Topic 1: Networks

Types of Networks avaliable

• https://www.youtube.com/watch?v=uliny6fWbvs (Einbetten)

Peer to Peer Networks

• 
• All the computers have the same status and are able to communicate with each other on equal footing. All computers on this network have access to all the resources of any other computer.

Advantages and Disadvantages of P2P

• Advantages
• Cost saving - no server is needed as all the computers are the same
• No network manager is needed - all users are responsible for the network
• Easy to set up - simple computer networks, set up by anyone
• No reliance on the server - no worry about server breaking down
• Low operating costs - less set up and maintenance costs
• Disadvantages
• Back ups can't be made centrally
• Users will need ICT knowledge as they're responsible for their own files on their computer
• Poorer security - resources are shared
• Some computers may run slowly
• Users may find difficulties finding files are they're not organised or held centrally
• Only suitable for small networks

Client-server Network

• https://www.youtube.com/watch?v=mm3r8EG4wLQ (Einbetten)
• Preferred choice for large networks. All computers do not have the same status. Usually a more powerful computer is the central computer where all the files and programs are stored, this is known as the server. The other computers are known as clients.
• A network manager is usually in charge of the server.

+ and - of client server network

• Advantages
• Security is better - because it is centralised a person has responsibility
• Centralised data - data is held at the file server which means all users have access to the same set of data
• Back ups are taken centrally - data and programs are unlikely to be lost
• Faster access to programs and files - servers are used which are powerful computers
• Centralised administration
• Disadvantages
• More expensive
• Need specialist knowledge - need a network manager who understands technicalities
• Software is sophisticated and expensive
• If the server breaks down the network is unusable until its repaired

Ring Topology

• Is also used on peer-to-peer networks as there is no server.
• All the computers are arranged in a circle.
• What happens with a ring topology?
• Data sent by one computer is passed around the ring until it reaches the correct computer.
• Advantages of ring networks:
• The network is not dependent on a central computer.
• Each computer has the same access as no one computer can be the 'hog'.
• Disadvantages of ring network:
• If there is a break in connection then the whole network fails.
• Faults are difficult to locate.
• Impossible to keep the network running whilst equipment is added or removed because there is only one path of data.
• https://www.youtube.com/watch?v=P1R6xWFEq3A (Einbetten)

Bus Topology

• All the devices connected to the network are connected to a common shared cable called the backbone. Signals are passed in either direction along the backbone.
• Advantages of bus topology networks:
• Cost effective because of the small amount of cable needed.
• Simple cable runs makes it easy to install.
• Easy to add extra devices to the network.
• Disadvantages of bus topology:
• The more devices the more degraded the networks performance.
• If there is a break in the backbone then the entire network cannot be used.
• https://www.youtube.com/watch?v=ySd-k7i7G5k (Einbetten)

Star Topology

• The star topology uses a central point to connect all the devices on the network. The central connection point can be a hub, a switch or a router.
• Advantages of star topography:
• Fault tolerant - if one cable fails then the other computers can still be used.
• Load tolerant - extra computers can be added without much loss in performance because all computers have their own path to the hub.
• Easy to add extra computers - extra computers can be added without disturbing the network.
• Disadvantages of star topology networks:
• Higher cost - the large amount of cabling needed makes it more expensive.
• Dependent on the central hub, switch or router - if the device at the centre of the network fails the whole network fails.
• https://www.youtube.com/watch?v=_9s_7RaopVg (Einbetten)

Wireless networking

• With wireless communication the data transfers through the air by radio waves. There are many public areas where the internet can be accessed using a person's laptop computer or other portable devices like a mobile phone. These places are known as hotspots. To set up small Wi-Fi network you would beed
• A broadband connection to internet.
• A router.
• WiFi enabled computer.
• How Wi-Fi works
• 1. Router is connected to the internet by a high speed broadband connection.
• 2. The router receives data from the internet.
• 3. Transmits data from the internet.
• 4. Computers wireless adapter picks up the signal and turns the radio signal into data so the computer can understand.
• https://www.youtube.com/watch?v=xmabFJUKMdg (Einbetten)

+ and - of wireless networks

• Advantages:
• Allows expensive LANS to be set up without cables.
• Allows people freedom of working anywhere a signal can be received.
• Ideal for networks in old listed buildings as cables can not be installed.
• Global set of standards - you can use it all over the world.
• Disadvantages:
• Power consumption is high - which means laptops soon exhaust their rechargeable batteries.
• May be health problems.
• May be security issues even when encrypted.
• Home networks may have limited range.
• Can get interference if wireless network signals overlap.

Network management software

• What network management does:
• Making sure all computers have up to date software with latest security.
• Keeping track of the software being run on each computer and checking that there are licenses.
• Providing remote control facilities that help desk staff can sort a user's computer without actually seeing the users screen.
• Bandwidth is used correctly.
• Checking speed of the processor and the memory used for computers. Useful for seeing upgrades.

Network Operating Systems Software

• Small networks can run off existing Windows software, but larger client server networks specialist network operating software is needed.
• Network operating systems are complex as they need to coordinate activities of all computers and devices on the network.
• Examples of network operating systems are:
• UNIX
• Linux
• Novell Netware

User accounts and user logs

• These are important as they prevent misuse of the network by users. If it does occur it is easy to find the culprit.
• User accounts:
• When accounts are created the network administrator/manager they allocate the users rights. They control which software the user can access, which shared files the user has access to, if the user can copy files and if the user can install software.
• User logs:
• The login procedure can provide an audit trail as to who has used what resources on the system. This is done by providing a user log, which is a record of the successful and failed logins also the resources used by the users.

Security strategies

• Security methods:
• Use of passwords and user-IDs
• Virus checkers - scans files, e-mails and instant messages for viruses
• Firewalls - software, hardware or both to protect hackers
• Encryption - keeps data secret when being sent over networks, e.g. finance

Configuration management

• When a network has been created it is necessary to configure it to maximise its performance. Network configuration management is the process of organising and maintaining all the information about a network. Network configuration management is the process of organising and maintaining all the information about a network.
• When a network needs modification, repair, expansion or upgrading the network manager/administrator will refer to the network configuration database to determine the best course of action. The network configuration database contains the locations and network addresses of all hardware devices used in the network and also information about the programs, versions and updates of the software installed on the network computers.
• Advantages of configuration management:
• It is much easier to repair, expand and upgrade network.
• The network will be optimised and will run faster.
• Less network downtime owing to better management.
• Possible to roll back changes to a previous configuration if changes made to a network adversely affect its performance.
• Keeps records of all the changes made to a network so you do not need to write down the new settings.

Remote management

• The tasks that the person can do in charge of management at their terminal:
• See which users are using network.
• Check on e-mails being sent in company time.
• Check internet sites that users have used.
• Check on the hardware to see if upgrades are needed.
• Check to make sure that the number of allowed users as per the licenses for software are not being exceeded.
• Guide users through problems they may be having.
• Make sure users do not have any unauthorised software loaded on their computer.
• Log a user off if they have left themselves logged on.
• See if components on the network are failing.
• Shut down stations on the network are failing.
• Shut down stations that are not functioning correctly.
• Rebuild stations by adding software.

Disaster planning - backup and restoration

• Companies have to deal with lost hardware, software, data or communication. This can be caused by:
• Hardware failures.
• Software bugs.
• Natural disasters.
• Deliberate damage.
• Accidental damage
• Disaster planning is needed:
• Minimise disruption.
• Get systems working ASAP.
• Ensure staff how to recover data and programs.

Back ups

• Loss of programs and hardware isn't that much of an issues as they can be replaced. If there is no back up on data it cannot easily be replaced.
• Back ups should be:
• Taken on regular and routine basis or even automatically.
• Kept in a fireproof safe or preferably kept off site.
• Taken using the grandfather, father and son principles in the case of batch processing systems.
• Used with RAID system.

Restorations

• There is no point backing up copies of files and not checking that the original files can be recovered using the backup. It is important that staff understand what they need to do recover the lost or damaged data. Occasionally, organisations should do a mock of a disaster recovery to check it actually works.
• Restoration can be done on a smaller level. E,g, if a computer crashes the existing copy may become corrupted.It is possible to re-create files that have been deleted by accident.

Auditing (keeping logs)

• Auditing keeps records of:
• Usernames.
• Times they have logged on and off.
• Details of programs they used.
• Details of files accessed.
• Details of changes.
• Auditing is used to identify abuses of the systems by authorised staff and also to investigate instances of unauthorised access like hackers.