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.same channel at the same time; also referredto as full duplex.Half-duplex channels canDDE has largely been superseded by Objecttransmit only or receive only.Linking and Embedding (OLE).See also communications parameters.See also Object Linking and Embedding.123Copyright © 2000 SYBEX Inc., Alameda, CA.www.sybex.com 2461book Page 124 Thursday, May 4, 2000 11:59 AMdynamic diskdynamic disk In Microsoft Windows Dynamic Link Library Abbreviated2000, a hard disk that is available only to DLL.A program module that contains ex-Windows 2000 and not available from any ecutable code and data that can be used byother operating system.A dynamic disk applications, or even by other DLLs, in per-does not use primary and extended parti- forming a specific task.tions to divide the available space into log-DLLs are used extensively throughout theical units.family of Microsoft Windows products.DLLs may have filename extensions ofTo create a dynamic disk, use the Disk.DLL,.DRV, or.FON.Management utility to convert a basic diskinto a dynamic disk.Dynamic disks allowThe DLL is linked into the application onlyyou to create, delete, and extend fault-tol-when the program runs, and it is unloadederant and multidisk volumes without re-again when no longer needed.If two DLLstarting the operating system.Windowsapplications are running at the same time2000 RAID (redundant array of inexpen-and both perform a particular function, onlysive disks) services are available only on dy-one copy of the code for that function isnamic disks.loaded, for more efficient use of limitedmemory.Another benefit of using dynamicSee also basic disk.linking is that the.EXE files are not as largeas they would be, because frequently usedDynamic DNS Abbreviated DDNS.Inroutines can be put into a DLL rather thanMicrosoft Windows 2000 Server, a mecha-repeated in each.EXE file that uses them.Anism that allows Dynamic Host Configura-smaller.EXE file means saved disk space andtion Protocol (DHCP) and Windows 2000faster program loading.clients to update Domain Name Service(DNS) records dynamically, rather than bydynamic RAM Abbreviated DRAM,the traditional method of manually addingpronounced dee-ram. A common type ofthe new records to static DNS zone files.computer memory that uses capacitors andtransistors storing electrical charges to rep-See also Domain Name Service.resent memory states.These capacitors losetheir electrical charge, so they need to be re-Dynamic Host Configuration Protocolfreshed every millisecond, during whichAbbreviated DHCP.A system based on net-time they cannot be read by the processor.work interface card addresses that is used toDRAM chips are small, simple, cheap, easyallocate IP addresses and other configura-to make, and hold approximately fourtion information automatically for net-times as much information as a static RAMworked systems.DHCP is an update of the(SRAM) chip of similar complexity.How-Bootstrap Protocol.ever, they are slower than SRAM.See also Bootstrap Protocol; hardware ad-dress; IP address; Transmission Control dynamic routing A routing techniqueProtocol/Internet Protocol.that allows the route that a message takes to124Copyright © 2000 SYBEX Inc., Alameda, CA.www.sybex.com 2461book Page 125 Thursday, May 4, 2000 11:59 AMDynaTextchange, as the message is in transit through Dynamic volumes can include simple,the network, in response to changing net- striped, spanned, and RAID-5 componentsand can exist only on dynamic disks.work conditions.Conditions forcing a routechange might include unusually heavy trafficSee also basic disk; dynamic disk.on a particular section of the network or aDynaText A form of electronic docu-cable failure.Also known as dynamic adap-ment and viewer used in Novell NetWaretive routing.for online manuals.You can use DynaTextdynamic volume In Microsoft Win- directly from the CD, or you can install it ondows 2000, a logical hard disk volume cre- the server or on a workstation.Replacesated by Disk Management.Electrotext.125Copyright © 2000 SYBEX Inc., Alameda, CA.www.sybex.com 2461book Page 126 Thursday, May 4, 2000 11:59 AMEEE See exa-.EB See exabyte.E1 A point-to-point, dedicated, EBCDIC See Extended Binary Coded2.048Mbps communications circuit capa- Decimal Interchange Code.ble of supporting thirty-two 64Kbps chan-echo 1.A transmitted signal that is re-nels used as 30 voice channels, 1 controlflected back to the sender strongly enough sochannel, and 1 synchronization and fram-that it can be distinguished from the originaling channel.The European equivalent ofsignal; often encountered on long-distanceNorth America s T1.telephone lines and satellite links.E1 circuits carry more channels than the 242.A form of repetition, used as a mecha-channels used in T1 systems, and repeatersnism in testing network nodes, in whichare required every 6000 feet when coppereach receiving station on the network ech-wire is used.oes a message back to the main server orE2 A European point-to-point, dedicat- host computer.ed, 8.848Mbps communications circuitecho cancellation A mechanism used toequivalent to four E1 circuits.E2 is the Eu-control echoes on communications linksropean equivalent of North America s T2such as satellite links.and is rarely used.The modem checks for a delayed duplica-E3 A European point-to-point, dedicated,tion of the original signal and adds a re-34.368Mbps communications circuitversed version of this transmission to theequivalent to 16 E1 circuits.The Europeanchannel on which it receives information.equivalent of North America s T3.This process effectively removes the echowithout affecting the incoming signal.E4 A European point-to-point, dedicated,139
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