2. Network Topologies.pdf

Network Topologies Network Topology- In computer networking, topology refers to the layout of connected devices. In communication networks, a topology is a usually schematic description of the arrangement of a network, including its nodes and connecting lines. There are two ways of defining network geometry: the physical topology and the logical (or signal) topology.

Network Topologies 1. Logical Topology- Nature of the paths the signals follow from node to node. In many instances, the logical topology is the same as the physical topology. But this is not always the case. 2. Physical Topology- Actual geometric layout of workstations. Network topologies are categorized into the following basic types:

Types of Physical Topology

Network Topologies a. Point to Point Topology- The simplest topology with a permanent link between two endpoints. Switched point-to-point topologies are the basic model of conventional telephony. The value of a permanent point-to-point network is unimpeded communications between the two endpoints.

Point-to-Point

Advantages: i. ii. iii. iv.

Lower Cost. Easy to setup. Good for temporary network setup. Use for connecting one area to another using a high speed connection.

Disadvantages: i. ii. iii.

Limited growth. No central location. Weak Security.

b. Ring Topology- In Ring Topology, all the nodes are connected to each-other in such a way that they make a closed loop. A failure in any cable or device breaks the loop and can shut down the entire network. Every data packet must pass through all the computers between sender and receiver.

Ring Topology

Network Topologies Advantages: i. ii. iii. iv.

Data is quickly transferred without a ‘bottle neck’ (very fast, all data traffic is in the same direction). The transmission of data is relatively simple as packets travel in one direction only. Adding additional nodes has very little impact on bandwidth. It prevents network collisions because of the media access method or architecture required.

Disadvantages: i. ii. iii.

iv.

The failure of a single node in the network can cause the entire network to fail. The movement or changes made to network nodes affect the entire network's performance. Data sent from one node to another has to pass through all the intermediate nodes. This makes the transmission slower in comparison to that in a star topology. The transmission speed drops with an increase in the number of nodes. There is heavy dependency on the wire connecting the network nodes in the ring.

c. Star Topology- One of the most common network setups where each of the devices and computers on a network connect to a central hub. If the central computer fails, the entire network becomes unusable.

Star Topology

Network Topologies Advantages: i. ii. iii. iv. v.

Good performance. Easy to set up and to expand. Any non-centralised failure will have very little effect on the network, whereas on a ring network it would all fail with one fault. Adding or removing network nodes is easy, and can be done without affecting the entire network. Due to the centralized nature, it is easy to detect faults in the network devices. As the analysis of traffic is easy, the topology poses lesser security risk.

Disadvantages: i. ii. iii. iv.

Expensive to install. Extra hardware required. Network operation depends on the functioning of the central hub. Hence, central hub failure leads to failure of the entire network. Also, the number of nodes that can be added depends on the capacity of the central hub.

d. Bus Topology- A bus topology is a type of network setup where each computer and network devices are connected to a single cable or backbone. A bus network is simple and reliable. If one node fails to operate, all the rest can still communicate with each other.

Bus Topology Advantages: i. ii. iii. iv. v.

It is easy to set up, handle, and implement. It is best-suited for small networks. Well suited for temporary networks (quick setup). Initially less expensive than other topologies. Cheap.

Network Topologies Disadvantages: i. ii.

iii. iv. v. vi. vii. viii. ix.

The cable length is limited. This limits the number of network nodes that can be connected. This network topology can perform well only for a limited number of nodes. When the number of devices connected to the bus increases, the efficiency decreases. It is suitable for networks with low traffic. High traffic increases load on the bus and the network efficiency drops. It is heavily dependent on the central bus. A fault in the bus leads to network failure. It is not easy to isolate faults in the network nodes. Each device on the network "sees" all the data being transmitted, thus posing a security risk. Difficult to administer/troubleshoot. Low security. Proper termination is required.(loop must be in closed path).

e. Mesh Topology- A network setup where each computer and network device is interconnected with one another, allowing for most transmissions to be distributed, even if one of the connections go down. The flow of information is random and the source to destination path of this information can take many paths.

Mesh Topology

Network Topologies Advantages: i. ii. iii. iv. v.

The arrangement of the network nodes is such that it is possible to transmit data from one node to many other nodes at the same time. The failure of a single node does not cause the entire network to fail as there are alternate paths for data transmission. It can handle heavy traffic, as there are dedicated paths between any two network nodes. Point-to-point contact between every pair of nodes makes it easy to identify faults. Mesh topologies aren’t affected by size or a shortage of users.

Disadvantages: i. ii. iii.

f.

The layout of a mesh topology requires constant supervision and is very expensive to implement. A lot of cabling is required. Owing to its complexity, the administration of a mesh network is difficult.

Tree Topology- A tree topology is a type of network topology that includes at least three specific levels in a topology hierarchy. Experts may define a tree topology as a combination of star and bus topologies, where multiple elements are connected through a single lateral connection.

Tree Topology

Network Topologies Advantages: i. ii. iii. iv. v. vi.

Experts may define a tree topology as a combination of star and bus topologies, where multiple elements are connected through a single lateral connection. Expansion of Network is possible and easy. Error detection and correction is easy. Each segment is provided with dedicated point-to-point wiring to the central hub. If one segment is damaged, other segments are not affected. The advantages of centralization that are achieved in a star topology are inherited by the individual star segments in a tree network.

Disadvantages: i. ii. iii.

Because of its basic structure, tree topology, relies heavily on the main bus cable, if it breaks whole network is crippled. Owing to its size and complexity, maintenance is not easy and costs are high. Also, configuration is difficult in comparison to that in other topologies. Though it is scalable, the number of nodes that can be added depends on the capacity of the central bus and on the cable type.