OSI model and DoD model

OSI model and DoD (TCP/IP) model in computer networking.

OSI model

  • Layer 7: Application Layer
    • Protocol data unit: Data
    • Closest to end-users, high-level APIs (resource sharing, remote file access, directory services, virtual terminals)
    • Examples: dns, ftp, http, nfs, snmp, smtp, telnet, and etc.
  • Layer 6: Presentation Layer
    • Protocol data unit: Data
    • Translation of data between a networking service and an application, char encoding, data compression, and encryption/decryption
    • Examples: mime, ssl, tls, and etc.
  • Layer 5: Session Layer
    • Protocol data unit: Data
    • Managing communication sessions
    • Examples: sockets (session establishment)
  • Layer 4: Transport Layer
    • Protocol data unit: Segment(TCP)/Datagram(UDP)
    • Reliable transmission of data segments between points on a network (segmentation, acknowledgement, multiplexing)
    • Examples: tcp, udp, and etc.
  • Layer 3: Network Layer
    • Protocol data unit: Packet
    • Addressing, routing and traffic control
    • Examples: ip, icmp, ospf, rip, and etc.
  • Layer 2: Data Link Layer
    • Protocol data unit: Frame
    • Reliable transmission of data frames between two nodes connected by a physical layer
    • Examples: ppp, atm, mac, ieee 802.2 and etc.
  • Layer 1: Physical Layer
    • Protocol data unit: Bit
    • Transmission and receiption of raw bit streams over a physical medium
    • Examples: ethernet physical layer, isdn, and etc.

TCP/IP (DoD) model

  • Layer 4: Application Layer
    • dns, dhcp, ftp, http, ssh, telnet, smtp, and etc.
  • Layer 3: Transport Layer
    • tcp, udp, and etc.
  • Layer 2: Internet Layer
    • ip, icmp, ipsec, and etc.
  • Layer 1: Link Layer
    • arp, mac, ppp, and etc.