Hello, everyone!
Today, I continue to explain network communication. Now, I will start to explain the layers of the TCP/IP model. In this article, I will explain the physical and data link layers.
The physical level is the lowest level or level 1 of the TCP/IP model or ISO/OSI referent model. It defines the electrical and physical characteristics of the transmission medium and the relationship between the device and the transmission medium. The physical layer defines voltage, data rate, connection method, maximum distance, etc. Here we are mainly talking about different types of cables (optical cables, UTP cables, etc.) and connectors (SC, LC, E2000, RJ45, etc.). It is done at the bit level - 0 and 1.
The data link layer is the second layer of the TCP/IP model or ISO/OSI referent model. This is the first logical layer. Its function is to physically address the terminals to allow communication between them. There are also fields that define the IP and IPX protocols so that the device knows how the data will be transmitted further. This layer consists of two sub-layers, which are:
LLC (Logic Link Control) sub-layer. It is located between the network layer and the MAC sub-layer. This sub-layer identifies the protocol and encapsulates the data to be transmitted. Most data link layer functions perform this sub-layer, and
MAC (Media Access Control) sub-layer. This sub-layer defines how data is transmitted and communicates with the physical layer. MAC defines device addressing, network topology, line specification, traffic flow control, etc. Every device on the network has a physical address - a MAC address. It consists of 48 bits and is globally unique. MAC addresses are most often represented by hexadecimal digits. Some network devices that have two or more NICs (Network Interface Card) have two or more MAC addresses because each NIC has its own MAC address.
There are several protocols that are defined. IEEE 802.2 LLC is a protocol used for LAN. For WAN, the following protocols are PPP (Point-to-Point Protocol), HDLC (High-level Data Link Control), FR (Frame Relay), etc. About all this in detail in the following articles.
This is the end of this article. In the next article, I will continue to write about this topic >> Network communication basics (4).
Thank you!
