1. Network Diagrams

2. Learning Objectives Identify different network topologies
Identify typical networking hardware devices
Explain the advantages and disadvantages of different network topologies
Explain the difference between Client Server and Peer-to-Peer network models
Analyse real-world scenarios to establish network hardware requirements
Analyse real-world scenarios to establish network software requirements

3. Pre-Reading Recap Network Topologies Network Software Network Hardware
Star
Bus
Ring
Network Software
Firewalls
Anti Virus
Spyware
Anti Malware
Network Hardware
Workstations
Mobile Workstations
Tablet Computers
Mobile Phones
Hub
Switch
Router
File Server
Server

4. Pre-Reading Recap What are the advantages of the Bus network?
What are the disadvantages of the Bus network?
What are the advantages of the Ring network?
What are the disadvantages of the Ring network?
What are the advantages of the Star network?
What are the disadvantages of the Star network?
Why would an organisation choose to use a Star network instead of a Bus or Ring?
What does a Firewall do?
What does Anti Virus do?
What does Spyware do?
What is the purpose of Anti Malware software?

5. Networks
A network is simply a collection of computers and equipment connected together.
The allow people to share files and resources
There are two main types of network
(LAN) Local Area Network
(WAN) Wide Area Network

6. LAN – Local Area Networks
A local area network (LAN) is defines as a collection of computers and peripheral devices (such as printers) connected together within a single site.
A site is not restricted to one building!
At school our network is classed as a LAN. It connects together all computers, printers and servers in multiple buildings.

7. WAN – Wide Area Networks
A WAN is a network, in which the computers systems are all located relatively distant from each other, for example, in different buildings all over the country or in different countries.
The Internet is an example of a WAN.
You will note that many LANs could be linked using a WAN.

8. Benefits of Networks: Communication
Using to communicate with colleagues
Using messaging systems to chat while you are working on other things
Transferring files between computers

9. Benefits of Networks: Sharing Resources
Sharing folders so that you can access files anywhere on the network from any computer and different people can access these files as needed
Sharing peripheral devices such as printers and scanners
Sharing an internet connection

10. Benefits of Networks: Centralised Management
User profiles and security can all be managed centrally
Software can be distributed across the network rather than having to install it on each individual computer
Users can use any PC on the network but still see their own files.

11. Disadvantages A network manager may need to be employed – expensive
Security problems – files sent between computers could spread a virus
Hackers can gain access to data more easily
If the server is down, all workstations on the network are affected
Initial cost of servers, communication devices, etc. can be expensive

12. Graded Exercises
Complete Questions 1-3 of the Pass grade questions

13. What is a topology?
A topology is a description/diagram of how computers can be laid out and connected. There are only three basic topologies that are used but these can be combined in a large network

14. Bus Network
Computers are connected to a single backbone cable. The computers all share this one cable to transmit to each other and only one computer can transmit at a time.
This is fine if most of the time the network is not too busy. It can be very slow with lots of computers trying to transmit at the same time.

15. Bus Network Advantages Disadvantages
Easy to implement and add more computer systems to the network
Quick to set up – well suited for temporary networks
Cost-effective – less cabling
It is difficult to troubleshoot the bus
Limited cable length and number of stations – performance degrades as additional computers are added
If there is a problem with the main cable or connection, the entire network goes down
Low security – all computers on the bus can see all data transmissions
Proper termination is required
Data collisions are more likely, which causes the network to slow down. A collision is when two computers try to send a packet at the same time

16. Ring Network
Computers are connected to adjacent computers in a ring. Computers take turns in transmitting data. This is controlled by a token around the ring. Computers can only transmit when they have the token.

17. Ring Network Advantages Disadvantages
Data is quickly transferred without a bottleneck – consistent data transfer speeds
The transmission of data is relatively simple as packets travel in one direction only
Adding additional nodes has very little impact on bandwidth
It prevents network collisions.
If any of the computer systems fail, the ring is broken and data cannot be transmitted efficiently
If there is a problem with the main cable or connection, the entire network goes down
It is difficult to troubleshoot the ring
Because all nodes are wired together, to add a another you must temporarily shut down the network

18. Star Network
All of the computers have their own cable that connects them to a central computer. The central computer controls the network.
The central computer is usually a server, where resources are stored.

19. Star Network Advantages Disadvantages
Good performance/fast network speed
Easy to set up
Possible to add more computer systems without taking the network down
Any non-centralised failure will have very little effect on the network
Minimal network collisions
Better security
Expensive to install – more cabling required
Extra hardware required, such as a hub

20. Topologies in use.
In most offices and classrooms the Star topology is used.
The room might look like a bus network but in fact all of the computers have their own cable connected to one device.

21. Mixed topologies Most network use a mix of the three topologies
The most common are star and bus.

22. Graded Exercises
Complete Questions 4-7 of the Pass grade questions

23. Connectivity
To connect a computer system to a network, a Network Interface Card (NIC) is required. A physical hardware port allowing a cable to connect your computer system to the network provides one method of connection.
The second method is to connect a computer system using a wireless connection, called a Wi-Fi.

24. Network Interface Card
Each computer must have way to connect to the LAN. This is done via a Network card. The correct term for a network card is
Network Interface Card or NIC for short

25. WiFi Connectivity
Computers can make a wireless connection if they have a wireless NIC.
A wireless router provides a connection with the physical network.
A computer device needs to be within range of the router to get access.
A wireless connection uses radio signals to send data across networks.
The wireless adapter converts the data into a radio signal and the wireless receiver decodes it so that the computer can understand it.

26. Graded Exercises
Complete questions 8-9 of the Pass grade Questions

27. Client-Server Network
The server is a powerful computer which provides services required by any of the clients
Client computers are those which people use to log on to and use the services provided by the server
Client
Query
Response
Search
Data
Server

28. Servers on LANs and WANs
One or more servers may be part of a local area network
A server may also be part of a wide area network
Google has massive servers in several different countries

29. A Google server room in Council Bluffs, Iowa
Photo: Google/Connie Zhou
See more images of Google data centres

30. A server can be part of a LAN

31. Serving all your needs
In a school network, there may be dozens or even hundreds of clients and several servers
A file server holds all the data files and databases and manages backups
A print server may organise printing on different printers
An server may receive s, detect and block spam, distribute s to users
A web server may host the school’s external website

32. Role of the server The server waits for requests from the clients
It may need to pass the request (e.g. for a web page) to another server – in which case, it becomes the “client”

33. Role of the client The client sends requests to the server
Waits for a reply
Receives the reply

34. The “handshaking” process
This is the process by which two devices initiate communication
One device sends a message to another indicating it wants to communicate
If two devices try to transmit simultaneously, both wait a random time and then try again
The “handshaking” negotiation then takes place to establish what protocol to use
Computer A: “I am ready to receive data”
Computer B: “I am ready to send data”
Computer A: “OK, send it!”

35. Types of server
Servers are often dedicated computers, meaning each one performs no other tasks beside its server tasks
However, on a multiprocessing operating system, a single computer can perform the tasks of several servers

36. Advantages of client server networking
All data can be backed up centrally rather than on each individual computer
Security is better because data is held in one location rather than all over the organisation
Users can log in from any computer on the network and access their data

37. Peer-to-Peer (P2P) Networks
An alternative to a client-server network
There is no central server. Each computer holds its own applications and data
All computers have equal status

38. Advantages of a peer-to-peer network
Easier to set up – computers can simply be cabled together
No special software is required to run the network
Individual computers can share a printer, router, modem and other hardware
Users can communicate directly with each other and share each others’ files
Where would you use a peer-to-peer network?
What are the disadvantages?

39. Drawbacks of a peer-to-peer network
Viruses and malware are easily transferred over this type of network
Data recovery and backup is not done centrally, so each computer has to have its own backup system
Files are not centrally organised, but stored on individual computers and may be hard to locate if the computer’s owner does not have a logical filing and naming system

40. Peer-to-peer on a WAN
The P2P configuration can also be used for file-sharing websites
BBC iPlayer, for example, uses P2P networking
This means that with thousands of people downloading, data can be passed between computers rather than just from the server
Peer-to-peer networks are often used for the illegal distribution of copyright material such as music and films, as they are very difficult to close down

41. Client server vs Peer-to-Peer
A central backing store is available to all computers
Storage facilities are distributed across all computers
Security is controlled by the central computer
Security is not centrally controlled
Backup is done centrally on the server
Backup must be done separately for each computer
All users are reliant on the central server
No central server
Can support hundreds or even thousands of users and grow with an organisation
Easy to set up but most suited to homes and small businesses

42. Graded Exercises
Complete questions of the Pass grade Questions

43. Network Hardware
Workstation (Desktop)
Workstation (laptop)
A workstation is a computer intended for individual use that is faster and more capable than a personal computer. It's intended for business or professional use (rather than home or recreational use).
A Desktop workstation is the same as a Desktop personal computer – it is less portable than a laptop! These are usually wired into a network.
A Laptop workstation tends to be wirelessly connected to a network – but these may be docked into a docking station to create a wired connection

44. Network Hardware
Tablet computers
Mobile phones
a small portable computer that accepts input directly on to its screen rather than via a keyboard or mouse
a telephone with access to a cellular radio system so it can be used over a wide area, without a physical connection to a network.

45. Network Hardware HUB Switch
A hub is a hardware device that connects multiple computers together in a network and allows them to share data packets.
Each computer will be connected to a single 'port' on the hub. So if you purchase an '8 port hub', you will be able to connect up to eight computers together.
When a data packet arrives at a hub port, it transmits it to every other port. Unlike a switch it does not examine data packets. Re-transmitting every packet to every port means that data collisions are more frequent than a switch. Network protocol can deal with collisions but it does have the effect of slowing down throughput when too many occur. Data security may also be an issue because every computer encounters every data packet, even if they were not the intended recipient.
A switch has a number of ports and it stores the addresses of all devices that are directly or indirectly connected to it on each port. 
As a data packet comes into the switch,  its destination address is examined and a direct connection is made between the two machines.
This added sophistication compared to a hub means that virtual networks can be set up where only a sub-set of connected computers can see each other. As far as these computers are concerned there are no other machines on the network.

46. Network Hardware
Router
Server
a networking device that forwards data packets between computer networks. Routers perform the "traffic directing" functions on the Internet. A data packet is typically forwarded from one router to another through the networks that constitute the internetwork until it reaches its destination node.
A Router remembers the routes that can be taken by a data packet and sends them along the ‘preferred line’ if this connection is not available it will send the packets using another route.
a computer or computer program which manages access to a centralized resource or service in a network.
For example:
Application
File

47. Graded Exercises
Complete Question 17 of the Pass Grade Exercises

48. Network Diagrams What is a network diagram?
A network diagram is a visual representation of network architecture. It maps out the structure of a network with a variety of different symbols and line connections. It is the ideal way to share the layout of a network because the visual presentation makes it easier for users to understand how items are connected.

49. Symbols Used in Network Diagrams

50. Network Diagrams - Activity
Complete the Merit and Distinction grade questions
Route to Distinction: When explaining your network diagrams your level of detail and technical terminology will be assessed. For distinction level you should be using technical terminology correctly and justifying your decisions on hardware, software, and topology.