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Why have networks?
Why have networks?
The original computers were standalone computers, not connected to any other machine or device. As computers became more widely used in the military, universities and industry, the need to connect computers together became paramount.
The advantages of networking include:
Hardware sharing, such as the sharing of printers and scanners.
Communication – Is the ability to send information between computers, networks and countries.
The disadvantages of networking include:
Reduced security – each new device added to the network is a new potential site of attack for a hacker.
Increased complexity – there are more devices to configure and more devices to break
Increased cost – networks require additional dedicated hardware to function.
Client-Server Network
Most organisations use a form of client – server networks. This is where access to network resources and overall control of the network is governed by the server. A server is a special kind of computer that is designed to cope with a large number of requests at the same time.
Servers control:
User access levels and authentication
File access and backup
Hardware resource sharing(such as printers and scanners)
Internet connection sharing and access control
Users log on to client computers, which connect to the network and access the shared resources.
Local Area Network (LAN)
Local Area Network (LAN)
A client – server network located in a single location is known as a Local Area Network (LAN). These networks are usually located in a single building or within a Small Geographical area
Wide Area Network (WAN)
Wide Area Network (WAN)
If an organisation is spread across a large site (such as a university campus) then each area would contain a single LAN, but all the LANs would be joined together using a bridge, router or modem, in order to form a large Wide Area Network.
This allows multiple LANs to:
Share access to devices such as printers and scanners
Share file access across multiple LANs
Share access to a single internet service.
The internet is a very, very large WAN.
Peer to Peer Networks
Peer to Peer Networks
Peer to Peer networks is usually temporary and quick to set up. They are usually used for temporary file and resource sharing, where a larger client-server network is not needed. Each device connected to a Peer to Peer network is a node, and each node forwards on data to all other nodes in range.
Advantages
Quick, easy and cheap to set up – no server, switch or routers required.
Decentralised, meaning that if one ‘node’ goes down, the network still remains up.
Some peer-to-peer networks (such as TOR networks) allow users to communicate anonymously, making it difficult to trace user activity.
Disadvantages
No access to the facilities that servers provide ( file backup, use authentication)
Less secure than standard networks
Network Topology
Network Topology
A network's topology is the arrangement, or pattern, in which all nodes on a network are connected together. There are several common topologies that are in use, but today the most common topologies are:
Star
Ring
Bus
Mesh
bus.mp4Ring.mp4star.mp4Star Topology
Star Topology
In a star topology, all nodes indirectly connect to each other through one or more switches. The switch acts as a central point through which all communications are passed. Large networks using a star topology are usually controlled by one or more servers. Hence, the client-server model usually uses a star topology.
Advantages
Easier to manage and more secure
Fast overall network speed due to dedicated hardware
Disadvantages
If the switch or server goes down, the whole network goes down.
Expensive to set up
Bus Topology
Bus Topology
In a bus topology, all nodes in the network are connected directly to a central cable that runs up and down the network - this cable is known as the backbone. Data is sent up and down the backbone until it reaches the correct node.
Advantages
t is easy to connect nodes to the network
less cabling is needed compared to a star topology, making it cheaper to install
Disadvantages
the whole network fails if the backbone cable is broken
terminators must be installed at each end of the backbone
having one backbone increases the chances of data collision
Ring Topology
Ring Topology
In a ring network, each device (workstation, server, printer) is connected to two other devices - this forms a ring for the signals to travel around. Each packet of data on the network travels in one direction and each device receives each packet in turn until the destination device receives it.
Advantages
This type of network can transfer data quickly, even if there are a large number of devices connected because the data only flows in one direction, so there won’t be any data collisions.
Disadvantages
If the main cable fails or any device is faulty, then the whole network will fail.
Peer to Peer Networks (P2P)
Peer to Peer Networks (P2P)
Peer to Peer networks is quick to set up. They are usually used for temporary file and resource sharing, where a larger client-server network is not needed. Each device connected to a Peer to Peer network is a node, and each node forwards on data to all other nodes in range.
Advantages
Quick, easy and cheap to set up – no server, switch or routers required.
Decentralised, meaning that if one ‘node’ goes down, the network still remains up.
Some peer-to-peer networks (such as TOR networks) allow users to communicate anonymously, making it difficult to trace user activity.
Disadvantages
No access to the facilities that servers provide ( file backup, use authentication)
Less secure than standard networks
Mesh Topology
Mesh Topology
This type of topology is commonly used to peer to peer networks.
Advantages
Quick and cheap to set up
If one node goes down, the whole network doesn’t go down
Can be used to connect devices where wireless / wired internet access doesn’t exist
Disadvantage
Generally slower network than a star.
Less secure
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