Internet websites now provide personal, educational, political and economic resources to virtually any point on the planet. With advancements in browser-based software for the Internet, many private organizations have implemented intra nets. An intranet is a private network utilizing Internet-type tools, but available only within that organization.
For large organizations, an intranet provides easy access to corporate information for designated employees. While an intranet is used to disseminate confidential information within a corporation, an extra net is commonly used by companies to share data in a secure fashion with their business partners. Internet-type tools are used by content providers to update the extranet.
Encryption and user authentication means are provided to protect the information, and to ensure that designated people with the proper access privileges are allowed to view it. Ethernet is the most popular physical layer LAN technology in use today. It defines the number of conductors that are required for a connection, the performance thresholds that can be expected, and provides the framework for data transmission. A standard Ethernet network can transmit data at a rate up to 10 Megabits per second 10 Mbps.
Ethernet is popular because it strikes a good balance between speed, cost and ease of installation. These benefits, combined with wide acceptance in the computer marketplace and the ability to support virtually all popular network protocols, make Ethernet an ideal networking technology for most computer users today.
This standard defines rules for configuring an Ethernet network and also specifies how the elements in an Ethernet network interact with one another. By adhering to the IEEE standard, network equipment and network protocols can communicate efficiently. This standard raises the Ethernet speed limit from 10 Mbps to Mbps with only minimal changes to the existing cable structure. Fast Ethernet provides faster throughput for video, multimedia, graphics, Internet surfing and stronger error detection and correction. Network managers who want to incorporate Fast Ethernet into an existing configuration are required to make many decisions.
The number of users in each site on the network that need the higher throughput must be determined; which segments of the backbone need to be reconfigured specifically for BASE-T; plus what hardware is necessary in order to connect the BASE-T segments with existing 10BASE-T segments. Gigabit Ethernet is a future technology that promises a migration path beyond Fast Ethernet so the next generation of networks will support even higher data transfer speeds. Gigabit Ethernet was developed to meet the need for faster communication networks with applications such as multimedia and Voice over IP VoIP.
It is defined in the IEEE Existing Ethernet LANs with 10 and Mbps cards can feed into a Gigabit Ethernet backbone to interconnect high performance switches, routers and servers. From the data link layer of the OSI model upward, the look and implementation of Gigabit Ethernet is identical to that of Ethernet. The most important differences between Gigabit Ethernet and Fast Ethernet include the additional support of full duplex operation in the MAC layer and the data rates. IEEE Unlike other Ethernet systems, 10 Gigabit Ethernet is based entirely on the use of optical fiber connections. This developing standard is moving away from a LAN design that broadcasts to all nodes, toward a system which includes some elements of wide area routing.
As it is still very new, which of the standards will gain commercial acceptance has yet to be determined.
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ATM is a cell-based fast-packet communication technique that can support data-transfer rates from sub-T1 speeds to 10 Gbps. ATM achieves its high speeds in part by transmitting data in fixed-size cells and dispensing with error-correction protocols. It relies on the inherent integrity of digital lines to ensure data integrity. ATM can be integrated into an existing network as needed without having to update the entire network.
Its fixed-length cell-relay operation is the signaling technology of the future and offers more predictable performance than variable length frames. Networks are extremely versatile and an ATM network can connect points in a building, or across the country, and still be treated as a single network. PoE is a solution in which an electrical current is run to networking hardware over the Ethernet Category 5 cable or higher.
This solution does not require an extra AC power cord at the product location. This minimizes the amount of cable needed as well as eliminates the difficulties and cost of installing extra outlets. Token Ring is another form of network configuration.
It differs from Ethernet in that all messages are transferred in one direction along the ring at all times. When the token arrives at a particular computer or device , the recipient is allowed to transmit data onto the network. Since only one device may be transmitting at any given time, no data collisions occur. Access to the network is guaranteed, and time-sensitive applications can be supported. However, these benefits come at a price.
Component costs are usually higher, and the networks themselves are considered to be more complex and difficult to implement. Various PC vendors have been proponents of Token Ring networks. After a physical connection has been established, network protocols define the standards that allow computers to communicate. A protocol establishes the rules and encoding specifications for sending data.
Types of Networks
This defines how computers identify one another on a network, the form that the data should take in transit, and how this information is processed once it reaches its final destination. Although each network protocol is different, they all share the same physical cabling. This common method of accessing the physical network allows multiple protocols to peacefully coexist over the network media, and allows the builder of a network to use common hardware for a variety of protocols. The Open System Interconnection OSI model specifies how dissimilar computing devices such as Network Interface Cards NICs , bridges and routers exchange data over a network by offering a networking framework for implementing protocols in seven layers.
Beginning at the application layer, control is passed from one layer to the next. The following describes the seven layers as defined by the OSI model, shown in the order they occur whenever a user transmits information. This layer supports the application and end-user processes. Within this layer, user privacy is considered and communication partners, service and constraints are all identified.
File transfers, email, Telnet and FTP applications are all provided within this layer. Within this layer, information is translated back and forth between application and network formats. This translation transforms the information into data the application layer and network recognize regardless of encryption and formatting. Within this layer, connections between applications are made, managed and terminated as needed to allow for data exchanges between applications at each end of a dialogue.
Network Protocol - Types of Network Protocols
Complete data transfer is ensured as information is transferred transparently between systems in this layer. The transport layer also assures appropriate flow control and end-to-end error recovery. Using switching and routing technologies, this layer is responsible for creating virtual circuits to transmit information from node to node. Other functions include routing, forwarding, addressing, internet working, error and congestion control, and packet sequencing. Information in data packets are encoded and decoded into bits within this layer.
Errors from the physical layer flow control and frame synchronization are corrected here utilizing transmission protocol knowledge and management.
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This layer consists of two sub layers: the Media Access Control MAC layer, which controls the way networked computers gain access to data and transmit it, and the Logical Link Control LLC layer, which controls frame synchronization, flow control and error checking. This layer enables hardware to send and receive data over a carrier such as cabling, a card or other physical means. It conveys the bitstream through the network at the electrical and mechanical level.
This order is then reversed as information is received, so that the physical layer is the first and application layer is the final layer that information passes through. In order to understand standard Ethernet code, one must understand what each digit means. Following is a guide:. An important part of designing and installing an Ethernet is selecting the appropriate Ethernet medium. Thickwire was one of the first cabling systems used in Ethernet, but it was expensive and difficult to use. This evolved to thin coax, which is easier to work with and less expensive.
It is important to note that each type of Ethernet, Fast Ethernet, Gigabit Ethernet, 10 Gigabit Ethernet, has its own preferred media types. This is similar to telephone cable and comes in a variety of grades, with each higher grade offering better performance. Level 5 cable is the highest, most expensive grade, offering support for transmission rates of up to Mbps. Level 4 and level 3 cable are less expensive, but cannot support the same data throughput speeds; level 4 cable can support speeds of up to 20 Mbps; level 3 up to 16 Mbps.
Fiber-optic cable is more expensive, but it is invaluable in situations where electronic emissions and environmental hazards are a concern.
Fiber-optic cable is often used in inter-building applications to insulate networking equipment from electrical damage caused by lightning. Because it does not conduct electricity, fiber-optic cable can also be useful in areas where heavy electromagnetic interference is present, such as on a factory floor.
The Ethernet standard allows for fiber-optic cable segments up to two kilometers long, making fiber-optic Ethernet perfect for connecting nodes and buildings that are otherwise not reachable with copper media. Network topology is the geometric arrangement of nodes and cable links in a LAN. Two general configurations are used, bus and star. These two topologies define how nodes are connected to one another in a communication network. A node is an active device connected to the network, such as a computer or a printer.
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A node can also be a piece of networking equipment such as a hub, switch or a router. A bus topology consists of nodes linked together in a series with each node connected to a long cable or bus. Many nodes can tap into the bus and begin communication with all other nodes on that cable segment. A break anywhere in the cable will usually cause the entire segment to be inoperable until the break is repaired.
Gigabit Ethernet also requires special adapters, hubs, switches, and cables. Gigabit Ethernet hardware was initially very expensive, thus limiting the use of gigabit Ethernet to high-end network interconnections. More recently, the prices of cables, adapters and especially switches has fallen dramatically, making gigabit the recommended choice for all new cable, adapter, and switch installations. Neither Fast Ethernet nor gigabit Ethernet support the use of thin or thick coaxial cable originally used with traditional Ethernet, although you can interconnect coaxial cable—based and UTP-based Ethernet networks by using media converters or specially designed hubs and switches.
Lower grade Cat 6 cable can be used if the distance is limited to 55 meters feet. Just as with gigabit Ethernet, all four pairs in the cable are used. Once the prices of adapters and switches falls to be close to those for gigabit Ethernet, we will see 10 gigabit Ethernet start to become popular for PC-based networks. To prepare for a future upgrade to 10 gigabit Ethernet, consider installing only Category 6a or better cabling in any new installations.
The most common forms of wireless networking are built around various versions of the IEEE Wi-Fi certification comes from the Wi-Fi Alliance, a nonprofit international trade organization that tests To carry the Wi-Fi logo, an This certification arose from the fact that certain ambiguities in the By purchasing only devices bearing the Wi-Fi logo, you ensure that they will work together and not fall into loopholes in the standards.
Note: The Bluetooth standard for short-range wireless networking, covered later in this chapter, is designed to complement, rather than rival, IEEE The widespread popularity of IEEE This was especially common in early Although these proprietary solutions can work, beware that most, if not all, of these vendor-specific solutions are not interoperable with devices from other vendors. When different vendor-specific devices are mixed on a single network, they use the slower common standard to communicate with each other. When the first A group of companies formed an alliance designed to ensure that their products would work together, thus eliminating any ambiguities or loopholes in the standards.
However, because the Wi-Fi Alliance now certifies other types of Currently, the Alliance has certified products that meet the final versions of the The Wi-Fi Alliance currently uses a color-coded certification label to indicate the standard s supported by a particular device. The image below shows the most common versions of the label, along with the official IEEE standard s that the label corresponds to: IEEE Wireless networks running Although the increasing use of these products is a potential source of interference, the short range of wireless networks indoor ranges up to approximately feet and outdoor ranges up to about feet, varying by product minimizes the practical risks.
Many devices use a spread-spectrum method of connecting with other products to minimize potential interference. Although Most As distances change and signal strength increases or decreases, The overhead required to track and change signaling methods, along with the additional overhead required when security features are enabled, helps explain why wireless hardware throughput is consistently lower than the rated speed. The figure below is a simplified diagram showing how speed is reduced with distance. Figures given are for best-case situations; building design and antenna positioning can also reduce speed and signal strength, even at relatively short distances.
Although real-world For example, in a typical office floor layout, the real-world throughput always slower than the rated speed due to security and signaling overhead of a typical At a distance of about 50 feet, Given the difference in throughput especially at long distances , and if we take the existence of In a single word: frequency. By using the 5 GHz frequency instead of the 2. The current solution for maximum flexibility is to use dual-band hardware. Dual-band hardware can work with either The final In some cases, problems with early-release Note: Although For example, you can configure a 2.
The latter offers the highest performance for Wireless-N devices. Similarly you can configure Wireless-G access points to allow Restricting or disabling the mixed mode operation offers higher performance at the expense of restricting the types of devices that can connect. The latest wireless network standard, MIMO uses multiple radios and antennas to transmit multiple data streams also known as spatial streams between stations.
Unlike earlier Thus, depending on the specific implementation of Wireless-N devices can contain radios in a number of different configurations supported by the standard. The radios are defined or categorized by the number of transmit antennas, receive antennas, and data streams also called spatial streams they can support.
A common notation has been devised to describe these configurations, which is written as a x b:c, where a is the maximum number of transmit antennas, b is the maximum number of receive antennas, and c is the maximum number of simultaneous data streams that can be used. Those using more antennas than data streams allow for increased signal diversity and range. That depends mainly on how many data streams are supported, as well as whether a couple of other optional features are enabled or not. The base configuration uses 20 MHz wide channels with an ns guard interval between transmitted signals.
By using channel bonding to increase the channel width to 40 MHz, more than double the bandwidth can be achieved in theory. In addition, the wider channel takes up more of the band, causing more interference with other wireless networks in range. Another optional feature is using a shorter guard interval GI , which is the amount of time in nanoseconds the system waits between transmitting OFDM orthagonal frequency division multiplexing symbols in a data stream. Just as with channel bonding 40 MHz channel width , this can cause problems if there is excessive interference or low signal strength, resulting in decreased overall throughput due to signal errors and retries.
Using the shorter ns guard interval would increase this to up to As with other members of the The Wi-Fi Alliance first began certifying products that support The In some cases, driver or firmware updates might be necessary to insure ensure full compliance. As with previous Wi-Fi certifications, the Wi-Fi Bluetooth is a low-speed, low-power standard originally designed to interconnect laptop computers, PDAs, cell phones, and pagers for data synchronization and user authentication in public areas such as airports, hotels, rental car pickups, and sporting events.
Bluetooth is also used for a variety of wireless devices on PCs, including printer adapters, keyboards, mice, headphones, DV camcorders, data projectors, and many others. A list of Bluetooth products and announcements is available at the official Bluetooth wireless information website. Bluetooth devices also use the same 2. However, in an attempt to avoid interference with Wi-Fi, Bluetooth uses a signaling method called frequency hopping spread spectrum FHSS , which switches the exact frequency used during a Bluetooth session times per second over the 79 channels Bluetooth uses.
Unlike Wi-Fi, which is designed to allow a device to be part of a network at all times, Bluetooth is designed for ad hoc temporary networks known as piconets in which two devices connect only long enough to transfer data and then break the connection. The current version of Bluetooth is 4.
Version 3. Despite the frequency-hopping nature of Bluetooth, studies have shown that Bluetooth Interference reduces throughput and in some circumstances can cause data loss. Bluetooth version 1. However, close-range less than 1 meter interference can still take place. IEEE has developed It can use various time-sharing or time-division methods to enable coexistence.
Bluetooth version 2. Companies that build both Bluetooth and A few years ago, the second-most important choice you had to make when you created a network was which network protocol to use because the network protocol affects which types of computers your network can connect.derivid.route1.com/coleccin-integral-de-friedrich-schiller.php
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Although data-link protocols such as Ethernet require specific types of hardware, network protocols are software and can be installed to or removed from any computer on the network at any time, as necessary. All the computers on any given network must use the same network protocol or protocol suite to communicate with each other. Although the same protocol is used in both cases, the settings vary a great deal.
You also might need to adjust your browser settings to indicate which connection type you are using. Correct settings for LAN access to the Internet and dial-up networking modem settings are almost always completely different. After the setup is working, view the properties and record them for future troubleshooting use.
It was the default protocol in Windows NT 3. If you are working at home or in a small office, you have an alternative to hole-drilling, pulling specialized network cabling, or setting up a wireless network. Other than using Ethernet wired or wireless , the most popular form of home networking involves adapting existing telephone wiring to networking by running network signals at frequencies above those used by the telephone system. This alliance has most of the major computer hardware and telecommunications vendors among its founding and active membership.
HomePNA 1. HomePNA 2. Although some vendors produced HomePNA 1. Both of these products use a bus topology that runs over existing telephone wiring and are designed for PC networking only. With the development of HomePNA 3. HomePNA 3. In addition to telephone wiring, HomePNA 3. As shown in the figure below, HomePNA 3. Because HomePNA 3. Home networking via power lines has been under development for several years, but electrical interference, inconsistent voltage, and security issues made the creation of a workable standard difficult until mid The HomePlug Powerline Alliance www.