Network Basic

Basic Concept of Network

A network is a collection of computers and devices connected together via communication devices and transmission media 

Computer Comunication

process in which two or more computers or devices transfer data, instructions and information

Communications System

• sending device : initiates an instruction to trasmit data, instruction and information
• communication device : connects the sending device to a communication channel
• communication channel / transmission media : which the data, instructions or information travel
• communication device : connects the communicatin channel/transmission media to a receiving device
• receiving device : accepts the transmission of data, instruction or information  

 Communication device : 

• hub
• switch
• router
• network interface card (NIC)

Transmission media :

• telephone line
• cable tv
• power line
• fiber optic
• satellite
• radiowave
• microwave

Network 

A network is a collection of computers and devices connected together via communication devices and transmission media.

Advantages of network :

• facilitating communication
• sharing hardware
• sharing software
• sharing data and information
• transfering funds

Disadvantages of network :

• viruses
• network failure
• slow service
• cost
• expert support required

Network Architecture

Network architecture is the design of computers and media on a network
Types of network architecture :  

• peer-to-peer (P2P)
• client server 

Peer-to-peer

• a collection of computers and other devices to share resources where computer have equal capabilities and responsibilities

Client Server 

• one or more computers act as a server and the other computers on the network request services from the server.
• Client : a host computer that supply/provide resources to client on the network
• Server : other computer and devices that request resources from the server on the network  

Network Topology

A network topology refers to the layout of the computers and devices in a communication network
Divided into :

• physical : the arrangement of a cabling
• logical : the path that data travels between computers on a network

Types of network topology :

• bus network
• star network
• ring network

Bus Network Topology

Physical :
consists of a single central cable (backbone) to which all computers and other devices connect

Logical :

• transmit data, instruction and information as a series of signal
• those signal are sent as electrical pulses that travel along the cable in all directions
• each devices is connected through T-connector
• a terminator is required at each end to prevent the signal from bouncing back 

Advantages :

• inexpensive and easy to install
• other devices can be attached and detached at any point without disturbing the network
• failure of one device dows not affect the network

Disadvantages :

• there's a disruption when other devices are added or removed
• difficult to identify the problem if the network is shut down

 

Star Topology

Physical :
All computers and other devices on the network connect to a central device thus forming a star

Logical :

• two types of central device that provide central connection point to all the devices on the network are hub and switch  
• all data that transfers from one divice to another passes through the hub or switch

Advantages :

• affect the whole network if one device fails
• other device can be added or removed from the network with no disruption
• easy to troubleshoot problem

Disadvantages :

• hub or switch fail, the entire network will fail
• requires more cable 
• more expensive because of the cost of the hub/switch

 

Ring Topology

Physical :
A cable forms a closed loop (ring) with all computers and devices arranged along the ring

Logical :

• data travels from one device to device around the ring in one direction
• token passing is the method for sending data around the ring
• each device takes a turn sending information through the use of a token
• only the device with the token is allowed to send data while the othe device must wait for their turn

Advantages :

• transmission of data is simple as it travel in one direction
• troubleshooting is easier
• the use of token enable all devices to share the network resources fairly

Disadvantages :

• a failure in any cable or device will breaks the loop and take down the entire network
• slower because data packets must pass throuh every computer 
• more difficult to install