Question 1

What is the key difference between TCP and UDP?

Accepted Answer

TCP is connection-oriented and reliable (guaranteed delivery, ordering); UDP is connectionless and faster but unreliable. TCP (Transmission Control Protocol) has handshaking, acknowledgements, and retransmission. UDP (User Datagram Protocol) has none — it just sends. Use TCP for accuracy (HTTP), UDP for speed (video, DNS).

Question 2

How many layers does the OSI model have, and what is the top layer?

Accepted Answer

7 layers; top is Application. OSI has 7 layers (bottom to top): Physical, Data Link, Network, Transport, Session, Presentation, Application. The Application layer (Layer 7) is where HTTP, FTP, DNS, and SMTP operate.

Question 3

What is the difference between HTTP and HTTPS?

Accepted Answer

HTTPS encrypts communication using TLS/SSL; HTTP sends data as plain text. HTTPS = HTTP + TLS encryption. Data between browser and server is encrypted, preventing eavesdropping and tampering. HTTPS uses port 443; HTTP uses port 80.

Question 4

What is ARP (Address Resolution Protocol) used for?

Accepted Answer

Mapping an IP address to a MAC (physical) address on a local network. When a device wants to communicate on a LAN, it broadcasts an ARP request: 'Who has IP x.x.x.x? Tell me your MAC address.' The device with that IP replies with its MAC.

Question 5

What is the difference between a hub, switch, and router?

Accepted Answer

Hub broadcasts to all devices; switch sends to a specific device; router connects different networks. Hub (Layer 1): broadcasts to all. Switch (Layer 2): forwards to specific MAC address. Router (Layer 3): routes between different networks using IP addresses. Hubs are obsolete; switches and routers are standard.

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