Codecademy Logo

Networks and The Internet

OSI Model

The OSI Model is a conceptual, implementation-neutral model that describes networking in seven separate layers, where each layer covers a set of functions and tasks.

This model helps us communicate while we do network troubleshooting and architecture.

TCP/IP Model

The TCP/IP Model is an implementation-specific networking model that revolves around the TCP protocol and IP addressing which anchor the Internet as we know it.

Its layers include:

  • The Network Layer
  • The Internet Layer
  • The Transport Layer
  • The Application Layer

OSI Layers

The OSI layers include: Physical, Data Link, Network, Transport, Session, Presentation, and Application.

  • The Physical layer includes physical technologies
  • The Data Link layer includes data framing and local MAC addressing
  • The Network layer includes connecting to the larger web and IP addressing
  • The Transport layer includes protocols that make sure reliable delivery happens
  • The Session layer authenticates and maintains communication over a period of time
  • The Presentation layer en/decrypts and translates data into presentable form
  • The Application layer includes all the applications we interact with that render data

Network Categories

Three broad categories of networks include:

  • Local Area Network (LAN), a smaller-sized network that connects multiple devices in a small area
  • Campus Area Network (CAN), a larger network that connects multiple computers and devices over a slightly larger area
  • Wide Area Network (WAN), the largest-sized network that connects multiple computers, over a geographically large area

The Internet is technically a WAN.

Network

A network is two or more computers or devices that are linked in order to share information.

Networking refers to a large set of standards and protocols that organize and regulate the sharing of information.

Network Protocols

A network protocol is a set of standards for Internet traffic.

Among them are the big transport protocols:

  • TCP and UDP
  • HTTP for web requests
  • DNS to convert domain names to IP addresses
  • IMAP/POP3 for email
  • SSH
  • FTP
  • SMB for access to specific resources