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Wild Packets - Networking terms Category: Agriculture and Industry > Networking terms Date & country: 24/02/2017, USA Words: 1152

Dot Address
Refers to the common notation for IP addresses in the form <n.n.n.n> where each number n represents, in decimal, 1 byte of the 4-byte IP address. Also called dotted notation or four-part dotted notation.

Download
The transfer of a file from a remote computer to a local computer.

Downsizing
The transfer of computing tasks previously performed by main frame or minicomputers to personal computers.

Downtime
1. A temporary interruption in the usability of a computer system.2. A work stoppage caused by the temporary lack of usability of acomputer system.

DQDB
Distributed Queue Dual Bus. Data link layer communication protocol, specified in the IEEE802.6 standard, designed for use in MANs. DQDB, which permits multiple systems to interconnect using two unidirectional logical buses, is an open standard that is designed for compatibility with carrier transmission standards and is aligned with emerging standards for BISDN. SIP (SMDS Interface Protocol) is based on DQDB. See also MAN.

DRAM
Dynamic random-access memory. RAM that stores information in capacitors that must be periodically refreshed. Delays can occur because DRAMs are inaccessible to the processor when refreshing their contents. However, DRAMs are less complex and have greater capacity than SRAMs. See also SRAM.

Drive
A data storage device.

Drop
Point on a multipoint channel where a connection to a networked device is made.

Drop Cable
Generally, a cable that connects a network device (such as a computer) to a physical medium. A type of AUI. See also AUI.

DS-0
Digital signal level 0. Framing specification used in transmitting digital signals over a single channel at 64-kbps on a T1 facility. Compare with DS-1 and DS-3.

DS-1
Digital signal level 1. Framing specification used in transmitting digital signals at 1.544-Mbps on a T1 facility (in the United States) or at 2.108-Mbps on an E1 facility (in Europe). Compare with DS-0 and DS-3.

DS-1/DTI
DS-1 domestic trunk interface. Interface circuit used for DS-1 applications with 24 trunks.

DS-3
Digital signal level 3. Framing specification used for transmitting digital signals at 44.736-Mbps on a T3 facility. Compare with DS-0 and DS-1. See also E3 and T3.

DSAP
Destination service access point. The SAP of the network node designated in the Destination field of a packet. Compare to SSAP. See also SAP (service access point).

DSP
Domain specific part. The part of a CLNS address that contains an area identifier, a station identifier, and a selector byte.

DSPU
Downstream physical unit. In SNA, a PU that is located downstream from the host.

DSR
Data set ready. EIA/TIA-232 interface circuit that is activated when DCE is powered up and ready for use.

DSU
Data service unit. Device used in digital transmission that adapts the physical interface on a DTE device to a transmission facility such as T1 or E1. The DSU is also responsible for functions such as signal timing. Often referred to together with CSU, as CSU/DSU. See also CSU.

DSX-1
Cross-connection point for DS-1 signals.

DTE
Data Terminal Equipment. The X.25 term for an end node. Device at the user end of a user-network interface that serves as a data source, destination, or both. DTE connects to a data network through a DCE device (for example, a modem) and typically uses clocking signals generated by the DCE. CTE includes devices such as computers, protocol translators, and multiplexers. Compare with DCE.

DTMF
Dual tone multifrequency. Use of two simultaneous voice-band tones for dialing (such as touch tone).

DTR
Data terminal ready. EIA/TIA 232 circuit that is activated to let the DCE know when the DTE is ready to send and receive data.

DTS
Distributed Time Service.

DUAL
Diffusing Update Algorithm. Convergence algorithm used in Enhanced IGRP that provides loop-free operation at every instant throughout a route computation. Allows routers involved in a topology change to synchronize at the same time, while not involving routers that are unaffected by the change. See also Enhanced IGRP.

Dual Counter-rotation Ring
Network topology in which two signal paths, whose directions are opposite one another, exist in a token-passing network. FDDI and CDDI are based on this concept.

Dual Homing
Network topology in which a device is connected to the network by way of two independent access points (points of attachment). One access point is the primary connection, and the other is a standby connection that is activated in the event of a failure of the primary connection.

Dual-homed Station
Device attached to multiple FDDI rings to provide redundancy.

DVMRP
Distance Vector Multicast Routing Protocol. Internetwork gateway protocol, largely based on RIP, that implements a typical dense mode IP multicast scheme. DVMRP uses IGMP to exchange routing datagrams with its neighbors. See also IGMP.

DXI
Data Exchange Interface. ATM Forum specification, described in RFC 1483, that defines how a network device such as a bridge, router, or hub can effectively act as an FEP to an ATM network by interfacing with a special DSU that performs packet segmentation and reassembly.

Dynamic Address Resolution
Use of an address resolution protocol to determine and store address information on demand.

Dynamic Addressing
A system of addressing in which the computer selects it s own address without the user's intervention.

Dynamic Routing
Routing that adjusts automatically to network topology or traffic changes. Also called adaptive routing.

Early Token Release
Technique used in Token Ring networks that allows a station to release a new token onto the ring immediately after transmitting, instead of waiting for the first frame to return. This feature can increase the total bandwidth on the ring. See also Token Ring.

EARN
European Academic Research Network. European network connecting universities and research institutes. EARN merged with RARE to form TERENA. See also RARE and TERENA.

EBCDIC
Extended binary code decimal interchange code. Any of a number of coded character sets developed by IBM consisting of 8-bit coded characters. This character code is used by older IBM systems and telex machines. Compare with ASCII.

Echo
1. In electronic signaling, the reflection of a signal caused by asudden change in the impedance of the carrier. 2. A networkcontinuity test where packets are sent to a distant node that isobligated to immediately send the packets back.

Echo Protocol
In the AppleTalk protocol family, a protocol that allows a computer to return test packets. The purpose of Echo Protocol is t testthe delivery conditions to a remote node, including reachability,reliability and round trip time.

Echo Test
A diagnostic test in which packets are sent by one node to another

Echoplex
Mode in which keyboard characters are echoed on a terminal screen upon return of a signal from the other end of the line indicating that the characters were received correctly.

ECMA
European Computer Manufacturers Association. Group of European computer vendors who have done substantial OSI standardization work.

EDI
Electronic Document (or Data) Interchange. The term EDI usuallyconnotes a system where authentication and security methodsguarantee the integrity and origin of the information.

EDIFACT
Electronic Data Interchange for Administration, Commerce, and Transport. Data exchange standard administered by the United Nations to be a multi-industry EDI standard.

EEPROM
Electrically erasable programmable read-only memory. EPROM that can be erased using electrical signals applied to specific pins. See also EPROM.

EGP
Exterior Gateway Protocol. Internet protocol for exchanging routing information between autonomous systems. Documented in RFC 904. Not to be confused with the general term exterior gateway protocol. EGP is an obsolete protocol that has been replaced by BGP. See also BGP.

EIA
Electronic Industries Association. Group that specifies electrical transmission standards. The EIA and TIA have developed numerous well-known communications standards, including EIA/TIA-232 and EIA/TIA-449. See also TIA.

EIA/TIA-232
Common physical layer interface standard developed by EIA and TIA, that supports unbalanced circuits at signal speeds of up to 64 kbps. Closely resembles the V.24 specification. Formerly known as RS-232.

EIA/TIA-449
Popular physical layer interface developed by EIA and TIA. Essentially, a faster (up to 2Mbps) version of EIA/TIA-232 capable of longer cable runs. Formerly called RS-449. See also EIA-530.

EIA/TIA-586
Standard that describes the characteristics and applications for various grades of UTP cabling. See also Category 1 cabling, Category 2 cabling, Category 3 cabling, Category 4 cabling, Category 5 cabling, and UTP.

EIA-530
Refers to two electrical implementations of EIA/TIA-449: RS-422 (for balanced transmission) and RS-423 (for unbalanced transmission). See also -422, RS-423, and EIA/TIA-449.

EISA
Extended Industry-Standard Architecture. 32-bit bus interface used in PCs, PC-based servers, and some Unix workstations and servers. See also ISA.

ELAN
Emulated LAN. ATM network in which an Ethernet or Token Ring LAN is emulated using a client-server model. ELANs are composed of an LEC, an LES, a BUS, and an LECS. Multiple ELANs can exist simultaneously on a single ATM network. ELANs are defined by the LANE specification. See also BUS, LANE, LEC, LECS, and LES.

Electromagnetic
Interference in the integrity of a signal caused by radiation. An

Electronic Mail
Widely used network application in which mail messages are transmitted electronically between end users over various types of networks using various network protocols. Often called email.

EMA
1. Enterprise Management Architecture. Digital Equipment Corporation network management architecture, based on the OSI network management model.

Email
Electronic Mail. A network application that can deliver messagesfrom one computer user to another.

EMI
Electromagnetic interference. Interference by electromagnetic signals that can cause reduced data integrity and increased error rates on transmission channels.

EMIF
ESCON Multiple Image Facility. Mainframe I/O software function that allows one ESCON channel to be shared among multiple logical partitions on the same mainframe. See also ESCON.

EMP
Electromagnetic pulse. Caused by lightning and other high-energy phenomena. Capable of coupling enough energy into unshielded conductors to destroy electronic devices. See also Tempest.

Emulation
A network activity in which a computer acts as if it is another kindof computer or terminal. An example is when a Macintosh useropens a remote terminal session to a VAX, it may run a programthat emulates a DEC VT240 terminal.

Emulation Mode
Function of an NCP that enables it to perform activities equivalent to those performed by a transmission control unit.

EN
End node. APPN end system that implements the PU 2.1, provides end-user services, and supports sessions between local and remote CPs. ENs are not capable of routing traffic and rely on an adjacent NN for APPN services. Compare with NN. See also CP.

Encapsulation
The process of placing one protocol inside of another. Usuallyimplies that the encapsulated protocol was not originally intendedby its designers to be carried by the encapsulating protocol.

Encapsulation Bridging
Carries Ethernet frames from one router to another across disparate media, such as serial and FDDI lines. Contrast with translational bridging.

Encoder
Device that modifies information into the required transmission format.

Encryption
The application of a specific algorithm to data so as to alter the appearance of the data making it incomprehensible to those who are not authorized to see the information. See also decryption.

Enhanced IGRP
Enhanced Interior Gateway Routing Protocol. Advanced version of IGRP developed by Cisco. Provides superior convergence properties and operating efficiency, and combines the advantages of link state protocols with those of distance vector protocols. Compare with IGRP. See also IGP, OSPF, and RIP.

Enterprise network
A networking system that allows communication and resourcesharing among all of a company's business functions andworkers. In some circles, this would even include the company'sbusiness including its suppliers and distributors.

Entity
A hardware (or firmware) device or software process capable ofinitiating or responding to communication. Entities typicallypossess a unique address.

Entropy
1. A measure of the disorder of a system. 2. The thermodynamictendency of a system to reduce its overall energy state by increasing its disorder. Theoretically, an equilibrium is reached where the energy reduction that can be gained by a further increase in entropy is offset by the energy necessary to contain that increase.

EOT
End of Transmission. Generally, a character that signifies the end of a logical group of characters or bits.

EPROM
Erasable programmable read-only memory. Nonvolatile memory chips that are programmed after they are manufactured and, if necessary, can be erased by some means and reprogrammed. Compare with EEPROM and PROM.

Equalization
Technique used to compensate for communications channel distortions.

Error checking
In data transmission, an action where the integrity of data isverified.

Error Control
Technique for detecting and correcting errors in data transmissions.

Error-correcting Code
Code having sufficient intelligence and incorporating sufficient signaling information to enable the detection and correction of many errors at the receiver.

Error-detecting Code
Code that can detect transmission errors through analysis of received data based on the adherence of the data to appropriate structural guidelines.

ES
1. End system. Generally, an end-user device on a network. 2. End system. Nonrouting host or node in an OSI network.

ESCON
Enterprise System Connection. IBM channel architecture that specifies a pair of fiber-optic cables, with either LEDs or lasers as transmitters and a signaling rate of 200 Mbps.

ESCON Channel
IBM channel for attaching mainframes to peripherals such as storage devices, backup units, and network interfaces. This channel incorporates fiber channel technology. The ESCON channel replaces the bus and tag channel. Compare with parallel channel. See also bus and tag channel.

ESD
Electrostatic discharge. Discharge of stored static electricity that can damage electronic equipment and impair electrical circuitry, resulting in complete or intermittent failures.

ESF
Extended Superframe Format. Framing type used on T1 circuits that consists of 24 frames of 192 bits each, with the 193rd bit providing timing and other functions. ESF is an enhanced version of SF. See also SF.

ES-IS
End System-to Intermediate System. OSI protocol that defines how end systems (hosts) announce themselves to intermediate systems (routers). See also IS-IS.

ESnet
Energy Sciences Network. Data communications network managed and funded by the U.S. Department of Energy Office of Energy Research (DOE/OER). Interconnects the DOE to educational institutions and other research facilities.

EtherTalk
1. EtherTalk Link Access Protocol (ELAP), the protocol that placesAppleTalk's DDP formatted packets in Ethernet frames. 2. Theimplementation of AppleTalk using Ethernet as a delivery system.In AppleTalk Phase 1, Ethernet V.2 is used; in Phase 2, 802.3 isused.

ETSI
European Telecommunication Standards Institute. Organization created by the European PTTs and the European Community (EC) to propose telecommunications standards for Europe.

EUnet
European Internet. European commercial Internet service provider. EUnet is designed to provide electronic mail, news and other Internet services to European markets.

Event
Network message indicating operational irregularities in physical elements of a network or a response to the occurrence of a significant task, typically the completion of a request for information. See also alarm and traps.

Excess Rate
Traffic in excess of the insured rate for a given connection. Specifically, the excess rate equals the maximum rate minus the insured rate. Excess traffic is delivered only if network resources are available and can be discarded during periods of congestion. Compare with insured rate and maximum rate.

EXEC
The interactive command process of the Cisco IOS software.

Expansion
The process of running a compressed data set through an algorithm that restores the data set to its original size. Compare with companding and compression.

Expedited Delivery
Option set by a specific protocol layer telling other protocol layers, or the same protocol layer in another device, to handle specific data more rapidly.

Explicit Route
In SNA, a route from a source subarea to a destination subarea, as specified by a list of subarea nodes and transmission groups that connect the two.

Explorer Frame
Frame sent out by a networked device in a SRB environment to determine the optimal route to another networked device.

Explorer Packet
Generated by an end station trying to find its way through a SRB network. Gathers a hop-by-hop description of a path through the network by being marked (updated) by each bridge that it traverses, thereby creating a complete topological map. See also all-routes explorer packet, local explorer packet, and spanning explorer packet.

Extension
A system software addition to the Macintosh OS that extends itfunctionality.

exterior gateway protocol
Any internetwork protocol used to exchange routing information between autonomous systems. Not to be confused with Exterior Gateway Protocol EGP), which is a particular instance of an exterior gateway protocol.

Exterior router
Router connected to an AURP tunnel, responsible for the encapsulation and deencapsulation of AppleTalk packets in a foreign protocol header (for example, IP). See also AURP and AURP tunnel.

Fan-out Unit
Device that allows multiple devices on a network to communicate using a single network attachment.

Fast Ethernet
A 100 MB network using 4 twisted pairs.

Fast Switching
Cisco feature whereby a route cache is used to expedite packet switching through a router. Contrast with slow switching.