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Arab Open University – Bahrain Branch
T209 Revision Handout FALL 2004 – 2005

Notes This handout is not intended to replace the official course material you have. This handout is a supplementary, non-official material. You should study the official course material for the exam. Not all of the T209 aspects are covered in this handout. This handout will be distributed to the T209 students at Bahrain Branch. If you have any comments, please e-mail me [email protected]

T209 Information and Communication Technology

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Mobile phones and their features, development, battery life,…. etc. Portable Data Assistance (PDA) and the convergence that happened. Effect of the advances of the electronics growing in on the mobile communication (DSP). Migration of 2G (purely voice oriented) to 3G (voice and data) Convergence in technology means to combine or group together various functionalities into a single entity/product in the following manner Content (audio, video, text and graphics) Platform (mobile phones, PDA, computer and TV) Distribution (wireless and wired) Ultimate convergence: Audio, Video, Graphics and Text all delivered by a single type of service provider via a single type of connection to a single type of platform due to the developments in IC and DSP. Standards: technical specifications that describe how one product will interact with another product. Interoperability: two devices from different vendors can work together ( Nokia to Motorola) Standard types: • • • International standards: defined and maintained by international bodies. It can be used by any manufacturer. Examples: V Series of Modem and GSM standards Industry-wide standard (de facto): emerge from common usage. Examples: USB Proprietary standard: owned and developed by one manufacturer. Examples: PDF

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Standardization bodies: ITU – ETSI – UMTS – 3GPP – 3GPP2 – Bluetooth SIG – IEEE – ISO System: anything that performs certain functions. It should have an input, processing and output. For example the car engine system. The input is the fuel, the processing is the fuel processing and burning and the output is a mechanical energy. Any system may have several sub-systems. The car engine system has the cooling sub-system, the ignition sub-system, the combustion sub-systems .. etc. Examples of ICT systems: CT systems: mobile phones, telephones, fax, satellite, telephone exchange ..etc. IT systems: PC, printers, PDA … etc. ICT systems: smart phones, LAN, WAN, Internet, WLAN.. etc. Communication system: it has three main blocks. They are: Transmitter: the information source ( a person, a mobile. It could be speech or data) Channel: it is where the data propagates. Fixed wires, wireless, mobile, .. etc. Receiver: the entity that will received the information (a person, a mobile)

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T209 Information and Communication Technology

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Computer system: it has three main blocks: The processing unit (CPU): it is where all the processing occurs. The memory unit: it is the place where you can save data. • • • • RAM: Read Only Memory. It losses its content when you switch off the unit. ROM: it keeps its content when you switch off the unit Hard-disk: the OS and the applications are stored here. Removable storage devices: CD-ROM, Floppies, USB, ZIP drives, … etc

The Input/Output unit: any output you will get from the system. The screen, the printer and more. Categories of communication system: One-to-one: one sender to one recipient. Example: a simple telephone call. One-to-many: one sender to many recipients. Example: a web page viewed by many recipients. Many-to-many: many senders to many recipients. Example: TV broadcast. Unidirectional: one way. No message exchange. One direction. Examples: TV or Radio Bidirectional: two ways. It supports message exchange. Example: a telephone call. Asynchronous: the act of sending and receiving are separated in time. Sending and receiving are not synchronized. Example: the ATM network. Synchronous: sending and receiving are synchronized by using a synchronized clock. Example: TDMA Detailed communication system:

Sender

Transmitter

Channel

Receiver

Recipient

Sender: information source (speech or data) Transmitter: it produces a message suitable for transmission over the channel. Channel: the medium. Fixed wire (less noisy) , wireless (more noisy) Receiver: receives the information. The most complicated part of the system. Recipient: the person for whom the message is intended PDA: it is considered as a computer system. It has all the main components of the normal PC like the CPU, the memory and the output. Example of a PDA: The PDA name: The Psion Revo CPU Information: This PDA is built around the ARM 710T Microprocessor Memory Unit Information: 8 MB of RAM, 8 MB of ROM I/O Unit Information: 53-key keyboard and a grayscale touch-sensitive screen

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T209 Information and Communication Technology

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Compression: Decreasing the size of stored information by reducing the representation of the information without significantly diminishing the information itself, usually by removing redundancies. Requires decompression upon retrieval. Lossless compression allows the original data to be recreated exactly. Examples: GIF and ZIP. Two of the most famous algorithms are the run-length and the LZ algorithms. Lossy compression sacrifices some accuracy to achieve greater compression. Example: JPEG, MPEG and MP3. Example, use the run-length algorithm to calculate the compressed message and the compression ratio for the following 0000111111111111111111111? Compressed message = (4)(0)(20)(1) = (100)(0)(10100)(1) Compression ratio =

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number of bit in the original message 24 = = 2.4 number of bits in the original message 10

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Why do we use compression? A compressed file takes up less storage space than the uncompressed version. A compressed file can be transferred more quickly Compression ratio: is the number of bits in the original message divided by the number in the compressed message. Signals: any wave that contains information. Analog signal: amplitude and time are continuous Discrete signal: amplitude is analog and time is discrete Digital signal: both the time and amplitude are discrete Sinusoidal waveform: it has the following equation

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y(t) = A sin(ωt + φ)
where, Y, a function of time. It could be a volt or a current. It is called the instantaneous value. Measure in volt or ampere ω = 2πf, the angular frequency measured in radian per second or rad/second. f, the frequency, measured in hertz. How many complete cycles the wave will finish in one second. F=1/T T, the time period, measured in second, and it is the time needed to complete one cycle. The amplitude (A): it is the maximum value the wave can reach (negative or positive). Measured in volt or ampere.

Φ, the phase angle, it determines the shift of the wave to the right or to the left.

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T209 Information and Communication Technology

The cycle: a cycle has two parts, one negative and the other positive. A combination of one negative and one positive parts is called a cycle. Example 1:

(Note: Before you solve these types of questions, make sure that all the units are consistent. For example, volt, second not volt and microsecond.)

For the following sinusoidal wave, calculate the following: The amplitude (A): A= 4 volt The time period (T): T = 0.003 second or 0.006-0.003 = 0.003 second The frequency (F) : F = 1/T = 1/0.003 = 333.3 Hz The angular frequency (ω):ω = 2πf = 2 x π x 333.3 = 666.6 π rad/second The sinusoidal equation: v(t) = 4 sin(666.6 πt+ φ)

Example 2: Draw the sine wave that has got the following equation: v(t) = 3 sin(300 π t + φ). To draw a sine wave we need the following parameters. The amplitude and the time period. By comparing the given equation with the general sinusoidal equation, we get: v(t) = 3 sin(300 π t + φ)

v(t) = A sin(ωt + φ)
The amplitude A = 3 volt The angular frequency (ω) 300 π t = ω t

ω = 300 π
And since

ω = 2 π f , then 300 π = 2 π f
f = 300 / 2 = 150 Hz, so T = 1/f = 1/150 = 0.0066 = 6.6 ms

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T209 Information and Communication Technology

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Fourier analysis: it is a tool to express any periodic or non-periodic signal as a composition of basic sine and cosine waves. For Periodic signals we have the Fourier Series (as well as Fourier Transform). For Non-Periodic signals we have the Fourier Transform. Bandwidth: we have two types of bandwidth. They are as follows: Analog: the range of frequencies present in a signal. Bandwidth may also refer to the range of frequencies that can be transmitted in analogue form via a channel without any significant distortion or loss of signal amplitude. Digital: the maximum rate of transmission of data, usually expressed in bits per second.

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Analog bandwidth = F1 – F2 Modulation: The modification of some property of the waveform of a signal (the carrier), in response to the information contained in another signal (the message). When, as is usually the case, the carrier wave is sinusoidal, the properties modified are amplitude, frequency or phase (or a combination of these). Modulation is carried out in order to make the message signal more suitable for transmission, processing or storage. Frequency modulation (FM): In this system it is the frequency which is modulated (i.e. changed, varied etc) in response to the original signal. Amplitude modulation (AM): In this system it is the amplitude which is modulated (i.e. changed, varied etc) in response to the original signal. Phase Modulation (PM): In this system it is the phase which is modulated (i.e. changed, varied etc) in response to the original signal. Multiplexing: The process of combining a number of signals so that they can share a single transmission channel.

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T209 Information and Communication Technology

TDM: the time is shared. Used in speech network TDMA used in cellular / wireless network FDM: the frequency is shared. Used in speech network FDMA used in cellular / wireless network Analog to digital conversion (A/D): converting the analog signal to digital signal by sampling the time axis at discrete instances to get discrete time signal then quantizing the digital amplitude values to get the digital signal. Sampling frequency: if the frequency components extend from 0 to B hertz then Lowpass signal: it should be at least twice as the highest frequency = 2 B Highpass signal: at least twice the bandwidth Aliasing: if any of the above rules is violated and the signal is corrupted Mobile network First generation – analog Second generation – GSM digital Third generation – 3G (UMTS) Path loss: when the radio signal looses it is strength as it is propagates through the media Frequency reuse: using the same frequency by other users in different cells. The distance between the cells should be enough. Cell: s geographical area is divided into different regions called cells. Distance separation is done to avoid the interference and to enable frequency reuse. Microcells: smaller cells used in congested areas like the city center. Fading: The reduction in signal intensity of one or several of the components of a radio signal, typically caused by the reflective or refractive effects of multi-path. It can be caused by: Multipath propagation: when more than one copy of the transmitted signal arrive at the receiver. Doppler effect: as a result of the movement of the mobile station Combating fading: this can be achieved by the following: Adaptive filtering: it tries to identify the channel that causes fading. The system then tries to nullify the bad effect by using a compensating circuit Frequency hopping: when the GSM system switches rapidly from one carrier frequency to another to avoid fading at one frequency. Human-Computer Interaction (HCI): human–computer interaction is a discipline concerned with the design, evaluation and implementation of interactive computing systems for human use and with the study of the major phenomena surrounding them. User-computer interfacing: Command-based Form-fill
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T209 Information and Communication Technology

Menu driven Graphical user interface (GUI) Virtual reality: which attempts to place the user within a high-quality, three-dimensional animated representation of the world. Augmented reality: explores the fact that the physical configuration of a device is a major factor that determines its usability. Speech recognizer: SR involves the capture of speech signal by the speech recognizer and the recognition of the words and their meanings. There two types of SR: Isolated word recognition: These systems try to recognize individual words or short phrases, often called ‘utterances’. Pauses at the beginning and end of an utterance make the recognition process much easier because there are no transition stages between utterances. Continuous speech recognizer: the words are spoken at a normal speech rate without the need for short phrases. Recognition is more difficult because the end of one word runs into the beginning of the next. Another classification of ASR based on the number of speakers Speaker independent system: Here the system is trained with thousands of speech samples from thousands of different users. The vocabulary is about 2000 words. They are generally used for general public systems such as telephone banking, travel information systems. Speaker enrollment system: These are usually trained to a few users (usually a single individual). They can handle large vocabulary of say 50,000 words since the number of users is very less. Linguistics: this field is concerned with understanding of what it is spoken. Also with the rules of forming acceptable utterances of any language. Four elements of Linguistics are important for ASR systems and these are: Phonology: This is the study of vocal sounds. This will be studied in detail in section 3. Lexicon: This defines the vocabulary or words used in a language Syntax: This deals with the grammar of the language Semantics: This defines the conventions for deriving the meaning of words and sentences. Speech corpora: Thousands of examples of different speakers are required, all speaking the same words and under similar recording conditions. The resulting data sets are known as ‘speech corpora’. Phonemes: the fundamental elements of the spoken language. In English there are 42 phonemes. Spectrogram: it is a tool to measure variations of frequencies in the speech signal. It is also called the voice print. It is the magnitude square of the Short-Time Fourier transform (STFT). Spectrum: the magnitude square of the Fourier transform. Short Time Fourier Transform (STFT): is the Fourier transform of a small segment of speech signal. This small segment is created using a window function. Hence STFT is also known as a class of Windowed Fourier transforms.
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T209 Information and Communication Technology

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Formants: the resonance frequencies of the vocal tract. STAIR: it is a design strategy. It has the following: Statement – prepare a clear statement of the requirements. Tools – review your tools and select the most appropriate for the task. Our tools might be 'pencil and paper' a specific programming language, a drawing or word-processing software package, or an off-the shelf key-pad. Actions – deciding the what, when and how. Implementation – executing the action plan. Building and testing the simulator. Review – verifying that your solution fulfils the requirements. Each iteration should bring you closer to an understanding of the requirements and hence a better solution. Design tools: there are two types: Top-down design / task decomposition: reducing the size of the problem into smaller problems. Limitations: they don’t convey the sequential relationship between the tasks. Also the diagram doesn’t show how one task depends on the completion of another task. Flowcharting: number of predefined symbols linked by arrows. It describes the interaction between processes. Data: information coded and structured for subsequent processing generally by a computer. Information: the meaning given to the data. Knowledge: it is associated with people while information is independent. inter-networking in a business context means undertaking commerce between organizations, and with their customers, using both private and public networks. The B2B acronym is used to mean business-to-business commerce, e.g. with suppliers. B2C is used for business to customer commerce, e.g. sales and support. The term intranet, which has been coined to describe a private network that has the look and feel of the Web. It is accessed through a browser and can offer similar multimedia facilities, but is only used within a single organization. An extranet has similar properties to an intranet but extends its facilities to a group of related organizations with business connections. The OSI layered model, why do we need it? Reduces complexity Standardizes interfaces Facilities modular engineering Ensures interoperable technology Accelerated evolution Simplifies teaching and learning

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T209 Information and Communication Technology

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Protocol Data Unit (PDU): the name of the data at every layer in the OSI or the TCP/IP layered models. Application layer: network processes to application. Provides network services to application processes, such as e-mail, file transfer, terminal emulation…. etc. PDU Name: Data Presentation layer: data representation. Insure data is readable by the receiving system, format of data, data structure, negotiates data transfer syntax for application layer. PDU Name: Data Session layer: interhost communication. Established, manages and terminates sessions between applications. PDU Name: Data Transport layer: end-to-end communication. Concerned with the transportation issues between hosts. Data transport reliability. Established, maintains and terminates virtual circuits. Fault detection and recovery. Information flow control. PDU Name: segment Network layer: addressing and best path. Provides connectivity and best path selection between end systems. Domain of routing. PDU Name: packets Data link layer: provides reliable transfer of data across media. Physical addressing, network topology, error notification, flow control. PDU Name: frames Physical layer: binary transmission. Wires, connectors, voltages, data rates. PDU Name: bits Digital bandwidth: the maximum bit rate the channel can handle. Measuring units: communication world: • • • • • • k (kilo) means 1000 (103) M (mega) means 1 000 000 (106) G (giga) means 1 000 000 000 (109) K = 1024 (210) M = 1 048 576 (220) G = 1 073 741 824 (230)

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computer world:

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A group of eight bits. Octet is used in communications, and byte is used in computing. Connecting computers: to connect more than one computer, you can use the following ways: Point-to-point: this is used to connect two computers only. You need a UTP cable with RJ 45 connectors. The name of the cable is cross cable. Local Area Network (LAN): to connect more than two computers you an interconnection device like a switch or a hub. Wide Area Network (WAN): this is used to connect more than one location together. Examples of WAN technologies: ISDN, Frame Relay, SMDS, ATM, DSL, the Internet, and Satellite….. etc. Media: it is where the data propagates. There are two types of media: Wired: available physically. Example: UTP, Coaxial and Fiber optic cables. Wireless: data is transmitted on the air. Examples: Wi-Fi, infrared, Bluetooth, microwave… etc.

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T209 Information and Communication Technology

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Topology: it is the physical shape of the network. There are different types of network topologies:

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For the mesh topology, the number of links (wires) needed is as follows:

number of links =
Where n is the number of nodes.

n (n - 1) 2

Example: find the number of links needed to connect 200 nodes.
number of links = n ( n - 1 ) 200 (200 - 1) 200 x 199 = = = 19900 links 2 2 2

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Ethernet Standard: developed by DEC, Xerox and Intel in 1970’s It uses shared media, which means any data or collision will be heard by all the machines. It uses Unshielded Twisted Pair (UTP) category 5, 5e or 6 with 4 pairs of wires (8 wires) To get rid of crosstalk, pairs are twisted. Full-duplex mode is the most common type with speed up to 1 Gbps used in backbone and 100 Mbps used in normal cases. Access method is Carrier Sense Multiple Access with Collison Detection (CSMA/CD) that works as follows: • • All machines sense the media, if there is a signal on the media, they don’t send. If the media is idle, they send their data.

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T209 Information and Communication Technology

• • • •

It is possible that two machines will sense that the media is idle, if this is the case, a collision will occur. When collision happens, it will be sensed by all the machines. A jam signal will be sent in the media to tell everybody to stop sending any data for a small period of time called the back-off time. After this time elapses, all machines will sense the media again, if the collision has vanished, then data can be sent. If the collision is still their, they will enter another back-off period and the time will be increased from the first period.

Round trip delay: it is the time needed for an Ethernet frame to travel the whole length of the network. The minimum Ethernet frame length is 512 bits and for a 10 Mbps network, the round trip delay will equal to 51.2 µs. Example For the network shown, assuming that each repeater introduces a delay of 3.5 µs and the propagation speed is 1.77×108 m/s and the length of each segment is 500 meters. Find the following:

B

A

R1

C

R2

1. The one way delay between A and B

R3

time =

dis tan ce 500 = = 2.82µs speed 1.77 × 10 8

2. The one way delay between B and C

D

time =

dis tan ce 500 + R1 = + 3.5 = 2.82 + 3.5 = 6.32 µs speed 1.77 × 10 8

3. The two way delay A and D

time =

dis tan ce 2000 + R1 + R 2 + R3 = + 3.5 + 3.5 + 3.5 = 11.2 + 10.5 = 21.7 µs speed 1.77 × 10 8

So the two way delay is 2 x 21.7 = 43.4 µs
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T209 Information and Communication Technology

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Ethernet frame: the process of adding additional control information to the user data is called the framing.

64 bits
Preamble

48 bits
Destination Address

48 bits
Source Address

16 bits
Type/Length

46 -1500 bytes
Data

32 bits
Frame Checksum Trailer

Header

Data

Preamble: to synchronize the receiver. Destination address: the MAC address of the destination. Source address: the MAC address of the source. Type/length: the type of packet being carried in this frame (IP packet) or the length of the data field. Frame checksum: for error checking, Cyclic Redundancy Check is used. Extending LAN: we have many options to extend a LAN if we reach the maximum physical limits using the interconnection devices like a repeater, a bridge, a hub or a switch
(Note: maximum limits are: UTP= 100 m, Coaxial Cable: Thin 185 m and Think 500 m, Fiber: 3000 m)

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Packets Frames Bits

Network Data Link Physical

Router Bridge / Switch Repeater / Hub

Repeater / hub: layer one device. It can understand bit only (0,1). Using this option will not give any performance advantages. (Hub: a multi-port repeater). Bridge/switch: a layer two device. We can use this option to segment our network. By segmenting we mean introducing multiple collision domains thus achieving a better network performance. (Switch: a multi-port bridge) Router: a layer three device. At this level, connecting different network running different protocols is possible. It is where the best path is calculated and hence routing of data occurs. By using a router we can have multiple collision and broadcast domains. Summary: Hub/Repeater: Single Collision Domain, Single Broadcast Domain Bridge/Switch: Single Broadcast Domain, Multiple Collision Domain Router: Multiple Broadcast Domain, Multiple Collision Domain
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T209 Information and Communication Technology

Broadcast / Collision Domains

PC PC PC PC

Single Collision / Broadcast Domain Repeater / Hub

PC PC PC PC

Collision Domain

Broadcast Domain

Collision Domain

PC PC PC PC Bridge/Switch

PC PC PC PC

Broadcast Domain
Collision Domain

Broadcast Domain Broadcast Domain
Collision Domain

PC PC PC PC Router

PC PC PC PC

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T209 Information and Communication Technology

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Encapsulation: The technique used by layered protocols in which a layer adds header information to the protocol data unit (PDU) from the layer above. As an example, in Internet terminology, a packet would contain a header from the physical layer, followed by a header from the network layer (IP), followed by a header from the transport layer (TCP), followed by the application protocol data.

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TCP/IP Vs. OSI layered Models

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T209 Information and Communication Technology

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TCP/IP Protocol Graph

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Peer-to-peer communication: the only layer that can understand the control information in the header is the peer layer. Network layer in the destination can understand the control information of the network layer in the source. This virtual communication is called peer-to-peer.

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Connection orientated service: in this type of communication, the user is required to keep the connection established and active throughout the transmission of information. This service is delivered by the TCP. Example: a telephone call Connection-less service: A connectionless service does not require the user to keep the connection established and active throughout the transmission of information. Each packet of data is sent and routed independently. This is usually associated with best effort services such as the I P. IP address: it is a 32 bit long number. It can be interpreted by the network/internet layer for the routing purposes. Example: 192.168.11.12

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T209 Information and Communication Technology

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Networking management: it is the process of configuring, managing, monitoring the network resources and components. It uses the Simple Network Management Protocol (SNMP). SNMP commands:

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GetRequest: asks for the value of a variable stored in the management information base (MIB) of the element. GetNextRequest: requests information on multiple variables from the MIB and is used to reduce network traffic. If one or more of the requested variables is unavailable, no values are returned and an error is reported. GetResponse: is sent by an agent in reply to one of the above PDUs as a confirmation response along with the requested data. SetRequest: sets a MIB variable to a desired value. Trap: an unsolicited message sent from an agent to the manager, usually to notify an alarm or similar event occurrence.

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