OSI Model

• Layer 7 - Application: Interface for receiving and sending data
  • Responsible for providing the protocols for applications to transmit traffic, HTTP is a layer 7 protocol.
• Layer 6 - Presentation: Formatting of the data & encryption
  • SSL and TLS (encryption protocols. The session is established in Layer 5 and formatted in layer 6)
• Layer 5 - Session: Tracking of packets
  • Session based protocols for application communication like SMB and RPC.
• Layer 4 - Transport: End to end communication between devices
  • TCP is layer 4 as it manages overall communication - Providing error control, assigning ports and sequences, and ensuring data is delivered correctly. UDP is also Layer 4 as it manages overall communication for its sub-protocols (eg. DNS)
• Layer 3 - Network: Logical addressing and routing of packets (IP Addresses)
  • IP & ICMP are network layer protocols.
• Layer 2 - Data link: Hardware addressing (MAC addresses)
  • Ethernet, Frame Relay, & Wi-Fi would be considered Data link layer protocols.
• Layer 1 - Physical: Physical connection / media type

TCP/IP Model

• Application Layer (Provides all of the functions of OSI's L5, L6, and L7)
  • OSI Application Layer (L7)
  • OSI Presentation Layer (L6)
  • OSI Session Layer (L5)
• Transport Layer
  • OSI Transport Layer (L4)
• Internet Layer
  • OSI Network Layer (L3)
• Network Access Layer
  • OSI Data Link Layer (L2)
  • OSI Physical Layer (L1)