OSI model
The Open Systems Interconnection model is the conceptual framework that everything in networking is built on. Seven layers. Each with a job. Click any layer to inspect its protocols, what it actually does, and how it shows up in the real world.
Click a layer to inspect
Packet journey
Step through how a real HTTPS request travels down the OSI stack from your browser to the wire, one layer at a time.
HTTPS GET request, full stack walkthrough
Browser initiates HTTP GET
Your browser constructs an HTTP GET request for the URL. This happens entirely at the Application layer — the browser doesn't yet know or care how the bytes will travel.
Quick reference
| # | Layer | PDU | Addressing | Key protocols |
|---|---|---|---|---|
| 7 | Application | Data | URL / FQDN | HTTP, HTTPS, DNS, SMTP, FTP, SNMP |
| 6 | Presentation | Data | — | TLS/SSL, JPEG, ASCII, MPEG |
| 5 | Session | Data | — | NetBIOS, RPC, PPTP |
| 4 | Transport | Segment | Port number | TCP, UDP, SCTP |
| 3 | Network | Packet | IP address | IP, ICMP, OSPF, BGP, EIGRP |
| 2 | Data Link | Frame | MAC address | Ethernet, 802.11, ARP, STP, VLAN |
| 1 | Physical | Bit | — | DSL, SONET, 802.3, 802.11 (PHY) |