Introduction
A networks is a complex system. To ensure that it runs smoothly and to ensure that everyone involved in running the network (the network manager and technicians, for example) know whose job it is to do what, a network will have a number of written policies in place. These will have been drawn up by the network manager, usually after consulting with everyone. They include Acceptable Use, Disaster Recovery, Back-up, Archiving and Failover policies.

Acceptable Use policy
People who need access to a network to do their job are usually asked to sign an agreement that they will only use it for legitimate reasons related to doing their job before they are allowed access. They also have to agree not to use it for illegal, unethical or for time-wasting activities, such as downloading copyrighted material, viewing pornography or spending time on social networking sites if it is not work-related. The agreement they have to sign is known as an Acceptable Use policy. This policy helps reassure an organisation, who is responsible for the network and what people are using it for. It also means that an organisation can reasonably sack someone who uses the network for anything other than work-related activities as the user was clearly informed in advance what the consequences would be.

Disaster Recovery policy
All networks might have a disaster. This could range from the entire building holding a network burning down to flood damage to malicious damage by a hacker or disgruntled employee. When a disaster happens, an organisation needs to get the network back up and running as quickly as possible or it might go out of business. A Disaster Recovery policy is a written document, which attempts to get the managers in an organisation to think in advance about what they need to do should a disaster happen. By thinking ahead and planning for the worst, companies will know what to do quickly and calmly in the event of a serious problem.

Back-Up policy
All data is at risk at all times. There are many reasons why this is so. A hacker or disgruntled employee may delete data, there could be a fire, data might get corrupted by software or an upgrade, a piece of equipment like a hard drive might fail, there might be an earthquake or other natural disaster, someone might steal a computer with data on and so on. To ensure that data can be recovered, it is backed-up regularly. However, a policy is written down to make it crystal clear;

• whose job it is to do the back-ups
• how often the back-ups will be made and when it will be done
• how each back-up is to be made
• how each back-up will be labelled
• where back-ups will be stored
• how the back-up system will be tested

Back-ups are usually done on a rolling basis. For example, in the first week of a four week back-up plan, an 'incremental back-up' might be made every night on a back-up tape called Monday1, Tuesday1, Wednesday1, and Thursday1. An incremental back-up resaves only those files that have changed since the last time a back-up was made. On the Friday, a 'full back-up' is made of the whole system' data on a tape called Friday1.

Then the above is repeated for the next week on tapes called Monday2, Tuesday2, Wednesday2, Thursday2 and Friday2, so you now have 10 tapes). The same is done for week three and week four (so you have 20 tapes now). Then at the start of the new four week period, the tapes are over-written and the whole process restarts.

The above policy might be fine for a small organisation. For larger ones, you would probably keep back-ups going back many months or even years. The reason why so many back-ups are made is that it might actually take a few weeks or months to detect that there was a problem with the back-up system. If you used just one tape and backed up a computer every day on that one tape, it would be a real problem if you discovered, for example, that the back-up device hadn't been working correctly for a few weeks or a back-up tape was faulty.

Archiving policy
Sometimes, you don't want to have certain files on your system anymore but you don't want to just delete them, or you are not allowed to legally. For example, when a year group leaves school to go to university or start a job, you don't need their details to be on a school's admin system anymore. If a company has finished doing its tax and accounting records for one year, they won't be needed again by the company, but they can't delete them in case the tax office wants to check them (companies have to keep tax records for seven years by law). Plane makers might have to refer to their records of components in a plane decades after a plane was built if there was a plane crash. They don't want the details of these components on their current system but they may possibly need them in the future.

Having old data on a system slows down searches, slows down back-up times and needs hard disk space. Data that is no longer currently required therefore is 'archived'. That means:

• The data is 'compressed' - squashed to make it as small as possible.
• It is copied to a storage device e.g. online storage or on a back-up tape.
• It is properly labelled with a date and details of the archive.
• If the back-up is a tape or similar, it is put in safe storage e.g. a fire safe or a safe in a bank, for example.
• The original data on the system is deleted.

Back-ups and archiving may seem similar but they are not. They are done for completely different purposes and in completely different ways.

Failover policy
Companies often have second devices in place for key pieces of equipment on a network, in case the first device fails. These are set up to start automatically if the first device fails. It means that the company doesn't have any 'down time' on the network. 'Down time' is when a company cannot use the network, even though it is critical to the running of the business. If the network was not working, even for a few hours, it might cost a company thousands or even millions of pounds. Typical pieces of equipment that are duplicated like this include servers and routers. Companies often produce a written policy called a Failover policy, which details what pieces of equipment will be duplicated, how they will be set up, what users can reasonably expect the down time to be and so on.

For example, a key piece of equipment on a network is the server. This controls the whole network and if it fails, the whole network will not be available for anyone to use. By providing a second server that will start automatically and is up-to-date with everyone's files, you can ensure that the network will carry on as if nothing has happened if the first server breaks down.

Q1. What is an ‘acceptable use policy’?
Q2. Why are disaster recovery plans necessary?
Q3. What might you typically find in a ‘back-up policy’?
Q4. Describe how data files might be archived?
Q5. Explain what ‘failover’ is.