Tcp Ip Model

TCP/IP Model — CCNA 200-301 Study Lesson The TCP/IP model is foundational to everything else on the CCNA exam — understanding how it maps to the OSI model, which protocols live at which layer, and how data is encapsulated and de-encapsulated will help you answer questions across every domain, not just Network Fundamentals. --- ## Why the TCP/IP Model Matters The exam tests the TCP/IP model both directly (identifying layers and protocols) and indirectly (troubleshooting, understanding how devices operate, explaining encapsulation). Because it underlies IP connectivity, security, and services topics, a weak grasp here creates gaps throughout the entire exam. --- ## The TCP/IP Model: Four Layers The TCP/IP model (also called the DoD model or Internet model) is the practical framework that real-world networking runs on. It has four layers, compared to the OSI model's seven. | TCP/IP Layer | OSI Equivalent Layers | Key Protocols / Examples | |---|---|---| | Application | Application, Presentation, Session (5–7) | HTTP, HTTPS, FTP, DNS, DHCP, SMTP, Telnet, SSH | | Transport | Transport (4) | TCP, UDP | | Internet | Network (3) | IP (IPv4/IPv6), ICMP, ARP | | Network Access | Data Link + Physical (1–2) | Ethernet, Wi-Fi (802.11), MAC addressing | > Note: Some textbooks and Cisco materials name the bottom layer "Link" or "Network Interface" — all refer to the same combined Layer 1+2 function. --- ## How the TCP/IP Model Relates to OSI The OSI model is the 7-layer reference model used for teaching and troubleshooting. The TCP/IP model is what is actually implemented in modern networks. Cisco exam questions may give you an OSI layer number or name and ask you to identify…