The TCP/IP model, also known as the Internet Protocol Suite, is the conceptual framework for networks that underpins the internet and many local area networks. Unlike the OSI model, which is more theoretical and divides the networking process into seven layers, the TCP/IP model has four layers. Each layer corresponds to one or more layers in the OSI model. Here’s a breakdown:
Application Layer (corresponds to OSI’s Application, Presentation, and Session layers)
- This is the top layer of the TCP/IP model.
- Provides the interface between the applications we use and the underlying network over which our messages are transmitted.
- Protocols and services include: HTTP, FTP, SMTP, POP3, DNS, DHCP, and many others.
Transport Layer (corresponds to OSI’s Transport layer)
- Responsible for end-to-end communication and flow control.
- Ensures that messages are delivered error-free, in sequence, and with no losses or duplications.
- The most common protocols at this layer are TCP (Transmission Control Protocol) and UDP (User Datagram Protocol).
Internet Layer (corresponds to OSI’s Network layer)
- Also sometimes called the Network Layer.
- Responsible for routing data packets between devices, often through multiple nodes and networks.
- Deals with IP addresses and routing.
- Key protocols include IP (Internet Protocol, both IPv4 and IPv6), ICMP (Internet Control Message Protocol), and ARP (Address Resolution Protocol).
Network Access Layer (corresponds to OSI’s Data Link and Physical layers)
- Also sometimes referred to as the Link Layer or Network Interface Layer.
- Deals with protocols that are specific to the network type (e.g., Ethernet, Wi-Fi) and how data is physically sent and received over that network, including addressing (like MAC addresses), error detection, and framing.
- Includes protocols and technologies like Ethernet, Wi-Fi, and ARP.
While the TCP/IP model doesn’t capture every detail or nuance of how every network operates, it provides a robust, practical framework that has proven adaptable and vital as the foundation of the modern internet.