Networking Fundamentals (TCP/IP, DNS, HTTP) Interview Questions & Answers (2025) | JaganInfo

A computer network is a collection of interconnected devices that can communicate and share resources.

The Internet is a global network of networks that connects millions of private, public, academic, business, and government networks.

The OSI model is a conceptual framework dividing network communication into seven layers from physical transmission to application-level interactions.

TCP/IP is a suite of communication protocols used to interconnect network devices on the Internet, comprising the Transmission Control Protocol and Internet Protocol.

An IP address is a numerical label assigned to each device connected to a computer network that uses the IP for communication.

IPv4 uses 32-bit addresses and supports about 4.3 billion addresses, IPv6 uses 128-bit addresses supporting a vastly larger number and improved routing.

The Domain Name System translates domain names like example.com into IP addresses machines can understand.

HTTP (HyperText Transfer Protocol) is the protocol used for transferring hypermedia documents, such as HTML, over the web.

HTTPS is the secure version of HTTP, using SSL/TLS to encrypt communication between browser and server.

A port number identifies specific processes or network services on a device to direct traffic correctly.

TCP uses a three-step process (SYN, SYN-ACK, ACK) to establish a reliable connection between client and server before data transmission.

TCP is connection-oriented, reliable, and ensures data is received in order; UDP is connectionless, faster, but offers no reliability.

A subnet divides a network into smaller logical segments to improve routing efficiency and enhance security.

Network Address Translation maps multiple private IP addresses to a single public IP address to conserve IP space and enhance security.

A firewall filters incoming and outgoing network traffic based on security rules to protect networks from unauthorized access.

DNS resolution queries root servers, TLD servers, and authoritative servers sequentially to resolve a domain name to an IP.

Address Resolution Protocol maps IP addresses to MAC addresses in a local network enabling device communication.

A proxy server acts as an intermediary between clients and servers, providing anonymity, caching, and filtering services.

Persistent connections reuse the same TCP connection for multiple requests, reducing latency; non-persistent connections open and close TCP connections per request.

Codes sent by a server to indicate the result of a client’s request, e.g., 200 OK, 404 Not Found, 500 Internal Server Error.

A process to establish secure encrypted communication by exchanging certificates and agreeing on encryption keys.

Distributing incoming network traffic across multiple servers to increase availability and reliability.

QoS prioritizes network traffic to ensure performance for critical applications, managing bandwidth and latency.

Internet Control Message Protocol is used for network diagnostics and error messages, such as ping and traceroute utilities.

Protocols like OSPF, BGP help routers dynamically select the best path to forward packets across networks.

Dynamic Host Configuration Protocol automatically assigns IP addresses and network configurations to devices.

Static NAT maps one private IP to a public IP; dynamic NAT assigns from a pool; PAT (Port Address Translation) allows multiple private IPs to share one public IP using ports.

Unicast sends data to a single receiver; multicast to a specified group; broadcast to all devices on a network segment.

Sockets are endpoints for sending or receiving data across a network connection, identified by IP address and port number.

Content Delivery Network caches static content at edge servers closer to users to improve access speed and reduce server load.

TCP uses algorithms like Slow Start, Congestion Avoidance, Fast Retransmit and Fast Recovery to detect congestion and adjust transmission rate.

Border Gateway Protocol is the main inter-domain routing protocol of the Internet, managing how packets are routed between autonomous systems.

DNS responses are cached locally and in intermediate servers to reduce lookup times and decrease network traffic.

HTTPS uses SSL/TLS to encrypt data in transit, verify server identity using certificates, and ensure data integrity and confidentiality.

HTTP/2 allows multiple requests and responses to be sent concurrently over a single TCP connection, improving load times and reducing latency.

A Virtual Private Network creates a secure encrypted tunnel over the internet to protect online privacy and data.

Common attacks include DDoS, Man-in-the-Middle, spoofing, phishing, brute-force, and injection attacks.

A TCP segment contains TCP header and data for reliable transport; an IP packet includes IP header and encapsulates TCP or UDP segments for routing.

Stateless protocols (HTTP) treat each request independently; stateful protocols (TCP) maintain session state across multiple requests.

WebSockets enable full-duplex communication channels over a single TCP connection, making real-time web applications possible.

Sticky sessions route requests from the same client to the same backend server to maintain session state.

3xx codes indicate redirection, instructing the client to perform further actions to complete the request, e.g., 301 Moved Permanently.

SDN separates the control plane from the data plane, allowing centralized network management and programmability.

Multiprotocol Label Switching directs data from one node to the next based on short path labels instead of long network addresses, speeding routing.

Purging removes cached content from CDN edge servers to ensure updated content is served.

Static NAT, dynamic NAT, and PAT (Port Address Translation) differ in how they map private to public IPs and ports.

ARP cache stores recently resolved IP-to-MAC address mappings to speed up address resolution and reduce network traffic.

TLS establishes security via negotiation, key exchange, certificate validation, symmetric encryption, and message authentication.

A denial-of-service attack exploiting the TCP three-way handshake by sending incomplete connection requests to exhaust server resources.

Use firewalls, encryption, strong authentication, regular patching, intrusion detection systems, and network segmentation.