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networkingNODE: #layer-7-application

OSI Layer 7: Application Layer

The topmost layer of the OSI model directly interacting with software applications to provide end-user network services.

AKA:Layer 7, L7, Application Layer
#networking#osi-layers#protocols#http#dns
GRAPH_RELATIONS // CONNECTED_NODESLINKED
PART OF:
↳Open Systems Interconnection (OSI) Model
RELATED TO:
↳OSI Layer 6: Presentation Layer

OSI Layer 7: Application Layer

Definition

The Application Layer is the layer closest to the end user. It provides network services directly to applications such as web browsers, email clients, and remote shells. It does not mean the application software itself, but the protocols the application utilizes.

Key Functions

  • Service Advertising & Discovery: Enabling apps to locate network services.
  • Resource Sharing: File sharing, remote database access, and print services.
  • Communication Management: Handling high-level message exchange formats.

Common Protocols

  • HTTP/HTTPS: Web document retrieval and REST APIs.
  • DNS: Domain name to IP resolution.
  • SMTP/IMAP/POP3: Electronic mail transmission and retrieval.
  • SSH/Telnet: Secure remote terminal access.
  • FTP/SFTP: File transfer.
  • DHCP: Dynamic host configuration and IP assignment.

Protocol Data Unit (PDU)

  • Data / Message

Adjacent Layers

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