Networks

What is a network?
A network is a linked set of computer systems which may be capable of sharing computer power and resources such as printers and databases.

Network topology:
A topology is the theoretical arrangement of components of a network.
Actual arrangements are determined by physical factors
Topologies will affect:
- Cost
-Performance
-Ease of installation

The types of topology:

Star:

• Shared link to server(s)
• Central node is the Hub
• Few data collisions
• Fast, robust and cost effective
• Can  set up independent segments
• the hub can be another node or switch
• The Hub has a separate connection  to each node

Bus :

• This uses one common linking cable (bus)
• Cheapest network design
• Network will slow down when there is heavy traffic
• Network is prone to lots of data collisions
• Breakage to the bus will affect the whole network.
• Only a limited distance can be covered.
• Terminators are required for this topology, which denote the start and end point of the bus line, to detect when data has not reached its destination.

Ring:

• One direction traffic
• fast performance
• Every node is required to have a network interface controller which allows it to communicate across a network using a series of protocol.
• Data will pass through the NIC of each node

Mesh:

• Most common type of network
• Using decentralised design
• can be wired or wireless
• no single point of failure
• each node connects to 2+ other nodes
• Nodes communicate directly with one another without needing internet connection.

All Types of network topology:



















LAN:

• Local Area Network
• Networked computers are located fairly near to one another geographically
• An example is all the computers in a school or office.
• Each devices is called a node.
• The entire infrastructure is owned by the organisation who own the LAN.
• All infrastructure is the responsibility and maintained by the organisation or individual
• Some equipment can be leased form external companies- in this case the companies is responsible and in control of repairing it. Usually to do with routers or wireless access points

Advantages:

• allows communication between workers
• allows data/files/information to be shared
• peripherals can be shared e.g. printers
• computers (software) can be updated/upgraded more easily (also virus scans)
• Log on from any connected machine
• Distributed processing where a program can be run simultaneously on may nodes

LAN Hardware:

• NIC- needed to connect to a LAN, allows computer to communicate over a network by providing physical access to a network and provides a unique address for each the node, the MAC (Media Access Control) address.
• Router:
• forwards data packets across many networks so are different to switches. They reseieve packets read the address information and use a routing table to forward thje packet to the next network
• Switch:
•  Allows network segments to be created and reduces data collisions and is hardware within the network for internal communication, a router forwards data packets across many networks so are different

Wireless access point (WAP):

• Allows wireless devices to connect to a wired network
• uses WI-FI, Bluetooth or related standards
• Usually connects to a router via a wired network.
• can relay data between the wireless and wired data 

WAN:

• Wide area Network
• Computers are located in various distant locations geographically 
• WAN is the result of joining two or more geographically separate LANs via satellite, fibre-optic cables, telephone lines or a combination of these.
• The infrastructure may be provided by telecoms companies.
• The largest WAN in existence is the Internet.#

SAN:

• Storage Area Network
• Dedicated network used for large scale storage of data in data centres.
• Common uses of a SAN include email servers, databases, and high usage file servers

PAN:

• Personal Area Network
• Used for data transmission among devices such as computers, smartphones & tablets. Can be used for communication between personal devices or to connect to a higher level network and / or Internet.

The Cloud:

• Data storage and services moved off site
• 3rd party manages maintenance, security, backups etc.

Advantages:

– No in-house maintenance

– Cheaper (less staff)

Disadvantages:

–loss of control / Security

–Relies on an internet connection