T Level Digital: Network Layers, Packets and Protocols

The network content of the Pearson digital T Level cores goes below the cables and the topology: it asks how data actually crosses a network, layer by layer and packet by packet, and which protocol does which job. That content is shared by the Digital Software Development, Digital Support and Security and Digital Data Analytics cores, which are assessed through two written papers and an employer-set project. This material covers the models and protocols; a companion material on network types, topologies and models covers the physical side.

The quiz has twelve questions set in invented organisations. Three are about the layered models: which OSI layer routes packets by IP address, which layer compresses and encrypts a medical image before it is sent, and which OSI layers the TCP/IP application layer covers. Four follow packets across a network: why a video-calling firm carries live video over UDP, which header field lets the receiver put a file back together, why the packets of one email arrive out of order, and why a busy router drops packets during the evening peak. One asks what a receiver does when a cyclic redundancy check does not match. The last four are about protocols at work: IMAP for staff who read mail on several devices, a booking system reachable by IP address but not by name, SFTP for uploading a client's website, and why OSPF may choose a three-hop route over fast fibre when RIP picks two slow hops. Each explanation says what the right answer does and what the tempting alternative does instead.

The flashcards go through all seven OSI layers, the four TCP/IP layers and how they match, TCP against UDP, the parts of a packet, packet switching and packet loss, the CRC and each protocol named in the core content.

The written work has eight tasks to answer on paper: the jobs of the transport, network and data link layers; OSI against TCP/IP and why layers help; how a file crosses the internet by packet switching; why a bank uses TCP and HTTPS while a video app uses UDP; diagnosing a DHCP fault on one day and a DNS fault on the next; and the secure versions of HTTP and FTP. Two are longer, evaluative answers of the kind used for the higher-mark questions: POP against IMAP for staff with several devices, and RIP against OSPF for a network of forty routers. Each has a model answer and the points a marker would look for.

There is also a short oral practice with an examiner, who asks one question at a time and gives brief feedback at the end.

• State the function of each OSI layer and name protocols or devices that work at it
• Map the four TCP/IP layers onto the OSI model
• Describe the contents of a packet and explain packet switching, packet loss and error detection with a CRC
• Choose between TCP and UDP for an application
• Match HTTP, HTTPS, SMTP, POP, IMAP, FTP, SFTP, DHCP and DNS to their jobs and diagnose which has failed
• Compare the routing protocols RIP and OSPF

Practice material written by Zestly, based on the core content of the Pearson T Level Technical Qualifications in Digital Software Development, Digital Support and Security and Digital Data Analytics (first teaching September 2025), content area 7.3: the OSI and TCP/IP models, data packets and common network protocols.