1. LO3 – Understand Business IT Systems
3.3 – Networking Characteristics

2. Networking Characteristics
A Network is two or more computers connected together to share information and resources.
Peer-to-Peer Network
In this configuration there is no central server. Instead, each workstation is loaded with the appropriate applications needed for that machine and local resources such as an attached printer folder or external hard drive can be shared.
The peer-peer network form is most commonly found in the home or a small office.
In this set-up the Modem / Router is providing access to the internet, it is providing wireless access to the network and it may be set up to issue an IP address for each machine , this is called a DHCP host or 'Dynamic Host Configuration Protocol. If a new computer is plugged into the network, it requests an IP address from the router.
The peer to peer configuration is popular because it is simple to set up.
You purchase a modem / router for an internet connection. Configure it as a DHCP host from its set-up menu - it may default to this in any case. Then connect it to a switch or hub with some network cable.
Attach other computers either directly with a network cable to the hub or use a wireless connection.
It is also quite cheap compared to a client-server set up. No server costs and no high technical expertise to maintain it.
Each computer is set up to share folders and peripherals such as printer, scanner, external hard drive.
Disadvantages
The main issue is that every machine is effectively independent.
Each one needs the correct applications loaded.
Your data is held on a specific machine which must be powered up. Although setting up a 'share' will allow you to see this on the other machines too
Each one needs its own anti-virus scanner
Each one needs its own backup schedule - either by backing up to a networked external hard drive or to its own external storage device

3. Client-Server Network
A client server network has a powerful computer known as a server which provides all of the services required on the network. These can include directing traffic around the network, managing disk drives and network peripherals such as printers and scanners.
The 'client' part of the network are the workstations that people log onto in order to use the network facilities.
This is the type of network most often used in middle to large organisations. In larger set-ups there may be several servers on the network, each one dedicated to a task or service. For instance there could be:
A print server which handles all of the print jobs required by network users
An server which provides a centralised service for all network users
File servers. There may be several file servers to provide plenty of storage capacity
An authentication server which handles all log-in and security measures
A web server to provide an internal intranet service
Domain Name Servers (DNS) are the Internet's equivalent of a phone book. They maintain a directory of domain names and translate them to Internet Protocol (IP) addresses. This is necessary because, although domain names are easy for people to remember, computers or machines, access websites based on IP addresses. Information from all the domain name servers across the Internet are gathered together and housed at the Central Registry. Host companies and Internet Service Providers interact with the Central Registry on a regular schedule to get updated DNS information. When you type in a web address, e.g., your Internet Service Provider views the DNS associated with the domain name, translates it into a machine friendly IP address (for example is the IP for jimsbikes.com) and directs your Internet connection to the correct website.
A client-Server Network
More information here

4. Client-Server Network - advantages
There are strong economic and practical reasons why the client-server topology is the preferred one for organisations such as schools, businesses, hospitals, government and so on.
1. All data and applications held centrally
2. Shared peripheral resources
Peripherals such as a heavy duty Laser Printer are expensive to purchase and maintain so it is best to make maximum use of them. This can be done by sharing the peripheral between all the clients. The server receives a print job from a client and sends it to the printer.

5. Client-Server Network - disadvantages

6. Client-Server Network/Peer to Peer Network Comparison

7. Network Topologies

8. Network Topologies
The word topology means ‘arrangement’, so when we talk about the topology of a network, we mean how the different parts are arranged and connected together.
Once you have decided to network a number of computers together, the next decision which needs to be made is which network layout or topology would be the best to use.
There are a number of different topologies to choose from, the three most popular being bus, ring and star.
Bus Network Topology
This is one method of connecting computers together and is the simplest one to connect together.
A single cable joins all of the workstations, printer, file server and other components together. At each end of the bus is a 'terminator'. This is a piece of hardware which prevents signals bouncing back and forth (echoes).
Advantages
Easy to install
Cheaper in cabling terms than a star network
Easy to add extra workstations
Transmissions are in both directions
Best choice for temporary networks
Attaching a new device is easy, so if one peripheral fails the others are not affected
Disadvantages
If there is a problem with the central cable, the entire network stops working
If there are a lot of workstations on the network, data can travel slowly.
Data collisions can happen as the network becomes busy
Low security - every workstation can see all of the data in the network
Limited cable length and a maximum number of workstations
Difficult to identify a faulty device
Animation of Bus Network Here

9. Ring Network Topology
In a ring network layout, all of the computers are connected to one another in a circle. The data passes from one computer to the next one and then all the way around the ring layout until it reaches the destination computer.
Ring networks have one directional communication through a cable. The message is received by each computer in the ring between the sender and receiver. Each computer in the chain sends the data packet to the next computer until the receiving device receives it. Often the message is boosted or regenerated to maintain signal strength.
Rings use a method known as token passing to prevent problems of multiple messages on the network colliding. A small data packet known as the token is continuously transmitted around the ring. When a device has data to transmit, it has to wait until the token arrives. At that point, the computer checks to see if the token is already being used by another device. If not, it adds its own data and control information such as the address of the receiving device and sends the token on its way. When the notice of safe delivery is received the token is released back to the ring.
Advantages
Transmission of data is fairly simple as it only travels in one direction
No data collisions
Extra computers can be added easily with little effect on performance – although
you have to shut down the network to be able to do this.
Disadvantages
If a single machine is switched off, the network doesn't work
If a cable breaks, the network doesn't work
Data must pass through every computer until it reaches its destination. This can make it slower than other network layouts.
If there are any problems with the network, they can be difficult to identify the cause.
Animation of Ring Network Here

10. Star Network Topology
The star network has a central device directly contected to all other nodes. Just like a star shape. The central node could be a hub, switch or a server.
Star networks are usually the layout of choice in schools and offices because they tend to be the most reliable of the topologies.
Advantages
Star networks are very reliable. If one connection fails, it does not affect other users
Very few data collisions as each workstation has its own cable to the server
Good security - no workstation can interact with another without going through the server first
Simple to add or remove a node as it has no effect on any other node
Scalability – can add many new nodes
Disadvantages
The most expensive network layout to install because of the amount of cables needed
Installing the network usually needs experts to set it up
Extra hardware such as hubs and switches may be needed
If the central switch or server fails, the whole network in down
Requires a high performance switch or server in the centre as all traffic passes through it
Animation of Star Network Here

11. Mesh Network Topology A full mesh network
In a mesh network, each node relays the data it receives to other nodes within reach. \unlike a star network, there is no central node in a mesh network.
Using cables to connect the nodes, means that a wired mesh network would rapidly become too expensive and complicated. However, when the connections are wireless, a mesh network offers significant advantages over a star topology.
Examples of Mesh Uses:
Music streaming – maximising range with the house as each device relays music to other devices within range
In factories (Dozens of sensors on the assembly floor transmit data and relaying them in to the factory floor. If one sensor fails, the others just carry on
The military – have battlefield mesh networks in place to allow soldiers to communicate with one another, due to the robust technology
A full mesh network
This shows that each device connects to every other device with a cable

12. Mesh Topology Networks cont…..
Advantages
Excellent wireless range: Most of the nodes are in the orange wireless range
and so can easily exchange data with one another/ But the red device is out of
range of every node except the blue one. And yet, that is all that is needed to
allow it to join the overall network.
Very Robust: If one node fails, then other nodes within range allow data transmission
around the network to continue. There is no central not to fail
Excellent for wireless networks as each node re-broadcasts all the data packets it receives
It can handle very high data traffic rates
Data packets can be sent simultaneously
Devices can join or leave the network without affecting the overall network
Disadvantages
The number of connection increase massively as more nodes are added
Rapidly becomes an impractical topology for wired nework as so many cables would be needed
Very expensive for a wired network due to cabling and switches needed
Needs complex co-ordination to be effective

13. Addressing, IP and Default Gateway

14. Addressing
Consider that a number of devices are networked and need to exchange data with one another. These are connected as a local network. They also want to exchange data with other networks across the internet.
How to do this?
Well, the very simplest thing to do would be to give each one a unique identity in the form of a number. For example the green device could be called '1', the orange '2' and the blue '3'. Then they could swap information by attaching the correct address to each piece of information being exchanged.
Giving each device an identity is fine in theory, but in practice it has to be a bit more complicated. Because
The numbering scheme has to be 'computer friendly'
The scheme has to handle a vast amount of devices
The scheme has to deal with more than one network
In terms of being 'computer friendly', the numbering scheme should be based on binary numbers, as that is what computers are designed to use. So an addressing scheme called 'IP' or 'Internet Protocol' was agreed upon, more that thirty years ago

15. Internet Protocol or IP
The Internet Protocol was designed to allow devices to exchange data over a network.
The word 'device' is used because they do not have to be computers. For example a factory may have dozens of digital controllers on the assembly line wanting to swap information. They can use IP for this.
The most dominant version of IP is called 'version 4' or IP v4.
Each address is made up of a 32 bit binary number like this:
A bit of maths will tell you that 232 devices can be identified
with this scheme or roughly four thousand million devices.
The 32 bit number is grouped into four 8 bit numbers like this:
- Converted into its decimal equivalent
- Then put a dot between each group to help keep them apart visually
This is still a 32 bit binary number held within the device, but network applications always present it in this form.
Networks and IP
A 32 bit number can identify four thousand million devices. But of course there isn't just one massive network across the planet - they are split into millions of smaller networks.
So the IP number is split into having two roles.
The first three numbers typically identify the network itself. Then the last number identifies the device within that network :
A Subnet mask is a 32-bit number that masks an IP address, and divides the IP address into network address and host address. Subnet Mask is made by setting network bits to all "1"s and setting host bits to all "0"s.
= 255 so subnet mask would equal where 255 denotes the network and 0 denotes the device. (1 byte of nodes
If you needed more devices a subnet might be which would give you 2 bytes of nodes.

16. Default Gateway
A default gateway serves as an access point or IP router that a networked computer uses to send information to a computer in another network or the internet. Default simply means that this gateway is used by default, unless an application specifies another gateway.
Diagrammatical Representation of a Network
A network diagram is a visual representation of a computer or telecommunications network. It shows the components that make up a network and how they interact, including routers, devices, hubs, firewalls, etc. Symbols represent the different components, for example: