Network Topology

 

What is Network Topology ?

A computer network is a collection of two or more computers which are connected together to share information and resources.

Types of Topology:-

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1. Based on Geographical Area Network
2. Based on Architecture

Based on Geographical Area Network:-

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1. Local Area Network (LAN)
2. Metropolitan Area Network (MAN)
3. Wide Area Network (WAN)

Based on Architecture:-

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1. Point to Point Topology
2. BUS Topology
3. Ring Topology
4. Star Topology
5. Mesh Topology
6. Tree Topology
7. Hybrid Topology

LAN topology has 2 types:-

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1. Physical Topology:- Represent your network's physical devices & cables.
2. Logical Topology:- Show how data behaves between network devices.

Point-to-Point Topology:-

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1. Point-to-Point networks have exactly 2 hosts, where the receiving end of one host connects directly to the sending end of the other host.
2. This is usually done with the help of a single, long cable that connects the two hosts (the hosts may be routers, servers, PCs etc.).

Advantages of point to point topology:

1. Very high bandwidth and speed because of only 2 end devices sharing the link.
2. Low latency connection.
3. Replacement of nodes is easy, as there are only 2 of them.
4. Easy to set up and maintain.

Disadvantages of point to point topology:

1. Not feasible for nodes spread out over large distances.
2. In case of damage to the common link, the whole network will go down.
3. If any of the 2 nodes stops working, it interrupts data transfer across the network.

BUS Topology:-

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1. In this topology, all the devices share a common communication channel, and there may be multiple devices connected across this common link.
2. A bus topology is a multipoint communication. In this topology one single and long cable_(Act as a back bone) used to leave all other devices in the network.
3. Nodes are connected to the bus cable by droplines and taps. A dropline is a connection between the device and the main cable.
4. A tap is a connector used to contact with the metalic core of the main cable and droplines.

Advantages of Bus Topology:

1. In case any node fails, it does not affect the operation of the network.
2. It is easy to connect/disconnect devices from the network without interrupting the operation of the network.
3. Expanding the network just requires joining more lengths of cable together.
4. Bus topology is a well-known technology since the installation and troubleshooting procedures are widely understood, and hardware components are readily available.

Disadvantages of Bus Topology:

1. If the common link fails, the whole network fails.
2. Too many devices may cause the network to slow down.
3. It is difficult to find the exact fault when something fails.
4. Only one device can transmit at a time.
5. Signals will bounce back if terminators are not configured correctly.
6. Signal interference occurs when two nodes send messages at the same time, causing their signals to collide.
7. The speed of bus topology is slow when heavy traffic created.

Ring Topology:-

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1. Each host machine in a ring topology links to exactly two other machines, forming a circular network structure. When a host tries to communicate with or send a message to a host that isn’t directly adjacent to it, the data is routed through all the hosts in between.
2. The communication in a ring topology may be unidirectional or bidirectional.
3. Token passing is the most popular ring topology access mechanism. A token is a frame that circulates throughout the network. Token passing is a network access mechanism that involves passing a token from one node to another.

 

 

Advantages of Ring Topology:

1. The advantage of a ring topology is that each computer serves as a repeater, re-generating the signal and forwarding it to the next computer, maintaining signal strength.
2. ThickNet coaxial cables or fiber optic cables were used for this purpose.
3. The signals are transmitted in the loop in one direction and forwarded via each computer. Each computer serves as a repeater to amplify the signal and send it to the next computer. 
4. It is more suitable for high traffic environments than bus networks. It also mitigates the effects of noise in the ring topology.

Disadvantages of Ring Topology:

1. The disadvantage of a ring topology is that only one computer at a time can send data in a single token ring. In addition, ring topologies are usually more expensive than bus technologies. 
2. If one cable has a fault, the whole ring is interrupted, which means an interruption in the network.
3. Data must pass through multiple devices, which may be a security concern.
4. In order to reconfigure, add, or delete nodes, we must take the entire network offline.
5. Because all network devices share bandwidth in a ring architecture, the addition of new devices can contribute to increased communication latency.

Star Topology:-

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1. In a star topology, cable segments from each computer in the network are connected to a central component, the so-called hub/switch.
2. A hub/switch is a device that connects multiple computers. In a star topology, the signals are transmitted from the computer via the hub/switch to all computers in the network. 

Advantages of Star Topology:

1. High speed data transfer
2. Easy to add more devices, just a single cable is required.
3. Network management is easy due to the presence of the hub device.
4. Easy to add/remove devices without affecting operation of the network.
5. Easy to locate problems in the network.

Disadvantages of Star Topology:

1. If the hub fails, the entire network fails.
2. Requires more wires compared to bus and ring topologies.
3. The overall bandwidth and performance of the network are also restricted by the settings and technical specifications of the central node, making star topologies costly to set up and operate.

Mesh Topology:-

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1. In a meshed topology, each computer is connected to each other by a separate cable. This configuration provides redundant paths in the network, so if one cable fails, another cable takes over the traffic and the network continues to function smoothly. 
2. Leased telephone lines, ThickNet coaxial cables or fiber optic cables were used for this purpose. 
3. 
   

There are 2 types of mesh topologies:

1. Full mesh:  
2. Partial/Half Mesh:

Full mesh: All hosts are connected to all other hosts in the network using a point-to-point connection.

Partial/Half Mesh: Not all hosts are connected to other hosts with a point-to-point connection, the connections are made purely based on the network requirements.

  

Advantages of Mesh Topology:

1. Reduction in congestion as there are special point-to-point links between devices.
2. Provides multiple routes for data transfer
3. Easier to identify faults due to the presence of point-to-point links.
4. Provides a high level of privacy and security. 
5. One advantage of the machine topology is its backup capability, as several paths are provided in the network. Since redundant paths require more cables than other topologies, a machine topology can be expensive.

Disadvantages of Mesh Topology:

1. Requires a lot of cables and data transfer ports to set up.
2. More expensive as compared to bus, star, ring etc.
3. Difficult to install due to the presence of a large number of links.
4. The number of redundant connections in this architecture is significant, reducing network efficiency.
5. Mesh topology networks are massive and challenging to maintain. If the network is not closely monitored, a communication connection breakdown will go undetected.

Tree Topology:-

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1. Most commonly occurring form of network topology, which uses the properties of both star and bus topology. Tree topology is organized into different levels, namely:

1. Access Layer: Lowest layer, involves computers.
2. Distribution Layer: Middle layers, joins and coordinates the upper and lower layers.
3. Core Layer: Highest layer, also the central part of the network.

Advantages of Tree Topology:

1. Easy to scale, as more computers can be added easily into the access layer.
2. In case of damage to a node, it does not affect other nodes in the network.
3. Easy to identify faults and maintain the network.
4. Easy to set up, because point-to-point links are used for individual segments.

Disadvantages of Tree Topology:

1. Tree topologies are costly due to the massive quantity of cable required to link each item inside the hierarchical architecture.
2. If the core layer fails, the entire network fails.
3. Because of the network’s hierarchical complexity and linear structure, adding additional nodes to a tree topology may soon become an unmanageable, not to mention costly, experience.

Hybrid Topology:-

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1. With a hybrid topology, two or more topologies are combined in a network design. Networks are rarely designed with a single topology type. For example, you can combine a star topology and a bus topology to take advantage of both topologies.

Advantages of Hybrid Topology:

1. Combines the good qualities of various topologies.
2. Very scalable and reliable
3. Easy to change as per the requirement of the network.
4. Hybrid topology is extremely successful because we can customise it so that we increase or amplify the strengths and make the weaknesses less prominent.

Disadvantages of Hybrid Topology:

1. Expensive due to the larger number of cables and ports required.
2. The design of the Hybrid network is the main disadvantage of the Hybrid architecture. The architecture of the Hybrid network is extremely complex to build.
3. The Hubs used in the Hybrid topology are highly costly since they are not like the Hubs used in other topologies