Computer Networks and Applications
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Questions and Answers

What is an advantage of the peer-to-peer architecture?

  • Scalability is limited by the number of servers.
  • Only one device can act as a server.
  • The architecture is simpler to manage.
  • New peers bring new service capacity as well as new service demands. (correct)

    • What is a characteristic of the client-server paradigm in the Application Layer?

  • Peers request service from other peers and provide service in return.
  • Clients communicate directly with each other.
  • Servers have permanent IP addresses and are always-on hosts. (correct)
  • Servers are intermittently connected and have dynamic IP addresses.

    • What is the function of a socket in the Application Layer?

  • It is a program that runs on a host.
  • It is a door through which a process sends and receives messages. (correct)
  • It is a network-core device.
  • It is a device that connects to the Internet.

    • What is necessary for a process to receive messages in the Application Layer?

    <p>The process must have a socket.</p> Signup and view all the answers

    What is an example of an Application Layer protocol that uses the client-server paradigm?

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

    What is the purpose of inter-process communication in the Application Layer?

    <p>To enable communication between processes running on the same host.</p> Signup and view all the answers

    What is a characteristic of the process that initiates communication in the Application Layer?

    <p>It is a client process that initiates communication.</p> Signup and view all the answers

    Why do processes need identifiers in the Application Layer?

    <p>Because many processes can be running on the same host.</p> Signup and view all the answers

    What does an application-layer protocol define?

    <p>Types of messages exchanged and rules for sending them</p> Signup and view all the answers

    What is an example of a proprietary protocol?

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

    Which transport service requirement is critical for web transactions?

    <p>Data integrity</p> Signup and view all the answers

    Which of the following is true about message semantics in an application-layer protocol?

    <p>It deals with the meaning of information in message fields</p> Signup and view all the answers

    What do open protocols provide to ensure interoperability?

    <p>Access to protocol definitions through RFCs</p> Signup and view all the answers

    Which port number is typically associated with mail servers?

    <p>25</p> Signup and view all the answers

    Study Notes

    Application Development and Communication

    • Applications run on end systems and communicate over networks, e.g., web servers interact with browser software.
    • Network-core devices do not host user applications; they support communication between end systems.

    Client-Server Paradigm

    • Servers are always-on hosts, typically located in data centers, and possess permanent IP addresses.
    • Clients initiate communication with servers, may have dynamic IP addresses, and are often intermittently connected.
    • Communication occurs via protocols like HTTP, IMAP, and FTP; clients do not communicate directly with each other.

    Peer-to-Peer Architecture

    • In peer-to-peer networks, there is no constant server; end systems communicate directly.
    • Peers can provide and request services, leading to self-scalability as new peers join.
    • Peer connections can be intermittent, complicating management; commonly used in P2P file-sharing systems.

    Processes and Communication

    • A process is a program executing within a host, communicating through inter-process communication (IPC) within the same host or via message exchange across different hosts.
    • Peer architectures incorporate both client and server processes, enabling direct communication.

    Sockets

    • A socket is used by processes to send and receive messages, acting as an interface for communications.
    • A sending process pushes a message out through the socket, which relies on the transport infrastructure for delivery to the receiving process's socket.
    • Each socket is controlled by the application developer and the operating system.

    Addressing Processes

    • To receive messages, processes must have unique identifiers; a host has a 32-bit IP address.
    • An identifier includes both the IP address and associated port numbers (e.g., HTTP server uses port 80, mail server uses port 25).
    • For example, to send a message to a web server, both the IP address and port number must be specified.

    Application-Layer Protocols

    • Application-layer protocols define message types, delineation of fields, message semantics, and rules for sending/response behavior.
    • Protocols can be open (defined in RFCs, promoting interoperability) like HTTP or proprietary (e.g., Skype, Zoom).

    Transport Service Requirements

    • Applications have varying demands for data integrity; some require 100% reliable transfer (e.g., file transfers, web transactions), while others like audio can tolerate some losses.
    • Applications may also have specific timing requirements, impacting the choice of transport service.

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    Description

    This quiz covers the basics of computer networks, including network architecture, communication protocols, and application development. It also touches on the concepts of end systems, network-core devices, and ISP roles.

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