AirPort
`
`Wireless Networking
`A Technical Overview
`
`Understanding and Using
`AirPort Networks
`AirPort 1.1
`
`Microsoft Corp. Exhibit 1049
`
`

`

`Contents
`
`2 Introduction
`
`3 AirPort Products
`
`5 AirPort Software
`
`8 AirPort Features
`
`12 Using AirPort Networks
`
`16 AirPort Networking Examples
`
`19 AirPort Administration
`
`24 Conclusion
`
`25 Appendix: Glossary
`
`Microsoft Corp. Exhibit 1049
`
`

`

`2
`
`Introduction
`
`With the introduction of Apple’s AirPort
`technology, wireless networking has
`become an option for users who want
`the benefits of wireless functionality
`without the complications. The informa-
`tion in this paper complements the
`AirPort manual by providing technical
`insight into AirPort and wireless
`networking in general.
`
`Now there’s a simple, affordable way to bring the Internet to a home, classroom, or small
`business—without cabling, additional phone lines, or complicated networking hardware.
`AirPort, Apple’s 11-megabit-per-second (Mbps) wireless local area network (LAN) technology,
`enables fast and reliable wireless communications between multiple computers and the Internet.
`AirPort is a fully integrated hardware and software solution designed to work optimally and
`seamlessly with Macintosh computers.
`
`Because AirPort is simple to set up and easy to use, it’s an ideal solution for working, playing,
`or collaborating over the Internet. The fast transfer rate—up to 10 times faster than other home
`networking products—means that AirPort can easily handle the most demanding Internet file
`sharing or multiplayer gaming. AirPort allows multiple computer users to simultaneously access
`different websites and email through a single Internet connection. Users of AirPort-enabled
`computers can also exchange files without floppy disks or other media.
`
`AirPort is based on the IEEE 802.11 Direct Sequence Spread Spectrum (DSSS) worldwide
`industry standard, so it allows for interoperability with other 802.11-based equipment. It uses
`radio frequency technology that enables it to communicate even through solid objects such
`as walls.
`
`Microsoft Corp. Exhibit 1049
`
`

`

`AirPort Products
`
`3
`
`There are two products in the AirPort product line: an AirPort Card that goes into each computer
`and an AirPort Base Station that communicates with nearby AirPort-enabled computers and the
`wired network or Internet.
`
`AirPort Card
`The 11-Mbps AirPort Card is available for all new Macintosh computers—iBook, iMac, PowerBook,
`and Power Mac G4. The credit-card-size card is user installable and comes with all the software
`needed to set up and operate an AirPort network. The same card is used in all AirPort-ready
`computers.
`
`AirPort Base Station
`Similar to the base station of a cordless telephone, the AirPort Base Station uses a physical
`connection to access the Internet and wireless connections to communicate with the AirPort-
`enabled computers. The base station has an RJ-11 connector for the built-in 56-kilobit-per-
`second V.90 modem.* There is also an RJ-45 connector for the built-in 10BASE-T Ethernet
`connection that allows users to connect to Ethernet or a DSL modem.
`
`Two software tools are available to configure the base station: the AirPort Setup Assistant for
`simple network setup and the AirPort Admin Utility for advanced, custom configurations. The
`Setup Assistant uses the computer’s active Internet access settings to configure the wireless
`network settings. The utility can be used to modify the base station’s previous Internet access
`settings or to enter new settings.
`
`AirPort Software Base Station feature
`Instead of purchasing a separate hardware base station, you can use an AirPort-enabled com-
`puter to provide Internet access to other AirPort-enabled computers. A computer that is set up
`to function in this way is known as a software base station. The software base station allows an
`AirPort-enabled computer to act as a base station for an AirPort network. The software directs
`the data to and from other computers on the wireless network and out to the Internet through
`a simple network by acting as a router.
`
`In this scenario, when an AirPort-enabled computer wants to access the Internet, it establishes a
`connection with the software base station. The software base station then establishes the Internet
`connection (through the computer’s modem), and routes the wireless TCP/IP Internet traffic
`between the Internet service provider (ISP) and the AirPort-enabled computers on the network.
`The user capacity of the software base station network depends on the speed of the computer
`that has the software base station enabled and the speed of the network connection.
`
`*Actual modem speeds lower; speed depends on connection rate and other factors.
`
`Microsoft Corp. Exhibit 1049
`
`

`

`AirPort
`AirPort Products
`
`4
`
`Users enable the software base station feature through the Setup Assistant or AirPort applica-
`tion. Once you have set up your computer to function as a software base station, you can easily
`turn the software base station on and off using the Control Strip.
`
`The software base station–enabled computer must be on and not in sleep mode for the soft-
`ware base station software to work. If you stop your computer from functioning as a software
`base station, all computers currently connected to the software base station will be discon-
`nected from the network.
`
`Microsoft Corp. Exhibit 1049
`
`

`

`AirPort Software
`
`5
`
`Apple is a leader in making advanced technology easy to use—and AirPort is no exception.
`Because Apple designs and integrates both the hardware and software, users will find that
`AirPort is simple to set up and easy to use.
`
`AirPort Setup Assistant
`The AirPort Setup Assistant steps users through the basic AirPort setup. For the majority of
`users, the Setup Assistant is the primary method of configuring AirPort. With the Setup
`Assistant, users can:
`
`• Configure their computer to access an AirPort network.
`• Set up a base station for Internet access via dial-up, Ethernet or a DSL modem.
`• Set up a software base station.
`• Transfer the Internet settings from their computer to the AirPort Base Station.
`• Change the base station Internet settings.
`
`Microsoft Corp. Exhibit 1049
`
`

`

`AirPort
`AirPort Software
`
`6
`
`AirPort Control Strip
`The Control Strip allows users to quickly check the quality of their wireless network connection.
`It monitors the signal-to-noise ratio of the connection and indicates the relative signal quality
`by the number of circles that are illuminated green. A strong and clear signal has all five circles
`illuminated while a weak or noisy signal may only have one circle illuminated. The Control Strip
`also allows a user to:
`
`• Quickly open the AirPort application.
`• Turn AirPort functionality on or off. This capability allows the user to comply with an airline’s
`request to turn off radio devices onboard an airplane.
`• Select the desired AirPort network among available choices. Users can quickly scan a list of the
`networks in the computer’s range and choose one of them. There’s no need to restart a com-
`puter or type in a wireless network name—just select a network name from the list and enter
`the password if required.
`• Establish a computer-to-computer AirPort connection to transfer data directly between
`computers.
`
`AirPort application
`The AirPort application allows users to:
`
`• Dial the modem in the base station to connect to the Internet.
`• Monitor modem status.
`• Hang up the dial-up modem on the AirPort Base Station.
`• Turn AirPort functionality on or off.
`• Select the desired AirPort network among available choices.
`• Select a “closed” third-party network if the user knows its name and password.
`• Determine the AirPort ID of both the computer and the base station.
`
`Microsoft Corp. Exhibit 1049
`
`

`

`AirPort
`AirPort Software
`
`AirPort Admin Utility
`While the Setup Assistant is the primary tool for users to easily configure their base station for
`simple networking scenarios, the AirPort Admin Utility is the administrative tool used to set up
`and manage more complex networks. The Admin Utility can program base stations both wire-
`lessly and over the Ethernet (either through the network or using a crossover cable). The
`Admin Utility allows network administrators to:
`
`• Change the base station name and password.
`• Change the network name and password.
`• Set the channel on which the base station will operate.
`• Plan a network by using the utility to optimally place base stations and test the coverage areas.
`• Set Internet connection settings—including providing Network Address Translation (NAT) and
`Dynamic Host Control Protocol (DHCP) functionality.
`• Configure a base station with wireless MAC address control.
`• Configure port mapping.
`• Save settings so they can be easily uploaded to other AirPort Base Stations.
`• Upload the base station binary.
`• Enable encryption.
`
`7
`
`Refer to pages 20, 22, and 23 for other Admin Utility screen shots.
`
`Microsoft Corp. Exhibit 1049
`
`

`

`8
`
`AirPort Features
`
`When setting up and using a wireless network, there are some key factors to consider that are
`different than when solely using a wired network. Those factors and the related AirPort features
`are discussed below.
`
`Performance
`The performance of wireless LANs is comparable to that of wired LANs. The maximum raw
`data rate for an AirPort network is 11 Mbps (actual data rates will vary). The bandwidth is shared
`among the users on each network in a manner similar to putting multiple computers on an
`Ethernet hub. The factors that affect network performance include the protocols used, the
`number of users on the network, the Internet connection speed, and the distance between
`each computer and the base station.
`
`AirPort, and wireless 802.11 networks in general, use the Carrier Sense, Multiple Access with
`Collision Avoidance (CSMA/CA) protocol scheme. CSMA/CA was designed and optimized for
`wireless LANs. In contrast, Ethernet networks use the Carrier Sense, Multiple Access with
`Collision Detection (CSMA/CD) protocol scheme.
`
`Capacity
`The recommended capacity for each base station is approximately 10 simultaneous users for
`the best Internet experience. That said, there is actually no hard limit to the number of users
`who can access the Internet through a single base station. Users share the bandwidth so the
`connection speed is divided among all users on the network. The maximum number of users
`depends on the connection to the Internet (dial up; Ethernet; or DSL modem), the type of
`applications being used, and whether the base station is acting as a bridge or has Internet con-
`nection sharing turned on. In general, casual Internet browsing requires much
`less bandwidth than activities such as continuous large file transfers or streaming QuickTime
`video. System administrators should understand the usage models of their clients and design
`their wireless networks taking those factors into consideration, just as they would with a
`wired network.
`
`Range
`AirPort offers a typical range of approximately 150 feet indoors in any direction from the base
`station. Because AirPort uses radio frequency signals, the range is affected by the location of the
`base station, the type and placement of the antennas, and the construction and contents of the
`building. The range may be substantially greater than the 150-foot radius from the base station
`in an open-air environment such as a campus quadrangle. Range depends on the strength of
`the signal and the amount of interference or noise on the signal.
`
`Microsoft Corp. Exhibit 1049
`
`

`

`9
`
`AirPort
`AirPort Features
`
`AirPort-enabled computers have antennas built into the enclosures. There are actually two
`antennas in every new Macintosh computer (iMac, iBook, Power Mac G4, and PowerBook) for
`diversity reception. The receiver compares the signals coming from each antenna and chooses
`the best one. This design results in better range and performance.
`
`Security
`AirPort offers encryption and password protection capabilities to deliver a level of security simi-
`lar to that offered by traditional wired networks. To protect the communications on wireless
`networks, AirPort supports Wired Equivalent Privacy (WEP) and other security options.
`
`• WEP is part of the IEEE 802.11 specification and uses both passwords and RC4 encryption. With
`WEP turned off, the wireless network is accessible to anyone within its range. With WEP turned
`on, AirPort uses 40-bit encryption during transmissions to “scramble” data for security. Users
`trying to join an AirPort network are prompted to enter the password for that network (which
`was set up by the network administrator). With AirPort, the passwords are easier to remember
`because they can be real words or phrases. These words or phrases are translated through an
`algorithm to a key that is recognized by the base station.
`• Even greater security can be obtained by using a 128-bit browser on secure websites or
`Mac OS 9 secure sockets on TCP/IP. Entities such as banks or brokerage houses may require
`128-bit browsers to access confidential account information online. With 128-bit browsers, the
`radio link is protected with a baseline 40-bit encryption, and the data is further encrypted
`between the browser and web server at the 128-bit level.
`• An additional form of security can be employed by restricting network access through authoriz-
`ing specific MAC addresses. The MAC address of authorized computers is loaded into the base
`station and only those computers can log on.
`• Some networks may require even greater security. In that case, a network security expert
`should be consulted.
`
`For more information on WEP, refer to the Interoperability section on page 11.
`
`Roaming
`The AirPort Base Station supports two types of roaming: passive and active.
`
`With passive roaming, the user must choose the desired network manually when moving from
`one base station to another. Passive roaming allows for more administrative control in areas
`with densely populated wireless networks by assigning different base stations and thus different
`networks to specific users. It helps ensure that a single base station is not overloaded by too
`many users and helps distribute the wireless load. In this case, each base station is assigned
`a specific network name and if desired, a network password. Users connect to their network
`by selecting the appropriate network name from the list of networks via the Control Strip and
`if needed, entering the correct password.
`
`If a user wants to connect to a base station that is on a different IP subnet from the last one
`the computer was connected to, the TCP/IP settings must be manually changed to reflect the
`new network name and values provided by the network administrator. If the IP address was
`assigned via DHCP, the computer will automatically get a new address, notify all TCP/IP-based
`applications (for example, Internet Explorer, Timbuktu, Eudora, Outlook Express), and change
`all the network settings.
`
`Microsoft Corp. Exhibit 1049
`
`

`

`AirPort
`AirPort Features
`
`10
`
`With active roaming, base stations communicate with each other to allow a client to automati-
`cally transfer from one base station to another without intervention by the user. The connec-
`tion may be momentarily interrupted while the client associates with the new base station.
`
`Active roaming requires all of the base stations to have the same network name and password
`and to be on the same subnet. Users see only one network name and password when they log
`on to the network. A subnet is a portion of a network that shares a common TCP/IP address
`component. The IP devices on the subnet have addresses with the same prefixes but unique
`suffixes for each device.
`
`Active roaming may be beneficial for large networks with wireless users spread out over a
`large geographic area, where a single base station may not be overloaded with too much
`data traffic.
`
`IEEE 802.11, the wireless standard
`The Institute of Electrical and Electronics Engineers (IEEE) is the regulatory group that defines
`standards that allow different companies to build interoperable products. The IEEE 802.11
`worldwide standard sets the interoperability rules for wireless LAN products. Similarly, the
`IEEE 802.3 standard defines interoperability for Ethernet products. More information about
`IEEE can be found at www.ieee.org. More information about 802.11 can be found at
`www.standards.ieee.org.
`
`The 802.11 standard specifies a choice of three types of physical layer RF transmission
`methods: DSSS, Frequency Hopping Spread Spectrum (FHSS), and Diffuse Infrared (IR).
`
`AirPort is compliant with the IEEE 802.11 DSSS specification. DSSS was selected by Apple
`because of its ability to achieve Ethernet speeds wirelessly. And DSSS standards support
`higher data rates than FHSS.
`
`Interoperability occurs within each of the three physical layer categories, but not between
`them. Therefore, DSSS products work with each other, but DSSS and FHSS products do not
`because they use different modulation methods.
`
`Most wireless LANs use spread spectrum radio transmission techniques. Spread spectrum tech-
`nology is designed to be more resistant to noise, interference, and unauthorized detection by
`using the radio-frequency transmitter to spread a narrowband signal over a wideband spectrum.
`DSSS and FHSS products vary in method, range, capacity, performance, noise, and cost.
`
`DSSS systems broaden the signaling band by artificially increasing the modulation rate using a
`spreading code. To detect the communication, an unauthorized person must know the chip-
`ping (spreading) code, the specific portion of the frequency band being used, and the scram-
`bling pattern. For DSSS, the 802.11 standard supports data rates of 1, 2, 5.5, and 11 Mbps.
`
`FHSS changes frequency in a pattern known to both the transmitter and receiver, which
`produces short, choppy bursts of data at rapidly changing frequencies. For FHSS, only 1-
`and 2-Mbps data rates are supported through the 802.11 standard.
`
`Microsoft Corp. Exhibit 1049
`
`

`

`11
`
`AirPort
`AirPort Features
`
`Infrared technology is not often used for wireless LANs because light waves, unlike radio waves,
`cannot pass through solid objects. This limits the range and flexibility of the IR network.
`
`Interoperability
`AirPort complies with the IEEE 802.11 DSSS industry standard. Therefore, AirPort is interopera-
`ble with many third-party 802.11-compliant products running at 1, 2, 5.5, or 11 Mbps. This
`interoperability allows some third-party base stations or other computers with wireless cards
`to be used in an AirPort network.
`
`Some third-party vendors of 802.11 products have not yet implemented WEP. Apple is working
`closely with WECA, the Wireless Ethernet Compatibility Alliance, to ensure that the AirPort
`implementation of WEP continues to meet the 802.11 standard. For more information about
`WECA, visit www.wirelessethernet.org.
`
`The AirPort modem-based Internet connection supports standard PPP protocols. AirPort does
`not support Internet access through providers that use nonstandard protocols, such as those
`in America Online software.
`
`Closed networks
`A “closed network” is a feature provided by some third-party wireless base stations. This feature
`allows a network name to be invisible from some wireless networks. Apple’s AirPort technology
`allows authorized users to log on to a closed network but does not currently allow administra-
`tors to create a closed network with an AirPort Base Station.
`
`In order to access a closed network, the user selects the “closed networks” option in the AirPort
`application and chooses “Other” from the Choose Network feature. The user must correctly
`type in a network name and password to log on to the closed network.
`
`Microsoft Corp. Exhibit 1049
`
`

`

`12
`
`Using AirPort Networks
`
`Supplemental to the AirPort manual, the information in this section will help users understand
`basic AirPort networking activities.
`
`Two types of connections
`The most robust type of AirPort connection is created through a fixed network using a base
`station to provide Internet access and manage the connectivity between the computers on the
`wireless network. The client computer can select the desired network from the various wireless
`networks within range.
`
`A temporary wireless connection can be set up directly between two or more AirPort-enabled
`computers so that users can share files, use collaborative software, or play multiplayer games.
`This type of connection is similar to what users would see if they connected computers
`together using an Ethernet hub but did not connect the hub to a larger network. To initiate
`a computer-to-computer AirPort connection, open the control panel and choose “Computer
`to Computer” from the pop-up menu.
`
`Creating an AirPort network
`The simplest way to set up an AirPort network is as follows:
`
`Step 1. Set up the computer to access the Internet (via modem or Ethernet) and test the
`connection.
`
`Step 2. Install an AirPort Card in a new iBook, iMac, PowerBook, or Power Mac G4 computer.
`(Note: Third-party 802.11-compatible wireless networking PC Cards are available for Macintosh
`PowerBook computers that are not AirPort ready.)
`
`Step 3. Plug an AirPort Base Station into a telephone line, modem, or Ethernet and a power
`source. If connecting to a DSL modem, or just Ethernet, simply plug the cable for that connec-
`tion into the RJ-45 port on the base station.
`
`Step 4. Step through the AirPort Setup Assistant to configure the base station for Internet
`access.
`
`Congratulations, you’ve just created an AirPort network.
`
`Microsoft Corp. Exhibit 1049
`
`

`

`13
`
`AirPort
`Using AirPort Networks
`
`Accessing the Internet
`AirPort technology works similar to the way a cordless telephone works. The handset of the
`cordless phone makes a wireless connection to the base, which is physically connected to the
`telephone line. In an AirPort network, the computers have wireless connections to the base
`station and the base station has a physical connection to the Internet.
`
`An AirPort Base Station can provide wireless Internet access to AirPort-enabled computers in
`several ways:
`
`• Connecting a telephone line or DSL modem to the base station.
`The modem connects the base station to your ISP.
`• Connecting the base station to an existing Ethernet network that already has Internet access.
`
`In either case, the base station receives web pages and email via its Internet connection, and
`then sends them to AirPort-enabled computers using the wireless network. For Internet access,
`users need a network connection and an account with their corporation, their institution, or an
`Internet service provider.
`
`The AirPort modem-based Internet connection uses standard PPP protocols. AirPort does not
`support Internet access through providers that use nonstandard protocols, such as those in
`America Online software.
`
`Optimizing a network
`Because the AirPort network is wireless, it is optimized differently than is a wired network. Key
`factors in setting up and optimizing the wireless network include placement of base stations
`away from interference, ensuring that users have coverage where they need it, and correctly
`assigning channels to the base stations to maximize throughput.
`
`When designing for the optimal placement of base stations, careful signal strength measure-
`ments should be taken in all three dimensions, because AirPort radio signals propagate ver-
`tically between floors as well as horizontally between rooms. To improve signal strength, users
`can move closer to the base station or place the base station higher toward the ceiling to
`lessen obstructions. To reduce noise, minimize the presence of items that may interfere with
`the signal, such as microwave ovens that operate in the same frequency band as AirPort. The
`AirPort signal is absorbed by “soft” materials such as wood, plaster, and glass, and reflected by
`“hard” materials such as concrete and metal. Reflected signals create more noise, which reduces
`the signal quality, while absorbed signals weaken the signal strength.
`
`With a multiple-base-station wireless LAN, it’s important to plan the layout and placement of
`the base stations to ensure adequate coverage and minimize obstructions. Signal strength mea-
`surements should be performed onsite by adjusting the location of either the base station or
`the client computers while testing the connection. The AirPort Admin Utility provides a time-
`based graph for walk-around measurements to determine coverage in a geographic area.
`
`Microsoft Corp. Exhibit 1049
`
`

`

`AirPort
`Using AirPort Networks
`
`14
`
`If two or more AirPort Base Stations will be used within about 150 feet of each other, the multi-
`ple base stations may cause interference on each other’s networks. To remedy this, each base
`station should use a different channel number with a channel separation of five channels. The
`nonoverlapping channels for 11-Mbps wireless networks in the United States are 1, 6, and 11
`(FCC) and in Europe are 1, 7, and 13 (ETSI).
`
`For example, suppose that three AirPort Base Stations are to be used in adjacent rooms in the
`United States. With 11 channels available, here is how the base stations should be configured:
`
`Base station name
`#1
`#2
`#3
`
`Channel
`1
`6
`11
`
`Wireless network name
`Wireless Net #1
`Wireless Net #2
`Wireless Net #3
`
`With this configuration, all of the base stations can be used in the same area without interfering
`with each other because they are operating on separate frequencies. This configuration would
`give the users in that area about 33 Mbps of raw wireless bandwidth.
`
`The same channel can be used by multiple base stations as long as their coverage areas don’t
`overlap. If two base stations that are using the same channel are too close to each other, their
`coverage areas will overlap and they will receive each other’s signal. This will lower the through-
`put of both base stations because only one base station can be operating at a time on the same
`frequency in the same coverage area.
`
`Adding older computers
`An original iMac or Power Macintosh G3 can easily be added to the wireless network by using
`a third-party Ethernet-to-wireless bridge or a crossover Ethernet cable with the base station.
`Although similar to a standard Ethernet cable, the crossover cable has four wires that are
`swapped receiver to transmitter and vice versa so that the computers can exchange data
`without needing a hub.
`
`Microsoft Corp. Exhibit 1049
`
`

`

`AirPort
`Using AirPort Networks
`
`If more than one older computer (including PCs) is in the AirPort network, an Ethernet hub
`is needed. Plug each computer into the hub and plug the hub into the AirPort Base Station.
`
`Manually turning off AirPort communications
`AirPort can be deactivated in situations where radio communications are prohibited, such as in
`an airplane. To turn off AirPort, click the AirPort portion of the Control Strip and choose “Turn
`AirPort Off ” from the menu or use the AirPort application.
`
`15
`
`Using the base station dial-up modem
`When a computer on a wireless network opens an application that requires a connection to
`the Internet, that action automatically activates the AirPort Base Station to begin the connection
`process to your ISP. For example, if a user types a URL into the web browser, the base station
`realizes it needs to make an Internet connection and dials the modem. Alternatively, the AirPort
`application has a Connect button to instruct the modem to dial the user’s ISP. This can be used
`if the connection regularly takes a while to establish itself and the user wants to ensure that he
`or she is connected. The base station does not have an internal speaker, so users do not hear
`the modem dial the same way that they may hear the internal modems on their computers.
`The modem status information located in the AirPort application can be used to provide infor-
`mation about the connection.
`
`As a default, the modem in the AirPort Base Station automatically disconnects from the Internet
`after 10 minutes of inactivity. This initial setting is obtained from the time-out value in the
`Remote Access control panel. Once the base station is programmed, the AirPort Admin Utility
`can be used to adjust the amount of time that the base station waits before disconnecting.
`If you want to hang up the modem in the base station immediately, you can use the AirPort
`application to do so.
`
`Base stations that are connected through the Ethernet port on the base station maintain
`Internet connectivity.
`
`Microsoft Corp. Exhibit 1049
`
`

`

`16
`
`AirPort Networking Examples
`
`The following examples are provided to give network administrators ideas as to how they
`might set up their own networks. Since there are many possible ways of setting up wireless
`networks, all combinations can’t be listed here.
`
`Creating a mobile network
`With AirPort, communication and collaboration among faculty and students on group projects
`or class assignments is now possible without being close to a network connection. Today, many
`schools have computer labs. During a given period, a class of students goes to the computer
`lab to work on projects or do research on the Internet. With AirPort, a mobile computer lab
`can go to the students instead. Let’s take a look at setting up a typical mobile lab.
`
`First, the network administrator sets up the base station using the admin utility. A base station
`name (for example, Base Station #1) and password is assigned primarily for use by the admin-
`istrator. A network name (for example, Mobile Lab Network #1), and password are also
`assigned. The network name and password are what the students use when they log on to
`the network.
`
`In this example, the administrator programs a fixed IP address for the base station. Because the
`school network is all part of the same subnet, the IP address is valid in every classroom. We’ll be
`using the school DHCP server for assigning IP addresses to the mobile lab’s iBook computers
`and hence won’t need the built-in NAT and DHCP functionality of the base station. The base
`station is set up as a wireless bridge by turning Internet connection sharing off using the
`AirPort Admin Utility.
`
`With the administrator’s setup complete, whenever the cart is rolled into a classroom, the base
`station is ready to be plugged into the wall with no additional work required by the teacher.
`
`Using the AirPort Setup Assistant, the iBook computers with AirPort Cards installed can be pre-
`configured. The assistant sets the AppleTalk and TCP/IP control panels to “AirPort,” which allows
`the TCP/IP settings to be assigned automatically from the DHCP server. The network settings
`can also be selected manually.
`
`With the classroom setup complete, the mobile lab can easily be put into use in just a few min-
`utes. When the cart arrives, the base station should be plugged into the existing Ethernet jack
`and AC power source for access to the school’s Ethernet backbone. At the same time, the
`iBook computers can be distributed to the students and started up. When the computers are
`started up, the AirPort software detects the base station in the classroom. Using the Control
`
`Microsoft Corp. Exhibit 1049
`
`

`

`17
`
`AirPort
`AirPort Networking Examples
`
`Strip, students log on to the base station by selecting “Mobile Lab Network #1” from the pull-
`down menu and enter the password if needed. The computers are now ready to research online
`or access the internal school resources on the intranet!
`
`Adjacent AirPort networks
`Many schools are interested in installing a fixed AirPort network to take maximum advantage of
`the benefits of wireless communications. In this example, there are three adjacent classrooms
`with overlapping coverage because the three base stations are within 150 feet of each other. This
`wireless network will be dense, so the priority will be to minimize the amount of interference.
`
`Because there are only three distinct 11-Mbps channels available to share between three base
`stations with overlapping range, careful network planning is essential. The base stations should
`be mounted high on the wall and at least 6 feet apart to minimize interference. To maximize
`throughput, each base station should be plugged into a separate Ethernet jack that runs to a
`10BASE-T switch. Assigning multiple base stations to the same channel is not recommended
`because only one base station transmits data at a time on the same frequency in an overlapping
`coverage area. In this case, we try to minimize the amount of interference by assigning different
`channels in each of the three rooms and by assigning unique passwords for each base station to
`balance the load of each base station.
`
`The base stations are configured using the AirPort Admin Utility. In this case, all of the network
`settings for the computers are manually entered because