Network Models & Protocols

Network Models are simplified representations that help organize and explain the complex system of protocols used in data communication.

There are two main models used in networking: the OSI Model and the TCP/IP Model.

  • The OSI Model is primarily a reference model used for understanding and designing network systems, and is mainly used for educational and conceptual purposes.
  • The TCP/IP Model represents the practical implementation used in modern networks today.

Protocols are formal rules or standards that define how data is transmitted and received over a network. They enable communication between devices, ensuring data is sent, received, and interpreted correctly, regardless of hardware or software differences.

Comparing the Two Models

The OSI Model

The Open Systems Interconnection (OSI) model is a seven-layer conceptual framework that standardizes the functions of a communication system, enabling interoperability between different devices and software.

  • Application Layer (7) - The Application Layer is the human-computer interaction layer, where applications can access the network services.
  • Presentation Layer (6) - The Presentation Layer ensures that data is in a usable format and this is also where data encryption occurs.
  • Session Layer (5) - The Session Layer maintains connections and is responsible for controlling ports and sessions.
  • Transport Layer (4) - The Transport Layer transmits data using transmission protocols including TCP and UDP.
  • Network Layer (3) - The Network Layer decides which physical path the data will take.
  • Data Link Layer (2) - The Data Link Layer defines how data is formatted and transmitted over the network.
  • Physical Layer (1) - The Physical Layer transmits raw bit streams over the physical medium.

The TCP/IP Model

The Transmission Control Protocol (TCP) / Internet Protocol (IP) model is a four-layer model for network communication. Each layer has a specific function, from providing application-level protocols to handling physical data transmission and ensuring end-to-end communication. TCP/IP is a suite of protocols that forms the foundation of the internet, providing reliable data transmission.

  • Application Layer - Combines the functions of the OSI Application, Presentation, and Session Layers.
  • Transport Layer
  • Internet Layer
  • Network Access - Combines the functions of the OSI Data Link and Physical Layers.

Protocols By Layer

Application Layer Protocols

Application Layer protocols are responsible for enabling communication between user applications and the network by defining the rules for data formatting, transmission, and processing. They act as the interface between applications like web browsers or email clients and the underlying network services, ensuring that diverse software can interact and exchange data effectively.

Hypertext Transfer Protocol (HTTP & HTTPS)

Hypertext Transfer Protocol (HTTP) is a communication protocol for transferring information over the internet, acting as a rulebook for communication between a client and a server.

HTTP uses a request-response model where the browser sends a request for a resource, and the server sends back a response containing the requested content.

HTTPS is a secure version of HTTP using SSL/TLS.

File Transfer Protocol (FTP & FTPS & SFTP)

File Transport Protocol (FTP) is a communication protocol used for transferring files between computers.

File Transfer Protocol Secure (FTPS) is an extension of FTP that uses SSL/TLS for encryption.

Secure File Transfer Protocol (SFTP) uses SSH to provide secure file transfers.

Simple Mail Transfer Protocol (SMTP)

Simple Mail Transfer Protocol (SMTP) is a communication protocol used for sending emails.

Domain Name System (DNS)

The Domain Name System (DNS) translates domain names (like google.com) to IP addresses.

Secure Shell (SSH)

Secure Shell (SSH) provides encrypted remote access.

Transport Layer Protocols

Transport Layer Protocols are responsible for end-to-end communication between applications, ensuring reliable data delivery, flow control, and error correction. They segment large data streams into smaller segments for transmission and reassemble them at the destination, manage the rate of data transfer to prevent congestion, and handle the connection establishment, maintenance, and termination.

Transmission Control Protocol (TCP)

Transmission Control Protocol (TCP) is a communication protocol that ensures reliable, connection-oriented communication.

User Datagram Protocol (UDP)

User Datagram Protocol (UDP) is a communication protocol that ensures faster, connectionless communication.

Internet Layer Protocols

Internet Layer Protocols are responsible for addressing and routing data packets across different networks to ensure they reach their correct destination. They manage the logical addressing of devices and the forwarding of packets from a source to a destination network, providing the "best-effort" delivery service that does not guarantee reliability.

Internet Protocol (IP)

Internet Protocol (IP) is a communication protocol that defines the addressing and routing of packets. IP assigns unique addresses to devices and routes packets across the network.

  • IPv4 - The fourth version of the Internet Protocol, still widely used today alongside IPv6, which routes data packets on the internet and other networks. It uses 32-bit addresses, commonly written in a dotted decimal format (192.168.0.1), to uniquely identify devices and enable them to communicate with each other. These addresses have two parts: a network prefix and a host number.
  • IPv6 - The next generation Internet protocol designed to replace the older IPv4 system. It provides a much larger address space to support the growing number of internet-connected devices, as well as to improve efficiency and security. Uses 128-bit addresses, written as eight groups of four hexadecimal digits separated by colons (2620:cc:8000:1c82:544c:cc2e:f2fa:5a9b).

Internet Control Message Protocol (ICMP)

Internet Control Message Protocol (ICMP) is used for diagnostic and error-reporting functions, such as ping and traceroute.

Address Resolution Protocol (ARP)

Address Resolution Protocol (ARP) is used to map IP addresses to physical MAC addresses on a local network.

Network Access Layer Protocols

Network Access Layer Protocols are responsible for physical transmission of data and error detection.

Ethernet

Ethernet is a technology for connecting devices in a wired computer network, such as home or office local area network (LAN).

Wi-Fi

Wi-Fi is a family of wireless network protocols based on the IEEE 802.11 family of standards, which are commonly used for local area networking of devices and Internet access, allowing nearby digital devices to exchange data by radio waves.

Point-to-Point Protocol (PPP)

Point-to-Point Protocol (PPP) is used for direct data link connections between two nodes.

Security Protocols

Security protocols ensure secure communication over potentially insecure networks.

Secure Sockets Layer (SSL) / Transport Layer Security (TLS)

Secure Sockets Layer (SSL) is a security protocol that encrypts data transferred between a user's web browser and a website, ensuring confidentiality, integrity, and authentication. SSL is deprecated.

Transport Layer Security (TLS) is the successor to SSL, providing encryption and authentication for secure web communications (HTTPS).

Secure Shell (SSH)

Secure Shell (SSH) is a cryptographic network protocol for operating network services securely over an unsecured network.