Network Standards & Protocols

📏 Why standards exist

Standards are agreed specifications that let equipment from different makers work together. IEEE writes standards such as 802.3 (Ethernet) and 802.11 (Wi-Fi). The IETF publishes the internet's protocols. ISO created the OSI model. Because of standards, any phone can join any Wi-Fi network.

📜 Common protocols

HTTP and HTTPS load web pages (HTTPS is the encrypted version). SMTP sends email; POP3 and IMAP collect it. FTP transfers files. DNS turns names into IP addresses. DHCP gives devices an IP address automatically when they join a network. TCP delivers data reliably and in order; UDP is faster but doesn't guarantee delivery, which suits video calls.

🧱 The TCP/IP model

The internet follows the four-layer TCP/IP model. Application: the protocols apps use (HTTP, SMTP, DNS). Transport: TCP or UDP split data into segments and use port numbers to reach the right app. Internet: IP addresses and routes packets across networks. Network access: sends frames over the actual medium, such as Ethernet or Wi-Fi.

🏢 The OSI model

OSI describes networking in seven layers: 7 Application, 6 Presentation (formats and encryption), 5 Session (manages conversations), 4 Transport, 3 Network, 2 Data link (frames and MAC addresses), 1 Physical (bits on the wire). OSI's top three layers map to TCP/IP's Application layer, and its bottom two to Network access.

📦 Encapsulation and decapsulation

When you send data, each layer wraps it with its own header on the way down: data becomes a segment (transport), then a packet (internet), then a frame (network access), then bits on the wire. The receiver unwraps the layers in reverse on the way up. This is called decapsulation.

Key points

• Standards let equipment from different makers work together.
• IEEE 802.11 is Wi-Fi, and 802.3 is Ethernet.
• HTTP loads pages, SMTP sends email, DNS finds addresses, and DHCP hands them out.
• TCP is reliable and ordered; UDP is fast but makes no promises.
• TCP/IP has four layers: application, transport, internet and network access.
• OSI has seven layers, from physical up to application.
• Each layer adds a header going down, and removes it coming up.

Try it for real: Inspect a real network

• On a computer, run ipconfig (Windows) or ifconfig (Mac or Linux) and find your IP address, subnet mask and default gateway.
• On a phone, open Wi-Fi settings: find the IP address that DHCP assigned and whether it uses 802.11n, ac or ax (if shown).