TCP/IP Model
The TCP/IP model is the practical model the Internet actually uses.
| TCP/IP layer | Maps to OSI layers | Protocols |
|---|---|---|
| Application | Application, Presentation, Session | HTTP, DNS, FTP, SMTP, SSH |
| Transport | Transport | TCP, UDP |
| Internet | Network | IP, ICMP, ARP |
| Network access (link) | Data link + Physical | Ethernet, Wi-Fi |
OSI vs TCP/IP
| OSI | TCP/IP |
|---|---|
| 7 layers | 4 layers |
| Reference model, designed before the protocols | Built around existing protocols |
| Clear distinction between service, interface and protocol | Less strict |
| Transport layer is connection-oriented only | Both connection-oriented (TCP) and connectionless (UDP) |
Four Levels of Addresses
Physical (MAC, 48-bit), logical (IP), port (16-bit, identifies a process) and specific (URL, email address).
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