I.S. Ch 7 Networks: Mobile Business
Ethernet is the most common connection type for wired networking and is available in speeds from 10 mbps all the way up to 10,000 Mbps (10 Gbit)
The most common wire used for Ethernet networking is Cat5 (Category 5) and the connectors used are RJ45, slightly larger than the RJ11 connectors used by phones, but the same shape.
Streaming is a method of sending audio and video files over the Internet in such a way that the user can view the file while it is being transferred.
The most obvious advantage is speed, a direct benefit for mobile and wireless devices since they are still not as fast as their wired counterparts. 31
Transmission control protocol/Internet protocol (TCP/IP), which provides the technical foundation for the public Internet as well as for large numbers of private networks
One of the primary reasons for developing TCP/IP was to allow diverse or differing networks to connect and communicate with each other, essentially allowing LANs, WANs, and MANs to grow with each new connection.
cable modem (or broadband modem) is a type of digital modem used with high-speed cable Internet service. Cable modems connect a home computer (or network of home computers) to residential cable TV service, while DSL modems connect to residential public telephone service.
broadband or high-speed Internet service has an average transfer rate 10 times faster than conventional dial-up service.
Although the advantages of using wireless networks are significant, added challenges exist such as protecting against theft, protecting wireless connections, preventing viruses on mobile devices, and addressing privacy concerns with RFID and LBS (
figure 7.23 281
TCP (the TCP part of TCP/IP) verifies the correct delivery of data because data can become corrupt when traveling over a network. TCP ensures the size of the data packet is the same throughout its transmission and can even retransmit data until delivered correctly
y. IP (the IP part of TCP/IP) verifies the data are sent to the correct IP address, numbers represented by four strings of numbers ranging from 0 to 255 separated by periods. For example, the IP address of www.apple.com is 97.17.237.15.
smartphones that offer more advanced computing ability and connectivity than basic cell phones.
3G, services that bring wireless broadband to mobile phones.
The Internet is a hierarchical structure linking different levels of service providers, whose millions of devices, LANs, WANs, and MANs supply all the interconnections
. At the top of the hierarchy are national service providers (NSPs)
Spatial data (geospatial data or geographic information) identifies the geographic location of features and boundaries on Earth, such as natural or constructed features, oceans, and more. Spatial data can be mapped and is stored as coordinates and topology.
A GIS accesses, manipulates, and analyzes spatial data.
wireless WAN (WWAN) is a wide area network that uses radio signals to transmit and receive data. WWAN technologies can be divided into two categories: cellular communication systems and satellite communication systems.
A cell phone is a device for voice and data, communicating wirelessly through a collection of stationary ground-based sites called base stations, each of which is linked to its nearest neighbor stations. Base station coverage areas are about 10 square miles and are called cells,
The other wireless WAN technology is a satellite communication system.
A satellite is a space station that orbits the Earth receiving and transmitting signals from Earth-based stations over a wide area
If there is one flaw in TCP/IP, it is the complexity of IP addresses. This is why we use a domain name system (DNS) to convert IP addresses into domains or identifying labels that use a variety of recognizable naming conventions.
A single computer can also have several host names—for instance, if a company is hosting several websites on a single server, much as an ISP works with hosting. Domain names are essentially rented, with renewable rights, from a domain name registrar, such as godaddy.com . Some registrars only register domain names, while others provide hosting services for a fee. ICANN (Internet Corporation for Assigning Names and Numbers) is a nonprofit governance and standards organization that certifies all domain name registrars throughout the world. With the certification, each registrar is authorized to register domain names, such as .com , .edu , or .org .
An intranet is a restricted network that relies on Internet technologies to provide an Internet-like environment within the company for information sharing, communications, collaboration, web publishing, and the support of business processes, as suggested in Figure 7.11 . This network is protected by security measures such as passwords, encryption, and firewalls, and thus only authorized users can access it. Intranets provide a central location for all kinds of company-related information such as benefits, schedules, strategic directions, and employee directories. 17
An extranet is an extension of an intranet that is available only to authorized outsiders, such as customers, partners, and suppliers. Having a common area where these parties can share information with employees about, for instance, order and invoice processing can be a major competitive advantage in product development, cost control, marketing, distribution, and supplier relations. Companies can establish direct private network links among themselves or create private, secure Internet access, in effect a "private tunnel" within the Internet, called a virtual private network (VPN). Figure 7.12 illustrates using a VPN to connect to a corporate server.
global positioning system (GPS) is a satellite-based navigation system providing extremely accurate position, time, and speed information. The U.S. Department of Defense developed the technology in the early 1970s and later made it available to the public. GPS uses 24 global satellites that orbit Earth, sending signals to a receiver that can communicate with three or four satellites at a time. A GPS receiver can be a separate unit connected to a mobile device using cable or wireless technology such as Bluetooth, or it can be included in devices such as mobile phones or vehicle navigation systems.
Automatic vehicle location (AVL) uses GPS tracking to track vehicles. AVL systems use a GPS receiver in the vehicle that links to a control center. Garmin is one of the more popular manufacturers of GPS tracking systems, offering vehicle tracking, phone and laptop integration, and hiker navigation for water and air. The satellites broadcast signals constantly, while the receiver measures the time it takes for the signals to reach it. This measurement, which uses the speed of the signal to determine the distance, is taken from three distinct satellites to provide precise location information. The time measurements depend on high-powered clocks on each satellite and must be precise, because an error of one-thousandth of a second can result in a location variation of more than 200 miles. GPS can produce very accurate results, typically within 5 to 50 feet of the actual location (military versions have higher accuracy) . GPS also provides latitude, longitude, and elevation information. 35
A bit (short for binary digit) is the smallest element of data and has a value of either 0 or 1.
Bandwidth is measured in terms of bit rate (or data rate ),
RFID accelerometer is a device that measures the acceleration (the rate of change of velocity) of an item and is used to track truck speeds or taxi cab speeds.
Chipless RFID tags use plastic or conductive polymers instead of silicon-based microchips, allowing them to be washed or exposed to water without damaging the chip. Examples of the innovative uses of RFID include: ■ RFID chips injected under the skin of animals using a syringe can help ranchers meet regulations, track wild animals for ecological studies, and return lost pets to their owners. ■ Retail stores use RFID to track and monitor inventory. Hospitals and pharmaceutical companies meet government regulations and standards with RFID. Even local libraries are using RFID to control theft and speed up the checkout process. ■ Car manufacturers install RFID antitheft systems. Toll roads use RFID to collect payments from passing cars. ■ Hospitals track patients', doctors', and nurses' locations to facilitate emergency situations and ensure safety. RFID also tracks equipment location to ensure quick response times during an emergency. ■ American Express and MasterCard use RFID for automatic payments. ■ Walmart and other large retailers use RFID to maintain inventory, stop shoplifting, and speed customer checkout processes.
A protocol is a standard that specifies the format of data as well as the rules to be followed during transmission.
Computers using the same protocol can communicate easily, providing accessibility, scalability, and connectability between networks
The devices used for satellite communication range from handheld units to mobile base stations to fixed satellite dish receivers. The peak data transmission speeds range from 2.4 Kbps to 2 Mbps. For the everyday mobile professional, satellite communication may not provide a compelling benefit, but for people requiring voice and data access from remote locations or guaranteed coverage in nonremote locations, satellite technology is a viable solution.
Conventional communication satellites move in stationary orbits approximately 22,000 miles above Earth. A newer satellite medium, the low-orbit satellite, travels much closer to Earth and is able to pick up signals from weak transmitters. Low-orbit satellites also consume less power and cost less to launch than conventional satellites. With satellite networks, businesspeople almost anywhere in the world have access to full communication capabilities, including voice, videoconferencing, and Internet access. Figure 7.19 briefly illustrates the satellite communication system.
Thus, a customer's telephone provider is also its ISP, and the telephone line carries both data and telephone signals using a DSL modem. DSL Internet services are used primarily in homes and small businesses.
DSL has two major advantages over dial-up. First, it can transmit and receive data much faster—in the 1 to 2 Mbps range for downloading and 128 Kbps to 1 Mbps for uploading. (Most high-speed connections are designed to download faster than they upload, because most users download more—including viewing web pages—than they upload.) The second major advantage is that because they have an "always on" connection to their ISP, users can simultaneously talk on the phone and access the Internet. DSL's disadvantages are that it works over a limited physical distance and remains unavailable in many areas where the local telephone infrastructure does not support DSL technology. 5
Provides Mobile Business Opportunities Unlike ebusiness, which normally requires desktop or laptop computers to connect to the Internet, mbusiness offers the advantages of making a purchase via the Internet an anywhere, anytime experience. It provides consumers with the ability to obtain information and order goods and services quickly and easily using a mobile device. The growing popularity of iPhones along with iPhone apps have helped fuel the growth of mbusiness. A few mbusiness offerings include:
Digital purchases. The most suitable purchase for a mobile user is for products that can be downloaded and used immediately such as music and (electronic) books. ■ Location-based services. The ability for merchants to capture and react to a user's current location and requirements can be a powerful tool for selling products and services. ■ Mobile banking and payments. Using a mobile device can provide access to personal bank accounts to view account history and execute transactions. In addition, a mobile device can be used for making payments, essentially acting as digital cash. For example, someone can order and pay for a Starbucks latte using a mobile device and app. ■ Mobile shopping. Most forms of shopping may be impractical using mobile devices; however, some forms of purchases lend themselves to mbusiness. For example, having the ability to purchase movie tickets for a show playing the same evening can be quite valuable. Mobile devices can also be used for comparison shopping. Before making a purchase, a shopper in a retail store may want to first see what the current price of a product is from another vendor to ensure he is getting a good price. 39
LBS can track and monitor objects much like RFID. Tracking vulnerable individuals and company assets is beneficial. But the dark side of LBS risks the invasion of privacy and security caused by indiscreet location tracking. For example, if a company is using LBS to know where each employee is on duty, it must not observe their positions when they are off duty. Advertising at random to users in a specific area may violate privacy if mobile users in the area do not want to receive these advertisements. Criminals might also take advantage of illegal location tracking. And because LBS are based on message exchange in a wireless network, there are always security risks because location information could be stolen, lost, or modified. Security mechanisms must eliminate or minimize the potential for attacks against LBS entities and reduce exposure of the user's identity and location. One way to solve the location privacy problem is to provide strong privacy practices that counterbalance the invisible nature of location collection in the wireless world. LBS policies should specify that:
Direct marketing purposes are permitted only with the business or service a user has a contract with. ■ Electronic messages cannot hide the identity of the sender. Solicitation is allowed only if the user has given prior consent. ■ The location service must tell the user about the type, duration, and purpose of the data they are collecting. ■ The user must be given the opportunity to reject any direct marketing opportunities.
Latitude represents a north/south measurement of position. Longitude represents an east/west measurement of position. Geocache is a GPS technology adventure game that posts the longitude and latitude location for an item on the Internet for users to find. GPS users find the geocache and typically sign a guest book or take an item and leave an item for the next adventure players to find. Caches are often placed in locations that are interesting or challenging for people to discover. A geocoin, a round coin-sized object, is uniquely numbered and hidden in geocache. Geocoins can also be shaped to match a theme such as the state of Colorado or a birthday party hat. Geocoins are often decorative or commemorative, making them collectible and highly valuable for technology adventures.
Estimated time of arrival (ETA) is the time of day of an expected arrival at a certain destination and is typically used for navigation applications. Estimated time enroute (ETE) is the time remaining before reaching a destination using the present speed and is typically used for navigation applications
A connection with a traditional telephone line and a modem, which most residential users had in the 1990s, is called dial-up access
First, it is slow, providing a maximum rate of 56 Kbps. (At 56 Kbps, it takes eight minutes to download a three-minute song and more than a day to download a two-hour movie.) Second, dial-up modem access ties up the telephone line so the user cannot receive and make phone calls while online. The good news is this is not as big an issue as it once was as many people have cell phones and no longer require using the telephone line for making phone calls. 4
Another level down is an Internet service provider (ISP), which specializes in providing management, support, and maintenance to a network
ISPs vary services provided and available bandwidth rates. ISPs link to RSPs and, if they are geographically close, to other ISPs. Some also connect directly to NSPs, thereby sidestepping the hierarchy.
An exciting and new convergence is occurring in the area of television with Internet Protocol TV (IPTV)
Internet Protocol TV (IPTV), which distributes digital video content using IP across the Internet and private IP networks. A few IPTV features include: ■ Support of multiple devices: PCs and televisions can access IPTV services. ■ Interactivity with users: Interactive applications and programs are supported by IPTV's two-way communication path. ■ Low bandwidth: IPTV conserves bandwidth because the provider sends only a single channel. ■ Personalization: Users can choose not only what they want to watch, but also when they want to watch it. 15
GPS and GIS both utilize location-based services (LBS), applications that use location information to provide a service
LBS is designed to give mobile users instant access to personalized local content and range from 911 applications to buddy finders ("Let me know when my friend is within 1,000 feet") to games (treasure hunts) to locationbased advertising ("Visit the Starbucks on the corner and get $1.00 off a latte"). Many LBS applications complement GPS and GIS, such as: ■ Emergency services ■ Field service management ■ Find-it services ■ Mapping ■ Navigation ■ Tracking assets ■ Traffic information ■ Vehicle location ■ Weather information ■ Wireless advertising 37
national service providers (NSPs), private companies that own and maintain the worldwide backbone that supports the Internet.
Network access points (NAPs) are traffic exchange points in the routing hierarchy of the Internet that connects NSPs. They typically have regional or national coverage and connect to only a few NSPs. Thus, to reach a large portion of the global Internet, a NAP needs to route traffic through one of the NSPs to which it is connected.
SECURITY
Networks are a tempting target for mischief and fraud. A company first has to ensure proper identification of users and authorization of network access. Outside suppliers might be allowed to access production plans via the company's extranet, for example, but they must not be able to see other information such as financial records. The company should also preserve the integrity of its data; only qualified users should be allowed to change and update data, and only well-specified data. Security problems intensify on the Internet where companies need to guard against fraud, invalid purchases, and misappropriation of credit card information.
personal area network (PAN) provides communication for devices owned by a single user that work over a short distance.
PANs are used to transfer files, including email, calendar appointments, digital photos, and music. A PAN can provide communication between a wireless headset and a cell phone or between a computer and a wireless mouse or keyboard. Personal area networks generally cover a range of less than 10 meters (about 30 feet). Bluetooth is a wireless PAN technology that transmits signals over short distances among cell phones, computers, and other devices. Bluetooth operates at speeds up to 1 Mbps within a range of 33 feet or less. Devices that are Bluetooth-enabled communicate directly with each other in pairs, like a handshake. Up to eight can be paired simultaneously. And Bluetooth is not just for technology devices. An array of Bluetooth-equipped appliances, such as a television set, a stove, and a thermostat, can be controlled from a cell phone—all from a remote location.
Enhancing mobility is one of the greatest advantages provided by wireless networks
PG 278 FIG 7.22
Sharing physical resources also supports a sustainable MIS infrastructure, allowing companies to be agile, efficient, and responsible at the same time. . Cloud computing (see Chapter 5) and virtualization consolidate information as well as systems that enhance the use of shared resources. By using shared resources, cloud computing and virtualization allow for collective computing power, storage, and software, in an on-demand basis.
Perhaps even more important than sharing physical resources is sharing data. Most companies, regardless of size, depend not just on their customer records, inventories, accounts receivable, financial statements, and tax information, but also on their ability to share these, especially with operations in remote locations. Networking with a LAN, WAN, or MAN allows employees to share data quickly and easily and to use applications such as databases and collaboration tools that rely on sharing. By sharing data, networks have made business processes more efficient. F
wide area network (WAN) spans a large geographic area such as a state, province, or country.
Perhaps the best example is the Internet. WANs are essential for carrying out the day-to-day activities of many companies and government organizations, allowing them to transmit and receive information among their employees, customers, suppliers, business partners, and other organizations across cities, regions, and countries and around the world
Protecting Against Theft Any mobile device is vulnerable to loss no matter how big or small it is. The company may face significant exposure from stolen IDs, passwords, encryption keys, and confidential information if the device falls into the wrong hands, especially if the theft is not discovered or reported immediately and the company does not have time to revoke access.
Power-on passwords—passwords implemented at the hardware level that must be entered before gaining access to the computer—are the first line of defense against unauthorized use. Companies should activate these passwords before giving their workforce the devices. They should also prohibit storing passwords on devices and periodically monitor compliance with the policy. Companies need to consider encrypting and password-protecting data stored on the device, including any flash drives or other mobile storage devices. In addition, some device management tools can send messages to a device to lock it or destroy its contents, which can be an attractive security feature.
RFID reader (RFID interrogator) is a transmitter/receiver that reads the contents of RFID tags in the area. A RFID system is comprised of one or more RFID tags, one or more RFID readers, two or more antennas (one on the tag and one on each reader), RFID application software, and a computer system or server, as Figure 7.21 illustrates. Tags, often smaller than a grain of rice, can be applied to books or clothing items as part of an adhesive bar-code label, or included in items such as ID cards or packing labels
Readers can be stand-alone devices, such as for self-checkout in a grocery store, integrated with a mobile device for portable use, or built in as in printers. The reader sends a wireless request that is received by all tags in the area that have been programmed to listen to wireless signals. Tags receive the signal via their antennas and respond by transmitting their stored data. The tag can hold many types of data, including a product number, installation instructions, and history of activity (such as the date the item was shipped). The reader receives a signal from the tag using its antenna, interprets the information sent, and transfers the data to the associated computer system or server.
One step down in the hierarchy is the regional service provider. Regional service providers (RSPs)
Regional service providers (RSPs) offer Internet service by connecting to NSPs, but they also can connect directly to each other
Passive RFID tags do not have a power source, whereas active RFID tags have their own transmitter and a power source (typically a battery). The power source runs the microchip's circuitry and broadcasts a signal to the reader (similar to the way a cell phone transmits signals to a base station). Passive RFID tags draw power from the RFID reader, which sends out electromagnetic waves that induce a current in the tag's antenna
Semipassive RFID tags use a battery to run the microchip's circuitry, but communicate by drawing power from the RFID reader Asset tracking occurs when a company places active or semi-passive RFID tags on expensive products or assets to gather data on the items' location with little or no manual intervention. Asset tracking allows a company to focus on its supply chain, reduce theft, identify the last known user of assets, and automate maintenance routines. Active and semi-passive tags are useful for tracking highvalue goods that need to be scanned over long ranges, such as railway cars on a track. The cost of active and semi-passive RFID tags is significant; hence, low-cost items typically use passive RFID tags.
Addressing Privacy Concerns with RFID and LBS As technology advances, the potential for privacy infringement does as well. RFID already has the capability to determine the distance of a tag from the reader location. It is not difficult to imagine that retailers could determine the location of individuals within the store and target specific advertisements to them based upon past purchases and shopping and behavior patterns. Many consumers would consider gathering such information intrusive enough, but the possibility that it could be sold to other retailers might lead consumers to refuse to give retailers any information.
Several steps are being taken to address these privacy concerns. For example, one proposal would require all RFID-tagged products to be clearly labeled. This would act as an alert mechanism to which items are being tracked. Another measure being considered is "Kill Codes," which would turn off all RFID tags when someone comes into contact with them. Another measure is "RSA Blocker Tags," which try to address privacy concerns while maintaining the integrity of the product. Only that store's authorized reader can track items with these tags; customers cannot be tracked outside the store in which they made a purchase.
Protecting Wireless Connections Network intrusions can occur if access codes or passwords are stored on a device that is lost or stolen. However, any time a wireless network connects to a wired one, the wireless network can serve as a conduit for a hacker to gain entry into an otherwise secure wired network. This risk is especially high if the wireless network is not sufficiently secured in its own right. Before the emergence of the Internet, hackers generally had to be physically present within the corporate complex to gain access to a wired network. The thousands, if not millions, of access points enabled by the Internet now allow hackers to work from a distance. This threat has spawned a variety of different security techniques from firewalls to VPNs to SSL and HTTPS.
Several techniques can secure wireless networks from unauthorized access whether used separately or in combination. One method is authenticating Wi-Fi access points. Because Wi-Fi communications are broadcast, anyone within listening distance can intercept communications. Every time someone uses an unsecured website via a public Wi-Fi access point, his or her log-on name and password are sent over the open airwaves, with a high risk that someone might "eavesdrop" or capture log-on names, passwords, credit card numbers, and other vital information.
Two ways to use VoIP for telephone calls are through a web interface that allows users to make calls from their computer and through a phone attached to a VoIP adapter that links directly to the Internet through a broadband modem. Figure 7.9 illustrates these two ways along with the use of VoIP-enabled phones, bypassing the need for an adapter. VoIP services include fixed-price unlimited local and long-distance calling plans (at least within the United States and Canada), plus a range of interesting features, such as
The ability to have more than one phone number, including numbers with different area codes. ■ Integrating email and voice mail so users can listen to their voice mail using their computer. ■ The ability to receive personal or business calls via computer, no matter where the user is physically located. 13 The biggest benefit of VoIP is its low cost. Because it relies on the Internet connection, however, service can be affected if the bandwidth is not appropriate or Internet access is not available. Skype is a perfect example of IP applied to telephone use. Unlike typical VoIP systems that use a client and server infrastructure, Skype uses a peer-to-peer network.
Individuals and companies use local ISPs to connect to the Internet, and large companies tend to connect directly using an RSP. Major ISPs in the United States include AOL, AT&T, Comcast, Earthlink, and NetZero.
The backbone shown in Figure 7.3 is greatly simplified, but it illustrates the concept that basic global interconnections are provided by the NSPs, RSPs and ISPs. 3
Network convergence is the efficient coexistence of telephone, video, and data communication within a single network, offering convenience and flexibility not possible with separate infrastructures.
The benefits of network convergence allow for multiple services, multiple devices, but one network, one vendor, and one bill, as suggested by One of the challenges associated with network convergence is using the many different tools efficiently and productively. Knowing which communication channel—PC, text message, videoconference—to use with each business participant can be a challenge
Secure sockets layer (SSL) is a standard security technology for establishing an encrypted link between a web server and a browser, ensuring that all data passed between them remain private. Millions of websites use SSL to protect their online transactions with their customers.
To create an SSL connection, a web server requires an SSL Certificate, an electronic document that confirms the identity of a website or server and verifies that a public key belongs to a trustworthy individual or company. Typically, an SSL Certificate will contain a domain name, the company name and address, and the expiration date of the certificate and other details. Verisign is the leading Internet Certification Authority that issues SSL Certificates. When a browser connects to a secure site, it retrieves the site's SSL Certificate, makes sure it has not expired, and confirms a Certification Authority has issued it. If the certificate fails on any one of these validation measures, the browser will display a warning to the end user that the site is not secure. If a website is using SSL, a lock icon appears in the lower right-hand corner of the user's web browser.
File transfer protocol (FTP) is a simple network protocol that allows the transfer of files between two computers on the Internet.
To transfer files with FTP, the FTP client program initiates a connection to a remote computer running FTP "server" software. After completing the connection the client can choose to send and/or receive files electronically. N
Traceroute is a utility application that monitors the network path of packet data sent to a remote computer.
Traceroute programs send a series of test messages over the network (using the name or IP address) until the last message finally reaches its destination. When finished, traceroute displays the path from the initial computer to the destination computer.
Unified communications (UC) is the integration of communication channels into a single service.
UC integrates communication channels allowing participants to communicate using the method that is most convenient for them. UC merges instant messaging, videoconferencing, email, voice mail, and VoIP. This can decrease the communication costs for a business while enhancing the way individuals communicate and collaborate. One area experiencing huge growth in network convergence is the use of the Internet for voice transmission.
War chalking is the practice of tagging pavement with codes displaying where Wi-Fi access is available. The codes for war chalking tell other users the kind of access available, the speed of the network, and if the network is secured.
War driving is deliberately searching for Wi-Fi signals while driving by in a vehicle. Many individuals who participate in war driving simply map where Wi-Fi networks are available.more malicious intent and use war driving to hack or break into these networks. War driving has been a controversial practice since its inception and has raised the awareness of the importance of wireless network security.
Worldwide Interoperability for Microwave Access (WiMAX), a communications technology aimed at providing high-speed wireless data over metropolitan area networks. In many respects, WiMAX operates like Wi-Fi, only over greater distances and with higher bandwidths. A WiMAX tower serves as an access point and can connect to the Internet or another tower. A single tower can provide up to 3,000 square miles of coverage, so only a few are needed to cover an entire city. WiMAX can support data communications at a rate of 70 Mbps. In New York City, for example, one or two WiMAX access points around the city might meet the heavy demand more cheaply than hundreds of Wi-Fi access points. WiMAX can also cover remote or rural areas where cabling is limited or nonexistent, and where it is too expensive or physically difficult to install wires for the relatively few users. 26
WiMAX can provide both line-of-sight and non-line-of-sight service. A non-line-ofsight service uses a small antenna on a mobile device that connects to a WiMAX tower less than six miles away where transmissions are disrupted by physical obstructions. This form of service is similar to Wi-Fi but has much broader coverage area and higher bandwidths. A line-of-sight option offers a fixed antenna that points at the WiMAX tower from a rooftop or pole. This option is much faster than non-line-of-sight service, and the distance between the WiMAX tower and antenna can be as great as 30 miles. Figure 7.16 illustrates the WiMAX infrastructure. 27 Some cellular companies are evaluating WiMAX as a means of increasing bandwidth for a variety of data-intensive applications such as those used by smartphones. Sprint Nextel and Clearwire are building a nationwide WiMAX network in the United States. WiMAX-capable gaming devices, laptops, cameras, and even cell phones are being manufactured by companies including Intel, Motorola, Nokia, and Samsung. 28
Mobile means the technology can travel with the user, for instance, users can download software, email messages, and web pages onto a laptop or other mobile device for portable reading or reference. Information collected while on the road can be synchronized with a PC or company server
Wireless, on the other hand, refers to any type of operation accomplished without the use of a hard-wired connection. There are many environments in which the network devices are wireless but not mobile, such as wireless home or office networks with stationary PCs and printers. Some forms of mobility do not require a wireless connection; for instance, a worker can use a wired laptop at home, shut down the laptop, drive to work, and attach the laptop to the company's wired network
Broadband over power line (BPL) technology makes possible high-speed Internet access over ordinary residential electrical lines and offers an alternative to DSL or high-speed
cable modems. BPL works by transmitting data over electrical lines using signaling frequencies higher than the electrical (or voice in the case of DSL) signals. BPL allows computer data to be sent back and forth across the network with no disruption to power output in the home. Many homeowners are surprised to learn that their electrical system can serve as a home network running speeds between 1 and 3 Mbps with full Internet access. Unfortunately, limitations such as interference and availability have affected BPL's popularity.
A packet is a single unit of binary data routed through a network
k. Packets directly impact network performance and reliability by subdividing an electronic message into smaller more manageable packets Standard packet formats include a packet header, packet body containing the original message, and packet footer packet header lists the destination (for example, in IP packets the destination is the IP address) along with the length of the message data packet footer represents the end of the packet or transmission end. The packet header and packet footer contain error-checking information to ensure the entire message is sent and received The receiving device reassembles the individual packets into the original by stripping off the headers and footers and then piecing together the packets in the correct sequence