Wi fi


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Wi fi

  1. 1. Wi – Fi B. Chandu Avinash B.Phanindra iii/iv B Tech iii/iv B Tech G V P College of engg. G V P College of engg vishakapatnam vishakapatnam ph:9290260573 e-mail:phani_bp@yahoo.co.in ABSTRACT What do writing in a diary, watching television, talking with friends, speaking on the telephone, and reading a menu have in common? They are all forms of communication. The word communication may be used to identify activities that do not involve people. Thus, communication may be defined as the means through which people exchange feelings and ideas with one another. While this definition is clear and simple, much more needs to be said. The new technology required for space exploration has had a major impact on communication in offices and homes. This technology has enabled business people to hold teleconferences with people in faraway cities. Computers and word processors are found in many offices. Electronic mail speeds business messages across continents, and electronic fund transfers give business managers great flexibility in managing money. A new revolution in communication was brought about with the advent of wireless technology. There were many developments in this field .there were infra red, blue tooth and now Wi-Fi. This paper mainly deals with the Wi-Fi, its networking components, operation modes, and operation basics, devices using it, security and finally pros, cons. 803.11b also called Wi-Fi (Wireless-Fidelity) promises to be the next big thing in wireless communication. Once limited to the domain of vertical market applications like inventory management, wireless LAN (often represented by same name Wi-Fi, which refers to the products based on IEEE standard 803.11b) is now rapidly expanding into horizontal markets. Large companies like Microsoft, as well as many universities use Wi-Fi extensively to provide notebook connectivity across multi-site campuses. WHAT IS WI-FI
  2. 2. Since 1999, wireless has simply been based on IEEE 802.11b; Wi-Fi is an open standard technology that enables you to build wireless connectivity between laptops and open area networks. Wi-Fi is trade name promulgated by the Wireless Ethernet Compatibility Alliance(WECA).The term Wi-Fi is used in place of 802.11b in same way that Ethernet is used in place of IEEE 802.3.Products certified as Wi-Fi compliant by WECA are inter operable with each other even if they are from different manufacturers. A user with Wi-Fi product can use any brand of access point with any other brand of client hardware is build to the Wi-Fi standard. Today’s Wi-Fi products, which transmit in the unlicensed spectrum of 2.5GHz, are capable of speeds up to 11 mpbs-about seven times faster than a typical T1 connection. Wi-Fi is the only wireless technology that will let you seemingly roam from work to home. Having been available in the corporate sector for some time now, Wi-Fi is now looking towards the home and small business. IEEE 802.11 and IEEE 802.11b standards 802.11b extends the original 802.11 standard which includes specification for 1mpbs and 2 mpbs wireless Ethernet transmission using spread spectrum RF signals in the 2.4 GHz Industrial, Scientific and Medical(ISM) band. the transmissions use 100milliwatts (MW) of transmitter power in North America (and less in other parts of world).In the original standard, two different spread spectrum transmission methods for physical layer (PHY) were defined: Direct sequence spread spectrum (DSSS) and Frequency hoping spread spectrum(FHSS).The 802.11b standard extends the original DSSS and PHY standard to provide a theoretical maximum data rate of 11 mpbs. Spread spectrum technology is a modulation technique that speeds data transmission across the entire available frequency band in prearranged scheme. This type of modulation makes the signal less vulnerable to noise interference and snooping. Spread spectrum technology also permits many users to share a frequency band with band with minimal interference from other users and from devices such as microwave ovens.
  3. 3. 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 currently 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. • 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.
  4. 4. • Wireless APs A wireless AP is a wireless network node that acts as a bridge between STAs and a wired network. A wireless AP contains: • At least one interface that connects the wireless AP to an existing wired network (such as an Ethernet backbone). • A wireless network device with which it creates wireless connections with STAs. • 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 wireless 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 segment—similar to an Ethernet-based network client that is connected to an Ethernet switch. OPERATION MODES IEEE 802.11 defines two operating modes: Ad hoc mode and Infrastructure mode. In ad hoc mode, also known as peer-to-peer mode, wireless clients communicate directly with each other (without the use of a wireless AP). Two or more wireless clients who communicate using ad hoc mode form an Independent Basic Service Set (IBSS). Ad hoc mode is used to connect wireless clients when a wireless AP is not present. In infrastructure mode, there is at least one wireless AP and one wireless client. The wireless client uses the wireless AP to access the resources of a wired network. The wired network can be an organization intranet or the Internet, depending on the placement of the wireless AP.
  5. 5. A single wireless AP that supports one or multiple wireless clients is known as a Basic Service Set (BSS). A set of two or more wireless APs that are connected to the same wired network is known as an Extended Service Set (ESS). An ESS is a single logical network segment (also known as a subnet), and is identified by its Service Set Identifier (SSID). If the available physical areas of the wireless APs in an ESS overlap, then a wireless client can roam, or move from one location (with a wireless AP) to another (with a different wireless AP) while maintaining Network layer connectivity. 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 such 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. You can achieve contiguous coverage over large areas by placing your wireless APs so that their signal areas overlap slightly. As a wireless client roams across different signal areas, it can associate and
  6. 6. reassociate from one wireless AP to another, maintaining a continuous logical connection to the wired network Devices using Wi-Fi While Wi-Fi may be widely used for communication between computers, there are PDA’s that support it. It’s also possible to add Wi-Fi support to a PDA inserting a Wi-Fi card into the SD (secure digital) slot. PDA’s such as the Toshiba e750 have inbuilt support for Wi-Fi .In march 2003,Nokia announced plans to build mobile phones that can seamlessly switch between 802.11b and public networks. 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 Equivalent Privacy (WEP) Open system authentication does not provide authentication, only identification using the wireless adapter's MAC address. Open system
  7. 7. 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 client 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 that 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 distributed manually, this method of authentication does not scale to a large infrastructure mode network (for example, corporate campuses and public places, such as malls and airports). Additionally, shared key authentication is not secure and is not recommended for use. Inherent in the nature of wireless networks, securing physical access 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. In practice, this is a text string that must be manually configured (using a keyboard) for both the wireless AP and wireless
  8. 8. clients. Obviously, this key distribution system does not scale well to an enterprise organization. Additionally, there is no defined mechanism to change the WEP key—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, where users might want to engage in peer-to-peer collaborative communication (for example, in areas such as conference rooms). 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. PROS & CONS Given the current situation, Wi-Fi should be adopted when there is a demand for high speeds on the move. Wi-Fi is suited for corporate with several executives roaming around the office with their laptops. Homes looking for the means to share a broad band internet connection can also consider adopting Wi-Fi. If you are buying a laptop, look for Wi-Fi enabled devices. A Wi-Fi setup is rather expensive when compared to regular LAN. Also, since Wi- Fi drains batteries much quicker, PDA user should avoid using it if they have the option of Bluetooth. It is difficult to provide security in a Wi-Fi network, as it is difficult to control the access to the network. CONCLUSION
  9. 9. Wi-Fi has all chances for huge growth, a strong value proposition, multiple uses, industry standardization; the global standardization .the technology flaws are not more than speed-breaker, as millions of dollars on R&D has already poured out. Lastly, there is plenty of space as one move from corporation-to the home-to the campus-to the airport-to-the-hotel and ultimately to a national wide level. This got to be the next big thing. REFERENCE BOOKS 1 .jeffduntemanns wi-fi guide –2nd edition 2. wi -fi home network-raymond smith 3.wi-fi hand book –frank ohrtman
  10. 10. Wi-Fi has all chances for huge growth, a strong value proposition, multiple uses, industry standardization; the global standardization .the technology flaws are not more than speed-breaker, as millions of dollars on R&D has already poured out. Lastly, there is plenty of space as one move from corporation-to the home-to the campus-to the airport-to-the-hotel and ultimately to a national wide level. This got to be the next big thing. REFERENCE BOOKS 1 .jeffduntemanns wi-fi guide –2nd edition 2. wi -fi home network-raymond smith 3.wi-fi hand book –frank ohrtman