Chapter 1 — Computing and service architecture
Lesson map
Lesson 01 published. Map, example, EX001.
flowchart TD
N0["Learning outcomes"]
N1["1.1 The setting"]
N2["1.2 Clients, servers and services"]
N3["1.3 Mapping Castleford's services"]
N4["1.4 Where network security applies"]
N5["Synthesis"]
N0 --> N1 --> N2 --> N3 --> N4 --> N5
N5 --> EX["Worked example"]
EX --> Q["Exercise EX001"]
Logical drawing
flowchart LR
N0["Learning outcomes"]
N1["1.1 The setting"]
N2["1.2 Clients, servers and services"]
N3["1.3 Mapping Castleford's services"]
N4["1.4 Where network security applies"]
N5["Synthesis"]
N0 --> N1 --> N2 --> N3 --> N4 --> N5 --> Q["EX001"]
[Learning outcomes]
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v
[1.1 The setting]
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v
[1.2 Clients, servers and services]
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v
[1.3 Mapping Castleford's services]
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v
[1.4 Where network security applies]
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v
[Synthesis]
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v
[Worked example] --> [Exercise EX001]
Learning outcomes
You will (1) describe clients, servers and cloud services; (2) map an organisation's services; (3) identify where network security applies.
1.1 The setting
Amina Yusuf begins an eighteen-month technical programme at the fictional Harrowgate Technical Institute, taught by instructor Leon Fischer. Her practical work is linked to the fictional Castleford Housing Association, which manages affordable homes and has two offices, sixty staff and a team of field officers who visit tenants with laptops. A single IT officer, Rosa Delgado, runs everything with help from a support company. The course is practical: each chapter builds skills Amina will use on supervised tasks at Castleford, always with synthetic data in labs and Rosa's approval for anything touching real systems.
1.2 Clients, servers and services
Most work at Castleford follows a client-server pattern. Staff laptops are clients; they use services provided by servers, such as file shares, the housing management system and printing. Some services run on a small server room at the main office, and others are cloud services, such as email and the tenant portal. Each service listens for connections on particular ports. Amina learns to describe every service by who uses it, where it runs and how it is reached, because network rules, monitoring and troubleshooting are all written in exactly those terms.
1.3 Mapping Castleford's services
With Rosa, Amina draws a simple service map: two offices linked by a site-to-site VPN, a server room with the housing system and file server, cloud email and portal, remote access for field officers, a guest wireless network in each reception, and printers in both offices. The map shows which groups use which services. It also shows weak spots, such as the housing system being reachable from the guest wireless network because both share one subnet at the main office, which Rosa had not realised.
1.4 Where network security applies
Network security applies wherever data travels: between laptops and servers, between offices, between field officers and the office, and between Castleford and cloud services. Amina marks each path on the map with the controls that protect it today: the VPN between offices, a firewall at each internet connection and HTTPS to cloud services. Paths without controls, such as guest to housing system, become the first list of things to fix. This simple exercise turns a vague worry into a concrete, prioritised list.
Worked example
The service map shows nine services and one unprotected path from guest wireless to the housing system.
Synthetic case. Castleford and its systems are synthetic.
Errors and limits
Service maps drawn without checking real paths often miss shared subnets.
Exercises
- EX001 — Service description. Describe a service in the terms network rules need. Rubric: 3 = users, location, ports or access path;; 2 = some terms;; 1 = name only;; 0 = none.
- EX002 — Weak spot found. What weakness did the service map reveal? Rubric: 3 = guest wireless can reach housing system via shared subnet;; 2 = guest access;; 1 = vague;; 0 = none.
- EX003 — Path controls. Name two controls already protecting Castleford paths. Rubric: 3 = office VPN, firewall, HTTPS;; 2 = two;; 1 = one;; 0 = none.
- EX004 — Supervision rule. What must happen before Amina touches real Castleford systems? Rubric: 3 = Rosa's approval;; 2 = approval;; 1 = vague;; 0 = none.
Synthesis
Mapping services and paths shows where network security controls are needed.