A computer network is a group of interconnected devices that exchange data using defined communication protocols, forming the backbone of digital transformation.
Topology Options
| Topology | Description |
|---|---|
| Bus | Single shared cable — simple but collision-prone |
| Ring | Each node in a loop — orderly but breaks on one failure |
| Star | All nodes link to a central hub — robust but hub-dependent |
| Mesh | Every node connects to multiple peers — fault-tolerant but complex |
| Tree/Hybrid | Combinations of star, bus, ring, and mesh for scalability |
Network Scopes
| Scope | Coverage |
|---|---|
| PAN | Personal Area Network (a few devices) |
| LAN | Local Area Network (single site) |
| MAN | Metropolitan Area Network (city-wide) |
| WAN | Wide Area Network (regional/global) |
TCP/IP Model ↔ OSI Layers
| TCP/IP Layer | OSI Layer | Examples |
|---|---|---|
| Link | Data Link / Physical | Ethernet, ARP, Wi-Fi, Bluetooth |
| Internet | Network | IP, ICMP, IPsec |
| Transport | Transport | TCP, UDP |
| Application | Session / Presentation / Application | HTTP, HTTPS, DNS, FTP, SSH |
Key Protocols
| Protocol | Purpose | Default Port(s) |
|---|---|---|
| TCP | Reliable, ordered delivery | — |
| UDP | Low-overhead, best-effort | — |
| IP | Addressing & routing | — |
| HTTP | Web traffic | 80 |
| HTTPS | Encrypted web traffic | 443 |
| DNS | Domain name resolution | 53 |
Core Networking Devices
| Device | Function |
|---|---|
| Switch | Forwards frames based on MAC addresses |
| Router | Directs packets using IP routing tables |
| Firewall | Enforces security policies at network boundaries |
| Access Point | Bridges wired and wireless segments |
Media Choices
| Media Type | Pros | Cons |
|---|---|---|
| Copper Cable | Cost-effective, easy to install | Limited distance & bandwidth |
| Fiber Optic | Very high bandwidth, long distance | Higher cost, delicate installation |
| Wireless | Flexible coverage, no cabling | Subject to interference, security |
Security Essentials
| Feature | Role |
|---|---|
| Authentication | Verifies user/device identity |
| Encryption (TLS) | Protects data in transit |
| Network Address Translation (NAT) | Translates private ↔ public IPs |
> Keep these high-level points in mind when designing, troubleshooting, or scaling any network.