Network Topology
Computer network topology: The way computers are connected to each other in a network is called topology. This topology plays a special role in network design. The appropriate topology needs to be selected based on which network will be used for which task.
Types of network topology: Computer network topology is mainly of two types, namely-
(i) Physical Topology and
(ii) Logical Topology.
Physical topology: Networking media is associated with various network devices. That layout is called physical topology. Physical topology can be divided into the following six categories, namely--
(i) Bus Topology
(ii) Ring Topology
(iii) Star Topology
(iv) Tree Topology
(v) Mesh Topology
(vi) Hybrid Topology
Bus Topology: In bus topology all the computers (nodes) are connected with a single connection line. Here the connection line is usually called a bus. When a computer sends a message to another computer, the message signal travels through the connection line and reaches all the other computers. Other computers examine the message and only the recipient computer receives the message. In a bus topology only one computer can send messages at a time. When a computer sends a message, others have to wait until it finishes sending. Therefore, when the number of computers in the network increases, the performance deteriorates.
Advantages of bus topology:
(i) Very simple, low cost and easy to use for small networks.
(ii) Requires less cable length.
(ii) The bus network can be extended by connecting the bus to another bus using BNC barrel connectors.
Bus Disadvantages:
(i) Performance may be very poor if network usage is high.
(ii) Each barrel connector weakens the electrical signal.
(iii) Bus network troubleshooting is difficult.
Star topology: In star topology, all computers are connected to a central location. At this central network location is a device called a concentrator or hub. No computer can send data directly to another computer. When a computer sends data to another computer, it first sends it to the hub. The hub sends that data to all computers or critical computers
Advantages of Star Topology:
(i) More computers can be easily added to the network.
(ii) Failure of any computer in the network does not affect the network.
(iii) The hub supports different network types, allowing the use of several types of cables simultaneously.
Disadvantages of Star Topology: The main disadvantage of this type of network is that if the hub goes down, the entire network is down. Besides, this topology requires more cables. As a result, the cost is higher.
Ring Topology: In this case, the computers build a network connected to each other in a circular way through the nodes (the points to which the computers are connected are called nodes). Thus the last computer is connected to the first one (Fig-7.3). In such a topology, each device has a receiver and a transmitter, which acts as a repeater. In this case, the responsibility of the repeater is to transfer the signal from one computer to the next computer.
Advantages of Ring Topology:
(i) Every computer has equal access to the network. Because the token goes to every computer.
(ii) Since all computers have equal access, network degradation also occurs equally.
Disadvantages of Ring Topology: The main disadvantage of this type of network is that if any one computer fails, the entire network is down.
Tree topology: In this case all the computers are connected in a particular place. There are high speed connections that are connected to the main computer to increase their signal sending speed. In this organization one or more tiers of computers are connected to the host computer. Layer 2 computers are connected to layer 3 computers. Layer 2 computers act as hosts for layer 3 computers.
Advantages of Tree Topology:
(i) Network expansion of tree topology by creating new Brahmas is quite convenient.
(ii) This network structure is more useful for office management.
(iii) Easy to connect or remove new nodes. Normal operation of the network is not disrupted. \
Disadvantages of Tree Topology:
(i) Tree network goes down if root or server computer fails.
(ii) Relatively complex compared to other topologies.
Mesh Topology: In this case every computer is directly connected to other computers. The main advantage of this organization is that any two nodes can exchange signals very quickly. Apart from that, if a computer or connection line goes down, the network does not suffer much. The main disadvantage of this organization is that the cost is very high due to the long length of connection lines.
Advantages of Mesh Topology:
(i) Signals can be exchanged between any two nodes at high speed.
(ii) Failure of a computer or connection line does not cause any inconvenience.
(iii) It provides greater assurance in data communication.
(iv) Network problems can be solved very easily.
(v) Infrastructure is very strong.
Disadvantages of Mesh Topology:
(i) Network installation and configuration in this topology is quite complex.
(ii) Longer length of connecting lines leads to higher cost. Apart from that, additional links have to be established in the network, thus increasing the cost.
Hybrid topology: The network that is formed by the combination of bus, ring, star, tree, mesh etc. topology or network is called hybrid topology.
Advantages of Hybrid Topology/Network:
(i) The network can be scaled up as per requirement.
(ii) Easier to diagnose any network problem.
Disadvantages of Hybrid Topologies/Networks:
(i) Relatively expensive.
(ii) Relatively complex compared to other topologies.
Logical Topology: How data will be transported to devices connected to physical topology is understood through logical topology. Logical and physical topologies are dependent on each other. There can be two types of logical topology, viz
(i) Logical bus topology and
(ii) Logical ring topology.
Logical bus topology: Physical star topology is generally used in Ethernet networks. When a physical star topology is used, all computers are connected to the hub. Any signal to be transmitted from any device must pass through the hub. is It uses logical topology for signal transport.
Advantages of Logical Bus Topology:
(i) Failure of one computer does not render the entire network useless.
(ii) It is the most used logical topology.
Disadvantages of Logical Bus Topology:
(i) Only one device can send data at a time.
(ii) Collision may occur if multiple computers want to send data simultaneously.
Logical ring topology: If data is transported in the form of a ring in a physical topology, then it is called a logical ring topology. A practical example of a logical ring topology is a token ring network. On the other hand, FDDI network is also logical ring topology.
Comments
Post a Comment