Protocols — Set 6

Correct Answer: B. Protocol

• **Protocol** — the 'P' in IP stands for Protocol, giving the full name Internet Protocol, which is the fundamental communication standard that defines how data packets are addressed, formatted, and routed across interconnected networks worldwide. • **Key fact** — IP comes in two versions: IPv4 (using 32-bit addresses like 192.168.1.1) and IPv6 (using 128-bit addresses like 2001:db8::1); IPv6 was created because the world ran out of available IPv4 addresses in 2011. • IP is a connectionless, best-effort protocol — it does not guarantee delivery, ordering, or error correction; those functions are delegated to TCP at the layer above. • 💡 Option A (Program) is wrong because Program has no standard networking meaning in the context of the IP abbreviation; Option C (Package) is wrong because data units in IP networking are called packets or datagrams, not packages, and Package does not expand any recognized networking acronym; Option D (Path) is wrong because path describes a concept in routing but is not part of the IP abbreviation.

Correct Answer: C. SMTP

• **SMTP (Simple Mail Transfer Protocol)** = the internet standard for sending email — when you hit Send, your email client connects to your provider's SMTP server (port 25 or 587), which then relays the message hop-by-hop to the recipient's mail server. • **Key fact** — SMTP is a push protocol: it actively pushes mail from one server to the next until it reaches the destination; it does not handle reading or retrieving email, which is why separate protocols (POP3 or IMAP) exist for that purpose. • SMTP authentication (SMTP AUTH) requires senders to prove their identity with a username and password before the server will relay outbound mail, preventing spam abuse. • 💡 Option A (POP3) is wrong because POP3 is used by clients to download email from the inbox on their server — it is a retrieval protocol, not a sending protocol; Option B (IMAP) is wrong because IMAP lets users read and manage email stored on the server across multiple devices, not send email to other servers; Option D (HTTP) is wrong because HTTP is used to serve web pages and has no role in inter-server mail routing.

Correct Answer: C. 80

• **Port 80** = the well-known default TCP port assigned to HTTP by IANA — when a browser connects to http://example.com without specifying a port, it automatically contacts port 80 on the server, which is where the web server listens for incoming page requests. • **Key fact** — port numbers below 1024 are called "well-known ports" and are reserved for standard services: port 80 for HTTP, port 443 for HTTPS, port 25 for SMTP, port 21 for FTP control, port 22 for SSH, and port 53 for DNS. • When a firewall blocks port 80, all plain HTTP traffic to that server is cut off, which is why firewall rules are written port-by-port for each service. • 💡 Option A (21) is wrong because port 21 is the control channel for FTP — used for login and commands, not for web traffic; Option B (25) is wrong because port 25 is used by SMTP for server-to-server email transfer; Option D (443) is wrong because port 443 is the default for HTTPS (encrypted web traffic), not for plain unencrypted HTTP.

Correct Answer: B. UDP

UDP or User Datagram Protocol just 'fires and forgets' packets toward a destination. This lack of overhead makes it very fast and efficient for streaming. If a packet is lost, UDP does not try to send it again.

Correct Answer: B. Transferring files

FTP or File Transfer Protocol is used to upload and download files to a server. It was one of the earliest protocols developed for the internet. It remains popular for large bulk data transfers between businesses.

Correct Answer: C. DNS

DNS or Domain Name System acts as the internet's translator. It allows humans to use easy-to-remember names while computers use numbers. This system is essential for the usability of the World Wide Web.

Correct Answer: B. SSH

SSH or Secure Shell is the industry standard for logging into remote servers. It encrypts the entire session, protecting the password from being stolen. It is the secure replacement for the older Telnet protocol.

Correct Answer: B. IMAP

IMAP keeps all emails on the server, which allows for perfect synchronization between devices. If you delete an email on your phone, it is also deleted on your laptop. This is the most popular way to read email today.

Correct Answer: A. HyperText Transfer Protocol Secure

HTTPS is the encrypted version of the basic HTTP protocol. It ensures that data sent between your browser and the website is private. Almost all modern websites use HTTPS to protect user data.

Correct Answer: C. ARP

ARP or Address Resolution Protocol is used by computers on a local network to talk to each other. Every device maintains an ARP table to remember which hardware belongs to which IP. It is a critical part of how local networks function.