Network Topology and Types

What is a network topology?
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.


Bus Topology:
In this type of network topology, all the nodes of a network are connected to a common transmission medium having two endpoints. All the data that travels over the network is transmitted through a common transmission medium known as the bus or the backbone of the network. When the transmission medium has exactly two endpoints, the network topology is known by the name, ‘linear bus topology'. In case the transmission medium, also called as the network backbone, has more than two endpoints, the network is said to have a distributed bus topology. Bus topology is easy to handle and implement and is best suited for small networks. But the downside of this topology is that the limited cable length limits the number of stations, thus limiting the performance to a less number of nodes.
Ring Topology:
In a ring topology, every node in the network is connected to two other nodes and the first and the last nodes are connected to each other. The data that are transmitted over the network pass through each of the nodes in the ring until they reach the destination node. In a ring network, the data and the signals that pass over the network travel in a single direction. The dual ring topology varies in having two connections between each of the network nodes. The data flow along two directions in the two rings formed thereby. The ring topology does not require a central server to manage connectivity between the nodes and facilitates an orderly network operation. But, the failure of a single station in the network can render the entire network inoperable. Changes and moves in the stations forming the network affect the network operation.
Mesh Topology:
In a full mesh network, each network node is connected to every other node in the network. Due to this arrangement of nodes, it becomes possible for a simultaneous transmission of signals from one node to several other nodes. In a partially connected mesh network, only some of the network nodes are connected to more than one node. This is beneficial over a fully connected mesh in terms of redundancy caused by the point-to-point links between all the nodes. The nodes of a mesh network require possessing some kind of routing logic so that the signals and the data traveling over the network take the shortest path during each of the transmissions.
Star Topology:
In this type of network topology, each node of the network is connected to a central node, which is known as a hub. The data that is transmitted between the network nodes passes across the central hub. A distributed star is formed by the interconnection of two or more individual star networks. The centralized nature of a star network provides a certain amount of simplicity while also achieving isolation of each device in the network. However, the disadvantage of a star topology is that the network transmission is largely dependent on the central hub. The failure of the central hub results in total network inoperability.
Tree Topology:
It is also known as a hierarchical topology and has a central root node that is connected to one or more nodes of a lower hierarchy. In a symmetrical hierarchy, each node in the network has a specific fixed number of nodes connected to those at a lower level. Apart from these basic types of network topologies, there are hybrid network topologies, which are composed of a combination of two or more basic topologies. These network mappings aim at harnessing the advantages of each of the basic topologies used in them. Network topologies are the physical arrangements of network nodes and wires. What is interesting is that the inanimate nodes and wires turn 'live' for the transmission of information.
Hybrid Topology:
A combination of any two or more network topologies. Instances can occur where two basic network topologies, when connected together, can still retain the basic network character, and therefore not be a hybrid network. For example, a tree network connected to a tree network is still a tree network. Therefore, a hybrid network accrues only when two basic networks are connected and the resulting network topology fails to meet one of the basic topology definitions. For example, two star networks connected together exhibit hybrid network topologies. Note 2: A hybrid topology always accrues when two different basic network topologies are connected.

Introduction to Computer Networks

Definitions of:

1. LAN: A local area network (LAN) is a group of computers and associated devices that share a common communications line or wireless link. Typically, connected devices share the resources of a single processor or server within a small geographic area (for example, within an office building).

2.MAN:A Metropolitan Area Network (MAN) is one of a number of types of networks (see also LAN and WAN). A MAN is a relatively new class of network, it serves a role similar to an ISP, but for corporate users with large LANs. There are three important features which discriminate MANs from LANs or WANs.

3. WAN: wide area network (WAN) is a geographically dispersed telecommunications network. The term distinguishes a broader telecommunication structure from a local area network (LAN). A wide area network may be privately owned or rented, but the term usually connotes the inclusion of public (shared user) networks. An intermediate form of network in terms of geography is a metropolitan area network (MAN).

4.PAN: A personal area network (PAN) is the interconnection of information technology devices within the range of an individual person, typically within a range of 10 meters. For example, a person traveling with a laptop, a personal digital assistant (PDA), and a portable printer could interconnect them without having to plug anything in, using some form of wireless technology. Typically, this kind of personal area network could also be interconnected without wires to the Internet or other networks.

5.VPN:VPN is a private network that uses a public network (usually the Internet) to connect remote sites or users together. Instead of using a dedicated, real-world connection such as leased line, a VPN uses "virtual" connections routed through the Internet from the company's private network to the remote site or employee. In this article, you will gain a fundamental understanding of VPNs, and learn about basic VPN components, technologies, tunneling and security.

6.CAN: Is a high-integrity serial data communications bus for real-time control applications.
Operates at data rates of up to 1 Mega bits per second.
Has excellent error detection and confinement capabilities
Was originally developed for use in cars
Is now being used in many other industrial automation and control applications
Has an OSI session layer known as Time Triggered CAN (TTCAN)
Has a sub-bus known as the Local Interconnect Network (LIN)
CAN is documented in ISO 11898 (for applications up to 1 Mega bits per second) and ISO 11519 (for applications up to 125 K bits per second)

7. SAN: Storage Area Network (SAN) is a high-speed subnetwork of shared storage devices. A storage device is a machine that contains nothing but a disk or disks for storing data.
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