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Wireless Network FAQ

Introduction
Purdue's central computing and telecommunications organization, ITaP (Information Technology at Purdue), has deployed a campus-wide wireless network called Purdue Air Link (PAL) for university students, faculty, staff, and visitors. The main goal of this design has been to provide a fast and secure computing environment for all wireless users. This document answers several questions users may have regarding wireless networking and Purdue Air Link.

1. What is wireless networking?
2. How does wireless networking work?
3. What are the benefits of wireless access?
4. Is wireless networking secure?
5. How is ITaP addressing security issues with PAL?
6. What technology is ITaP using to build the PAL wireless network?
7. What is IEEE, and what does 802.11b mean?
8. Why did ITaP select the IEEE 802.11b standard for PAL, rather than any of the other competing wireless technologies?
9. What kinds of devices can access PAL?
10. I'm planning on buying a laptop and/or PDA and would like to use it with PAL. What should I get?
11. I already own a laptop and/or PDA. What do I need to access PAL with it?
12. Where can I purchase a wireless network card?
13. I have my wireless network card installed. Do I need to change any settings or install any software on my device in order to access PAL?
14. How fast is PAL? What kind of data transfer speeds should users expect?
15. Where will PAL be available?
16. What kind of range does an AP get?
17. How are you covering large areas like Purdue Memorial Union?
18. What happens when I move between coverage areas of different AP’s?
19. Where do I go if I have trouble using PAL?
20. Can a visitor to the university use PAL to access the web?

1. What is wireless networking?
Wireless networking allows users of mobile devices such as laptop computers and personal digital assistants (PDA's) to access a computer network (such as the Purdue campus network or the Internet) without the need for a physical (that is, hard-wired) connection.

2. How does wireless networking work?
Wireless networking works very similar to a cordless telephone, where the phone base broadcasts a signal to the handset and then sends the handset’s responses through the telephone cord plugged into a wall jack. In wireless networking, a device called an Access Point (AP), which is hard wired to a computer network itself, broadcasts a signal to the surrounding area. Any device that is equipped with a wireless networking card can receive that signal and communicate with the AP, and through it, with the rest of the network.

3. What are the benefits of wireless access?
For end users, the freedom of mobility—users can easily move their devices around within an area served by an AP (for example, carrying a laptop from a desk to a nearby table), or from one such area to another (for example, from a classroom to a study lounge), without having to unplug and re-plug networking wires. For the network connection provider, the ability to offer network access in areas where installing a wired network would be difficult or prohibitive. Remember, though, that a wireless network works best as a supplement to a traditional wired network, not as a substitute for one.

4. Is wireless networking secure?
Because wireless network signals travel through the air just like signals used by cordless phones, radios, and other wireless devices, anybody within range can intercept that signal—and potentially view the data being sent back and forth by your computer. Just like law enforcement agencies can wiretap your phone, people on a wireless network can “tap” into your network connection. This means that a malicious user could read your e-mail, steal your passwords or credit card numbers, or intercept any other sensitive data that may be traveling over the network. In an attempt to protect wireless users from these types of attacks, the technology’s designers created an encryption process for it called Wired Equivalent Privacy (WEP). When WEP is activated, data sent over the network is encrypted and other users are unable to see in plain text what you are doing. However, due to a design flaw, WEP is easily compromised. An attacker can break the WEP encryption and still view your data by using some readily available programs.

Recently, the WEP extension to the 802.11 standard was re-evaluated and an update to it, known as Wi-Fi Protected Access (WPA), was ratified. To overcome the weaknesses of WEP, WPA uses stronger encryption keys and also has an accompanying key management system. This key management system is called the Temporal Key Integrity Protocol (TKIP) and it ensures that no two similar encryption keys are used in close enough proximity (time-wise) to give a would-be attacker enough data to crack the encryption.

By using WPA in conjunction with 802.1x (a port-based authentication system), wireless networks can now provide an even more secure connection than a wired connection can. This is the result of not only providing encryption once associated to the wireless network, but requiring users to be properly authenticated before being allowed to associate in the first place. This combination ensures that data transfers over the wireless medium are secure and that only authorized users are allowed onto the network. ;

5. How is ITaP addressing security issues with PAL?

ITaP is committed to providing our users with a trusted computing environment. With the introduction of PAL2.0, users now have a choice as to the method they use to connect to Purdue's wireless network: by using WPA or using a VPN (Virtual Private Network) connection. WPA, described above provides secure, authenticated access to PAL and give users the freedom to roam throughout coverage areas without losing their wireless connection (in most cases).

VPN technology requires users to authenticate themselves before using the wireless network, and encrypts all of the data that is carried on the wireless network. With a VPN-secured connection, all of the wireless traffic is encrypted using a strong encryption algorithm (168-bit 3DES encryption, as compared to the 128-bit or even 40-bit encryption offered by WEP).

This means that, in order to access PAL, users will be required to adjust their computer's network settings to negotiate the VPN connection directly or use WPA, and then to login to the network with a username and password combination each time they connect. For members of the Purdue community, this will be their Purdue Career Account username and password; visitors can be assigned guest accounts for temporary access (for VPN connections only). With this solution, wireless users can feel confident that their use of the wireless network is secure and that their data transfers are safe.

6. What technology is ITaP using to build the PAL wireless network?
To run the PAL wireless network, ITaP is installing networking equipment that is based on the IEEE 802.11b/g design standard, which provides the specifications for the devices that make up the two sides of the wireless connection: the wireless Access Points (AP’s) and the networking cards that users install in their electronic devices.

7. What is IEEE, and what does 802.11b/g mean?
IEEE is the Institute of Electrical and Electronics Engineers, a standards body that promotes design specifications to ensure compatibility between different manufacturers' products. 802.11b/g is simply the designation for the particular kind of wireless networking technology ITaP has chosen for PAL. Any wireless networking card that is advertised as being compatible with the 802.11b/g standard, therefore, will work fine with PAL; several different manufacturers produce such cards, designed for use with a wide variety of different operating systems and devices.

8. Why did ITaP select the IEEE 802.11b/g standard for PAL, rather than any of the other competing wireless technologies?
802.11b/g is a proven, award-winning technology that is widely available on the market today. While other wireless standards promise superior performance in comparison, many of these are either still in development or are just entering production, and so are not yet suitable for deployment on the sort of scale that PAL requires. As wireless networking technology continues to advance, ITaP will of course look for ways to improve PAL’s performance and usability. Because of the popularity of 802.11b/g wireless networking, developers of other technologies are making every effort to ensure backwards compatibility or dual-mode interoperability between 802.11b/g devices and their own. Therefore, when PAL is upgraded to a next-generation wireless technology base, the network will remain accessible to users with 802.11b/g-compatible devices, allowing them to migrate to the newer technology at their own pace.

9. What kinds of devices can access PAL?
PAL2.0 supports wireless-ready devices with WPA support running the following operating systems.

• Windows 2000/XP
• Mac OS X (Panther and Tiger only)
• Pocket PC 2003
• Linux (with Xsupplicant)

PAL1.0 supports wireless-ready devices running the following operating systems.

• Linux
• Mac OS X (NOT Mac OS 9 or earlier)
• Solaris 5.6/5.8
• Windows 95/98/ME/2000/XP/CE
• Handheld PC 2000
• Palm OS 3.5-4.1 (NOT PalmOS 5)
• PocketPC 3.0, 2002, 2003

As support for additional devices and operating systems becomes available, it will be added to the PAL website.

10. I'm planning on buying a laptop and/or PDA and would like to use it with PAL. What should I get?
First, make sure that the laptop or PDA that you're interested in runs one of the operating systems listed under question 9. In addition to checking the operating system, you will also need to ensure that it is compatible with 802.11b/g wireless networking (check with the manufacturer if you're not sure). If it is compatible, all you need to do is purchase and install a suitable networking card. Some devices can be ordered/purchased with a networking card preinstalled.

11. I already own a laptop and/or PDA. What do I need to access PAL with it?
Currently, only devices running an operating system listed under question 9 will be able to access PAL. If your device's operating system isn't listed here, you will need to upgrade the operating system (consult the manufacturer for details). In addition to checking the operating system, you will also need to ensure that it is compatible with 802.11b/g wireless networking (again, check with the manufacturer if you're not sure). If it is compatible, all you need to do is purchase and install a suitable networking card. Some devices come with a networking card preinstalled; if this is the case with yours, then you do not need to do anything else.

12. Where can I purchase a wireless network card?
802.11b/g cards are available from several vendors, and currently cost between $40 and $150. ITaP has negotiated special discounted pricing with a number of major manufacturers, some of whom offer networking cards—see ITaP’s shopping page at http://www.itap.purdue.edu/shopping for details. Alternatively, many bookstores around campus have wireless cards in stock, and major electronics and office-supply stores like Best Buy, Staples, Circuit City, and Wal-Mart frequently carry wireless cards as well.

13. I have my wireless network card installed. Do I need to change any settings or install any software on my device in order to access PAL?
Depending on the method you choose to use to connect to PAL, follow the instructions for your specific operating system. Links to the individual instructions pages can be found at the top of this page on the left in the navigation menu.

14. How fast is PAL? What kind of data transfer speeds should users expect?
The 802.11b standard has a maximum throughput of 11Mbps (comparable to 10base-T Ethernet) and but 802.11g increases the maximum throughput to 54Mbps The bandwidth available from one AP is shared among all users in its range. Further, an individual user’s bandwidth can increase or decrease according to the strength of the signal the user’s device is currently receiving. Therefore, PAL users should expect to see speeds around 4 to 6Mbps of throughput when associated with an 802.11b AP and around 15 to 27Mbps when associated to an 802.11g AP.

There is a widespread piece of misinformation regarding data transfer speeds when users are in a mixed b/g environment. Popular information states that if an 802.11b client enters an area populated entirely by 802.11g clients, the speed for all users is dropped to 11Mbps for compatibiltity. This is part truth. There are two major types of network traffic: unicast and broadcast. The above scenario only affects broadcast traffic since all users must be able to receive broadcasts in order for the network to function properly. Unicast traffic, which is between two hosts, is not affected by the above scenario (e.g unicast traffic to any of the 802.11g users would still transfer at the maximum theoretical throughput of 54Mbps).

15. Where is PAL available?
A list of buildings on the West Lafayette campus with partial or complete wireless coverage is available at http://www.itap.purdue.edu/airlink/info/plan.cfm. Alternately, you can view a map of campus with these buildings highlighted at http://www.itap.purdue.edu/airlink/info/WirelessCurrent3.pdf

16. What kind of range does an AP get?
Typical indoor range for an AP will be from 50 to 100 feet, while outdoors a signal can extend up to 100 yards, but this is dependant on many factors. In most situations, surrounding structural elements will decrease an AP’s effective range—intervening walls, floors, or ceilings between an AP and a user will generally dampen the signal, for example. Conversely, some AP’s may be equipped with signal-boosting antennas, which can increase their effective range significantly. If you are attempting to use a wireless connection in an area where signal strength is weak, moving your device just a few feet may improve your reception dramatically.

17. How are you covering large areas like Purdue Memorial Union?
We are using multiple AP’s in many buildings to offer the best signal strength and connectivity throughout.

18. What happens when I move between coverage areas of different AP’s?
So long as the coverage areas are contiguous, you will not notice any change in your network status; all of Purdue’s wireless AP’s are connected to the same section of the campus network (called a subnet) so you can move from one area to another without disturbing your connection—this is commonly known as “roaming.” When using original PAL, if you take your device out of range of an AP, your network connection will drop, and you will need to reconnect when you re-enter an AP coverage area.

When using PAL2.0 you won’t need to do anything to switch from one AP’s area of coverage to another—the wireless card in your device will automatically search the surrounding area for signals from nearby AP’s. If the card detects a decrease in signal strength, it will search for another AP with a better signal; likewise, if your card detects that it is losing data during transmissions, it will again search for another AP to use. Finally, your wireless card will periodically search for all 802.11 channels and assess which AP will give the best coverage—even if the signal it is currently receiving is holding steady, other changes nearby may result in the signal from another AP suddenly coming in much stronger, in which case the card will automatically switch over to this new signal. Changing coverage in this fashion is completely automatic, and transparent to the user.

19. Where do I go if I have trouble using PAL?
First, consult the PAL Web site http://www.itap.purdue.edu/airlink, which provides installation instructions and solutions to possible problems you may encounter. If you need further assistance, contact ITaP by e-mail at itap@purdue.edu or by telephone at 49-44000.

20. Can a visitor to the university use PAL to access the web?
Yes, temporary PUID numbers and passwords are available for University guests so that they can use the wireless network, but guest access must be requested by a Purdue University unit.

A school or department may request access for a single individual for one or more days or for a group attending a meeting. Temporary access will be disabled at the close of the requested time.

To request guest accounts for your visitors, visit Request Airlink Account page and fill out the appropriate form.

There is no charge for this service.