What is a Network Communication Protocol?

Map Of Internet 1973


A network protocol is a protocol:

  • that describes the computer language
  • that will allow two or more computer processes to communicate together.

Protocols are instructions for multiple agents. Algorithms are instructions for single agents.

Manuel Blum #hlf14


A protocol has only one OSI level (Open Systems Interconnection)

Lower Level

These Protocols are in the lower Layer level of OSI (Open Systems Interconnection) and manipulate packets.

They implement packets:

  • Addressing,
  • routing
  • and traffic control

Example: The most known are the protocols in the Transport layer

These protocols communicate via sockets

Type Client Server Installation Machine
TCP/IP sockets Two different
UNIX domain sockets Same
Shared Memory Same

Using a Shared Memory segment allows for the best performance, but greater memory usage. Using UNIX domain sockets allows for improved performance over TCP/IP, but with less memory consumption than a shared memory segment connection.

Higher level

This higher level (mostly the Application Layer (level 7)) is a wrapper around the lower levels and exposes you with a message (and not with packet)






File Transfer


Naming directory

The banner is the first message that the server sends before any protocol exchange when a client connects.


A protocol being a process between multiple agents is visualized with all process diagrams such as:

Example of Sequence for the oauth code flow

sequenceDiagram participant Cli as Client participant RO as Resource Owner participant AS as Authorization Server participant RS as Resource Server Cli->>RO: (A) Send a Authorization Request RO->>Cli: (B) Get a Authorization Grant Cli->>AS: (C) Send the Authorization Grant AS->>Cli: (D) Get a Access Token Cli->>RS: (E) Send the Access Token RS->>Cli: (F) Get the Protected Resource

Operating System


Windows - System Information will list low network protocol (OSI Layer 4) such as:

Windows Network Protocol Sysinfo


Page 39, 2.1.2 - Book - Hopcroft, Motwani, Ullman, Automata Theory, Languages, and Computation 3rd Edition. pdf

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