Running Free with Linux
By Roman Vichr2005-04-21
Interoperability Issues
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The interoperability of various cards with Linux drivers is an important consideration when deploying wireless on a Linux platform. You should also ensure the interoperability of the various hardware pieces themselves; they should all understand each other's signals within the same spectrum. Don't forget that products that appear to be similar might not be. For example, 802.11 and 802.11-FH products are not interoperable with 802.11-DS products, and vice versa.
Chipsets
The use of various chipsets in different wireless products can be a challenge, given that some cards might be supported and others of the same brand might not be. Sometimes, even cards with the same model number can have different chipsets, which makes it difficult to determine if a card is supported under Linux. However, most of the available 802.11b cards use the Intersil PrismII chipset, which is well-supported under Linux.
The 802.11b specification is just an extension of 802.11-DS, which enhances speed, but the products are always interoperable at least at 2 Mbs (802.11-DS mode). The 802.11g standard is a non-straightforward extension of 802.11b; its purpose is to increase bandwidth on the same frequency.
When you try to make 802.11a products interoperate (at 5 GHz), be aware that they are interoperable themselves based on the exact same chipset, but they do not directly interoperate with 802.11b products unless you have a device that works with both 802.11b and 802.11a. For a good review of interoperability of Wi-Fi frequencies and standards, read The 802.11g standard -- IEEE and The ABCs of 802.11.
When considering your Linux wireless device drivers, remember that the driver does not always implement all the features of the corresponding Windows driver. This limits the interoperability. Security features in particular tend to lag behind on Linux. The next section looks at some of the details on enhancements and management.
Networking Flexibility and Wireless Initiatives
To enable wireless network flexibility and ensure security, several initiatives have been launched such as the Wireless FreeNetwork Allocations and NodeDB.com (see Resources for more information). Essentially, these are sites where people can list their location and information about access points or fixed client connections so others can easily locate them based on a geographic directory service.
The spirit of Linux -- its openness and user-as-owner and manager ethos -- exerts its influence in several wireless initiatives, regardless of whether Linux is actually part of the solution. In some, like NodeDB.com, Linux is just one of the platforms. In the WIANA and NoCatAuth initiatives, it is the backbone of the initiatives due to the ability of user customization right at the operating system; that is, at the access point level.
WIANA
The Wireless Assigned Numbers Authority, also known as the WIANA initiative (see Resources for more information), is attempting to create a structure for wireless address management. Traditional IP address registries depend on static hierarchical structures, which are not sufficient for wireless. WIANA has to address the ad-hoc character of wireless networks, where nodes can move from one hierarchy to another simply by virtue of their location. Under WIANA guidelines, users, not providers, govern the networks. Large-scale wireless networks are based on a physical medium that is different from the traditional Internet, which requires actual per-address authentication. The high connection fees in the traditional Internet prohibit wireless users from taking the same approach to obtaining IP addresses. Under WIANA, these addresses are provided free of charge. WIANA also seeks to centralize the handling of abuse and blocking. WIANA supports compatible wireless software and hardware under the mission statement provided by LocustWorld.com. The hardware and software is designed to be fully compatible under 802.11 Wi-Fi on any platform. The main idea is to provide open community wireless WANs, which are governed by the users themselves, to give users more flexibility.
NoCatAuth
You can put the initiative called NoCatAuth into a similar category. It was initially built to support 802.11b wireless networks in Sonoma County, California. This implementation approach centralizes the authentication code that makes shared Internet services to one point possible (similar to WIANA efforts). In order to use the NoCatAuth under an open source license, the Perl programming language, GNU make, and gpgv must be installed on your Linux system.
Tutorial Pages:
» A Variety of Tools and Projects Help Get Wireless Linux Off the Ground
» A Linux Wireless Access Point: Build or Buy?
» Friendly Tools
» Interoperability Issues
» Linux's Wireless Future
» Resources
First published by IBM DeveloperWorks
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