OSI Model

The 7-layer reference model for network communication.

Memory Aid (Layer 7 to 1): "All People Seem To Need Data Processing" — Application, Presentation, Session, Transport, Network, Data Link, Physical

Layer	Name	Protocols / Standards	PDU	Devices	Aid
7	Application	HTTP, HTTPS, FTP, SMTP, DNS, DHCP, SNMP, SSH, Telnet, POP3, IMAP, LDAP, RDP, SIP, NTP	Data	Firewalls (L7), Load Balancers, WAF, Proxy Servers	All
6	Presentation	SSL/TLS, JPEG, GIF, PNG, MPEG, ASCII, EBCDIC, encryption, compression	Data	Gateways (encryption)	People
5	Session	NetBIOS, PPTP, L2TP, RPC, SCP, NFS, SQL sessions, SMB	Data	Gateways	Seem
4	Transport	TCP, UDP, TLS (handshake), SCTP	Segment (TCP) / Datagram (UDP)	Firewalls (L4), Load Balancers	To
3	Network	IP (IPv4/IPv6), ICMP, IGMP, IPSec, OSPF, BGP, RIP, EIGRP	Packet	Routers, Layer 3 Switches	Need
2	Data Link	Ethernet (802.3), Wi-Fi (802.11), ARP, PPP, Frame Relay, STP, VLAN (802.1Q), MAC	Frame	Switches, Bridges, NICs, WAPs	Data
1	Physical	Ethernet (physical), USB, DSL, ISDN, Bluetooth, RS-232, fiber optic standards	Bits	Hubs, Repeaters, Cables, Modems, Patch Panels	Processing