1.0 Introduction
A computer network is regarded as a connection of computers and other similar devices in a specific configuration for the purpose of resource sharing. Software applications, files and folders, hardware such as printers and scanners, as well as internet connection are resources that can be shared on a network. Computer networks within a small geographical area such as a building are known as Local Area Networks (LANs) spanning a distance of not more than 100 metres. The connection of the devices are normally achieved with the use of wired connections, but wireless connections using free space as the medium of communication between the networked devices are also becoming more widely accepted. According to the IEEE 802.11 specification, the Wireless networks (WLANs) use free space as the medium of communication between networked devices.
Owing to the broadcast nature of wireless network signals through free space, a number of apparent disadvantages are inherent with the use of wireless networks as compared with the wired counterpart. These disadvantages border on security of the network on one part, and signal strength considerations as well as signal interference owing to the unbounded communication medium through air.
Despite the shortcomings of wireless networks, a number of measures can still be put in place to reinforce the security of the networks. They are also gaining popularity since they offer a lot of flexibility in deployment and use over the wired counterpart. A lot of applications are built around the use of wireless networks these days as they gain more acceptability among many more users.
This paper will expound on the components of wireless networks in section two, especially with respect to the IEEE 802.11 standards that defines the technology. Owing to the importance of the signaling techniques in avoiding signal interference, the different signaling techniques will also be discussed. The security risks associated with the use of wireless networks and the various methods and technologies that are being deployed to mitigate the risks discussed in section five, and finally, a number of applications and purposes that wireless networks are being deployed for will be discussed.
2.0 Components of a WLAN
A Wireless Local Area Network (WLAN) is basically composed of a wireless Network Interface Card (NIC) card or Peripheral Connect Interface (PCI) Adapter as used in desktop computers, a wireless Access Point (AP) or Base station and a wireless router.
2.1 Wireless NIC Cards
The wireless NIC cards can work in an ad-hoc mode which allows client-to-client connections or in a client-access point mode. The communication of a wireless NIC card in ad-hoc mode will depend on the 802.11 specification and the NIC product being used. Most wireless network cards are equipped with a plug and play capability, making them easy to set up.
2.2 Wireless Access Points
Wireless access points are connected to the wired part of the LAN through a connector. In the design of WLAN to cover a building, more than one AP may be needed to effectively cover the building depending on the transmission range of the AP device. The APs handle the transmission and reception of data with all the wireless devices within its range and can accomodate multiple devices at once.
3.0 The IEEE 802.11 Standard
The IEEE 802.11 protocol specifies the physical layer and the Media Access Control (MAC) layers of the WLAN with communication achieved over the 2.4 GHz and 5.0 GHz frequency bands. There are different specifications of the IEEE 802.11 wireless standard owing to difference in characteristics such as data rates, range of coverage, frequency of transmission etc. Some of these specifications are presented in table 1.
Some other characteristics of the IEEE 802.11 wireless LAN technology are presented in table 2.
Since the signals in wireless network communication are transmitted in free space, there is a very high likelihood that the signals will interfere with each other. There is a high chance of wireless communication signals interfering with other electronic devices such as a microwave oven which are not supposed to be a part of the wireless communication network. In order to avoid this situation, a number of signaling techniques have been defined to be used such as;
Direct Sequence Spread Spectrum (DSSS): transmitted data is spread over a large range of frequencies in the full bandwidth of the frequency band using an encoding scheme. This signaling technique has a longer range and higher throughput when compared with FHSS but it is less resistant to noise.
Frequency Hopping Spread Spectrum (FHSS): where a carrier signal hopping from one frequency to the other is used to transmit data. The order of the hops is known only between the transmitting and receiving devices. It has a lower throughput when compared with DSSS, but it is resistant to noise and easier to implement.
Orthogonal Frequency Division Multiplex (OFDM): data is encoded on multiple carrier frequencies with a higher bandwidth obtained when compared with the spread spectrum techniques.
5.0 Security in WLAN
WLANs also have security vulnerabilities that make them susceptible to security breaches especially owing to the broadcast nature of the signals. A good wireless network will be one that takes the vulnerabilities inherent in the nature of wireless networks into consideration and measures put in place to mitigate the risks.
Availability: the network infrastructure and resources must be available for the use of legitimate users when they need it
Authentication: verification of the identity of every user must be carried out to ensure that only authentic and legitimate users can access the network.
Integrity: integrity of the data as transmitted over the network must be such that the exact message that is sent by a sender is received without any modification by the intended recipient(s)
Authorization: ensures that access rights to the network are assigned to legitimate users.
Confidentiality: the confidentiality feature ensures that any information that is communicated over the network between a sender and a receiver must not be accessible to parties the information is not intended for consumption.
Non-repudiation: this ensures that any data transaction that takes place over the network can be later proved to have taken place truly.
Some of the vulnerabilities encountered in wireless networks can be traced to a number of factors including ease of access to the network as a result of the broadcast nature of wireless signals (Lackner, 2013) with connection only requiring being within range of the broadcast signal; inexpensive hardware to connect to wireless networks, and ignorance on part of users with acts that further expose the network to more risks.
Some of the security breaches encountered in wireless networks include eavesdropping, denial of ervice (DoS) attack, man-in-the-middle attacks etc.
5.1 Wireless networks security techniques
Owing to the broadcast nature of the signals in a wireless network through free space and the susceptibility of communication to interception by anybody with the right equipment within the broadcast range of the signals, securing the network from such intrusion can be a challenge. One way to prevent unauthorized access to the wireless network is to use authentication techniques before users are allowed access to the network (Karygiannis and Owens, 2002). In order to further prevent an unauthorized person from reading transmitted information over the network, information encoding is employed using cryptography. Authentication and cryptography are thus two major techniques of providing security in a wireless network.
5.1.1 Wireless Authentication
In wireless authentication, two major authentication schemes are used. These techniques are Wired Equivalent Privacy (WEP) and Wi-Fi Protected Access (WPA). In these two schemes, a shared secret key is used between the devices intending to establish communication.
In WEP, an alphanumeric key that is the same for all users of the network is sent by a device to the wireless router before it is granted access to the network. WEP is the most popular authentication technique used in wireless networks and the key used can be of varying lengths of 64 bits and128 bits. A longer authentication key means a stronger protection but may lead to slower data connection and information exchange (Al-Qasrawi and Al-Hazaimeh, 2013). WEP key security prevents eavesdropping and protects the confidentiality of user data.
The WPA technology is replacing WEP as it is offering stronger protection especially for WLANs that are using older hardware. WPA2 replaces WPA in order to completely address the shortcomings of WPA and provide the strongest cryptographic security for wireless networks. It may however require new hardware as it is not compatible with legacy systems.
5.1.2 Cryptography
Cryptography entails making sure that any information that is transmitted and gets intercepted by an unauthorized third party will not be readable to the interceptor. This security technique involves the transmission of a ciphertext which is obtained as the result of an encryption process achieved with the use of a key to transform a plaintext (Goel et al., 2013). In the encryption process, the key used is a short length of string which is known generally and may be changed as often as possible. The methods of encryption used in cryptography are basically classified into two categories from which other modern techniques are developed. These are substitution ciphers and transposition ciphers.
6.0 Applications
The applications of WLANs are unlimited as they find relevance in every sphere of business endeavour. Used widely in commerce especially POS terminals of retailers, warehouse inventory management, healthcare, hospitality to enhance the operations of these businesses (Malladi and Agrawal, 2002).
WLANs are deployed to make business processes easy. The proliferation of wireless devices means more employees in offices use hand-held devices such as tablets and other smart phones that they use in supporting their work. The provision of true nomadic access by WLANs makes the use of this networking infrastructure very convenient for workers (Boudriga, 2009) and thus increases the level of productivity.
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Karygiannis, T. and Owens, L. (2002). Wireless Network Security 802.11, Bluetooth and Handheld Devices. National Institute of Standards and Technology, Technology Administration U.S. Department of Commerce. PDF. Retrieved from http://csrc.nist.gov/publications/nistpubs/index.html. on 23rd January, 2016.
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