
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How many layers does the OSI Model have? And what are they?
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OSI = 7 layers. Layer 1, Physical, 2 Data link, 3 Network, 4 Transport, 5 Session 6 Presentation 7 Application
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How many layers does the Internet Model have? And what are they?
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Internet model = 5 layers. 1 Physical, 2 Data Link, 3 Network, 4 Transport, 5 Application
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How many groups of layers are there and what are they?
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There is 3 and they are Hardware layer, Internetwork Layer, and Application layer
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Who developed OSI Model?
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ISO
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What is Data Communication?
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Transmission of data between 2 devices by either electrical, optical, wireless or freespace transmission systems.
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Future of I.T
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Virtual Reality, Info Super Highways, Interactive Video
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True or False: Peer to peer networks require Network Operating System?
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False
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True or False: In twisted pair cabling, the wires are twisted to reduce the electromagnetic interference?
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True
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What is guided media?
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When the transmission flows along a physical guide. Examples: Twisted pair wiring, coaxial cable and optical fiber cable.
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What is Wireless Media?
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There is no wave guide, transmission just flows through the air. Examples: Radio, infrared, microwave, satellite communications
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True or False: Wireless LAN is a guided transmission medium?
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False
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True or False: Integration of voice, video and data is a future trend in ICT?
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True
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True or False: Asynchronous Transmission is more efficient technique than Synchronous Transmission?
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False
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What is Asynchronous Transmission?
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Start stop transmission, each character sent independently
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What is Synchronous Transmission?
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Characters are transmitted at one time as a block of data.
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Which one of the following devices is used to change digital computer signal for transmission over telephone lines? A. Modem B. Router C. Multiplexer D. Hub E. Codec
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A. Modem
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How many different amplitudes would be required to be able to send 3 bits per signal element (symbol) using Amplitude Modulation?A. 16 B. 18 C. 9 D. 8 E. None of the above
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8 |
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Which of the following devices is used to convert analogue to digital and vice versa at the telephone switch / exchange end?\nA. Switch B. Modem C. Codec D. Multiplexer E. None of the above
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C. Codec
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How many Amplitudes for a Amplitude Modulation (AM)?
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2
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Calculate 4 bit AM modulation = nn = n Amplitudes
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24 = 16
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______________ is a modulation technique that combines two different modulation combinations to send four bits per symbol. A. Quadrature amplitude modulation B. Time Division Multiplexing C. Synchronous Digital Line Control D. Pulse Code Modulation E. Baseband signaling
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A
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OSI Network Model has _____ layers.
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7
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US-ASCII, 7 bit coding system can provide codes for _______ valid characters
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128
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In a hierarchical design of switches the name for middle layer of switches between the Access switches and the Core switches is ____________ switch.
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Distribution switch
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What are the benefits of standardisation?
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Software / hardware made by different vendors work together
Easier to make software / hardware No monopoly Lowers prices Better quality (safety) |
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Describe the three stages of standardisation.
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Specification: Identify the problem, Identification: Identify the solutions, Acceptance: Get industry leaders to agree on a single uniform solution (standard)
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Why is data compression done in data communication?
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Can increase throughput of data, fewer bits are transmitted with compression without loss of any data (e.g. 1000 bits instead of 2000 bits) |
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Describe the two data compression techniques.
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Huffman Encoding: Compression rate of 2:1 ratio, Huffman table is to be seen with the message. Lempel-Ziv Encoding: compression rate of 6:1 ratio, when the same character pattern occurs in the message the index to the dictionary entry is transmitted rather than sending the actual data
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What are the benefits of multiplexing?
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Its cheaper because fewer network links are needed
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What is multiplexing?
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Breaking up a higher speed link into several slower links and vice versa. There are 2 types of multiplexing: Frequency Division Multi. And Time Division Multi.
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Compare FDM and TDM
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FDM: Divides circuit horizontal. Uses guardbands to separate the channels. Example: Cable TV. TDM: Divides circuit vertically. Time on the main link is shared equally with each smaller link getting a specified time slot whether it has data to send or not
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True or False: Fibre optic cable is guided transmission medium?
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True
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True or False: In frequency modulation the amplitude and phase of the wave remain constant?
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True
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True or False: Server computer requires Network Operating System?
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True
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True or False: The term “attenuation” refers to an increase in magnitude of power of the signal?
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False
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What is Attenuation?
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A decrease in magnitude of power of the signal (Weakening of the signal)
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True or False: Local Area Network (LAN) covers an entire city?
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False
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How many different amplitudes would be required to be able to send 4 bits per signal element (symbol) using Amplitude Modulation? \n A. 16 B. 18 C. 9 D. 32 E. None of the above.
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A. 16
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Trellis Code Modulation (TCM): \n A. Combines phase and frequency modulation\nB. Combines phase and amplitude modulation \nC. Can transmit 6-10 bits per signal element (symbol) \nD. is both B and C \nE. can provide a maximum of 12 bits?
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D. Both B and C.
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_____________ is a modulation technique that combines two different amplitude combinations to send four bits per symbol. \n A. Quadrature Amplitude Modulation B. Time Division Multiplexing C. Synchronous Digital Line Control D. Pulse Code Modulation E. Baseband signaling
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A.
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Which of the following statements is not true about Pulse Amplitude Modulation (PAM)? A. Measuring the signal B. Taking samples of the signal C. Encoding the signal as binary data sample D. Three steps are required for conversion E. Converts digital signal to analogue signal
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E
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Which of the following sets standard for the Internet? A. ISO B. ANSI C. IETF D. IEEEE E. ITU
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C. IETF
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Internet Network Model has _____ Layers?
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5
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US-ASCII, 7 bit coding can provide codes for ____________ valid characters
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128
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US-ASCII, 8 bit coding can provide codes for_____ valid characters
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256
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Local loop formed by wires that run from your home (or business) to the telephone exchange is also known as _______________________
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The last mile
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IEEE is the abbreviation for ________________________________________________
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Institute of Electrical and Electronics Engineers
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Describe Unipolar.
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Voltage is always positive or negative
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Describe Bipolar (NRZ/RN).
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Varies from plus to minus Voltage. Doesn’t return to zero after each bit / returns to zero.
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Differences between Bi-Polar and Unipolar signaling.
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Bipolar less errors than Unipolar.
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Describe Bandwidth with examples.
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Bandwidth is the width of the band. Difference between highest and lowest frequencies in a band. In digital networks bandwidth is used to describe the amount of data that can be send p.sec Example: Voice grade telephone circuits have a bandwidth of 300HZ to 4KHZ for voice transmission
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Describe Bit Rate with examples.
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Number of bits of data sent every second. Bit rate = baud rate * number of bits per symbol
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Describe Half-Duplex with examples
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Data flows both ways, but only one direction at a time. Some kind of control information must be included so that sender and receiver don’t send at the same time Example: CB Radio
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Describe Full Duplex
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Data flows in both directions at the same time
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Describe Simplex:
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Data flows move in one direction only, such as radio or cable TV broadcasts.
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What is Protocol? Examples?
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The standards which two communication devices communicate. E.g. TCP/IP, IPX/SPX
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Name the 3 groups of layers.
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Application Layer
Internetwork Layer Hardware Layer |
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What is MAN?
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Metropolitan Area Networks, Connects LANs within a city.
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What is WAN?
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Wide Area Networks, Connects LANs between cities and countries. Fibre, microwave and satellite used.
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What is a backbone network
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A larger central network connecting LANs, MANs and WANs.
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What are the 2 types of backbones?
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Switched backbone and router backbone
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What is Layer 1? What does it do?
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Physical Layer. Where data transfer occurs. Includes different types of media (cable and satellite)
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What is Layer 2? What does it do?
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Data Link Layer. Gets data from Network layer and passes to physical layer. Error detection / correction between adjacent nodes. 2 sublayers are MAC and LLC
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What is Layer 3? What does it do?
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Network Layer. Performs routing. Get data from transport and pass it to the data layer. Messages are sent to the right destination (IP – from TCP/IP and IPX (from IPX / SPX
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What is Layer 4? What does it do?
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Transport Layer. Can be called end to end layer. Deals with end to end issues, ensures data is sent to the right destination Examples: TCP and SPX
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What is Layer 5? What does it do?
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Session Layer. Establishes and manages a communication link between co-operating applications. Half / full duplex
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What is Layer 6? What does it do?
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Presentation Layer. Responsible for formatting and presentation of the data, like ASCII or EBCIDIC, encryption, compression standards
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What is Layer 7? What does it do?
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Application Layer. End user application access to the networks. Generates data to be transmitted. Examples: HTTP, SMTP
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