OSI + TCP/IP Deep Dive

Master all OSI layers, TCP/IP stack behavior, and layer-mapped troubleshooting.

Intermediate Level

Master all 7 OSI layers and align them with real TCP/IP packet delivery behavior.

Click the numbered markers on each diagram to explore the concept step by step.

Advanced troubleshooting and incident response depend on accurate layer isolation.

Common confusion: Transport vs session

Fix: Transport manages delivery; session manages conversation state/context.

Common confusion: L2 problem appears as app failure

Fix: Lower-layer loss often propagates upward as app instability.

▸L1 Physical, L2 Data Link, L3 Network, L4 Transport, L5 Session, L6 Presentation, L7 Application.
▸Use each layer to isolate where failures occur in real incidents.

OSI 7-Layer Model

L7ApplicationHTTP, DNS, SMTP

L6PresentationTLS, MIME

L5SessionNetBIOS, RPC

L4TransportTCP, UDP

L3NetworkIP, ICMP

L2Data LinkEthernet, ARP

L1PhysicalCables, Radio

← Encapsulation (down) · Decapsulation (up) →

OSI vs TCP/IP

TCP/IP

Application

Transport

Internet

Network Access

OSI (equiv.)

Application · Presentation · Session

Transport

Network

Data Link · Physical

OSI	TCP/IP	Primary Function
Application + Presentation + Session	Application	App protocol and data formatting
Transport	Transport	End-to-end transport via TCP/UDP
Network	Internet	Logical addressing and routing
Data Link + Physical	Network Access	Frame delivery and signaling