OSI Application Protocol Layer

An OSI Application Protocol Layer is an abstraction layer that specifies shared communication protocols and interface methods for enabling network hosts to exchange application data.

Context:
- It can implement Network Protocol through application protocols.
- It can provide Interface Method through protocol handlers.
- It can support Host Communication through service endpoints.
- It can enable Data Exchange through network services.
- It can manage Resource Access through access controls.
- It can ensure Device Identification through discovery protocols.
- It can validate Network Interface through interface checkers.
- It can maintain Data Integrity through error recoverys.
- ...
- It can often handle Session Management through connection handlers.
- It can often control Data Flow through flow controls.
- It can often ensure Message Integrity through error checkings.
- It can often maintain Service Quality through performance monitors.
- It can often provide Authentication Service through security protocols.
- ...
- It can range from being a Simple Protocol Layer to being a Complex Protocol Layer, depending on its protocol complexity.
- It can range from being a Basic Service Layer to being an Advanced Service Layer, depending on its service capability.
- It can range from being a TCP/IP Model Layer to being an OSI Model Layer, depending on its architectural model.
- ...
- It can integrate with Transport Layer for reliable delivery.
- It can work with Presentation Layer for data formatting.
- It can interact with Session Layer for connection management.
- ...
Examples:
- Service Implementation Types, such as:
  - Common Application Service Elements, such as:
    - Remote Operation Services for distributed operations.
    - Data Transfer Services for data movement.
  - Specific Application Service Elements, such as:
    - File Transfer Services for file operations.
    - Database Access Services for data retrieval.
- Protocol Implementations, such as:
  - Web Protocols, such as:
    - HTTP Protocol for web communication.
    - HTTPS Protocol for secure web communication.
  - File Transfer Protocols, such as:
    - FTP Protocol for file transfer.
    - SFTP Protocol for secure file transfer.
  - Email Protocols, such as:
    - SMTP Protocol for email transmission.
    - POP3 Protocol for email retrieval.
- Network Services, such as:
  - Directory Services, such as:
    - DNS Service for name resolution.
    - LDAP Service for directory access.
  - Authentication Services, such as:
    - Kerberos Service for network authentication.
    - OAuth Service for authorization protocol.
- ...
Counter-Examples:
- Transport Layer, which manages data transmission but not application logic.
- Network Layer, which handles packet routing but not application services.
- Data Link Layer, which controls physical transmission but not application protocols.
See: OSI Model, Abstraction Layer, Communication Protocol, Interface (Computing), Host (Network), Internet Protocol Suite.

References

2025

(Wikipedia, 2025) ⇒ https://en.wikipedia.org/wiki/application_layer Retrieved:2025-1-29.
- An application layer is an abstraction layer that specifies the shared communication protocols and interface methods used by hosts in a communications network. An application layer abstraction is specified in both the Internet Protocol Suite (TCP/IP) and the OSI model. Although both models use the same term for their respective highest-level layer, the detailed definitions and purposes are different.