Data Communications Fundamentals
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Data communications is the exchange of data between two devices via some form of transmission medium such as via ______.

wire cable

The four fundamental characteristics that affect the effectiveness of data communication are delivery, accuracy, timeliness, and ______.

jitter

The ______ is the device that sends the data message.

sender

In a simplex data flow, communication is ______, as on a one-way street.

<p>unidirectional</p> Signup and view all the answers

In a half duplex system, each station can both transmit and receive, but not at the ______.

<p>same time</p> Signup and view all the answers

A ______ is defined as a set of nodes connected by communication links.

<p>network</p> Signup and view all the answers

Distributed processing is when a task is divided among multiple ______.

<p>computers</p> Signup and view all the answers

Performance of a network is measured in various ______.

<p>criteria</p> Signup and view all the answers

The physical layer is responsible for movements of individual bits from one node to the next, dealing with physical characteristics of interfaces and media, as well as the representation of ______.

<p>bits</p> Signup and view all the answers

The data link layer is responsible for moving ______ from one node to the next.

<p>frames</p> Signup and view all the answers

The network layer is responsible for the delivery of individual ______ from the source host to the destination host.

<p>packets</p> Signup and view all the answers

The transport layer is responsible for the delivery of a ______ from one process to another.

<p>message</p> Signup and view all the answers

The session layer establishes, maintains and synchronizes the ______ between communicating systems.

<p>interaction</p> Signup and view all the answers

The presentation layer is responsible for translation, compression, and ______.

<p>encryption</p> Signup and view all the answers

The application layer provides services to the ______.

<p>user</p> Signup and view all the answers

In the OSI model, changes in one layer should not require changes in ______ layers.

<p>other</p> Signup and view all the answers

A ______ is used to filter traffic on the network and minimize collisions.

<p>bridge</p> Signup and view all the answers

Bridges operate at the ______ layer of the OSI model.

<p>data link</p> Signup and view all the answers

A bridge reads the destination address of a packet to determine if it should ______ or filter it.

<p>forward</p> Signup and view all the answers

When traffic becomes too heavy between segments, a bridge can become a ______.

<p>bottleneck</p> Signup and view all the answers

The ______ Protocol is used to prevent looping within a network topology.

<p>Spanning Tree</p> Signup and view all the answers

A ______ is a backup route that ensures continuous data flow if the primary path fails.

<p>redundant path</p> Signup and view all the answers

A loop occurs when data circulates along redundant paths, leading to a ______ storm.

<p>broadcast</p> Signup and view all the answers

In a spanning tree protocol, a ______ Bridge is chosen as the main reference point for the network.

<p>Root</p> Signup and view all the answers

Bridges use physical addresses known as ______ to make data forwarding decisions.

<p>MAC addresses</p> Signup and view all the answers

Transmission media is a physical medium through which data is transmitted from one device to another within a ______.

<p>network</p> Signup and view all the answers

Conducted or guided media use a ______ such as a wire or fiber optic cable to move the signal.

<p>conductor</p> Signup and view all the answers

______ media use radio waves of different frequencies and do not require a wired connection.

<p>Wireless</p> Signup and view all the answers

Transmission impairments limit the ______ a signal can travel.

<p>distance</p> Signup and view all the answers

Twisted pair wires consist of two insulated copper wires arranged in a regular ______ pattern.

<p>spiral</p> Signup and view all the answers

The pair in a shielded twisted pair (STP) is wrapped with ______ foil or braid for insulation.

<p>metallic</p> Signup and view all the answers

Category 5 UTP cables can achieve data rates of up to ______ mbps.

<p>100</p> Signup and view all the answers

Coaxial cables are used for cable television, LANs, and ______.

<p>telephone</p> Signup and view all the answers

For digital signals, repeaters are needed every ______ kilometers.

<p>2-3</p> Signup and view all the answers

Fiber optic cables require a light source such as an injection laser diode or ______.

<p>LED</p> Signup and view all the answers

One advantage of fiber optic cables is their ______ to environmental interference.

<p>immunity</p> Signup and view all the answers

Coaxial cables have a bandwidth of ______ to 600MHz.

<p>400</p> Signup and view all the answers

A disadvantage of fiber optic cables is that they can be ______ over short distances.

<p>expensive</p> Signup and view all the answers

Wireless transmission uses ______ for both transmission and reception.

<p>antennas</p> Signup and view all the answers

Single mode fiber guides light down the center of an extremely narrow ______.

<p>core</p> Signup and view all the answers

Microwave transmission requires an unobstructed line of sight between the source and the ______.

<p>receiver</p> Signup and view all the answers

Satellite microwave transmission involves a microwave relay station in ______.

<p>space</p> Signup and view all the answers

The ______ band is known for experiencing major rain interference.

<p>Ku</p> Signup and view all the answers

In satellite communication, earth stations send signals to the satellite on an ______.

<p>uplink</p> Signup and view all the answers

A significant disadvantage of microwave transmission is the requirement for ______ towers and repeaters.

<p>expensive</p> Signup and view all the answers

Geostationary satellites remain above the equator at a height of ______ miles.

<p>22,300</p> Signup and view all the answers

Optical communication uses ______ rays as a medium for propagation.

<p>light</p> Signup and view all the answers

The first designated satellite transmission band is called the ______ band.

<p>C</p> Signup and view all the answers

Flashcards

Data Communications

The exchange of data between two devices using a transmission medium like wires.

Communication System

A combination of hardware (physical equipment) and software (programs) that enables data communication.

Delivery

Data must reach the intended destination.

Accuracy

Data must be transmitted without errors.

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Timeliness

Data must be delivered within a reasonable time.

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Simplex Data Flow

Communication is one-way, like a TV broadcast.

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Half Duplex

Communication is two-way but not simultaneously, like a walkie-talkie.

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Full Duplex

Communication is two-way and simultaneous, like a phone conversation.

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Physical Layer

Handles the physical transmission of bits between network devices. It deals with the electrical, mechanical, and procedural aspects of data transfer.

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Data Link Layer

Provides reliable data transfer between adjacent network devices. It deals with framing, addressing, error control, and flow control.

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Network Layer

Responsible for routing data packets across the network. It handles logical addressing and determines the best path for data to travel.

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Transport Layer

Provides reliable end-to-end connection between applications on different hosts. It handles segmentation, reassembly, and connection control.

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Session Layer

Manages communication sessions between applications on different hosts. It deals with dialog control and checkpoints.

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Presentation Layer

Handles data presentation formats. It deals with translation, encryption, and compression.

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Application Layer

Provides services to users. It handles network access, file transfer, email, and other application-level tasks.

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Layered Model

A communication architecture that divides network functionality into distinct layers, each with its own responsibilities. Each layer relies on the next lower layer for basic services.

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Bridge

A networking device that connects different network segments (LANs) and forwards data based on destination addresses. It filters unwanted traffic and reduces collisions.

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Bridge Functions

Bridges perform actions to manage data flow, including:

  • Controls broadcast: Restricts network-wide broadcasts to specific segments.
  • Maintains address tables: Stores information about connected devices to make forwarding decisions.
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Transparent Bridge

A type of bridge that operates invisibly to network devices. It filters and forwards data without interrupting the flow between connected segments.

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Spanning Tree Protocol (STP)

A Layer 2 protocol that prevents data looping within a network by blocking redundant paths. It ensures seamless data flow even with multiple paths.

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Redundant Path

A backup route in a network that allows data to flow even if the primary path fails. While useful, it can cause looping problems.

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Loop (Network)

A condition where data travels endlessly on redundant paths in a network, creating a broadcast storm and impacting network performance.

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Root Bridge

The central bridge in a network that determines the shortest paths for data flow. All other bridges rely on the root bridge for decisions.

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Bridge Protocol Data Units (BPDUs)

Special messages exchanged between bridges to establish connections and determine the root bridge. They contain information about paths and network configuration.

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Transmission Media

The physical path that carries data signals between network devices. Think of it as the 'road' for data to travel.

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Conducted Media

Transmission media that uses physical wires or cables (like copper or fiber optic) to transmit data.

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Wireless Media

Transmission media that uses radio waves to transmit data without physical connections.

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Bandwidth

The range of frequencies a transmission medium can carry, directly impacting the amount of data that can be transmitted per unit of time.

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Twisted Pair Wires

Consists of two insulated copper wires twisted together to reduce electromagnetic interference.

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Shielded Twisted Pair (STP)

Twisted pair wires with metallic shielding to further reduce electromagnetic interference.

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Unshielded Twisted Pair (UTP)

Twisted pair wires without metallic shielding, more affordable but less protected from interference.

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Category 5 UTP

A type of UTP cable providing higher data rates (up to 100 Mbps) due to tighter twisting and better performance.

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Coaxial Cable (COAX)

A type of cable commonly used for cable television, LANs, and telephones. It consists of an inner conductor surrounded by a braided mesh, both sharing a common center axial.

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Coaxial Cable Layers

Coaxial cables have several layers: an inner conductor, an insulator, a braided shield, a dielectric material, and an outer jacket. These layers provide electrical insulation, shielding from interference, and physical protection.

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Fiber Optic Cable

A type of cable that transmits data using light pulses through thin strands of glass or plastic. It's known for its high bandwidth, low attenuation, and immunity to interference.

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Fiber Optic Signal Types

There are three main types of fiber optic signals: multimode step-index fiber, multimode graded-index fiber, and single mode fiber. Each type differs in its light propagation and bandwidth capabilities.

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Wireless (Unguided Media) Transmission

Transmission and reception of data through radio waves or other electromagnetic waves without physical cables. Antennas are used to transmit and receive signals.

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Terrestrial Microwave

A type of wireless communication that transmits data using microwave signals over ground-based antennas. It is often used for long-distance communication.

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Satellite Microwave

A type of wireless communication that uses microwave signals to transmit data between satellites and ground stations. It's commonly used for global communication and broadcasting.

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Broadcast Radio

A type of wireless communication that transmits audio signals over radio waves, allowing anyone with a receiver to tune in to a specific station.

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Line of Sight Requirement

A limitation of terrestrial microwave communication where a direct, unobstructed path between the transmitter and receiver is necessary for signal transmission.

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Satellite Microwave Transmission

A form of wireless communication where signals are relayed through satellites orbiting Earth, enabling communication over vast distances.

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Geostationary Satellite

A satellite positioned at a specific altitude above the equator, orbiting at the same speed as the Earth's rotation, appearing stationary from Earth.

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Uplink and Downlink

Communication pathways for satellite transmission: Uplink - transmitting signals from Earth to a satellite, Downlink - transmitting signals from a satellite back to Earth.

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C Band

One of the principal satellite transmission bands, used for communication, with a frequency range of 4 to 6 GHz (downlink) and 6 to 8 GHz (uplink).

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Ku Band

A commonly used satellite transmission band, operating in the 12 to 14 GHz (downlink) and 14 to 18 GHz (uplink) range, known for its susceptibility to rain interference.

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Ka Band

A higher frequency satellite transmission band (19 to 29 GHz downlink and 29 to 31 GHz uplink), offering higher bandwidth but requiring more expensive equipment.

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Study Notes

Data Communications

  • Data communications is the exchange of data between two devices via a transmission medium like wire cable.
  • Communication systems consist of hardware and software components.
  • Key characteristics affecting data communication effectiveness include delivery, accuracy, timeliness, and jitter (variation in packet arrival time).
  • Components of a data communication system include message, sender, receiver, and transmission medium (e.g., twisted-pair wire, coaxial cable, fiber-optic cable).

Data Representation

  • Text is represented as a bit pattern (sequence of 0s and 1s).
  • Numbers are also represented by bit patterns.
  • Images are composed of pixels (picture elements).
  • Pixel size depends on image resolution.

Data Flow

  • Simplex: unidirectional data flow (e.g., keyboard to monitor).
  • Half-duplex: both devices can transmit but not simultaneously (e.g., walkie-talkies).
  • Full-duplex: both devices transmit and receive simultaneously (e.g., telephone networks).

Networks

  • A network is a collection of nodes (devices) connected by communication links (e.g., computers, printers).
  • Distributed processing is when tasks are distributed among multiple computers.
  • Network performance is measured by factors such as number of users, hardware capabilities, transmission medium type, and software efficiency.
  • Reliability is determined by failure frequency, recovery time, and robustness.
  • Network security is maintained through protecting data from unauthorized access, damage, and losses.

Physical Structures

  • A link is a communications pathway for data transfer between devices.
  • Point-to-point links provide a dedicated link between two devices.
  • Multipoint (multidrop) links share a link between multiple devices (spatially or temporarily).
  • Topology: the geometric representation of connections between devices in a network.
  • Different topologies exist: Mesh, Star, Bus, Ring, Tree, and Hybrid.

Network Models

  • OSI model is a seven-layered architecture for network communication.

  • Internet model is a five-layered architecture for network communication.

  • Network categories include LANs (local), MANs (metropolitan), and WANs (wide area).

  • IP (Internet Protocol) is used for addressing hosts on a network.

  • IPV4 and IPV6 are different versions of the Internet Protocol.

  • Standards like the OSI model are used for communication in networks.

Protocols and Standards

  • Protocols are sets of rules governing data communication.
  • Key protocol elements include syntax, semantics, and timing.
  • Standards ensure compatibility between network devices.
  • Standards organizations like ISO define and implement these protocols.

Transmission Media

  • Transmission media is the physical pathway for data transmission in a network (wired or wireless).
  • Wired media use physical conductors, while wireless media use radio waves.
  • Factors like bandwidth, transmission impairments, and the number of receivers influence transmission capacity.
  • Common examples of guided media include twisted-pair cable, coaxial cable, and fiber-optic cable.
  • Wireless media include radio and infrared.

Error Detection and Correction

  • Errors occur if the receiver's information doesn't match the sender's.
  • Single-bit errors occur when a single bit is altered during transmission.
  • Multiple-bit errors occur when more than one bit is altered.
  • Burst errors occur when multiple consecutive bits are altered.
  • Error detection methods ensure reliable data transmission (parity check, checksum, CRC).

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Final Exam Summary PDF

Description

Test your knowledge on the key concepts of data communications including characteristics, flow types, and network layers. This quiz covers essential terminology and principles that govern the exchange of data between devices. Challenge yourself and enhance your understanding of how data communication systems operate.

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