We gave you a taste of Networking Protocols in our previous tutorial. There are several of these protocols, and we’ll introduce them gradually, though not necessarily in a strict chronological order. We will frequently return to previous topics, expanding on previous information with new information. We will also go forward at times, employing mechanisms that will only be explained in greater detail over time. It may appear overwhelming at first, but with time, everything should start to blend into one coherent picture.
This and the subsequent tutorial will go over a protocol known as “Address Resolution Protocol (ARP)”. This protocol is used to resolve addresses, as the name implies.
Introduction to Address Resolution Protocol (ARP)
Address Resolution Protocol(ARP) is a protocol or procedure in a local-area network(LAN) that maps an ever-changing Internet Protocol(IP) address to a fixed physical machine address, also known as a media access control (MAC) address.
Because the lengths of the IP Address and MAC Address differ, this mapping procedure is essential. An IP Address is made up of 32 bits. MAC addresses, on the other hand, are 48 bits long. ARP translates a 32-bit address to a 48-bit address and vice versa.
So, who is responsible for this mapping? Is it a hub, a switch, or a router? Follow along to find out the answer.
The Open Systems Interconnection (OSI) model and its layers
The Open Systems Interconnection(OSI) model is a networking model. It was developed in the late 1970s. The OSI model uses layers to provide IT teams with a visual representation of what is happening with a specific networking system. This can be useful in determining which layer affects which network application, device, or software. Furthermore, it determines which IT or engineering professional is in charge of managing that layer. Its goal is to guide vendors and developers so that their digital communication products and software programs can interoperate, as well as to provide a clear framework describing the functions of a network or telecommunications system. OSI architecture has been officially adopted as an international standard by the International Organization for Standardization(ISO).
The main idea behind OSI is that the communication process between two endpoints in a network can be divided into seven distinct groups of associated functions or layers. The OSI model consists of seven layers. To function properly according to the OSI model, each end device must implement these seven layers.
In this architecture, each layer serves the layer above it, and the layer beneath it is served in turn. In a given message between users, data will flow through the layers of the source computer, across the network, and through the layers of the receiving computer.
Suppliers created proprietary model networking to support their own products in the early days of computer networking. The main issue with these models was that only devices manufactured by the same vendor could communicate with one another. For example, only the computer or networking device produced by IBM could communicate.
This situation was neither good nor profitable for both manufacturers and consumers. It compelled not only producers to manufacture all essential network devices but also consumers to buy all devices from the same manufacturer.
To overcome this barrier, leading hardware manufacturers have agreed that a vendor-neutral network model should be used or supported alongside their proprietary networking model. Two significant efforts were made to develop a supplier-neutral networking model.
The first was created by ISO, and the second by the Department of Defense. ISO (The International Organization for Standardization) established the OSI (Open Systems Interconnection) model, and the US Defense Department (DoD) developed the TCP / IP model.
The OSI model assists computer network users and operators by providing:
- Determine the hardware and software required to build their network.
- Understand and communicate the process that components use when communicating across a network.
- Troubleshoot by determining which network layer is causing an issue and concentrating efforts on that layer.
The OSI model assists network device manufacturers and networking software vendors in the following ways:
- Create devices and software that can communicate with any other vendor’s products, allowing for open interoperability.
- Define which parts of the network their products should work with.
- Inform users about the network layers at which their product operates, such as only at the application layer or across the stack.
Q: I heard that the modern Internet is not based on the OSI model, but rather on the simpler TCP/IP model.
Differences between OSI and TCP/IP models
The modern Internet is based on the simpler TCP/IP model rather than the more complex OSI model. The OSI 7-layer model, on the other hand, is still widely used because it helps visualize and communicate how networks work, as well as isolate and troubleshoot networking problems.
This tutorial does not go into detail about the TCP/IP model. It will be covered in a later tutorial. For the time being, keep in mind that the internet we use is reliant on Internet Protocol Suits. So we’ll go over the TCP/IP model a little bit.
The Transfer Control Protocol/Internet Protocol (TCP/IP) model predates the OSI model and was developed by the United States Department of Defense (DoD). TCP/IP is the simpler of the two models, combining several OSI layers into a single one:
- TCP/IP combines OSI layers 5, 6, and 7 into a single Application Layer.
- TCP/IP combines OSI layers 1 and 2 into a single Network Access Layer. However, TCP/IP does not handle sequencing or acknowledgment functions, these are handled by the underlying transport layer.
Other important differences:
- TCP/IP is a functional model that is based on specific, standard protocols and is designed to solve specific communication problems. OSI is a generic, protocol-agnostic model designed to describe all types of network communication.
- Most TCP/IP applications use all the layers, whereas simple OSI applications do not use all seven layers. Only layers 1, 2, and 3 are required for data communication.
The TCP IP model’s functionality is divided into four layers, each with its own set of protocols.
TCP/IP is a layered server architecture system, with each layer defined by the function to be performed. All four TCP IP layers work together to transfer data from one layer to the next.
Now that you’ve completely forgotten about the Address Resolution Protocol (ARP), let’s get started. We will explain ARP using the OSI model.
The data link layer, also known as the MAC address, establishes and terminates a connection between two physically connected devices so that data transfer can occur. The IP address is also known as the network layer or the layer in charge of routing data packets through various routers. ARP communicates between these layers.
ARP is used by a network device to send data through a switch on a TCP/IP network. Remember switch knows MAC Address and Router knows IP Address. Using the IP address, the device must determine the MAC address. It accomplishes this through the use of ARP. The IP address and the Address Resolution Protocol(ARP) are used to retrieve the MAC address.
ARP operates between the Open Systems Interconnection(OSI) model’s Layers 2 and 3. Layer 2 of the OSI model, the data link layer, contains the MAC address. The IP address exists on the network layer, Layer 3.
