24-04-2010, 11:39 AM
[attachment=3385]
PAPER PRESENTATION
PRESENTED BY
M.Girish kumar
G.prakash
IIIECE
St.Ann's College of Engineering &Technology
CHIRALA
ABSTRACT
Technology is no longer judged by its technical brilliance, but by the return on investment (both tangible and intangible). This in turn, is dictated by the killer application for that technology. Wi reless Networks fit into this because the technology has been around long enough and can provide enough benefits to be seriously considered for deployment.
At the enterprise, it provides communication support for mobile computing. It overcomes and, in fact, annihilates the physical limitation of wired networks in terms of adaptability to a variation in demand. Network connectivity in a company's meeting room is a classic example. The number of users using that room would vary for different meetings. So, it would be difficult to decide how many wired network ports to put there. With wireless access, the number of users is mostly constrained by the bandwidth available on the wireless network.
Mobility is another feature by wireless. Mobile users can be truly m obile, in that hey don't need to be bound to their seats when connecting to the network. Mobility, however is not only associated with users, it's also associated with the infrastructure itself. You can have a wireless network up and running in no time, a boon for people who need to do it for exhibitions, events, etc.
This leads to other provision of wireless, that of scalability. It really helps in extending your network. It also becomes important if an enterprise has a rented office and needs to shift to a new place. At home, the need for wireless is more to do with ubiquitous computing.
Wi-Fi, or wireless fidelity, is freedom: it allows you to connect to the internet from your couch at home, a bed in a hotel room, or a conference room at work without wires. It is a wireless technology like cell phones, Wi -Fi enabled computers send and receive data indoors and outdoors; anywhere within the range of the base station. And the best thing of all, Wi-Fi is fast. In fact, it's several times faster than the fastes t cable modem connection.
Wireless technology, therefore is really happening, and should be seriously considered. The following presentation explains wireless LANs, their basic operations, topologies; security features and answers some of the questions eva luating WLAN technology.
1. IEEE 802.11b Wireless Networking Overview
Approval of the IEEE 802.11 standard for wireless local area networking (WLAN) and rapid progress made toward higher data rates have put the promise of truly mobile computing within reach. While wired LANs have been a mainstream technology for at least fifteen years, WLANs are uncharted territory for most networking professionals.
In September of 1999, the Institute of Electrical and Electronic Engineers (IEEE) ratified the specification for IEEE 802.11b, also known as Wi -Fi. IEEE 802.11b defines the physical layer and media access control (MAC) sub layer for communications across a shared, wireless local area network (WLAN).
At the physical layer, IEEE 802.11b operates at the radio frequency of 2.45 gigahertz (GHz) with a maximum bit rate of 11 Mbps. It uses the direct sequence spread spectrum (DSSS) transmission technique. At the MAC sub layer of the Data Link layer, 802.11b uses the carrier sense multiple access with collision avoidance (CSMA/CA) media access control (MAC) protocol.
A wireless station with a frame to transmit first listens on the wireless medium to determine if another station is currentl y transmitting (this is the carrier sense portion of CSMA/CA). If the medium is being used, the wireless station calculates a random back off delay. Only after the random back off delay elapses can the wireless station again listen for a transmitting station. By instituting a random back off delay, multiple stations that are waiting to transmit do not end up trying to transmit at the same time (this is the collision avoidance portion of CSMA/CA). Collisions can occur and, unlike with Ethernet, they might not be detected by the transmitting nodes. Therefore, 802.11b uses a Request to Send (RTS)/Clear to Send (CTS) protocol with an Acknowledgment (ACK) signal to ensure that a frame is successfully transmitted and received.
2. Wireless Networking Components
IEEE 802.11b wireless networking consists of the following components:
Stations: A station (STA) is a network node that is equipped with a wireless network device. A personal computer with a wireless network adapter is known as a wireless client. Wireless clients can communicate directly with each other or through a wireless access point (AP). Wireless clients are mobile.
Wireless AP: wireless AP is a wireless network node that acts as a bridge between STAs and a wired network. A wireless AP contains:
1. At least one interface that connects the wireless AP to an existing wired network (such as an Ethernet backbone).
2. A wireless network device with which it creates wireless connections with
STAs.
3. IEEE 802.1D bridging software, so that it can act as a transparent bridge
between the wireless and wired networks.
The wireless AP is similar to a cellular phone network's base station. Wireless clients communicate with both the wired network and other wireless clients through the wireless AP. Wireless APs are not mobile and act as peripheral bridge devices that extend a wired network.
Ports: A port is a channel of a device that can support a single point -to-point connection. For IEEE 802.11b, a port is an association, a logical entity over which a single wire less connection is made. A typical wireless client with a single wireless network adapter has one port and can support only one wireless connection. A typical wireless AP has multiple ports and can simultaneously support multiple wireless connections. The logical connection between a port on the wireless client and the port on a wireless AP is a point -to-point bridged LAN segmentâ€similar to an Ethernet-based network client that is connected to an Ethernet switch.
3. IEEE 802.11b Operating Modes (network topology)
AP's are not mobile, and form part of the wired network infrastructure. A BSS in this Configuration is said to be operating in infrastructure mode.
IEEE 802.11 defines two operating modes: Ad hoc mode and Infrastructure mode. The basic topology of an 802.11 network is shown in Figure 1. A Basic Service Set (BSS) consists of two or more wireless nodes, or stations (STAs), which have r ecognized each other and have established communications. In the most basic form, stations communicate directly with each other on a peer-to-peer level sharing a given cell coverage area. This type of network is often formed on a temporary basis, and is commonly referred to as an ad hoc network, or Independent Basic Service Set (IBSS).
The Extended Service Set (ESS) shown in Figure 2 consists of a series of overlapping BSSs (each containing an AP) connected together by means of a Distribution System (DS). Although the DS could be any type of network, it is almost invariably an Ethernet LAN. Mobile nodes can roam between APs and seamless campus -wide coverage is possible.
4. IEEE 802.11b Operation Basics
When a wireless adapter is turned on, it begins to scan across the wireless frequencies for wireless APs and other wireless clients in ad hoc mode. Assuming that the wireless client is configured to operate in infrastructure mode, the wireless adapter chooses a wireless AP with which to connect. This selection is made automatically by using SSID and signal strength and frame error rate information. Next, the wireless adapter switches to the assigned channel of the selected wireless AP and negotiates the use of a port. This is known as establishing an association.
If the signal strength of the wireless AP is too low, the error rate too high, or if instructed by the operating system (in the case of Windows XP), the wireless adapter scans for other wireless APs to determine whether a different wireless AP can provide a stronger signal or lower error rate. If suc h a wireless AP is located, the wireless adapter switches to the channel of that wireless AP and negotiates the use of a port. This is known as reassociation.
Reassociation with a different wireless AP can occur for several reasons. The signal can weaken as either the wireless adapter moves away from the wireless AP or the wireless AP becomes congested with too much traffic or interference. By switching to another wireless AP, the wireless adapter can distribute the load to other wireless APs, increasing the performance for other wireless clients.
5. Radio Technology in 802.11
IEEE 802.11 provides for two variations of the PHY. These include two (2) RF technologies namely Direct Sequence Spread Spectrum (DSSS), and Freque ncy Hopped Spread Spectrum (FHSS). The DSSS and FHSS PHY options were designed specifically to conform to FCC regulations (FCC 15.247) for operation in the 2.4 GHz ISM band, which has worldwide allocation for unlicensed operation.
| Data
1 1 Bit Barker Cod** (PRN); 101 1101000
Figure 3 Digital Modulation of Data with PRM Sequence
DSSS systems use technology similar to GPS satellites and some types of cell phones. Each information bit is combined via an XOR function with a longer Pseudo -random Numerical (PN) sequence as shown in Figure 3. The result is a high speed digital stream which is then modulated onto a carrier frequency using Differential Phase Shift
Keying (DPSK).
When receiving the DSSS signal, a matched filter correlator is used as shown in Figure 4.The correlator removes the PN sequence and recovers the original data str eam. Tat the higher data rates of 5.5 and 11 Mbps, DSSS receivers employ different PN codes and a bank of correlators to recover the transmitted data stream. The high rate modulation method is called Complimentary Code Keying (CCK). The effects of using PN codes to generate the spread spectrum signal are shown in Figure 5.
As shown in Figure 5a, the PN sequence spreads the transmitted bandwidth of the resulting signal (thus the term, "spread spectrum") and reduces peak power. Note however, that total power is unchanged. Upon reception, the signal is correlated with the same PN sequence to reject narrow band interference and recover the original binary data (Fig. 5b). Regardless of whether the data rate is 1, 2, 5.5, or 11 Mbps, the channel bandwidth is about 20 MHz for DSSS systems. Therefore, the ISM band will accommodate up to three non-overlapping channels
6. Multiple Access
The basic access method for 802.11 is the Distributed Coordination Function (DCF) which uses Carrier Sense Multiple Access / Collision Avoidance (CSMA / CA). This requires each station to listen for other users. If the channel is idle, the station may transmit. However if it is busy, each station waits until transmission stops, and then enters into a random back off procedure. This prevents multiple stations from seizing the medium immediately after completion of the preceding transmission.
Figure 7 CSMA/CD Back-off Algorithm
Packet reception in DCF requires acknowledgement as shown in Figure 7. The period between completion of packet transmission and start of t he ACK frame is one Short Inter Frame Space (SIFS). ACK frames have a higher priority than other traffic. Fast acknowledgement is one of the salient features of the 802.11 standard, because it requires ACKs to be handled at the MAC sub layer.
The underlying assumption is that every station can "hear" all other stations. This is not always the case. Referring to Figure 8, the AP is within range of the STA -A, but STA-B is out of range. STA-B would not be able to detect transmissions from STA -A, and the probability of collision is greatly increased. This is known as the Hidden Node.
To combat this problem, a second carrier sense mechanism is available. Virtual Carrier Sense enables a station to reserve the medium for a specified period of time through the use of RTS/CTS frames.
7. IEEE 802.11 Security The IEEE 802.11 standard defines the following mechanisms for wireless security:
¢ Authentication through the open system and shared key authentication types
¢ Data confidentiality through Wired Equi valent Privacy (WEP)
Open system authentication is used when no authentication is required. Some wireless APs allow the configuration of the MAC addresses of allowed wireless clients. However, this is not secure because the MAC address of a wireless cli ent can be spoofed.
Shared key authentication verifies that an authenticating wireless client has knowledge of a shared secret. This is similar to preshared key authentication in Internet Protocol security (IPsec). The 802.11 standard currently assumes th at the shared key is delivered to participating STAs through a secure channel that is independent of IEEE 802.11. In practice, this secret is manually configured for both the wireless AP and client. Because the shared key authentication secret must be dist ributed manually, this method of authentication does not scale to a large infrastructure mode network (for example, corporate campuses and public plac es, such as malls and airports) for use.
Inherent in the nature of wireless networks, securing physical ac cess to the network is difficult. Because a physical port is not required, anyone within range of a wireless AP can send and receive frames, as well as listen for other frames being sent. Without WEP, eavesdropping and remote packet sniffing would be very easy. WEP is defined by the IEEE 802.11 standard and is intended to provide the level of data confidentiality that is equivalent to a wired network.
WEP provides data confidentiality services by encrypting the data sent between wireless nodes. WEP encryption uses the RC4 symmetrical stream cipher with either a 40-bit or 104-bit encryption key. WEP provides data integrity from random errors by including an integrity check value (ICV) in the encrypted portion of the wireless frame.
However, one significant problem remains with WEP. The determination and distribution of WEP keys are not defined and must be distributed through a secure channel that is independent of 802.11. Obviously, this key distribution system does not scale well to an enterprise organization.
Additionally, there is no defined mechanism to change the WEP key â€either per authentication or at periodic intervals over the duration of an authenticated connection. All wireless APs and clients use the same manually configured WEP key for multiple connections and authentications. With multiple wireless clients sending large amounts of data, it is possible for a malicious user to remotely capture large amounts of WEP cipher text and use cryptanalysis methods to determine the WEP key.
The lack of WEP key management, to both automatically determine a WEP key and change it frequently, is a principal limitation of 802.11 security, especially with a large number of wireless clients in infrastructure mode. The lack of automated authentication and key determination services also effects operation in ad hoc mode.
The combination of a lack of both adequate authentication methods and key management for encryption of wireless data has led the IEEE to adopt the IEEE 802.1X Port-Based Network Access Control standard for wireless connections
8. The Wireless Ethernet Compatibility Alliance
The recently adopted Complimentary Code Keying (CCK) waveform delivers speeds of 5.5 and 11 Mbps in the same occupied bandwidth as current generation 1 and 2 Mbps DSSS radios and will be fully backward compatible. Now that a standard is firmly in place, WLANs will become a part of the enterprise networking landscape within the next twelve months.
The mission of the Wireless Ethernet Compatibility Alliance is to provide certification of compliance with the IEEE 802.11 Standard and to ensure that products from multiple vendors meet strict requirements for interoperability. With cross vendor interoperability assured, WLANs are now able to fulfill the promise of hi gh speed mobile computing.
Conclusion:
The use of wireless LANs is expected to increase dramatically in the future as businesses discover the enhanced productivity and the increased mobility that wireless communications can provide in a society that is m oving towards more connectionless connections.
In conclusion, the panelists felt that hurdles in deploying WLANs can be overcome. Cost of wireless services are already falling. The issue is now to lower the costs of the device that is needed to access the WLAN. Large chop design companies can make use of this opportunity to get into the market place. And Wi -Fi cannot move ahead quickly without support form private and government sectors
Bibliography:
1. Data over wireless networks -Gilbert Held
2. Electronics for you (magazine) June 2003 & February 2003
3. Electronics today (magazine) March 2003
4. A Technical tutorial on the IEEE 802.11 protocol - Pablo Brenner
PAPER PRESENTATION
PRESENTED BY
M.Girish kumar
G.prakash
IIIECE
St.Ann's College of Engineering &Technology
CHIRALA
ABSTRACT
Technology is no longer judged by its technical brilliance, but by the return on investment (both tangible and intangible). This in turn, is dictated by the killer application for that technology. Wi reless Networks fit into this because the technology has been around long enough and can provide enough benefits to be seriously considered for deployment.
At the enterprise, it provides communication support for mobile computing. It overcomes and, in fact, annihilates the physical limitation of wired networks in terms of adaptability to a variation in demand. Network connectivity in a company's meeting room is a classic example. The number of users using that room would vary for different meetings. So, it would be difficult to decide how many wired network ports to put there. With wireless access, the number of users is mostly constrained by the bandwidth available on the wireless network.
Mobility is another feature by wireless. Mobile users can be truly m obile, in that hey don't need to be bound to their seats when connecting to the network. Mobility, however is not only associated with users, it's also associated with the infrastructure itself. You can have a wireless network up and running in no time, a boon for people who need to do it for exhibitions, events, etc.
This leads to other provision of wireless, that of scalability. It really helps in extending your network. It also becomes important if an enterprise has a rented office and needs to shift to a new place. At home, the need for wireless is more to do with ubiquitous computing.
Wi-Fi, or wireless fidelity, is freedom: it allows you to connect to the internet from your couch at home, a bed in a hotel room, or a conference room at work without wires. It is a wireless technology like cell phones, Wi -Fi enabled computers send and receive data indoors and outdoors; anywhere within the range of the base station. And the best thing of all, Wi-Fi is fast. In fact, it's several times faster than the fastes t cable modem connection.
Wireless technology, therefore is really happening, and should be seriously considered. The following presentation explains wireless LANs, their basic operations, topologies; security features and answers some of the questions eva luating WLAN technology.
1. IEEE 802.11b Wireless Networking Overview
Approval of the IEEE 802.11 standard for wireless local area networking (WLAN) and rapid progress made toward higher data rates have put the promise of truly mobile computing within reach. While wired LANs have been a mainstream technology for at least fifteen years, WLANs are uncharted territory for most networking professionals.
In September of 1999, the Institute of Electrical and Electronic Engineers (IEEE) ratified the specification for IEEE 802.11b, also known as Wi -Fi. IEEE 802.11b defines the physical layer and media access control (MAC) sub layer for communications across a shared, wireless local area network (WLAN).
At the physical layer, IEEE 802.11b operates at the radio frequency of 2.45 gigahertz (GHz) with a maximum bit rate of 11 Mbps. It uses the direct sequence spread spectrum (DSSS) transmission technique. At the MAC sub layer of the Data Link layer, 802.11b uses the carrier sense multiple access with collision avoidance (CSMA/CA) media access control (MAC) protocol.
A wireless station with a frame to transmit first listens on the wireless medium to determine if another station is currentl y transmitting (this is the carrier sense portion of CSMA/CA). If the medium is being used, the wireless station calculates a random back off delay. Only after the random back off delay elapses can the wireless station again listen for a transmitting station. By instituting a random back off delay, multiple stations that are waiting to transmit do not end up trying to transmit at the same time (this is the collision avoidance portion of CSMA/CA). Collisions can occur and, unlike with Ethernet, they might not be detected by the transmitting nodes. Therefore, 802.11b uses a Request to Send (RTS)/Clear to Send (CTS) protocol with an Acknowledgment (ACK) signal to ensure that a frame is successfully transmitted and received.
2. Wireless Networking Components
IEEE 802.11b wireless networking consists of the following components:
Stations: A station (STA) is a network node that is equipped with a wireless network device. A personal computer with a wireless network adapter is known as a wireless client. Wireless clients can communicate directly with each other or through a wireless access point (AP). Wireless clients are mobile.
Wireless AP: wireless AP is a wireless network node that acts as a bridge between STAs and a wired network. A wireless AP contains:
1. At least one interface that connects the wireless AP to an existing wired network (such as an Ethernet backbone).
2. A wireless network device with which it creates wireless connections with
STAs.
3. IEEE 802.1D bridging software, so that it can act as a transparent bridge
between the wireless and wired networks.
The wireless AP is similar to a cellular phone network's base station. Wireless clients communicate with both the wired network and other wireless clients through the wireless AP. Wireless APs are not mobile and act as peripheral bridge devices that extend a wired network.
Ports: A port is a channel of a device that can support a single point -to-point connection. For IEEE 802.11b, a port is an association, a logical entity over which a single wire less connection is made. A typical wireless client with a single wireless network adapter has one port and can support only one wireless connection. A typical wireless AP has multiple ports and can simultaneously support multiple wireless connections. The logical connection between a port on the wireless client and the port on a wireless AP is a point -to-point bridged LAN segmentâ€similar to an Ethernet-based network client that is connected to an Ethernet switch.
3. IEEE 802.11b Operating Modes (network topology)
AP's are not mobile, and form part of the wired network infrastructure. A BSS in this Configuration is said to be operating in infrastructure mode.
IEEE 802.11 defines two operating modes: Ad hoc mode and Infrastructure mode. The basic topology of an 802.11 network is shown in Figure 1. A Basic Service Set (BSS) consists of two or more wireless nodes, or stations (STAs), which have r ecognized each other and have established communications. In the most basic form, stations communicate directly with each other on a peer-to-peer level sharing a given cell coverage area. This type of network is often formed on a temporary basis, and is commonly referred to as an ad hoc network, or Independent Basic Service Set (IBSS).
The Extended Service Set (ESS) shown in Figure 2 consists of a series of overlapping BSSs (each containing an AP) connected together by means of a Distribution System (DS). Although the DS could be any type of network, it is almost invariably an Ethernet LAN. Mobile nodes can roam between APs and seamless campus -wide coverage is possible.
4. IEEE 802.11b Operation Basics
When a wireless adapter is turned on, it begins to scan across the wireless frequencies for wireless APs and other wireless clients in ad hoc mode. Assuming that the wireless client is configured to operate in infrastructure mode, the wireless adapter chooses a wireless AP with which to connect. This selection is made automatically by using SSID and signal strength and frame error rate information. Next, the wireless adapter switches to the assigned channel of the selected wireless AP and negotiates the use of a port. This is known as establishing an association.
If the signal strength of the wireless AP is too low, the error rate too high, or if instructed by the operating system (in the case of Windows XP), the wireless adapter scans for other wireless APs to determine whether a different wireless AP can provide a stronger signal or lower error rate. If suc h a wireless AP is located, the wireless adapter switches to the channel of that wireless AP and negotiates the use of a port. This is known as reassociation.
Reassociation with a different wireless AP can occur for several reasons. The signal can weaken as either the wireless adapter moves away from the wireless AP or the wireless AP becomes congested with too much traffic or interference. By switching to another wireless AP, the wireless adapter can distribute the load to other wireless APs, increasing the performance for other wireless clients.
5. Radio Technology in 802.11
IEEE 802.11 provides for two variations of the PHY. These include two (2) RF technologies namely Direct Sequence Spread Spectrum (DSSS), and Freque ncy Hopped Spread Spectrum (FHSS). The DSSS and FHSS PHY options were designed specifically to conform to FCC regulations (FCC 15.247) for operation in the 2.4 GHz ISM band, which has worldwide allocation for unlicensed operation.
| Data
1 1 Bit Barker Cod** (PRN); 101 1101000
Figure 3 Digital Modulation of Data with PRM Sequence
DSSS systems use technology similar to GPS satellites and some types of cell phones. Each information bit is combined via an XOR function with a longer Pseudo -random Numerical (PN) sequence as shown in Figure 3. The result is a high speed digital stream which is then modulated onto a carrier frequency using Differential Phase Shift
Keying (DPSK).
When receiving the DSSS signal, a matched filter correlator is used as shown in Figure 4.The correlator removes the PN sequence and recovers the original data str eam. Tat the higher data rates of 5.5 and 11 Mbps, DSSS receivers employ different PN codes and a bank of correlators to recover the transmitted data stream. The high rate modulation method is called Complimentary Code Keying (CCK). The effects of using PN codes to generate the spread spectrum signal are shown in Figure 5.
As shown in Figure 5a, the PN sequence spreads the transmitted bandwidth of the resulting signal (thus the term, "spread spectrum") and reduces peak power. Note however, that total power is unchanged. Upon reception, the signal is correlated with the same PN sequence to reject narrow band interference and recover the original binary data (Fig. 5b). Regardless of whether the data rate is 1, 2, 5.5, or 11 Mbps, the channel bandwidth is about 20 MHz for DSSS systems. Therefore, the ISM band will accommodate up to three non-overlapping channels
6. Multiple Access
The basic access method for 802.11 is the Distributed Coordination Function (DCF) which uses Carrier Sense Multiple Access / Collision Avoidance (CSMA / CA). This requires each station to listen for other users. If the channel is idle, the station may transmit. However if it is busy, each station waits until transmission stops, and then enters into a random back off procedure. This prevents multiple stations from seizing the medium immediately after completion of the preceding transmission.
Figure 7 CSMA/CD Back-off Algorithm
Packet reception in DCF requires acknowledgement as shown in Figure 7. The period between completion of packet transmission and start of t he ACK frame is one Short Inter Frame Space (SIFS). ACK frames have a higher priority than other traffic. Fast acknowledgement is one of the salient features of the 802.11 standard, because it requires ACKs to be handled at the MAC sub layer.
The underlying assumption is that every station can "hear" all other stations. This is not always the case. Referring to Figure 8, the AP is within range of the STA -A, but STA-B is out of range. STA-B would not be able to detect transmissions from STA -A, and the probability of collision is greatly increased. This is known as the Hidden Node.
To combat this problem, a second carrier sense mechanism is available. Virtual Carrier Sense enables a station to reserve the medium for a specified period of time through the use of RTS/CTS frames.
7. IEEE 802.11 Security The IEEE 802.11 standard defines the following mechanisms for wireless security:
¢ Authentication through the open system and shared key authentication types
¢ Data confidentiality through Wired Equi valent Privacy (WEP)
Open system authentication is used when no authentication is required. Some wireless APs allow the configuration of the MAC addresses of allowed wireless clients. However, this is not secure because the MAC address of a wireless cli ent can be spoofed.
Shared key authentication verifies that an authenticating wireless client has knowledge of a shared secret. This is similar to preshared key authentication in Internet Protocol security (IPsec). The 802.11 standard currently assumes th at the shared key is delivered to participating STAs through a secure channel that is independent of IEEE 802.11. In practice, this secret is manually configured for both the wireless AP and client. Because the shared key authentication secret must be dist ributed manually, this method of authentication does not scale to a large infrastructure mode network (for example, corporate campuses and public plac es, such as malls and airports) for use.
Inherent in the nature of wireless networks, securing physical ac cess to the network is difficult. Because a physical port is not required, anyone within range of a wireless AP can send and receive frames, as well as listen for other frames being sent. Without WEP, eavesdropping and remote packet sniffing would be very easy. WEP is defined by the IEEE 802.11 standard and is intended to provide the level of data confidentiality that is equivalent to a wired network.
WEP provides data confidentiality services by encrypting the data sent between wireless nodes. WEP encryption uses the RC4 symmetrical stream cipher with either a 40-bit or 104-bit encryption key. WEP provides data integrity from random errors by including an integrity check value (ICV) in the encrypted portion of the wireless frame.
However, one significant problem remains with WEP. The determination and distribution of WEP keys are not defined and must be distributed through a secure channel that is independent of 802.11. Obviously, this key distribution system does not scale well to an enterprise organization.
Additionally, there is no defined mechanism to change the WEP key â€either per authentication or at periodic intervals over the duration of an authenticated connection. All wireless APs and clients use the same manually configured WEP key for multiple connections and authentications. With multiple wireless clients sending large amounts of data, it is possible for a malicious user to remotely capture large amounts of WEP cipher text and use cryptanalysis methods to determine the WEP key.
The lack of WEP key management, to both automatically determine a WEP key and change it frequently, is a principal limitation of 802.11 security, especially with a large number of wireless clients in infrastructure mode. The lack of automated authentication and key determination services also effects operation in ad hoc mode.
The combination of a lack of both adequate authentication methods and key management for encryption of wireless data has led the IEEE to adopt the IEEE 802.1X Port-Based Network Access Control standard for wireless connections
8. The Wireless Ethernet Compatibility Alliance
The recently adopted Complimentary Code Keying (CCK) waveform delivers speeds of 5.5 and 11 Mbps in the same occupied bandwidth as current generation 1 and 2 Mbps DSSS radios and will be fully backward compatible. Now that a standard is firmly in place, WLANs will become a part of the enterprise networking landscape within the next twelve months.
The mission of the Wireless Ethernet Compatibility Alliance is to provide certification of compliance with the IEEE 802.11 Standard and to ensure that products from multiple vendors meet strict requirements for interoperability. With cross vendor interoperability assured, WLANs are now able to fulfill the promise of hi gh speed mobile computing.
Conclusion:
The use of wireless LANs is expected to increase dramatically in the future as businesses discover the enhanced productivity and the increased mobility that wireless communications can provide in a society that is m oving towards more connectionless connections.
In conclusion, the panelists felt that hurdles in deploying WLANs can be overcome. Cost of wireless services are already falling. The issue is now to lower the costs of the device that is needed to access the WLAN. Large chop design companies can make use of this opportunity to get into the market place. And Wi -Fi cannot move ahead quickly without support form private and government sectors
Bibliography:
1. Data over wireless networks -Gilbert Held
2. Electronics for you (magazine) June 2003 & February 2003
3. Electronics today (magazine) March 2003
4. A Technical tutorial on the IEEE 802.11 protocol - Pablo Brenner
