Data Communication and Networking Unit 1

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Questions and Answers

What is the role of the USART in data transmission?

Convert data from parallel to serial at the sender (correct)

Generate SYN characters at the beginning of every data block

Recognize signals at the receiving end

Convert data from serial to parallel at the receiver

Attenuation is a form of delay distortion.

False

What are the two types of errors that can occur if the signal carries binary data?

Single bit error and burst errors

In Time Division Multiplexing (TDM), transmission time is divided into number of ____________.

time slices Signup and view all the answers

What is a network?

A network is a set of devices connected by communication links, where devices can be computers, printers, or any other devices capable of sending and/or receiving data. Signup and view all the answers

What is the process of imposing an input signal onto a carrier wave by varying its one or more properties called?

modulation Signup and view all the answers

What is data communication?

Data communication is the exchange of information between two or more computers. Signup and view all the answers

Which modulation technique keeps the frequency and phase of the carrier signal constant while varying the amplitude to represent bit 0 and 1?

Amplitude Shift Keying (ASK) Signup and view all the answers

In full duplex transmission, data can only flow one way at a time.

False Signup and view all the answers

What is an IP address?

An IP address is a unique identifier that identifies a device on the internet. Signup and view all the answers

______ communication is a method of sending data one bit at a time over a communication channel.

Serial Signup and view all the answers

What is a MAC address?

A MAC address is a unique identifier assigned to a network interface controller (NIC) for communication within a network segment. Signup and view all the answers

What is the purpose of a modem in data communication?

A modem converts data into a format suitable for a transmission medium to enable communication between computers. Signup and view all the answers

Match the modulation technique with its description:

Amplitude Shift Keying (ASK) = Varying amplitude to represent bits 0 and 1 Frequency Shift Keying (FSK) = Varying frequency to represent bits 0 and 1 Phase Shift Keying (PSK) = Varying phase to represent bits 0 and 1 Signup and view all the answers

What are the two types of transmission media?

Wired media and Wireless media Signup and view all the answers

What does WDM stand for?

Wavelength Division Multiplexing Signup and view all the answers

In the Stop and Wait flow control method, the sender sends multiple frames at a time.

False Signup and view all the answers

What mechanism is used to detect and control errors in the data link layer in Go-Back-N protocol?

NAK Signup and view all the answers

In a Sliding Window method, multiple frames are sent by the sender at a time before requiring an acknowledgment. The window size is numbered modulo-___

n Signup and view all the answers

Match the following transmission media with their descriptions:

Twisted pair wire = Carries data in the form of electric current signals Coaxial cable = Consists of an inner conductor surrounded by insulating sheath and outer conductor Optical fiber = Transmits data in terms of light and is made up of glass fibers enclosed in a plastic jacket Signup and view all the answers

What is the phenomenon called when a spoon immersed in a glass of water appears bent?

Refraction Signup and view all the answers

Which types of multimode propagation are mentioned in the text?

Step Index Signup and view all the answers

Step Index is characterized by a sudden change in the direction of light at the core-cladding interface.

True Signup and view all the answers

In Single Mode propagation, the light beam travels more or less __________.

horizontally Signup and view all the answers

Match the internetworking devices with their descriptions.

Repeater = Regenerates a signal at the physical layer of the OSI model Bridge = Divides a network into smaller subnetworks and forwards data intelligently Router = Intelligent device operating at the physical, data link, and network layer Gateway = Operates at all layers of the OSI model and relays frames between different network types Signup and view all the answers

What are some common resources shared in a Local Area Network (LAN)?

Printers Signup and view all the answers

Ethernet uses bus topology for its physical network layout.

True Signup and view all the answers

What is the primary purpose of a Wide Area Network (WAN)?

connect cities, states, countries, or continents Signup and view all the answers

The main broadcast method used in Local Area Networks (LANs) is ____. Nodes in a LAN share the same transmission medium.

bus Signup and view all the answers

Match the LAN technology with its corresponding topology:

Ethernet = Bus Topology Token Ring = Ring Topology Fiber Distributed Data Interface (FDDI) = Ring Topology Signup and view all the answers

Which of the following is true about the D channel in ISDN?

It carries control signals for bearer channels. Signup and view all the answers

What are the three types of H-Channels in ISDN based on data rates?

H0 (384 kbps), H11 (1536 kbps), H12 (1920 kbps) Signup and view all the answers

TCP/IP model has five layers: application layer, transport layer, network layer, data link layer, and physical layer.

True Signup and view all the answers

Which protocol at the Transport layer of TCP/IP is connection-oriented and provides reliable communication between end systems?

TCP Signup and view all the answers

The Window size field in TCP/IP is a 16-bit field that determines the size of data the ______ can accept.

receiver Signup and view all the answers

Which of the following statements is true about the User Datagram Protocol (UDP)?

It is less concerned with reliability and security. Signup and view all the answers

Study Notes

Data Communication and Networks

A network is a set of devices (nodes) connected by communication links, which can be computers, printers, or any other device capable of sending and/or receiving data.

Data Communication

Data communication refers to the exchange of information between two or more computers using a common language and protocol.
An IP address is a unique address that identifies a device on the internet, allowing information to be sent between devices on a network.
IP addresses are 32-bit addresses, and the address space of IPv4 is 2^32 or 4,294,967,296.

MAC Address

A Media Access Control (MAC) address is a unique identifier assigned to a network interface controller (NIC) for use as a network address in communications within a network segment.
A MAC address is hardcoded onto a network interface card (NIC) and is unique to it.
MAC addresses are 48-bit addresses and are typically displayed in a 12-digit hexadecimal number with a colon or hyphen separating every two digits.

Simplest Form of Data Communication

The simplest form of data communication involves a sender, a receiver, and a transmission medium.
The transmission medium can be wired or wireless, and the data is transmitted in the form of bits (0s and 1s).

Real-Life Data Communication

Real-life data communication involves many hardware devices and software techniques, including modems, multiplexers, demultiplexers, transmission media, topology, routing, and protocols.
Modems convert data into a format suitable for a transmission medium, and multiplexers combine multiple data streams into one composite signal.

Characteristics of Data Communication

Correct delivery: the data must reach only the intended recipient and not someone else.
Accurate delivery: there must not be any alteration in data while it is in transit.
Timely delivery: data must travel from sender to receiver in a finite amount of time.

Protocols

A protocol defines three elements: syntax (what is to be communicated?), semantics (how it is to be communicated?), and timing (when it is to be communicated?).
Protocols are necessary for devices from different vendors to communicate with each other.

Standards

Standards are necessary in data communication to ensure that devices from different vendors can work together.
There are two types of standards: de jure (formal) and de facto (emerged in the marketplace).

Signal Propagation

Signal propagation is the fundamental basis for data communication to take place.
Signal propagation involves the transmission of a signal from a source to a receiver.

Sinusoidal Signal

A sinusoidal signal is a waveform that oscillates at a specific frequency and amplitude.
The amplitude of a signal can be measured in volts, amperes, or watts.

Period, Frequency, and Phase

The period of a signal is the time it takes to complete one cycle.
The frequency of a signal is the number of cycles it completes in one second.
The phase of a signal is the position of the waveform relative to time zero.

Bandwidth

The bandwidth of a signal is the difference between the upper and lower frequencies of a signal.
The bandwidth of a channel is the maximum bit rate supported by the channel.

Analog and Digital Transmission Methods

There are four possible types of transmission methods:
- Analog signal, analog transmission
- Digital signal, digital transmission
- Digital signal, analog transmission
- Analog signal, digital transmission

Analog Signal Analog Transmission

Analog signal analog transmission involves the transmission of an analog signal over an analog transmission medium.
Amplifiers are used to overcome attenuation and noise in the signal.

Digital Signal Digital Transmission

Digital signal digital transmission involves the transmission of a digital signal over a digital transmission medium.
Repeaters are used to amplify or regenerate the signal to extend its transmission distance.

Digital Signal Analog Transmission

Digital signal analog transmission involves the conversion of a digital signal to an analog signal using a modem.
The analog signal is transmitted over an analog transmission medium and converted back to a digital signal at the receiving end.

Modulation Techniques

Modulation techniques involve the imposition of an input signal onto a carrier wave by varying its amplitude, frequency, or phase.
There are three types of modulation techniques: amplitude shift keying (ASK), frequency shift keying (FSK), and phase shift keying (PSK).

Amplitude Shift Keying (ASK)

ASK involves the variation of the amplitude of the carrier signal to represent 0s and 1s.
ASK is susceptible to noise and is less efficient in terms of bandwidth.

Frequency Shift Keying (FSK)

FSK involves the variation of the frequency of the carrier signal to represent 0s and 1s.
FSK provides better noise immunity and is suitable for long-distance data transmission.

Phase Shift Keying (PSK)

PSK involves the variation of the phase of the carrier signal to represent 0s and 1s.
PSK is more bandwidth-efficient than ASK and FSK.

Analog Signal Digital Transmission

Analog signal digital transmission involves the conversion of an analog signal to a digital signal using a codec (coder/decoder) or A/D converter.
The digital signal is transmitted over a digital transmission medium and converted back to an analog signal at the receiving end.

Pulse Code Modulation (PCM)

PCM is a technique used to convert an analog signal to a digital signal.
PCM involves sampling, quantization, and encoding the analog signal.

Modes of Data Transmission

There are three modes of data transmission: simplex, half-duplex, and full-duplex.
Simplex communication is a one-way communication, where data is transmitted in one direction only.
Half-duplex communication is a two-way communication, where data is transmitted in one direction at a time.
Full-duplex communication is a two-way communication, where data is transmitted in both directions simultaneously.

Parallel and Serial Communication

Parallel communication involves the transmission of multiple bits simultaneously over multiple wires.
Serial communication involves the transmission of one bit at a time over a single wire.
Parallel communication is faster and more suitable for short-distance communication, while serial communication is more suitable for long-distance communication.### Synchronization in Serial Communication
In serial communication, the start of every character transmitted and the middle position of each bit interval must be identified to measure the bit value.
Sender and receiver have different clocks, which need to be synchronized to ensure correct readings.
There are three approaches to achieve synchronization: Asynchronous Communication, Synchronous Communication, and Isochronous communication.

Asynchronous Communication

In asynchronous communication, the time of character transmission is unpredictable.
Characters are preceded by a start bit and succeeded by 1, 1.5, or 2 stop bits.
NRZ-L signaling is used for encoding the signal.
When a line is idle, a constant negative voltage (signifying binary 1) is sent.
When a character is sent, a start bit (0) is sent, followed by 5-8 bits of the character, a parity bit (if used), and then a stop bit.

Synchronous Communication

In synchronous transmission, a whole block of data bits is transferred at once.
The block of bits may or may not contain different characters, or even a digitized image.
Bit-oriented protocol is used between sender and receiver.
Because there are no beginning and end bits, the data transfer rate is quicker, but there's an increased possibility of errors occurring.
To resolve this, clocks need to be regularly resynchronized.

Error Classification, Detection, and Correction

Errors can be classified into three categories: Delay Distortion, Attenuation, and Noise.
Delay Distortion: signals at different frequencies travel at different speeds along the medium, causing signals to arrive at the destination at different times.
Attenuation: signal strength decreases over distance, and is higher at higher frequencies.
Noise: unwanted electromagnetic energy inserted during transmission.
Errors can be single-bit errors (a single bit of the data unit changes) or burst errors (multiple bits of a data unit change).

Error Detection

Checksum: a fixed-length data that is a result of performing a certain operation on data to be transmitted.
The sender computes the checksum, appends it to the data, and sends it to the receiver.
The receiver computes the checksum and compares it with the received checksum to detect errors.
Other error detection methods include Vertical Redundancy Check (parity check), Longitudinal Redundancy Check, and Cyclic Redundancy Check.

Multiplexing

Multiplexing divides the physical line or medium into logical segments called channels.
Different channels can carry data simultaneously over the same physical medium.
Hardware equipment called a multiplexer is used at the sender side to combine inputs from different sources and load them onto different channels of a medium.
There are two types of multiplexing: Frequency Division Multiplexing (FDM) and Time Division Multiplexing (TDM).

Frequency Division Multiplexing (FDM)

FDM is a technique used to divide the total bandwidth available in a communication medium into a series of non-overlapping frequency bands called channels.
Each channel is used to carry a separate signal.
FDM is used in analog telephone systems to carry multiple conversations over a single wire.

Time Division Multiplexing (TDM)

TDM is a technique used for digital transmission only.
In TDM, the transmission time is divided into a number of time slices, and each time slice is allotted to a different source node.
The source node which is sending data during its time slice can send data at a high rate.
There are two ways of allocating time slices: Synchronous TDM and Statistical TDM.

Digital Telephone Hierarchy

Digital Signal (DS) Service is a digital telephone hierarchy.
DS-0 is a single digital channel with a capacity of 64Kbps, which can carry one voice conversation.
Higher levels of the hierarchy include DS-1, DS-2, DS-3, and DS-4, which can carry multiple voice conversations simultaneously.

Wavelength Division Multiplexing (WDM)

WDM is a variation of FDM used for optical fiber transmission.
Multiple transmissions with different wavelengths are combined and sent together.
Individual transmissions are retrieved by filtering based on their wavelengths.

Error Recovery

Stop and Wait: a simple flow control method where the sender sends one frame at a time and waits for acknowledgment from the receiver.
Go-Back-N: a method where multiple frames are sent at a time, and the receiver sends a single acknowledgment for all the frames received.
Sliding Window: a method where multiple frames are sent at a time, and the receiver sends a single acknowledgment for all the frames received.### Sliding Window Protocol
In Sliding Window Protocol, the receiver sends an ACK containing the number of the next frame it expects to receive.
The sender's window shrinks from the left when frames are sent and expands to the right when ACKs are received.
The receiver's window shrinks from the left when frames are received and expands to the right when ACKs are sent.

Message Switching

Message switching is a network switching technique where data is routed in its entirety from the source node to the destination node, one hop at a time.
Every intermediate switch in the network stores the whole message before forwarding it to the next node.
Message switching reduces network congestion, allows messages of unlimited sizes, and does not have to deal with out-of-order packets or lost packets.
However, it introduces delay at each switching node, making it unsuitable for real-time applications.

Transmission Media

Transmission media are the physical infrastructure components that carry data from one node to another.
There are two main categories of transmission media: guided media and unguided media.
Guided media are based on physical cables, such as twisted pair wires, coaxial cables, and optical fibers.
Unguided media are wireless, such as cellular (mobile) telephones and satellite communication.

Guided Media

Twisted pair wires are commonly used in telephone systems and can carry both data and voice.
Unshielded Twisted Pair (UTP) is the most commonly used media, but it is prone to noise and crosstalk.
Shielded Twisted Pair (STP) has a metal shield that prevents penetration of electromagnetic noise and crosstalk.
Coaxial cables are commonly used by cable companies to carry cable transmissions and are more reliable and carry higher data rates than UTP.
Optical fibers transmit data in the form of light and are made up of glass fibers enclosed in a plastic jacket.

Optical Fiber

Optical fibers use reflection to guide the light through the fiber.
There are two types of optical fiber propagation: multimode and single mode.
Multimode fibers use LED light sources and have multiple beams of light that pass through the core of the fiber.
Single mode fibers use highly focused light beams and have a smaller core diameter than multimode fibers.

Cellular (Mobile) Telephones

The first mobile telephone was developed in 1946, but it was difficult to operate and had a single channel for both sending and receiving communication.
The second development, Improved Mobile Telephone System (IMTS), had a strong transmitter and used two frequencies for communication.
The third development, Advanced Mobile Phone System (AMTS), divided a large geographical area into small regions called cells.
Each cell has an antenna and cell office to control that cell, and all cells are controlled and coordinated by a Mobile Telephone Switching Office (MTSO).

Satellite Communication

A satellite is a physical object that revolves around the earth at a known height.
Satellites perform the function of an antenna and repeater together.
Ground stations are equipment installed on the earth's surface that enables communication over one or more satellites.
Geosynchronous satellites are used to move at the same revolution per minute as the earth and in the same direction, allowing for communication between any two parts of the world.
Three methods of communication using satellites are: Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA), and Code Division Multiple Access (CDMA).

Internetworking Devices

Internetworking devices are classified into three categories: Repeaters, Bridges, and Routers.
Repeaters regenerate a signal and work at the physical layer of the OSI model.
Bridges divide a big network into smaller sub-networks and operate at both the physical and data link layers.
Routers operate at the physical, data link, and network layers and are used to interconnect two or more networks.

Gateways

Gateways operate at all layers of the OSI model and are used to relay frames between different networks that use different protocols.
Gateways are capable of translating between frame formats and different protocols.
Gateways are very powerful computers compared to bridges and routers, typically used to connect huge networks.

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Description

Introduction to data communication and networking, including definitions of network and data communication, and the role of nodes in a network.