The Best of the SQL Server Training Courses

 

Over the years, I've taught six different SQL Server training courses. The first two were designed to teach only SQL Server 2000. The next four were designed to teach SQL Server 2005 and SQL Server 2000 combined. I loved teaching these courses as they were real-world courses; however, I've never been as excited about a SQL Server course as I am the about the one I'm currently preparing for ASPE. This SQL Server course will focus on the topics that students have begged for over my seven years of teaching SQL Server.

In all of the other SQL Server training courses I've delivered, some tie has existed to a Microsoft certification. Not with this one. We've decided to give the attendees the topics they've asked for over the years. These topics include:

  • Installing SQL Server right the first time
  • Designing and implementing well-performing databases
  • Optimizing the performance of existing databases
  • Improving security
  • Understanding advanced features such as SSIS, SSRS and SSAS

Any many more topics as well. The training will be focused on SQL Server 2005 and 2008 with just a few referenced so SQL Server 2000. If you'd like to know when the training class is coming to your area, just contact me through the SysEdCo.com contact page.

Absorption and Reflection in the Microwave and in Wireless LANs

I don’t know about you, but I like popcorn with a great movie. Of course, today we can get freshly popped popcorn in under four minutes thanks to the power of the microwave. Microwave ovens use the 2.4 GHz ISM frequency range (some use it all and some use just a portion) to pop that popcorn. The popcorn absorbs the RF energy by converting it to heat. Eventually, the heat builds up pressure and you hear that wonderful poppety pop pop sound coming from the microwave, which means you’ll be enjoying your movie and your popcorn in just a few minutes.

So, what does a microwave oven have to do with wireless LANs? Well, the answer to that question is twofold. First, it can be used as a teaching tool to understand concepts like absorption and reflection. Second, microwave ovens can cause interference with your wireless LAN in many scenarios.

As a teaching tool, the microwave oven can help you understand both absorption and reflection. When you put a glass of cold water in the microwave and turn the microwave on, the water heats up. Why? Because absorption occurs. Absorption, remember, is the conversion of RF energy to heat. Now, you can take out that glass of water and dip a nice tea bag in it to get some soothing hot tea.

Reflection is seen in the fact that very little of the output energy escapes from the microwave. Why? It is being reflected inward by the design of the internal unit. Place your cell phone in a microwave (without turning the microwave oven on, of course) and close the door. After a few seconds, open the door again – you’ll likely see that your phone is looking for service. Why? The design of the microwave keeps as much of the RF energy in as possible and that results in keeping the cell tower’s energy out as well.

Microwave ovens can cause interference simply because they operate in the same frequency space as 802.11, 802.11b and 802.11g devices. Many 802.11n devices may also attempt to communicate in the 2.4 GHz frequency space. While the microwave ovens do a good job of protecting you as a human (by keeping dangerous levels of RF energy inside the microwave), they certainly let plenty of the energy escape from the perspective of a nearby wireless LAN. Always test the microwaves in the area where you are installing a wireless LAN. It may dictate the channel you have to use.

After testing dozens of microwave ovens, I’ve determined that the average microwave oven leaks about as much RF energy as a consumer-grade (linksys) access point. The energy may be a little less focused, but it is spread over a larger range of the 2.4 GHz band. Watch out for this in your wireless LAN designs.

RF Wavelength Calculations for Wireless Networks

The wavelength of a RF wave is calculated as the distance between two adjacent identical points on the wave. The wavelength is frequently measured as the distance from one crest of the wave to the next.

The wavelength is an important factor in wireless networking. The wavelength dictates the optimum size of the receiving antenna and it determines how the RF wave will interact with its environment. For example, an RF wave will react differently when it strikes an object that is large in comparison to the wavelength than when it strikes an object that is small in comparison to the wavelength.

The wavelength and the frequency are interrelated. For a given medium, if you know the wavelength, you can calculate the frequency and if you know the frequency, you can calculate the wavelength. The wavelength is directly related to the frequency and the speed of light. If you know the frequency, you can calculate the wavelength. If you know the wavelength, you can calculate the frequency.

One of the great discoveries in the history of electromagnetism is that electromagnetic waves travel at the speed of light. Since we know the speed of light to be 299,792,458 meters per second (or the simple 300,000,00 meters per second, if you prefer), we also know that this is the speed at which electromagnetic waves travel in a vacuum. This was theorized by James Clerk Maxwell and proved through experimentation by Heinrich Hertz.

You are probably familiar with measurements like 100 megahertz and 3.6 gigahertz. These measurements refer to the number of cycles per second. When we say that the access point is using the 2.45 GHz (gigahertz) spectrum, we say it is using the spectrum that uses a wave cycle rate of 2,450,000,000 times per second. This measurement is named for Heinrich Hertz and his research in electricity and magnetism. A kilohertz is 1,000 hertz or cycles per second. A megahertz is 1,000,000 hertz and a gigahertz is 1,000,000,000 hertz. A terahertz is one trillion hertz, but these frequencies are not commonly found in today’s wireless communications.

Since we know that RF waves travel at the speed of light we can calculate the frequency when we know the wavelength or the wavelength when we know the frequency. The following formula can be used to calculate the wavelength in meters when the frequency is known:

w = 299,792,458 / f

Where w is the wavelength in meters and f is the frequency in hertz and the medium is a vacuum. Therefore, the 2.45 GHz spectrum would have a wavelength that is calculated with the following formula:

w = 299,792,458 / 2,450,000,000

The result is .123 meters or approximately 12.3 centimeters in length. This translates to about 4.8 inches. To calculate inches from centimeters, just multiple the number of centimeters times 0.3937. The formal character used to represent a wavelength is the Greek lambda (λ), and the symbol for the speed of light is c. Therefore, the formal representation of the previous formula would be:

λ = c / f

The calculation for frequency is just the opposite. You will divide the speed of light by the wavelength in meters to discover the frequency. Keep in mind that the numbers we’ve been using have been rounded and that impacts the results of the following formula; however, the results are close enough to recognize that a wavelength of .123 meters would indicate a RF wave in the 2.45 GHz spectrum:

f = 299,792,458 / .123
f = 2437337056.91

Due to the complex measurement number that is the speed of light, this number is often rounded to 300 billion meters per second. While this will change formula results, the findings are close enough for understanding the behavior of RF waves; however, engineers developing RF systems must use more precise measurements. Additionally, formulas like the following simplify matters:

wavelength in inches (λ) = 11.811 / f (in GHz)
wavelength in centimeters (λ) = 30 / f (in GHz)

Because wireless networks use such high frequency ranges, formulas like this make the calculations easier.

How to Configure DirectAccess for Windows 7 and Server 2008 R2

DirectAccess (which is properly spelled as one word and not two, such as Direct Access – even though Microsoft gets it wrong in their website meta tags – though possibly intentional) is one of the most touted new features in Windows 7. Sadly, it’s not really a Windows 7 feature alone. You must deploy Windows Server 2008 R2 in order to take advantage of the DirectAccess feature.

Microsoft has, however, provided a lab demo configuration document here:

http://www.microsoft.com/downloads/details.aspx?displaylang=en&FamilyID=8d47ed5f-d217-4d84-b698-f39360d82fac

You can use this document as a starting point to explore DirectAccess configuration processes even if you don’t have a Server 2008 R2 machine at this time. Now, for some really good news. If you just want to play with WIndows Server 2008 R2, get the evaluation VHD that works in Hyper-V here:

http://www.microsoft.com/downloads/details.aspx?familyid=9040A4BE-C3CF-44A5-9052-A70314452305&displaylang=en

Hopefully this information will help you get started with configuring DirectAccess. Remember, you must configure DirectAccess on the Server 2008 R2 server as well as the Windows 7 clients.