Network architecture lecture 3
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Questions and Answers

What is the primary function of a bridge in a network?

  • To generate new traffic and improve bandwidth
  • To amplify signal strength and extend distance
  • To connect multiple network segments and regulate traffic (correct)
  • To create additional network hops for data transmission

    • Which of the following accurately describes modern Ethernet networks compared to legacy Ethernet?

  • They transmit data over shared media at lower rates
  • They can only operate in half-duplex mode for efficiency
  • They require more physical distance due to lower speeds
  • They operate at significantly higher speeds with dedicated segments (correct)

    • What type of device can function as a repeater in a Wi-Fi network?

  • Ethernet switches
  • Network bridges
  • Active hubs (correct)
  • Routers with NAT capabilities

    • In switched Ethernet networks, what is a primary advantage over legacy Ethernet?

    <p>Each station has a dedicated segment instead of sharing bandwidth (A)</p> Signup and view all the answers

    What is one of the main benefits of self-healing networks?

    <p>They ensure reliability through multiple routing paths (C)</p> Signup and view all the answers

    What is the main purpose of the OSI Model?

    <p>To standardize functions of a communications system in layers. (D)</p> Signup and view all the answers

    Which layers of the OSI Model are primarily implemented in software?

    <p>Application and Presentation layers. (B)</p> Signup and view all the answers

    What does each layer in the OSI Model do in relation to the other layers?

    <p>A layer serves the layer below it and is served by the layer above it. (B)</p> Signup and view all the answers

    Which aspect of network management is improved by the layered architecture of the OSI Model?

    <p>Debugging of network applications becomes easier. (A)</p> Signup and view all the answers

    Which of the following statements about network layers is true?

    <p>Each layer has protocols that dictate data exchange formats. (A)</p> Signup and view all the answers

    How does the OSI Model enhance communication between end users?

    <p>By facilitating interaction among application layer processes. (A)</p> Signup and view all the answers

    Which of the following best describes the lower layers of the OSI Model?

    <p>They handle data transport and are often implemented in hardware. (C)</p> Signup and view all the answers

    What defines a Local Area Network (LAN)?

    <p>It connects many devices in close proximity. (C)</p> Signup and view all the answers

    What distinguishes Wide Area Networks (WAN) from Local Area Networks (LAN)?

    <p>WANs connect devices over large distances. (B)</p> Signup and view all the answers

    What was the original data rate of the first Ethernet network developed in the 1970s?

    <p>3 Mbps (B)</p> Signup and view all the answers

    Which protocol was used in the original Ethernet for managing network traffic?

    <p>Carrier Sense Multiple Access (CSMA/CD) (C)</p> Signup and view all the answers

    What major advancement has improved the speed and reliability of WAN technologies?

    <p>Fiber optic cables (B)</p> Signup and view all the answers

    Which invention did the original Ethernet network use?

    <p>Coaxial cable (D)</p> Signup and view all the answers

    What is the significance of Ethernet (IEEE 802.x) in networking?

    <p>It is the most popular network technology worldwide. (C)</p> Signup and view all the answers

    Who were the collaborators that led to the development of the 10-Mbps Ethernet Version 1.0 specification?

    <p>Digital Equipment Corporation, DEC, and Xerox (C)</p> Signup and view all the answers

    Which one of the following is NOT a layer in the OSI model?

    <p>Command Layer (D)</p> Signup and view all the answers

    What is the original function of an Ethernet network?

    <p>To allow communication over a single shared cable among devices (B)</p> Signup and view all the answers

    What modern technology is NOT typically associated with Ethernet networks?

    <p>Dial-up telephone lines (D)</p> Signup and view all the answers

    What is the purpose of protocols in networking?

    <p>To establish rules for communication between devices (C)</p> Signup and view all the answers

    Which of the following describes an Ethernet segment?

    <p>A single shared medium for network communication (A)</p> Signup and view all the answers

    What essential components must an Ethernet frame contain?

    <p>Source and destination addresses, along with mandatory information (C)</p> Signup and view all the answers

    Which factor contributes to the increasing demand for local area networks?

    <p>Cost savings from sharing information and resources (D)</p> Signup and view all the answers

    What type of cabling was historically used for Ethernet devices?

    <p>Coaxial copper cable (C)</p> Signup and view all the answers

    In the context of Ethernet, what does the term 'node' refer to?

    <p>Any device attached to the shared medium (C)</p> Signup and view all the answers

    Which of the following motivations for local area networking focuses on enhancing security?

    <p>Improving organizational security (A)</p> Signup and view all the answers

    Which medium is currently more commonly used in Ethernet compared to historical usage?

    <p>Fibre optic cabling (D)</p> Signup and view all the answers

    What is the main issue with connecting too many devices to a single segment in a CSMA/CD network?

    <p>Increased contention for the medium (B)</p> Signup and view all the answers

    In a ring topology, what role does the token play during data transmission?

    <p>It allows a workstation to send data when it is seized. (D)</p> Signup and view all the answers

    After a workstation sends a message in a ring topology, what happens to the token?

    <p>It is changed back to 0. (D)</p> Signup and view all the answers

    What is a characteristic of mesh topology in networking?

    <p>Nodes collaborate to disseminate data to the entire network. (C)</p> Signup and view all the answers

    In a star topology, how is data transmitted between devices?

    <p>Through a centralized digital switch. (A)</p> Signup and view all the answers

    What type of cable can be used in the ring topology media?

    <p>Twisted pair, coaxial cable, or optical fibre (B)</p> Signup and view all the answers

    When a workstation recognizes the data intended for it in a ring topology, what action does it take?

    <p>It copies the message and changes the token to 0. (B)</p> Signup and view all the answers

    What is one advantage of using a mesh topology?

    <p>Improved redundancy and reliability. (B)</p> Signup and view all the answers

    Which topology utilizes a digital switch for data transmission?

    <p>Star Topology (A)</p> Signup and view all the answers

    What occurs when the frame returns to the originator in a ring network after carrying a message?

    <p>The originator checks the token and removes the message. (C)</p> Signup and view all the answers

    What is the primary benefit of the layered architecture in the OSI Model?

    <p>It simplifies the network design. (A)</p> Signup and view all the answers

    Which OSI layer primarily deals with user application interactions?

    <p>Application Layer (D)</p> Signup and view all the answers

    Which of the following layers in the OSI Model is primarily responsible for data transport?

    <p>Physical Layer (D)</p> Signup and view all the answers

    What is the relationship between the layers in the OSI Model?

    <p>A layer serves the layer above it and is served by the layer below it. (A)</p> Signup and view all the answers

    Why is network management considered easier in a layered architecture?

    <p>It allows issues to be isolated within a specific layer. (D)</p> Signup and view all the answers

    Which statement best describes the upper layers of the OSI Model?

    <p>They handle application issues and are generally implemented only in software. (A)</p> Signup and view all the answers

    What best describes the function of protocols within the OSI Model?

    <p>Protocols define formats for data exchange and the controls for communication. (D)</p> Signup and view all the answers

    What is the historical medium used for Ethernet communication?

    <p>Coaxial copper cable (A)</p> Signup and view all the answers

    What do nodes in an Ethernet network refer to?

    <p>Devices attached to the shared medium (B)</p> Signup and view all the answers

    Which of the following best defines an Ethernet frame?

    <p>A variable-sized chunk of information for communication (D)</p> Signup and view all the answers

    Which factor contributes to the enhancement of information exchange in local area networks?

    <p>Automation of communication (D)</p> Signup and view all the answers

    What primary advantage does Ethernet provide regarding the addition of devices?

    <p>No modifications are needed for existing devices (D)</p> Signup and view all the answers

    What modern technology is commonly used alongside current Ethernet standards?

    <p>Fiber optics (C)</p> Signup and view all the answers

    Which of the following best describes the term 'segment' in Ethernet networking?

    <p>A shared medium for communication (B)</p> Signup and view all the answers

    What significant benefit does a local area network provide to organizations?

    <p>Decreased costs by centralizing resources (A)</p> Signup and view all the answers

    What is a primary advantage of peer-to-peer networking?

    <p>Quick resource sharing (B)</p> Signup and view all the answers

    What is a key characteristic of client/server networking?

    <p>All resources are centralized on a single server (C)</p> Signup and view all the answers

    What does CSMA/CD stand for in networking terms?

    <p>Carrier-Sense Multiple Access with Collision Detection (D)</p> Signup and view all the answers

    Which of the following represents a disadvantage of traditional Ethernet?

    <p>Electrical interference affecting signals (A)</p> Signup and view all the answers

    How does a server in client/server networking improve data integrity?

    <p>By saving the most current version of documents in one location (A)</p> Signup and view all the answers

    In a peer-to-peer network, how do users access each other's resources?

    <p>Directly without the need for an intermediary (C)</p> Signup and view all the answers

    What results from a collision in a CSMA/CD network?

    <p>The transmission returns in a garbled form (D)</p> Signup and view all the answers

    What is a limitation when using traditional Ethernet regarding network diameter?

    <p>Cables must be kept short for signal clarity (C)</p> Signup and view all the answers

    How can attenuation negatively impact an Ethernet network?

    <p>Weakens electrical signals over long cable runs (B)</p> Signup and view all the answers

    What role does a network operating system serve in client/server networking?

    <p>Centralizes control and management of resources (D)</p> Signup and view all the answers

    What role does the cladding play in a fiber optic cable?

    <p>It surrounds the core and affects total internal reflection. (A)</p> Signup and view all the answers

    Which of the following statements is true regarding single mode fiber optics?

    <p>It is suitable for longer distances with higher bandwidth. (C)</p> Signup and view all the answers

    What is a significant disadvantage of fiber optic cables?

    <p>They are expensive to maintain and require special tools for termination. (D)</p> Signup and view all the answers

    What typically causes attenuation in fiber optic cables?

    <p>Impurities in the material and absorption at certain frequencies. (D)</p> Signup and view all the answers

    Which diameter range is typical for the core of fiber optic cables?

    <p>50 to 500 nm (B)</p> Signup and view all the answers

    What is the main limitation of using CSMA/CD in a network?

    <p>There is a practical limit to the number of devices that can coexist. (A)</p> Signup and view all the answers

    In a ring topology, what happens when a workstation identifies a frame destined for it?

    <p>It copies the data and changes the token back to 0. (A)</p> Signup and view all the answers

    What initial condition allows a workstation to send a message in a ring topology?

    <p>There has to be an empty information frame circulating. (D)</p> Signup and view all the answers

    Which type of topology allows each node to serve as a relay for other nodes?

    <p>Mesh Topology (C)</p> Signup and view all the answers

    What is the first action performed by a workstation that wants to send data in a ring topology?

    <p>It seizes the token and sets it to 1. (A)</p> Signup and view all the answers

    In which scenario does contention increase significantly in a CSMA/CD network?

    <p>When devices continuously send data without waiting. (A)</p> Signup and view all the answers

    Which of the following best describes the role of the token in a token ring network?

    <p>It indicates which workstation can send data. (A)</p> Signup and view all the answers

    How does a star topology facilitate data transmission?

    <p>A digital switch centrally manages data transfer. (D)</p> Signup and view all the answers

    What type of media can be used in a ring topology?

    <p>Twisted pair, coaxial cable, or optical fiber (A)</p> Signup and view all the answers

    What is a characteristic of data frame circulation in ring topology?

    <p>Data frames travel in only one direction. (A)</p> Signup and view all the answers

    Study Notes

    International & Access Foundation Programmes

    • Computer Science Module, Semester 2, Part 4
    • Topic: Networks - OSI model and Ethernet
    • Lecturer: Nevan Bermingham

    The OSI Model

    • The Open Systems Interconnection (OSI) model is a standardization effort by the International Organization for Standardization.
    • It standardizes communications system functions through abstraction layers.
    • Similar communication functions are grouped into logical layers.
    • Each layer serves the layer above and is served by the layer below.
    • Most modern network communication protocols are based on the OSI model.
    • The lecture will cover Ethernet and IP locations in the OSI model and the modern GSM mobile network.
    • Layer architecture simplifies network design.
    • Network applications are easier to debug in a layered architecture.
    • Network management is simplified through layered architecture.
    • Network layers operate according to a set of rules (protocols).
    • Protocols define data exchange format, control, and timing for layer communication.

    Upper Layers of the OSI Model

    • The upper layers deal with application issues and are mostly implemented in software.
    • It's the layer closest to the end user, handling communications between users through application layer processes.
    • Example tasks include application issues, e-mail, file transfer, and client-server interactions.

    Lower Layers of the OSI Model

    • Handles Data Transport, Physical, and Data Link Layers
    • Typically implemented in hardware and software.

    OSI Model Layers

    • Application: Network process to application. Data Representation and Encryption.
    • Presentation: Data representation and encryption
    • Session: Interhost communication
    • Transport: End-to-End Connections and Reliability
    • Network: Path Determination and IP Logical Addressing
    • Data Link: MAC and LLC (Physical Addressing)
    • Physical: Media, Signal, and Binary Transmission

    Ethernet (IEEE 802.x)

    • Originated in the 1970s as an experimental coaxial cable network by Xerox.
    • Initial data rate: 3 Mbps.
    • Used a carrier sense multiple access/collision detection (CSMA/CD) protocol.
    • Became popular and widely deployed globally.
    • Modern Ethernet uses fiber optics, satellite, and microwave point-to-point communications.
    • Ethernet communication occurs over a single cable shared by all devices.
    • Devices can communicate with any other device on the network without modification.

    LAN's & WAN's

    • Local Area Network (LAN): Connects devices within a building.
    • Wide Area Network (WAN): Connects devices across distances.
    • WANs often use dedicated lines leased from telephone companies.
    • Ethernet utilises technologies like fibre optics, satellite, and microwave for extending range and improving speed and reliability.

    Ethernet Hubs and Switches

    • Ethernet hubs provide a central connection point for devices.
    • Ethernet switches, unlike hubs, create a dedicated segment for each device, reducing collisions and improving network performance.

    Networking

    • Networking allows sharing information between multiple computers.
    • The internet is a large example, but smaller networks are also vital.
    • Libraries use computer terminals instead of card catalogs for quick and easy access.

    Types of Network Topologies

    • Bus Topology: All devices connect to a common medium. Collisions can occur if multiple devices transmit simultaneously. The most traditional Ethernet topology.
    • Ring Topology: Stations connect in a ring, with data transmitted through the ring. Each station copies the data and transfers it to the next until it gets to its destination. Token ring is an example of this type.
    • Star Topology: Devices connect to a central switch or hub. Each communication goes through the central hub which decides to which device the data should go to.
    • Mesh Topology: Each device connects to several other devices, increasing reliability, although installation requires more work and has a higher cost. Often seen in wireless scenarios.
    • Wireless Topology: Wireless connections to other devices, using the electromagnetic spectrum.

    Network Design

    • Peer-to-Peer: All computers are equal, directly sharing resources.
    • Client-Server: Centralized server manages data, security, and resources.

    Transmission Mediums (Definition)

    • Transmission media are the physical pathways that connect devices on a network.
    • Examples include:
      • Twisted pair
      • Coaxial cable
      • Fiber optic cable
      • Microwave
      • Infrared
      • Satellite.

    Transmission Mediums (Types)

    • Bound Media: Twisted pair, Co-axial cables, Fiber optic. Transmit signals within a physical means
    • Unbound Mediums: Microwaves, Infrared, Satellite. Transmit signals through the air or via other signals.

    Modulation

    • Modulation involves combining data signals with a higher-frequency carrier signal, to transmit the signal.
    • This facilitates signal transmission over longer distances, and through different media.
    • Types include: -Amplitude modulation
      • Frequency modulation
      • Digital modulation
    • Methods such as phase-shift keying (PSK) and frequency-shift keying (FSK).

    Modem, Cable, and Fibre-optic Technologies

    • Modem transfers digital data over telephone or cable lines.
    • Cable lines used for broadband internet, televisions.
    • Fiber optic uses light pulses to carry data over long distances with high bandwidth.

    Ethernet Switches, Repeaters, and Bridges

    • Switches manage traffic between network segments, enabling more efficient data transfer compared to hubs.
    • Repeaters boost the signal for longer transmission distances.
    • Bridges interconnect different network segments.

    Disadvantages of Ethernet

    • Distance limitations due to signal attenuation.
    • Interference.

    Advantages of Fiber-optics

    • High Bandwidth, non-flamable, light-weight, no electromagnetic interference.

    Applications for these Mediums

    • Microwave point-to-point, common for long-distance communication links like tv and radio broadcasting.
    • Infrared is often used for short-range communication.
    • Satellites can create interconnections for high capacity communication across countries.

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