10-100..
(Or 10+100) Refers to a device having both 10Mbps Ethernet and 100Mbps Fast Ethernet connections, on separate ports. This is in contrast to 10/100, which has connections on the same port.
See also 10/100, auto negotiation, Ethernet, Fast Ethernet, Mbps, port.
10/100
Refers to a device having both a 10Mbps Ethernet and 100Mbps Fast Ethernet connection on the same port. This is in contrast to 10-100, which has both connections on different ports.
See also 10-100, auto negotiation, Ethernet, Fast Ethernet, Mbps, port.
This is a technical specification used for Ethernet networks. 10BASE-T is part of the IEEE standards body specification for Ethernet (10Mbps) over Category 3, 4 or 5 twisted pair cable (two pairs of wire—one pair for transmitting data and the other for receiving data). 10BASE-T has a distance limit of approximately 100m (328ft) per segment.
See also Category 3 cabling, Category 5 cabling, Ethernet, IEEE, Mbps, network, segment, STP, twisted pair, UTP.
This is a technical specification used in Ethernet networks. 10BASE2 is part of the IEEE standards body specification for 10Mbps Ethernet, and is thin coaxial cable, also known as thinnet or cheapernet. 10BASE2 has a distance limit of approximately 185m (607ft) per segment.
See also coaxial cable, Ethernet, IEEE, Mbps, network, segment.
This is a technical specification used in Ethernet networks. 10BASE5 is part of the IEEE standard body specification for 10Mbps Ethernet, and is thick coaxial cable. 10BASE5 has a distance limit of approximately 500m (1640ft) per segment.
See also coaxial cable, Ethernet, IEEE, Mbps, network, segment.
This is a technical specification used in Ethernet networks. 10BASE-FL is part of the IEEE standards body specification for using fiber-optic cabling that runs at 10Mbps (Ethernet). Segments in a network using 10BASE-FL cabling can be up to 2km (1.24 mile) long.
See also fiber-optic cabling, IEEE, Mbps, network, segment.
This is a technical specification used in Fast Ethernet networks. 100BASE-FX is part of the IEEE standards body specification for using fiber-optic cabling that runs at 100Mbps (Fast Ethernet).
See also Ethernet, Fast Ethernet, fiber-optic cabling, IEEE, Mbps, network.
This is a technical specification used in Fast Ethernet networks. 100BASE-TX is part of the IEEE standards body specification for 100Mbps (Fast Ethernet) Category 5 UTP (unshielded twisted pair) or STP (shielded twisted pair) cable (two pairs of wire—one pair for transmitting data and the other for receiving data).
See also Category 5 cabling, Ethernet, Fast Ethernet, IEEE, Mbps, network, STP, UTP.
adapter card
Adapter cards are also referred to as a NICs. See NIC for more information.
On all OfficeConnect® devices, there are a series of LEDs (light emitting diodes) that provide status information about the device. On OfficeConnect hubs, the Alert LED alerts you to abnormal network conditions and is shaped like an exclamation mark (!).
See also hub, LED, network, OfficeConnect®.
Attachment Unit Interface. This is an IEEE 802.3 (Ethernet) standard interface that allows you to connect a PC or an Ethernet device to an Ethernet network. For example, a hub (OfficeConnect® TP4Combo) with an AUI port can be connected using a transceiver to an Ethernet network running on thick coaxial cabling. Your PC may have a NIC (network interface card) with a 15-pin AUI socket.
See also Ethernet, IEEE, network, NIC, OfficeConnect®, PC, transceiver.
Some devices in the OfficeConnect® range support auto negotiation.
Auto negotiation is where two devices sharing a link, automatically configure to use the best common speed. The order of preference (best first) is: 100BASE-TX full duplex, 100BASE-TX half duplex, 10BASE-T full duplex, and 10BASE-T half duplex. Auto negotiation is defined in the IEEE 802.3 standard for Ethernet and is an operation that takes place in a few milliseconds.
See also 100BASE-TX, 10BASE-T, duplex, full duplex, half duplex, IEEE, network, OfficeConnect®
auto sensing
Some devices in the OfficeConnect® range support auto sensing.
This is where a port that can operate at different speeds (for example, 10Mbps and 100Mbps) has the ability to detect the speed of another port to which it is connected; both ports will automatically configure to use the best common speed. The term has become interchangeable with auto negotiation, which is similar.
See also auto negotiation, Mbps, OfficeConnect®, port
backbone
The main cable that connects network segments. A cable that carries information between relatively remote devices, for example between two hubs on opposite sides of a building.
See also hub, segment.
Bandwidth is a measure of the information capacity of a communication link. For example, Ethernet has a bandwidth of 10Mbps.
Workstations or network users that use the network heavily are referred to as using a high bandwidth—these are usually users who do a lot of graphical or multi-media work across the network.
Bandwidth is the difference between the highest and lowest frequencies of a communication link, expressed in Hertz (Hz).
See also Ethernet, Mbps, network.
baud
This is the signalling rate of a line, in other words, the rate at which data travels along a line. Baud is the number of transitions (voltage or frequency changes) made per second.
See also bps.
Binary digit. This is the smallest element of computer information. A single digit in a binary number (0 or 1) is a bit. Groups of bits make up larger units of data in computer systems—the most commonly known of which is the byte (eight bits).
See also bps, byte.
bit rate
The speed at which bits are transmitted, usually expressed in bits per second (bps).
See also bps, bit.
British Naval Connector. BNC connectors are used to connect, extend or terminate coaxial cable networks, such as Ethernet. Some OfficeConnect® hubs have a BNC port.
There are various connectors, such as the BNC T-connector, the BNC barrel connector and the BNC terminator.
See also 10BASE2, coaxial cable, OfficeConnect®, port, transceiver.
bits per second. bps is used as a measurement for transmission of data in a communications system.
See also bit, Kbps, Mbps.
Bridges provide a way to join two or more networks together to form a single logical network, and are similar to switches. The networks that are joined together are referred to as network segments in the resulting network. Bridges can connect LANs of a different network type, for example, Ethernet to Fast Ethernet, or Ethernet to Token Ring.
Bridges can be installed into networks for the following reasons:
To increase the size or number of nodes for the entire network.
To reduce traffic bottlenecks caused by an excessive number of nodes.
To link different types of network, such as Ethernet and Token Ring, and forward packets between them.
See also Ethernet, Fast Ethernet, LAN, network, node, packet, segment, switch, Token Ring, traffic.
Both source and destination addresses are dealt with by bridges. The source address of a packet is the address of the device that initiates the transmission of the packet. The destination address is the address of the device for which the packet is intended. The distinction between source and destination device addresses is important to the operation of bridges. Bridges use source addresses to learn which network segment PCs and network devices are on, and then use this knowledge to forward packets based on the destination address.
Bridges, like routers, also perform filtering, whereby certain packets can be prevented from being passed on (using source and destination address as criteria). This allows only essential internetwork traffic to cross the bridge thereby reducing internetwork traffic.
Bridges work at the data link layer (layer 2) of the OSI reference model, compared to routers that operate at layer 3, the network layer. The routing information contained in higher level protocol packets is invisible to them, and they cannot tell the difference between packets encoded in different network layer protocols.
See also, filtering, internetwork, network, node, OSI reference model, packet, protocol, repeater, router, switch, Token Ring, traffic.
A data packet forwarded by a device to all nodes on a network, or broadcast domain.
See also broadcast storm, multicast, network, packet, unicast.
Multiple simultaneous broadcasts that typically absorb available network bandwidth and can cause a network to slow down or become unusable. A broadcast storm may occur, for example, due to faulty network equipment.
See also bandwidth, broadcast, network. byte
A unit of data equivalent to eight binary digits (bits). A byte holds the equivalent of a single character, such as a letter of the alphabet (a) or an ampersand (&). Measurements on storage devices, such as disks and databases, are given in bytes.
See also bit.
See Category 3 cabling.
See Category 5 cabling.
One of five grades of twisted pair (TP) cabling defined by the EIA/TIA-586 standard. Category 3 is voice grade cable used in 10BASE-T networks (Ethernet) to transmit data at speeds of up to 10Mbps.
See also 10BASE-T, Category 5 cabling, EIA, Ethernet, Fast Ethernet, Mbps, network, TIA, twisted pair.
One of five grades of twisted pair cabling defined by the EIA/TIA-586 standard. Category 5 is used in 100BASE-T networks (Fast Ethernet) and can transmit data up to speeds of 100Mbps. Category 5 cabling is better to use for network cabling than Category 3, because it supports both Ethernet (10Mbps) and Fast Ethernet (100Mbps) speeds.
See also 100BASE-T, Category 3 cabling, EIA, Ethernet, Fast Ethernet, Mbps, network, TIA, twisted pair.
According to rules that define Fast Ethernet networks (IEEE 802.3u), networking devices are classified. All 3Com Fast Ethernet OfficeConnect hubs are Class II. This means that two Class II hubs can be directly connected together; Class I hubs cannot.
See also Ethernet, Fast Ethernet, hub, IEEE, OfficeConnect®.
This is the FCC (Federal Communications Commission) certification of radiation limits applied to digital devices. Class A is for business use. Class B is for residential use and is more stringent in order to avoid interference with televisions and other receiving devices. All OfficeConnect® devices have both Class A and B certification.
See also FCC, OfficeConnect®.
A computer system or workstation that requests a service or the contents of a file from a file server.
See also client/server, client/server network, server.
A network architecture whereby a system is divided into two parts: the client (front end) is a requesting machine (usually a PC), and the server (back end) is a supplying machine. Both terms can be applied to hardware devices or software programs.
See also client, client/server network, network, server.
client/server network
A local area network (LAN) structure in which network resources are centralized and controlled from one or more servers. Individual workstations or clients (such as PCs) must request services through the server(s).
See also client, client/server, LAN, network, PC, peer-to-peer network, server, traffic.
coax
See coaxial cable.
This is a high-capacity networking cable. Coaxial cable (or coax) consists of a hollow outer braided copper or foil shield surrounding a single inner copper conductor with plastic insulation between the two conducting layers. Coaxial cable is used for both broadband (for example, cable TV) and baseband (for example, Ethernet) communications networks. Coaxial cable is usually free from external interference and capable of high transmission rates over long distances.
See also network, STP, UTP.
A term used to describe two colliding packets in an Ethernet or Fast Ethernet network. Collisions are a part of normal Ethernet or Fast Ethernet operation, but a sudden prolonged increase in the number of collisions can indicate a problem with a device, particularly if they are not accompanied by a general increase in traffic. On coaxial segments, an increase in collisions can indicate faulty cabling.
See also coaxial cable, Ethernet, Fast Ethernet, packet, traffic.
Excessive network traffic.
See also network, traffic.
cross-over cable
A cross-over cable has its transmit and receive wires crossed. For a connection between two devices to work, the receiver of one device must be connected to the transmitter of the other.
Therefore, when connecting two MDI ports or two MDI-X ports, a cross-over cable must be used.
See also EIA/TIA-232, MDI, MDI-X, PC, port.
crosstalk
Interference on a cable or piece of equipment created by a signal in an adjacent cable or piece of equipment. Crosstalk can affect the quality of data transmission.
Carrier-sense Multiple Access with Collision Detection. This is the protocol defined in Ethernet and Fast Ethernet standards (IEEE 802.3) in which devices transmit only after finding a data channel clear for a period of time. When two devices transmit simultaneously, a collision occurs and the devices involved in the collision delay retransmitting for a random length of time.
See also collision, Ethernet, Fast Ethernet, IEEE, protocol.
datagram
A TCP/IP or IPX message that contains Internet source and destination addresses and data which is used to route the packet through a network. Datagrams are the primary information units used on the Internet.
See also Internet, TCP/IP.
Disk Operating System. A computer operating system developed by Microsoft and IBM: IBM PCs use PC-DOS, and non-IBM PCs use MS-DOS. Microsoft’s Windows® 95 and Windows NT® are newer computer operating systems than DOS.
See also PC.
driver
Software that controls a port such as a network interface card (NIC), keyboard, printer or monitor. Network equipment (such as hubs) attached to PCs requires drivers that the PC uses to communicate with them.
See also NIC, PC, port.
duplex
Transmission that permits simultaneous two-way communication. Duplex is synonymous with full duplex.
See also full duplex, half duplex.
Cable that contains both a transmit (Tx) and receive (Rx) channel.
See also full duplex, half duplex.
Electronic mail. This is the transmission of messages to individuals or groups, over a network. E-mails may contain text messages, tables, charts, pictures as well as attachments. The use of E-mail in an office environment can reduce the need for paper, as memos and inter-office communication can be sent over the network, thereby saving time and valuable resources.
See also network
Electronic Industries Association. An industry trade organization that, together with the TIA (Telecommunications Industry Association), sets standards for electrical consumer products. The EIA and TIA specifies data transmission standards such as EIA/TIA-232.
See also EIA/TIA-232, TIA.
The EIA/TIA-232 is a standard for a 25-pin serial interface that can be used to connect computers to networking equipment. (EIA/TIA-232 was formerly known as RS-232.)
See also EIA, network, TIA.
Electromagnetic compatibility. The ability of a device to operate effectively in the environment in which it was intended, without receiving electromagnetic interference (EMI) from other devices and equipment, or generating it.
Ethernet was invented by Xerox Corporation and developed jointly by Xerox, Intel, and Digital Equipment Corporation (DEC) and is a widely used LAN technology.
Ethernet networks use the CSMA/CD protocol and run over various cables at a rate of 10Mbps; they are used by, for example, TCP/IP and XNS protocols. Ethernet is similar to a series of standards produced by IEEE referred to as IEEE 802.3.
See also CSMA/CD, Ethernet, Fast Ethernet, IEEE, LAN, Mbps, protocol, TCP/IP,
XNS.
Fast Ethernet operates at 100Mbps and so has 10 times more bandwidth than Ethernet, enabling it to cope with larger amounts of traffic; this results in operation 10 times faster than Ethernet. Fast Ethernet runs over the various 100BASE (cables): for example, 100BASE-FX and 100BASE-TX.
Fast Ethernet networks operate at 100Mbps and are based on the 10BASE-T Ethernet CSMA/CD network access method, an extension to the IEEE 802.3 specification.
See also 10BASE-T, 100BASE-T, 100BASE-TX, 100BASE-FX, bandwidth, CSMA/CD, Ethernet, IEEE, Mbps, network, traffic.
Federal Communications Commission. The regulatory telecommunications body for the U.S.A. that licenses and controls electronic and electromagnetic transmission standards. The FCC specifies bandwidth ranges for different communication channels.
Fiber Distributed Data Interface. This is a network standard for high speed transmission over fiber-optic cable. FDDI uses two rings of fiber-optic cabling (providing greater resilience) and transmits at 100Mbps at distances up to 2km (1.24 mile) between nodes. FDDI is typically used as a backbone technology providing connectivity between Ethernet and Token Ring networks. It is used in critical applications, for example in an airport.
See also backbone, Ethernet, fiber-optic cable, LAN, Mbps, node, packet, protocol, server, Token Ring.
A cable containing one or more optical fibers used for transmitting data in the form of light. Fiber-optic cable is more expensive than copper but is not susceptible to electromagnetic interference and is capable of higher data transfer speeds over greater distances.
A process where network traffic is screened for certain characteristics, such as destination address (the address of the device for which the packet is intended) or protocol. From this process it is determined whether traffic is forwarded based on the established criteria. This allows only essential internetwork traffic to cross a bridge thereby reducing internetwork traffic.
Filtering in routers can prevent unauthorized access to a network or host on a network; this barrier is often called a firewall. Filtering is performed by bridges, switches and routers.
See also bridge, internetwork, network, packet, protocol, router, switch, traffic.
firewall
A firewall in a network is a node set up as a barrier to prevent traffic crossing from one segment to another. Firewalls are used to improve network traffic as well as for security purposes, and may serve as a barrier between connected public and private networks. A firewall may be implemented in a router or it may be a network device specialized for this purpose.
See also network, node, router, segment, traffic.
A frame is a set of bits that form a basic block of data. Usually, a frame contains its own control information, including the address of the device to which it is being sent.
From a piece of networking equipment, frames can be unicast (sent to a single device), multicast (sent to multiple devices) or broadcast (sent to all devices).
See also broadcast, multicast, packet, unicast.
The ability of a device or line to transmit data simultaneously in both directions over the same communications link, potentially doubling the throughput of traffic.
See also bandwidth, duplex cable, half duplex.
gateway
A device that interconnects networks with different, incompatible communications protocols. The gateway performs a protocol conversion to translate one set of protocols to another (for example, from TCP/IP to IPX).
See also network, IPX, OfficeConnect®, OSI reference model, protocol, TCP/IP.
The term half duplex is used to describe data transmission that can occur in two directions over the same communications link, in only one direction at a time. Hubs only operate in half duplex mode, as opposed to switches which can operate in both full duplex and half duplex.
See also duplex cable, full duplex, hub, switch.
A hub is a device used in a network that serves as the central location for connecting workstations together. The term hub is often used as a generic term for a piece of networking equipment.
See also bit, bridge, network, OfficeConnect®, repeater, router, switch.
Institute of Electrical and Electronics Engineers. This organization was founded in 1963 and sets standards for computers and communications. The committee that formed the 802 standards for networking was set up in 1980 to ensure that systems and devices manufactured by different vendors could communicate with the minimum of complications, allowing global compatibility across products.
The Internet is a worldwide network composed of government, academic, commercial, military and corporate networks spanning the world.
The Internet was originally developed for the U.S. military and then became widely used for academic and commercial research. Users accessing the Internet can read and download data on virtually any subject from almost anywhere in the world.
See also intranet, network, WWW.
A collection of networks (that may be dissimilar in type) interconnected by routers, gateways, or other devices, so that they can function as a single, large network. Sometimes called an internet, which is not the same as the Internet (the World Wide Web).
See also Internet, network, router, WWW.
intranet
Intranets are internal, private networks used by companies and academic institutions worldwide. Intranets are secure from public access and serve as databases of information in the same format as that used by the World Wide Web.
See also internet, network, World Wide Web.
Internet Protocol. IP is a layer 3 network protocol (of the OSI reference model) that is the standard for sending a basic unit of data (an IP datagram) through an internetwork. IP is part of the TCP/IP set of protocols describing the routing of packets to addressed devices.
See also datagram, Internet, internetwork, packet, protocol, OSI reference model, TCP/IP.
Internet Packet Exchange. A communications protocol devised by Novell® for Novell NetWare®. IPX packets can be routed from one network to another at layers 3 and 4 of the OSI reference model.
See also Internet, network, OSI reference model, packet.
Integrated Services Digital Network. An international telecommunications standard for transmitting voice, video, and data over digital lines running at 64Kbps. ISDN is used for private or public digital telephone networks where binary data, such as graphics and digitized voice and data transmission, pass over the same digital network that carries most telephone transmissions today.
See also Kbps, network, OfficeConnect®.
Kilobits per second. The measurement of the speed of data transfer in a communications system. One kilobit is equal to 1000 bits.
See also bit, Mbps.
Local Area Network. A network of connected devices (such as PCs, printers, servers and hubs) covering a relatively small geographic area (usually not larger than a floor or building). LANs are characterized by high transmission speeds over short distances. Ethernet, FDDI and Token Ring are widely used technologies for configuring LANs.
See also Ethernet, Fast Ethernet, FDDI, hub, network, server, Token Ring.
This is a peer-to-peer operating system developed by the company Artisoft. for Ethernet and Token Ring networks.
See also Ethernet, network, peer-to-peer networks, Token Ring.
Light Emitting Diode. A semi-conducting light source that emits light by converting electrical energy. LEDs on 3Com OfficeConnect® products provide status information on the device and the network to which it is attached.
See also network, OfficeConnect®.
link
Physical connection between two nodes in a network.
See also network, node.
loop
See network loop.
The abbreviation for Macintosh® computer.
Media Access Control. A protocol for determining which devices have access to a network at any one time, specified by the IEEE. The MAC protocol differs depending on the method used to connect the network (for example Token Ring or Ethernet).
See also Ethernet, IEEE, MAC address, network, protocol, Token Ring.
Media Access Control address; also called hardware address or physical address. An address associated with a particular network device. NICs and managed devices that connect to a LAN have a MAC address assigned to them as MAC addresses are used to identify devices in a network. MAC addresses are 6 bytes long, are specified by the IEEE and are preassigned to your network equipment.
See also byte, IEEE, LAN, MAC, managed device, network, NIC.
managed device
Managed devices are those that support network management. Two devices in the OfficeConnect® range that are managed products are the OfficeConnect Switch 140M and the OfficeConnect Hub 8/TPM.
See also network management, OfficeConnect®.
Megabits per second (not to be confused with megabytes per second—MBps). The measurement of the speed of data transfer in a communications system. A megabit is one million bits. Ten megabits per second (10Mbps) means that 10 million pulses are transmitted per second in a communications system.
See also bit, MBps.
MegaBytes per second (not to be confused with megabits per second—Mbps). The measurement of the speed of data transfer in a communications system. A megabyte is approximately one million bytes. [1 MB = 1,048,576 bytes.]
See also byte, Mbps.
Medium Dependent Interface. MDI refers to an Ethernet port connection. The IEEE 802.3 network standard defines MDI as the electrical and mechanical interface between a piece of equipment and a transmission medium.
Within an RJ45 port there is a transmit line and a receive line. RJ45 ports can be MDI (the lines are uncrossed) or MDI-X (the lines are crossed). For a connection between two devices to work, the receiver of one device must be connected to the transmitter of the other, therefore, the MDI port of one device must be connected to an MDI-X port of another device using straight-through cable.
See also Ethernet, IEEE, MDI/MDIX, network, OfficeConnect®, port, RJ45, straight-through cable.
Medium Dependent Interface/Medium Dependent Interface crossover. The switch located on the back of an OfficeConnect® switch or hub that is used to alter the operation of a specific port. The ‘X’ stands for crossing the transmit and receive lines of a port. An MDI port (uncrossed) connects to the MDI-X (crossed) port of another hub.
An example of using the MDI/MDI-X switch is given below. The diagram shows three OfficeConnect hubs connected by 10BASE-T cable to form a stack.
Starting from the bottom, connect the highest numbered port of the lower hub in the stack to any port of the hub immediately above. Repeat this for each hub.
Set all MDI/MDIX switches to MDI (in) except for the top hub (the one with the highest numbered port not connected to another hub). This unused port can be connected to a PC provided that the MDI/MDIX switch is set to MDIX (out).
See also 10BASE-T, hub, OfficeConnect®, MDI, port, switch.
modem
MOdulator–DEModulator. A device that adapts a computer’s digital signal into audio frequencies (analogue) for transmission down a telephone line, and adapts them back again. Transmission speeds of modems generally range from 2,400bps (2.4Kbps) to 56,000bps (56Kbps).
See also bps, Kbps.
multicast
A message sent simultaneously to a specific group of nodes on a network.
See also broadcast, network, node.
NetBIOS Extended User Interface. This is an enhanced version of the NetBIOS protocol used by network operating systems (NOS), such as Microsoft’s Windows NT®. NetBEUI is pronounced “netbooey”.
See also frame, LAN, NetBIOS, network, NOS, protocol.
NetBIOS
Network Basic Input/Output System. A common network protocol for local area networks (LANs) that contain PCs (personal computers).
NetBIOS is an established network standard that provides the interface between a PC’s operating system and its input/output channel. NetBIOS was later formalized in NetBEUI.
See also frame, LAN, NetBEUI, network, NOS, OSI reference model, PC, protocol.
NetWare®
A network operating system (NOS) developed by Novell®. NetWare supports DOS, Mac and UNIX, plus various LAN network technologies such as Ethernet, and Token Ring. For a more detailed description of network operating systems, refer to NOS.
See also Ethernet, LAN, Mac, network, NOS, Token Ring, UNIX.
network
A group of devices such as computers, printers, hubs, switches, and other hardware, that are connected and are able to communicate with each other. Networks vary in size: some are within a single office, others span the globe.
See also hub, internetwork, network, switch.
network loop
This occurs when two pieces of network equipment are connected by more than one path, thereby causing packets to repeatedly cycle round and round the network and not reach their destination. A repeating hub will detect network loops and automatically partition one of its ports to break the loop.
See also hub, network, packet, partition.
network management
As your network grows, it may be necessary to manage communications on your network. This is called network management. Monitoring a network allows you to diagnose problems and gather statistics on network performance, for administration purposes.
See also hub, managed device, network, OfficeConnect®, switch.
A 3Com trademarked name for PCs that are built with pre-installed drivers and a 3Com network interface card (NIC). Every PC with a 3Com Network Ready logo is certified to be functional in virtually every network operating system environment.
See also driver, network, NIC, NOS, PC.
Network Interface Card. (Also known as an adapter or adapter card.) A circuit board installed into a piece of computing equipment, for example, a PC, enables you to connect your PC to the network.
See also network, OfficeConnect®, PC.
node
A communication device attached to a network, such as a computer or server.
See also network, server.
Network Operating System. A network operating system is software that allows users to share files, printers, faxes, modems and to access a server.
Examples of network operating systems are Windows NT®, Windows® for Workgroups, Windows 95, Novell Netware and LANtastic.
See also DOS, LAN, LANtastic®, modem, NetWare®, OS/2, network, server.
The 3Com OfficeConnect® integrated networking system is designed to take the worry out of building and running a small network. The OfficeConnect family of products provides all the networking capabilities for small businesses and offices which want to share information resources, high-speed access to the Internet and remote connections to other offices.
The range of OfficeConnect products currently available are: an OfficeConnect networking kit, Ethernet and Fast Ethernet hubs, switches and routers.
Open System Interconnection. International computer network standards developed by ISO and CCITT (Consultative Committee for International Telephony and Telegraphy) to create common standards of communication between computers from different manufacturers.
See also network, OSI reference model.
Open Systems Interconnection reference model.
See also Ethernet, Fast Ethernet, hub, Internet, network, router, switch.
packet
A packet is unit of information that your workstations and other equipment send to each other over the network. When information is sent from a computer (for example a text file), it is transmitted over the network as a series of packets.
A packet consists of a set of bits forming a single block of data, containing a header which consists of control information such as sender, receiver, and error-control data, as well as the message itself. Because they are similar units of network data, the terms packet and frame have become interchangeable.
See also bit, frame, hub, network, router, switch.
partition
A partition in a network is when one or more ports are isolated, for example, to remove a network loop. 3Com OfficeConnect® hubs detect network loops and partition their ports to remove the loops.
See also hub, network, network loop, OfficeConnect®, port.
Personal Computer. Although PC is now the term generally used for any personal computer, the original PC standard was developed by IBM.
The PCMCIA created a 16-bit socket into which credit card-sized cards are plugged: these are commonly known as PC cards. The ports on these cards attach, for example, modems, sound cards and hard disks to portable computers.
See also modem, NIC, port, PCMCIA.
Personal Computer Memory Card International Association. This non-profit making organization was set up in 1989 to standardize a method for connecting equipment to portable computers.
See also PC card.
peer-to-peer network
A peer-to-peer network is one in which workstations (such as PCs) can share information and each other’s resources without relying on a centralized server. For example, in a network of four PCs and one hub, it is possible to allow files on all four PCs to be accessed from any other PC.
See also client/server network, hub, network, PC, server.
port
A socket from where data can enter and leave a computer, or a networking device. On a personal computer, the serial (console) and parallel ports are for plugging in communications lines to equipment such as modems, routers and printers.
See also internetwork, modem, router.
power adapter
A power adapter is a transformer that converts the alternating current (AC) from a wall outlet, into direct current (DC) required by an electronic device.
protocol
In networking, a protocol is a formal set of rules and conventions developed by international standards bodies that govern how devices on a network exchange data. A protocol defines format, timing, control and sequence of data in a network.
See also network.
repeater
A repeater is a simple device that regenerates a signal passing through the network, so that the transmission distance of that signal can be extended. A multi-port repeater is known as a hub.
The further a data packet travels along a network, the weaker the signal carrying that data packet becomes. Repeaters repeat (regenerate) data packets they so that neither the number of packets that pass through them, nor the distance they travel, has any effect on signal quality.
Repeaters are also used to connect two LANs of the same network type (for example Ethernet to Ethernet) and work at layer 1 of the OSI reference model.
See also bridge, hub, LAN, network, OSI reference model.
A standard connector used to connect Ethernet networks. The “RJ” stands for “registered jack”.
See also Ethernet, network.
router
Routers provide a link between geographically separate networks. An internetwork based on routing consists of many different logical subnetworks. Bridges and switches connect these subnetworks, improving network performance by keeping traffic within segments. Repeaters and hubs link segments together, and the workstations within the segments.
See also bridge, hub, network, segment, switch, traffic.
Operating at layer 3 of the OSI reference model (called the network layer) routers are concerned not only with the source and destination address of each packet that passes through them, but also with the actual path that each packet takes through the network.
Today, routers generally handle many protocols (such as IP and IPX)—they are multiprotocol routers. A router must have appropriate software for each protocol it supports because, unlike bridges, routers are active devices, meaning that they may make decisions about each packet that passes through them, such as which is the best path a packet can take to reach its destination. For this reason, routers need to know more about protocols than bridges. However, some protocols are unroutable, such as NetBIOS. Unroutable protocols must be bridged.
See also bridge, hub, internetwork, IP, IPX, modem, NetBIOS, OfficeConnect®, OSI reference model, packet, protocol, repeater, segment, switch, traffic.
See EIA/TIA-232.
segment
A group of devices such as PCs, servers or printers that are connected by network equipment. On Ethernet segments, computers can be connected together by hubs, and signals broadcast on that segment are heard by all stations attached to it. If the segment is interconnected to another segment with a bridge or router, it is possible to send packets between those segments. Network segments joined with bridges or routers form internetworks. A segment is often called a subnetwork.
See also bridge, Ethernet, hubs, internetwork, network, packet, PC, router, server.
server
A computer or specialized device in a network that is shared by multiple users. A server provides users with access to shared network services such as computer files and printers.
See also client/server, network.
Sequenced packet exchange. A communications protocol developed by Novell® for use with NetWare® used to control the transport of messages across a network.
See also network, NOS, protocol.
Shielded Twisted Pair. Cabling consisting of one or more pairs of insulated wires used in a variety of network applications. The wires are wrapped in metal to eliminate electromagnetic interference (EMI) and are of a better quality than UTP (Unshielded Twisted Pair).
See also Category 3 cabling, Category 5 cabling, network, twisted pair, UTP.
straight-through cable
A straight-through cable has its wires connected to the same pins at both ends (including the transmit and receive wires). For a connection between two devices to work, the receiver of one device must be connected to the transmitter of the other. Therefore, when connecting an MDIX port to an MDI port, a straight-through cable must be used. Straight-through cable is the most common type of off-the-shelf cable available for networking.
See also MDI/MID-X, port.
switch
A switch is similar to a bridge, but often faster. The term switching is taken from the telecommunications industry where the devices that routed telephone calls were originally called mechanical switches. It is a device specifically designed to solve problems resulting from bandwidth shortages and network bottlenecks (congestion). A switch segments a network into smaller domains, providing a higher percentage of bandwidth to each end station (an end station being, for example, a PC).
See also bandwidth, bridge, congestion, network, OfficeConnect®, PC.
Like a bridge, both source and destination address are dealt with by switches. The source address of a packet is the address of the device that initiates the transmission of the packet. The destination address is the address of the device to which the packet is being sent. Switches learn on the basis of source address, and forward on the basis of destination address. The switch learns the addresses associated with each port on the switch (that is, the switch learns by which port a devices’ communication lines enter it) and builds tables of information that are then used for future switching decisions.
Switching has come to represent an architecture where any inbound traffic can be redirected to any outbound port with relatively little concern for traffic loss or congestion.
See also bandwidth, bridge, congestion, network, OfficeConnect®, packet, PC, port, segment, traffic .
Transmission Control Protocol/Internet Protocol. This is the name for two of the most well-known protocols developed by the U.S. Department of Defense in the 1970s to allow equipment from different vendors to communicate. Originally a UNIX standard, TCP/IP is now supported on almost all platforms, and is the protocol of the Internet.
IP represents the scheme by which two devices (both with IP addresses) communicate. TCP manages the flow of IP packets, ensuring that the packets remain error-free and reach their destination correctly.
See also Internet, internetwork, IP, network, nodes, packet, protocol, UNIX.
thick coax
See 10BASE5.
thin coax
See 10BASE2.
Telecommunications Industry Association. A telecommunications standards organization founded in 1988 in America. The TIA was formed from a spin-off group from the EIA (Electronic Industries Association) to set global telecommunications standards, such as EIA/TIA-232.
See also EIA, EIA/TIA-232.
Developed by IBM, Token Ring offers a method to connect devices in a LAN (local area network). Hence, Token Ring offers the same service as Ethernet, implemented in a different manner: an electronic token (a data packet) is passed around stations in a ring. Most small businesses install Ethernet networks, due to their comparative simplicity to Token Ring.
See also Ethernet, LAN, network, packet.
Token Ring networks take on the physical appearance of a star, but actually operate as a logical ring. A device (such as a PC) takes possession of the token, transmits its data, then frees the token after the data has made a complete circuit of the electrical ring.
The IEEE 802.5 standard specifies the wiring on which Token Ring operates (STP, UTP or fiber-optic cable); Token Ring operates at either 4 or 16Mbps.
See also Ethernet, fiber-optic cable, IEEE, LAN, Mbps, network, packet, PC, STP, UTP.
transceiver
A device that transmits and receives digital and analog signals. In networking, a transceiver is a device that connects an interface to a local area network (LAN). Transceivers can be standalone units, or incorporated into a circuit board within a computer. They are usually used to connect media of different types, for example, thick coaxial cable to an AUI.
See also 10BASE5, AUI, coaxial cable, collision, Ethernet, LAN, network, traffic.
traffic
Movement of data packets on a network.
See also network, packet.
twisted pair (TP)
A pair of thin wires commonly used for telephone wiring and computer networks. The wires are twisted around each other to minimize interference from other cables.
The two major types of twisted pair are shielded twisted pair (STP) and unshielded twisted pair (UTP). UTP is popular because it is thinner and doesn’t take up much room, but the former (STP) has added protection against electromagnetic interference.
See also bandwidth, Category 3 cabling, Category 5 cabling, coaxial cable, fibre-optic cable, network, STP, UTP.
unicast
A message sent to an individual node on a network.
See also broadcast, multicast, network, node.
An operating system developed at Bell Laboratories in 1969. UNIX is an operating system which can run on a wide variety of hardware.
unmanaged device
Unmanaged devices are those that do not support network management.
See also network management, OfficeConnect®.
Unshielded Twisted Pair. Cabling consisting of one or more pairs of wires used in a variety of network applications that are bound in plastic. UTP is popular because it is very pliable and does not take up as much room as STP and other cables.
See also network, STP, twisted pair.
Wide Area Network. to follow.
See also LAN, network.
See WWW.
wire speed
Wire speed refers to the maximum capacity of a connection. For Ethernet and Fast Ethernet connections this is normally defined by the maximum rate of packets that can be transmitted over a connection. Ethernet wire speed is 14,880 packets per second and Fast Ethernet wire speed is 148,809 packets per second.
See also bit, Ethernet, Fast Ethernet, packet.
World Wide Web (or Web) is an Internet service that allows easy access to information on servers around the world. Web browsers such as Netscape Navigator™ and Internet Explorer allow users to “browse the Web” in order to access this information. WWW documents are structured using HTML (HyperText Mark-up Language) and can incorporate many software applications.
See also Internet, server.
XNS
Xerox Network Services. An early networking protocol developed by Xerox, that allows users (for example, someone working on a PC) to use files that are on another computer.
See also network, PC, protocol.