ATM

Asynchronous Transfer Mode. International standard for cell relay in which multiple service types (such as voice, video, or, data)

 or conveyed  in fixed length (53 byte) cells. Fixed length cells allow cell processing to occur in hardware, thereby reducing delay. ATM is designed to take advantage of high-speed transmission media.

Bridge

A device that connects and passes packets between two network segments that use the same communications protocol.

Bridges operate at the data link layer (Layer 2) of the OSI reference model.

Broadcast Domain

The set of all devices that will receive broadcast frames originating from any device within the set. Broadcast domains can be

bounded by VLANs in a stand-alone environment. In an internetworking environment, they are typically bounded by routers because routers do not forward broadcast frames.

Ethernet

Baseband LAN specification invented by Xerox Corporation and developed jointly by Xerox, Intel, and Digital Equipment Corporation. Ethernet networks use CSMA/CD and run over a variety of cable types at 10 Mbps. Ethernet is similar to the IEEE 802.3 series of standards.

Frame

The logical grouping of information sent as a data link layer unit over a transmission medium. Often refers to the header and trailer, used for synchronization and error control, which surround the user data contained in the unit.

Hub

Generally, a device that serves as the center of a star-topology shared network. Also describes a hardware or software device that contains multiple independent but connected modules of network and internet work equipment.

IEEE

Institute of Electrical and Electronics Engineers. The IEEE is a professional organization whose activities include the development of communications and network standards. IEEE LAN standards are the predominant LAN standards today.

IP

Internet Protocol. Network layer protocol in the TCP/IP stack offering a connectionless inter-network service. IP provides features for addressing, type-of-service specification, security, and fragmentation and reassembly.

IP Address

32-bit address assigned to hosts using TCP/IP. An IP address belongs to one of five classes (A, B, C, D, or E) and is written as four octets separated by periods (dotted decimal format). Each address consists of a network number, an optional sub-network number, and a host number. The network and sub-network numbers together are used for routing, while the host number is used to address an individual host within the network or sub-network. A subnet mask is used to extract network and sub-network information from the IP address.

LAN

Local-Area Network. High-speed, low-error data network covering a relatively small geographic area (up to a few thousand meters). LANs connect workstations, peripherals, terminals, and other devices in a single building or other geographically limited area. LAN standards specify cabling and signaling at the physical and data link layers of the OSI model. Ethernet, FDDI, and Token Ring are widely used LAN technologies.

Latency

Delay between the time a device requests access to a network and the time it is granted permission to transmit. It is also the delay between the time when a device receives a frame and the time that frame is forwarded out the destination port.

Packet

A logical grouping of information that includes a header containing control information and (usually) user data, packets are most often used to refer to network layer units of data.

Router

Network layer device that uses one or more metrics to determine the optimal path along which network traffic should be forwarded. Routers forward packets from one network to another based on network layer information. Occasionally called a gateway (although this definition of gateway is becoming increasingly outdated).

Subnet

Sub-network. In IP networks, a network sharing a particular subnet address. Sub-networks are networks arbitrarily segmented by a network administrator in order to provide a multilevel, hierarchical routing structure while shielding the subnetwork from the addressing complexity of attached networks.

Switch

A network device that filters, forwards, and floods frames based on the destination address of each frame. The switch operates at the data link layer of the OSI model.