Sustainability Research Paper Example | Topics and Well Written Essays - 1000 words

Supportability - Research Paper Example Truth be told, it is a typical confusion that the nearness of worldwide financial emergency could a zero development rate in the interest for global the travel industry. As per Reisinger (2009, p. 8), the travel industry includes the development of â€Å"goods, administrations, and people†. Thus, the setting of worldwide the travel industry is exceptionally expansive as in this idea incorporates not just individuals who are going for recreation purposes (for example excursion purposes or visiting untamed life attractions, workmanship exhibitions, historical centers, and a nearby celebration, and so on.) (Felsenstein and Fleischer, 2003) yet in addition those people who are moving to another nation in look for new business or business openings (Baum, 2006; Lundmark, 2006). Globalization has something to do with the persistently expanding interest for universal the travel industry. Truth be told, noteworthy change that is as of now happening in the pattern of universal the trave l industry turned out to be progressively unpredictable and quick paced as a result of globalization as well as because of the accessibility of advance correspondence innovation (Reisinger, 2009, p. 8; Formica and Kothari, 2008; Kyriaki and Vogt, 2006; Morrison, Taylor, and Douglas, 2004). Hence, Reisinger (2009, p. 27) clarified that globalization is the mystery behind the opening of new business openings and development in worldwide the travel industry. ... Other than the perpetual or legally binding remote specialists, social the travel industry additionally incorporates low-salary government representatives who are alloted to work outside their country (Bhatia, 2001, p. 55). It is generally less expensive and simpler to enlist exceptionally serious people from outside nations. Subsequently, one of the primary reasons why organizations in created nations are employing remote specialists is to chop down the fixed expense of work. Corresponding to the on-going free exchanging of work powers, a large number of individuals every year are relied upon to make a trip starting with one nation then onto the next (Baum, 2006; Lundmark, 2006). In scan for a superior money related pay, many individuals from creating or immature regions will persistently endeavor to search for better work openings in created nations. This clarifies why the quantity of unlawful settlers and low-gifted specialists who are moving to UK is too much higher than anticipa ted (Beckford, 2012; Jowit, 2012). To control the expanding number of illicit transients, the UK government is firm in its choice to oust back unlawful settlers to their country (Beckford, 2012). This could by one way or another expansion the quantity of explorers every year. Rather than driving illicit settlers to return back to their mom land, President Obama chose to suspend the extradition and lawfully permit 1.7 million unlawful outsiders to work in the United States (Emmanuel, 2012; Preston, 2012a, 2012b). By and large, the nearness of financial downturn brought about by regular catastrophes can start new business open doors for some private areas. Such occurrence could in the end open new business and work openings not just with respect to exceptionally legitimate specialists yet additionally the engineers

Child Socialization Essay

What are the operators of kids Socialization? Socialization Agents Presentation What is a specialist of socialization? An operator of socialization is individuals and gatherings that impact our self-idea, feelings, perspectives and conduct. There are five operators that assume a job in the socialization of kids. Each specialist of socialization assumes a job in the improvement of youngsters. In this article I play on portraying the five specialists and how they help in youngster improvement. The five mingling operators comprise of Family, School and Childcare, Peers, Mass media, and Community. As kids develop and change the measure of impact of every operator changes. Youngsters will figure out how to create trust, freedom, the inclination to step up to the plate, the feeling of skill and aspiration, the choice on what our identity is, our associations with others, and reflections on life by and large. Family Peruse more: Personal factors that influence kid advancement paper The family capacities to find kids socially, and assumes a significant job in their socialization. Raising a family is rarely simple. With the end goal for everything to run easily, every individual has a task to carry out. People learn and create to be the grown-up individual that they become. As the youngster creates and propels in psychosocial advancement, the specialists become more grounded or more vulnerable in their ability for impact. From the get-go in a child’s improvement, the family is, obviously, the most grounded operator, however as the youngster advances to preschool age, projects or schools start to apply impact. At young, peers are dynamic socialization operators. School and Child Care In younger students are place outside the immediate control of the family, and need to figure out how to turn into a piece of a friend gathering. Kids in sports will learn socialization aptitudes and qualities. Instruction is the procedure by which society transmits its aggregated information, abilities, customs and qualities starting with one age then onto the next. It occurs through any experience that has aâ formative impact in transit one thinks, feels, or acts. With more moms working in our general public childcare has become a noteworthy specialist of socialization. Families need to search for a guardian who gives warm, cherishing care and direction for the youngster and works with the family to guarantee that the kid creates in the most ideal manner conceivable. The guardians must have a setting that protects the youngster, secure and solid; and formatively suitable exercises that help the kid grow inwardly, socially, intellectually and genuinely. Friends Companion bunches offer help for kids as they change into the grown-up society. Youngsters begin diminishing reliance on guardians. They will expand sentiment of independence, and associating with an a lot bigger interpersonal organization. The term â€Å"peer pressure† is frequently used to portray examples where an individual feels by implication constrained into changing their conduct to coordinate that of their friends. Friend bunches impact mental and social alterations for bunch people. They give point of view outside of individual’s perspectives. Individuals inside friend bunches likewise figure out how to create associations with others in the social framework. Broad communications Broad communications emerges as correspondence innovation spreads data on another scale. The broad communications enormously affect a mass scale. The broad communications spread a wide scope of methods for correspondence, data and amusement, for example, books, music, papers and magazines, radio, TV, the Internet just as computer games. The broad communications enormously affect our perspectives and practices. It additionally influences our perspective. At the point when we go out shopping we are going to need to purchase what we just observed on the TV. The depiction of human characters in various projects and its notices on TV impacts our point of view on what is solid, cool, or the upgraded IT thing that we currently need to run out and buy. Similar projects help in forming the perspectives, qualities, and essential direction of individuals to life. Network The term network has two particular commutative implications: 1) Community can allude to a normally little, social unit of any size that shares basic qualities. The term can likewise allude to the national network or global network, and 2) in science, a network is a gathering of communicating living life forms sharing a populated situation. Local gatherings can give kids alternate points of view. The area of what kind of network you live in will influence your kid socialization. It has been demonstrated that youngsters in a lower financial network are bound to perpetrate wrongdoings, drink, and medications. End There are numerous elements that impact your youngster and the manner in which your kid will get free. Each youngster will be brought up in contrast societies, school, and situations. Every youngster is extraordinary; one kid may accept a commendation as a commendation while a kid with low confidence may see an affront. I feel that the family assumes the greatest job with advancement with the kid. These five instances of impacts on our socialization are significant in forming the grown-up that we will turn into. References: 1. http://www.merriam-webster.com/word reference/network 2. www.boundless.com 3. Youngster, Family, School, Community Socialization and backing (ninth release). Roberta M. Berns.

Advantages of Online Paper Writing Services

Advantages of Online Paper Writing ServicesThe online term paper writing services has become more popular now, than ever before. Because of the internet, it is no longer necessary to go to a real paper company or library to get free help. You can simply search on Google for something like 'online paper writing services' and you will find many websites that have this type of assistance.However, just because you are looking for a certain service doesn't mean that you should be totally disappointed if you do not find it. You can get paper at a cheaper price than what you can get at your local library. You can also try to find an online resource where you can learn from someone who is already making use of these services. This way, you will be able to compare prices.Paper writing services offer you the opportunity to write your paper without any worry. In the past, people would try to take care of their papers for them and would often struggle with this. Nowadays, you can take out a cred it card and pay them for their services. This way, you will be able to write your papers on your own and get them back tomorrow or maybe even in a week.One of the advantages of this new service is that you can get your work completed in one sitting. You can download the papers when you are done with them. This way, you won't have to worry about having a slow computer or needing to connect your computer to the internet. All of this happens automatically and you can continue working on your other tasks.You can also put the papers together yourself. The other option you have is to have them mailed back to you. This can make things easier, but it will still cost you money.Another advantage of online paper writing services is that you will get personalized help. Instead of getting all of the same paper on all of the days that you are writing, you will be getting different ones on each day. This is helpful if you have a lot of papers to get done or if you have to send them out as fast as possible. By doing this, you will also be able to set your own schedule for yourself.No matter what type of paper you are working on, you will be able to get one for free. Most of the time, you will be asked to send a resume, so they can get a feel for your writing skills. They will also be able to see if you can write a specific style of paper. If they feel that you are capable of writing the particular paper, they will mail it to you for free.Once you have gotten all of your papers, you will need to take them to an approved place for handling paper. This is important to make sure that the paper does not get damaged. It can be very frustrating when your paper is damaged and you need to wait for the fix, but because of the high prices that are associated with sending it to a storage facility, you may be forced to pay for that.

New Place, Shakespeares Home in Stratford-upon-Avon

​When Shakespeare retired from London around 1610, he spent the last few years of his life in New Place, one of Stratford-upon-Avon’s largest houses, which he purchased in 1597. Unlike Shakespeare’s birthplace on Henley Street, New Place was pulled down in the 18th century. Today, Shakespeare fans can still visit the site of the house which has now been turned into an Elizabethan garden. Nash’s House, the building next door, still remains and serves as a museum dedicated to Tudor life and New Place. Both sites are cared for by the Shakespeare Birthplace Trust.​ New Place New Place, once described as a â€Å"pretty house of brick and timber,† was built towards the end of the 15th century and bought by Shakespeare in 1597 although he did not live there until his retirement from London in 1610. On display in the adjoining museum is a sketch of New Place by George Vertue showing the main house (where Shakespeare lived) enclosed by a courtyard. These street-facing buildings would have been the servant’s quarters. Francis Gastrell New Place was demolished and rebuilt in 1702 by the new owner. The house was rebuilt in brick and stone but it only survived another 57 years. In 1759, the new owner, Reverend Francis Gastrell, quarreled with the town authorities over taxation and Gastrell had the house permanently demolished in 1759. New Place was never again rebuilt and only the foundations of the house remain. Shakespeare’s Mulberry Tree Gastrell also caused controversy when he removed Shakespeare’s mulberry tree. It is said that Shakespeare planted a mulberry tree in the gardens of New Place, which posthumously attracted visitors. Gastrell complained that it made the house damp and he had it chopped for firewood or perhaps Gastrell wanted to deter the visitors! Thomas Sharpe, an enterprising local clockmaker and carpenter, bought most of the wood and carved Shakespeare mementos from it. The museum in Nash’s House displays some of the artifacts said to be made from Shakespeare’s mulberry tree.

The Forgotten Dead By William D. Carrigan And Clive Webb

â€Å"Forgotten Dead† by authors William D. Carrigan and Clive Webb, delivered a collective narration of the numerous lynching crimes against Mexican people in the southern west states of the United States. Their purpose was to describe that extend of mob violations against the minority groups of people in the United States. By, arguing how many of these racial crimes were prejudice to eliminate the potential competition for territory, and gold mines’ economy that were potentially able to provide the envy position that Anglo people were afraid to loose. They wanted to figure out, who these forgotten dead Mexicans were at the time, and what types of â€Å"crimes† they committed to face such cruelty death in the hands of the mob Anglo groups. They uncovered the grand extend of violent scenes that Anglo vigilantes members of mob groups organized the banishment of many Mexican in what they had considered part of their territory at the time. They were Anglo racial mo bs that created freighted violence of lynching, decapitation, gun downs, mutilation, burnings, and many more crimes that not only were committed to Mexican but other minority groups residing in former Mexican territories. Perhaps Mexican population was not the only target to these mob lynching groups, they demonstrated how many African Americans, Chileans, and Chinese also were brutally killed, but the evidence given still portray the big difference of hate against these other races. The authors also explained well the

Should Abortion Be Legal - 1481 Words

Abortion has been around for many years. It is a very popular method to rid the woman’s body of an unborn child. Overtime the laws have changed drastically about abortion and women’s rights. Back in the 13th century abortion was considered homicide and was punishable by hanging. Later it became legal only if it was necessary to save a woman’s life. Eventually things got out of hand and abortion was banned completely, then slowly the laws came back into play after half a century (Rich and Wagner). Abortion for many people is considered okay as long as it is the woman’s choice, but other people think it is wrong and should be considered as murder to a human life. Although abortion is a very hot topic in today’s society is it really the best†¦show more content†¦They are normally involved in pro-choice organizations. Their mission is to try and educate women about abortion in a positive manner and make them feel secure about their decisions. T hey feel that it is the woman’s right to be able to choose what they feel is best. Between these two groups of people there are many contributing factors that make them feel and act the way they do. One of the contributing factors as to why people feel that abortion should be banned completely is their religious beliefs. Religion is a sufficient cause and is a very hot topic just like abortion. Different religions each have their own viewpoints on abortion. According to â€Å"Religious views on abortion† it states that early Christian traditions are against abortion because the Bible repeatedly refers to children before birth as very small/young children. As said in the Bible â€Å"children are a gift from the lord; they are a reward from him† (Psalm 127:3). Therefore children are a gift from God and they should be cherished. Also said in the bible is â€Å"you must not murder† (Exodus 20:13). Another religion, such as Catholics, is against abortion because they believe that life is very sacred. An unborn baby inside a mother’s womb has no voice and no power and is considered innocent. The pro-life believers feel that there are many other options out

Computer Engineer free essay sample

After reading this chapter and completing the exercises, you will be able to: ? ? ? Describe the primary physical networking topologies in common use Describe the primary logical networking topologies in common use Describe major LAN networking technologies 109 Copyright 2011 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. 110 Chapter 3 Not so long ago, there was a real choice to be made between available network topologies and technologies when designing and building a new internetwork. Thankfully, this area of networking has gotten simpler rather than more complex, mainly because the choices have narrowed, with inferior or costly solutions becoming obsolete. This chapter discusses network topologies, which describe both the physical arrangement of cabling or pathways between network devices and the logical manner in which data is transferred from device to device. Next, you learn about network technologies or architectures that describe the methods computers use to transmit data to the networking medium in an orderly fashion. As you’ll see, the topology and technology are often tightly coupled, as certain technologies can be used only with certain topologies. The choices have been limited because only a few technologies and topologies remain as viable options. As is often the case, however, it helps to know where networking started to get an idea of where it might be heading. So even though some information covered in this chapter is obsolete or nearly so, your understanding of these older technologies will help you better understand current and future technologies. Physical Topologies The word â€Å"topology,† for most people, describes the lay of the land. A topographic map, for example, shows the hills and valleys in a region, whereas a street map shows only the roads. A network topology describes how a network is physically laid out and how signals travel from one device to another. However, because the physical layout of devices and cables doesn’t necessarily describe how signals travel from one device to another, network topologies are categorized as physical and logical. The arrangement of cabling and how cables connect one device to another in a network are considered the network’s physical topology, and the path data travels between computers on a network is considered the network’s logical topology. You can look at the physical topology as a topographic map that shows just the lay of the land along with towns, with only simple lines showing which towns have pathways to one another. The logical topology can be seen as a street map that shows how people actually have to travel from one place to another. As you’ll see, a network can be wired with one physical topology but pass data from machine to machine by using a different logical topology. All network designs today are based on these basic physical topologies: bus, star, ring, and point-to-point. A bus consists of a series of computers connected along a single cable segment. Computers connected via a central device, such as a hub or switch, are arranged in a star topology. Devices connected to form a loop create a ring. Two devices connected directly to one another make a point-to-point topology. Keep in mind that these topologies describe the physical arrangement of cables. How the data travels along these cables might represent a different logical topology. The dominant logical topologies in LANs include switching, bus, and ring, all of which are usually implemented as a physical star (discussed later in â€Å"Logical Topologies†). Physical Bus Topology The physical bus topology, shown in Figure 3-1, is by far the simplest and at one time was the most common method for connecting computers. It’s a continuous length of cable Copyright 2011 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Physical Topologies 111 3 Figure 3-1 A physical bus topology network Courtesy of Course Technology/Cengage Learning  connecting one computer to another in daisy-chain fashion. One of this topology’s strengths is that you can add a new computer to the network simply by stringing a new length of cable from the last computer in the bus to the new machine. However, this strength is countered by a number of weaknesses: ? There’s a limit of 30 computers per cable segment. ? The maximum total length of cabling is 185 meters. ? Both ends of the bus must be terminated. ? Any break in the bus brings down the entire network. ? Adding or removing a machine brings down the entire network temporarily. ? Technologies using this topology are limited to 10 Mbps half-duplex communication because they use coaxial cabling, discussed in Chapter 4. Because of the preceding limitations, a physical bus topology is no longer a practical choice, and technology has moved past this obsolete method of connecting computers. However, the original Ethernet technology was based on this topology, and the basis of current LAN technology has its roots in the physical bus. So your understanding of bus communication aids your general understanding of how computers communicate with each other across a network. How Data Travels in a Physical Bus Two properties inherent in a physical bus are signal propagation and signal bounce. In any network topology, computers communicate with each other by sending information across the media as a series of signals. When copper wire is the medium, as in a typical physical bus, these signals are sent as a series of electrical pulses that travel along the cable’s length in all directions. The signals continue traveling along the cable and through any connecting devices until they weaken enough that they can’t be detected or until they encounter a device that absorbs them. This traveling across the medium is called signal propagation. However, even if a signal encounters the end of a cable, it bounces back and travels in the other direction until it weakens or is otherwise impeded. When a signal hits the end of a cable and bounces back up the cable’s length, it interferes with signals following it, much like an echo. Imagine if you were trying to communicate Copyright 2011 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. 112 Chapter 3 in an empty room with hard walls that caused your voice to echo continuously. The echo from the first words out of your mouth would garble the sound of words that followed, and your message would be unintelligible. The term used when electricity bounces off the end of a cable and back in the other direction is called signal bounce or reflection. To keep signal bounce from occurring, you do what you would to keep excessive echo from occurring; you install some type of material at both ends of the medium to absorb the signal. In a physical bus, you install a terminator, which is an electrical component called a resistor that absorbs the signal instead of allowing it to bounce back up the wire. Physical Bus Limitations Now that you know more about how a physical bus works, the previous list of weaknesses needs some additional explanation. The limitation of 30 stations per cable segment means only 30 computers can be daisy-chained together before the signal becomes too weak to be passed along to another computer. As an electrical signal encounters each connected workstation, some of its strength is absorbed by both the cabling and the connectors until the signal is finally too weak for a computer’s NIC to interpret. For the same reason, the total length of cabling is limited to 185 meters, whether there’s 1 connected station or 30 connected stations. The network can be extended in cable length and number of workstations by adding a repeater to the network, which, as you know, regenerates the signal before sending it out. At all times, both ends of the bus must be terminated. An unterminated bus results in signal bounce and data corruption. When a computer is added or removed from the network, both ends are no longer terminated, resulting in an interruption to network communication. For a small network of only a few computers, you might think a bus topology is fine, until you consider the last weakness listed: maximum bandwidth of 10 Mbps half-duplex communication. A physical bus uses coaxial cable (a cabling type discussed in Chapter 4, similar to what’s used in cable TV connections), which is limited to a top speed of 10 Mbps and communication in only half-duplex mode. Most of today’s networks use twisted-pair cabling, which can operate at 100 Mbps or faster and run in full-duplex mode, so communication between devices is much faster. For all these reasons, the physical bus topology has long since fallen out of favor and been replaced largely by the star topology, discussed next. Physical Star Topology The physical star topology uses a central device, such as a hub or switch, to interconnect computers in a LAN (see Figure 3-2). Each computer has a single length of cable going from its NIC to the central device. Some advantages of a physical star topology are the following: ? Much faster technologies are used than in a bus topology. ? Centralized monitoring and management of network traffic is possible. ? Network upgrades are easier. A physical star is the topology of choice for these reasons and more. With a central device, communication options are available that simply aren’t possible with a physical bus. For example, the central device can be a 100 Mbps hub, which increases a physical bus’s top Copyright 2011 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Physical Topologies 113 3 Switch Figure 3-2 A physical star topology network Courtesy of Course Technology/Cengage Learning speed tenfold, or a switch, making it possible for multiple communication sessions to occur simultaneously and in full-duplex mode. As a budding network administrator, being able to monitor and manage your network with a central device is a big advantage over what was possible with a physical bus topology. Today’s hubs and switches can include software that collects statistics about your network traffic patterns and even alerts you when excessive errors or unusually high traffic rates are occurring on your network. You don’t get these features in a $19. 99 hub or switch, but  enterprise-level devices can be equipped with several network management tools. As long as your current cabling and installed NICs support it, your network can be upgraded quickly and easily from a ponderous 10 Mbps hub-based LAN to a blazing fast 100 Mbps or even 1000 Mbps switched network simply by replacing the central device. In addition, if your NICs must also be upgraded, you can upgrade in steps because most devices support multiple speeds. So if you want to upgrade from 100 Mbps to 1000 Mbps, you can replace the central device with a switch that supports both speeds, and then upgrade NICs as time and money allow. The switch transmits and receives on each port at the speed supported by the NIC connected to that port. What happens if the number of workstations you need to connect exceed the number of ports on the central device? In this case, you can connect hubs or switches, as you learned in Chapter 2. When several hubs or switches must be connected, usually one device is used as the central connecting point, forming an extended star. Extended Star The extended star topology, shown in Figure 3-3, is the most widely used in networks containing more than just a few computers. As the name implies, this topology is a star of stars. A central device, usually a switch, sits in the middle. Instead of attached computers forming the star’s arms, other switches (or hubs) are connected to the central switch’s ports. Computers and peripherals are then attached to these switches or Copyright 2011 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. 114 Chapter 3 Switch Switch Switch Switch Switch Figure 3-3 An extended star topology network Courtesy of Course Technology/Cengage Learning hubs, forming additional stars. The extended star is sometimes referred to as a â€Å"hierarchical star† because there are two or more layers of stars, all connecting back to the central star. The extended star can be used to connect many computers, with the central device running at a very fast speed to shuttle data between the LAN’s outer stars. This topology is most effective when the center of the star is running at a much faster speed than other devices; for example, the central device can run at 1000 Mbps while other devices run at 100 Mbps. How Data Travels in a Physical Star The details of how data travels from computer to computer in a physical star depend on the type of central device. Data transmission starts at a device at the end of one of the central device’s arms. From there, it travels along the network medium’s length until it arrives at the central device. As you know from learning how hubs and switches work, the transmission path differs, depending on the device. Other devices, such as multistation access units (MAUs) used in token ring networks, move data differently. The type of central device, therefore, determines the logical topology, discussed later in this chapter. Physical Star Disadvantages With all the clear advantages of a physical star, you might wonder whether there are any disadvantages. None outweigh the advantages, but it’s worth mentioning that the central device represents a single point of failure. In other words, if the hub or switch fails or  someone kicks the power cord out of the outlet, down goes the entire network. Thankfully, these devices tend to be reliable and are usually placed out of the way of everyday foot traffic. That being said, they do fail from time to time, and having a spare on hand is a good idea. When a physical bus was still the norm and the physical star was just coming on the networking scene in the late 1980s, it was often argued that because each computer must be Copyright 2011 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Physical Topologies 115 cabled directly to the central device, instead of a bus’s daisy-chain arrangement, more cable was required to connect computers. This point is indeed true, and at the time, the amount of cabling needed was a factor in designing a network with a bus or star arrangement. By the time the star network’s advantages were fully realized in the mid-1990s, however, the cabling cost difference had diminished substantially, and the advantages clearly outweighed the minor cost disadvantage. Physical Ring Topology A physical ring topology is like a bus, in that devices are daisy-chained one to another, but instead of terminating each end, the cabling is brought around from the last device back to the first device to form a ring. This topology had little to no following in LANs as a way to connect computers. It was used, however, to connect LANs with a technology called Fiber Distributed Data Interface (FDDI). FDDI was most often used as a reliable and fast network backbone, which is cabling used to communicate between LANs or between hubs or switches. In Figure 3-4, the devices used to connect buildings form a ring, but computers on each LAN are connected with a physical star topology. Building C LAN switch FDDI hub Building A Building B Figure 3-4 A physical ring topology is usually used to connect LANs Courtesy of Course Technology/Cengage Learning The physical ring also had reliability issues because data had to be forwarded from one station to the next. Unlike a bus, in which data travels in all directions and is terminated at both ends, a ring doesn’t have any beginning or end. So each station must reproduce data and pass it along to the next station until it reaches the destination or the originator of the data. In other words, data always travels in one direction. If any station in the ring fails, data can no longer be passed along, and the ring is broken. Technologies such as FDDI overcome some problems with a physical ring network by creating a dual ring, in which data can travel in both directions so that a single device failure doesn’t break the entire ring. However, this technology is costly, and although it was used extensively in the 1990s and early 2000s because it was fast (100 Mbps) and reliable, 100 Mbps and 1000 Mbps Ethernet have largely supplanted it with an extended star technology. Copyright 2011 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially  affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. 3 116 Chapter 3 Point-to-Point Topology As its name implies, a point-to-point topology is a direct link between two devices. It’s most often used in WANs, in which a device on a business’s network has a dedicated link to a telecommunication provider, such as the local phone company. The connection then hooks into the phone company’s network to provide Internet access or a WAN or MAN link to a branch office. The advantage of this type of topology is that data travels on a dedicated link, and its bandwidth isn’t shared with other networks. The disadvantage is that this topology tends to be quite expensive, particularly when used as a WAN link to a distant branch office. Point-to-point topologies are also used with wireless networks in what’s called a wireless bridge. This setup can be used to connect two buildings without using a wired network (see Figure 3-5) or to extend an existing wireless network. Figure 3-5 A point-to-point wireless topology Courtesy of Course Technology/Cengage Learning A rudimentary LAN can also be set up with a point-to-point topology by connecting a cable between the NICs on two computers. Of course, this method allows only two computers on the network, but it can be used effectively for transferring files from one computer to another in the absence of a hub or switch. So as you can see, point-to-point topologies are used for specialized purposes. They aren’t commonly used in LANs; they’re used more often in WANs and large internetworks. Mesh Topology A mesh topology connects each device to every other device in a network. You can look at a mesh topology as multiple point-to-point connections for the purposes of redundancy and fault tolerance. Figure 3-6 shows a full mesh topology between four locations, with the switch in each location providing connectivity to multiple computers. Each switch is connected to every other switch, which is called a â€Å"full mesh. † If each switch were connected to only two other switches, it would be called a â€Å"partial mesh. † In either case, the purpose of creating a mesh topology is to ensure that if one or more connections fail, there’s another path for reaching all devices on the network. For example, in Figure 3-6, two connections could fail, but all devices could still communicate with one another. This type of topology is used mostly commonly in large internetworks and WANs, where routers or switches in multiple buildings or towns are connected in a partial or full mesh. Parts of the Internet are also designed with a partial mesh topology, in which major ISPs are connected so that even if one ISP’s network fails, data can bypass this part of the network to get to its destination. Mesh topologies, although reliable, are also expensive because of the additional cabling and ports required. In most cases, the ports used to connect devices are the highest speed available, such as 1 Gbps or 10 Gbps, and they often use expensive fiber-optic cabling for connecting buildings. Copyright 2011 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Logical Topologies Chicago 117 New York WAN link 3 Los Angeles Phoenix Figure 3-6 Switches in each building are connected in a full mesh topology Courtesy of Course Technology/Cengage Learning Logical Topologies As mentioned, a network’s logical topology describes how data travels from computer to computer. In some cases, as with a physical bus and physical ring, the logical topology mimics the physical arrangement of cables. In other cases, as with a physical star, the electronics in the central device determine the logical topology. A network’s logical topology reflects the underlying network technology (covered later in â€Å"Network Technologies†) used to transfer frames from one device to one another. Table 3-1 summarizes the main logical topologies, the technologies using them, and the physical topologies for implementing them. Table 3-1 Logical topology Bus Logical topologies and associated network technologies and physical topologies Network technology Ethernet Physical topology Bus or star Wireless LANs Star Description A logical bus topology can be implemented as a physical bus (although this topology is now obsolete). When a logical bus is implemented as a physical star using wired Ethernet, the center of the star is an Ethernet hub. Whatever the physical topology is, data transmitted from a computer is received by all other computers. Wireless LANs use a physical star topology because they connect through a central access point. However, only one device can Copyright 2011 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. 118 Chapter 3 Table 3-1 Logical topology Logical topologies and associated network technologies and physical topologies (continued ) Network technology Physical topology Description transmit at a time and all devices hear the transmission, so a wireless LAN can be considered a logical bus topology. Ring Star Token ring networks use a central device called a multistation access unit (MAU or MSAU). Its electronics form a logical ring, so data is passed from computer to computer in order, until it reaches the destination device. FDDI Switched Token ring Ring As discussed, FDDI devices are connected in a physical ring, and data passes from device to device until it reaches the destination. Ethernet Star A switched logical topology using a physical star topology running Ethernet is by far the most common topology/technology combination now and likely will be well into the future. A switched topology creates dynamic connections or circuits between two devices whenever data is sent. This topology is  sometimes considered a switched point-to-point topology because a circuit is established between two points as needed to transfer data (like turning on a switch), and then the circuit is broken when it’s no longer needed (like turning off a switch). You have seen what a logical bus looks like when implemented as a physical bus. All computers are daisy-chained to one another, and network signals travel along the cable’s length in all directions, much like water flowing through interconnected pipes. When a logical bus is implemented as a physical star, the same process occurs, but the pathways are hidden inside the central hub. Figure 3-7 shows what a logical bus might look like when implemented with a hub. Signal Signal Logical bus inside a network hub Signal Signal Figure 3-7 A logical bus implemented as a physical star Courtesy of Course Technology/Cengage Learning Copyright 2011 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the righ to remove additional content at any time if subsequent rights restrictions require it. Logical Topologies 119 A logical bus is sometimes called a â€Å"shared media topology† because all stations must share the bandwidth the media provides. A logical ring using a physical star implements the ring inside the central device’s electronics, which is an MAU in the token ring technology. Data is passed from one node or computer to another until it reaches the destination device (see Figure 3-8). When a port has no device connected to it, it’s simply bypassed, and data is sent out the next connected port. Figure 3-8 A logical ring implemented as a physical star Courtesy of Course Technology/Cengage Learning A switched topology works something like what’s shown in Figure 3-9. Although there’s always an electrical connection between the computer and switch, when no data is being transferred, there’s no logical connection or circuit between devices. However, when the switch receives a frame, a logical circuit is made between the source and destination devices until the frame is transferred. PC 4 PC 5 PC 6 No packets being transmitted PC 1 PC 2 PC 3 PC 1 and PC 6 communicate while PC 2 and PC 5 communicate Figure 3-9 The logical functioning of a switch Courtesy of Course Technology/Cengage Learning Copyright 2011 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.