Computer networking application protocols

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Computer networking application protocols travel over computer networking end-to-end protocols to provide services meaningful to application programs residing in the endpoints. The application protocols differ in the kind of information they transfer (e.g., self-contained messages, computer files, remote procedure calls, spoken language, etc.). Note well that these are not directly accessible to a human user. To draw an analogy to postal mail, a person can drop an envelope into a mailbox, but has no access either to the mechanism between mailbox and post office, or post office to post office.

Application protocols also differ in their expectations of the performance end-to-end service below them. The application protocol may provide security, expect certain security services from the end-to-end or computer networking internetwork protocols over which they run, or both.

Classes of information transfer


Messages are self-contained units of data, which may contain other types of data.

Message handling protocols are analogous to postal protocols. Different protocols run among mail clients that provide a human interface; message transfer agents analogous to post offices, possibly at multiple levels of a hierarchy; and message stores, analogous to temporary mailboxes.

The major IETF message transfer paradigms and protocols include:

See messaging application protocols for further detail


Files are sequences of units of data.

Structured data

Remote procedure calls

Character- or bit-oriented interaction

Directory services

Network management services

Expectations of the end-to-end service


They may be tolerant or intolerant of impairments such as:

  • Latency
  • Bit errors
  • Packet loss
  • Sequencing of packets