Whether mono-spaced bold or proportional bold, the addition of italics indicates replaceable or variable text. Italics denotes text you do not input literally or displayed text that changes depending on circumstance. To connect to a remote machine using ssh, type ssh username domain. If the remote machine is example. The mount -o remount file-system command remounts the named file system.
To see the version of a currently installed package, use the rpm -q package command. It will return a result as follows: package-version-release. Note the words in bold italics above — username, domain. Each word is a placeholder, either for text you enter when issuing a command or for text displayed by the system. Aside from standard usage for presenting the title of a work, italics denotes the first use of a new and important term. Publican is a DocBook publishing system. Pull-quote Conventions.
Terminal output and source code listings are set off visually from the surrounding text. Output sent to a terminal is set in mono-spaced roman and presented thus:.
Source-code listings are also set in mono-spaced roman but add syntax highlighting as follows:. Notes and Warnings. Finally, we use three visual styles to draw attention to information that might otherwise be overlooked.
Notes are tips, shortcuts or alternative approaches to the task at hand. Ignoring a note should have no negative consequences, but you might miss out on a trick that makes your life easier. Important boxes detail things that are easily missed: configuration changes that only apply to the current session, or services that need restarting before an update will apply.
Ignoring a box labeled 'Important' will not cause data loss but may cause irritation and frustration. Warnings should not be ignored.
Ignoring warnings will most likely cause data loss. Please select the proper component for this guide. Chapter 1. Due to increased demand for convenient networking and more flexible access to both the Internet and company resources via more geographically widespread coverage areas, wireless networking use has dramatically increased in recent years.
Mobile access to data services previously unavailable is now common. The sales and penetration of wireless access have resulted in a recent projection by ABI Research that one billion Wi-Fi chipsets will ship in the year Not only has wireless data access achieved a great deal of market penetration in recent years, but the price of the related hardware has dropped dramatically, making it even more accessible. Wi-Fi seems to be everywhere; in laptops, desktops, PDAs, cell phones and routers, and there is such a large amount of wireless networks in many urban areas that complete overcrowding of the public radio spectrum in use can occur.
This guide provides a high-level overview of the past, present, and future of IEEE Although the specific wireless technology based on IEEE Parts of this guide contain detailed information specific to Fedora Documentation and other Linux operating systems, however, many of the topics and concepts relate to all operating systems, vendors, and environments. You should read this guide if you are looking for an overview of wireless technologies and how they are implemented in Fedora Documentation or other Linux operating systems.
Other readers will gain general information on how wireless works, the hardware involved, and other topics such as standards and security. A wireless LAN referred to as WLAN in this guide is a wireless local area network that allows computers or other devices to communicate via radio frequency RF technology. It affords the user mobility to move around and stay connected to the network without using physical cables such as in a traditional Ethernet system.
The IEEE Institute of Electrical and Electronics Engineers is a non-profit, global organization which implemented and continually develops a set of standards for wireless communication. This family of standards is known as IEEE Standards are discussed in more detail later.
Although wireless networks are commonly referred to as Wi-Fi, this is only a marketing term chosen by the Wireless Ethernet Compatibility Alliance now known as the Wi-Fi Alliance. History of Wireless LANs. Although wireless communications are nothing new, Norman Abramson, as a professor at the University of Hawaii, led the development of what is acknowledged as the first computer network using wireless communications, in Known as ALOHAnet, it enabled wireless communication between a small set of islands and pioneered today's wireless networks, as well as lending concepts to Ethernet development.
With more available devices, higher data rates and cheaper hardware, wireless access has now become widespread. The IEEE recently ratified This amendment addresses several performance and security issues and is covered later in this guide.
Benefits of Wireless LANs. Wireless LANs offer mobility and convenience, allowing connections from nearly any location within the coverage area. Also, the installation of a WLAN is in many cases easier than a wired network, because of the lack of a need to install actual cables in wall fittings and data centers.
A properly designed WLAN can be installed relatively quickly and can also be transported to a new location more easily. Wireless LANs introduce several deployment and usability factors that should be considered. An Ethernet system generally has its electrical current traveling neatly bounded inside a wire.
The performance and reliability of a wireless LAN is dependent on atmospheric conditions, physical obstructions, other WLANs, RF interference, RF propagation characteristics and the basic laws of physics. The use of a WLAN is therefore generally not as reliable or as fast as a wired system, however recent developments in the communications standards that actually use some of these atmospheric anomalies to their advantage have alleviated the problems to a degree.
The reliability and performance of a WLAN depends on correct deployment which has all of these conditions taken into account. Security concerns are also a factor. A WLAN spreads to coverage areas outside that of a controlled wired system, and is much less predictable. For instance, many wireless networks used in the home can be detected from the street outside. A business may inadvertently make their network available to a competitor in an adjacent building.
Hence, several security mechanisms exist for IEEE These are covered later. Linux Wireless Support. Linux supports many wireless devices. Many of these adapters are supported by default in the Linux kernel via open source drivers available in Fedora Documentation. Your device is most likely supported; however, to find an overview of devices and drivers currently supported in Linux and Fedora Documentation, refer to the following URL at Linuxwireless.
Any products pictured or otherwise referred to in this guide are provided for reference purposes only, and no endorsement or guarantees of supportability are intended.
Chapter 2. Standards Defined. The WLAN and radio communications industries are regulated by several different organizations. These bodies develop and implement standards and regulations that include limits on factors such as power output, antenna height, hardware compatibility, frequency allocation and usage and general spectrum management. This chapter gives an overview of these bodies and their responsibilities.
Note that local regulations may exist in your area that may differ from those listed here. When deploying a WLAN, the requirements of your local regulatory domain authority should always be adhered to. Standards and Regulatory Bodies. The ITU-R manages worldwide spectrum management and satellite orbits and keeps the interference-free operation of communications as its primary objective. Wi-Fi Alliance - A non-profit, worldwide association consisting of more than member companies from more than 20 countries.
This is done by performing a series of certification testing on products. IEEE - The Institute of Electrical and Electronics Engineers is a global, non-profit organization, with more than , members from more than countries.
The IEEE is a professional group working towards the advancement of technology, to "foster technological innovation and excellence for the benefit of humanity. The More information about the IEEE and the Equipment that conforms to this standard is considered legacy and is no longer being manufactured.
It is, however, considered the baseline for IEEE The most recent revision of the This standard sparked a huge increase of WLAN adoption, and is considered as one of the main catalysts for the popularity of Wi-Fi today. Equipment that operates under this standard is not compatible with The higher frequency in use by Equipment conforming to this As it uses the same 2.
Devices operating under the This technology uses multiple antennas and multiple wireless connections to achieve these rates, and is much more resistant to interference without requiring a significant increase in power used to transmit the data. MIMO also presents the ability to use multipath an atmospheric anomaly where a single signal takes different paths and arrives at the receiver at slightly different times, causing a negative factor on performance when using older standards to its advantage.
Many products existed on the market before the standard was fully ratified; often known as "Pre N" or "Draft N", these devices are not guaranteed to fully operate under, or be compatible with, specifications of the completed standard.
These draft devices are also not guaranteed to be compatible across differing vendors. At the time of writing, there are concerns that Chapter 3. Hardware And Communication. This chapter gives an overview of some of the hardware available for wireless LANs, the role they play, and further details about their operation.
Components of a Wireless LAN. In order for successful communications to take place in a WLAN, certain hardware is needed. The hardware can be generally categorized as being a transmitter , antenna , a receiver , or a combination of these. Transmitter - A transmitter, as an active device, initiates an electromagnetic signal, beginning the wireless communication process. Usually, a transmitter sends this signal to an antenna after the data has been received by the originating station ie.
Specifically, it can propagate a signal after it has been received from a transmitter as an AC signal and then passively creates the waveform for it to travel through the air. The actual shape and path that the electromagnetic waves take depends on the type of antenna, its intended purpose and its desired coverage area. An antenna also performs the reverse of this operation by receiving signals and passing them along to a receiver.
Receiver - A receiver completes the electromagnetic communications in a WLAN by taking a signal usually from an antenna and passing it to the computer in a way it can understand such as binary 1s and 0s. Types of Cards. Wireless client adapters allow desktop and mobile computers to join and communicate on a WLAN. They can be quickly set up and transferred between machines. The antenna is built into an integrated unit and the adapters are approximately the same size as a USB flash memory adapter:.
They typically have an external antenna attached, and provide support for connecting antennas for specific signal requirements, or for increased signal strength:. Types of Antennas. There are three main antenna categories available for wireless LANs: Omnidirectional , Semidirectional and Highly directional. Omnidirectional - Omnidirectional antennas are designed to radiate a signal in all directions.
Although it is impossible under the basic laws of physics for an antenna to perfectly radiate a signal in all directions at equal strength, an antenna of this type is an attempt to provide general coverage in all directions.
This is the most common type found for client adapters and access points, as in these situations, good coverage in a general spherical area around the antenna is desirable. Semidirectional - Semidirectional antennas are designed to provide specific, directed signal coverage over large areas. An example of a semidirectional antenna is a Yagi antenna. Highly-directional - Highly directional antennas are used for point-to-point links; for example, between two buildings.
They radiate a very narrow beam over a long distance, and are often used for dedicated links. Connection Modes. Clients typically connect in one of two modes: adhoc or infrastructure.
Adhoc mode involves stations communicating directly with each other without the need for a central point to manage communications. This is also known as peer-to-peer mode. The default and most common mode is known as Infrastructure mode. Infrastructure mode uses a Wireless Access Point WAP , which is a central device that manages transmissions between clients. Refer to the following for more details on Access Points:.
From Wikipedia. The WAP usually connects to a wired network, and can relay data between the wireless devices such as computers or printers and wired devices on the network. Access points commonly found in home environments provide different features from those found in business or corporate settings. Consumer-level WAPs are often integrated into broadband gateways, and multiple functions can be served from a single device.
These functions typically include a switch for wired access, routing functionality, a broadband modem, and a network firewall. Usually an omnidirectional antenna is used, or multiple antennas, a scheme known as antenna diversity. WAPs often have a built-in web interface for their configuration which can be accessed by a web browser.
In fact, the signals for these devices can operate on one of eleven 11 distinct sections or channels within the 2. Some regions allow operation in thirteen 13 channels, however the U. S FCC defines eleven 11 channels. What this means is that you can configure your wireless adapter and access point to operate on slightly different frequencies than other networks in your area, to avoid interference and congestion.
Each of these channels cover a frequency range of 22MHz; in other words, a device operating in each of these channels can operate at up to 11MHz on either side of the "center" frequencies listed in the following table.
Table 3. IEE Channels that are separated by at least five other channels or at least 2. You can use this important piece of knowledge when you have wireless congestion issues; for example, in an apartment building with three wireless networks near each other, you can avoid congestion by getting the networks to run on channels that are sufficiently separated from each other, such as 1, 6 and A heavily congested area may not provide the freedom to do this, however it is a useful thing to remember.
Chapter 4. Best Practices. This chapter covers the security concerns and features of IEEE Unique Challenges. As described in Section 1. This introduces several challenges to effective security. The standard security model known as CIA, or Confidentiality , Integrity and Availability can be applied to the unique elements of wireless data transmission. This three-tiered model is a general framework for assessing risks to sensitive information and establishing security policy.
Confidentiality - This part of the CIA model states that sensitive information must be available only to a set of pre-defined individuals, and unauthorized transmission and usage of information should be restricted.
This element of the CIA model is worthy of attention when using a WLAN simply because the radiated signal can easily travel beyond the traditional borders of the network, through walls and other fixtures, and can become available to unauthorized users much more easily.
This is especially true when using no encryption, weak encryption or if the network has other design flaws. Integrity - This part of the model states that information should not be altered in ways that render it incomplete or incorrect, and unauthorized users should be restricted from the ability to modify or destroy sensitive information.
Much like the confidentiality element, affording unauthorized users a greater opportunity to intrude on the network can compromise the level of integrity of data. Data integrity checks are also integrated into the communication and encryption mechanisms used. Availability - This part of the CIA model states that information should be accessible to authorized users any time that it is needed. Availability is a warranty that information can be obtained with an agreed-upon frequency and timeliness.
This element applies to all networking equipment - that a network service is available when needed, and it is no different for wireless equipment. Sufficient knowledge of the hardware and how a wireless LAN operates at a low level is important in order to provide reliable, timely network capabilities, especially in a complicated environment and where reliability is crucial.
Wireless networks broadcast messages using radio and are thus more susceptible to eavesdropping than wired networks. When introduced in ,[1] WEP was intended to provide confidentiality comparable to that of a traditional wired network. Beginning in , several serious weaknesses were identified by cryptanalysts with the result that today a WEP connection can be cracked with readily available software within minutes.
The WEP protocol does not provide any support for key management mechanisms, and in most environments the same key is shared by many clients. In an environment where keys are not changed regularly, this can compound the problem of using WEP as a flawed protocol. WEP uses keys that must be shared by both the client and the access point as all stations that want to send or receive must know the key. These keys are commonly referred to as being 64 or bits long. In fact, the actual keys are either 40 or bits long, and the remaining 24 bits in either configuration represent what is called the Initialization Vector IV.
This IV is used in combination with the key to encrypt the actual data. The implementation of the mechanisms used to combine the IV and the secret key in the WEP protocol has several flaws which can make the recovery of the keys by a malicious user simple:. Short IV length - The 24 bits reserved for the IV do not allow for sufficient cryptographic complexity. IV is sent in cleartext - The IV is sent in cleartext unencrypted over the network.
Weak IVs - Some of the generated IVs do not provide enough randomness and these can be used to extract the key. The IV is part of the encryption key - As an attacker can see 24 bits of every key in cleartext without any effort, it becomes a basic mathematical process to deduce the rest of the key. WEP is now considered an outdated algorithm and is not recommended for use; however, it should be noted that many of its shortcomings arise from it simply being a poor implementation of its underlying mechanisms, and does not necessarily indicate that the actual mechanisms are inherently flawed.
Dedicated authentication methods - WPA introduced the ability to use These operate as a dedicated authentication mechanisms for users, ie. With the growth of wireless networks worldwide, enabling secure communications is of utmost importance. Using WPA preferably WPA2 with the AES algorithm is the recommended way to encrypt your wireless network, and although some brute force attacks on WPA using the TKIP algorithm are becoming available, using a randomized, strong key, following a layered approach to security and employing secondary techniques to securing your wireless LAN beyond relying solely on encryption will alleviate these risks to a large degree.
Due to the fact that broadcom use proprietary drivers for their wireless modules it is not usually possible for them to work out of the box with Fedora. This tutorial is aimed at helping you to get the adapter working.
The process itself can be quite simple, but I am aware of some pitfalls that you may come up against in some cases. I know how to get around some of these. With this in mind I will try to highlight potential problems and their fixes as we go through. Once the system has booted and you have logged in again we need to check if the driver "broadcom-wl" has installed.
Obviously the the actual driver version might be slightly different to the output below, but you should get a similar response. There is a chance that you will get a warning that "files needed for building modules against kernel could not be found" and "Is the correct kernel devel package installed? If that is the case don't worry, just continue. First check the system:.
If they are the same you can skip to the "Load the "wl" module" part just after the system restart in red below, otherwise you need to do the following.
You now need to install the correct kernel devel for your system.
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