7. Application Layer

• Application

  • interface between the applications and user

  • data format, compression and encryption (presentation)

  • dialog between source and destination application (session)

• Hypertext Transfer Protocol (HTTP)

  • port 80

  • request/response protocol

  • HTTPS 443

• Email

  • Simple Mail Transfer Protocol (SMTP)

    • Sending email

    • port 25

  • Post Office Protocol (POP)

    • Receive email

    • port 110

  • Internet Message Access Protocol (IMAP)

    • Receive email

    • port 143

  • Mail User Agent (MUA)

  • Mail Transfer Agent (MTA)

  • Mail Deliver Agent (MDA)

• Domain Name System (DNS)

  • resolve name to IP

  • fully-qualified domain names

  • distributed set of servers

  • nslookup

• Dynamic Host Configuration Protocol (DHCP)

  • obtain IP automatically

• File Transfer Protocol (FTP)

  • data transfers between a client and a server

  • port 20 (data) and 21 (control)

• Server Message Block (SMB)

  • Sharing protocol