OSI Model

Layer 7: Application

• Describes the interface between two applications on separate computers.
• Payload
• Protocols include: HTTP, SMTP, POP3, IMAP4, FTP, Telnet, and RDP

Layer 6: Presentation

• Responsible for reformatting, compressing, and/or encrypting data so that the receiving application can use it.

Layer 5: Session

• Protocols at this layer coordinate and maintain communications between nodes on the network.

Layer 4: Transport

• Responsible for transporting application layer payloads from one application to another.
• Segment, User Datagram Protocol
• Protocols include: TCP, UDP

Layer 3: Network

• Responsible for moving messages from one node to another until they reach destination host.
• Packet
• Protocols include: IP, ICMP, ARP

Layer 2: Data Link

• Layers 2 and 1 are responsible for interfacing with the physical hardware only on the local network. These are programmed into the firmware of the NIC and other hardware.
• Frame
• Protocols include Ethernet, Wi-Fi

Layer 1: Physical

• Responsible for sending bits using wired or wireless transmission.