Computer Networks
OSI Model, TCP/IP, Protocols & Network Security
CS303 – Computer Networks
Undergraduate Computer Science
Comprehensive Study Guide | Exam Ready
, 1. Introduction to Computer Networks
A computer network is a group of interconnected devices that share resources and
communicate using agreed-upon protocols. Networks enable resource sharing, communication,
and distributed computing.
1.1 Network Classification by Scale
Network Full Name Coverage Example
Type
PAN Personal Area Network ~10 meters Bluetooth devices, USB peripherals
LAN Local Area Network Building/campus Office network, university Wi-Fi
MAN Metropolitan Area City-wide Cable TV, city-wide Wi-Fi
Network
WAN Wide Area Network Country/global The Internet, bank networks
2. OSI Model (7 Layers)
The OSI (Open Systems Interconnection) model is a conceptual framework that standardizes
how different network systems communicate in seven distinct layers.
Layer Name Function Protocols/Examples
7 Application User interface, application HTTP, HTTPS, FTP, SMTP, DNS
services
6 Presentation Data formatting, encryption, SSL/TLS, JPEG, MPEG, ASCII
compression
5 Session Manages NetBIOS, RPC, PPTP
sessions/connections
between apps
4 Transport End-to-end communication, TCP, UDP, port numbers
error control
3 Network Logical addressing, routing IP, ICMP, OSPF, BGP, routers
2 Data Link Physical addressing, error Ethernet, MAC addresses, switches
detection
1 Physical Transmission of raw bits Cables, hubs, fiber, Wi-Fi signals
over media
Mnemonic to remember layers (top to bottom): All People Seem To Need Data Processing
3. TCP/IP Model
OSI Model, TCP/IP, Protocols & Network Security
CS303 – Computer Networks
Undergraduate Computer Science
Comprehensive Study Guide | Exam Ready
, 1. Introduction to Computer Networks
A computer network is a group of interconnected devices that share resources and
communicate using agreed-upon protocols. Networks enable resource sharing, communication,
and distributed computing.
1.1 Network Classification by Scale
Network Full Name Coverage Example
Type
PAN Personal Area Network ~10 meters Bluetooth devices, USB peripherals
LAN Local Area Network Building/campus Office network, university Wi-Fi
MAN Metropolitan Area City-wide Cable TV, city-wide Wi-Fi
Network
WAN Wide Area Network Country/global The Internet, bank networks
2. OSI Model (7 Layers)
The OSI (Open Systems Interconnection) model is a conceptual framework that standardizes
how different network systems communicate in seven distinct layers.
Layer Name Function Protocols/Examples
7 Application User interface, application HTTP, HTTPS, FTP, SMTP, DNS
services
6 Presentation Data formatting, encryption, SSL/TLS, JPEG, MPEG, ASCII
compression
5 Session Manages NetBIOS, RPC, PPTP
sessions/connections
between apps
4 Transport End-to-end communication, TCP, UDP, port numbers
error control
3 Network Logical addressing, routing IP, ICMP, OSPF, BGP, routers
2 Data Link Physical addressing, error Ethernet, MAC addresses, switches
detection
1 Physical Transmission of raw bits Cables, hubs, fiber, Wi-Fi signals
over media
Mnemonic to remember layers (top to bottom): All People Seem To Need Data Processing
3. TCP/IP Model
