topology in computer network

What is Network Topology? 

 Topology defines the structure of the network in which all  components are connected to each other. There are two types of topologies: physical topology and logical topology. 

 Types of Network Topology 

 Physical topology is a geometric representation of all  nodes in a network. There are six types of network topologies: bus topology, ring topology, tree topology, star topology, network topology  and hybrid topology.

 1. Bus topology 

 .The bus topology is designed so that all  stations are connected via a single cable, the so-called main cable. 

 Each node is  connected to the core cable via a drop cable or directly  to the core cable. 

.When a node wants to send a message over the network, it inserts it into the network. All available stations on the network  receive the message, regardless of whether it was addressed or not. 

. The bus topology is primarily used in the 802.3 (Ethernet) and 802 standards.4 standard networks. 

 Configuring a bus topology is much simpler than other topologies. 

. The backbone cable is considered “single track”; with which the message is transmitted to all  stations. 

.The most popular method of accessing a bus topology is CSMA (Carrier Sense Multiple Access).

CSMA:  is a media access control used to control  data flow to maintain data integrity, i.e. H. Packages are not  lost. There are two alternative ways to solve problems that arise when two nodes send messages at the same time. 

 CSMA CD: CSMA CD (Collision Detection) is an access method for detecting collisions. As soon as a collision is detected, the transmitter stops data transmission. It therefore works according to the principle of “collision recovery”. 

 CSMA CA: CSMA CA (Collision Evidence) is an access method  to avoid collisions by checking whether the transmission medium is busy or not.If it is busy,  the sender waits until the medium becomes inactive. This technique effectively reduces the risk of  collision. This does not work with Collision Recovery. 

 Advantages of bus topology: 

 Cheaper cable: With bus topology, the nodes are connected directly  to the cable without going through a hub.The initial  installation effort is therefore low. 

Moderate Data Rate: Coaxial or twisted pair cables are primarily used in bus-based networks, supporting speeds of up to 10 Mbps. 

Familiar Technology: Bus topology is a familiar technology because the installation and troubleshooting techniques are well known and the hardware components are readily available.

 Limited error: An error on one node has no effect on other nodes. 

 Disadvantages of the bus topology: 

 Extensive cabling: The bus topology is quite simple, but still  requires a lot of cabling. 

 Difficult Troubleshooting: Special test equipment is required to detect cable failures. If a fault occurs in the cable,  communication between all nodes is interrupted.

Signal interference: When two nodes send messages at the same time, the signals of both  nodes interfere with each other. 

Difficult reconfiguration: Adding new devices to the network would slow down the network. 

Attenuation: Attenuation is the loss of signal that leads to communication problems.Repeaters are used to regenerate the signal.

2) Ring topology  

• Ring topology is like  bus topology, but has connected ends.

 •The node that receives a message from the previous computer forwards that message to the next node. 

•Data flows in one direction, meaning it is one-way. 

• Data flows in a single continuous loop called an endless loop.. It is terminalless, meaning each node is connected to another node and has no endpoint. 

• Data in a ring topology flows clockwise. 

•The most common access method in a ring topology is token passing. 

• Token Passing: This is a network access method in which a token is passed from one node to another. .Token: Is a frame circulating in the network.   Passing Token Operation   

• The token moves through the network and  is transmitted from one computer to another until it reaches its destination. 

• The sender modifies the token by placing the address along with the data. 

• Data is transmitted from one device to another  until the destination address matches. Once the target device receives the token, it sends a confirmation of receipt to the sender. 

•In  ring topology, tokens are used as owners.   Advantages of ring topology: 

Difficulty troubleshooting: Specialized testing equipment is required to identify cable errors. If a cable error occurs, it will disrupt  communication between all  nodes.

 Failure: Failure of one station leads to  failure of the entire network.  Difficult Reconfiguration: Adding new devices to the network will slow down the network.  

Delay: Communication delay is  proportional to the number of nodes. Adding new devices increases  communication latency.

3) Star Topology 

 Tar Topology 

Computer Network Topologies 

 • A star topology is a network arrangement  in which each node is connected to a central hub, switch, or  central computer. 

• The central computer is called a server, and the  devices connected to the server are called clients. 

• Coaxial cables or RJ-45 cables are used to connect  computers. 

 • hubs or switches are primarily used as interconnect devices in a physical star topology. 

• Star topology is the most popular topology in network implementations. 

 Advantages of Star Topology 

 Efficient Troubleshooting: Troubleshooting is quite efficient in a star topology  compared to a bus topology. In a bus topology, the manager needs to check the kilometers of the cables. With a star topology, all  stations are connected to a central network. Therefore, the network administrator must go to a single workstation to troubleshoot the problem. 

Network Control: Complex network control functions can be easily implemented in a star topology. Changes to the star topology are automatically taken into account. 

Limited outage: Since each station is connected to the central hub via its own cable, the failure of one cable has no impact on the entire network. 

Familiar Technology: Star topology is a familiar technology because its tools are convenient. 

Easy expansion: Can be easily expanded by adding new stations  to the hub's open ports. 

Economics: Star topology networks are cost-effective because they use inexpensive coaxial cables.

High data rate: Supports a bandwidth of approximately 100 Mbit/s. Ethernet 100BaseT is one of the most popular star topology networks. 

 Disadvantages of Star Topology 

  Central point of failure: If a central hub or switch fails, all  connected nodes cannot communicate with each other. 

 Cable: Sometimes cable management becomes difficult when extensive routing is required. 

 4) Tree topology 

 Computer network topologies 

 • The tree topology combines the properties of the bus topology and the star topology.

 • A tree topology is a type of structure in which all  computers are hierarchically connected to each other. The highest node in the tree topology is called the root node and all other nodes are  descendants of the root node. 

 • There is only one data transmission path  between two nodes. This creates a parent-child hierarchy. 

 Advantages of Tree Topology 

 Broadband Support: Tree topology is mainly used to provide broadband transmission, e.g.This means that signals are transmitted over long distances without attenuation.

Easy to expand: we can add new devices to the existing network. So we can say that the tree topology can be easily extended.

 Ease of Management: In tree topology, the entire network is divided into segments called star networks that can be easily managed and maintained. Error detection: Detecting and correcting errors is simple in a tree topology. 

 Limited error: An error at one station does not affect the entire network.

 Point to Point Wiring: It has point to point wiring for individual segments.

 Disadvantages of Tree Topology 

 Troubleshooting Difficulty: If any error occurs in the node then troubleshooting becomes difficult. 

 High cost: The equipment required for broadband transmission is very expensive.

 Error : The tree topology relies heavily on the main bus cable, and a main bus cable failure will bring down the entire network. 

 Difficult to reconfigure: If a new device is added, reconfiguration becomes difficult.

 5) Mesh Topology 

 • Mesh technology is a network arrangement in which computers are interconnected through various redundant connections. 

 • There are many paths from one computer to another. It does not contain a switch, hub, or any central computer serving as a central contact point. 

 • The Internet is an example of a mesh topology. 

• Mesh topology is mainly used for WAN deployments where communication errors are a serious problem. 

• The Mesh topology is mainly used for wireless networks. 

 • Mesh topology can be formed using the formula: Number of cables = (n*(n-1))/2;

 • Where n is the number of nodes representing the network. 

 Mesh topologies are divided into two types: 

 Fully connected mesh topologies Partially connected mesh topologies Fully

 connected mesh topologies: In a full mesh topology, each computer is connected to all available computers in the network.

 Partial mesh topology: In a partial mesh topology, all but a few computers are not connected to computers with which they regularly communicate. 

Advantages of Mesh Topology:

Reliable: Mesh topology networks are very reliable, as any disruption in the link will not affect the communication between machines connected computer.

Fast communication: Very fast communication between nodes. 

 Easier reconfiguration: Adding a new device will not interrupt communication between other devices. 

 Disadvantages of Mesh Topology Cost: Mesh topology contains a larger number of connected devices such as routers and more transmission media than other topologies.

Management: Mesh topology networks are very large and very difficult to maintain and manage.If the network is not carefully monitored, communication link errors will go undetected. 

 Efficiency: In this topology, redundant connections are high, reducing network efficiency.  

6) Hybrid topology

The combination of different topologies is called hybrid topology. Hybrid topology is the connection between different links and nodes to transmit data. When two or more different topologies are combined, it is called hybrid topology and if similar topologies are connected together then no hybrid topology will be created. For example, if there is a ring topology in one branch of ICICI bank and a bus topology in another branch of ICICI bank, connecting these two topologies will create a hybrid.

 Advantages of Hybrid Topology Reliable: 

If a failure occurs in one part of the network, it will not affect the operation of the rest of the network. 

Scalable: Network size can be easily expanded by adding new devices without affecting the functionality of the existing network. 

 Flexible: This topology is flexible as it can be designed according to the organization's requirements. 

 Efficiency: Hybrid topology is very efficient because it can be designed in a way that maximizes the network's strength and minimizes its weaknesses.

 Disadvantages of Hybrid Topology Complex Design : 

The main disadvantage of hybrid topology is the hybrid network design. It is difficult to design hybrid network architecture.

Expensive Hub : Hubs used in hybrid topologies are expensive because these hubs are different from conventional hubs used in other topologies. 

 Expensive Infrastructure: Infrastructure costs are very high because hybrid networks require a lot of cabling, network equipment, etc.