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A B C D E F G H I J K L M N O P Q R S T U V W X Y Z 5-4-3 Rule Restriction on coax Ethernet stating that a packet from a device can traverse at most five segments, four repeaters, and across three segments containing stations. 10BASE2 10Mbps baseband Ethernet over cheapernet or thin coaxial cable. 10BASE5 10Mbps baseband Ethernet over thick coaxial cable. 10BASE-T A baseband 10Mbps Ethernet over two pairs of Category 3 or better unshielded twisted-pair cabling. 100BASE-FX A baseband 100Mbps Ethernet over fiber optic cable. 100BASE-T General term for 100Mbps Ethernet over twisted-pair cable. 100BASE-TX 100Mbps Ethernet over two pairs of Category 5 unshielded twisted pair or shielded twisted-pair. 1000BASE-CX Baseband Gigabit Ethernet over of four pairs of category 5 or better. 1000BASE-LX Baseband Gigabit Ethernet using long-wavelength laser devices over single-mode fiber. 1000BASE-SX Baseband Gigabit Ethernet using short-wavelength laser devices over multimode mode fiber. 1000BASE-T Gigabit Ethernet over Category 5 unshielded twisted-pair copper cabling.
Application-Specific Integrated Circuit (ASIC) Chip A processing chip that contains program logic implemented as hardware. Asynchronous Transfer Mode (ATM) A method of transmitting information that is organized into cells. Also, a virtual circuit service based on ATM technology. Attachment Unit Interface (AUI) For 10Mbps Ethernet, the interface between communications electronics in a station and a transceiver. This can be implemented as a cable or as an internal interface within a NIC. Attenuation The loss of signal strength that occurs as information traverses a medium. Attenuation is expressed in decibels. Auto-Negotiation A protocol that enables Ethernet systems at the end of a twisted-pair or optical fiber segment to negotiate configuration parameters such as speed, half or full-duplex mode, and use of flow control.
Baseband Communication via pulses impressed on a medium. Only one signal can be on the medium. Bayonet Neil-Concelman (BNC) A type of connector used for thinnet Ethernet. Broadcast The act of sending a frame addressed to all stations. Buffer A unit of memory, used for the temporary storage of data. Bus A network topology that connects devices via a shared cable. Byte An 8-bit unit of data.
Carrier Sense Multiple Access with Collision Detection (CSMA/CD) The protocol used for classical Ethernet. A station waits until the communication channel is free before transmitting. If two stations transmit concurrently, a collision occurs, and each station pauses before retransmitting. See backoff. Chassis An enclosure that contains slots for network modules chosen for a specific application. Cladding A cylinder of glass that surrounds the core of a fiber optic cable. Coaxial cable segment A single cable section or two or more sections joined by connectors, terminated at each end. Collision domain A set of Ethernet segments connected by repeaters. If two devices on the domain transmit at the same time, a collision will occur. Cross-connect A physical connection between path panels or punch-down blocks. Crossover cable A cable whose wires cross so that the transmit pit in at one end is connected to receive pin at the other end. Crosstalk A signal induced on a wire by a signal on neighboring wire. Cut-through-switch When a switch that starts to transmit a frame before it has received the entire packet.
Data Circuit-terminating Equipment (DCE) Equipment that connects data terminal equipment to the network. Data link layer The layer above the physical layer, in which 0s and 1s are organized into packets. Date Terminal Equipment (DTE) A communicating system that can be the source or destination of data. Desktop Switch A switch that connects directly to end user devices. The switch usually has an uplink port for connection back to a workgroup or backbone switch. Device driver A software program that controls a device used in a computer, such as a printer, CD-ROM, monitor display, or network interface card.
Ethernet The name for a family of LAN technologies standardized by the IEEE 802.3 committee. Extension bits For half-duplex Gigabit Ethernet, nondata symbols added to the end of frames that are less than 512 bytes in length.
Far End Crosstalk (FEXT) The distortion of an outgoing signal by an incoming signal on an adjacent wire, measured in decibels. Fast Ethernet A nickname for the 100Mbps version of Ethernet. FCS field A field at the end of a frame that contains the result of a calculation (called a cyclic redundancy check, or CRC) performed on the remaining bits of the frame. Fiber Optic Inter-Repeater Link (FOIRL) An early implementation of 10Mbps Ethernet across fiber optic link between two repeaters. Filtering database, or Filtering Table A data structure in a switch that maps the Destination Address found in the packet, to a port on the switch. When VLANs are enabled the switch's data structure uses the Destination Address and the VLAN information. Flooding Action by a switch that does not know the ports destination MAC address found in the . The switch transmits the broadcast packet through all ports except for the one on which it arrived. Flow Control Flow control is the management of data flow between computers or devices or between nodes in a network so that the data can be handled at an efficient pace. Too much data arriving before a device can handle it causes data overflow, meaning the data is either lost or must be retransmitted. Full-duplex A mode of operation that enables a pair of systems connected by a link to transmit frames to one another at the same time.
Gigabit Ethernet 1000Mbps Ethernet. It currently is implemented in full-duplex mode only. Gigabit Interface Converter (GBIC) A transceiver used to connect Gigabit Ethernet port to a specific medium. Gigabit Media Independent Interface (GMII) A GIGABIT Ethernet adapter interface to which different types of GBIC transceivers can be attached. This provides choice in the media to which a system can connect. GVRP With GVRP, a switch can exchange VLAN configuration information with other GVRP switches, prune unnecessary broadcast and unknown unicast traffic, and dynamically create and manage VLANs on switches connected through 802.1Q trunk ports.
Half-duplex A mode of operation that allows only a single station to successfully transmit a frame at a given time. Hertz (HZ) Electrical wave frequency in cycles per second. One hertz(Hz) equals one cycle per second. Hub A repeater used in star-wired topology.
IGMP The Internet Group Management Protocol (IGMP) is an Internet protocol that provides a way for an Internet computer to report its multicast group membership to adjacent routers. Multicasting allows one computer on the Internet to send content to multiple other computers that have identified themselves as interested in receiving the originating computer's content. Multicasting can be used for such applications as updating the address books of mobile computer users in the field, sending out company newsletters to a distribution list, and "broadcasting" high-bandwidth programs of streaming media to an audience that has "tuned in" by setting up a multicast group membership. IGMP snooping Eavesdropping on IGMP messages by switches to identify the ports that lead to members of a multicast group. Impedance A measure (in ohms) of the opposition of a to the flow of electricity down the wire. Internet Engineering Task Force (IETF) A group responsible for defining and implementing the TCP/IP suite of protocols that is used on the Internet. Internet Protocol (IP) The layer 3 IETF protocol that routes traffic from it's source to its destination. Interframe gap (Also called the Interpacket gap) The gap required between the end of an Ethernet frame and the start of transmitting the next frame. For example, for Ethernet, the interframe gap is 96 bit times. Invalid frame A frame that does not contain an integral number of bytes and it is too short or too long or carries an invalid CRC value.
Jabber A condition wherein a station transmits for a period of time longer than the maximum permissible frame length. It usually signals a problem on the network. Jam bits In Ethernet, a series of 32 randomly selected bits that are sent after a transmitter detects a collision to assure that all stations hear the collision. Jumbo frame "Jumbo frames" extend ethernet packet size from 1500 to 9000 bytes.
Layer 2 Switch Network device that functions as multi-port switch. Layer 3 Switch Network device that functions as a router and a multi-port switch. Layer 4 Switch A switch that makes forwarding decisions taking Layer 4 protocol information into account. Light emitting diode (LED) A device used to transmit signals across multimode fiber optic cable. Link Aggregation The ability to combine multiple ports on a switch together to increase bandwidth and/or auto-failover. Link integrity test signal A periodic pulse sent across twisted-pair cable to test the cable when the data transmitter is idle. Local Area Network (LAN) A network that connects a set of computers so that they can communicate with each other directly. Logical Link Control (LLC) header A header that contains a source and destination service point addresses and a control field. LocalTalkTM An Apple Computer-proprietary LAN technology with access control at a data rate of 230kb/s.
MAC address A bit string that uniquely identifies a device in transmitted packets. It is 48 bits in length used by devices on the LAN to indicate source and destination addresses. Management Information Based (MIB) A collection of SNMP network management variables. Media Converter A device that connects segments for two different media (such as twisted-pair to fiber optic cabling) making the two segments behave like one extended segment. Medium Dependent Interface (MDI) Port A port that transmits and receives via the standard pin connections. Computer adapters or transceivers have MDI ports. Medium Dependent Interface Crossover (MDI-X) Port A hub port that reverses the role of the send and receive pins, allowing a straight-through cable to be used between the port and a station. Medium Independent Interface (MII) A 100Mbps adapter interface to which different types of transceivers can be attached. This provides choice in the media to which a system can connect. Medium Attachment Unit (MAU) A transceiver that is used to connect a repeater or data terminal equipment (DTE) to a transmission medium. Medium The material on which the data maybe transmitted. STP, UTP, and optical fibers are examples of media. MIB Management information base (MIB) is a formal description of a set of network objects that can be managed using the Simple Network Management Protocol (SNMP). The format of the MIB is defined as part of the SNMP. (All other MIBs are extensions of this basic management information base.) MIB-I refers to the initial MIB definition; MIB-II refers to the current definition. SNMPv2 includes MIB-II and adds some new objects. Modal dispersion Dispersion of the arrival times of rays emitted into a multimode fiber. A large dispersion makes it possible for the receiver to interpret incoming signals correctly. Multicast Multicast is communication between a single sender and multiple receivers on a network. This data is exchanged using Bridge Protocol Data Units (BPDUs). Multicast address An address used to identify a group of systems to which frames will be forwarded. Multimode fiber Optical fiber cable with a relatively wide core (62.5 or 50 microns) that allows multiple rays of light to follow different paths through the core.
Network A set of devices and communication links that allow computers to intercommunicate. Network diameter For a collision domain, the length of the longest path between two points. Non-blocking A switch that is capable of processing traffic at the maximum frame and data arrival rates without having to drop data. Normal link pulse (NLP) The periodic pulse used for a link integrity test by signal which checks whether the link is working.
Optical Time-Domain Reflectometer (OTDR) An optical fiber test tool that locates fiber faults. Organizationally Unique Identifier (OUI) A 3-byte code assigned by the IEEE, usually for use as a MAC address prefix.
Packet A generic term used for a Layer 2 frame or a Layer 3 protocol data unit. Patch cord A short, flexible cable terminated with connectors. Patch panel A cross-connect designed to accommodate the use of patch cords. It facilitates administration of moves and changes. Physical layer (PHY) The layer interfaces with the transmission medium and transmits and receives bits. Port-based VLAN A VLAN defined by a list of switch ports. All systems reached through those parts belong to the same VLAN. Punch-down block A twisted-pair wiring panel for which each wire is placed in a pin and then punched into place, stripping the insulation and making a connection to the process.
QoS Quality of Service (QoS) is the idea that transmission rates, error rates, and other characteristics can be measured, improved, and, to some extent, guaranteed in advance. QoS is of particular concern for the continuous transmission of high-bandwidth video and multimedia information.
Remote monitoring Standards that enable an SNMP network management station to interwork with a network-monitoring component in a system. Repeater A physical-layer device that accepts signals from one cable segment. (Also called a hub). RMON RMON (Remote Network Monitoring) provides standard information that a network administrator can use to monitor, analyze, and troubleshoot a group of distributed local area networks (LANs) and interconnecting T-1/E-1 and T-2/E-3 lines from a central site. RMON specifically defines the information that any network monitoring system will be able to provide. It's specified as part of the Management Information Base (MIB) in Request for Comments 1757 as an extension of the Simple Network Management Protocol (SNMP). The latest level is RMON Version 2 (sometimes referred to as "RMON 2" or "RMON2"). RMON collects nine kinds of information, including packets sent, bytes sent, packets dropped, statistics by host, by conversations between two sets of addresses, and certain kinds of events that have occurred. A network administrator can find out how much bandwidth or traffic each user is imposing on the network and what websites are being accessed. Alarms can be set in order to be aware of impending problems. Router A device that forwards Layer 3 protocol data units or packets. A router can interconnect multiple local area networks and WAN links with one another. Also called a Layer 3 switch. Routing Information Protocol (RIP) A networking routing protocol. Routing protocol A network protocol that enables routers to exchange information used to build their routing tables.
Segment A copper or optical fiber between two devices. Device types include DTE's, repeaters, switches, and routers. Single-Mode Fiber An optical fiber with a narrow core (8 to 9 microns) that allows light to travel along, only one path. Slot time The minimum number of bit times in a valid half-duplex Ethernet transmission. It is 512 bit times for transmission rates up to 100Mbps, and 4096 bit times for 1000Mbps Ethernet. SNMP agent Software component in a managed device that participates in SNMP. SNMP manager Software component in a network management station that reads or updates management variables at a remote device by sending requests to the device's SNMP agent. Spanning Tree Protocol Spanning tree is a protocol that allows the bridges to exchange information so that only one of them will handle a given message that is being sent between two computers within the network. The spanning tree protocol prevents the condition known as a bridge loop. The spanning tree algorithm determines the network which computer hosts are in. Square corner (SC) A popular type of fiber optic connector. Station A device attached to a LAN that is capable of transmitting and receiving data. Straight tip (ST) A type of fiber optic connector. Switch A LAN device that operators at Layer (the data link layer). A switch interconnects two or more LAN segments and selectively forwards LAN frames between segments. Switch identifier The combination of an assigned port priority and the port number. Switch Protocol Data Unit (BPDU) messages Spanning Tree Protocol messages that enable switchs to agree on an initial tree-shaped topology and, after the failure of some component, change the topology to repair broken paths.
Tagged frame A packet that contains a header that carries a VLAN identifier and a priority value. Also called a VLAN tagged packet. Transceiver A hardware component that transmits signals onto a medium and receives them from the medium. Also called medium attachment unit (MAU). Trap A message that an SNMP agent sends to report a significant event (such as reboot or a serious error that occurs at a device). Trunking The capability to combine a group of ports on a switch so that they behave like a single link. Tunneling Encapsulating one type of packet inside the data field of another packet. Twisted-pair link A twisted-pair cable including the connected hardware.
Universally administered MAC address An address assigned to a network interface card by a manufacturer that has obtained a block of unique identifiers from the IEEE. Unshielded twisted-pair cable (UTP) A cable in which wires are paired and twisted around each other. Usually four pairs are bundled into a single cable. The cables are grade by categories ranging from 1 to 7.
Virtual LAN (VLAN) A group of systems (such as the computers in a work group) that need to communicate with one another, and protocols that restrict the delivery of virtual LAN frames to members of the VLAN. VLAN switch A switch that is capable of participating in VLAN protocols. VLAN trunk A link that carries traffic between a pair of VLAN switches. It can carry traffic for multiple VLAN's.
Wave Division Multiplexing (WDM) WDM conversion modules have one strand of single mode fiber coming into them. They transmit and receive on the same fiber strand. The MIL-RC3xW13 transmits at 1310 nm and receives at 1550 nm. The MIL-RC3xW15 transmits at 1550 nm, and receives at 1310 nm wavelengths. One of each is required at opposite ends of the fiber to work properly. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
