Chapter 1 — Computing and service architecture

Open, free learning for anyone who wants to protect people and technology. No account is required to read this text or its worked answers.

Public activity · 30d

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Learning outcomes

You will (1) describe how a small organisation's services fit together; (2) map services to the systems that host them; (3) identify which services are most critical.

1.1 Services at the practices

Nadia Kowalczyk is a technical trainee at the fictional Harbourside Technical College, placed with the fictional Linden Dental Group, which runs five dental practices. Her instructor, Daniel Mercer, asks her to start by listing services rather than devices. Linden's services include appointment booking, patient records, digital X-ray imaging, card payments, email and the staff rota. Each service is something people use to get work done. Thinking in services first helps Nadia see why each device matters, because a device is only important for the services it supports.

1.2 From services to systems

Nadia maps each service to the systems that host it. Patient records run on a cloud practice management system reached through a web browser. X-ray imaging uses a local imaging server in each practice connected to sensors in the surgeries. Payments use card terminals from a payment provider. Email is a cloud service. The rota is a spreadsheet on a shared drive. Grace Mwangi, Linden's IT manager, checks the map and adds a backup appliance in the head office that copies each practice's imaging server every night.

1.3 What is critical

Nadia asks practice managers which outage would stop work. Without patient records, dentists cannot see treatment history and appointments stall. Without imaging, many treatments cannot proceed safely. Payments can fall back to taking card details later by phone with the provider. The rota can be printed. She ranks records and imaging as critical, payments as important and the rest as supporting. The ranking tells Grace where to spend her limited time on resilience and protection, and it gives Nadia a frame for every later chapter.

Worked example

Nadia lists six services, maps them to hosting systems with Grace's correction and ranks records and imaging as critical.

Synthetic case. Linden, Harbourside and all people are synthetic.

Errors and limits

Service lists miss informal tools. Managers may overstate their own needs.

Exercises

EX001 — Services first. Why list services before devices?
Show marking criteria
Rubric: 3 = a device matters only for the services it supports;; 2 = purpose;; 1 = vague;; 0 = none.
EX002 — Grace's addition. What did Grace add to the map?
Show marking criteria
Rubric: 3 = a head office backup appliance copying imaging servers nightly;; 2 = backup;; 1 = vague;; 0 = none.
EX003 — Payment fallback. Why are payments not ranked critical?
Show marking criteria
Rubric: 3 = they can fall back to taking card details later by phone;; 2 = fallback;; 1 = unimportant;; 0 = none.
EX004 — Critical services. Which services are critical?
Show marking criteria
Rubric: 3 = patient records and imaging;; 2 = both;; 1 = email;; 0 = none.