What is Network Topology?
Network Topology refers to the structure of the topology of a network. A network topology could consist of several types of routers with many connections to other routers. In a network, routers are able to route information from one router to another over their connections.
Topologies can be physical or logical. Physical Topology means the physical design of a network, including the devices, location and cable installation. Logical Topology refers to how data transfers in a network as opposed to its design. Some of the most common network topologies are:
- Bus Topology
- Ring Topology
- Star Topology
- Mesh Topology
- Tree Topology
Bus topology is a computer networking concept that provides a computer with a direct connection to several other computers in a network. The computer that is providing the connection between those other computers is referred to as the bus topology switch. There are several different ways to implement bus topology connections, the best of which is to use a computer that has four, or eight, or sixteen sockets.
This structure is prevalent for local area networks. In this structure or topology, a single network cable runs in the building or campus, and all nodes are linked along with this communication line with two endpoints called the bus or backbone, as the shown figure:
By this type of topology, if one node goes faulty, all nodes may be affected as all nodes share the same cable for sending and receiving information. The cabling cost of bus systems is the least of all the different topologies. Each end of the cable is terminated using a special terminator.
Advantages of Bus Topology
- Reliable in very small networks as well as easy to use and understand.
- Requires the least amount of cable to connect the computers (nodes) together and therefore is less expensive than other cabling arrangements.
- It’s easy to extend, Two cables can be easily joined with a connector, making a longer cable for more computers to join the network.
- A repeater can also be used to extend a bus configuration.
Disadvantages of Bus Topology
- In a busy network with a lot of traffic, a server or switch port may experience high CPU loads, leading to increased load and lower processing performance.
- Each connection between two cables weakens the electrical signal.
- The bus configuration can be difficult to find and can cause the whole networks to stop functioning.
Ring topology is a common type of topology used for Ethernet networks. It consists of a single link that is routed around the network in a cycle (ring). The ring is formed with other nodes with which it forms an interconnect or ring. Ring topologies are sometimes referred to as daisy chains due to the shape of the network.
A typical ring topology will have two or more devices connected in a chain. In the two-node case, the devices are connected directly to each other. If more than two devices are connected, a single physical link will be connected in a loop between each pair of devices, as shown in the figure on the right.
There is a direct point-to-point link between two neighbouring nodes (the Next and the Previous). These links are unidirectional, which ensures that transmission by a node traverses the whole ring and comes back to the node, which made the transmission as shown in the figure.
Information is sent from one node to the next as it moves around the ring. To ensure that each packet of data transmitted to the rink arrives at its destination, it is prefixed with the station’s address to which it is being sent.
In response to the arrival of a packet of data, the node first checks to see if the packet’s address is the same as its own; if it is, it then collects the data contained inside the packet.
If the packet does not belong to it, it sends it to the next node in the ring. Faulty nodes can be isolated from the ring. When the workstation is powered on, it connects itself to the ring.
When power is off, it disconnects itself from the ring and allows the information to bypass the node. The most common implementation of this topology is a token ring. A break in the ring causes the entire network to fail. Individual nodes can be isolated from the ring.
Advantages of Ring Topology
- Ring networks offer high performance for a small number of workstations or for larger networks where each station has a similar workload.
- Ring networks can span longer distances than other types of networks.
- Ring networks are easily extendable.
- Unlike Bus topology, there is no signal loss in Ring topology because the tokens are data packets that are re-generated at each node.
Disadvantages of Ring Topology
- Relatively expensive and difficult to install.
- Failure of one computer on the network can affect the whole network.
- It is difficult to find fault in a ring network.
- Adding or removing computers can disrupt the network.
- It is much slower than an Ethernet network under normal load.
Star topology uses a central hub through which all components are connected. In a Star topology, the central hub is the host computer, and at the end of each connection is a terminal, as shown in Figure.
Nodes communicate across the network by passing data through the hub. A star network uses a significant amount of cable as each terminal is wired back to the central hub, even if two terminals are side by side but several hundred meters away from the host.
The central hub makes all routing decisions, and all other workstations can be simple. An advantage of the star topology is that failure in one of the terminals does not affect any other terminal; however, failure of the central hub affects all terminals. This type of topology is frequently used to connect terminals to a large time-sharing host.
Advantages of Star Topology
- It is more reliable (if one connection fails, it does not affect others).
- The centre of a star network is a good place to diagnose network faults and if one computer fails the whole network is not disturbed. Hub detects the fault and isolates the faulty computer.
- It is easy to replace, install or remove hosts or other devices, the problem can be easily detected.
- It is easier to modify or add a new computer without disturbing the rest of the network by simply running a new line from the computer to the central location and plugging it to the hub.
- Use of multiple cable types in the same network with a hub.
Disadvantages of Star Topology
- It is expensive to install as it requires more cable, it costs more to cable a star network because all network cables must be pulled to one central point, requiring more cable length than other networking topologies.
- Central node dependency, if the central hub fails, the whole network fails to operate.
- Many star networks require a device at the central point to rebroadcast or switch the network traffic.
Devices are connected with many redundant interconnections between network nodes. In a well-connected topology, every node has a connection to every other node in the network. The cable requirements are high, but there are redundant paths built-in. Failure in one of the computers does not cause the network to break down, as they have alternative paths to other computers.
Mesh topologies are used in the critical connection of host computers (typically telephone exchanges). Alternate paths allow each computer to balance the load to other computer systems in the network by using more than one of the connection paths available.
Therefore, a fully connected mesh network has no (n-1) /2 physical channels to link n devices. To accommodate these, every device on the network must have (n-1) input/output ports.
Advantages of Mesh Topology
- Yield the greatest amount of redundancy in the event that one of the nodes fails where network traffic can be redirected to another node.
- Point-to-point link makes fault isolation easy.
- Privacy between computers is maintained as messages travel along a dedicated path.
- Network problems are easier to diagnose.
Disadvantages of Mesh Topology
- The amount of cabling required is high.
- A large number of I/O (input/output) ports are required.
A tree topology is a topology in which all the components are interconnected in a hierarchical manner. When you build a network topology in a tree, you are usually thinking of a mesh architecture.
The most common structure or topology is a Tree topology; Tree topology is a LAN topology in which only one route exists between any two nodes on the network. The pattern of connection resembles a tree in which all branches spring from one root.
Tree topology is a hybrid topology. It is similar to the star topology, but the nodes are connected to the secondary hub, which is connected to the central hub. In this topology group of star-configured networks are connected to a linear bus backbone.
Advantages of Tree Topology
- Installation and configuration of the network are easy.
- The addition of the secondary hub allows more devices to be attached to the central hub.
- Less expensive when compared to mesh topology.
- Faults in the network can be detected traces.
Disadvantages of Tree Topology
- Failure in the central hub brings the entire network to a halt.
- More cabling is required when compared to the bus topology because each node is connected to the central hub.
In conclusion, there are many different types of network topologies that can be used in a business. It is important to choose the right topology for the business in order to ensure that the network is efficient and meets the needs of the users. A call to action would be to consult with a network specialist to determine which topology is best for a business.