Why have Wireless LANs Become so Popular?
Business networks today are evolving to support people who are on the move. Employees and employers, students and faculty, government agents and those they serve, sports fans and shoppers, all are mobile and many of them are "connected." Perhaps you have a mobile phone that you route instant messages to when you are away from your computer. This is the vision of mobility-an environment where people can take their connection to the network along with them on the road.
There are many different infrastructures (wired LAN, service provider networks) that allow mobility like this to happen, but in a business environment, the most important is the WLAN.
Productivity is no longer restricted to a fixed work location or a defined time period. People now expect to be connected at any time and place, from the office to the airport or even the home. Traveling employees used to be restricted to pay phones for checking messages and returning a few phone calls between flights. Now employees can check e-mail, voice mail, and the status of products on personal digital assistants (PDAs) while at many temporary locations.
At home, many people have changed the way they live and learn. The Internet has become a standard service in many homes, along with TV and phone service. Even the method of accessing the Internet has quickly moved from temporary modem dialup service to dedicated DSL or cable service. Home users are seeking many of the same flexible wireless solutions as office workers. For the first time, in 2005, more Wi-Fi-enabled mobile laptops were purchased than fixed-location desktops.
In addition to the flexibility that WLANs offer, another important benefit is reduced costs. For example, with a wireless infrastructure already in place, savings are realized when moving a person within a building, reorganizing a lab, or moving to temporary locations or project sites. On average, the IT cost of moving an employee to a new location within a site is $375 (US dollars).
Another example is when a company moves into a new building that does not have any wired infrastructure. In this case, the savings resulting from using WLANs can be even more noticeable, because the cost of running cables through walls, ceilings, and floors is largely avoided.
Though harder to measure, WLANs can result in better productivity and more relaxed employees, leading to better results for customers and increased profits.
Wireless LANs
Most current business networks rely on switch-based LANs for day-to-day operation inside the office. However, workers are becoming more mobile and want to maintain access to their business LAN resources from locations other than their desks. Workers in the office want to take their laptops to meetings or to a co-worker's office. When using a laptop in another location, it is inconvenient to rely on a wired connection. In this topic, you will learn about wireless LANs (WLANs) and how they benefit a business. You will also explore the security concerns associated with WLANs.
Portable communications have become an expectation in many countries around the world. You can see portability and mobility in everything from cordless keyboards and headsets, to satellite phones and global positioning systems (GPS). The mix of wireless technologies in different types of networks allows workers to be mobile.
You can see that the WLAN is an extension of the Ethernet LAN. The function of the LAN has become mobile. You are going to learn about WLAN technology and the standards behind the mobility that allow people to continue a meeting, while walking, while in a cab, or while at the airport.
Comparing a WLAN to a LAN
Wireless LANs share a similar origin with Ethernet LANs. The IEEE has adopted the 802 LAN/MAN portfolio of computer network architecture standards. The two dominant 802 working groups are 802.3 Ethernet and 802.11 wireless LAN. However, there are important differences between the two.
WLANs use radio frequencies (RF) instead of cables at the physical layer and MAC sub-layer of the data link layer. In comparison to cable, RF has the following characteristics:
RF does not have boundaries, such as the limits of a wire in a sheath. The lack of such a boundary allows data frames traveling over the RF media to be available to anyone that can receive the RF signal.
RF is unprotected from outside signals, whereas cable is in an insulating sheath. Radios operating independently in the same geographic area but using the same or a similar RF can interfere with each other.
RF transmission is subject to the same challenges inherent in any wave-based technology, such as consumer radio. For example, as you get further away from the source, you may hear stations playing over each other or hear static in the transmission. Eventually you may lose the signal all together. Wired LANs have cables that are of an appropriate length to maintain signal strength.
RF bands are regulated differently in various countries. The use of WLANs is subject to additional regulations and sets of standards that are not applied to wired LANs.
WLANs connect clients to the network through a wireless access point (AP) instead of an Ethernet switch.
WLANs connect mobile devices that are often battery powered, as opposed to plugged-in LAN devices. Wireless network interface cards (NICs) tend to reduce the battery life of a mobile device.
WLANs support hosts that contend for access on the RF media (frequency bands). 802.11 prescribes collision-avoidance instead of collision-detection for media access to proactively avoid collisions within the media.
WLANs use a different frame format than wired Ethernet LANs. WLANs require additional information in the Layer 2 header of the frame.
WLANs raise more privacy issues because radio frequencies can reach outside the facility.
Wireless LANs share a similar origin with Ethernet LANs. The IEEE has adopted the 802 LAN/MAN portfolio of computer network architecture standards. The two dominant 802 working groups are 802.3 Ethernet and 802.11 wireless LAN. However, there are important differences between the two.
WLANs use radio frequencies (RF) instead of cables at the physical layer and MAC sub-layer of the data link layer. In comparison to cable, RF has the following characteristics:
RF does not have boundaries, such as the limits of a wire in a sheath. The lack of such a boundary allows data frames traveling over the RF media to be available to anyone that can receive the RF signal.
RF is unprotected from outside signals, whereas cable is in an insulating sheath. Radios operating independently in the same geographic area but using the same or a similar RF can interfere with each other.
RF transmission is subject to the same challenges inherent in any wave-based technology, such as consumer radio. For example, as you get further away from the source, you may hear stations playing over each other or hear static in the transmission. Eventually you may lose the signal all together. Wired LANs have cables that are of an appropriate length to maintain signal strength.
RF bands are regulated differently in various countries. The use of WLANs is subject to additional regulations and sets of standards that are not applied to wired LANs.
WLANs connect clients to the network through a wireless access point (AP) instead of an Ethernet switch.
WLANs connect mobile devices that are often battery powered, as opposed to plugged-in LAN devices. Wireless network interface cards (NICs) tend to reduce the battery life of a mobile device.
WLANs support hosts that contend for access on the RF media (frequency bands). 802.11 prescribes collision-avoidance instead of collision-detection for media access to proactively avoid collisions within the media.
WLANs use a different frame format than wired Ethernet LANs. WLANs require additional information in the Layer 2 header of the frame.
WLANs raise more privacy issues because radio frequencies can reach outside the facility.
Introducing Wireless LANs802.11 wireless LANs extend the 802.3 Ethernet LAN infrastructures to provide additional connectivity options. However, additional components and protocols are used to complete wireless connections.
In an 802.3 Ethernet LAN, each client has a cable that connects the client NIC to a switch. The switch is the point where the client gains access to the network.
In a wireless LAN, each client uses a wireless adapter to gain access to the network through a wireless device such as a wireless router or access point.
The wireless adapter in the client communicates with the wireless router or access point using RF signals. Once connected to the network, wireless clients can access network resources just as if they were wired to the network.
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