Application Layer Protocols MCQ Quiz - Objective Question with Answer for Application Layer Protocols - Download Free PDF

Microsoft Azure is a cloud computing service created by Microsoft for building, deploying, and managing applications and services through a global network of Microsoft-managed data centers.

Explanation:

DNS uses TCP for zone exchanges between servers and UDP when a client is trying to resolve a hostname to an IP address.

1. The Domain Name System (DNS) is the phonebook of the Internet. Humans access information online through domain names, like nytimes.com or espn.com. Web browsers interact through Internet Protocol (IP) addresses. DNS translates domain names to IP addresses so browsers can load Internet resources.

2. Each device connected to the Internet has a unique IP address that other machines use to find the device. DNS servers eliminate the need for humans to memorize IP addresses such as 192.168.1.1 (in IPv4), or more complex newer alphanumeric IP addresses such as 2400:cb00:2048:1::c629:d7a2 (in IPv6).

Working of DNS:

• When a user types a human-readable address into the browser, the operating system’s DNS client will check for information in a local cache. If the requested address isn’t there, it will look for a Domain Name System server in the local area network (LAN). When the local DNS server receives the query, and the requested domain name is found, it will return the result.
• If the name is not found, the local server will forward the query to a DNS cache server, often provided by the Internet Service Provider (ISP). Since the DNS server’s cache contains a temporary store of DNS records, it will quickly respond to requests. These DNS cache servers are called not authoritative DNS servers as they provide request resolution based in a cached value acquired from authoritative DNS servers.

Confusion Points

Some Standard books say that DNS uses UDP only, But in implementation DNS also using TCP as well.

The correct answer is Option 2) HTTP.

Key Points

• HTTP (HyperText Transfer Protocol) is the protocol that governs how data is transmitted between a web browser (client) and a web server.
• It defines:
  • How requests (like GET, POST) are made by the browser to the server
  • How the server responds with status codes (200 OK, 404 Not Found, etc.) and content (HTML, CSS, JS, JSON)
  • The structure and format of the request and response messages
• HTTP is a stateless, application-layer protocol built on top of TCP/IP.
• Modern web traffic often uses HTTPS, which is HTTP over an encrypted TLS/SSL connection.

Additional Information

• Option 1 – HTML: A markup language used to structure content on web pages, not for communication protocols.
• Option 3 – URL (Uniform Resource Locator): Specifies the address of a resource on the internet, not the communication mechanism.
• Option 4 – XML: A markup language for storing and transporting data; it does not define how communication occurs.
• Common HTTP Methods:
  • GET – Retrieve data
  • POST – Submit data to the server
  • PUT – Update a resource
  • DELETE – Remove a resource

The correct answer is Option 3) Sockets.

Key Points

• Sockets are the most commonly used method for inter-process communication (IPC) over a network.
• A socket provides an endpoint for sending and receiving data across a network using standard protocols like TCP or UDP.
• They allow client-server models to exchange data between applications on the same system or across different systems via IP addresses and port numbers.
• Each socket is identified by a combination of IP address and port number, enabling reliable bidirectional communication.

Additional Information

• Option 1 – Named pipe: Used for IPC on the same machine; not typically used for network communication.
• Option 2 – Semaphore: Used for synchronization, not for data communication between client and server.
• Option 4 – Message queuing: Suitable for asynchronous communication but less common for real-time client-server networking.
• Socket Types:
  • TCP Socket: Reliable, connection-oriented
  • UDP Socket: Unreliable, connectionless
• Common Use Cases: Web browsers, email servers, FTP, online chat applications

Explanation:

SNMP Agent Communication with SNMP Manager

Definition: The Simple Network Management Protocol (SNMP) is a protocol used for network management. It allows network administrators to manage network performance, find and solve network problems, and plan for network growth. An SNMP-managed network consists of three key components: managed devices, agents, and a network management system (NMS). The SNMP agent is software that resides on a managed device, such as a router, switch, or server, and communicates with the SNMP manager, which is part of the NMS.

Working Principle: The SNMP agent collects data from the managed device it resides on and makes this data available to the SNMP manager upon request. The primary method by which the SNMP agent communicates with the SNMP manager is through responding to GET and SET requests. These requests allow the SNMP manager to query the agent for information (GET) or modify the configuration (SET).

Advantages:

• Enables centralized network management, allowing administrators to monitor and control multiple devices from a single location.
• Supports proactive network management by providing real-time data on network performance and issues.
• Allows for automation of network management tasks, reducing the need for manual intervention.

Disadvantages:

• Security vulnerabilities if not properly configured, as SNMP data can be intercepted if transmitted without encryption.
• Complexity in setting up and managing SNMP, requiring a good understanding of network management principles.

Applications: SNMP is widely used in network management systems for monitoring network-attached devices for conditions that warrant administrative attention. It is commonly used in data centers, large enterprise networks, and telecommunications networks.

Correct Option Analysis:

The correct option is:

Option 2: By responding to GET and SET requests from the SNMP Manager.

This option accurately describes the primary method of communication between the SNMP agent and the SNMP manager. The SNMP agent responds to GET requests from the SNMP manager to provide information about the managed device and to SET requests to configure or modify settings on the managed device.

Additional Information

To further understand the analysis, let’s evaluate the other options:

Option 1: By generating encrypted data streams.

This option is incorrect as SNMP itself does not inherently generate encrypted data streams. While SNMPv3 does support encryption to secure the data being transmitted, it is not the primary method of communication. The fundamental communication still revolves around GET and SET requests.

Option 3: By initiating a TCP connection.

SNMP primarily uses the User Datagram Protocol (UDP) for communication, not TCP. UDP is preferred for its lower overhead and faster transmission times, although it does not guarantee delivery like TCP. Therefore, this option is incorrect.

Option 4: By sending files via FTP.

This option is incorrect as it misrepresents the nature of SNMP communication. SNMP does not use the File Transfer Protocol (FTP) for communication between the agent and the manager. SNMP operates using its own set of protocols and messages, such as GET, SET, and TRAP.

Conclusion:

Understanding the correct method of communication between the SNMP agent and the SNMP manager is crucial for effective network management. The SNMP agent primarily communicates by responding to GET and SET requests from the SNMP manager, allowing for the collection and modification of data on managed devices. This communication method is fundamental to the operation of SNMP and enables centralized, automated, and proactive network management.

• TELNET is the terminal emulation protocol in a TCP/IP environment for the remote access of a terminal (client) to a server.
• TELNET uses the TCP as the transport protocol to establish a connection between server and client.

The correct answer is SMTP.

Key Points 

• SMTP:- The Simple Mail Transfer Protocol (SMTP) is used for the transfer of mail messages and attachments.
• IP:- The Internet Protocol (IP) is a routable protocol responsible for IP addressing and the fragmentation and reassembly of packets.
• UDP:- UDP provides a one-to-one or one-to-many, connectionless, unreliable communications service. UDP is used when the amount of data to be transferred is small.

File Transfer Protocol (FTP) is a standard communication protocol used for the transfer of computer files from a server to a client on a computer network.

FTP is built on a client-server model architecture using separate control and data connections between the client and the server.

Port numbers 21 and 20 are used for FTP. Port 21 is used to establish the connection between the 2 computers (or hosts) and port 20 to transfer data (via the Data channel).

Port 20- Data

Port 21- Host

File transfer is among the most frequently used TCP/IP applications and it accounts for a lot of the network traffic on the Internet.

Various standard file transfer protocols existed even before the Internet was available to everyone and it was these early versions of the file transfer software that helped create today's standard known as the File Transfer Protocol (FTP).

The correct answer is Protocol.

Key Points

• The set of rules that facilitate communication between nodes in a network is called Protocol. 
• A network protocol is an established set of rules that determine how data is transmitted between different devices in the same network.
  • It dictates how to format, transmit and receive data so that computer network devices -- from servers and routers to endpoints -- can communicate.
  • Network protocols break larger processes into discrete, narrowly defined functions and tasks across every level of the network.
  • In the standard model, known as the Open Systems Interconnection (OSI) model, one or more network protocols govern activities at each layer in the telecommunication exchange.
  • Lower layers deal with data transport, while the upper layers in the OSI model deal with software and applications.
• Classification of network protocols
  • DHCP: Dynamic Host Configuration Protocol
  • DNS: Domain Name System Protocol
  • FTP: File Transfer Protocol
  • HTTP: Hyper Text Transfer Protocol
  • IMAP and IMAP4: Internet Message Access Protocol (version 4)
  • POP and POP3: Post Office Protocol (version 3)
  • SMTP: Simple Mail Transfer Protocol
  • Telnet: Terminal emulation protocol
  • SNMP: Simple Network Management Protocol
  • LPP: Lightweight Presentation Protocol
  • RPC: Remote Procedure Call protocol
  • TCP: Transmission Control Protocol
  • UDP: User Datagram Protocol
  • IP: Internet Protocol (IPv4)
  • IPv6: Internet Protocol version 6
  • ICMP: Internet Control Message Protocol
  • ARP: Address Resolution Protocol
  • SLIP: Serial Line IP

SMTP stands for Simple Mail Transfer Protocol. SMTP is used when email is delivered from an email client, such as Outlook Express, to an email server or when email is delivered from one email server to another. SMTP uses port 25.

POP3 stands for Post Office Protocol. POP3 allows an email client to download an email from an email server. POP3 normally uses port 110.

IMAP stands for Internet Message Access Protocol. It is a protocol that an email client can use to download email from an email server. IMAP requires more disk space on the server and more CPU resources than POP3, as all emails are stored on the server. IMAP normally uses port 143.

The correct answer is option 3

SMTP:

• SMTP stands for Simple Mail Transfer Protocol and it is an application layer protocol.
• SMTP is used to send an email from a mail client to a mail server.
• SMTP uses port 25.

POP:

• POP stands for Post Office Protocol and it is also an application layer protocol.
• POP allows an email client to download an email from an email server.

HTTP:

The Hypertext Transfer Protocol (HTTP) is an Application Layer protocol and is used to check email in a web browser.

So, m1 : SMTP  m2 : POP m3 : HTTP

The correct answer is 1 - C, 2 - B, 3 - A.

Key Points 

• The Hypertext Transfer Protocol (HTTP) is an application layer protocol for distributed, collaborative, hypermedia information systems.
• The File Transfer Protocol (FTP) is a standard communication protocol used for the transfer of computer files from a server to a client on a computer network.
• Telnet is an application protocol used on the Internet or local area network to provide a bidirectional interactive text-oriented communication facility using a virtual terminal connection.

Additional Information

• INTERNET stands for Interconnected Network that is a network system that connects millions of web servers.
• GOOGLE stands for Global Organization of Oriented Group Language of Earth. 
• USB stands for Universal Serial Bus.
• CCTV stands for closed-circuit television.

• FTP is a client-server protocol for transmitting files between computers on the Internet over TCP/IP connections.
• FTP  stands for File Transfer Protocol
• Using FTP, a client can upload, download, delete, rename, move and copy files on a server.

HTTP: Multiple TCP connections can be used at client and server end.

FTP: For FTP also multiple connections can be used at the same time.

TELENT: Only one TCP connection is allowed at a time.

SMTP: SMTP also allows only one TCP connection at a time.

The correct answer is Option 2.

Concept:

The most commonly used Email protocols on the internet – POP3, IMAP, and SMTP. 

• Post Office Protocol 3 is the most commonly used protocol for receiving email over the internet. This standard protocol, which most email servers and their clients support, is used to receive emails from a remote server and send them to a local client.
• Internet Message Access Protocol is a protocol for accessing email or bulletin board messages from a mail server or service. IMAP allows a client e-mail program to access remote message stores as if they were local.
• The Simple Mail Transfer Protocol is the industry standard for sending emails over the Internet.

The correct answer is (ii), (iii), and (iv).