OSI Model Layers

Application Layer 7 - Purpose

Top layer of OSI, where users interact with apps like Chrome, Gmail, Zoom. Provides services like HTTP, SMTP, FTP.

Application Layer 7 - Devices

User applications themselves (software).

Application Layer 7 - Protocols

HTTP/HTTPS, SMTP, FTP, DNS, DHCP, SNTP, Telnet.

Presentation Layer 6 - Purpose

Makes sure data is in the right format; handles translation, compression, and encryption.

Presentation Layer 6 - Devices

End-user devices and software algorithms for encryption, compression, translation.

Presentation Layer 6 - Protocols

SSL/TLS, JPEG, MPEG, GIF, TIFF, ASCII, Unicode, HTML, MIME.

Session Layer 5 - Purpose

Manages communication: establishes, maintains, and ends sessions; handles authentication and authorization.

Session Layer 5 - Devices

Gateways, firewalls, PCs.

Session Layer 5 - Protocols

RPC, SCP, ASP, ZIP, NFCP.

Transport Layer 4 - Purpose

Ensures reliable delivery of data in correct order, breaks data into packets, assigns port numbers.

Transport Layer 4 - Devices

Multilayer switches (load balancers), firewalls, intrusion detection systems.

Transport Layer 4 - Protocols

TCP, UDP.

Network Layer 3 - Purpose

Decides best route for data using IP addresses, handles routing.

Network Layer 3 - Devices

Routers, ACLs.

Network Layer 3 - Protocols

IP, ICMP, RIP, OSPF, BGP.

Data Link Layer 2 - Purpose

Ensures correct data transfer within a local network, uses MAC addresses.

Data Link Layer 2 - Devices

NICs, bridges, switches, wireless access points.

Data Link Layer 2 - Protocols

Ethernet, PPP, ARP, MAC, Wi-Fi.

Physical Layer 1 - Purpose

Handles actual hardware that transmits/receives data using cables or wireless signals; converts data into electrical, light, or radio signals.

Physical Layer 1 - Devices

Transceivers, repeaters, hubs, media converters.

Physical Layer 1 - Protocols

Ethernet, Token Ring, RS-232, USB, Bluetooth.