Surplus computer means that manufacturer excess, overstock, and slightly obsolete inventories in huge quantities were purchased. What that means for you, our customer, is truly remarkable discount computer prices! These benefits and values of surplus computers were traditionally available to only large volume commercial buyers, dealers, and corporate level buyers. Also, discount computers are also sold retail so you can get all the benefits too.
The sellers of surplus computers and discount computers are committed to offering tremendous savings to you, the retail customer. Desktop PCs, laptops, notebooks, barebones, whole computer systems, computer accessories, everything in computers you can find in surplus and discount computers.
Sometimes repackaged products are sold as - continued below ...
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surplus computers or discount computers but they are always evaluated, tested and quality assured, fully functional and repackaged for shipment.
Sometimes sold as surplus computers or discount computers are open Box products which are retested, quality assured, fully functional and complete. The customer can expect original manufacturer packaging.
Monday, August 2, 2010
What is a Topology?
The physical topology of a network refers to the configuration of cables, computers, and other peripherals. Physical topology should not be confused with logical topology which is the method used to pass information between workstations. Logical topology was discussed in the Protocol chapter .
Main Types of Physical Topologies
The following sections discuss the physical topologies used in networks and other related topics.
Linear Bus
Star
Star-Wired Ring
Tree
Considerations When Choosing a Topology
Summary Chart
Linear Bus
A linear bus topology consists of a main run of cable with a terminator at each end (See fig. 1). All nodes (file server, workstations, and peripherals) are connected to the linear cable. Ethernet and LocalTalk networks use a linear bus topology.
Advantages of a Linear Bus Topology
•Easy to connect a computer or peripheral to a linear bus.
•Requires less cable length than a star topology.
Disadvantages of a Linear Bus Topology
•Entire network shuts down if there is a break in the main cable.
•Terminators are required at both ends of the backbone cable.
•Difficult to identify the problem if the entire network shuts down.
•Not meant to be used as a stand-alone solution in a large building.
Star
A star topology is designed with each node (file server, workstations, and peripherals) connected directly to a central network hub or concentrator
Data on a star network passes through the hub or concentrator before continuing to its destination. The hub or concentrator manages and controls all functions of the network. It also acts as a repeater for the data flow. This configuration is common with twisted pair cable; however, it can also be used with coaxial cable or fiber optic cable.
Advantages of a Star Topology
•Easy to install and wire.
•No disruptions to the network then connecting or removing devices.
•Easy to detect faults and to remove parts.
Disadvantages of a Star Topology
•Requires more cable length than a linear topology.
•If the hub or concentrator fails, nodes attached are disabled.
•More expensive than linear bus topologies because of the cost of the concentrators.
The protocols used with star configurations are usually Ethernet or LocalTalk. Token Ring - continued below ...
continued ...
uses a similar topology, called the star-wired ring.
Star-Wired Ring
A star-wired ring topology may appear (externally) to be the same as a star topology. Internally, the MAU (multistation access unit) of a star-wired ring contains wiring that allows information to pass from one device to another in a circle or ring (See fig. 3). The Token Ring protocol uses a star-wired ring topology.
Tree
A tree topology combines characteristics of linear bus and star topologies. It consists of groups of star-configured workstations connected to a linear bus backbone cable (See fig. 4). Tree topologies allow for the expansion of an existing network, and enable schools to configure a network to meet their needs.
Advantages of a Tree Topology
•Point-to-point wiring for individual segments.
•Supported by several hardware and software venders.
Disadvantages of a Tree Topology
•Overall length of each segment is limited by the type of cabling used.
•If the backbone line breaks, the entire segment goes down.
•More difficult to configure and wire than other topologies.
5-4-3 Rule
A consideration in setting up a tree topology using Ethernet protocol is the 5-4-3 rule. One aspect of the Ethernet protocol requires that a signal sent out on the network cable reach every part of the network within a specified length of time. Each concentrator or repeater that a signal goes through adds a small amount of time. This leads to the rule that between any two nodes on the network there can only be a maximum of 5 segments, connected through 4 repeaters/concentrators. In addition, only 3 of the segments may be populated (trunk) segments if they are made of coaxial cable. A populated segment is one which has one or more nodes attached to it . In Figure 4, the 5-4-3 rule is adhered to. The furthest two nodes on the network have 4 segments and 3 repeaters/concentrators between them.
This rule does not apply to other network protocols or Ethernet networks where all fiber optic cabling or a combination of a fiber backbone with UTP cabling is used. If there is a combination of fiber optic backbone and UTP cabling, the rule is simply translated to 7-6-5 rule.
Considerations When Choosing a Topology:
•Money. A linear bus network may be the least expensive way to install a network; you do not have to purchase concentrators.
•Length of cable needed. The linear bus network uses shorter lengths of cable.
•Future growth. With a star topology, expanding a network is easily done by adding another concentrator.
•Cable type. The most common cable in schools is unshielded twisted pair, which is most often used with star topologi
About the Author
The physical topology of a network refers to the configuration of cables, computers, and other peripherals. Physical topology should not be confused with logical topology which is the method used to pass information between workstations. Logical topology was discussed in the Protocol chapter .
Main Types of Physical Topologies
The following sections discuss the physical topologies used in networks and other related topics.
Linear Bus
Star
Star-Wired Ring
Tree
Considerations When Choosing a Topology
Summary Chart
Linear Bus
A linear bus topology consists of a main run of cable with a terminator at each end (See fig. 1). All nodes (file server, workstations, and peripherals) are connected to the linear cable. Ethernet and LocalTalk networks use a linear bus topology.
Advantages of a Linear Bus Topology
•Easy to connect a computer or peripheral to a linear bus.
•Requires less cable length than a star topology.
Disadvantages of a Linear Bus Topology
•Entire network shuts down if there is a break in the main cable.
•Terminators are required at both ends of the backbone cable.
•Difficult to identify the problem if the entire network shuts down.
•Not meant to be used as a stand-alone solution in a large building.
Star
A star topology is designed with each node (file server, workstations, and peripherals) connected directly to a central network hub or concentrator
Data on a star network passes through the hub or concentrator before continuing to its destination. The hub or concentrator manages and controls all functions of the network. It also acts as a repeater for the data flow. This configuration is common with twisted pair cable; however, it can also be used with coaxial cable or fiber optic cable.
Advantages of a Star Topology
•Easy to install and wire.
•No disruptions to the network then connecting or removing devices.
•Easy to detect faults and to remove parts.
Disadvantages of a Star Topology
•Requires more cable length than a linear topology.
•If the hub or concentrator fails, nodes attached are disabled.
•More expensive than linear bus topologies because of the cost of the concentrators.
The protocols used with star configurations are usually Ethernet or LocalTalk. Token Ring - continued below ...
continued ...
uses a similar topology, called the star-wired ring.
Star-Wired Ring
A star-wired ring topology may appear (externally) to be the same as a star topology. Internally, the MAU (multistation access unit) of a star-wired ring contains wiring that allows information to pass from one device to another in a circle or ring (See fig. 3). The Token Ring protocol uses a star-wired ring topology.
Tree
A tree topology combines characteristics of linear bus and star topologies. It consists of groups of star-configured workstations connected to a linear bus backbone cable (See fig. 4). Tree topologies allow for the expansion of an existing network, and enable schools to configure a network to meet their needs.
Advantages of a Tree Topology
•Point-to-point wiring for individual segments.
•Supported by several hardware and software venders.
Disadvantages of a Tree Topology
•Overall length of each segment is limited by the type of cabling used.
•If the backbone line breaks, the entire segment goes down.
•More difficult to configure and wire than other topologies.
5-4-3 Rule
A consideration in setting up a tree topology using Ethernet protocol is the 5-4-3 rule. One aspect of the Ethernet protocol requires that a signal sent out on the network cable reach every part of the network within a specified length of time. Each concentrator or repeater that a signal goes through adds a small amount of time. This leads to the rule that between any two nodes on the network there can only be a maximum of 5 segments, connected through 4 repeaters/concentrators. In addition, only 3 of the segments may be populated (trunk) segments if they are made of coaxial cable. A populated segment is one which has one or more nodes attached to it . In Figure 4, the 5-4-3 rule is adhered to. The furthest two nodes on the network have 4 segments and 3 repeaters/concentrators between them.
This rule does not apply to other network protocols or Ethernet networks where all fiber optic cabling or a combination of a fiber backbone with UTP cabling is used. If there is a combination of fiber optic backbone and UTP cabling, the rule is simply translated to 7-6-5 rule.
Considerations When Choosing a Topology:
•Money. A linear bus network may be the least expensive way to install a network; you do not have to purchase concentrators.
•Length of cable needed. The linear bus network uses shorter lengths of cable.
•Future growth. With a star topology, expanding a network is easily done by adding another concentrator.
•Cable type. The most common cable in schools is unshielded twisted pair, which is most often used with star topologi
About the Author
5 years ago we gathered around and marveled at the little specs moving at our commands, doing not much – except moving off course, we called these things games. Today the hardware in computers and other devices has changed significantly; we went from having a “spacious” 1mb hard drive to 250 GB of space. The graphics have also taken a giant leap for our computers, no longer are we confined to little dots but our 256mb graphic cards allow us to explore a virtual world in 3d. The sound has also changed from 4bit to 32 and pretty soon 64bit; we went from beeps to actually words. Finally the speed of our beloved computers has also increased from mere kilobytes to gigabytes of rams. In such a short period of time we went from what we used to call “advanced” technology to today’s much superior devices. So if you guys are like I am, there is one question that strikes our mind, what’s next? Well I would love to say that we will be able to put on our virtual glasses that will allow us to explore the virtual world as if we were in it, but this is not likely, sorry guys; however, these sorts of glasses are being constructed but its - continued below ...
continued ...
unlikely they will come out any time soon. What we can expect to see is an improvement in our Text-to-speech and vise versa programs after the 64bit sound card is released allowing the computer to understand our voices much clearly, also we should soon be seeing more “dept” in our computer as you may know that the most our computers can run on 32bit resolution, it is expected that Microsoft is like to bring out a 64bit resolution with there next version of windows. Also the speed and graphics are to increase a lot more, already some games look as they are almost real, and soon they will look real. I am not certain exactly what marvel the computer hardware’s will hold in the future, but one thing is certain it will be something to forward too, and once again the next generation will be mocking the so called advanced technology we have today.
About the Author
continued ...
unlikely they will come out any time soon. What we can expect to see is an improvement in our Text-to-speech and vise versa programs after the 64bit sound card is released allowing the computer to understand our voices much clearly, also we should soon be seeing more “dept” in our computer as you may know that the most our computers can run on 32bit resolution, it is expected that Microsoft is like to bring out a 64bit resolution with there next version of windows. Also the speed and graphics are to increase a lot more, already some games look as they are almost real, and soon they will look real. I am not certain exactly what marvel the computer hardware’s will hold in the future, but one thing is certain it will be something to forward too, and once again the next generation will be mocking the so called advanced technology we have today.
About the Author
Los Angeles, CA --- With companies downsizing, corporations under strict scrutiny from the government and businesses finding it essential to be overly protective of proprietary information, times are not only challenging but keeping a close eye on company activities is essential. And corporations conducting internal investigations are on the rise. Privately held computer evidence recovery firm, Computer Forensics International (CFI) President, Mark McLaughlin is hard at work helping companies strengthen their cases to protect their best interests utilizing computer forensics. “A services company was accused of wrongful termination and breaching an executive employee contract. CFI examined his laptop revealing the disenchanted employee emailed sensitive company information to his friends who were competitors. The action against the company was withdrawn and the company initiated a lawsuit against the former executive,” explains McLaughlin.
This is just one of many cases McLaughlin has spearheaded utilizing computer forensics. One of the most common is finding out what employees are doing on valuable company time including surfing the Internet for pornography, sending - continued below ...
continued ...
sexually harassing emails to other employees, destroying or stealing valuable inside company information, or sharing that information with competitors or taking clients from the company to start up an outside independent business.
A prime example of this involves a case CFI has worked on with a nationwide services company. They suspected a key executive was resigning to work for a competitor and taking confidential files to assist them. Using a pretext they obtained his company laptop in advance of his departure. CFI's analysis revealed hidden email communications with his future employer and the creation of a confidential Zip archive of files. The company thwarted the transfer of data and received a stipulated judgment against the future employer and employee.
Mark McLaughlin has amassed nearly 25 years experience in computer forensic analysis, corporate security investigations, information systems management and law enforcement. He's a frequent lecturer and California State Bar qualified instructor for attorneys on computer forensics.
This is just one of many cases McLaughlin has spearheaded utilizing computer forensics. One of the most common is finding out what employees are doing on valuable company time including surfing the Internet for pornography, sending - continued below ...
continued ...
sexually harassing emails to other employees, destroying or stealing valuable inside company information, or sharing that information with competitors or taking clients from the company to start up an outside independent business.
A prime example of this involves a case CFI has worked on with a nationwide services company. They suspected a key executive was resigning to work for a competitor and taking confidential files to assist them. Using a pretext they obtained his company laptop in advance of his departure. CFI's analysis revealed hidden email communications with his future employer and the creation of a confidential Zip archive of files. The company thwarted the transfer of data and received a stipulated judgment against the future employer and employee.
Mark McLaughlin has amassed nearly 25 years experience in computer forensic analysis, corporate security investigations, information systems management and law enforcement. He's a frequent lecturer and California State Bar qualified instructor for attorneys on computer forensics.
continued ...
clicks of the button using the thumb, or a more simple one which is cordless and has a finger-operated trackball that works where you need it.
Ergonomic Armrests are also very important for prevention of such ailments as neck pain, back pain, poor circulation and chronic neck fatigue, including the ones discussed for the ergonomic mouse. Your arm also needs to be very comfortable and positioned properly to ensure that you will not tire while doing your webmaster duties. Ergonomic armrests have been proven scientifically that such problems as muscle tension in the neck and shoulders can be reduced considerably. With the quality arm support that you receive with the ergonomic armrests you will receive a comfortable arm, shoulder and neck support without any restriction in your motion.
With all Ergonomic computer products you as a webmaster will be able to get your work done faster and more efficiently because you will be more comfortable and will be reducing the stress in your neck and shoulders.
You can also find several other ergonomic computer products such as ergonomic chairs, ergonomic keyboards, keypad tray, mouse support tray, wrists rests, and forearm rests. Any position that you put your body in can cause damage if you are not comfortable and start feeling pain. The best way to ensure a healthy body for all webmasters is to purchase ergonomic computer products right from the start. Sit upright in your chair with proper posture, position your monitor so you do not have eye strain or have the monitor at the wrong angle, use ergonomic computer products to prevent pain in your hands, arms, wrists, shoulders, and back.
clicks of the button using the thumb, or a more simple one which is cordless and has a finger-operated trackball that works where you need it.
Ergonomic Armrests are also very important for prevention of such ailments as neck pain, back pain, poor circulation and chronic neck fatigue, including the ones discussed for the ergonomic mouse. Your arm also needs to be very comfortable and positioned properly to ensure that you will not tire while doing your webmaster duties. Ergonomic armrests have been proven scientifically that such problems as muscle tension in the neck and shoulders can be reduced considerably. With the quality arm support that you receive with the ergonomic armrests you will receive a comfortable arm, shoulder and neck support without any restriction in your motion.
With all Ergonomic computer products you as a webmaster will be able to get your work done faster and more efficiently because you will be more comfortable and will be reducing the stress in your neck and shoulders.
You can also find several other ergonomic computer products such as ergonomic chairs, ergonomic keyboards, keypad tray, mouse support tray, wrists rests, and forearm rests. Any position that you put your body in can cause damage if you are not comfortable and start feeling pain. The best way to ensure a healthy body for all webmasters is to purchase ergonomic computer products right from the start. Sit upright in your chair with proper posture, position your monitor so you do not have eye strain or have the monitor at the wrong angle, use ergonomic computer products to prevent pain in your hands, arms, wrists, shoulders, and back.
Webmasters usually sit at their computers much longer in a day than most other office workers, sometimes up to 10 and 12 hours. This can bring about the potential for physical discomforts that are attributed to prolonged use and the repetitive tasks that they perform on computers every day. If left unchanged, these discomforts can result in bodily injuries. If your income depends on you being online or at your computer, these injuries can cause you time off of your computer, very high medical bills, and loss of income. The use of ergonomic computer products will not only improve your health by making you more comfortable, but will also aid you in becoming more productive and have less physical stress and even make fewer errors.
You may now be wondering what Ergonomic computer products are and how they can help you be more comfortable at your computer. Well, to understand what these products are you must first know what Ergonomic is. Ergonomics is the study of work. This study aims to achieve the development of equipments, tools, and devices that fit the work of the webmaster. With this study, the proper tools and equipment can be developed to ensure that webmasters do not develop any serious health problems while performing their tasks at their computers.
One item that you use more than any other while at your computer is your mouse. There are plenty of fancy expensive ones out there, but do they aid in the prevention of carpal tunnel syndrome, repetitive stress injuries, and tendonitis? An Ergonomic Mouse will. These are designed especially for webmasters to give them a more comfortable way of maneuvering and surfing the internet while giving them the support they need. You can find a very uniquely designed Ergonomic mouse that will be perfect for your needs while ensuring a healthy position for you hand and wrist. You may need one in which you rest the side of your hand at the base of the mouse and the thumb on the switch on the top of the stick for easy right and left
You may now be wondering what Ergonomic computer products are and how they can help you be more comfortable at your computer. Well, to understand what these products are you must first know what Ergonomic is. Ergonomics is the study of work. This study aims to achieve the development of equipments, tools, and devices that fit the work of the webmaster. With this study, the proper tools and equipment can be developed to ensure that webmasters do not develop any serious health problems while performing their tasks at their computers.
One item that you use more than any other while at your computer is your mouse. There are plenty of fancy expensive ones out there, but do they aid in the prevention of carpal tunnel syndrome, repetitive stress injuries, and tendonitis? An Ergonomic Mouse will. These are designed especially for webmasters to give them a more comfortable way of maneuvering and surfing the internet while giving them the support they need. You can find a very uniquely designed Ergonomic mouse that will be perfect for your needs while ensuring a healthy position for you hand and wrist. You may need one in which you rest the side of your hand at the base of the mouse and the thumb on the switch on the top of the stick for easy right and left
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Information becomes power as soon as you act. Our monster ebook library is almost ready. We are working hard to provide the best quality ebooks at the lowest prices. Make sure you join our mailing list to grab amazing discounts on popular titles ...
To support our articles, we offer search access to an information product database that contains over 9,000 vendors. This database is a little bit special, because each vendor has agreed to provide a rock solid
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