Esteban Herlein

Addicted to discovering, learning and understanding technologies.

2 minute read

The OSI model defines the application layer as the user interface responsible for displaying received information to the user.

In contrast, the Internet Protocol model does not concern itself with such detail.

An application layer is an abstraction layer that specifies the shared protocols and interface methods used by hosts in a communications network. The application layer abstraction is used in both of the standard models of computer networking; the Internet Protocol Suite (TCP/IP) and the Open Systems Interconnection model (OSI model).

Although both models use the same term for their respective highest level layer, the detailed definitions and purposes are different.

In TCP/IP, the application layer contains the communications protocols and interface methods used in process-to-process communications across an Internet Protocol (IP) computer network. The application layer only standardizes communication and depends upon the underlying transport layer protocols to establish host-to-host data transfer channels and manage the data exchange in a client-server or peer-to-peer networking model. Though the TCP/IP application layer does not describe specific rules or data formats that applications must consider when communicating, the original specification (in RFC 1123) does rely on and recommend the robustness principle for application design.

In the OSI model, the definition of the application layer is narrower in scope. The OSI model defines the application layer as the user interface responsible for displaying received information to the user. In contrast, the Internet Protocol model does not concern itself with such detail. OSI also explicitly distinguishes additional functionality below the application layer, but above the transport layer at two additional levels; the session layer and the presentation layer. OSI specifies a strict modular separation of functionality at these layers and provides protocol implementations for each layer.

Protocols

  • Bitcoin Digital currency
  • BitTorrent peer-to-peer file sharing
  • CFDP Coherent File Distribution Protocol
  • CoAP Constrained Application Protocol
  • DDS Data Distribution Service
  • DeviceNet automation industry protocol
  • eDonkey classic file sharing protocol
  • FastTrack filesharing, known from KaZaa and more
  • Finger User Information Protocol
  • Freenet censorship resistant p2p network
  • FTAM File Transfer Access and Management
  • Gopher Gopher protocol
  • HL7 Health Level Seven
  • HTTP HyperText Transfer Protocol
  • H.323 Packet-Based Multimedia Communications System
  • IRCP Internet Relay Chat Protocol
  • Kademlia p2p hashtables
  • LDAP Lightweight Directory Access Protocol
  • LPD Line Printer Daemon Protocol
  • MIME (S-MIME) Multipurpose Internet Mail Extensions and Secure MIME
  • Modbus Serial communications protocol
  • MQTT Protocol MQ Telemetry Transport
  • Netconf Network Configuration Protocol
  • NFS Network File System
  • NIS Network Information Service
  • NNTP Network News Transfer Protocol
  • NTCIP National Transportation Communications for Intelligent Transportation System Protocol
  • NTP Network Time Protocol
  • OSCAR AOL Instant Messenger Protocol
  • PNRP Peer Name Resolution Protocol
  • RDP Remote Desktop Protocol
  • RELP Reliable Event Logging Protocol
  • RIP Routing Information Protocol
  • Rlogin Remote Login in UNIX Systems
  • RPC Remote Procedure Call
  • RTMP Real Time Messaging Protocol
  • RTP Real-time Transport Protocol
  • RTPS Real Time Publish Subscribe
  • RTSP Real Time Streaming Protocol
  • SAP Session Announcement Protocol
  • SDP Session Description Protocol
  • SIP Session Initiation Protocol
  • SLP Service Location Protocol
  • SMB Server Message Block
  • SMTP Simple Mail Transfer Protocol
  • SNTP Simple Network Time Protocol
  • SSH Secure Shell
  • SSMS Secure SMS Messaging Protocol
  • TCAP Transaction Capabilities Application Part
  • TDS Tabular Data Stream
  • Tor anonymity network
  • TSP Time Stamp Protocol
  • VTP Virtual Terminal Protocol
  • Whois (and RWhois) Remote Directory Access Protocol
  • WebDAV Web Distributed Authoring and Versioning
  • X.400 Message Handling Service Protocol
  • X.500 Directory Access Protocol (DAP)
  • XMPP Extensible Messaging and Presence Protocol

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