Network Protocols : MCQs & PYQs with Explanation

Option B

Emails were originally designed to send only ASCII (American Standard Code for Information Interchange) text, meaning simple English letters, digits, and symbols. But over time, people needed to send images, audio, video, documents, and text in other languages (Non-ASCII).

To solve this, an additional standard was developed called MIME (Multipurpose Internet Mail Extensions). It works with existing email protocols like SMTP, POP, or IMAP and allows emails to carry different types of content.
Besides supporting non-ASCII text, MIME also allows multiple parts in a single email, enabling attachments and formatted text. When we attach a photo or a PDF in an email, MIME encodes that file into a format (like Base64) that can be sent as plain text through SMTP. The receiver’s email client then decodes it back to the original file.

Option D

When we use email, different protocols handle the sending and receiving of messages. SMTP (Simple Mail Transfer Protocol) is used for sending emails from one server to another, while POP (Post Office Protocol) is designed to download emails from the server to a single device, usually removing them from the server afterward. 

In contrast, IMAP (Internet Message Access Protocol) allows users to access, manage, and organize their emails directly on the mail server, keeping messages synchronized across multiple devices such as phones, laptops, and tablets.

Option B

In networking, different protocols are used for communication and service management.
When a network service starts, it must inform other devices about its availability. This is done using a protocol that allows dynamic registration of services in a table.
Service Advertising Protocol (SAP) is a protocol used in the IPX (Internetwork Packet Exchange) suite that enables network services to dynamically advertise their availability to other devices on the network. It maintains a Server Information Table (SAP Table), where details of available services are stored.
For example, when a file server starts, it broadcasts its presence using SAP so that clients on the network can easily discover and access its services.

Option B

The Domain Name System (DNS) is like the phonebook of the internet. It helps us convert easy-to-remember domain names into numerical IP addresses that computers use to communicate. DNS makes browsing the internet simple and user-friendly.
There are two types of DNS lookups:
Forward Lookup: This converts a domain name to an IP address using A or AAAA records.
Reverse Lookup: This converts an IP address back to a domain name using a PTR (Pointer) record. It helps in verification, logging, and network troubleshooting.

Option C

When a client (web browser) sends a request to a web server using the HTTP (Hypertext Transfer Protocol), the server responds with a status code. HTTP status codes are three-digit numbers returned by a web server to indicate the result of a client’s request.

The status code 404 means, “Not Found”, the requested resource such as a webpage or file does not exist on the server.

Option D

The Address Resolution Protocol (ARP) is used for finding the MAC address that corresponds to a given IP address within a Local Network.
When a device wants to communicate with another device on the same network, it needs the MAC address (Physical Address) of the destination device to actually send the data.
ARP helps in this process by broadcasting a request with the target IP address to all devices on the network. Only the device with the matching IP responds with its MAC address, enabling the sender to Map the IP Address to the correct MAC Address.

Option D

To identify the physical address (MAC address) of a device from its IP address, the Address Resolution Protocol (ARP) is used. ARP maps a logical IP address to its corresponding physical MAC address within a local network.

Option A

A Protocol is a set of rules that allows computers to communicate with each other over a network. For accessing the Internet, computers must use a common protocol that is accepted worldwide.
The Internet is based on the TCP/IP protocol suite. TCP (Transmission Control Protocol) is responsible for reliable data transmission, while IP (Internet Protocol) handles addressing and routing of data packets from the source to the destination.

Option B

In computer networks, different layers of the OSI/TCP-IP model use specific protocols for communication:

• Transport Layer is responsible for end-to-end communication and uses protocol like TCP or UDP.
• Network Layer handles logical addressing and routing and uses protocols like IP, ARP.
• Data Link Layer is responsible for node-to-node communication and uses protocols like PPP, Frame Relay.

Option B

ARP (Address Resolution Protocol) is used in computer networks to map a known IP address to its corresponding MAC (Media Access Control) address within a local network.

Option A

An FTP (File Transfer Protocol) session is established between a client and a server for file transfer over a network. The question specifically asks which criteria must be met, meaning only those conditions that are compulsory in every case should be selected.
For an FTP session, the FTP server must be active and running, otherwise no connection can be established. 
The client system must have FTP client software to initiate and manage the communication. 
Also, FTP operates on the TCP/IP protocol suite, so both client and server must support TCP/IP for data transfer.
Although user authentication (username and password) is commonly used, it is not mandatory in all cases, because FTP also supports anonymous login, where users can access the server without credentials.

Option C

In computer networks, Electronic Mail (Email) requires reliable data transmission so that messages are delivered correctly without loss. The Transport Layer provides this reliability using protocols like TCP and UDP.
TCP (Transmission Control Protocol) is a connection-oriented and reliable protocol that ensures data is delivered in order and without errors. Email protocols such as SMTP, POP3, and IMAP use TCP to guarantee proper delivery.

Option C

HDLC (High-Level Data Link Control) is a Layer-2 (Data Link Layer), bit-oriented (it treats the transmitted data as a stream of bits) protocol formalized by ISO. It supports reliable framing, Error Detection (CRC) for reliable communication and operates commonly in point-to-point links (Router-to-Router).

Option C

DNSSEC (Domain Name System Security Extensions) is designed to provide authentication and integrity of DNS data, ensuring that the DNS response comes from the correct source and has not been altered during transmission. 
However, DNSSEC does not encrypt the data, it only uses Digital Signatures to verify authenticity. Therefore, the DNS queries and responses remain visible in plain text, even though their integrity can be verified.

Option D

SSL (Secure Sockets Layer) handshake is the process used to establish a secure connection between client and server. It follows a defined sequence of message exchanges.
Basic Flow of SSL Handshake:

• Client Hello : Client initiates communication and sends supported parameters.
• Server Hello : Server responds with chosen parameters.
• Server Key Exchange : Server sends key-related information if required.
• Client Key Exchange : Client sends key information to establish session key.