Introduction
For those just beginning their networking career, you may have heard the term “TCP/IP model” thrown around. If you haven’t heard of it before, it may be somewhat confusing. However, the TCP/IP model is essential to computer networking and is critical to learn.
War of the Networks
In 1969, the DoD invented the first computer “network” known as ARPANET. ARPANET was a massive leap forward in the development of computers because it allowed for communication between two or more machines, which was previously unheard of. However, the network protocols for ARPANET were proprietary, as were the subsequent networks companies built on top of it.
Companies like IBM developed closed-source computer networks, which only worked with that manufacturer’s equipment, i.e., IBM computers could only talk to IBM computers. This severely limited the capabilities of computer networking. However, in the 1970s two DARPA scientists (Vint Cerf and Bob Kahn) developed the TCP/IP protocol. From there the TCP/IP protocol rapidly gained traction. With the creation and standardization of the TCP/IP protocol, the foundations for the internet were set.
How does the TCP/IP model work?
The TCP/IP model has 5 layers:
- Physical
- Data Link
- Network
- Transport
- Application
A graphical representation of the TCP/IP model is shown below:
Layer 1 – Physical
Layer 1 of the TCP/IP model is the physical layer. The physical layer consists of the physical hardware, ports, and cables necessary to transmit information over the network, i.e., Ethernet cables, fiber optic cables, Network Interface Cards (NICs), and hubs. The physical layer allows computers to be connected and share information.
Layer 2 – Data Link
The data link layer is the layer that packages the information sent from the layers above it into a format known as a frame. The frame acts as a wrapper for the data itself, allowing the receiving machine to know what data and how much of that data is going to be sent to it. By doing this, the TCP/IP model implements efficient communication between devices and minimizes the risk of data loss.
Layer 3 – Network
Layer 3 of the TCP/IP model is the network layer. The network layer is the layer of the TCP/IP model that handles the functions that allow the actual communication across networks. The network layer uses IP addresses to identify machines, whereas the data link layer uses MAC addresses to identify machines. A network router functions at layer 3 since it routes IP addresses, whereas a network switch functions at layer 2 since it routes MAC addresses.
Layer 4 – Transport
The transport layer contains the UDP and TCP protocols and ensures that all data arrives at the receiving machine in sequence with no data loss. The TCP protocol is a connection-oriented protocol that prioritizes reliability over speed, whereas the UDP protocol is connectionless and prioritizes speed over reliability. More information can be found in the resources section.
Layer 5 – Application
The application layer is responsible for all of the protocols that deliver data to the user. The application layer consists of protocols such as DNS, HTTP, and FTP. The application layer in the TCP model combines the application, session, and presentation layers of the OSI model.
Conclusion
In summary, the TCP/IP protocol is the backbone of the internet. It provided a critical solution to the inter-compatibility problem of the early internet and spearheaded the burgeoning growth of the future internet.
Resources
