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How to draw a network or system diagram

A network or system diagram shows the parts of a system and how they connect. Not examined as a drawing question in our 2025 bank but useful for web architecture and security short answers.

What it looks like in the real exam

Reasoned No 2025 NESA question in our bank asks you to draw a network diagram. Know the idea because web, security and protocol questions often describe such a system in words, and you may need to explain where a firewall or HTTPS fits.

What to show

ItemHow to draw it
Device or serverA labelled box or icon (Client, Router, Web server, Database server)
ConnectionA line between devices
Label on a connectionThe protocol or data (HTTPS request, SQL query)
Security controlShow it where it sits (firewall on the router, encrypted link)

Method

  1. List the parts in the scenario: who requests, who serves, where data lives. General advice
  2. Draw them left to right in the path of a request. General advice
  3. Join them with lines and label the protocol (HTTP/HTTPS, SQL, SMTP). General advice
  4. Mark security controls (firewall, HTTPS, an internal-only database link). General advice
  5. Check every device and link is labelled.

Worked example: a web application (original)

Clientbrowser or appRouterand firewallInternetWeb serverFlask appDatabaseserverHTTPS requestthen an SQL queryinternal network onlyLabel every device, every connection, and what travels on it (protocol or data). Show where security controls sit (firewall, HTTPS).
Simple network and system diagram: client, router with firewall, the internet, web server, database server, with the protocol labelled on each link

Markers’ checklist

  • Every device labelled.
  • Every connection drawn and labelled with a protocol or data.
  • Security controls placed correctly.
  • Direction of the request is clear.

Common mistakes

  • General advice Putting the database directly on the internet side.
  • General advice Unlabelled connections.

Time per mark

Derived The paper averages 1.75 minutes per mark (140 minutes ÷ 80 marks), so a 3-mark drawing question is about 5.3 minutes in total. General advice Suggested split: 1 minute reading and planning, most of the time drawing, and the last minute checking labels against the checklist. Drawing in an online tool is slower than on paper, so practise with the tool on NESA’s familiarisation site.

Practice (2 prompts, with answers)

Item 1

Show how an email travels from a sender to a receiver.

Show the answer

Sender’s email client → (SMTP) → sender’s mail server → (SMTP) → receiver’s mail server → (IMAP or POP3) → receiver’s email client. Original practice Protocol names are standard; check the exact set your course lists.

Item 2

Where should a firewall go in the web application diagram, and why?

Show the answer

Between the internet and the internal network (on the router), so it filters traffic before it reaches the web and database servers. Original practice

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