Figure 1
Revised: August 26, 2005
By Richard G. Baldwin
File: FwlProj050.htm
This laboratory project was prepared specifically for the benefit of my students who are enrolled in ITNW 1351, Fundamentals of Wireless LANs.
The project was designed under the assumption that students enrolled in the course have successfully completed the prerequisite course, ITNW 1325, Fundamentals of Networking Technologies.
The project design also assumes that the students are actively studying the material in the prescribed textbook for this course, which explains such complex topics as the IEEE 802.11g wireless specification.
Another browser window
I recommend that you open another copy of this document in a separate browser window so that you can easily view the discussion and the figures at the same time.
The purpose of this project is to introduce you to Windows Zero Wireless Configuration (WZWC).
WZWC will be used in several future laboratory projects.
The following equipment is required to complete this laboratory project:
What is Windows Zero Wireless Configuration (WZWC)?
A Google search produces a variety of different views and a number of opinions regarding WZWC. One of the most enlightening is available at Wired News and reads partially as follows:
"... in earlier versions of Windows, users had to configure their equipment through software written by the Wi-Fi hardware manufacturers -- which aren't known as user-friendly program writers. The configuration utilities varied from maker to maker, with various manufacturers sometimes using different words and definitions to describe the same concept. Microsoft stepped in with Wireless Zero Configuration to unify the utilities and ease the pain."
WZWC should already be enabled
If you purchased a WinXP compatible wireless NIC and installed it on your WinXP system according to the manufacturer's instructions, WZWC should already be enabled on your WinXP system. If not, you will need to contact the manufacturer and get the situation rectified.
The assumed starting point
I am going to assume that you are not currently connected to the wireless router, and that there are a couple of useful features of WZWC that have not yet been enabled on your computer (although that might not be a good assumption).
Begin the project by selecting the following menu sequence:
Start/Connect To/Wireless Network Connection
The Wireless Network Connection dialog
If you were not already connected to the wireless router, a dialog similar to that shown in Figure 1 should appear on your screen.
(If you were already connected, you will see something different.)
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The networks that will be showing
The number of networks, and the names of the networks that will appear in the list of networks in the dialog of Figure 1 will depend on how many wireless routers are within range of your computer.
All wireless routers in range will be seen
The wireless networks controlled by all wireless routers that are within range of your computer will appear on the list of networks shown in Figure 1, even if those networks are not on the preferred list of networks that I will discuss later.
Can connect manually if you know the password
Manually connecting to a network that is not currently on the preferred list will cause that network to be put on the list.
For the specific case shown in Figure 1, there were two wireless routers within range of my computer:
Initiate a connection
Click on the network that you want to connect to and then click the Connect button.
If encryption is enabled on the router, you will be asked to provide and to confirm the Network key. Provide the key and then click the Connect button on the Network key dialog box.
The connection gets made
After a short time delay during which some progress information will be shown on the screen, the appearance of the Wireless Network Connection dialog should change to become similar to that shown in Figure 2.
Note that the network that you selected should now be showing to be Connected on the right side. In the specific case of Figure 2, I connected to the Linksys router.
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Dismiss the dialog
Click the X-button in the upper-right corner of the dialog in Figure 2 to close the dialog.
Explore the Windows Zero Wireless Configuration
Now that you are connected to the wireless network, it is time to start exploring the Windows Zero Wireless Configuration.
Once again select the following menu sequence:
Start/Connect To/Wireless Network Connection
This time, the Wireless Network Connection Status dialog should appear on the screen as shown in Figure 3.
(This is similar to what you would have seen earlier if you were already connected to a wireless network.)
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Although it isn't indicated in the name of the dialog, this dialog is the graphical entry point to the Windows Zero Wireless Configuration (WZWC).
Select the General tab
Select the General tab of the dialog shown in Figure 3 if it isn't already selected.
Note that the General tab for this dialog is separated into two parts.
The top part of the General tab
The top part shows information about the connection, including the speed and the signal strength.
(In a future project having to do with wireless site surveys, you will use this dialog on a laptop computer to roam around in the locale of the wireless router and to record the signal strength at different locations.)
The bottom part of the General tab
The bottom part of the dialog in Figure 3 shows activity information relative to the connection.
If you use a browser at this point to connect to a website while monitoring this dialog, you should see increases in the number of data packets sent and and the number of data packets received.
For example, click the following link to download a large zip file. This should cause a substantial increase in the number of packets received as shown in Figure 3.
The View Wireless Networks button
Click the View Wireless Networks button in the dialog shown in Figure 3. This should cause a Wireless Network Connection dialog similar to that shown in Figure 2 to appear on the screen.
The Wireless Network Connection dialog
This is one way to access the Wireless Network Connection dialog whenever you need it. There are other ways to access this dialog as well.
If you have access to two or more wireless networks, this dialog will make it possible to disconnect from one and to connect to the other.
Re-acquire the dialog in Figure 3
Note that clicking the View Wireless Networks button causes the Wireless Network Connection dialog shown in Figure 3 to go away. We aren't finished with it yet, so go back and get it on the screen the same way you did it earlier.
The Disable button
Click the Disable button on the Wireless Network Connection Status dialog in Figure 3. If you then try to access a site on the Internet, you will find that your wireless connection has been broken.
You can re-enable the same wireless connection simply by selecting the following menu sequence:
Start/Connect To/Wireless Network Connection
Select the sequence twice
Select that menu sequence twice to:
Select the General tab on the Wireless Network Connection Status dialog if it isn't already selected.
The Properties button
Click the Properties button on the dialog in Figure 3.
This should cause the Wireless Network Connection Properties dialog shown in Figure 4 to appear on the screen, in addition to the dialog from Figure 3.
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Once again, select the General tab if it isn't already selected.
Clear the checkboxes
Clear the two checkboxes in Figure 4 that read as follows (they may or may not already be clear):
Then click the OK button on the dialog in Figure 4.
The dialog in Figure 4 should disappear, leaving the dialog from Figure 3 still on the screen.
The network icons
Examine the icons on the right side of the system tray at the bottom of the screen.
If you are connected to the wireless router, you should not see an icon there corresponding to the wireless connection.
(If you are not connected to the wireless router, you probably will see an icon there corresponding to the wireless router.)
Remove Linksys power
Remove power from the Linksys wireless router to fully disable it.
When you remove power from the Linksys router, several things should happen.
Websites are not avaiable
First, it should no longer be possible for you to connect to websites or other computers on the LAN using the Linksys wireless router.
(Note however that if you also have a wired connection, you may be able to connect to websites via the wired connection.)
Wireless icon should be visible
Second, a wireless icon should appear in the right end of the system tray with a large red X indicating that there is no connection.
If you point to that icon with your mouse, you should see a tooltip indicating that the Wireless Network Connection is not connected.
Linksys router is no longer available
Third, if you select the following menu sequence,
Start/Connect To/Wireless Network Connection
the Wireless Network Connection dialog shown in Figure 1 should appear, and should no longer show the Linksys router as being available.
Restore power to the Linksys router
This should cause the wireless connection to the Linksys wireless router to be re-established automatically.
If it doesn't, you should be able to manually re-establish the connection by selecting the following menu sequence:
Start/Connect To/Wireless Network Connection
Re-acquire the Wireless Network Connection Status dialog
Re-acquire the Wireless Network Connection Status dialog shown in Figure 3 by selecting the following menu sequence:
Start/Connect To/Wireless Network Connection
Re-acquire the Wireless Network Properties dialog
Re-acquire the Wireless Network Properties dialog shown in Figure 4 by clicking the Properties button in Figure 3.
Check the checkboxes
Check the two checkboxes in Figure 4 that read as follows:
Then click the OK button in Figure 4.
The dialog in Figure 4 should disappear, leaving the dialog from Figure 3 on the screen.
Examine the icons
Examine the icons on the right side of the system tray at the bottom of the screen. You should see an icon there corresponding to the wireless connection. This is the result of your having checked the checkbox in Figure 4 that reads:
Implement limited or no connectivity
The next step is to create a condition corresponding to the second checkbox in Figure 4 that reads:
This is a little more difficult to accomplish. You will accomplish it by changing the WEP password on the router to a password that is different from the one under which you are logged onto the router.
Change the WEP password
Use the procedures described in Incorporating Simple WEP Encryption to add or change the WEP password on the router. Change the password to a password that is different from the one that you used to log onto the router.
What happens when you change the password?
When you change the password, the wireless icon in the system tray should modify itself to show a yellow triangle with an exclamation mark.
A warning bubble pointing to that icon should appear telling you that you now have Limited or no connectivity. This notification is the result of you having checked the bottom checkbox in Figure 4 that reads:
Wireless Network Connection dialog
The Wireless Network Connection dialog shown in Figure 2 should change to look similar to that shown in Figure 5.
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Note the connectivity information on the right side of the linksys network in Figure 5, which now reads Limited or no connectivity.
Regaining full connectivity
To regain full connectivity to the Linksys router:
Retain this state
Allow the two checkboxes shown in Figure 4 to remain checked for the remainder of the project.
Preferred access order
A wireless network configuration can exist in at least four different states:
Note, for example, that both the linksys and the belkin54g networks in Figure 1 are in the Manual state.
How is the Manual state achieved?
A network can be put into the Manual state by:
You will be asked to confirm that you really do want to put the network into the Manual state.
What are the characteristics of the Manual state?
If a wireless network is in the Manual state, it will not connect automatically when you boot your computer, even if the computer is within range of the router. You must make the connection manually, as described earlier under Get a wireless connection.
Similarly, if you have access to two or more wireless networks and they are all in the Manual state, none of them will connect automatically when you boot your computer.
The Automatic state
On the other hand, if one of your wireless networks is in the Automatic state, it will connect automatically when you boot your computer provided that your computer is within range of the wireless router for that network.
How do you put a network into the Automatic state?
One way to put a wireless network into the Automatic state is to manually make a connection to its router and then turn your computer off without manually disconnecting from the router for that network.
(I will show you some other ways to put a network into the Automatic state later.)
With an exception that I will describe later involving preferred order, when you reboot your computer, a connection will be made automatically to that router provided that your computer is within range of the router.
Putting two or more networks in the Automatic state
If your computer is within range of two or more wireless routers, you can put them all in an Automatic state by:
If you do that, you will end up with one network in the Connected state and all of the other networks in the Automatic state.
You will automatically connect later
When you reboot your computer, you will automatically connect to one of the networks.
In that case, the one that you will automatically connect to will be determined by the Preferred network order.
(I will show you one more way to put a network into the Automatic state later.)
Which one will connect automatically?
This leads to the question as to which network the computer will connect to in the event that you have two or more networks in an Automatic state and they are all within range when you boot up your computer.
Preferred network order
The preferred connection order is determined by the order of the list of networks shown in the list of Preferred networks in Figure 6.
(The dialog in Figure 6 can be exposed by going to the dialog shown in Figure 4 and selecting the Wireless Networks tab.)
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Add or remove networks from the list
As you can see, the dialog in Figure 6 allows you to add new networks to the list of Preferred networks and to remove networks from the list of Preferred networks.
(When you click the Add button a dialog appears that allows you to add the network to the list on the basis of its network name, such as linksys, for example.)
Making a network Automatic
In addition,
exposes the linksys properties dialog shown in Figure 7.
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Putting a network in the Automatic state
The checkbox in Figure 7 makes it possible for you to switch that network back and forth between the Automatic state and a state referred to as On Demand.
(At this point in time, I am unable to explain the difference between the Manual state and the On Demand state. They appear to behave the same, but there is probably some subtle difference.)
This is the mechanism that I promised to show you earlier, which can be used to put a network in the Automatic state.
Getting back to the preferred order
Your computer will automatically connect to Automatic networks in the order that they are listed in the dialog shown in Figure 6, provided that they are within range of the router.
Modifying the preferred order
You can use the dialog in Figure 6 to modify the listed order, and hence the preferred order of connection.
To modify the listed order:
Automatic connect at boot up
The next time you boot up your computer, the Automatic network that is highest on the list and is also within range of your computer will be the one that gets connected.
Switching to a different wireless network
Even when all of the networks are in the Automatic state, you can switch the connection to a different network without changing the state of the networks by:
(Recall that selecting a network and clicking the Disconnect button will switch it into the Manual state.)
Does not change the preferred order
This process of switching to a different network using this approach does not change the preferred order.
The next time you boot up your computer, the preferred order will prevail.
The Automatic network that is closest to the top of the list in Figure 6, and is also within range, is the network that will be automatically connected the next time you boot up your computer.
Wireless Network Connection Status Support tab
Go to the Wireless Network Connection Status dialog shown in Figure 3 and click on the Support tab. This will expose the dialog shown in Figure 8.
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It will probably be useful for you to learn a little about what you see there.
What is an IP address?
Every computer or device that communicates on the Internet must have an address. Some of those devices must have globally-unique addresses and some do not.
A globally-unique address
For example, the server on my website at http://www.dickbaldwin.com must have a globally-unique address so that computers belonging to people from all over the globe can find it on the web and can communicate with it.
A locally-unique address
On the other hand, the computer on my desk at the college doesn't need a globally-unique address. It needs only a locally-unique address, because no computer from outside the campus has any reason to communicate with it.
IP addresses have 32 bits
All Internet addresses, commonly known as IP addresses, (where IP stands for Internet Protocol) are 32-bit addresses.
However, most representations of IP addresses that are produced for human consumption are not presented as 32 binary bits.
(Most humans aren't very good at remembering long strings of characters made up of 1 and 0.)
Four decimal-equivalent values
Rather, the 32-bit address is typically subdivided into four groups of eight bits each. Each group of eight bits is represented (for human consumption) by its decimal equivalent value with those four values separated by periods. An example of such a format follows:
256.128.64.32
For human consumption only
Remember, this is simply a representation of the 32-bit address for human consumption. The fact that the address can be represented in this way doesn't change the fact that it continues to be a 32-bit address.
My current IP address
Right now, my computer has a wireless connection to my Belkin wireless router, which is connected directly to the cable modem provided by my Internet Service Provider (ISP). My cable company is also my ISP in addition to providing cable services for my television.
The IP address that was most recently assigned to my router by the cable company is:
66.69.231.68
In other words, this is the address that the cable modem uses to communicate with my router. This is the address of the router when viewed from the outside of my house looking in.
The router address from the viewpoint of my computer
On the other hand, the router has assumed the following IP address for communication with the computers inside my house that have established wireless connections with the router:
192.168.2.1
(Actually, I was the one who selected that IP address, from a set of allowable addresses for the router, when I configured it for installation in my house.)
Router acts as a store and forward device
In other words, my computer cannot communicate directly with the cable modem (the ISP).
When my computer needs to send a message to the ISP for forwarding to some web site on the Internet, my computer will send the message to the router using the address 192.168.2.1.
The router will forward that message to the cable modem which will, in turn forward it on to the device on the Internet for which it is ultimately intended.
The current IP address of my computer
There are currently two wireless routers in my house within range of my computer: a Belkin router and a Linksys router.
The Linksys router is connected as a wired device to the Belkin router. My computer is currently connected as a wireless device to the Belkin router.
My Belkin router, has assigned the following IP address to my computer:
192.168.2.2
and has assigned the following IP address to my wife' computer:
192.168.2.3
A different IP address
My computer can make a wireless connection to either wireless router.
When my computer makes a wireless connection to the Linksys router, it will be assigned a different IP address by the Linksys router, because the Linksys router is configured somewhat differently from the Belkin router.
Thus, the IP address assigned to an individual computer can change over time.
A response to my message
When the ISP receives the response to the message that I sent to the web site discussed earlier, it will forward that response to my Belkin router at 66.69.231.68.
The Belkin router will turn around and attempt to deliver the response to my computer at 192.168.2.2. If my computer still has a wireless connection to the Belkin router, it will accept the message and present it to me in the form of a display in my browser window.
A globally-unique IP address
I believe that 66.69.231.68, which is currently assigned to my router, is a globally-unique IP address. In other words, at any instant in time, only one device operating on the Internet anywhere on Earth will be using that address. I say that because this IP address is not an address that is set aside for use as a private IP address.
Private IP addresses
According to http://www.faqs.org/rfcs/rfc1918.html, the Internet Assigned Numbers Authority (IANA) has reserved the following three blocks of the IP address space for private internets:
10.0.0.0 - 10.255.255.255 172.16.0.0 - 172.31.255.255 192.168.0.0 - 192.168.255.255
Not a globally-unique IP address
The current IP address of my computer, 192.168.2.2 is not a globally-unique address. It is one of the addresses that has been set aside for use as a private IP address.
At any point in time, there are thousands and possibly millions of devices using that same IP address on a worldwide basis.
A private network
The network on the back side of my router, consisting of my computer and my wife's computer, plus a couple of older computers used for data backup, is a private network. My router is managing this private network, and only my router is aware of the existence of these computers. The Internet at large doesn't know of their existence.
Thousands of private networks
I'm confident that somewhere else in the world, (maybe in the house next door), there is another router managing a private network using the same addresses.
In fact, I am confident that scattered around the world there are thousands of other routers managing thousands of private networks using the same IP addresses.
A real-world analogy
This is analogous to the postal mail situation in a company. The postal address of the company is globally-unique. No other postal destination anywhere on the globe has the same address as a particular company. This is necessary to guarantee that letters destined for the company don't end up somewhere else.
Postal mail is delivered to the company mailbox
The postal service delivers all mail to a mailbox representing the company. The postal service doesn't deliver letters to Dick Baldwin who happen to work for the company.
Internal mail distribution
Once the letters reach the company's mailbox, it is up to the company to manage the distribution of the individual letters to the employees who work there. In this sense the company is analogous to a router and an individual employee is analogous to an individual computer in a private network managed by the router.
Internal mail addresses
Company management can assign whatever internal address to Dick Baldwin's cubicle that it considers appropriate For example, management could assign the internal mail address 192.168.2.2 to Dick Baldwin's cubicle if it chose to do so. Then the mail clerk would deliver mail addressed to Dick Baldwin in care of the company to that cubicle.
In other words, the mail clerk would know the address of the cubicle currently occupied by Dick Baldwin.
Not visible outside the company
Persons outside the company would know about, or could learn about, the mailbox address belonging to the company. However, persons outside the company wouldn't have any reason to know anything about cubicle number 192.168.2.2, nor would they know who occupies that cubicle at any particular point in time.
The cubicle number isn't normally a part of the postal address for Dick Baldwin within the company. Usually only Dick Baldwin's name is a part of that postal address.
The current IP address for my computer
As you can see in Figure 8, at the time that I took the screen shot, the IP address 192.168.2.2 had been assigned to my computer.
In theory, the assigned address could be different at a different time on a different day, based solely on the decision of the address-assignment algorithm in the router.
In reality, the address probably will be different at a different time on a different day if my computer connects to a different wireless router.
What is DHCP?
According to http://www.dhcp.org/:
"The Dynamic Host Configuration Protocol (DHCP) is an Internet protocol for automating the configuration of computers that use TCP/IP. DHCP can be used to automatically assign IP addresses, to deliver TCP/IP stack configuration parameters such as the subnet mask and default router, and to provide other configuration information such as the addresses for printer, time and news servers."
In other words, with respect to my wireless router, DHCP is the process that manages the assignment of IP address and other information related to IP addresses to the computers on the private network managed by my wireless router.
Different router configurations
Routers can be set up in several different ways. One way is to cause the router to assign IP addresses to the computers that connect to the router in essentially a random fashion making certain that no two computers are connected to the router at the same time with the same IP address. That is what is meant by the terminology Assigned by DHCP in Figure 8.
What is a subnet mask?
IP addresses can be thought of as existing in a hierarchical fashion, with each level in the hierarchy being made up of sub-networks or subnets.
Another postal analogy
For example, going back to the postal mail analogy, the campus of the college where I teach is located in Austin, Texas, in zip code 78758.
All of the postal addresses in Texas could be thought of as a subnet of all of the addresses in the United States.
All of the addresses in Austin could be thought of as a subnet of all the addresses in Texas.
The Austin subnet is subdivided into several zip codes. All of the addresses in zip code 78758 could be thought of as a subnet of the Austin subnet.
The campus where I normally teach is located in the 78758 subnet. That college campus, which provides a postal mailbox for each of its employees, forms a subnet of the subnet known as 78758.
A private subnet
Furthermore, the postal subnet on the campus is a private subnet, the details of which are known only to college management and employees. People outside the college don't know (and don't care) about the process by which mail is delivered to me once it reaches the campus.
My campus mail is delivered to a mailbox that is assigned to me in a central mailroom on the campus. My specific mailbox can be thought of as a leaf of the hierarchical tree. The mailbox is somewhat analogous to a specific value in the right-most eight bits of the IP address that is assigned to my computer in my private wireless network.
So, what is a subnet mask?
I can't explain the subnet mask in detail without getting into a lot of detail about the bits in an IP address. I don't want to get into that kind of detail in this project.
Suffice it to say that the subnet mask 255.255.255.0 showing in Figure 8 means that the subnet to which my computer belongs consists of the set of IP addresses ranging from 192.168.2.1 to 192.168.2.255.
(This assumes that the address 192.168.2.0 is not allowed, but I'm not certain of that.)
Note that the first three numbers in this range match the first three numbers in the IP address assigned to my computer. The last number in the range consists of all possible combinations of eight binary bits.
Thus, this private subnet could consist of 255 separate connected devices (including the router that manages the subnet having an IP address of 192.168.2.1). Each connected device would have a different (and locally unique) IP address. Beyond 255 devices, there would be no addresses available in the subnet to assign to devices that request a connection.
What is a default gateway?
In theory, a computer in a subnet can discover the address of and send a message directly to any other computer in the same subnet. However, it can't send a message directly to any computer that is outside the subnet.
A forwarding address
When a computer needs to send a message to a computer that is outside the subnet, it sends that message to the device having an address that matches the address of the default gateway. It is the responsibility of that device to determine where next to send that message (possibly to another gateway) and to send the message on its way.
Same as internal router address
Note that in Figure 8, the address of the Default Gateway is the same as the internal address of the router. Thus, my computer will send messages destined for computers outside the subnet to the router. The router will then forward the messages on to their final destination.
Cable company uses DHCP
For residential class service, my cable company also operates under DHCP rules and assigns an IP address to each of its customers.
To prevent someone like myself from paying for residential class service and operating an Internet store out of my house, the cable company periodically changes (or at least threatens to change) the IP address that is assigned to my account.
(If I am willing to pay an additional amount for business class service, the cable company will assign a static IP address to my account and won't change it as long as I pay my monthly bill. That would make it possible for me to operate an Internet store out of my house.)
The IP address assigned to my account
As mentioned earlier, at the time of this writing, the cable company has assigned the following IP address to my account: 66.69.231.68. That IP address is part of a subnet defined as 255.255.240.0. If I did the arithmetic correctly, that means that my account is part of a subnet consisting of 4096 accounts.
The default gateway
The default gateway provided by the cable company in conjunction with the IP address and the subnet mask was 66.69.231.68.
When my computer needs to send a message to http://www.dickbaldwin.com, for example, it first contacts something called a Domain Name Server or DNS (which I won't get into in detail here) to determine the IP address that represents that web site.
(The current IP address of the DNS provided by the cable company is 24.93.41.125. The DNS will send back the registered IP address for http://www.dickbaldwin.com. For discussion purposes, assume that the IP address of that web site is 123.456.789.012)
Sending the message
My computer would then construct the message as a series of packets and send those packets to the router gateway at 192.168.2.1 requesting that the packets be forwarded to 123.456.789.012.
The router would send the packets to the cable company gateway at 66.69.231.68 requesting that they be forwarded to 123.456.789.012.
The cable company would send them to another forwarding address with the request that they be forwarded to 123.456.789.012.
This store and forward process would continue until the packets finally arrive at http://www.dickbaldwin.com where they would be used to reconstruct the original message.
Responding to the message
The server at http://www.dickbaldwin.com would construct a response and send it back to my computer essentially reversing the process by which the message arrived at that server in the first place.
And that is probably more than you ever wanted to hear about DHCP, IP addresses, Subnet Masks, Default Gateways, and Domain Name Servers.
Copyright 2005, Richard G. Baldwin. Reproduction in whole or in part in any form or medium without express written permission from Richard Baldwin is prohibited.
Richard has participated in numerous consulting projects and he frequently provides onsite training at the high-tech companies located in and around Austin, Texas. He is the author of Baldwin's Programming Tutorials, which have gained a worldwide following among experienced and aspiring programmers. He has also published articles in JavaPro magazine.
In addition to his programming expertise, Richard has many years of practical experience in Digital Signal Processing (DSP). His first job after he earned his Bachelor's degree was doing DSP in the Seismic Research Department of Texas Instruments. (TI is still a world leader in DSP.) In the following years, he applied his programming and DSP expertise to other interesting areas including sonar and underwater acoustics.
Richard holds an MSEE degree from Southern Methodist University and has many years of experience in the application of computer technology to real-world problems.
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