Networks and Data Communication
Infrastructure
Networks and Data Communication
Syllabus tag: KASNEB CPA | Foundation Level | CA16 Information Communication Technology | Topic 5 Networks and Data Communication
Lesson objectives
By the end of this topic, you will be able to:
- Classify networks by geographical scope
- Describe the common network topologies
- Identify the main networking devices
- Explain the client-server and peer-to-peer models
- Describe transmission media and the factors affecting speed
Why this matters
Nothing in a modern accounting system is standalone. Understanding how the parts connect explains where data can be intercepted, why a branch office is slow, and what a company is buying when it pays for bandwidth.
Classification by scope
| Network | Scope |
|---|---|
| PAN | Personal — devices around one person, typically Bluetooth |
| LAN | Local — one building or site |
| MAN | Metropolitan — a city or campus |
| WAN | Wide — countries or continents; the internet is the largest |
LAN and WAN differ in more than distance. A LAN is usually owned by the organisation and is fast and cheap to run. A WAN uses third-party infrastructure, is slower, costs money continuously, and is where security exposure begins — the data leaves premises the company controls.
Topologies
| Topology | Structure | Weakness |
|---|---|---|
| Bus | All devices on one backbone cable | The backbone fails and the whole network stops |
| Star | All devices connect to a central hub or switch | The hub fails and the whole network stops |
| Ring | Each device connects to two others in a loop | A single break can halt the ring |
| Mesh | Devices interconnect on multiple paths | Expensive in cabling |
| Tree / hierarchical | Stars connected to a backbone | Backbone dependence |
Star is the usual choice for an office. It costs more in cable than a bus and is far easier to diagnose: one workstation failing affects only itself, and faults can be traced to a single connection.
Mesh is expensive because it is resilient. Multiple paths mean no single break isolates anything, which is why the backbone of the internet is meshed and an office is not.
Network devices
- Network interface card (NIC) — connects a device to the network
- Switch — directs traffic only to the intended recipient
- Router — connects different networks and chooses the path between them
- Modem — converts between digital and analogue signals
- Firewall — filters traffic according to rules
- Access point — provides wireless connection to a wired network
A switch and a hub differ in an important way. A hub sends every message to every device; a switch sends it only where it is addressed. The switch is faster and more secure, because traffic is not broadcast to machines that have no business seeing it.
Client-server and peer-to-peer
| Client-server | Peer-to-peer | |
|---|---|---|
| Structure | Central server provides services | Each machine both requests and provides |
| Security | Centrally administered | Managed on each machine |
| Backup | Centralised and reliable | Each user is responsible |
| Cost | Higher — server and administration | Lower |
| Suits | Any organisation keeping accounting records | Very small offices |
Any business keeping accounting records should use client-server. Not for speed, but because backup and access control can be enforced centrally. In a peer-to-peer network, the security of the whole is the security of the least careful user.
Transmission media
| Medium | Characteristics |
|---|---|
| Twisted pair | Cheap, common in offices, limited distance |
| Coaxial | Better shielding, higher capacity |
| Fibre optic | Very high capacity, immune to electrical interference, hard to tap |
| Wireless / radio | Convenient, no cabling, easier to intercept |
| Satellite | Reaches remote areas, noticeable delay |
| Microwave | Line of sight, high capacity |
Fibre is hard to tap, which is a security property as well as a performance one. Wireless is the reverse: convenience is bought with an exposure that requires encryption to manage, since the signal does not stop at the wall.
Speed and its limits
Bandwidth is the capacity of the link. Latency is the delay before data starts arriving. They are different, and confusing them is a common error.
A satellite link may have high bandwidth and poor latency — plenty of capacity, but a noticeable pause on every exchange. A file transfer barely notices; an interactive system feels unusable.
Other factors: the number of simultaneous users, the protocol overhead, and the slowest link in the path. A network is only as fast as its narrowest point, which is why upgrading a head office connection does nothing for a branch on a poor line.
:::checkpoint A branch office reports that the accounting system is slow, though head office finds it fast. Identify three possible explanations from this topic and say which you would test first. :::
Protocols
A protocol is an agreed set of rules for communication.
- TCP/IP — the foundation of the internet
- HTTP and HTTPS — web pages; HTTPS adds encryption
- FTP — file transfer
- SMTP, POP3, IMAP — email sending and retrieval
The S in HTTPS matters to an accountant. Data submitted over plain HTTP travels readable by anyone in the path. Any page collecting a password, a payment or client data should be HTTPS, and a browser warning to that effect should never be dismissed.
:::checkpoint A company allows staff to access the accounting system over public wireless networks. Identify the risk and state two controls that would reduce it. :::