A Complete Overview of Data Link Layer and Network Layer of TCP/IP Model

Have you ever imagined how data packets get transferred from one end of the internet to the other? How important data should be displayed on your monitor or smartphone or tablet? This is all possible because of the transmission control protocol/internet protocol or TCP/IP model. Today, modern computing and telecommunication heavily rely on the TCP/IP model as it defines how the data is sent and received through network communication hardware, including network switches, adapters, routers, and many more. From email to your web browsers to the system that runs several applications and connects them to the internet, everything is based on the core concepts of the TCP/IP model. The functionality of the TCP/IP model is divided into four layers – physical layer, data link layer, network layer, and transport layer. Each layer is defined as a specific function to perform. This post highlights the data link layer and network layer in detail.

A Brief Introduction on Data Link Layer

The data link layer is a second layer or layer 2 of the TCP/IP network model. This layer is one of the most complicated layers that have complex functionalities and liabilities. The data link layer is responsible for converting the data stream from the network layer (layer 3) into frames that are sent over the L2 network switches. This layer uses a Media Access Controller or MAC to generate the frames that will be transmitted over the network. While transmitting data, the layer adds a header containing information like source and destination MAC addresses to the data packet received from the network layer. According to the functionality, the data link layer is again divided into two sub-layers:

1. Media Access Control (MAC): The sub-layer provides an interface with the network adapter and controls access to the network medium.
2. Logical Link Control (LLC): The layer is responsible for managing links between communication devices and error-checking functions for frames.

The data link layer does many tasks, including framing, addressing, synchronization, error control, flow control, multi-access, and more. But, one important function of computer networking is LAN Switching that is associated with the data link layer. In LAN switching, the data packet from one system is transferred to another system in the local area network (LAN). In LAN, several computers are connected by a network infrastructure device called network switches. For instance, if system A wants to send data to system B, then A will place the data as bit-stream over the network media. Now, the L2 network switch will receive the bit-stream and deliver the data to the intended recipient. In simple words, the network switch that operates at layer 2 will open the data link layer frame header and trailer and deliver the frame to the exact recipient system.

A Quick Overview of Network Layer

The network layer is layer 3 of the TCP/IP model, from the bottom. The important protocols included in the network layer are internet protocol (IPv4 or IPv6), address resolution protocol (ARP), internet control message protocol (ICMP), and more. This layer is responsible for encapsulating the data packets generated by the transport layer protocols.

Another important function of computer networking is routing, which is associated with the network layer. In routing, IP datagrams from the system that exists on one network are forwarded to another system on a remote network. Basically, routing is done by network routers. For instance, system A of one LAN wants to send data to system B of another LAN, then A will place the data as bit-stream over the network media. Here is how the data path flow will be:

• System A to network switch of LAN 1
• The network switch of LAN 1 to the router of LAN 1
• Router of LAN 1 to the router of LAN 2 through internet cloud
• The router of LAN 2 to network switch of LAN 2
• The network switch of LAN 2 to computer B

In simple words, routers operate at layer three open the network layer header, and use the address information in the IP datagram header to deliver it to the router of the destination LAN.

The information provided in this post will help you better understand the layers of the TCP/IP model in detail. You may also understand the importance of network switches to connect and transfer data to specific devices. Would you like to expand your existing network using these networking switches? If yes, then you must source them from a reliable industry supplier like VERSITRON. With years of industry experience, the company offers reliable network devices and solutions with their main focus on fiber optics.

R.W. Tull is the President of VERSITRON. He interfaces daily with current and potential end-users. R.W. works closely with clients to review layout diagrams and drawings in order to ensure that the best fiber optic solution is achieved.