JOURNEY TO THE ICT SITE

before i tell more about the Network topology,, let me explain something about:

NIC

• A network interface controller (also known as a network interface card, network adapter, LAN adapter and by similar terms) is a computer hardware component that connects a computer to a computer network.
• Whereas network interface controllers were commonly implemented on expansion cards that plug into a computer bus, the low cost and ubiquity of the Ethernet standard means that most newer computers have a network interface built into the motherboard.

1. Physical topology refers to the physical design of a network including the devices, location and cable installation.
2. Logical topology refers to how data is actually transferred in a network as opposed to its physical design. In general physical topology relates to a core network whereas logical topology relates to basic network.

• point-to-point
• bus
• star
• ring or circular
• mesh
• tree
• hybrid
• daisy chain

• The simplest topology is 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.
• The value of an on-demand point-to-point connection is proportional to the number of potential pairs of subscribers, and has been expressed as Metcalfe's Law.
• the point to point topology is a type of physical topology

• A bus network is an arrangement in a local area network (LAN) in which each node(workstation or other device) is connected to a main cable or link called the bus. The illustration shows a bus network with five nodes.
• Each node is shown as a sphere, the bus appears as a heavy horizontal line, and connections to the bus appear as vertical lines.

• A bus network is simple and reliable. If one node fails to operate, all the rest can still communicate with each other. For a major disruption to take place, the bus itself must be broken somewhere. Bus networks are easy to expand.Additional nodes can be added anywhere along the bus.
• There are several limitations to the bus network topology. The length of the bus is limited by cable loss. A bus network may not work well if the nodes are located at scattered points that do not lie near a common line.In situations like this, a ring network, mesh network, or star network may prove more flexible and more cost effective.

• Alternatively referred to as a star network, a star topology is one of the most common network setups where each of the devices and computers on a network connect to a central hub.
• A major disadvantage of this network topology is that if the central hub fails, all computers connected to that hub would be disconnected.
• Below is a visual example of a simple computer setup on a network using the star topology. 

• A network topology that is set up in a circular fashion in which data travels around the ring in one direction and each device on the right acts as a repeater to keep the signal strong as it travels.
• Each device incorporates a receiver for the incoming signal and a transmitter to send the data on to the next device in the ring. The network is dependent on the ability of the signal to travel around the ring.

• Mesh network topology is one of the key network architectures in which devices are connected with many redundant interconnections between network nodes such as routers and switches.
• In a mesh topology if any cable or node fails, there are many other ways for two nodes to communicate.
• While ease of troubleshooting and increased reliability are definite pluses, mesh networks are expensive to install because they use a lot of cabling.
• Often, a mesh topology will be used in conjunction with other topologies (such as Star, Ring and Bus) to form a hybrid topology.
• Some WAN architecture, such as the Internet, employ mesh routing.Therefore the Internet allows sites to communicate even during a war.

• The type of network topology in which a central 'root' node (the top level of the hierarchy) is connected to one or more other nodes that are one level lower in the hierarchy (i.e., the second level) with a point-to-point link between each of the second level nodes and the top level central 'root' node, while each of the second level nodes that are connected to the top level central 'root' node will also have one or more other nodes that are one level lower in the hierarchy (i.e., the third level) connected to it, also with a point-to-point link, the top level central 'root' node being the only node that has no other node above it in the hierarchy (The hierarchy of the tree is symmetrical.) Each node in the network having a specific fixed number, of nodes connected to it at the next lower level in the hierarchy, the number, being referred to as the 'branching factor' of the hierarchical tree.
• This tree has individual peripheral nodes.

• Hybrid networks use a combination of any two or more topologies in such a way that the resulting network does not exhibit one of the standard topologies (e.g., bus, star, ring, etc.). For example, a tree network connected to a tree network is still a tree network topology.
• A hybrid topology is always produced when two different basic network topologies are connected.
• Two common examples for Hybrid network are: star ring network and star bus network.

• Except for star-based networks, the easiest way to add more computers into a network is by daisy-chaining, or connecting each computer in series to the next.
• If a message is intended for a computer partway down the line, each system bounces it along in sequence until it reaches the destination.
• A daisy-chained network can take two basic forms : linear and ring.