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AirPort

From Academic Kids

AirPort is a wireless networking system from Apple Computer based on the IEEE 802.11b (also known as Wi-Fi) standard and certified as compatible with other 802.11b devices. A later family of products based on the IEEE 802.11g specification is known as AirPort Extreme, offering speeds up to 54 megabits per second and interoperability with older products.

Somewhat confusingly, AirPort and AirtPort Extreme in common usage can refer to the protocol (802.11b and 802.11g, respectively), the expansion card or the base station.

In some markets the system is known as AirMac.

Contents

Overview

AirPort debuted on July 21 1999 at the Macworld Expo in New York. The initial offering included an optional expansion card for Apple's new line of iBook notebooks, plus an AirPort Base Station.

The original AirPort system allows transfer rates up to 11 Mbit/s. Antennas were integrated into the displays of iBooks, so reception was very good. Apple was the first manufacturer to embrace 802.11b wireless networking. The AirPort card was later added as an option for almost all of Apple's product line, including PowerBooks, eMacs, iMacs, and Power Macs. Only Xserves do not have an AirPort option.

On January 7th, 2003, Apple introduced AirPort Extreme, based on the 802.11g specification. AirPort Extreme allows data transfer of up to 54 Mbit/s, and (unlike the competing 802.11a) is fully backwards-compatible with the thousands of existing 802.11b base stations in coffee shops, retail stores, offices and homes. All of Apple's current computer models, with the exception of the XServe, have a slot to insert an AirPort Extreme card, and all models of PowerBook and iBook now ship with a card as standard. AirPort and AirPort Extreme cards are not physically compatible: AirPort Extreme cards cannot be installed in older Macs, and AirPort cards cannot be installed in newer Macs. However, AirPort Extreme devices can communicate both with other 802.11g-based devices as well as older 802.11b AirPort cards.

The original AirPort cards used Lucent's chipset, but unlike the Lucent WaveLan Silver Card (the equivalent 40-bit card) Apple released a firmware update to raise the encryption level to 128-bit (effectively giving a free upgrade to a Lucent WaveLan Gold card) in the spring of 2001. The original AirPort card was discontinued in June, 2004.

Base stations

Missing image
Apple_graphite_airport_base_station_front.jpg
Original graphite AirPort Base Station

An AirPort base station is used to connect AirPort-enabled computers to the internet, a wired LAN, or other devices.

AirPort

The original version (known as Graphite') features a modem and an Ethernet port and is based on the Lucent WaveLan PC-Card and used an embedded 486 processor.

A second generation model (known as Dual Ethernet or Snow) was introduced on 2001-11-13 which features two ethernet ports, one for LAN and one for WAN. It also added compatibility with America Online's dial-up service, making AirPort the only wireless solution to do so. This model is based on a Motorola PowerPC 860 processor.

AirPort Extreme

The AirPort base station was replaced by the AirPort Extreme Base Station on 2003-01-07. As well as the faster speed of Airport Extreme, it added an external antenna port and a USB port to connect a printer. The printer is then available to network users via Bonjour and IPP. A second, cheaper version was also available, lacking the modem and external antenna port, though it was discontinued in mid-2004 after the launch of the AirPort Express (see below). On 2004-04-19, a third version was introduced supporting Power over Ethernet and complying to UL 2043 fire regulations.

All AirPort Extreme models use an AMD Alchemy Au1500 processor which is based on the MIPS architecture.

AirPort Express

Missing image
Apple_airport_express.jpg
AirPort Express

The AirPort Express is a simplified and compact AirPort Extreme base station with a new feature called AirTunes. It did not replace the AirPort Extreme base station. It was introduced by Apple on 2004-06-07 and includes analog and digital audio outputs; a USB port for remote printing; and an ethernet port. The audio output is used for AirTunes functionality, which allows music to be streamed over a wireless network from iTunes. The AirPort Express can also be used to easily expand wireless coverage via WDS-bridging.

The main processor in the AirPort Express is a Broadcom BCM4712KFB wireless networking chipset. This has a 200MHz MIPS processor built in. The audio is handled by a Texas Instruments PCM2705 digital-to-analog converter.

The USB port on AirPort Express base can also be used to attach a Keyspan USB infrared remote control, to control AirTunes.

Security

In radio based networking, security is a critical aspect since it is possible to access the system from a distant location. As with most WLAN systems, radio network security is based on the Wired Equivalent Privacy standard which gives a number of inherent limitations and is considered by many in the security industry to have been "broken". The latest base stations, beginning with the AirPort Extreme, also offer WPA security. More important problems come in the management and default configuration of the Airport. After a reset, the base station enters a fully functional state but defaults to providing no encryption. The system provides for remote management and has a publicly known default1 password.

Even if the management password is securely updated to a secure value, it has been discovered that the management system uses a password which is sent across the network without encryption2. In response to this discovery Apple has stated that management of the Airport should be either by a wired connection or over a WEP encrypted network. Unfortunately, however, the system software gives no warning if the user accidentally, or through ignorance, begins remote management of the AirPort over an insecure network.

The installation manual included in the AirPort Extreme base station includes almost no instructions for security beyond the information on the default password and the location of the security slot which can be used for physically securing the base station using a cable lock. As of 2004 the AirPort web site also lacked obvious instructions or information related to AirPort security, however a the Manual Designing Airport Networks which is available for download there has a chapter devoted to security3. Another manual Managing AirPort Extreme Networks, also available from the support site includes a section on choosing encryption techniques4 and includes a comparison of the different techniques. These sections provide basic security advice, but do not fully cover certain risks; for example, the section on closed networks says that network users "must know the network name", but fails to mention the possibility of guessing.

On the IP networking side, the AirPort is by default configured to provide a NAT gateway and as such, the basic features of a stateful firewall. Whilst this does not provide full application level filtering, it does mean that a computer connected to the Internet through an AirPort base station will be better protected than it would be likely to be with a direct Internet connection.

If used by an experienced administrator with good security knowledge then an AirPort base station can be part of a solution which could provide a level of security acceptable in most applications. In a situation with an inexperienced user setting up a base station with little knowledge of WLAN security, the AirPort system could easily allow the easy configuration of an insecure wireless network with no warnings to the user.

References

  1. AirPort Extreme Base Station Setup Guide, Apple Computer Inc. Taiwan 1999 Page 20
  2. Apple AirPort Administrative Password Obfuscation Security Advisory  (http://www.atstake.com/research/advisories/2003/a051203-1.txt), Jeremy Rauch and Dave G. @stake, Inc, retrived 2003/12/05 from http://www.atstake.com/research/advisories/2003/a051203-1.txt 2004/12/29.
  3. Designing AirPort Networks (http://manuals.info.apple.com/en/airport/DesigningAirPortNetworks0190271.pdf), Apple Computing, 2004, retrieved 2004/12/29 from http://www.apple.com/support/airport/
  4. Managing AirPort Extreme Networks (http://download.info.apple.com/Apple_Support_Area/Manuals/hardware/Managing_AirPort_Extreme_Networks_v3.4.pdf), Apple Computing, 2004, retrieved 2004/12/29 from http://www.apple.com/support/airport/

External links

id:AirPort it:Famiglia AirPort he:AirPort ja:AirMac

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