A backbone is a larger transmission line that carries data gathered from smaller lines that interconnect with it.

1) At the local level, a backbone is a line or set of lines that local area networks connect to for a wide area network connection or within a local area network to span distances efficiently (for example, between buildings).
2) On the Internet or other wide area network, a backbone is a set of paths that local or regional networks connect to for long-distance interconnection. The connection points are known as network nodes or telecommunication data switching exchanges (DSEs).

Bluetooth is a computing and telecommunications industry specification that describes how mobile phones, computers, and personal digital assistants (PDAs) can easily interconnect with each other and with home and business phones and computers using a short-range wireless connection. Using this technology, users of cellular phones, pagers, and personal digital assistants such as the PalmPilot will be able to buy a three-in-one phone that can double as a portable phone at home or in the office, get quickly synchronized with information in a desktop or notebook computer, initiate the sending or receiving of a fax, initiate a print-out, and, in general, have all mobile and fixed computer devices be totally coordinated.

Bluetooth requires that a low-cost transceiver chip be included in each device. The tranceiver transmits and receives in a previously unused frequency band of 2.45 GHz that is available globally (with some variation of bandwidth in different countries). In addition to data, up to three voice channels are available. Each device has a unique 48-bit address from the IEEE 802 standard. Connections can be point-to-point or multipoint. The maximum range is 10 meters. Data can be exchanged at a rate of 1 megabit per second (up to 2 Mbps in the second generation of the technology). A frequency hop scheme allows devices to communicate even in areas with a great deal of electromagnetic interference. Built-in encryption and verification is provided.

In data communications, bits per second (abbreviated bps) is a common measure of data speed for computer modem and transmission carriers. As the term implies, the speed in bps is equal to the number of bits transmitted or received each second. The duration d of a data bit, in seconds, is inversely proportional to the digital transmission speed s in bps:

d = 1/s

Larger units are sometimes used to denote high data speeds. One kilobit per second (abbreviated Kbps in the U.S.; kbps elsewhere) is equal to 1,000 bps. One megabit per second (Mbps) is equal to 1,000,000 bps or 1,000 kbps.

Computer modems for twisted pair telephone lines usually operate at speeds between 14.4 and 57.6 kbps. The most common speeds are 28.8 and 33.6 kbps. So-called "cable modems," designed for use with TV cable networks, can operate at more than 100 kbps. Fiberoptic modems are the fastest of all; they can send and receive data at many Mbps.
The bandwidth of a signal depends on the speed in bps. With some exceptions, the higher the bps number, the greater is the nominal signal bandwidth. (Speed and bandwidth are, however, not the same thing.) Bandwidth is measured in standard frequency units of kHz or MHz.

Data speed is sometimes specified in terms of 'baud', which is a measure of the number of times a digital signal changes state in one second. Baud, sometimes called the "baud rate," is almost always a lower figure than bps for a given digital signal. The terms are often used interchangeably, even though they do not refer to the same thing. If you hear that a computer modem can function at "33,600 baud" or "33.6 kilobaud," you can be reasonably sure that the term is being misused, and the figures actually indicate bps.

In telecommunication networks, a bridge is a product that connects a local area network (LAN) to another local area network that uses the same protocol (for example, Ethernet or token ring). You can envision a bridge as being a device that decides whether a message from you to someone else is going to the local area network in your building or to someone on the local area network in the building across the street. A bridge examines each message on a LAN, "passing" those known to be within the same LAN, and forwarding those known to be on the other interconnected LAN (or LANs).

In bridging networks, computer or node addresses have no specific relationship to location. For this reason, messages are sent out to every address on the network and accepted only by the intended destination node. Bridges learn which addresses are on which network and develop a learning table so that subsequent messages can be forwarded to the right network.

Bridging networks are generally always interconnected local area networks since broadcasting every message to all possible destinations would flood a larger network with unnecessary traffic. For this reason, router networks such as the Internet use a scheme that assigns addresses to nodes so that a message or packet can be forwarded only in one general direction rather than forwarded in all directions.

A bridge works at the data-link (physical network) level of a network, copying a data frame from one network to the next network along the communications path.

A bridge is sometimes combined with a router in a product called a 'brouter'.

In general, broadband refers to telecommunication in which a wide band of frequencies is available to transmit information. Because a wide band of frequencies is available, information can be multiplexed and sent on many different frequencies or channels within the band concurrently, allowing more information to be transmitted in a given amount of time (much as more lanes on a highway allow more cars to travel on it at the same time).

Related terms are wideband (a synonym), baseband (a one-channel band), and narrowband (sometimes meaning just wide enough to carry voice, or simply "not broadband," and sometimes meaning specifically between 50 cps and 64 Kpbs).

Carrier Sense Multiple Access/Collision Detect (CSMA/CD) is the protocol for carrier transmission access in ethernet networks. On Ethernet, any device can try to send a frame at any time. Each device senses whether the line is idle and therefore available to be used. If it is, the device begins to transmit its first frame. If another device has tried to send at the same time, a collision is said to occur and the frames are discarded. Each device then waits a random amount of time and retries until successful in getting its transmission sent.

CSMA/CD is specified in the IEEE 802.3 standard.

ANSI/EIA (American National Standards Institute/Electronic Industries Association) Standard 568 is one of several standards that specify "categories" (the singular is commonly referred to as "CAT") of twisted pair cabling systems (wires, junctions, and connectors) in terms of the data rates that they can sustain. The specifications describe the cable material as well as the types of connectors and junction blocks to be used in order to conform to a category.

While longer connections for Gigabit Ethernet use optical fiber, the goal is to leverage the CAT 5 twisted-pair wiring most organizations already have in place for connections out to the desktop. (Four pairs of twisted pair are used.)

The two most popular specifications are CAT 3 and CAT 5. While the two cables may look identical, CAT 3 is tested to a lower set of specifications and can cause transmission errors if pushed to faster speeds. CAT 3 cabling is near-end crosstalk-certified for only a 16 MHz signal, while CAT 5 cable must pass a 100 MHz test.

The CAT 6 specification was not yet formally approved by the EIA as of March, 2001, although products are being offered that conform to a proposed specification. A CAT 7 specification is reportedly being considered.

Please, see also Why 'twisted pair' cable? and 'What is the difference between UTP and STP cable'?

A client is the requesting program or user in a client/server relationship. For example, the user of a Web browser is effectively making client requests for pages from servers all over the Web. The browser itself is a client in its relationship with the computer that is getting and returning the requested HTML file. The computer handling the request and sending back the HTML file is a server.

Client/server describes the relationship between two computer programs in which one program, the client, makes a service request from another program, the server, which fulfills the request. Although the client/server idea can be used by programs within a single computer, it is a more important idea in a network. In a network, the client/server model provides a convenient way to interconnect programs that are distributed efficiently across different locations. Computer transactions using the client/server model are very common. For example, to check your bank account from your computer, a client program in your computer forwards your request to a server program at the bank. That program may in turn forward the request to its own client program that sends a request to a database server at another bank computer to retrieve your account balance. The balance is returned back to the bank data client, which in turn serves it back to the client in your personal computer, which displays the information for you.

The client/server model has become one of the central ideas of network computing. Most business applications being written today use the client/server model. So does the Internet's main program, TCP/IP. In marketing, the term has been used to distinguish distributed computing by smaller dispersed computers from the "monolithic" centralized computing of mainframe computers. But this distinction has largely disappeared as mainframes and their applications have also turned to the client/server model and become part of network computing.

In the usual client/server model, one server, sometimes called a daemon, is activated and awaits client requests. Typically, multiple client programs share the services of a common server program. Both client programs and server programs are often part of a larger program or application. Relative to the Internet, your Web browser is a client program that requests services (the sending of Web pages or files) from a Web server (which technically is called a Hypertext Transport Protocol or HTTP server) in another computer somewhere on the Internet. Similarly, your computer with TCP/IP installed allows you to make client requests for files from File Transfer Protocol (FTP) servers in other computers on the Internet.
Other program relationship models included master/slave, with one program being in charge of all other programs, and peer-to-peer, with either of two programs able to initiate a transaction.

A BNC (Bayonet Neil-Concelman, or sometimes British Naval Connector) connector is used to connect a computer to a coaxial in a 10Base-2 Ethernet network. 10BASE-2 is a 10 MHz baseband network on a cable extending up to 185 meters - the 2 is a rounding up to 200 meters - without a repeater cable. 10BASE-2 Ethernets are also known as "Thinnet", "thin Ethernet", or "cheapernets". The wiring in this type of Ethernet is thin, 50 ohm, baseband coaxial cable. The BNC connector in particular is generally easier to install and less expensive than other coaxial connectors.

A BNC male connector has a pin that connects to the primary conducting wire and then is locked in place with an outer ring that turns into locked position.

Different sources offer different meanings for the letters BNC. However, our most knowledgable source indicates that the B stands for a bayonet-type connection (as in the way a bayonet attaches to a rifle) and the NC for the inventors of the connector, Neil and Concelman.

Coaxial cable is the kind of copper cable used by cable TV companies between the community antenna and user homes and businesses. Coaxial cable is sometimes used by telephone companies from their central office to the telephone poles near users. It is also widely installed for use in business and corporation Ethernet and other types of local area network.

Coaxial cable is called "coaxial" because it includes one physical channel that carries the signal surrounded (after a layer of insulation) by another concentric physical channel, both running along the same axis. The outer channel serves as a ground. Many of these cables or pairs of coaxial tubes can be placed in a single outer sheathing and, with repeaters, can carry information for a great distance. Coaxial cable was invented in 1929 and first used commercially in 1941. AT&T established its first cross-continental coaxial transmission system in 1940. Depending on the carrier technology used and other factors, twisted pair copper wire and optical fiber are alternatives to coaxial cable.

In an Ethernet network, a collision is the result of two devices on the same Ethernet network attempting to transmit data at exactly the same time. The network detects the "collision" of the two transmitted packets and discards them both. Collisions are a natural occurrence on Ethernets. Ethernet uses Carrier Sense Multiple Access/ Collision Detect (CSMA/CD) as its method of allowing devices to "take turns" using the signal carrier line. When a device wants to transmit, it checks the signal level of the line to determine whether someone else is already using it. If it is already in use, the device waits and retries, perhaps in a few seconds. If it isn't in use, the device transmits. However, two devices can transmit at the same time in which case a collision occurs and both devices detect it. Each device then waits a random amount of time and retries until successful in getting the transmission sent.

A crossover cable is a cable that is used to interconnect two computers by "crossing over" (reversing) their respective PIN contacts. Either an RS-232C or an registered jack connection is possible. A crossover cable is sometimes known as a null modem.

Dynamic Host Configuration Protocol (DHCP) is a communications protocol that lets network administrators manage centrally and automate the assignment of Internet Protocol (IP) addresses in an organization's network. Using the Internet Protocol, each machine that can connect to the Internet needs a unique IP address. When an organization sets up its computer users with a connection to the Internet, an IP address must be assigned to each machine. Without DHCP, the IP address must be entered manually at each computer and, if computers move to another location in another part of the network, a new IP address must be entered. DHCP lets a network administrator supervise and distribute IP addresses from a central point and automatically sends a new IP address when a computer is plugged into a different place in the network.

DHCP uses the concept of a "lease" or amount of time that a given IP address will be valid for a computer. The lease time can vary depending on how long a user is likely to require the Internet connection at a particular location. It's especially useful in education and other environments where users change frequently. Using very short leases, DHCP can dynamically reconfigure networks in which there are more computers than there are available IP addresses.

DHCP supports static addresses for computers containing Web servers that need a permanent IP address.

DHCP is an alternative to another network IP management protocol, Bootstrap Protocol (BOOTP). DHCP is a more advanced protocol, but both configuration management protocols are commonly used. Some organizations use both protocols, but understanding how and when to use them in the same organization is important. Some operating systems, including Windows NT/2000, come with DHCP servers. A DHCP or BOOTP client is a program that is located in (and perhaps downloaded to) each computer so that it can be configured.

Please, see also What means 'IP'?

DSL (Digital Subscriber Line) is a technology for bringing high-bandwidth information to homes and small businesses over ordinary copper telephone lines. xDSL refers to different variations of DSL, such as ADSL, HDSL, and RADSL.

Assuming your home or small business is close enough to a telephone company central office that offers DSL service, you may be able to receive data at rates up to 6.1 megabits (millions of bits) per second (of a theoretical 8.448 megabits per second), enabling continuous transmission of motion video, audio, and even 3-D effects.

More typically, individual connections will provide from 1.544 Mbps to 512 Kbps downstream and about 128 Kbps upstream. A DSL line can carry both data and voice signals and the data part of the line is continuously connected. DSL installations began in 1998 and will continue at a greatly increased pace through the next decade in a number of communities in the U.S. and elsewhere. Compaq, Intel, and Microsoft working with telephone companies have developed a standard and easier-to-install form of ADSL called G.lite that is accelerating deployment. DSL is expected to replace ISDN in many areas and to compete with the cable modem in bringing multimedia and 3-D to homes and small businesses.

Traditional phone service (sometimes called POTS for "plain old telephone service") connects your home or small business to a telephone company office over copper wires that are wound around each other and called twisted pair. Traditional phone service was created to let you exchange voice information with other phone users and the type of signal used for this kind of transmission is called an analog signal. An input device such as a phone set takes an acoustic signal (which is a natural analog signal) and converts it into an electrical equivalent in terms of volume (signal amplitude) and pitch (frequency of wave change). Since the telephone company's signalling is already set up for this analog wave transmission, it's easier for it to use that as the way to get information back and forth between your telephone and the telephone company. That's why your computer has to have a model- so that it can demodulate the analog signal and turn its values into the string of 0 and 1 values that is called digital information.

Because analog transmission only uses a small portion of the available amount of information that could be transmitted over copper wires, the maximum amount of data that you can receive using ordinary modems is about 56 Kbps (thousands of bits per second). (With ISND, which one might think of as a limited precursor to DSL, you can receive up to 128 Kbps.) The ability of your computer to receive information is constrained by the fact that the telephone company filters information that arrives as digital data, puts it into analog form for your telephone line, and requires your modem to change it back into digital. In other words, the analog transmission between your home or business and the phone company is a bandwidth bottleneck.

Digital Subscriber Line is a technology that assumes digital data does not require change into analog form and back. Digital data is transmitted to your computer directly as digital data and this allows the phone company to use a much wider bandwidth for transmitting it to you. Meanwhile, if you choose, the signal can be separated so that some of the bandwidth is used to transmit an analog signal so that you can use your telephone and computer on the same line and at the same time.

ADSL (Asymmetric Digital Subscriber Line) is a technology for transmitting digital information at a high bandwidth on existing phone lines to homes and businesses. Unlike regular dialup phone service, ADSL provides continously-available, "always on" connection. ADSL is asymmetric in that it uses most of the channel to transmit downstream to the user and only a small part to receive information from the user. ADSL simultaneously accommodates analog (voice) information on the same line. ADSL is generally offered at downstream data rates from 512 Kbps to about 6 Mbps. A form of ADSL, known as Universal ADSL or G.lite, has been approved as a standard by the ITU-TS.

ADSL was specifically designed to exploit the one-way nature of most multimedia communication in which large amounts of information flow toward the user and only a small amount of interactive control information is returned. Several experiments with ADSL to real users began in 1996. In 1998, wide-scale installations began in several parts of the U.S. In 2000 and beyond, ADSL and other forms of DSL are expected to become generally available in urban areas. With ADSL (and other forms of DSL), telephone companies are competing with cable companies and their cable modem services.

Many DSL providers choose to use Modems instead of Routers as a cheaper means to get DSL access. Prior to deciding which device best suits your needs, you must analyze the difference between these two products.

A DSL modem is a card that needs to be physically installed into your computer via PCI port. Some modems are external units that can be plugged into a USB port (Universal Serial Bus). DSL modems require proprietary software drivers for your operating system as well as taking up different IRQ addresses, DMA addresses, IO addresses and com ports. Since modems use such a vast variety of resources, they could cause conflicts with other devices already installed into your computer. Devices such as controller cards, graphics cards and SCSI cards could conflict with your modem if they share the same range of addresses. Another drawback to modems is the requirement to install proprietary software drivers into your OS (Operating System). Anytime a driver is installed into an OS, there is a risk of software incompatibility between the OS and the installed drivers. It is possible that the drivers themselves could cause havoc with your operating system and not be compatible at all.

Another drawback to using a modem is the limitation of hooking up multiple computers or other hardware devices. A modem usually contains only one Ethernet port, allowing only one computer to connect to the internet with one Dynamically issued IP address by the ISP. Everytime a connection is made to the ISP, the IP address that is assigned to a DSL modem could possible change. Hence, this brings us to the limitation of running servers that require static routable IP addresses such as http (web), smtp (mail), pop3 (mail), ftp (File Transfer Protocol), snmp (Simple Network Management Protocol), telnet, DNS (Domain Name Service), Quake, Unreal, etc. To break this modem barrier, many companies as well as individuals look toward using routers as a better means for a fast reliable DSL connection.

DSL routers on the other hand are hardware based solutions for fast internet access. They do not require special software to be installed into your OS nor do they take up addresses that could cause conflicts with devices already installed in your computer. Since DSL routers use a hardware solution instead of software drivers to connect your computer to the internet, they are compatible with many operating systems including Windows 9x, Windows NT, Windows 2000, Macintosh, Linux, Unix and any other operating system that uses TCP/IP protocols to communicate to the Internet. Routers also bring forth an abundant amount of utilities already programmed into the router. Among the list of utilities included are VPN (Virtual Private Network) support, NAT (Network Address Translation), firewall capabilities (Security Features), DHCP (Dynamic Host Common Protocol), etc. Unlike modems which support only one computer, routers support from one to several to many computers. It is also possible to run servers that require a static routable IP address such as Net Meeting, http (web), smtp (mail), pop3 (mail), ftp (File Transfer Protocol), snmp (Simple Network Management Protocol), telnet, DNS (Domain Name Service), Quake, Unreal, etc.

Although DSL modems are cheaper, there is no comparison between the functionality and flexibility that a DSL router can offer to your network. If you want a fast solid Internet connection without giving way to both security and usability, choose a DSL router. If you would prefer to cut cost, loose out on the mentioned options and use only one computer choose a DSL modem. Every LevelOne Broadband Cable/ADSL Router will cut the cost of our users dramatically by giving them the option to use utilities already present in the router without buying additional third party software and hardware.

Search for LevelOne Cable/ADSL Routers (Products)...

The speed that you see on Netscape Navigator or Microsoft Internet Explorer when data is being transmitted is measured in KBps (kilo bytes per second). Our Broadband lines are sold based on Kbps (kilo bits per second) or Mbps (megabits per second). When transferring data, there are 8 bits in each byte.

Total data throughput includes your data (the payload) plus the overhead associated with the data transport protocols needed to route your data, perform error checking, etc. Two protocols are required to transport your data over a Broadband circuit: TCP/IP and ATM.

TCP/IP is the standard protocol that makes the Internet possible. However, it imposes an overhead of at least 40 bytes per packet of payload transmitted. Every data packet is encapsulated in a TCP/IP wrapper as it leaves the originating computer. Since most data packets are under 400 bytes, this means that at least 10% of your bandwidth is consumed by the TCP/IP protocol.

ATM is the protocol used to control data transmission between your Broadband router and the edge router (the edge router is where you are connected into the Internet). This protocol breaks up the TCP/IP packets into "cells" of 48 bytes each for most efficient transmission between your LevelOne Broadband router and edge router. However, an additional 5 bytes are required for the header of each ATM cell, so a further 10% of the bandwidth is consumed by this protocol's overhead.
Additional bandwidth is consumed because cells or packets are not always completely filled. For example many acknowledgment messages are very short - just 1 or 2 bytes - but each requires a full TCP/IP header.

So the real world file transfer rate you would typically see is about 80% of the sync speed of your Broadband circuit. For example, if you have a 1.0Mbps Broadband circuit, its sync speed is 1.0Mbps and the total data transfer rate is 1 million bits per second or 125,000 bytes per second. But TCP/IP and ATM require 20% of this bandwidth leaving you with 100,000 bytes per second as a maximum. Let's say you're trying to copy a 10 Megabyte file - the absolutely best speed would be 100 seconds (10MB divided by 100,000 bytes per second). However, the file transfer protocol (FTP) requires the receiving machine to send acknowledgments every now and will impact file throughput. Then there's congestion on the Internet. And lastly the machine sending you the file may also be dealing with thousands of other file requests at the same time which impact the system file transfer rate.

Thus, in the real world of the Internet, 75-85% of circuit sync speed is a realistic expectation for the net data transfer. Most popular web sites have many users sharing them simultaneously and cannot match this data rate.

Full-duplex data transmission means that data can be transmitted in both directions on a signal carrier at the same time. For example, on a local area network with a technology that has full-duplex transmission, one workstation can be sending data on the line while another workstation is receiving data. Full-duplex transmission necessarily implies a bidirectional line (one that can move data in both directions).

A home network is two or more computers interconnected to form a local area network (LAN) within the home. A home network allows computer owners to interconnect multiple computers so that each can share files, programs, printers, other peripheral devices, and Internet access with other computers, reducing the need for redundant equipment and, in general, making everything easier to use. For example, if you have an older computer without a CD-ROM, you can access your newer computer's CD-ROM instead of purchasing one for your older computer. Sharing files across a home network is also easier than copying a file to a floppy and running to the other computer to use the file. A new trend, sometimes referred to as an intelligent network, extends the home network to include controls for the home ambient environment, security systems, and kitchen devices. In general, a home network is distinguished from a small office-home office (SOHO) network only by its more general purpose and possibly by the kinds of devices that are interconnected.

Before deciding what kind of home network you want, you must ask yourself if it bothers you to drill holes and run wire throughout your house? Do you mind opening your computer and installing network cards? Are your computers in the same room? What is your budget for a home network? Do you mind paying someone to come in and do the setup for you?

With LevelOne products you can build home networks, that use wire connections or wireless networks:

- Direct cable connection: This allows you to connect both computers with a null modem that plugs into both computers' serial, parallel, or Universal Serial Bus (USB) port. You simply configure the Windows 9x/NT Direct Cable Connection feature and you're ready to go. You lose your printer's parallel port if you use a parallel port connection. USB is faster than both serial and parallel, but you must make sure you are using Windows 95B or Windows 98 when using a USB network. This is a possible choice when two computers are in the same room.
- Traditional Ethernet: A peer-to-peer Ethnernet network requires installing network interface cards (NIC) inside each computer and interconnecting them with a coaxial cable cable or a twisted pair cable. You have to install driver and configure Windows 9x/NT. This type of network is suitable for use with two to twelve computers. (Search for LevelOne network interface cards and LevelOne PalmCon Hubs/Switches and levelOne SohoCon products…)
- Wireless LAN: see 'What ist Wireless LAN?'

In general, a hub is the central part of a wheel where the spokes come together. The term is familiar to frequent fliers who travel through airport "hubs" to make connecting flights from one point to another. In data communications, a hub is a place of convergence where data arrives from one or more directions and is forwarded out in one or more other directions. A hub usually includes a switch of some kind. (And a product that is called a "switch" could usually be considered a hub as well.) The distinction seems to be that the hub is the place where data comes together and the switch is what determines how and where data is forwarded from the place where data comes together. Regarded in its switching aspects, a hub can also include a router.

1) In describing network topologies, a hub topology consists of a backbone (main circuit) to which a number of outgoing lines can be attached ("dropped"), each providing one or more connection port for device to attach to. For Internet users not connected to a local area network, this is the general topology used by your access provider. Other common network topologies are the bus network and the ring network. (Either of these could possibly feed into a hub network, using a bridge.)

2) As a network product, a hub may include a group of modem cards for dial-in users, a gateway card for connections to a local area network (for example, an Ethernet or a token ring), and a connection to a line (the main line in this example).

A stackable hub is a hub designed to be connected and stacked or positioned on top of another hub, forming an expanding stack. Since a hub is basically a concentrator of device connections, a set of stackable hubs is just a bigger concentrator. The stackable approach allows equipment to be easily and economically expanded as a grows in size. The stacking feature also reduces clutter.

Typically, devices with network interface cards (NIC) are connected to each hub with shielded twisted pair (STP) or unshielded twisted pair (UTP) cable. The set of stackable hubs is interconnected with a very short "cascading" cable in the rear of the stack. A special port, such as an Ethernet Attachment Unit Interface (AUI) port, may be provided to connect the set of stackable hubs to a backobne cable that connects to other sets of stackable hubs or other network devices.

Typical stackable hub options include:
- the ability to mix hubs, router and other devices in the same stack,
- fault tolerance so that if one hub fails, the other hubs in the stack can continue to operate,
- port redundancy so that if one port fails, a backup port can be automatically substituted,
- hardware and software to let you manage the stackable hubs using the Simple Network Management Protocol (SNMP).

In telecommunications, a switch is a network device that selects a path or circuit for sending a unit of data to its next destination. A switch may also include the function of the router, a device or program that can determine the route and specifically what adjacent network point the data should be sent to. In general, a switch is a simpler and faster mechanism than a router, which requires knowledge about the network and how to determine the route.

Relative to the layered Open Systems Interconnection (OSI) communication model, a switch is usually associated with layer 2, the Data-Link layer. However, some newer switches also perform the routing functions of layer 3, the Network layer. Layer 3 switches are also sometimes called IP switches.

On larger networks, the trip from one switch point to another in the network is called a hop. The time a switch takes to figure out where to forward a data unit is called its latency. The price paid for having the flexibility that switches provide in a network is this latency. Switches are found at the backbone and gateway levels of a network where one network connects with another and at the subnetwork level where data is being forwarded close to its destination or origin. The former are often known as core switches and the latter as desktop switches.

Search for LevelOne Hubs and Switches…

On a local area network (LAN) or other network, the MAC (Media Access Control) address is your computer's unique hardware number. (On an Ethernet LAN, it's the same as your Ethernet address.) When you're connected to the Internet from your computer (or host as the Internet protocol thinks of it), a correspondence table relates your IP address to your computer's physical (MAC) address on the LAN.

MDI/MDIX is a type of Ethernet port connection using twisted pair cabling. The MDI (for medium dependent interface) is the component of the media attachment unit (MAUI) that provides the physical and electrical connection to the cabling medium. An MDIX (for MDI crossover) is a version of MDI that enables connection between like devices. MDI ports connect to MDIX ports via straight-through twisted pair cabling; both MDI-to-MDI and MDIX-to-MDIX connections use crossover twisted pair cabling.

A network interface card (NIC) is a computer circuit board or card that is installed in a computer so that it can be connected to a network. Personal computers and workstations on a local area network (LAN) typically contain a network interface card specifically designed for the LAN transmission technology, such as Ethernet or token ring. Network interface cards provide a dedicated, full-time connection to a network.

Search for LevelOne Network Interface Cards…

Twisted pair is the ordinary copper wire that connects home and many business computers to the telephone company. To reduce crosstalk or electromagnetic induction between pairs of wires, two insulated copper wires are twisted around each other. Each connection on twisted pair requires both wires. Since some telephone sets or desktop locations require multiple connections, twisted pair is sometimes installed in two or more pairs, all within a single cable. For some business locations, twisted pair is enclosed in a shield that functions as a ground. This is known as shielded twisted pair (STP). Ordinary wire to the home is unshielded twisted pair (UTP).

Twisted pair is now frequently installed with two pairs to the home, with the extra pair making it possible for you to add another line when you need it.

Twisted pair comes with each pair uniquely color coded when it is packaged in multiple pairs. Different uses such as analog, digital and Ethernet require different pair multiples.

Although twisted pair is often associated with home use, a higher grade of twisted pair is often used for horizontal wiring in LAN installations because it is less expensive than coaxial cable.

Wake on LAN is a technology that allows a network professional to remotely power on a computer or to wake it up from sleep mode. By remotely triggering the computer to wake up and perform scheduled maintenance tasks, the technician does not have to physically visit each computer on the network. Wake on LAN works by sending a wake-up frame or packet to a client machine from a server machine that has remote network management software installed. The Wake on LAN network adapter installed in the client receives the wake-up frame and turns on. The scheduled tasks then begin.

To use Wake on LAN technology you need a Wake on LAN network adapter, Wake on LAN enabled motherboard, and remote management software (Search for the LevelOne WOL Interface card).

The Wake on LAN network adapter continually monitors the network looking for wake-up frames. The adapter must have a constant power source in order to boot up, which is usually from a special power supply that delivers a certain amount of power continually. The Wake on LAN adapter also decodes the wake-up frame to determine if it is a wake-up. The key to determining a wake-up frame is if the media access control (MAC address) address is repeated 16 times without breaks or interruptions.

The motherboard must contain a complementary metal-oxide semiconductor (CMOS) that is designed to use Wake on LAN technology.

The remote management software sends the wake-up frames. This software also enables a professional to disable Wake on LAN technology. The remote management software allows the scheduling of tasks that are needed and tells the computer to shut down or go into sleep mode when done.

Wireless is a term used to describe telecommunications in which electromagnetic waves (rather than some form of wire) carry the signal over part or all of the communication path. Some monitoring devices, such as intrusion alarms, employ acoustic waves at frequencies above the range of human hearing; these are also sometimes classified as wireless.

The first wireless transmitters went on the air in the early 20th century using radiotelegraphy (Morse code). Later, as modulation made it possible to transmit voices and music via wireless, the medium came to be called "radio." With the advent of television, fax, data communication, and the effective use of a larger portion of the spectrum, the term "wireless" has been resurrected.

Common examples of wireless equipment in use today include:
-Cellular phones and pagers ## provide connectivity for portable and mobile applications, both personal and business,
- Global Positioning System (GPS) ## allows drivers of cars and trucks, captains of boats and ships, and pilots of aircraft to ascertain their location anywhere on earth,
- Cordless computer peripherals – the cordless mouse is a common example; keyboards and printers can also be linked to a computer via wireless,
- Cordless telephone sets ## these are limited-range devices, not to be confused with cell phones,
- Home-entertainment-system control boxes ## the VCR control and the TV channel control are the most common examples; some hi-fi sound systems and FM broadcast receivers also use this technology,
- Remote garage-door openers ## one of the oldest wireless devices in common use by consumers; usually operates at radio frequencies,
- Two-way radios ## this includes Amateur and Citizens Radio Service, as well as business, marine, and military communications,
- Baby monitors ## these devices are simplified radio transmitter/receiver units with limited range,
- Satellite television ## allows viewers in almost any location to select from hundreds of channels,
- Wireless LANs or local area networks ## provide flexibility and reliability for business computer users.

Wireless technology is rapidly evolving, and is playing an increasing role in the lives of people troughout the world. In addition, ever-larger numbers of people are relying on the technology directly or indirectly.

A wireless LAN is one in which a mobile user can connect to a local area network (LAN) through a wireless (radio) connection. A standard, IEEE 802.11, specifies the technologies for wireless LANs. The standard includes an encryption method, the Wired Equivalent Privacy algorithm.

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Wi-Fi is the popular term for a high-frequency wireless local area network (WLAN). The Wi-Fi technology is rapidly gaining acceptance in many companies as an alternative to a wired LAN. It can also be installed for a home network. Wi-Fi is specified in the 802.11b specification from the Institute of Electrical and Electronics Engineers (IEEE) and is part of a series of wireless specifications together with 802.11, 802.11a, and 802.11g. All four standards use the Ethernet protocol and CSMA/CA (carrier sense multiple access with collision avoidance) for path sharing.

The 802.11b (Wi-Fi) operates in the 2.4 GHz range offering data speeds up to 11 megabits per second. The modulation used in 802.11 has historically been phase-shift keying (PSK). The modulation method selected for 802.11b is known as complementary code keying (CCK), which allows higher data speeds and is less susceptible to multipath-propagation interference.

Unless adequately protected, a Wi-Fi wireless LAN can be susceptible to access from the outside by unauthorized users, some of whom have used the access as a free Internet connection! (The activity of locating and exploiting security-exposed wireless LANs is commonly known as war driving.) Companies that have a wireless LAN are urged to add security safeguards such as the Wired Equivalent Privacy (WEP) encryption standard, the setup and use of a virtual private network (VPN) or IPsec, and a firewall or DMZ.

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