Wired and wireless networks, protocols and layers — OCR GCSE Computer Science

Wired connection means devices link using a physical cable, most commonly copper Ethernet cable such as Cat5e or Cat6 with RJ45 connectors, or fibre-optic cable for long distances and high bandwidth. Data travels as electrical signals in copper or as light pulses in fibre, giving a stable, private medium that is hard to intercept without physical access. Wired links usually give higher and more consistent bandwidth, lower latency and less interference than wireless, which suits fixed devices such as desktop computers, servers, printers and access points. The trade-off is that cables restrict movement, need installation and can be costly or awkward to route. In an exam, describe the medium, the connector or cable type, and compare performance and security with wireless.

Ethernet is the family of protocols and standards used for wired local area networks. It defines how devices format and transmit frames over a shared medium, using MAC addresses to identify network interface cards. Ethernet commonly runs over copper twisted-pair cable with RJ45 connectors at speeds such as 100 Mbps, 1 Gbps or 10 Gbps, and over fibre for longer links. Wireless networking uses radio waves instead of cables, typically following the IEEE 802.11 standards known as Wi-Fi, with devices connecting through a wireless access point. Bluetooth is another wireless standard used for short-range personal area networks, such as connecting a phone to headphones. Wireless gives mobility and easy installation but can suffer interference, weaker security and variable bandwidth.

Wi-Fi is a family of wireless networking technologies that lets devices join a local area network and exchange data through radio waves instead of cables. A device needs a wireless network interface and must associate with an access point, which broadcasts a network name (SSID) and manages traffic. Data is carried on radio channels, and security protocols such as WPA2 or WPA3 encrypt transmissions so that eavesdroppers cannot easily read them. Wi-Fi is convenient because many users can connect without cabling, but signal range is limited by walls and distance, and performance can fall when many devices share one channel. In an exam answer, link Wi-Fi to a specific context, for example a school laptop connecting to a classroom access point, and explain both the benefit of mobility and a limitation such as interference or reduced security compared with a wired link.

Bluetooth is a short-range wireless technology that lets devices form a personal area network and exchange data directly. It uses radio waves in the 2.4 GHz band and is designed for low power consumption, which suits battery-powered devices such as wireless earbuds, keyboards, fitness trackers and car systems. To connect, devices go through pairing, often involving a shared passcode or confirmation, and then create a small network called a piconet in which one device takes the master role and others are slaves. Because range is typically only a few metres and data rates are lower than Wi-Fi, Bluetooth is used for close-range links rather than general internet access. In an exam answer, explain the pairing process and link the technology to a suitable context, such as streaming audio from a phone to headphones, while noting limitations such as short range and possible interference.

Encryption scrambles data into ciphertext so that anyone intercepting it cannot read the original plaintext. A key controls the scrambling and unscrambling. In a network context, encryption protects data in transit. For example, when a browser opens an HTTPS connection, the client and server agree a session key and all later traffic is encrypted. Students should be able to describe what encryption does, why it matters on wired and wireless networks, and how keys relate to the process. The OCR J277 specification places encryption under 1.3.2 Wired and wireless networks, protocols and layers, and does not require knowledge of symmetric and asymmetric encryption at GCSE.

Every device needs an address to route data. An IP address is a logical address, often assigned by a DHCP server, which can change when joining a new network. Routers use it to forward packets. IPv⁴ uses 32 bits (e.g. 192.168.1.10), but due to address exhaustion, IPv⁶ was created using 128 bits in hexadecimal. A MAC address is a physical address burned into the network interface card (NIC) by the manufacturer. It is fixed and used within a local network to identify the exact hardware. Students must compare these addresses, know their formats, and explain why IPv⁶ is needed.

Standards are agreed, documented specifications that allow hardware and software from different manufacturers to interoperate on a network. Without them, devices could use incompatible signalling or data formats and fail to communicate. Standards cover physical properties, such as Ethernet cable connectors and Wi-Fi radio frequencies, and logical properties, such as data formats and the rules that protocols follow. For example, because manufacturers follow Wi-Fi standards, a smartphone from one vendor can connect to a wireless router from another. Standards therefore improve compatibility and make network behaviour predictable, which simplifies troubleshooting. Note the distinction: a protocol is a specific set of communication rules, while a standard is the broader agreed specification that a protocol may conform to.

A protocol is a set of rules for how devices exchange data. TCP/IP is the core suite: IP addresses and routes packets between networks, while TCP splits data into segments, numbers them and reassembles them, requesting retransmission of lost segments. HTTP transfers web pages between a browser and a web server; HTTPS does the same but encrypts the traffic using TLS, protecting passwords and card details. FTP moves files between a client and a server, often for uploading website content. POP downloads email from a server to one device, typically removing it from the server. IMAP keeps email on the server and synchronises folders and read status across multiple devices. SMTP sends outgoing email from a client to a server and between servers. In the exam you may match a protocol to a task or explain the difference between two similar protocols.

Layering splits network communication into separate jobs so each layer handles one concern and offers services to the layer above. A common model has four layers: application (HTTP, FTP, SMTP), transport (TCP, UDP), network (IP) and link (Ethernet, Wi-Fi). When you send a message, data passes down the stack: each layer adds its own header, a process called encapsulation. The receiving device passes data up, and each layer removes and acts on its header. This means a web browser only needs HTTP, while the link layer worries about cables and radio. Layers are self-contained, so a change in one layer, such as swapping copper for fibre, need not affect the others. Standard interfaces between layers let different vendors' hardware and software interoperate, which is why the internet works across mixed equipment.