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FAQ At Sion Computers, we've done our best to create a Web site that anticipates and satisfies our customers' needs. With that goal in mind, we've compiled a list of frequently asked questions. If you do not find an answer to your question here, contact us at 0845 8695516 or info@sioncomputers.com.
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Program Updates E-Mails Backup Downloading And Installing Programs Wireless
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What are you doing here? You are profiling this person and then deciding what to do based on that profile. It’s your responsibility to be concerned about who enters your living space. Further, if you have children, you’ve probably also taught them how to deal with strangers who come to your door. Anti-virus programs work much the same way. These programs look at the contents of each file, searching for specific patterns that match a profile – called a virus signature – of something known to be harmful. For each file that matches a signature, the anti-virus program typically provides several options on how to respond, such as removing the offending patterns or destroying the file. To understand how anti-virus programs work, think about scam artists – people who visit your home to try to get you to buy a phony product or service, or to let them in. Once inside, they may try to steal your valuables or try to harm you in some way. There are a variety of ways you might find out about a specific scam artist lurking in your neighborhood. Perhaps you see a television report or read a newspaper article about them. They might include pictures and excerpts of the story the scam artist uses to scam their victims. The news report gives you a profile of someone you need to be on the lookout for. You watch for that person until either the story fades away or you hear that they’ve been caught. Anti-virus programs work much the same way. When the anti-virus program vendors learn about a new virus, they provide an updated set of virus signatures that include that new one. Through features provided by the updated anti-virus program, your home computer also automatically learns of this new virus and begins checking each file for it, along with checking for all the older viruses. However, unlike scam artists, viruses never completely fade away. Their signatures remain part of the master version of all virus signatures. Suppose a scam artist was at your front door. What would you do? Perhaps you’d not encourage them to come in nor buy their product but, at the same time, you’d try not to upset them. You’d politely listen to their story and then send them on their way. After you closed the door, you may call the police or the telephone number given in the report that initially brought them to your attention. With viruses, you often have the chance to react to them when they’ve been discovered on your home computer. Depending upon the specific characteristics of the virus, you might be able to clean the infected file. Or you might be forced to destroy the file and load a new copy from your backups or original distribution media. Your options depend upon your choice of anti-virus program and the virus that’s been detected. In your living space, you look at those who come to your door and you look at what you receive in the mail. These are two of the ways that items can get into your living space, so you examine them, sometimes closely, sometimes not. Viruses can reach your computer in many ways, through floppy disks, CD-ROMs, email, web sites, and downloaded files. All need to be checked for viruses each time you use them. In other words, when you insert a floppy disk into the drive, check it for viruses. When you receive email, check it for viruses. When you download a file from the Internet, check it for viruses before using it. Your anti-virus program may let you specify all of these as places to check for viruses each time you operate on them. Your anti-virus program may also do this automatically. All you need to do is to open or run the file to cause it to be checked. Just as you walk around your living space to see if everything is OK, you also need to “walk” around your home computer to see if there are any viruses lurking about. Most anti-virus programs let you schedule periodic exams of all files on your home computer on a regular basis, daily for example. If you leave your computer turned on over night, think about scheduling a full-system review during that time. Some anti-virus programs have more advanced features that extend their recognition capabilities beyond virus signatures. Sometimes a file won’t match any of the known signatures, but it may have some of the characteristics of a virus. This is comparable to getting that “there’s something not quite right here, so I’m not going to let them in” feeling as you greet someone at your door. These heuristic tests, as they’re called, help you to keep up with new viruses that aren’t yet defined in your list of virus signatures. An anti-virus program is frequently an add-on to your home computer, though your newly purchased computer might include a trial version. At some point, say after 60 days, you must purchase it to continue using it. To decide whether to make that purchase or to look elsewhere, use these steps for evaluating anti-virus programs:
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What do you do when a software “appliance” – a program – or the operating system itself breaks? How do you restore the functions that they provide? Do you know whom to call or even where to look to determine what to do next? Most vendors provide patches that are supposed to fix bugs in their products. Frequently these patches do what they’re supposed to do. However, sometimes a patch fixes one problem but causes another. For example, did you ever have a repairperson fix an appliance but in the process, they scratched the floor or damaged a countertop during their visit? For a computer, the repair cycle might have to be repeated until a patch completely fixes a problem. Vendors often provide free patches on their web sites. When you purchase programs, it’s a good idea to see if and how the vendor supplies patches, and if and how they provide a way to ask questions about their products. Just as appliance vendors often sell extended warranties for their products, some software vendors may also sell support for theirs. Have you ever received a recall notice for your car or another product you’ve purchased? Vendors send these notices to product owners when a safety-related problem has been discovered. Registering your purchase through the warranty card gives the vendor the information they need to contact you if there is a recall. Program vendors also provide a recall-like service. You can receive patch notices through email by subscribing to mailing lists operated by the programs’ vendors. Through this type of service, you can learn about problems with your computer even before you discover them and, hopefully, before intruders have the chance to exploit them. Consult the vendor’s web site to see how to get email notices about patches as soon as they’re available. Some vendors have gone beyond mailing lists. They provide programs bundled with their systems that automatically contact their web sites looking for patches specifically for your home computer. These automatic updates tell you when patches are available, download them, and even install them. You can tailor the update features to do only want you want, such as just telling you something new is waiting but doing nothing more. While the patching process is getting easier, even to the point where it can be completely automated, it is not yet foolproof. In some cases, installing a patch can cause another seemingly unrelated program to break. The challenge is to do as much homework as you can to learn what a patch is supposed to do and what problems it might cause once you’ve installed it. This is a hard job. Often, the vendors don’t tell you about problems their patches can cause. Why? Because it is simply impossible to test all possible programs with all possible patches to discover unexpected side effects. Imagine doing that job and then continuing to do that for each new program and patch that comes along. Vendors rely on their customers to tell them when something unexpected happens once a patch is installed. So, if this happens to you, let them know. Imagine then that you’ve either found a patch on the vendor’s site or you’ve received notice that a patch is available. What do you do next? Follow the steps below to evaluate a patch before you install it:
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These unsolicited items are sent to unsuspecting recipients. They may contain a return address, a provocative envelope, or something else that encourages its receiver to open it. This technique is called social engineering. Because we are trusting and curious, social engineering is often effective. In the case of the Anthrax letters addressed to United States senators, the envelopes contained a school’s return address as an inducement to open them. What government official wouldn’t want to serve their constituency by reading and responding to a letter supposedly sent by a class at a school, especially an elementary school? By opening the letter and subsequently spreading its lethal contents, the recipient complied with the wishes of the sender, a key foundation of social engineering. In the pre-Anthrax letter days, a mail handler might have given little thought to the contents of the letter or the validity of the return address. Those days are behind us. You probably receive lots of mail each day, much of it unsolicited and containing unfamiliar but plausible return addresses. Some of this mail uses social engineering to tell you of a contest that you may have won or the details of a product that you might like. The sender is trying to encourage you to open the letter, read its contents, and interact with them in some way that is financially beneficial – to them. Even today, many of us open letters to learn what we’ve won or what fantastic deal awaits us. Since there are few consequences, there’s no harm in opening them. Email-borne viruses and worms operate much the same way, except there are consequences, sometimes significant ones. Malicious email often contains a return address of someone we know and often has a provocative Subject line. This is social engineering at its finest – something we want to read from someone we know. Email viruses and worms are fairly common. If you’ve not received one, chances are you will. Here are steps you can use to help you decide what to do with every email message with an attachment that you receive. You should only read a message that passes all of these tests.
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On your home computer, have you similarly divided everything into the same categories? What have you done about the items – files in this case – that you can’t replace? Examples are the files that make up your checking account records, that novel you’ve been writing for the past few years, and those pictures you took last summer with your digital camera. What happens if your computer malfunctions or is destroyed by a successful attacker? Are those files gone forever? Now think about your car for a moment. Do you have a spare tire? Is it inflated? When was the last time you used it? Can you imagine buying a car without a spare tire? Even if you bought a used car without a spare, how soon did you buy a spare so that you’d have one when you needed it? Think back to your home computer. Do you have a “spare tire,” meaning a way to continue computing when you have a “blowout” caused by a malfunction or an intruder? Said another way, can you back up your files onto some other media so that you can recover them if you need to? If you’d never buy a car without a spare tire, why did you buy a computer without a device to back up your files? When deciding what to do about backing up files on your computer, ask these questions:
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Unfortunately, the Internet is not the same. There are neither standards nor many certification organizations. Anyone who writes a program can distribute it through any means available, such as through the web or by sending you a copy. Speaking of that, have you ever received a CD-ROM in the mail? How do you know that it contains what the label says? The answer is: you don’t know. More importantly, it’s difficult to know. No matter how you acquire a program, it runs on your computer at the mercy of the program’s author. Anything, any operation, any task that you can do, this program can also do. If you’re allowed to remove any file, the program can too. If you can send email, the program can too. If you can install or remove a program, the program can too. Anything you can do, the intruder can do also, through the program you’ve just installed and run. Sometimes there’s no explanation of what a program is supposed to do or what it actually does. There may be no user’s guide. There may be no way to contact the author. You’re on your own, trying to weigh a program’s benefits against the risk of the harm that it might cause. What’s the problem you’re trying to solve here? You are trying to determine if the program you’ve just found satisfies your needs (say it provides a service that you want or you’re just experimenting) without causing harm to your computer and ultimately the information you have on the computer. How do you decide if a program is what it says it is? How do you gauge the risk to you and your computer by running this program? You address these same risk issues when you purchase an appliance; you may just not have realized that’s what you were doing. When you make that purchase, you buy from either a local store you know or a national chain with an established reputation. If there’s a problem with your purchase, you can take it back to the store and exchange it or get your money back. If it causes you harm, you can seek relief through the legal system. The reputation of the merchant, the refund/return policy, and the availability of the legal system reduce your risk to a point where you make the purchase. Apply these same practices when you buy a program. You should
So then, how do you decide if a program is worth it? To decide if you should install and run a program on your home computer, follow these steps:
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You've seen the adverts on the telly of a Centrino notebook working on the top of Mount Everest? So now you think that WiFi works brilliantly and you can just switch your notebook on anywhere you like and pick up a fantastically clean and powerful signal. WRONG! In fact I'm amazed that trading standards haven't been on to Intel for such misleading adverts. The Background So let's set some background ground facts down for a start: Now this might come as a shock but 2.4GHz WiFi does NOT go through brick walls or concrete. It MIGHT go through plasterboard but not if the plasterboard is foil backed; often builders use foil backed plaster board on both walls and ceilings to help meet modern building regs concerning heat insulation and fire regs. The signal WILL go through wood (e.g. floorboards) but it is weakened quite a lot in doing so. 2.4GHz will also go though a window but if it's K glass double glazing (as installed according to building regs. for the last 5 years) then the metal vapour of the K coating will knock the signal strength down by at least 30%. WiFi's good ain't it! Therefore, if you want to get a wireless signal from the lounge to the upstairs bedroom then it has to bounce around the lounge to get through the door, ricochet down the hallway, up the stairs and into the bedroom. The problem then is you don't know if or how the signal will bounce or reflect so you don't know if the signal will ever reach the bedroom. At each reflection the signal strength is reduced and also there might be more than one route to the room upstairs (because the signal might reflect a different way to get to the room upstairs). Because the signal might go by multiple routes then the signals from each route arrive at slightly different times. This is called multi-path effects and causes many problems when the radio device tries to extract the data from the signal. It's like trying to hear someone talking to you in a nightclub with the music blaring in your face i.e. the signal is strong but garbled. The net effect is that the signal has a very good chance of not reaching the destination or being of a very poor quality when it does so the link ends up running at a slow speed. Next, an antenna doesn't magically create extra signal out of thin air! All it does is take your existing signal and concentrate it into a specific direction. A standard low gain (2db) antenna fitted to an access point or wireless LAN card sends out a signal in a roughly spherical pattern with a small dimple at the top and bottom. A so-called high gain omni antenna takes your existing spherical signal and flatterns it into more of a doughnut shape so it sends more signal out horizontally. Now, if the signal was getting from downstairs to upstairs by going through the floors (although not very well) then going to an antenna which sends more of the signal out horizontally might make things worse! Then there's the common myth that 11g (54meg, sometimes called 54g) is better than 11b. WRONG! There are two problems with 11g Usually 11g equipment outputs a lower signal strength than 11b 11g radio devices have a considerably lower signal sensitivity at the higher speeds and, let's face it, if you aren't going to use the higher speeds then why bother paying for 54meg in the first place? e.g these are the power output and receiver sensitivity figures for a good make 54G access point.
Now get confused by all these dBm and things Let's look at the transmit power first of all. A high dBm figure means more power. 11meg is 21dBm and 54meg is 16dBm i.e. 5dBm less. In real terms 6dB would half the transmitter distance so 5dB less power is nearly halfing the transmission range at 54 meg. Now, let's look at the signal sensitivity. A more negative figure is better (it's a figure for how well a device can suck a signal in). 11meg is -86dBm and 54meg is -72dBm i.e. a difference of 14dB. Remember every 6dB halfs the range so 14dB is going to knock the range down by a factor of at least 4. So we have half the range due to output power and then a quarter of that due to bad sensitivity. That's one eigth of the range at 54meg compaired to 11meg i.e. the effective range has dropped by nearly 90% when you try to run at 54meg! A typical user question So now we've got the groundwork out of the way let's look at a typical user question: Typical question: "I am using a L*****s XYZ54 access point on the ground floor but the signal to my PC's on the first floor is not 100% reliable. I was wondering which antenna would be best for improving this signal? Also, my XYZ54 access point has two antenna sockets; should I connect an antenna to both sockets or only one?". Looking at the first part of the question ".which antenna would be best for improving this signal.". From above you can see this is a hard one. If the signal is getting upstairs by going through the floorboards then a high gain omni antenna might make things worse by sending less signal upwards. However, if the signal is getting to your PC's by bouncing along the hallways and stairs then sending a stronger signal horizontally might make things better. You really don't know The first thing to consider is, if your are using 11g (54meg) then do you really need 54meg? If it's just distributing your ADSL broadband then remember that ADSL normally goes at only half a meg or sometimes at one or even two meg. So an 11meg wireless connection is many times faster than your broadband - 54g is going to make no difference to your internet access. Next think about the location of the AP (Access Point). Can you arrange to place it better in the building so it's closer to the PC's? Of course you don't know how the signal is getting from the AP to the PC's so you might have to try several different spots around the building to see if you get an improvement. Now look at the antenna on the PC; don't just consider the AP antenna. Normally the PC antenna is the weak link. If it's a PCMCIA card in a notebook with a built in antenna then the antenna in the card is probably just a track on a circuit board - not the best antenna on the block! A PCMCIA card with a 'proper' 'stick up in the air' antenna will be a lot better. USB devices are sometimes better than PCMCIA because the USB device is on a cable which gets it away from the notebook. If the notebook is a Centrino type with a built in antenna then there's not much you can do about it. Try orientating the notebook in a different way. You might even have to try disabling the built in wireless and using a different radio device (PCMCIA or USB). If the PC is a desktop with a PCI card then often the antenna for the PCI card is right at the back of the PC shielded by the metal case of the PC. A small (5db) antenna on a short extension lead which enables you to position the antenna on top of the PC is good thing to consider. It's not advisable to fit an extension lead to the existing antenna because you will loose too much gain in the extension cable. Next you could try simply upping your existing antenna a little bit in gain. If you go too high on the gain then you might make things worse. Remember a high gain antenna takes your existing signal and concentrates it to point in a specific direction. So going for too high a gain means you might have problems on where to point the antenna to make it work. Also, if you are trying to pickup the signal in several points in the building then you might end up improving things for one position but making it worse for the rest. So, if your device is the industry standard 2db little 'rubber-duck' antenna try changing them for 5db 'rubber-duck' antenna. See if that works. If this doesn't work then you might consider going for an 8db omni but now you are starting to get pretty directional on your antenna, so you run a high risk of making things much worse rather than much better. If you are just trying to improve things on the same floor as the AP then normally higher gain omni antenna are a fairly safe bet (because you aren't trying to throw any signal up or down). I wouldn't normally advise using directional antenna to sort this problem, especially if you have PC's scattered all around the place. If the area is just a large open plan office or warehouse then high gain omni antenna are a good bet. Even better consider a 'corner' style antenna. This fits in a corner (hence the name) and sends the signal out at 90 degrees covering the whole room. Now, the second part of the question: ".my XYZ54 access point has two antenna sockets; should I connect an antenna to both sockets or only one?" The simple answer is connecting to both sockets but I'll explain why. If a radio device has two antennas then this is because it runs in diversity mode. With diversity mode, for reception, the radio device uses the particular antenna that gives the best signal. Because the wavelength of 2.4GHz WiFi is very short (about 12.5cm) then the signal strength can vary quite a lot over a space of just a few inches. This is the theory with diversity antenna setup. But what about transmission with diversity? Well, with most diversity setups the radio device will transmit on only one of the two antennas. It doesn't matter which antenna was used to receive the signal it only transmites back on the one specific antenna. In this case you could use just one high gain antenna but you must pick the antenna connection that does the transmitting as well as receiving. If you pick the wrong antenna socket then you end up still sending out a weak signal. Using two antennas means you stand a better chance of picking the correct antenna connection. Now, some high-end WiFi devices use a different form of diversity. With these devices the transmittion happens on the same antenna that was used to receive the signal. The theory goes if antenna socket A was best to receive the signal from the other party then probably the same antenna is best for sending the stuff back. With this setup then you could still use one antenna because the radio device will automatically decide which antenna is best for receiving and transmittion. In effect the device ends up only using one of the antenna and your diversity advantages aren't used. Using two antennas though gives back full diversity operation. That covers the important aspects of distributing WiFi around your home/building now let's think about some of the less common systems. Repeaters and WDS What about repeaters? A WiFi repeater is supposed to take in the WiFi signal from a remote radio device and then blast it out again locally. So it would be nice to think you could put a WiFi repeater up on the first floor. It will then pickup the signal from downstairs and then broadcast it as a strong signal on the first floor. Sounds good but there are some problems (aren't there always). First of all, our own experience shows that radio devices don't seem to like repeating from other make/models of devices. Secondly, the repeater must be able to get a good, reliable, stable signal from the radio first device. If it can't then it ends up repeating rubbish or even worse just slows the whole lot down with repeated resend messages. Thirdly, each time the signal is repeated it slows the network down. If you want to use repeaters then the best solution is to go for WDS (Wireless Distribution System). With a WDS system then you can use multiple repeaters and each repeater can talk to any other repeater and decides which repeater it needs to talk to in order to reach the destination. You still have the problems mentioned above but WDS is more resilient because it can dynamically reroute it's traffic to use different radio devices. So if the reception to/from one repeater deteriorates then the system adjusts and starts sending traffic via a different route (assuming of course that you have enough WDS repeaters placed around to give the option of alternative routes). WDS is probably not worth thinking about in a home setup but in a business with a multi-story building and offices scattered all around WDS is the best system for distributing using WiFi. What's the answer then? Well the best answer is to dump wireless and run proper CAT5 LAN cables around the building. Obviously though this won't be either feasible or desirable in many cases; though, if you just want to get a LAN connection to a single back office then running a LAN CAT5 cable around the outside (not inside) of the house will normally turn out to be the cheapest and most reliable method. Another option is to consider going half and half, use CAT5 cables where you can (i.e. where they are easy to run and don't upset your significant other) and using wireless where you have to. For example, you could have an AP in the lounge downstairs to cover that area and possibly the room next door. Then run a CAT5 cable around the outside of the house up to the first floor to a second AP running on a different radio channel. Hopefully you can position the second AP to give adequate coverage for your devices upstairs.
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