Chapter 4: Telecommunications and Networking (Before You Go On)

What are the primary business reasons for using networks?

* Enables Organizations to be more flexible and adaptable to changing business environments. * Enables companies to share hardware, applications,and data across the company and with other companies. * Enables the sharing of ideas, documents, and creative insights to employees and work group that are geographically separated.

Identify each part of an Internet address.

Addresses on the Internet. Each computer on the Internet has an assigned address, called the Internet Protocol (IP) address that distinguishes it from all other computers. The IP address consists of sets of numbers, in four parts, separated by dots. For example, the IP address of one computer might be 135.62.128.91. You can access a Web site by typing this number in the address bar of your browser. Currently, there are two IP addressing schemes. The first scheme, IPv4, is the most widely used. IP addresses using IPv4 consist of 32 bits, meaning that there are 232 possibilities for IP addresses, or 4,294,967,295 distinct addresses. Note that the IP address in the preceding paragraph (135.62.128.91) is an IPv4 address. At the time that IPv4 was developed, there were not as many computers that need addresses as there are today. Therefore, a new IP addressing scheme has been developed, IPv6. IP addresses using IPv6 consist of 128 bits, meaning that there are 2128 possibilities for distinct IP addresses, which is an unimaginably large number. IPv6, which is replacing IPv4, will accommodate the rapidly increasing number of devices that need IP addresses, such as smartphones. IP addresses must be unique so that computers on the Internet know where to find one another. The Internet Corporation for Assigned Names (ICANN) (www.icann.org) coordinates these unique addresses throughout the world. Without that coordination, we would not have one global Internet. Because the numeric IP addresses are difficult to remember, most computers have names as well. ICANN accredits certain companies called registrars to register these names, which are derived from a system called the domain name system (DNS). Domain names consist of mul-tiple parts, separated by dots that are read from right to left. For example, consider the domain name business.auburn.edu. The rightmost part (or zone) of an Internet name is its top-level domain (TLD). The letters edu in business.auburn.edu indicate that this is an educational site. The following are popular U.S. TLDs: com (commercial sites) edu (educational sites) mil (military government sites) gov (civilian government sites) org (organizations) To finish our domain name example, auburn is the name of the organization (Auburn University), and business is the name of the particular machine (server) within the organization to which the message is being sent. A top-level domain is the domain at the highest level in the hierarchical Domain Name Sys-tem of the Internet. The top-level domain names are located in the root zone (rightmost zone) of the name. Management of most TLDs is delegated to responsible organizations by ICANN. ICANN operates the Internet Assigned Numbers Authority (IANA), which is in charge of maintaining the DNS root zone. Today, IANA distinguishes the following groups of TLDs: country-code top-level domains (ccTLD): two letter domains established for countries or territories (ex. de for Germany, ru for Russia) internationalized country code top-level domains (IDN ccTLD): ccTLDs in non-Latin character sets (ex. Arabic or Chinese) generic top-level domains (gTLD): top-level domains with three or more characters. gTLDs initially consisted of .gov, .edu, .com, .mil, .org, and .net.

Compare and contrast the three wireline communications channels.

Communicating data from one location to another requires some form of pathway or medium. A communications channel is such a pathway. It is comprised of two types of media: cable (twisted-pair wire, cable, or fiber-optic cable) and broadcast (microwave, satellite, radio, or infrared).Cable media or wireline media use physical wires or cables to transmit data and information. Twisted-pair wire and coaxial cables are made of copper, and fiber-optic cable is made of glass. The alternative is communication over broadcast media or wireless media. The key to mobile communications in today's rapidly moving society is data transmissions over electro-magnetic media—the "airwaves." In this section you will study the three wireline channels. Table 6.1 summarizes the advantages and disadvantages of each of these channels. You will become familiar with wireless media in Chapter 8. • Twisted-Pair Wire. Twisted-pair wire is the most prevalent form of communications wiring; it is used for almost all business telephone wiring. As the name suggests, it consists of strands of copper wire twisted in pairs (see Figure 6.4). Twisted-pair wire is relatively inexpensive to purchase, widely available, and easy to work with. However, it also has some significant disadvantages. Specifically, it is relatively slow for transmitting data, it is subject to interference from other electrical sources, and it can be easily tapped by unintended receivers to gain unauthorized access to data. • Coaxial Cable. Coaxial cable (Figure 6.5) consists of insulated copper wire. Compared to twisted-pair wire, it is much less susceptible to electrical interference, and it can carry much more data. For these reasons, it is commonly used to carry high-speed data traffic as well as television signals (thus the term cable TV). However, coaxial cable is more expensive and more difficult to work with than twisted-pair wire. It is also somewhat inflexible. • Fiber Optics. Fiber-optic cable (Figure 6.6) consists of thousands of very thin filaments of glass fibers that transmit information via light pulses generated by lasers. The fiber-optic cable is surrounded by clad-ding, a coating that prevents the light from leaking out of the fiber. Fiber-optic cables are significantly smaller and lighter than traditional cable media. They also can transmit far more data, and they provide greater security from interference and tapping. As of mid-2013, optical fiber had reached data transmission rates of more than 50 trillion bits (terabits) per second in laboratory experiments. Fiber-optic cable is typically used as the backbone for a network, whereas twisted-pair wire and coaxial cable connect the backbone to individual devices on the network.

Describe the difference between the Internet and the World Wide Web.

Many people equate the Internet with the World Wide Web. However, they are not the same thing. The Internet functions as a transport mechanism, whereas the World Wide Web is an application that uses those transport functions. Other applications, such as e-mail, also run on the Internet. The World Wide Web (The Web, WWW, or W3) is a system of universally accepted stan-dards for storing, retrieving, formatting, and displaying information via a client/server architec-ture. The Web handles all types of digital information, including text, hypermedia, graphics, and sound. It uses graphical user interfaces (GUIs; explained in Technology Guide 2), so it is very easy to navigate. Organizations that wish to offer information through the Web must establish a home page, which is a text and graphical screen display that usually welcomes the user and provides basic information on the organization that has established the page. In most cases, the home page will lead users to other pages. All the pages of a particular company or individual are collectively known as a Web site. Most Web pages provide a way to contact the organization or the individual. The person in charge of an organization's Web site is its Webmaster. (Note: Webmaster is a gender-neutral title.) To access a Web site, the user must specify a uniform resource locator (URL), which points to the address of a specific resource on the Web. For instance, the URL for Microsoft is http://www.microsoft.com. Recall that HTTP stands for hypertext transport protocol. The remaining letters in this URL—www.microsoft.com—indicate the domain name that identifies the Web server that stores the Web site.Users access the Web primarily through software applications called browsers. Browsers provide a graphical front end that enables users to point-and-click their way across the Web, a process called surfing. Web browsers became a means of universal access because they deliver the same interface on any operating system under which they run.

Describe an enterprise network.

Organizations today have multiple LANs and may have multiple WANs. All of these networks are interconnected to form an enterprise network. Figure 6.2 displays a model of enterprise computing. Note that the enterprise network in the figure has a backbone network. Corporate backbone networks are high-speed central networks to which multiple smaller networks (such as LANs and smaller WANs) connect. The LANs are called embedded LANs because they connect to the backbone WAN.

Differentiate between client/server computing and peer-to-peer processing.

Organizations typically use multiple computer systems across the firm. Distributed processing divides processing work among two or more computers. This process enables computers in different locations to communicate with one another via telecommunications links. A common type of distributed processing is client/server processing. A special type of client/server processing is peer-to-peer processing. Client/Server Computing. Client/server computing links two or more computers in an arrangement in which some machines, called servers, provide computing services for user PCs, called clients. Usually, an organization performs the bulk of its processing or application/data storage on suitably powerful servers that can be accessed by less powerful client machines. The client requests applications, data, or processing from the server, which acts on these requests by "serving" the desired commodity.Client/server computing leads to the ideas of "fat" clients and "thin" clients. As discussed in Technology Guide 1, fat clients have large storage and processing power and therefore can run local programs (such as Microsoft Office) if the network goes down. In contrast, thin clients may have no local storage and only limited processing power. Thus, they must depend on the network to run applications. For this reason, they are of little value when the network is not functioning. Peer-to-Peer Processing. Peer-to-peer (P2P) processing is a type of client/server distributed processing where each computer acts as both a client and a server. Each computer can access (as assigned for security or integrity purposes) all files on all other computers.

What is the difference between LANs and WANs?

Regardless of their size, networks represent a compromise among three objectives: speed, distance, and cost. Organizations typically must select two of the three. To cover long distances, organizations can have fast communication if they are willing to pay for it, or cheap communication if they are willing to accept slower speeds. A third possible combination of the three trade-offs is fast, cheap communication with distance limitations. This is the idea behind local area networks.A local area network (LAN) connects two or more devices in a limited geographical region, usually within the same building, so that every device on the network can communicate with every other device. Most LANs today use Ethernet (discussed later in this chapter). Figure 6.1 illustrates an Ethernet LAN that consists of four computers, a server, and a printer, all of which connect via a shared cable. Every device in the LAN has a network interface card (NIC) that allows the device to physically connect to the LAN's communications medium. This medium is typically unshielded twisted-pair wire (UTP).Although it is not required, many LANs have a file server or network server. The server typi-cally contains various software and data for the network. It also houses the LAN's network operat-ing system, which manages the server and routes and manages communications on the network. When businesses have to transmit and receive data beyond the confines of the LAN, they use wide area networks. Interestingly, the term wide area network did not even exist until local area networks appeared. Before that time, what we call a wide area network today was simply called a "network."A wide area network (WAN) is a network that covers a large geographic area. WANs typically connect multiple LANs. They are generally provided by common carriers such as telephone companies and the international networks of global communications services providers. WANs have large capacity, and they typically combine multiple channels (e.g., fiber-optic cables, microwave, and satellite). The Internet is an example of a WAN. WANs also contain routers. A router is a communications processor that routes messages from a LAN to the Internet, across several connected LANs, or across a wide area network such as the Internet.

Describe the three types of P2Ps.

There are three basic types of peer-to-peer processing. The first type accesses unused CPU power among networked computers. A well-known application of this type is SETI@home(http://setiathome.ssl.berkeley.edu). These applications are from open-source projects, and they can be downloaded at no cost. The second form of peer-to-peer is real-time, person-to-person collaboration, such as Micro-soft SharePoint Workspace (http://office.microsoft.com/en-us/sharepoint-workspace). This product provides P2P collaborative applications that use buddy lists to establish a connection and allow real-time collaboration within the application. The third peer-to-peer category is advanced search and file sharing. This category is characterized by natural-language searches of millions of peer systems. It enables users to discover other users, not just data and Web pages. One example of this category is BitTorrent. BitTorrent (www.bittorrent.com) is an open-source, free, peer-to-peer file-sharing application that simplifies the problem of sharing large files by dividing them into tiny pieces, or "torrents." BitTorrent addresses two of the biggest problems of file sharing: (1) downloading bogs down when many people access a file at once, and (2) some people leech, meaning they download content but refuse to share it. BitTorrent eliminates the bottleneck by enabling all users to share little pieces of a file at the same time—a process called swarming. The program prevents leeching because users must upload a file while they download it. Thus, the more popular the content, the more efficiently it zips over a network.

Describe the Ethernet and TCP/IP protocols.

• Ethernet. A common LAN protocol is Ethernet. Most large corporations use 10-gigabit Ethernet, where the network provides data transmission speeds of 10 gigabits (10 billion bits) per second. However, 100-gigabit Ethernet is emerging. • Transmission Control Protocol/Internet Protocol. The Transmission Control Protocol /Internet Protocol (TCP/IP) is the protocol of the Internet. TCP/IP uses a suite of protocols, the main ones being the Transmission Control Protocol (TCP) and the Internet Protocol (IP). The TCP performs three basic functions: (1) It manages the movement of packets between computers by establishing a connection between the computers, (2) it sequences the transfer of packets, and (3) it acknowledges the packets that have been transmitted. The Internet Protocol (IP) is responsible for disassembling, delivering, and reassembling the data during transmission. Before data are transmitted over the Internet, they are divided into small, fixed bundles called packets. The transmission technology that breaks up blocks of text into packets is called packet switching. Each packet carries the information that will help it reach its destination—the sender's IP address, the intended receiver's IP address, the number of packets in the message, and the number of the particular packet within the message. Each packet travels independently across the network and can be routed through different paths in the network. When the packets reach their destination, they are reassembled into the original message. It is important to note that packet-switching networks are reliable and fault tolerant. For example, if a path in the network is very busy or is broken, packets can be dynamically ("on the fiy") rerouted around that path. Also, if one or more packets does not get to the receiving computer, then only those packets need to be resent. Why do organizations use packet switching? The main reason is to achieve reliable end-to-end message transmission over sometimes unreliable networks that may have transient (short-acting) or persistent (long-acting) faults. The packets use the TCP/IP protocol to carry their data. TCP/IP functions in four layers (see Figure 6.7). The application layer enables client application programs to access the other layers, and it defines the protocols that applications use to exchange data. One of these application protocols is the Hypertext Transfer Protocol (HTTP), which defines how messages are