SPARRSO — Assistant Engineer (CSE) — Written Exam: 2020প্রশ্ন ও সমাধান

Network protocol is a formal set of rules and conventions that governs how data is formatted, transmitted, and received between devices on a network, so that hardware and software from different vendors can communicate reliably despite differences in design.

TCP/IP (Transmission Control Protocol/Internet Protocol) is the foundational protocol suite of the Internet, originally developed by the U.S. Department of Defense, that specifies how data is broken into packets, addressed, routed, transmitted, and reassembled at the destination.

TCP/IP's 4-layer model:

Layer	Function	Example Protocols
Application	User-facing services; formats data for the application	HTTP, FTP, DNS, SMTP
Transport	End-to-end delivery, reliability (TCP) or speed (UDP)	TCP, UDP
Internet	Logical addressing and routing between networks	IP, ICMP, ARP
Network Access	Physical transmission over the actual medium	Ethernet, Wi-Fi (802.11)

graph TD
    App["Application Layer (HTTP, FTP, DNS)"] --> Trans["Transport Layer (TCP, UDP)"]
    Trans --> Int["Internet Layer (IP, ICMP)"]
    Int --> NA["Network Access Layer (Ethernet, Wi-Fi)"]

Key characteristics:

• TCP provides connection-oriented, reliable delivery (acknowledgements, retransmission, ordered packets) — used for web pages, email, file transfer.
• IP provides connectionless, best-effort addressing and routing using IP addresses.
• TCP/IP requires little central management and is designed to recover automatically from failure of any single device or link on the network, thanks to its packet-based, decentralized routing.

Exam takeaway: a protocol is the "rulebook" for communication; TCP/IP is the internet's 4-layer rulebook (Application to Transport to Internet to Network Access) where TCP guarantees reliable delivery and IP handles addressing/routing.

A computer network is a collection of interconnected computing devices that can exchange data and share resources (files, printers, internet access) with one another.

Types of computer network, classified by geographical scope:

Type	Full Form	Typical Range	Example
PAN	Personal Area Network	A few meters	Bluetooth headset connected to a phone
LAN	Local Area Network	A single building/campus	Office computers linked via a switch
CAN	Campus Area Network	Multiple buildings, one campus	A university connecting several departments
MAN	Metropolitan Area Network	An entire city	Cable TV network or city-wide Wi-Fi
WAN	Wide Area Network	Country/global	The Internet itself

flowchart LR
    PAN["PAN - a few meters (Bluetooth)"] --> LAN["LAN - one building/campus"]
    LAN --> CAN["CAN - multiple buildings"]
    CAN --> MAN["MAN - a city"]
    MAN --> WAN["WAN - country/global (Internet)"]

Additional classification by architecture:

• Client-Server network: dedicated servers provide services (files, email, web pages) to client machines.
• Peer-to-Peer (P2P) network: every node can act as both client and server, sharing resources directly without a central server.
• Wireless networks (WLAN/WWAN): any of the above types implemented over radio/Wi-Fi/cellular instead of physical cabling.

Example: a bank's ATM network spans the country (WAN), its head-office building uses a LAN, and its regional data centers might be linked via a MAN - showing how these types nest and combine in practice.

Exam takeaway: network types scale by geographical range - PAN < LAN < CAN < MAN < WAN - and can additionally be classified by architecture (client-server vs peer-to-peer) or medium (wired vs wireless).