1.3. The TCP/IP Model: How Real Networks Work
đź’ˇ First Principle: While OSI is great for understanding concepts, the TCP/IP model is what actually runs the internet. It collapses OSI's seven layers into four practical ones. The exam expects you to map protocols to TCP/IP layers and understand that TCP/IP is what you configure on real devices.
What happens when you confuse the models: You see a question asking "which TCP/IP layer handles IP addressing?" If you're thinking OSI (Layer 3 = Network), you might miss that TCP/IP calls this the "Internet" layer. Or a question asks about "Network Access" layer—that's TCP/IP's combined Layer 1+2, not the OSI Network layer. Model confusion costs exam points.
Think of OSI as the architectural blueprint and TCP/IP as the actual building. The blueprint has more detail, but the building is what you live in. When you configure a real router, you're working with TCP/IP concepts.
Loading diagram...
TCP/IP Layers and Common Protocols:
| TCP/IP Layer | OSI Equivalent | Common Protocols | Device |
|---|---|---|---|
| Application | 7, 6, 5 | HTTP, HTTPS, DNS, DHCP, SNMP, SSH, Telnet, FTP, TFTP | — |
| Transport | 4 | TCP (port 80, 443, 22), UDP (port 53, 67, 69) | — |
| Internet | 3 | IPv4, IPv6, ICMP, OSPF, EIGRP | Router |
| Network Access | 2, 1 | Ethernet, 802.11 (Wi-Fi), ARP | Switch, NIC |
⚠️ Exam Trap: ARP (Address Resolution Protocol) is often tested. It maps IP addresses to MAC addresses and operates at the boundary between Layer 2 and Layer 3. Remember: ARP answers the question "What MAC address belongs to this IP address?"