| Full name | Open Systems Interconnection | Transmission Control Protocol / Internet Protocol |
| Created by | ISO & CCITT (now ITU-T) | DARPA / Vint Cerf & Bob Kahn |
| Year | 1984 (finalized) | 1974 (RFC 675), refined 1978–1983 |
| Purpose | Universal reference/teaching model; vendor-neutral interoperability standard | Practical protocol suite to interconnect ARPANET nodes; basis for the modern Internet |
| Motivation | IBM's SNA, DEC's DECnet, and others were proprietary; ISO wanted a universal framework so any vendor's hardware could talk to any other's | US DoD needed resilient, survivable communication that could reroute around damaged nodes; existing protocols were brittle |
| Layers | 7 (Physical, Data Link, Network, Transport, Session, Presentation, Application) | 4 (Network Access, Internet, Transport, Application) |
| Layer mapping | Strict 1-to-1 separation of concerns | OSI layers 5-6-7 collapsed into Application; layers 1-2 collapsed into Network Access |
| Data unit names | Bits, Frames, Packets, Segments, Data, Data, Data | Frames, Datagrams, Segments, Messages |
| Transport protocols | Model defines—doesn't specify | TCP (reliable) and UDP (unreliable/fast) |
| Adoption | Reference model; actual OSI protocol stack rarely deployed | De facto standard; powers the entire Internet |
| Strengths | Clear separation of concerns, excellent for teaching, vendor-neutral | Proven at Internet scale, simple, flexible |
| Weaknesses | Complex, late to market, never widely implemented as actual protocols | No clear separation of service/interface/protocol; security bolted on later |
| Session/Presentation | Explicit separate layers | Application layer handles both (e.g., TLS ≈ Presentation, RPC ≈ Session) |
| Modern relevance | Foundation for network engineering education, troubleshooting framework | The running Internet—every device uses TCP/IP |