Overview of Wireless Technologies

Wireless networking is amazingly useful, both on the job (so that you never have to play rock/paper/scissors over a limited number of Ethernet cables in a conference room), and even more so when traveling, enabling you to connect laptops and PDAs to the Internet in libraries, coffee shops, hotels, and many other public places. Wireless networking also provides an excellent mechanism for connecting networks of computers that are located in inaccessible locations or in existing structures where running new or additional cabling is a problem. Modulo security concerns, wireless networks can prevent the need to drill additional holes through Mount Vernon, the Vatican, or the Louvre.

Wireless networking refers to technology that enables a computer to communicate using standard network protocols, but without network cabling. Most commonly, wireless networks are local area networks (LANs) whose members use industry standards such as the Institute of Electrical and Electronics Engineers (IEEE) 802.11 to communicate. The original 802.11 standard was released in 1997, and defines the frequencies, data rates, and media access methods used to communicate between the participants in a wireless network. Subsequent standards have defined a potentially bewildering variety of 802.11X standards.

Regardless of the frequency and speed at which participants communicate, there are two basic types of wireless networks: ad hoc wireless networks and managed wireless networks. The characteristics of each (and their differences) are the following:

Ad hoc networks: Also referred to as peer-to-peer wireless networks, consist of some number of computers that each have a wireless networking interface card and that communicate directly with all of the other wireless computers on that network. This enables them to share files and printers, but will not provide access to wired or Internet network resources unless one (or more) of the computers is also connected to those other network resources and is configured to serve as a gateway, bridge, or router to the other network(s). Acronym fans may see Ad hoc networks referred to as IBSS (Independent Basic Service Sets) during the computer bowl.

Managed networks: Also referred to as infrastructure wireless networks, use an access point (sometimes also referred to as a base station) to manage communication between multiple wireless computers, acting much like a hub or switch for the wireless network. An access point is also typically connected to a wired network such as the Internet, and serves as the bridge or gateway between the wireless and wired networks. Access points are traditionally dedicated hardware devices (sometimes referred to as a HAP, a Hardware Access Point), such as Apple’s Airports or devices from companies such as LinkSys, NetGear, Cisco, and others, but can also be software solutions (referred to as SAPs, Software Access Points) that run on a computer that is equipped with both wired and wireless network connections. Acronym fans may see managed networks referred to as a BSS (Basic Service Set; N computers and one access point) or ESS (Extended Service Set; N access points and N computers forming one subnet) during the computer bowl.

Large areas that require wireless coverage can accomplish this by providing multiple access points and supporting roaming, which is the ability of a user’s connection to transfer from one access point to another. This is usually invisible to the user, though some access points require passwords or other authentication when moving between access points. Many networking hardware vendors also provide specialized hardware known as extension points that amplify the signal and therefore extend the range of an existing access point. Whether or not hardware access points support roaming or extension points is dependent on the hardware manufacturer. As with most networking hardware, a good rule of thumb is that buying all of your network hardware from the same vendor increases your chances for compatibility.

Agreement between the low-level wireless networking standards that the computers in your wireless network use is the most important aspect of setting up a successful wireless network. If the computers and access points can’t communicate in the first place, you aren’t going to be setting up much of anything. Though IEEE 802.11 is a published standard for wireless communication, several different 802.11 protocols and associated standards exist, not all of which are compatible with each other. The following is a current list of popular 802.11 standards, communication speeds, and compatibility promises:

802.11a: A standard for 802.11 communications using the regulated 5.0 GHz frequency, offering maximum communication speeds of 25 to 54 Megabits per second. It is not compatible with any other 802.11 standard.

802.11b: A standard for 802.11 communications using the unregulated 2.4 GHz frequency, offering maximum communication speeds of 5 to 11 Megabits per second. The 802.11b standard is forward compatible with the 802.11g and proposed 802.11n standards.

802.11g: A standard for 802.11 communications using the unregulated 2.4 GHz frequency, offering maximum communication speeds of 25 to 54 Megabits per second. The 802.11g standard is backward compatible with the 802.11b standard and forward compatible with the proposed 802.11n standard.

802.11n: A standard for 802.11 communications using the unregulated 2.4 GHz frequency, offering maximum communications speeds of 100 to over 200 Megabits per second. The 802.11n standard is designed to be backward compatible with the 802.11b and 802.11g standards.

Wireless networks also support a variety of security solutions, ranging from network names to encryption mechanisms. The most common of these are the following:

MAC (Media Access Control) filtering: A security mechanism that requires that access points be programmed with lists of the systems that can connect to them, identified by hardware Ethernet address. MAC security only prevents against unauthorized connections to an access point—it does not secure those communications, once established.

SSID (Service Set IDentifier): An SSID acts as a simple password by providing a unique identifier for a specific wireless network. Access points with a specific SSID can be configured to disallow access to anyone who does not provide that SSID when negotiating the initial connection. SSID security only prevents against unauthorized connections to an access point—it does not secure those communications, once established. An Extended Service Set IDentifier (ESSID) is just an SSID that is (or can be) used on multiple access points to identify the same network.

WEP (Wired Equivalent Privacy): A security mechanism that requires supplying a 48-, 64-, or 128-bit security key when negotiating a connection to an access point. This key is used for encrypting and decrypting wireless communications. If this key is the same as that used by the access point, the two can communicate successfully. WEP security protects against unauthorized access and also provides secure wireless communication, because all communication packets are encrypted.

WPA (WiFi Protected Access): A security mechanism that uses a Temporary Key Integrity Protocol to replace WEP and provides enhanced security on existing hardware. WPA uses a key server or pre-generated key set to encrypt communications on a per-packet basis. Two different WPA standards exist: WPA1, which was developed using a draft of the IEEE 802.11i security standard, and WPA2, which was developed using an approved version of the 802.11i security standard. WPA is not currently supported by all Ubuntu wireless applications, but is the next big thing for wireless network security.

All of these security measures can be used together, in any combination, or separately. Only WEP and WPA provide security for the packets that are being transmitted, but typing in a 128-bit key each time you configure a new wireless interface is both error-prone and incredibly tedious. Many sites therefore use MAC and SSID/ESSID security to establish connections, and then protect transmitted packets by using standard SSH tunneling or VPN technologies on top of the wireless communication layer.

Source of Information : Ubuntu Linux - Bible

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