A network or sometimes called nodes is a set of devices connected through some communication links. These nodes can be a computer, printer, or any devices which are capable of transmitting signals at one node and received them at other nodes on the network. Computer networks are used to communicate data between two devices. When two devices communicate with each other through sending and receiving data between them is called data flow. Data flow can be in different ways in these devices as follows:
- Half Duplex
- Full Duplex
In Simplex mode, two or more devices communicate in one direction or one-way or the communication in this mode is unidirectional.
In this mode, only one device transmits the data, and the others receive this data.
Example of Simplex
Keyboards and traditional monitors are the best examples of Simplex mode. A keyboard is used to enter the data as input while the monitors are used to receive the output. This transmission of data is unidirectional or in one way only.
In Half-Duplex mode, both devices can transmit and accept the data signals but not at the same time. In simple words, we can say that when a device sends data, other device receives it and vice-versa. This mode of data flow is used in cases where no need for data communication in both directions same time and the entire channel capacity can be utilized for each direction.
The Half-Duplex mode of data flow is just like a one-way road where only the traffic is allowed only one direction at a time while others have to wait to clear it.
Examples of Half-Duplex
CB (citizens band) radios and walkie-talkies, etc.
The Full-Duplex mode is also called Duplex mode in which both devices can transmit and receive the data simultaneously. Unlike the Half-Duplex mode, in Full-Duplex mode, the data or signals transmitting in one direction can utilize the entire capacity of the link with data flowing in another direction. The entire channel capacity must be shared between these two devices at the same time.
This mode of data flow is like a two-way road where the vehicles are allowed to go in both directions at the same time.
Example of Full-Duplex/Duplex
Mobile phones are the best common example of Full-Duplex mode where both persons are allowed to talk at the same time over telephone lines.
Read also: What is a Wireless or Wi-Fi network?
What is a Computer Network?
A network or sometimes called nodes is a set of devices connected through some communication links. These nodes can be a computer, printer, or any devices which are capable of transmitting signals at one node and received them at other nodes on the network. Computer networks are used to communicate data between two devices.
In distributed processing, a task is divided among multiple systems or nodes. In this, a subset is handled by the personal computer, instead of a single large machine that is responsible for all types of process in communication.
A computer network should ensure a certain number of criteria like performance, reliability, and security.
The performance of any computer network is based on transit time as well as response time. Performance is calculated by two metrics called throughput and delay. For better performance of any system, we need more throughout and smaller delay time in communication. To send more data over any network, we have to increase throughput and for traffic congestion, we have to increase the delay time of the network.
- The performance of any network depends on some factors as follows:
- Number of users
- Transmission medium
- Hardware and software used in the network.
- Reliability is an attribute of any network which is measured by a few parameters such as:
- Frequency of failure
- Recovery time of a link/network after a failure
- Network robustness in a catastrophe
- Security of any network includes the prevention of data from viruses and unauthorized access over the network. Further, we need to implement some policies and procedures to recover lost data from data breaches as well as prevent the data from damage and development.
Physical Structures or Network attributes:
There are some network attributes discussed to understand the networks in a better manner.
Types of connections:-
A connection is the type of any physical or virtual link that is required to connect two or more devices together. This link is a communication pathway that is used to transfer data from one device to another at the same time.
For better understanding, we can imagine it mathematically through a line drawn from point A to another point B. This line is carrying data from A to B and B to A at the same time.
There are two important types of connections are as follows:
- Point-to-Point connection
- Multipoint connection
To establish a dedicated link between two or more devices, a point-to-point connection is used and this link reserves its entire capacity for successful transmission between them. In this type of connection, a wire or cable is used to connect both ends. However, microwave or satellite links also available for such connections.
Television remote is used to change TV channels by infrared rays and this remote establishes a point-to-point connection between remote and television.
Multipoint connections are used when more than two devices share a common link between them. It is also called a Multi-drop connection. In these types of connections, the entire capacity of the link is shared spatially or temporally between available devices. If there are lots of devices that are sharing the link together, it called a spatially shared connection.
Must Read: Classification of Computer Network
Physical Topology is defined as a method to disburse the network physically or logically. A link is used to connect two or more devices, further two or more than two links are connected through the Topology. Hence, the Physical Topology represents the relationship between the link and devices (nodes) to one another.
Types of Topology
There are five basic types of Topologies are possible and these are as follows:
- Mesh Topology
- Bus Topology
- Star Topology
- Ring Topology
- Tree Topology
- In Mesh Topology, each device establishes a dedicated point-to-point connection with other devices. Dedicated means the link is carrying data between two devices that are connected together.
- In a Mesh Topology system, a host is connected through single or multiple hosts simultaneously having a dedicated point-to-point connection with one another. These hosts also act as a relay for others who don’t have dedicated point-to-point links.
Example of Mesh Topology
In the Telecom industry, each regional office must be connected to every other regional office. This connection is called Mesh Topology.
Types of Mesh Topology:
Mesh Topology has two types and these are as follows-
- Full Mesh- It provides the most reliable network structure in all available topologies, in which all hosts establish a dedicated point-to-point connection with all other hosts.
In Full Mesh Topology, every new host requires n(n-1)/2 connections.
- Partial Mesh- Unlike full Mesh, it does not require a dedicated point-to-point connection between the hosts. In this topology, hosts are connected in specific arbitrarily design to each other host. This topology provides reliability for some particular hosts, not for all.
How to find a number of connections or physical links in Mesh Topology?
To find the number of connections or physical links in a Mesh Topology system, we have to assume that each node must be connected to every other node. If there are n numbers of nodes are available in the system.
- Suppose, node 1 is connected to other nodes,
Then total number of connections= (n-1)
- Similarly, node 2 is connected to all other nodes,
Then total number of connections= (n-1)
Similarly, node n is connected to all other nodes and having (n-1) connections.
Now mathematically, we need n(n-1) physical links. However in Duplex mode, communication allows in both directions, hence we will divide the number of links by 2.
Total Number of links/connection required= n(n-1)/2
Advantages of Mesh Topology
- It is used to eliminate the traffic problems while carrying data from one node to other as it uses dedicated links that are responsible for carrying their own data load by all networks.
- It is robust which means while one link gets inactive, it does not affect the entire system.
- It provides a more secure connection in comparison to other topologies.
- Fault identification and fault isolation is easy in this topology.
Disadvantages of Mesh Topology
In Mesh topology, every device needs a connection with every other device so, It requires more cabling as well as the number of Input and Output (I/O) ports.
Installation and reconnection are difficult in the Mesh topology system.