OBJETIVOS ESPECÍFICOS

With the growing use of computers and the popularity of the Internet, it has become viable to deploy LANs in places where we never thought we would need a LAN. Today, LANs are being used in industrial manufacturing, offices, small businesses, and at homes. Wireless networking has taken LAN connectivity a step further. Now, with wireless networking, LANs have become far more flexible than they used to be. Wireless LANs are easier to build than conventional wired LANs and provide mobility to LAN users. Wireless LANs are being used to connect mobile devices, such as personal digital assistants (PDAs) and laptop computers, with stationary computers, such as desktop computers. Wireless networking equipment is also being used to connect separate buildings as well as extending the reach of the Internet and the virtual private networks (VPNs) across several miles in remote areas where wired infrastructure is sparse.

In this chapter we discuss the different aspects of a wireless LAN that directly impact the feasibility for SoHo, enterprise, and WISP deployment scenarios. We talk about the benefits, deployment scenarios, costs associated, deployment issues, bandwidth and network congestion, security, and health concerns of the wireless LANs. If you decide that wireless LANs are not suitable for you, you should look at Chapter 1, "Networking Basics," which describes a basic wired LAN to study whether wired LANs satisfy your needs.

Benefits of Wireless LANs

The primary advantage that wireless LANs have over wired networks is that they do not require wires and can be set up quickly in areas where wiring costs can be prohibitive. The advent of wireless LANs has provided us with a greater level of flexibility on how we configure our computing equipment and environment than the wired LANs. You no longer need separate modems, black−and−white printers, color printers, scanners, CD−ROM readers/writers, and other devices for every computer in your home or office. You also do not need to go through the hassle of keeping multiple copies of files when sharing a document.

When deciding whether a wireless network is right for you, you should first make sure that you do indeed need a LAN. Though LANs provide some very useful services, they incur installation and maintenance costs. To justify your need for a LAN, you should have at least one computer, and one or more of the following should apply to you:

You want to share files across computers.

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You intend to share a printer among computers.

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Only one Internet connection is available, and you want to share it across two or more computers.

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You intend to share a new type of device that connects to a LAN and make its services available to all the computers on the given LAN—for example, a computer controlled telescope.

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You are willing to spend a decent amount of money to build a network.

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Your workstations and other network devices need to be mobile and not tied down to a particular location.

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Physical limitations prohibit running network cables and drops.

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Lease or other restrictions do not allow for installation of a wiring plant.

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You need to deploy networks in open spaces where you expect a lot of foot traffic, and network wires and equipment would cause additional safety issues.

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You temporarily need a LAN, for example, at a research site.

In today's computing environments, devices, data, and resources are often distributed across multiple points on a network and are accessible from any authorized workstation in that network. Wireless LAN takes these capabilities to the next level by adding mobility to the workstations and network devices. Within a wireless LAN, the workstations are not limited to a single position in the building but can be moved around while they continue to function. Powerful portable computers and network devices can be carried around a building or campus while they continue to communicate with mission−critical servers and other computers on the rest of the network, sharing information.

Deployment Scenarios

Wireless LANs can be deployed in many different deployment scenarios. Each deployment scenario has a different set of needs. In this section we restrict our focus to small office home office (SoHo), enterprise, and Wireless Internet Service Providers (WISP) scenarios.

Small Office Home Office (SoHo)

Small office home office (SoHo) deployment generally involves either a home LAN, a LAN at a home−based office, or a LAN at a small business. Wireless LANs are rapidly becoming networks of choice for these uses because of their low cost and lack of wiring needs. Setting up wired LANs requires complex wiring generally running to a central point, which is not only costly but in some cases, such as apartments or older homes, almost impossible.

In SoHo environments, the number of computers in a LAN is typically very small. These LANs normally contain between 2 and 10 computers. They are normally used to share files, printers, and data backup devices. Nowadays it is also very common for SoHo networks to share a single Internet connection. Under most circumstances, these networks do not require high security. The speed requirement is nominal, and the budget is small. Therefore, for the SoHo environment, a suitable LAN would be one that is not too complex, has a reasonable level of security, provides the ability to connect with the Internet, and does not require a major investment.

In a SoHo or a home network there may be several computers, a color printer, a black−and−white laser printer, a scanner, several CD−ROM readers, a CD−ROM writer, and a modem (see Figure 4.1). Using a wireless LAN, these resources can be shared efficiently, and you do not need to purchase and install every device for every computer. You can scan a picture from the scanner connected to the desktop in your child's bedroom to the file server (a computer on the LAN with a high−capacity shared hard disk) in your home office that also has the color printer attached it. Then you go to the family room and use the imaging software on your notebook to edit and enhance the picture while you recline in your favorite chair and watch TV surrounded by your loved ones. After completing your first draft, you print the file on the printer attached to the server in your office and review it. You then email the picture to your partner through the Internet−sharing device and cable modem; you also leave a note for your assistant with the file name. When your assistant comes in the next day, he or she opens the file that you saved on the server from his or her workstation and makes the final changes. Over the weekend your friends come over with their laptops and 802.11b Wi−Fi cards and you play network games over the wireless LAN.

Figure 4.1: A SoHo wireless LAN setup.

Enterprise

Enterprise networks are generally comprised of a larger number of computers, security systems, file−storage and archiving systems, many workstations and laptops, several servers, multiple printers and scanners as well as presentation systems participating in a network. In industrial complexes and manufacturing plants, there may be machinery that needs to communicate with central servers. Enterprise networks are typically divided into several workgroups. The security requirements are very high, the users need to be authenticated, the data and resources have to be protected not only from outsiders but there is also the need to have proper access control for authorized users. The speed and bandwidth requirements are also high, and the network needs to be properly segmented to reduce the network traffic. An enterprise network can also span across multiple floors, multiple buildings, and multiple locations. There may be several Internet and VPN connection lines linking a network with other parts of the enterprise network. There is also the need for covering the complete office area without any dead zones (an area without a network signal) as well as allowing the users to roam freely between floors, in the campus, and across locations. Wireless LANs provide the opportunity for enterprises to provide greater mobility to their computer users as well as to lower costs for connecting work areas across buildings and floors (see Figure 4.2). There is no longer a need to run expensive cabling between floors and buildings. This is even more useful in industrial and warehouse situations, where there is an even greater need for mobility for monitoring and data−gathering devices such as inventory scanners. Automobile rental companies have long used wireless networks to check in and check out cars. In offices, wireless networks open the possibility of configuring more flexible workspaces. Many organizations using the wireless LANs provide roaming offices to their employees. In roaming offices, employees do not have fixed offices but use the available space on a per−need basis. In project−oriented workplaces, knowledge workers may need to work in several workgroups during the course of the same day. Using wireless LANs, these workers can get together and collaborate without losing productivity. Knowledge workers no longer need to be tied to their desks to access the data they need. The participants in the meetings can bring their portable computing devices to the meetings. Wireless networking is also changing the structure of meetings. Participants often "chat" in smaller groups and carry out side "conversations" and exchange information privately using their portable devices connected to the network without disturbing the main meeting. There are now 802.11b−based wireless presentation devices coming on the market that allow corporate users to prepare presentations on their workstations and then deliver them without having to deal with the wires on projectors that are permanently attached to wireless receivers. One can expect these receivers to be integrated in the projectors as time passes. We are all familiar with going into a meeting and then waiting for the presenter to connect their computers to the projectors and fiddle with the projectors until they get started.

Figure 4.2: Enterprise wireless LAN setup.

Wireless Internet Service Providers (WISPs)

Wireless ISPs, or WISPs, are growing very rapidly across the country. Their greatest penetration seems to be in remote or rural areas. As the demand for broadband grows, so grows the gap in availability between urban and remote rural areas. In urban areas, with rapidly declining costs of wireless equipment, opportunities are developing for WISPs to provision buildings without the need for the expensive wiring. There are several WISPs providing services at major hotels, airport terminals, and restaurants. The Wireless ISPs have a higher need for authentication so that only authorized users can access their systems. Generally their security needs are moderate and not as high as enterprise networks.

The Wireless ISPs come in two flavors:

Those providing 802.11b−based services at public access points in the urban areas

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Those providing wireless services to customer premises in remote areas

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Wireless Access in Urban Public Areas

There are several operators offering high−speed Internet connections at public locations such as coffee shops, airports, hotels, and neighborhoods. These organizations are community−based, providing anonymous and free access, as well as commercial companies that provide such service at cost. One such wireless operator is T−Mobile USA, Inc (for more information, go to their Web site at www.t−mobile.com/hotspot), which has access points at over 1,200 locations across the country including almost all Starbucks in Manhattan and the San Francisco Bay area. Let's look at some of the WISPs that are currently providing service in the different parts of the United States.

Commercial Operators

There are many commercial operators providing Internet services at restaurants, hotels, malls, and other such locations where a large number of people are likely to congregate. Most of the

coverage areas. One operator, http://www.hereuare.com/ is starting a program that allows users to roam between different areas and use services available from a variety of providers through their partnership agreements. Currently there are two main commercial operators providing public 802.11b−based high−speed Internet services. Generally their network access points are connected to T1 or DSL connections to the Internet. They typically have several types of access accounts both that have monthly charges as well as pay−as−you−go plans.

T−Mobile USA, Inc. (www.t−mobile.com/hotspot). T−Mobile by far has the largest

network with over 1,200 access points, at the time of this writing, across the country. The service is known as T−Mobile HotSpot Service. T−Mobile HotSpot users need an account to access the T−Mobile HotSpot services, which are available in over 1,200 locations including hotels and airports.

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Wayport Inc. (www.wayport.com). Wayport generally caters to business users. They

manage access points at many airports and more than 420 hotels, including Four Seasons Hotels & Resorts, Wyndham Hotels & Resorts, Sonesta Hotels & Resorts, Radisson Hotels, and Ramada Inns.

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hereUare Communications (www.hereuare.com). According to their Web site, hereUare

Communications claims that "unified Wireless Access technology provides the common glue between the myriad of Service Providers, hardware vendors, and wireless Internet access points."

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802.11 Public Access Wireless LANs

Most public access wireless LANs are generally managed by community−based independent operators that provide Internet access to the public without any charge. Most broadband providers frown upon such services because they see the public access wireless LANs as a dilution of their market in these service areas. Some of the broadband providers actively monitor the bandwidth usages of its users and at times terminate their service. Nevertheless these public access wireless networks are gaining popularity and are cropping up everywhere. The following is a list of some providers and Internet sites that list wireless LANs:

WLANA (www.wlana.org). Lists various equipment vendors, network software providers,

and WISPs.

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WiFinder (www.wifinder.com). WiFinder lets users search for a public wireless access

point anywhere in the United States.

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Wireless Service to Customer Premises

Several ISPs in remote rural areas provide Internet access services via 802.11b to customer premises. These services normally use technologies involving equipment that works in the line of sight. The ISP generally provides a box that can "see" the ISP tower. These boxes communicate with the ISP tower and connect the customer LAN with the Internet through the ISP infrastructure. One such ISP is in Maine. Midcoast Internet Solutions (MIS) started in 1995 in a basement in Owl's Head, Maine. MIS put BreezeNET brand devices on a tower at a high point near Owl's Head, and its new business began. MIS uses a variety of BreezeNET devices:

Client devices called station adapters (SA) that plug into Ethernet LANs, more or less standard access points (AP)

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Wireless bridges (WB), which connect repeater stations with MISs Internet feed

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In a typical end−user installation, MIS brings out a station adapter and an antenna and performs all the wiring necessary to bring an Ethernet connection to the right drop spot. The company sites new locations with either a view to an AP on one of its towers or mountain sites, or by pointing at

businesses that host repeating stations.

Costs Associated with Wireless LANs

The popularity of wireless LANs is making it attractive for hardware vendors to manufacture wireless LAN hardware. This popularity is not only bringing thousands of devices to the market, but it is also bringing the prices down. The cost of ownership of a wireless LAN depends on the deployment scenario, the number of users, and the quality of service desired.

SoHo

SoHo deployments are the simplest. These deployments normally require an AP, and a wireless LAN network interface card (NIC) for each computer or device that connects to the wireless LAN. A wireless LAN that uses 802.11b technology with four computers and an AP with broadband connectivity can be built for under $500. An AP without the broadband connectivity might result in even less cost.

Enterprise

Enterprises are the hardest when estimating costs. Enterprise costs depend on the number of users, area of coverage, and the number of APs that might be needed. When calculating the cost of wireless LANs for enterprises, you should be especially careful about the reliability and security of such networks. The best quality components with the highest level of security available should be used to build such LANs. If roaming is desired (which enables the users to roam within a network of two or more APs), when selecting APs, ensure that the APs you purchase support roaming features. If a wireless LAN is to be supported across buildings, then high−power line−of−sight equipment can be used for interconnecting the LANs in two buildings.

Mixing 802.11a with 802.11b devices might also be a solution when interference is a concern. 802.11a can be used to interconnect LANs or to provide a wireless backbone.

WISPs

Most WISP networks today only support 802.11b devices at the point of service. These locations normally include coffee shops, airports, and shopping malls. The cost to build one such site using 802.11b to support up to 10 users would include an AP, a computer to authenticate the users and ensure proper billing, and a broadband Internet connection. A WISP can bring the Internet connection to the point of service using a wireless solution, or using the local communications provider. So, the major cost when setting up a WISP site is the Internet connection.

Deployment Issues

Deployment issues for wireless LANs include the location of the AP, interference with other wireless devices, and network bandwidth.

AP is placed at an obstructed location, the network may not perform to its best. APs should be placed where they are least obstructed. A good idea is to perform a site survey and find a location that is central and provides the best signal across the property.

Security of the network is also a concern in SoHo environments. Radio frequency penetrates walls, and if someone on the other side of the wall is aware of a wireless LAN operation, they can easily bring their own wireless LAN cards and connect to the same network. It is, therefore, important that wireless LANs are set up for use with authentication and encryption.

Enterprise

Enterprise wireless LANs have to be very carefully segmented, which means that you must install a