Networking Questions for SBI PO

Types of Networks

Networks are classified by their geographic coverage. Knowing the scope of each type is the most tested concept. PAN covers personal devices like Bluetooth earphones. LAN covers a building or campus. MAN covers a city. WAN covers countries or the globe. The internet is the largest WAN.

• PAN: Personal Area Network — Bluetooth, up to 10 metres
• LAN: Local Area Network — office, school, up to few km
• MAN: Metropolitan Area Network — city-wide, eg. cable TV networks
• WAN: Wide Area Network — country or global scale, uses leased lines
• Internet is a network of networks — the biggest WAN
• WLAN: Wireless LAN — uses Wi-Fi, no physical cables

Network Topologies

Topology means the physical or logical arrangement of devices in a network. SBI PO tests which topology has a single point of failure, which is most fault-tolerant, and which uses the least cable. Bus uses one common cable; Star connects all to a central hub; Ring connects in a loop; Mesh connects every device to every other device.

• Bus: one backbone cable, easy to set up, single break disrupts all
• Star: all connect to central hub/switch — most common in offices
• Ring: data travels in one direction around a loop — single break = failure
• Mesh: every device connected to every other — most fault-tolerant, most expensive
• Tree: hybrid of Bus and Star — used in large networks
• Star topology failure: only affected node goes down, rest keep working

Network Devices

Each hardware device in a network has a specific job. SBI PO frequently asks which device does what — especially confusing pairs like Hub vs Switch, Router vs Gateway, and Modem vs Router. Remember: Hub is dumb (broadcasts to all), Switch is smart (sends to specific device), Router connects different networks.

• Hub: Layer 1 device, broadcasts data to all ports — no filtering
• Switch: Layer 2 device, sends data to specific MAC address — smarter than hub
• Router: Layer 3 device, connects different networks, uses IP addresses
• Modem: converts digital to analog and back — needed for internet via telephone line
• Gateway: connects networks with different protocols — acts as a translator
• Repeater: boosts weak signals over long distances — Layer 1 device
• Bridge: connects two LAN segments — Layer 2 device

Protocols and Standards

Protocols are rules for data communication. SBI PO asks full forms, port numbers, and what each protocol does. The most tested ones are TCP/IP, HTTP, FTP, SMTP, DNS, DHCP, and HTTPS. Remember that HTTP uses port 80 and HTTPS uses port 443.

• TCP/IP: Transmission Control Protocol / Internet Protocol — backbone of internet
• HTTP: HyperText Transfer Protocol — web browsing, port 80
• HTTPS: HTTP Secure — encrypted web browsing, port 443
• FTP: File Transfer Protocol — transferring files, port 21
• SMTP: Simple Mail Transfer Protocol — sending emails, port 25
• DNS: Domain Name System — converts domain names to IP addresses
• DHCP: Dynamic Host Configuration Protocol — assigns IP addresses automatically
• POP3: Post Office Protocol v3 — receiving emails, port 110

OSI Model and TCP/IP Model

The OSI model has 7 layers. SBI PO asks layer names, their order, and which device or protocol works at which layer. The TCP/IP model has 4 layers and is the practical model used on the internet. Think of OSI as the theory model and TCP/IP as the real-world model.

• OSI layers (top to bottom): Application, Presentation, Session, Transport, Network, Data Link, Physical
• Mnemonic for OSI top to bottom: All People Seem To Need Data Processing
• Physical layer: cables, hubs, repeaters
• Data Link layer: switches, bridges — uses MAC address
• Network layer: routers — uses IP address
• Transport layer: TCP and UDP — end-to-end communication
• TCP/IP layers: Application, Transport, Internet, Network Access (4 layers only)

IP Addressing and Related Terms

An IP address uniquely identifies a device on a network. IPv4 uses 32 bits (eg. 192.168.1.1) and IPv6 uses 128 bits. MAC address is the hardware address burned into a network card. SBI PO tests the difference between public and private IP, IPv4 vs IPv6, and what DNS does.

• IPv4: 32-bit address, written as 4 octets — about 4.3 billion addresses
• IPv6: 128-bit address, written in hexadecimal — solves address exhaustion
• MAC address: 48-bit physical address, unique to every network card
• Private IP: used inside a LAN (eg. 192.168.x.x) — not routable on internet
• Public IP: assigned by ISP, visible on the internet
• DNS converts human-readable names (google.com) to IP addresses

Internet Terms and Transmission Media

SBI PO occasionally asks about ISP, bandwidth, broadband, Wi-Fi standards, and cable types. Bandwidth is the amount of data transmitted per second. Broadband means high-speed internet. Optical fibre is the fastest physical medium. Wi-Fi uses IEEE 802.11 standards.

• ISP: Internet Service Provider — connects users to the internet
• Bandwidth: data transfer capacity, measured in bps, Kbps, Mbps, Gbps
• Twisted pair cable: most common LAN cable — cheap, limited range
• Coaxial cable: used in cable TV networks — better shielding
• Optical fibre: fastest, uses light signals, immune to electromagnetic interference
• Wi-Fi standard: IEEE 802.11 — 802.11ac and 802.11ax (Wi-Fi 6) are latest

• Confusing Hub and Switch — Hub sends data to ALL ports; Switch sends to the specific destination MAC address only.
• Mixing up SMTP and POP3 — SMTP is for SENDING emails, POP3 and IMAP are for RECEIVING emails.
• Getting OSI layer order wrong — remember the mnemonic both top-down and bottom-up since questions ask both ways.
• Thinking Router and Gateway are the same — Router connects similar networks using IP; Gateway connects networks with different protocols and acts as a full translator.
• Confusing Modem with Router — Modem connects you to the ISP line; Router distributes that connection inside your home or office.

• OSI layers top to bottom: All People Seem To Need Data Processing (Application, Presentation, Session, Transport, Network, Data Link, Physical)
• Hub Switch Router Gateway — order of intelligence: Hub is dumbest, Gateway is smartest. Think HSRG = Humans Slowly Reach Greatness.
• Port numbers trick: HTTP 80 = H is the 8th letter; HTTPS 443 = 4+4+3 = 11 = HTTPS has 5 letters... just memorise 80 and 443 as a pair.
• Network size order: PAN less than LAN less than MAN less than WAN — think Personal, Local, Metro, Wide = People Love Metro Walks.

• SBI PO typically asks 3-4 networking questions — expect at least one on protocols (full form or port number), one on devices (Hub vs Switch vs Router), and one on OSI layers.
• Full forms are heavily tested — know FTP, SMTP, DNS, DHCP, HTTP, ISP, LAN, WAN, MAN, PAN cold. A wrong full form is a common trap option.
• Topology questions usually ask about fault tolerance (answer: Mesh) or single point of failure (answer: Star hub failure or Bus backbone break).
• OSI model questions often give a device and ask which layer it operates at — remember: Physical=Hub/Repeater, Data Link=Switch/Bridge, Network=Router.
• In SBI PO descriptive or passage-based computer questions, networking terms may appear in context — do not skip TCP/IP model as it is increasingly tested in newer papers.