Network topology types
In this post, we share knowledge of Networking topology types. Networking concepts at the end of this post you will be able to
define network topology,
Identify different types of topology
describe the open system interconnection (OSI) model and its layers.
Network topology refers to the arrangement of the different elements(links and nodes) of a network. It is the layout of a network and may be depicted as:
- Physical topology: It is the arrangement of the various network components.
- Logical topology: It describes how data flows in a network.
Distances between the nodes, physical connections, rate of transmission of types of the signal may differ between two networks, but still, topologies may be identical.
Network topology types
Types of topology
There are five types of network topologies based on the type of exchange of information through the network. They are as discussed:
In a bus topology, each node is connected to a single cable using interface connectors. The central cable, known as a bus , is the backbone of the network. The packets that are transmitted in both directions along the bus contain the destination address. As a single high capacity cable is required, this topology needs minimum cabling and the cost is also low. The entire cable setup needs to be reconfigured to add a node. It is a time-consuming process to troubleshoot as every point needs to be checked to locate the fault.
The following figure shows bus topology where all nodes are connected to the same terminal:
The star topology links the nodes over a network, utilizing a central control unit which is known as a hub . Nodes in a star-based network can be easily attached to the hub. All the nodes are connected to the hub, thus, requiring a lot of cabling and high cost. A faulty hub can disrupt the entire network.
The following figure shows the star topology:
The ring topology links the nodes through a point-to-point connection over a network. It is easy to locate cable faults in a ring and if any nodes in the network malfunctions, the entire network stops functioning.
The nodes in the network make a closed loop. The flow of data is unidirectional around the ring. The data is passed through the nodes from the sender to the receiver.
The following figure shows the closed-loop connection in ring topology :
The mesh topology involves a point-to-point connection between every node in the network. It is highly reliable as network connectivity does not depend on anyone node. It is used for large network connections. It involves high installation and setup costs due to the complex cabling required to connect each node with the other. This topology becomes difficult to manage if the size of the network increases.
The following figure shows the architecture of mesh topology:
The cellular topology is a wireless topology, where a geographic area is divided into cells or regions. Each cell is a separate entity that is controlled by a central station. This topology operates on wireless media which does not require cabling.
It is easy to install as the only requirement is the availability of a central location and signal strength. Data transmission happens in a cellular digital packet data (CDPD) format.
The following figure shows a cellular topology connection:
The OSI model is a conceptual or networking framework designed to implement a set of rules, known as protocols, for the transfer of information between different layers. It was designed by the International Organisation for Standardization(ISO).
The model divides network communications into seven layers:
- Physical layer
- Datalink layer
- network layer
- Transport layer
- Session layer
- Presentation layer
- Application layer
The following figure describes the seven layers of an OSI model:
Every layer protocol performs specific services which is unique for that layer. The protocol interacts with the protocols which are directly above and below it, while performing the services.
The description of the seven layers on the basis of their functions are as follows:
It is the first layer of the OSI model. This layer protocol transmits bits rather than packets in the form of a physical signal over the connecting network. It interfaces with the data link layer and performs coding, decoding and transmission of information in the form of bits.
It passes the information bit by bit and detects and accepts signals which are passed to the data link layer. It monitors error rates in data but cannot perform error corrections.
The following figure shows the flow of data from the data link layer to the physical layer and vice-versa:
It is the second layer of the OSI model which transmits information in the form of packets. These packets contain the source and the destination address which are required to transmit them to their assigned destination. It also performs error checking, which is not done by the physical layer
- It provides an interface to the network layer
- It deals with transmission error to ensure that the frame arrives without any problem
- It controls the flow of data
The following figure shows the flow of data from the network layer to the data link layer:
It is the third layer of the OSI model. It transmits data packets in a logical way and it assigns network addresses to these packets which is translated into their equivalent physical addresses. There are two types of address assigned to each node:
- Network address
- Physical address
In this protocol layer, each packet is assigned a network address which works on a hierarchical addressing design. It accepts the data segments, which are known as packets, from the transport layer. The header part of these packets are added with the logical addressing information before being sent back to the transport layer.
The following image shows the flow of data in packets from the transport layer to the network layer:
The fourth layer in the OSI model is the transport layer. On the basis of its application, this layer can be either connection-oriented or connectionless.
It accepts data from the layer above it(session layer) and performs end to end delivery of the data. It ensures that the data is transferred from the sender to the receiver without any error and is understandable by the receiver.
This layer of protocol forms data packets and it assigns the sender’s and receiver’s addresses to the header part of the packets. This is known as the multiplexing of data.
The following image shows the flows of data in segments from the session layer to the transport layer:
It is the fifth layer of the OSI model. This layer performs different functions between two nodes in the network:
- Coordinates and maintains communication between nodes
- Establishes and maintains a secure communication link between the nodes
The following image shows the flow of data from the presentation layer to the session layer:
It is the sixth layer. Its function is to accept data from the layer above it (application layer )and format the information.
It acts as a translator and performs the function of compressing and encoding the information received from the above layer. This layer performs various functions such as :
- Data encryption
- Data compression
- Data conversion
The following images show the flow of data from the application layer to the presentation layer:
It is the top layer of the OSI model. It deals with the user end applications such as e-mail, transfer of files, dealing with software and web browsing.
Unlike other layers, it does not serve but can interact with the layer below it to transfer its data to the host.
The following image shows the connection of the user and presentation layer with the application layer: