OSI Reference Model - aljimenez28/champlain GitHub Wiki
The OSI Model is a framework that standardizes how data is transmitted and received over a network. It has 7 layers, each with a specific role.
Layer 7 – Application
- What it does: Interfaces with the end-user (apps like web browsers, email, etc.)
- Examples: HTTP, FTP, SMTP, DNS, POP3
- Think: This is what the user sees and interacts with
Layer 6 – Presentation
- What it does: Formats and encrypts data for the application layer
- Functions: Data translation, encryption/decryption, compression
- Examples: JPEG, SSL/TLS, MPEG
- Think: Translator for different data formats
Layer 5 – Session
- What it does: Manages sessions or connections between applications
- Functions: Start, maintain, and terminate sessions
- Examples: NetBIOS, RPC, PPTP
- Think: Phone call manager for app connections
Layer 4 – Transport
- What it does: Provides reliable delivery of data
- Functions: Error checking, flow control, retransmission
- Examples: TCP (reliable), UDP (fast but unreliable)
- Think: UPS/FedEx – ensures data is delivered properly
Layer 3 – Network
- What it does: Handles routing and addressing of packets
- Functions: IP addressing, routing, fragmentation
- Examples: IP, ICMP, OSPF, RIP
- Devices: Routers
- Think: GPS – picks the best path for data
Layer 2 – Data Link
- What it does: Moves frames across the local network
- Functions: MAC addressing, error detection (via CRC), framing
- Examples: Ethernet, PPP, ARP, VLAN
- Devices: Switches, Bridges
- Think: Post office clerk – adds address labels (MAC)
Layer 1 – Physical
- What it does: Sends raw bits (0s and 1s) over physical medium
- Functions: Electrical/optical signaling, cabling, pin layouts
- Examples: Cables, Hubs, NICs, Fiber optics
- Devices: Hubs, Repeaters, Physical network cards
- Think: Wires and plugs – the physical stuff
A way to remember the order: PLEASE DO NOT THROW SAUSAGE PIZZA AWAY