NETWORK????

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 A network is defined as a group of two or more computer systems linked together. There are many types of computer networks, including the following: local-area networks

Network can be divide by two, First, network architecture and second, network topology.

Network Architecture Types

Peer-to-Peer Architectures


In a peer-to-peer architecture model, a system is decomposed into computational nodes that have equivalent capabilities and responsibilities. This division is in contrast to a client-server architectural model, where client and server nodes are divided into server and client roles.


An example of a peer-to-peer architecture is a system of intelligent agents that collaborate to collect, filter, and correlate information.

CLIENT SERVER Architectures

each computer or process on the network is either a client or a server. Server are powerful computers or processes dedicated to managing disk drives (file servers), printers (print servers), or network traffic (network servers ). Clients are PCs or workstations on which users run applications. Clients rely on servers for resources, such as files, devices, and even processing power.

NETWORK TOPOLOGY

A network topology refers to the layout of the computer and devices in a communications network

PHYSICAL : the physical layout of nodes, workstation and cable in the network

LOGICAL: the path that data travels between computer on a network

TYPES OF NETWORK TOPOLOGY

BUS Topology

Bus topology is a network type in which every computer and network device is connected to single cable. When it has exactly two endpoints, then it is called Linear Bus topology.

Features of Bus Topology

• It transmits data only in one direction.
• Every device is connected to a single cable

Advantages of Bus Topology

• It is cost effective.
• Cable required is least compared to other network topology.
• Used in small networks.
• It is easy to understand.
• Easy to expand joining two cables together.

Disadvantages of Bus Topology

• Cables fails then whole network fails. 
• If network traffic is heavy or nodes are more the performance of the network decreases. 
• Cable has a limited length. 
• It is slower than the ring topology.

RING Topology

It is called ring topology because it forms a ring as each computer is connected to another computer, with the last one connected to the first. Exactly two neighbours for each device.

Features of Ring Topology

• A number of repeaters are used for Ring topology with large number of nodes, because if someone wants to send some data to the last node in the ring topology with 100 nodes, then the data will have to pass through 99 nodes to reach the 100th node. Hence to prevent data loss repeaters are used in the network.
• The transmission is unidirectional, but it can be made bidirectional by having 2 connections between each Network Node, it is called Dual Ring Topology.
• In Dual Ring Topology, two ring networks are formed, and data flow is in opposite direction in them. Also, if one ring fails, the second ring can act as a backup, to keep the network up.
• Data is transferred in a sequential manner that is bit by bit. Data transmitted, has to pass through each node of the network, till the destination node.

Advantages of Ring Topology

• Transmitting network is not affected by high traffic or by adding more nodes, as only the nodes having tokens can transmit data.
• Cheap to install and expand

Disadvantages of Ring Topology

• Troubleshooting is difficult in ring topology. 
• Adding or deleting the computers disturbs the network activity. 
• Failure of one computer disturbs the whole network.

STAR Topology

In this type of topology all the computers are connected to a single hub through a cable. This hub is the central node and all others nodes are connected to the central node.

Features of Star Topology

• Every node has its own dedicated connection to the hub.
• Hub acts as a repeater for data flow.
• Can be used with twisted pair, Optical Fibre or coaxial cable.

Advantages of Star Topology

• Fast performance with few nodes and low network traffic. 
• Hub can be upgraded easily. 
• Easy to troubleshoot. 
• Easy to setup and modify. 
• Only that node is affected which has failed, rest of the nodes can work smoothly.

Disadvantages of Star Topology

• Cost of installation is high. 
• Expensive to use. 
• If the hub fails then the whole network is stopped because all the nodes depend on the hub. 
• Performance is based on the hub that is it depends on its capacity