This glossary is produced to help you understand the many terms–and in particular the myriad of acronyms–that can be encountered on this topic.<\/p>\n
To keep this document reasonably small we have deliberately omitted common terms. In addition, the definitions have been kept brief. We recommend that you consult the glossaries found in other sources (see below) for more comprehensive definitions.<\/p>\n
You are invited to submit words which you think should be included in future editions.<\/p>\n
Glossary<\/p>\n
abstract syntax: A description of a data structure that is independent of machine-oriented structures and encodings.
\nACSE: Association Control Service Element. The method used in OSI for establishing a call between two applications. Checks the identities and contexts of the application entities, and could apply an authentication security check.<\/p>\n
address mask: A bit mask used to select bits from an Internet address for subnet addressing. The mask is 32 bits long and selects the network portion of the Internet address and one or more bits of the local portion. Sometimes called subnet mask.<\/p>\n
address resolution: A means for mapping Network Layer addresses onto
\nmedia-specific addresses. See ARP.<\/p>\n
ADMD: Administration Management Domain. An X.400 Message Handling
\nSystem public service carrier. Examples: MCImail and ATTmail in the
\nU.S., British Telecom Gold400mail in the U.K. The ADMDs in all
\ncountries worldwide together provide the X.400 backbone. See PRMD.<\/p>\n
agent: In the client-server model, the part of the system that
\nperforms information preparation and exchange on behalf of a client
\nor server application. See NMS, DUA, MTA.<\/p>\n
ANSI: American National Standards Institute. The U.S.
\nstandardization body. ANSI is a member of the International
\nOrganization for Standardization (ISO)<\/p>\n
AOW: Asia and Oceania Workshop. One of the three regional OSI
\nImplementors Workshops, equivalent to OIW and EWOS.<\/p>\n
API: Application Program Interface. A set of calling conventions
\ndefining how a service is invoked through a software package.<\/p>\n
Application Layer: The top-most layer in the OSI Reference Model
\nproviding such communication services as electronic mail and file
\ntransfer.<\/p>\n
ARP: Address Resolution Protocol. The Internet protocol used to
\ndynamically map Internet addresses to physical (hardware) addresses
\non local area networks. Limited to networks that support hardware
\nbroadcast.<\/p>\n
ARPA: Advanced Research Projects Agency. Now called DARPA, the U.S.
\ngovernment agency that funded the ARPANET.<\/p>\n
ARPANET: A packet switched network developed in the early 1970s. The
\n“grandfather” of today’s Internet. ARPANET was decommissioned in
\nJune 1990.<\/p>\n
ASN.1: Abstract Syntax Notation One. The OSI language for describing
\nabstract syntax. See BER.<\/p>\n
attribute: The form of information items provided by the X.500
\nDirectory Service. The directory information base consists of
\nentries, each containing one or more attributes. Each attribute
\nconsists of a type identifier together with one or more values. Each
\ndirectory Read operation can retrieve some or all attributes from a
\ndesignated entry.<\/p>\n
Autonomous System: Internet (TCP\/IP) terminology for a collection of
\ngateways (routers) that fall under one administrative entity and
\ncooperate using a common Interior Gateway Protocol (IGP). See
\nsubnetwork.<\/p>\n
backbone: The primary connectivity mechanism of a hierarchical
\ndistributed system. All systems which have connectivity to an
\nintermediate system on the backbone are assured of connectivity to
\neach other. This does not prevent systems from setting up private
\narrangements with each other to bypass the backbone for reasons of
\ncost, performance, or security.<\/p>\n
Bart Simpson (R): Internet and OSI cult hero.<\/p>\n
baseband: Characteristic of any network technology that uses a single
\ncarrier frequency and requires all stations attached to the network
\nto participate in every transmission. See broadband.<\/p>\n
BER: Basic Encoding Rules. Standard rules for encoding data units
\ndescribed in ASN.1. Sometimes incorrectly lumped under the term
\nASN.1, which properly refers only to the abstract syntax description
\nlanguage, not the encoding technique.<\/p>\n
big-endian: A format for storage or transmission of binary data in
\nwhich the most significant bit (or byte) comes first. The reverse
\nconvention is called little-endian.<\/p>\n
BITNET: Because It’s Time NETwork. An academic computer network
\nbased originally on IBM mainframe systems interconnected via leased
\n9600 bps lines. BITNET has recently merged with CSNET, The
\nComputer+Science Network (another academic computer network) to form
\nCREN: The Corporation for Research and Educational Networking. See
\nCSNET.<\/p>\n
BOC: Bell Operating Company. More commonly referred to as RBOC for
\nRegional Bell Operating Company. The local telephone company in each
\nof the seven U.S. regions.<\/p>\n
bridge: A device that connects two or more physical networks and
\nforwards packets between them. Bridges can usually be made to filter
\npackets, that is, to forward only certain traffic. Related devices
\nare: repeaters which simply forward electrical signals from one cable
\nto another, and full-fledged routers which make routing decisions
\nbased on several criteria. In OSI terminology, a bridge is a Data
\nLink Layer intermediate system. See repeater and router.<\/p>\n
broadband: Characteristic of any network that multiplexes multiple,
\nindependent network carriers onto a single cable. This is usually done using frequency division multiplexing. Broadband technology
\nallows several networks to coexist on one single cable; traffic from
\none network does not interfere with traffic from another since the
\n“conversations” happen on different frequencies in the “ether,”
\nrather like the commercial radio system.<\/p>\n
broadcast: A packet delivery system where a copy of a given packet is
\ngiven to all hosts attached to the network. Example: Ethernet.<\/p>\n
BSD: Berkeley Software Distribution. Term used when describing
\ndifferent versions of the Berkeley UNIX software, as in “4.3BSD
\nUNIX.”<\/p>\n
catenet: A network in which hosts are connected to networks with
\nvarying characteristics, and the networks are interconnected by
\ngateways (routers). The Internet is an example of a catenet. See
\nIONL.<\/p>\n
CCITT: International Consultative Committee for Telegraphy and
\nTelephony. A unit of the International Telecommunications Union
\n(ITU) of the United Nations. An organization with representatives
\nfrom the PTTs of the world. CCITT produces technical standards,
\nknown as “Recommendations,” for all internationally controlled
\naspects of analog and digital communications. See X Recommendations.<\/p>\n
CCR: Commitment, Concurrency, and Recovery. An OSI application
\nservice element used to create atomic operations across distributed
\nsystems. Used primarily to implement two-phase commit for
\ntransactions and nonstop operations.<\/p>\n
client-server model: A common way to describenetwork services and the
\nmodel user processes (programs) of those services. Examples include
\nthe name-server\/name-resolver paradigm of the DNS and file-
\nserver\/file-client relationships such as NFS and diskless hosts.<\/p>\n
CLNP: Connectionless Network Protocol. The OSI protocol for
\nproviding the OSI Connectionless Network Service (datagram service).
\nCLNP is the OSI equivalent to Internet IP, and is sometimes called
\nISO IP.<\/p>\n
CLTP: Connectionless Transport Protocol. Provides for end-to-end
\nTransport data addressing (via Transport selector) and error control
\n(via checksum), but cannot guarantee delivery or provide flow
\ncontrol. The OSI equivalent of UDP.<\/p>\n
CMIP: Common Management Information Protocol. The OSI network
\nmanagement protocol.<\/p>\n
CMOT: CMIP Over TCP. An effort to use the OSI network management
\nprotocol to manage TCP\/IP networks.<\/p>\n
connectionless: The model of interconnection in which communication
\ntakes place without first establishing a connection. Sometimes
\n(imprecisely) called datagram. Examples: LANs, Internet IP and OSI
\nCLNP, UDP, ordinary postcards.<\/p>\n
connection-oriented: The model of interconnection in which
\ncommunication proceeds through three well-defined phases: connection
\nestablishment, data transfer, connection release. Examples: X.25,
\nInternet TCP and OSI TP4, ordinary telephone calls.<\/p>\n
core gateway: Historically, one of a set of gateways (routers)
\noperated by the Internet Network Operations Center at BBN. The core
\ngateway system forms a central part of Internet routing in that all
\ngroups must advertise paths to their networks from a core gateway,
\nusing the Exterior Gateway Protocol (EGP). See EGP, backbone.<\/p>\n
COS: Corporation for Open Systems. A vendor and user group for
\nconformance testing, certification, and promotion of OSI products.<\/p>\n
COSINE: Cooperation for Open Systems Interconnection Networking in
\nEurope. A program sponsored by the European Commission, aimed at
\nusing OSI to tie together European research networks.<\/p>\n
CREN: See BITNET and CSNET.<\/p>\n
CSMA\/CD: Carrier Sense Multiple Access with Collision Detection. The
\naccess method used by local area networking technologies such as
\nEthernet.<\/p>\n
CSNET: Computer+Science Network. A large computer network, mostly in
\nthe U.S. but with international connections. CSNET sites include
\nuniversities, research labs, and some commercial companies. Now
\nmerged with BITNET to form CREN. See BITNET.<\/p>\n
DARPA: Defense Advanced Research Projects Agency. The U.S.
\ngovernment agency that funded the ARPANET.<\/p>\n
Data Link Layer: The OSI layer that is responsible for data transfer
\nacross a single physical connection, or series of bridged
\nconnections, between two Network entities.<\/p>\n
DCA: Defense Communications Agency. The government agency
\nresponsible for the Defense Data Network (DDN).<\/p>\n
DCE: Distributed Computing Environment. An architecture of standard
\nprogramming interfaces, conventions, and server functionalities
\n(e.g., naming, distributed file system, remote procedure call) for
\ndistributing applications transparently across networks of
\nheterogeneous computers. Promoted and controlled by the Open
\nSoftware Foundation (OSF), a consortium led by HP, DEC, and IBM. See
\nONC.<\/p>\n
DDN: Defense Data Network. Comprises the MILNET and several other
\nDoD networks.<\/p>\n
DECnet: Digital Equipment Corporation’s proprietary network
\narchitecture.<\/p>\n
DNS: Domain Name System. The distributed name\/address mechanism used
\nin the Internet.<\/p>\n
domain: In the Internet, a part of a naming hierarchy.
\nSyntactically, an Internet domain name consists of a sequence of
\nnames (labels) separated by periods (dots), e.g., “tundra.mpk.ca.us.”
\nIn OSI, “domain” is generally used as an administrative partition of
\na complex distributed system, as in MHS Private Management Domain
\n(PRMD), and Directory Management Domain (DMD).<\/p>\n
dotted decimal notation: The syntactic representation for a 32-bit
\ninteger that consists of four 8-bit numbers written in base 10 with
\nperiods (dots) separating them. Used to represent IP addresses in
\nthe Internet as in: 192.67.67.20.<\/p>\n
DSA: Directory System Agent. The software that provides the X.500
\nDirectory Service for a portion of the directory information base.
\nGenerally, each DSA is responsible for the directory information for
\na single organization or organizational unit.<\/p>\n
DUA: Directory User Agent. The software that accesses the X.500
\nDirectory Service on behalf of the directory user. The directory
\nuser may be a person or another software element.<\/p>\n
EARN: European Academic Research Network. A network using BITNET
\ntechnology connecting universities and research labs in Europe.<\/p>\n
EGP: Exterior Gateway Protocol. A reachability routing protocol used
\nby gateways in a two-level internet. EGP is used in the Internet
\ncore system. See core gateway.<\/p>\n
encapsulation: The technique used by layered protocols in which a
\nlayer adds header information to the protocol data unit (PDU) from
\nthe layer above. As an example, in Internet terminology, a packet<\/p>\n
would contain a header from the physical layer, followed by a header
\nfrom the network layer (IP), followed by a header from the transport
\nlayer (TCP), followed by the application protocol data.<\/p>\n
end system: An OSI system which contains application processes
\ncapable of communicating through all seven layers of OSI protocols.
\nEquivalent to Internet host.<\/p>\n
entity: OSI terminology for a layer protocol machine. An entity
\nwithin a layer performs the functions of the layer within a single
\ncomputer system, accessing the layer entity below and providing
\nservices to the layer entity above at local service access points.<\/p>\n
ES-IS: End system to Intermediate system protocol. The OSI protocol
\nby which end systems announce themselves to intermediate systems.<\/p>\n
EUnet: European UNIX Network.<\/p>\n
EUUG: European UNIX Users Group.<\/p>\n
EWOS: European Workshop for Open Systems. The OSI Implementors
\nWorkshop for Europe. See OIW.<\/p>\n
FARNET: Federation of American Research NETworks.<\/p>\n
FDDI: Fiber Distributed Data Interface. An emerging high-speed
\nnetworking standard. The underlying medium is fiber optics, and the
\ntopology is a dual-attached, counter-rotating Token Ring. FDDI
\nnetworks can often be spotted by the orange fiber “cable.”<\/p>\n
FIPS: Federal Information Processing Standard.<\/p>\n
flame: To express strong opinion and\/or criticism of something,
\nusually as a frank inflammatory statement in an electronic message.<\/p>\n
FNC: Federal Networking Council. The body responsible for
\ncoordinating networking needs among U.S. Federal agencies.<\/p>\n
fragmentation: The process in which an IP datagram is broken into
\nsmaller pieces to fit the requirements of a given physical network.
\nThe reverse process is termed reassembly. See MTU.<\/p>\n
FRICC: Federal Research Internet Coordinating Committee. Now
\nreplaced by the FNC.<\/p>\n
FTAM: File Transfer, Access, and Management. The OSI remote file
\nservice and protocol.<\/p>\n
FTP: File Transfer Protocol. The Internet protocol (and program)
\nused to transfer files between hosts. See FTAM.<\/p>\n
gateway: The original Internet term for what is now called router or
\nmore precisely, IP router. In modern usage, the terms “gateway” and
\n“application gateway” refer to systems which do translation from some
\nnative format to another. Examples include X.400 to\/from RFC 822
\nelectronic mail gateways. See router.<\/p>\n
GOSIP: Government OSI Profile. A U.S. Government procurement
\nspecification for OSI protocols.<\/p>\n
IAB: Internet Activities Board. The technical body that oversees the
\ndevelopment of the Internet suite of protocols (commonly referred to
\nas “TCP\/IP”). It has two task forces (the IRTF and the IETF) each
\ncharged with investigating a particular area.<\/p>\n
ICMP: Internet Control Message Protocol. The protocol used to handle
\nerrors and control messages at the IP layer. ICMP is actually part
\nof the IP protocol.<\/p>\n
IESG: Internet Engineering Steering Group. The executive committee
\nof the IETF.<\/p>\n
IETF: Internet Engineering Task Force. One of the task forces of the
\nIAB. The IETF is responsible for solving short-term engineering
\nneeds of the Internet. It has over 40 Working Groups.<\/p>\n
IGP: Interior Gateway Protocol. The protocol used to exchange
\nrouting information between collaborating routers in the Internet.
\nRIP and OSPF are examples of IGPs.<\/p>\n
IGRP: Internet Gateway Routing Protocol. A proprietary IGP used by
\ncisco System’s routers.<\/p>\n
INTAP: Interoperability Technology Association for Information
\nProcessing. The technical organization which has the official
\ncharter to develop Japanese OSI profiles and conformance tests.<\/p>\n
intermediate system: An OSI system which is not an end system, but
\nwhich serves instead to relay communications between end systems.
\nSee repeater, bridge, and router.<\/p>\n
internet: A collection of networks interconnected by a set of routers
\nwhich allow them to function as a single, large virtual network.<\/p>\n
Internet: (note the capital “I”) The largest internet in the world
\nconsisting of large national backbone nets (such as MILNET, NSFNET,
\nand CREN) and a myriad of regional and local campus networks all over
\nthe world. The Internet uses the Internet protocol suite. To be on
\nthe Internet you must have IP connectivity, i.e., be able to Telnet
\nto–or ping–other systems. Networks with only e-mail connectivity
\nare not actually classified as being on the Internet.<\/p>\n
Internet address: A 32-bit address assigned to hosts using TCP\/IP.
\nSee dotted decimal notation.<\/p>\n
IONL: Internal Organization of the Network Layer. The OSI standard
\nfor the detailed architecture of the Network Layer. Basically, it
\npartitions the Network layer into subnetworks interconnected by
\nconvergence protocols (equivalent to internetworking protocols),
\ncreating what Internet calls a catenet or internet.<\/p>\n
IP: Internet Protocol. The network layer protocol for the Internet
\nprotocol suite.<\/p>\n
IP datagram: The fundamental unit of information passed across the
\nInternet. Contains source and destination addresses along with data
\nand a number of fields which define such things as the length of the
\ndatagram, the header checksum, and flags to say whether the datagram
\ncan be (or has been) fragmented.<\/p>\n
IRTF: Internet Research Task Force. One of the task forces of the
\nIAB. The group responsible for research and development of the
\nInternet protocol suite.<\/p>\n
ISDN: Integrated Services Digital Network. An emerging technology
\nwhich is beginning to be offered by the telephone carriers of the
\nworld. ISDN combines voice and digital network services in a single
\nmedium making it possible to offer customers digital data services as
\nwell as voice connections through a single “wire.” The standards
\nthat define ISDN are specified by CCITT.<\/p>\n
IS-IS: Intermediate system to Intermediate system protocol. The OSI
\nprotocol by which intermediate systems exchange routing information.<\/p>\n
ISO: International Organization for Standardization. You knew that,
\nright? Best known for the 7-layer OSI Reference Model. See OSI.<\/p>\n
ISODE: ISO Development Environment. A popular implementation of the
\nupper layers of OSI. Pronounced eye-so-dee-eee.<\/p>\n
JANET: Joint Academic Network. A university network in the U.K.<\/p>\n
JUNET: Japan UNIX Network.<\/p>\n
KA9Q: A popular implementation of TCP\/IP and associated protocols for
\namateur packet radio systems.<\/p>\n
Kermit: A popular file transfer and terminal emulation program.<\/p>\n
little-endian: A format for storage or transmission of binary data in
\nwhich the least significant byte (bit) comes first. See big-endian.<\/p>\n
mail exploder: Part of an electronic mail delivery system which
\nallows a message to be delivered to a list of addressees. Mail
\nexploders are used to implement mailing lists. Users send messages
\nto a single address (e.g., hacks@somehost.edu) and the mail exploder
\ntakes care of delivery to the individual mailboxes in the list.<\/p>\n
mail gateway: A machine that connects two or more electronic mail
\nsystems (especially dissimilar mail systems on two different
\nnetworks) and transfers messages between them. Sometimes the mapping
\nand translation can be quite complex, and generally it requires a
\nstore-and-forward scheme whereby the message is received from one
\nsystem completely before it is transmitted to the next system after
\nsuitable translations.<\/p>\n
Martian: Humorous term applied to packets that turn up unexpectedly
\non the wrong network because of bogus routing entries. Also used as
\na name for a packet which has an altogether bogus (non-registered or
\nill-formed) Internet address.<\/p>\n
MHS: Message Handling System. The system of message user agents,
\nmessage transfer agents, message stores, and access units which
\ntogether provide OSI electronic mail. MHS is specified in the CCITT
\nX.400 series of Recommendations.<\/p>\n
MIB: Management Information Base. A collection of objects that can
\nbe accessed via a network management protocol. See SMI.<\/p>\n
MILNET: MILitary NETwork. Originally part of the ARPANET, MILNET was
\npartitioned in 1984 to make it possible for military installations to
\nhave reliable network service, while the ARPANET continued to be used
\nfor research. See DDN.<\/p>\n
MTA: Message Transfer Agent. An OSI application process used to
\nstore and forward messages in the X.400 Message Handling System.
\nEquivalent to Internet mail agent.<\/p>\n
MTU: Maximum Transmission Unit. The largest possible unit of data
\nthat can be sent on a given physical medium. Example: The MTU of
\nEthernet is 1500 bytes. See fragmentation.<\/p>\n
multicast: A special form of broadcast where copies of the packet are
\ndelivered to only a subset of all possible destinations. See
\nbroadcast.<\/p>\n
multi-homed host: A computer connected to more than one physical data
\nlink. The data links may or may not be attached to the same network.<\/p>\n
name resolution: The process of mapping a name into the corresponding
\naddress. See DNS.<\/p>\n
NetBIOS: Network Basic Input Output System. The standard interface
\nto networks on IBM PC and compatible systems.<\/p>\n
Network Address: See Internet address or OSI Network Address.<\/p>\n
Network Layer: The OSI layer that is responsible for routing,
\nswitching, and subnetwork access across the entire OSI environment.<\/p>\n
NFS(R): Network File System. A distributed file system developed by
\nSun Microsystems which allows a set of computers to cooperatively
\naccess each other’s files in a transparent manner.<\/p>\n
NIC: Network Information Center. Originally there was only one,
\nlocated at SRI International and tasked to serve the ARPANET (and
\nlater DDN) community. Today, there are many NICs, operated by local,
\nregional, and national networks all over the world. Such centers
\nprovide user assistance, document service, training, and much more.<\/p>\n
NIST: National Institute of Standards and Technology. (Formerly
\nNBS). See OIW.<\/p>\n
NMS: Network Management Station. The system responsible for managing
\na (portion of a) network. The NMS talks to network management
\nagents, which reside in the managed nodes, via a network management
\nprotocol. See agent.<\/p>\n
NOC: Network Operations Center. Any center tasked with the
\noperational aspects of a production network. These tasks include
\nmonitoring and control, trouble-shooting, user assistance, and so on.<\/p>\n
NSAP: Network Service Access Point. The point at which the OSI
\nNetwork Service is made available to a Transport entity. The NSAPs
\nare identified by OSI Network Addresses.<\/p>\n
NSF: National Science Foundation. Sponsors of the NSFNET.
\nNSFNET: National Science Foundation NETwork. A collection of local,
\nregional, and mid-level networks in the U.S. tied together by a
\nhigh-speed backbone. NSFNET provides scientists access to a number
\nof supercomputers across the country.<\/p>\n
OIW: Workshop for Implementors of OSI. Frequently called NIST OIW or
\nthe NIST Workshop, this is the North American regional forum at which
\nOSI implementation agreements are decided. It is equivalent to EWOS
\nin Europe and AOW in the Pacific.<\/p>\n
ONC(tm): Open Network Computing. A distributed applications
\narchitecture promoted and controlled by a consortium led by Sun
\nMicrosystems.<\/p>\n
OSI: Open Systems Interconnection. An international standardization
\nprogram to facilitate communications among computers from different
\nmanufacturers. See ISO.<\/p>\n
OSI Network Address: The address, consisting of up to 20 octets, used
\nto locate an OSI Transport entity. The address is formatted into an
\nInitial Domain Part which is standardized for each of several
\naddressing domains, and a Domain Specific Part which is the
\nresponsibility of the addressing authority for that domain.<\/p>\n
OSI Presentation Address: The address used to locate an OSI
\nApplication entity. It consists of an OSI Network Address and up to
\nthree selectors, one each for use by the Transport, Session, and
\nPresentation entities.<\/p>\n
OSPF: Open Shortest Path First. A “Proposed Standard” IGP for the
\nInternet. See IGP.<\/p>\n
PCI: Protocol Control Information. The protocol information added by
\nan OSI entity to the service data unit passed down from the layer
\nabove, all together forming a Protocol Data Unit (PDU).<\/p>\n
PDU: Protocol Data Unit. This is OSI terminology for “packet.” A
\nPDU is a data object exchanged by protocol machines (entities) within
\na given layer. PDUs consist of both Protocol Control Information
\n(PCI) and user data.<\/p>\n
Physical Layer: The OSI layer that provides the means to activate and
\nuse physical connections for bit transmission. In plain terms, the
\nPhysical Layer provides the procedures for transferring a single bit
\nacross a Physical Media.<\/p>\n
Physical Media: Any means in the physical world for transferring
\nsignals between OSI systems. Considered to be outside the OSI Model,
\nand therefore sometimes referred to as “Layer 0.” The physical
\nconnector to the media can be considered as defining the bottom
\ninterface of the Physical Layer, i.e., the bottom of the OSI<\/p>\n
Reference Model.<\/p>\n
ping: Packet internet groper. A program used to test reachability of
\ndestinations by sending them an ICMP echo request and waiting for a
\nreply. The term is used as a verb: “Ping host X to see if it is up!”<\/p>\n
port: The abstraction used by Internet transport protocols to
\ndistinguish among multiple simultaneous connections to a single
\ndestination host. See selector.<\/p>\n
POSI: Promoting Conference for OSI. The OSI “800-pound gorilla” in
\nJapan. Consists of executives from the six major Japanese computer
\nmanufacturers and Nippon Telephone and Telegraph. They set policies
\nand commit resources to promote OSI.<\/p>\n
PPP: Point-to-Point Protocol. The successor to SLIP, PPP provides
\nrouter-to-router and host-to-network connections over both
\nsynchronous and asynchronous circuits. See SLIP.<\/p>\n
Presentation Address: See OSI Presentation Address.<\/p>\n
Presentation Layer: The OSI layer that determines how Application
\ninformation is represented (i.e., encoded) while in transit between
\ntwo end systems.<\/p>\n
PRMD: Private Management Domain. An X.400 Message Handling System
\nprivate organization mail system. Example: NASAmail. See ADMD.<\/p>\n
protocol: A formal description of messages to be exchanged and rules
\nto be followed for two or more systems to exchange information.<\/p>\n
proxy: The mechanism whereby one system “fronts for” another system
\nin responding to protocol requests. Proxy systems are used in
\nnetwork management to avoid having to implement full protocol stacks
\nin simple devices, such as modems.<\/p>\n
proxy ARP: The technique in which one machine, usually a router,
\nanswers ARP requests intended for another machine. By “faking” its
\nidentity, the router accepts responsibility for routing packets to
\nthe “real” destination. Proxy ARP allows a site to use a single IP
\naddress with two physical networks. Subnetting would normally be a
\nbetter solution.<\/p>\n
PSN: Packet Switch Node. The modern term used for nodes in the
\nARPANET and MILNET. These used to be called IMPs (Interface Message
\nProcessors). PSNs are currently implemented with BBN C30 or C300
\nminicomputers.<\/p>\n
RARE: Reseaux Associes pour la Recherche Europeenne. European
\nassociation of research networks.<\/p>\n
RARP: Reverse Address Resolution Protocol. The Internet protocol a
\ndiskless host uses to find its Internet address at startup. RARP
\nmaps a physical (hardware) address to an Internet address. See ARP.<\/p>\n
RBOC: Regional Bell Operating Company. See BOC.<\/p>\n
repeater: A device which propagates electrical signals from one cable
\nto another without making routing decisions or providing packet
\nfiltering. In OSI terminology, a repeater is a Physical Layer
\nintermediate system. See bridge and router.<\/p>\n
RFC: Request For Comments. The document series, begun in 1969, which
\ndescribes the Internet suite of protocols and related experiments.
\nNot all (in fact very few) RFCs describe Internet standards, but all
\nInternet standards are written up as RFCs.<\/p>\n
RFS: Remote File System. A distributed file system, similar to NFS,
\ndeveloped by AT&T and distributed with their UNIX System V operating
\nsystem. See NFS.<\/p>\n
RIP: Routing Information Protocol. An Interior Gateway Protocol
\n(IGP) supplied with Berkeley UNIX.<\/p>\n
RIPE: Reseaux IP Europeenne. European continental TCP\/IP network
\noperated by EUnet. See EUnet.<\/p>\n
rlogin: A service offered by Berkeley UNIX which allows users of one
\nmachine to log into other UNIX systems (for which they are
\nauthorized) and interact as if their terminals were connected
\ndirectly. Similar to Telnet.<\/p>\n
ROSE: Remote Operations Service Element. A lightweight RPC protocol,
\nused in OSI Message Handling, Directory, and Network Management
\napplication protocols.<\/p>\n
router: A system responsible for making decisions about which of
\nseveral paths network (or Internet) traffic will follow. To do this
\nit uses a routing protocol to gain information about the network, and
\nalgorithms to choose the best route based on several criteria known
\nas “routing metrics.” In OSI terminology, a router is a Network
\nLayer intermediate system. See gateway, bridge and repeater.<\/p>\n
RPC: Remote Procedure Call. An easy and popular paradigm for
\nimplementing the client-server model of distributed computing. A
\nrequest is sent to a remote system to execute a designated procedure,<\/p>\n
using arguments supplied, and the result returned to the caller.
\nThere are many variations and subtleties, resulting in a variety of
\ndifferent RPC protocols.<\/p>\n
RTSE: Reliable Transfer Service Element. A lightweight OSI
\napplication service used above X.25 networks to handshake application
\nPDUs across the Session Service and TP0. Not needed with TP4, and
\nnot recommended for use in the U.S. except when talking to X.400
\nADMDs.<\/p>\n
SAP: Service Access Point. The point at which the services of an OSI
\nlayer are made available to the next higher layer. The SAP is named
\naccording to the layer providing the services: e.g., Transport
\nservices are provided at a Transport SAP (TSAP) at the top of the
\nTransport Layer.<\/p>\n
selector: The identifier used by an OSI entity to distinguish among
\nmultiple SAPs at which it provides services to the layer above. See
\nport.<\/p>\n
Session Layer: The OSI layer that provides means for dialogue control
\nbetween end systems.<\/p>\n
SGMP: Simple Gateway Management Protocol. The predecessor to SNMP.
\nSee SNMP.<\/p>\n
SLIP: Serial Line IP. An Internet protocol used to run IP over
\nserial lines such as telephone circuits or RS-232 cables
\ninterconnecting two systems. SLIP is now being replaced by PPP. See
\nPPP.<\/p>\n
SMDS: Switched Multimegabit Data Service. An emerging high-speed
\nnetworking technology to be offered by the telephone companies in the
\nU.S.<\/p>\n
SMI: Structure of Management Information. The rules used to define
\nthe objects that can be accessed via a network management protocol.
\nSee MIB.<\/p>\n
SMTP: Simple Mail Transfer Protocol. The Internet electronic mail
\nprotocol. Defined in RFC 821, with associated message format
\ndescriptions in RFC 822.<\/p>\n
SNA: Systems Network Architecture. IBM’s proprietary network
\narchitecture.<\/p>\n
SNMP: Simple Network Management Protocol. The network management
\nprotocol of choice for TCP\/IP-based internets.<\/p>\n
SPAG: Standards Promotion and Application Group. A group of European
\nOSI manufacturers which chooses option subsets and publishes these in
\na “Guide to the Use of Standards” (GUS).<\/p>\n
SQL: Structured Query Language. The international standard language
\nfor defining and accessing relational databases.<\/p>\n
subnet mask: See address mask.<\/p>\n
subnetwork: A collection of OSI end systems and intermediate systems
\nunder the control of a single administrative domain and utilizing a
\nsingle network access protocol. Examples: private X.25 networks,
\ncollection of bridged LANs.<\/p>\n
TCP: Transmission Control Protocol. The major transport protocol in
\nthe Internet suite of protocols providing reliable, connection-
\noriented, full-duplex streams. Uses IP for delivery. See TP4.<\/p>\n
Telnet: The virtual terminal protocol in the Internet suite of
\nprotocols. Allows users of one host to log into a remote host and
\ninteract as normal terminal users of that host.<\/p>\n
three-way-handshake: The process whereby two protocol entities
\nsynchronize during connection establishment.<\/p>\n
TP0: OSI Transport Protocol Class 0 (Simple Class). This is the
\nsimplest OSI Transport Protocol, useful only on top of an X.25
\nnetwork (or other network that does not lose or damage data).<\/p>\n
TP4: OSI Transport Protocol Class 4 (Error Detection and Recovery
\nClass). This is the most powerful OSI Transport Protocol, useful on
\ntop of any type of network. TP4 is the OSI equivalent to TCP.<\/p>\n
transceiver: Transmitter-receiver. The physical device that connects
\na host interface to a local area network, such as Ethernet. Ethernet
\ntransceivers contain electronics that apply signals to the cable and
\nsense collisions.<\/p>\n
Transport Layer: The OSI layer that is responsible for reliable end-
\nto-end data transfer between end systems.<\/p>\n
UA: User Agent. An OSI application process that represents a human
\nuser or organization in the X.400 Message Handling System. Creates,
\nsubmits, and takes delivery of messages on the user’s behalf.<\/p>\n
UDP: User Datagram Protocol. A transport protocol in the Internet
\nsuite of protocols. UDP, like TCP, uses IP for delivery; however,
\nunlike TCP, UDP provides for exchange of datagrams without
\nacknowledgements or guaranteed delivery. See CLTP.<\/p>\n
UUCP: UNIX to UNIX Copy Program. A protocol used for communication
\nbetween consenting UNIX systems.<\/p>\n
XDR: eXternal Data Representation. A standard for machine-
\nindependent data structures developed by Sun Microsystems. Similar
\nto ASN.1.<\/p>\n
X\/Open: A group of computer manufacturers that promotes the
\ndevelopment of portable applications based on UNIX. They publish a
\ndocument called the X\/Open Portability Guide.<\/p>\n
X Recommendations: The CCITT documents that describe data
\ncommunication network standards. Well-known ones include: X.25
\nPacket Switching standard, X.400 Message Handling System, and X.500
\nDirectory Services.<\/p>\n
The X Window System (TM): A popular window system developed by MIT
\nand implemented on a number of workstations.<\/p>\n
………………………………………….<\/p>\n
<\/p>\n
\n\n
- \n
\n
- Application Profile<\/a><\/dt>\n
- The DCMI Abstract Model (DCAM) [1] is a specification which defines an abstract syntax for metadata records that is independent of, but mappable to, a diversity of concrete implementation syntaxes such as HTML\/XHTML, XML, and any of the concrete syntaxes defined for RDF. The DCAM was developed as a basis for defining validatable metadata records, in a variety of popular implementation syntaxes, whose contents could straightforwardly be exposed as RDF triples.<\/dd>\n<\/dl>\n
\n
- Appropriate Literal (archaic<\/i>)<\/dt>\n
- In the late 1990s, when work began on the Resource Description Framework, the notion was introduced that resolvable URIs should be used as metadata values. The notion of “appropriate literal” captured the requirement to present consumers of metadata not just with URIs, but with readable text strings or other appropriate literals, such as dates or classification numbers, for the purpose of resource discovery. The ambiguity of whether Dublin Core properties were intended to be used with strings or URIs as values was not properly addressed until the assignment of domains and ranges<\/a> in 2008.<\/dd>\n<\/dl>\n
\n
- DCMI Abstract Model<\/a><\/dt>\n
- The Dublin Core Abstract Model<\/a> (DCAM) specifies the components and constructs used in Description Sets (metadata records). DCAM provides an information model independent of any particular encoding syntax and a clear mapping to RDF triples. It is designed to be used in conjunction with the Description Set Profile<\/a> constraint language and DCAM-conformant syntax specifications in the construction of application profiles<\/a>. Developed between 2003 and 2008, DCAM was in 2010 the subject of a critical review<\/a>. DCAM and related specifications are not currently the object of further development and testing.<\/dd>\n<\/dl>\n
\n
- DCMI (Dublin Core Metadata Initiative) Ltd<\/dt>\n
- The Dublin Core Metadata Initiative<\/a> (DCMI) is a public, not-for-profit organization, incorporated in Singapore, with a mission to develop interoperable metadata standards for a broad range of purposes and business models. DCMI is hosted by the National Library Board of Singapore and supported by institutional members and sponsors. From its start in 1995 with a workshop at OCLC in Dublin, Ohio, through incorporation in Singapore in 2009, the Dublin Core Metadata Initiative was managed as an activitiy within OCLC’s Office of Research. DCMI publishes metadata specifications, holds annual conferences, and hosts numerous discussion forums.<\/dd>\n<\/dl>\n
\n
- DCMI Metadata Terms<\/a><\/dt>\n
- The RDF Properties, Classes, Vocabulary Encoding Schemes, and Datatypes declared and maintained by the Dublin Core Metadata Initiative are collectively referred to as DCMI Metadata Terms<\/a>. Of the four types of terms, Properties, Classes, and Datatypes (Syntax Encoding Scheme) are defined exactly as in RDF<\/a>. The notion of a Vocabulary Encoding Scheme is unique to DCMI, though it is similar to — arguably, formally indistinguishable from — the notion of a Concept Scheme<\/a> in Simple Knowledge Organization System (SKOS).<\/dd>\n<\/dl>\n<\/dt>\n
- AACR2<\/strong><\/dt>\n
- See Anglo-American Cataloguing Rules<\/a><\/dd>\n
- <\/a>administrative metadata<\/strong><\/dt>\n
- Metadata used in managing and administering information resources, e.g., location or donor information. Includes rights and access information, data on the creation and preservation of the digital object.<\/dd>\n
- AGLS<\/strong><\/dt>\n
- See AGLS (Australian Government Locator Service)<\/a><\/dd>\n
- <\/a>Anglo-American Cataloguing Rules (AACR2)<\/strong><\/dt>\n
- The dominant bibliographic standard regulating cataloging in the English-speaking world.\u00c2\u00a0 AACR2 represents a set of rules for the standard description of and access to all materials which a library holds or to which it has access.<\/dd>\n
- <\/a>American Standard Code for Information Interchange (ASCII)<\/strong><\/dt>\n
- A scheme that provides standard numeric values to represent letters, numbers, punctuation marks and other characters.\u00c2\u00a0 The use of standard values allows computers and computer programs to exchange data.<\/dd>\n
- <\/a>application profile<\/strong><\/dt>\n
- In DCMI usage, an application profile<\/a> is a declaration of the metadata terms an organization, information resource, application, or user community uses in its metadata. In a broader sense, it includes the set of metadata elements, policies, and guidelines defined for a particular application or implementation. The elements may be from one or more element sets, thus allowing a given application to meet its functional requirements by using metadata elements from several element sets including locally defined sets. For example, a given application might choose a specific subset of the Dublin Core elements that meets its needs, or may include elements from the Dublin Core, another element set, and several locally defined elements, all combined in a single schema. An application profile is not considered complete without documentation that defines the policies and best practices appropriate to the application.<\/dd>\n
- Appropriate values<\/a><\/strong><\/dt>\n
- Best practice for a particular Element or Qualifier may vary by context. Definitions may provide some guidance; other information may be found in “Using Dublin Core”<\/em><\/a>.<\/dd>\n
- ASCII<\/strong><\/dt>\n
- See American Standard Code for Information Interchange<\/a><\/dd>\n
- <\/a>Audience<\/strong><\/dt>\n
- Dublin Core element to record a class of entity for whom the resource is intended or useful. A class of entity may be determined by the creator or the publisher or by a third party. See also “Using Dublin Core”<\/em><\/a>.<\/dd>\n
- Author<\/strong><\/dt>\n
- See Creator<\/a><\/dd>\n
- <\/a>authority control<\/strong><\/dt>\n
- A set of rules or procedures that assist in the maintenance of consistent forms of names or terms within a database.<\/dd>\n
- <\/a>authority file<\/strong><\/dt>\n
- A collection o
\nf authority records.<\/dd>\n- <\/a>authority record<\/strong><\/dt>\n
- A record that registers the preferred form of a personal or corporate name, geographic region or subject term. It may indicate variant forms of the established heading, biographical or cultural information associated with the heading, as well as related headings.<\/dd>\n<\/dl>\n<\/blockquote>\n
<\/a><\/p>\n
B<\/h2>\n
\n\n
- <\/a>Basic Semantics Register<\/strong><\/dt>\n
- An ISO Standard ISO\/TS 16668:2000<\/a> which identifies and defines semantic components for use in data exchange.<\/dd>\n
- <\/a>best practice<\/strong><\/dt>\n
- Guidance and documentation to describe and standardize the use of metadata elements that best support a community’s needs.<\/dd>\n
- BSR<\/strong><\/dt>\n
- See Basic Semantics Register<\/a><\/dd>\n<\/dl>\n<\/blockquote>\n
<\/a><\/p>\n
C<\/h2>\n
\n\n
- <\/a>case-sensitive<\/strong><\/dt>\n
- Lower and upper case letters are not treated as if they were interchangeable; e.g. ‘a’ is not the same as ‘A’.<\/dd>\n
- <\/a>CEN<\/strong><\/dt>\n
- European Committee for Standarization (Comit\u00c3\u00a9 Europ\u00c3\u00a9en de Normalisation; Europ\u00c3\u00a4isches Komitee f\u00c3\u00bcr Normung) “CEN is contributing to the objectives of the European Union and European Economic Area with voluntary technical standards which promote free trade, the safety of workers and consumers, interoperability of networks, environmental protection, exploitation of research and development programmes, and public procurement.” http:\/\/www.cenorm.be\/cenorm\/index.htm<\/a><\/dd>\n
- <\/a>classification<\/strong><\/dt>\n
- A logical scheme for arrangement of knowledge, usually by subject. Classification schema are alpha and\/or numeric; for example, Library of Congress Classification, Dewey Classification, Universal Decimal Classification.<\/dd>\n
- <\/a>controlled vocabulary<\/strong><\/dt>\n
- A prescribed set of consistently used and carefully defined terms.<\/dd>\n
- <\/a>Contributor<\/a><\/strong><\/dt>\n
- The Dublin Core element used to designate the entity responsible for making contributions to the content of the resource. Examples of a Contributor include a person, an organization or a service. Typically, the name of a Contributor should be used to indicate the entity. See also “Using Dublin Core”<\/em><\/a>.<\/dd>\n
- <\/a>Coverage<\/a><\/strong><\/dt>\n
- The Dublin Core element used to designate the extent or scope of the content of the resource. Coverage will typically include spatial location (a place name or geographic co-ordinates), temporal period (a period label, date, or date range) or jurisdiction (such as a named administrative entity). Recommended best practice is to select a value from a controlled vocabulary, and that, where appropriate, named places or time periods be used in preference to numeric identifiers such as sets of co-ordinates or date ranges. See also “Using Dublin Core”<\/em><\/a>.<\/dd>\n
- <\/a>Creator<\/a><\/strong><\/dt>\n
- The Dublin Core element used to designate the entity primarily responsible for making the content of the resource. Examples of a Creator include a person, an organization, or a service. See also “Using Dublin Core”<\/em><\/a>.<\/dd>\n
- <\/a>Crosswalk<\/strong><\/dt>\n
- A table that maps the relationships and equivalencies between two or more metadata schemes. Crosswalks or metadata mapping support the ability of search engines to search effectively across heterogeneous databases.<\/dd>\n<\/dl>\n<\/blockquote>\n
<\/a><\/p>\n
D<\/h2>\n
\n\n
- <\/a>Date<\/a><\/strong><\/dt>\n
- The Dublin Core element used to designate the date associated with an event in the life cycle of the resource. Typically, Date will be associated with the creation or availability of the resource. See also “Using Dublin Core”<\/em><\/a>.<\/dd>\n
- <\/a>DCAPS<\/strong><\/dt>\n
- Dublin Core Application Profile ” is a declaration specifying which metadata terms an organization, information provider, or user community uses in its metadata. By definition, a DCAP identifies the source of metadata terms used – whether they have been defined in formally maintained standards such as Dublin Core, in less formally defined element sets and vocabularies, or by the creator of the DCAP itself for local use in an application. Optionally, a DCAP may provide additional documentation on how the terms are constrained, encoded, or interpreted for application-specific purposes.” See http:\/\/www.ukoln.ac.uk\/metadata\/dcmi\/dc-elem-prop\/<\/a><\/dd>\n
- DCMES<\/strong><\/dt>\n
- Dublin Core Metadata Element Set. See Dublin Core<\/a>.<\/dd>\n
- DCMI<\/strong><\/dt>\n
- See Dublin Core Metadata Initiative<\/a><\/dd>\n
- DCMI recommendation<\/a><\/strong><\/dt>\n
- A DCMI recommendation is a human-readable document that may define one or more DCMI terms.<\/dd>\n
- <\/a>DCMI term<\/a><\/strong><\/dt>\n
- A DCMI term is a DCMI element, a DCMI qualifier or term from a DCMI-maintained controlled vocabulary. Each DCMI term is defined in a DCMI recommendation and is identified by a Uniform Resource Identifier (URI) within a DCMI namespace.<\/dd>\n
- DCMI term declaration<\/a><\/strong><\/dt>\n
- A DCMI term declaration is the machine-processable representation of one or more DCMI terms, expressed in a schema language.<\/dd>\n
- <\/a>Description<\/a><\/strong><\/dt>\n
- The Dublin Core element used to designate a textual description of the content of the resource. See also “Using Dublin Core”<\/em><\/a>.<\/dd>\n
- DCSV<\/strong><\/dt>\n
- See Dublin Core Structured Value<\/a><\/dd>\n
- <\/a>descriptive metadata<\/strong><\/dt>\n
- Metadata that supports the discovery of an object.<\/dd>\n
- <\/a>digital tourist<\/strong><\/dt>\n
- An inexperienced searcher in the digital environment who does not possess knowledge of community- specific vocabularies. The Dublin Core provides a rudimentary vocabulary, or “pidgin language” for information discovery when exploring new digital territories. Coined by Ricky Erway at the Metadata Workshop on Metadata for Networked Images, September 24-25, 1996.<\/dd>\n
- <\/a>discovery software<\/strong><\/dt>\n
- A computer application designed to simplify, assist and expedite the process of finding information resources.<\/dd>\n
- <\/a>Digital Object Identifier<\/a><\/strong><\/dt>\n
- DOI was developed by the International DOI Foundation as a system for identifying and exchanging intellectual property in the digital environment. It provides a mechanism to link a searcher to digital content and facilitates copyright management.<\/dd>\n
- <\/a>Document Type Definition (DTD)<\/strong><\/dt>\n
- In SGML or XML, a formal description of the components of a specific document or class of documents. DTDs provide a formal grammar used for machine processing (parsing) of documents expressed in SGML or XML. A DTD description includes:<\/p>\n
\n
- The containers or elements that make up the document; e.g., paragraphs, headings, list items, figures, tables, etc.<\/li>\n
- The logical structure of the document; e.g., chapters containing sections, etc.<\/li>\n
- Additional information associated with elements (known as attributes); e.g., identifiers, date stamps, etc.<\/li>\n<\/ul>\n<\/dd>\n
- <\/a>document-like object (DLO)<\/strong><\/dt>\n
- Originally defined as an entity that resembles a document from the standpoint that it is substantially text-based and shares other properties of a document; e.g., electronic mail messages or spreadsheets. The definition was expanded at the 3rd DC workshop<\/a> to refer to any discrete information resource that are characterized by being fixed (i.e., having identical content for each user). Examples include text, images, movies, and performances.<\/dd>\n
- DOI<\/strong><\/dt>\n
- see Digital Object Identifier<\/a><\/dd>\n
- <\/a>dot.syntax<\/strong><\/dt>\n
- A mechanism for refining the meaning of the element in HTML; for example, <META NAME=”DC.Title.Alternative” CONTENT=”Title<\/em>“><\/dd>\n
- DTD<\/strong><\/dt>\n
- See Document Type Definition<\/a><\/dd>\n
- <\/a>Dublin Core<\/strong><\/dt>\n
- The Dublin Core is a metadata element set.<\/a> It includes all DCMI terms (that is, refinements, encoding schemes, and controlled vocabulary terms) intended to facilitate discovery of resources. The Dublin Core has been in development since 1995 through a series of focused invitational workshops that gather experts from the library world, the networking and digital library research communities, and a variety of content specialties. See the Dublin Core Web Site<\/a> for additional information.<\/dd>\n
- <\/a>Dublin Core Metadata Initiative<\/strong><\/dt>\n
- The Dublin Core Metadata Initiative is the body responsible for the ongoing maintenance of Dublin Core. DCMI is currently hosted by the OCLC Online Computer Library Center, Inc<\/a>., a not-for-profit international library consortium. The work of DCMI is done by contributors from many institutions in many countries. DCMI is organized into Communities and Task Groups to address particular problems and tasks (see the DCMI Work structure page<\/a>). Participation in DCMI is open to all interested parties. Instructions for joining can be found at the DCMI web site on the DCMI Contact information page<\/a>.<\/dd>\n
- Dublin Core Simple<\/strong><\/dt>\n
- See Simple Dublin Core<\/a><\/dd>\n
- <\/a>Dublin Core Structured Values<\/a><\/strong><\/dt>\n
- DCSV recognizes two types of substrings: labels and values. A label is the name of the type of a value, and a value is the data itself. A value that is comprised of components, i.e. a value which has its own label and value, is called a structured value. Punctuation supports the parsing of the DCSV.<\/dd>\n
- Dublin Core Terms<\/a><\/strong><\/dt>\n
- See DCMI term<\/a><\/dd>\n
- <\/a>Dumb-down Principle<\/a><\/strong><\/dt>\n
- The qualification of Dublin Core Elements is guided by a rule known colloquially as the Dumb-Down Principle. According to this rule, a client should be able to ignore any qualifier and use the value as if it were unqualified. While this may result in some loss of specificity, the remaining term value (minus the qualifier) must continue to be generally correct and useful for discovery. Qualification is therefore supposed only to refine, not extend the semantic scope of an Element.<\/dd>\n<\/dl>\n<\/blockquote>\n
<\/a><\/p>\n
E<\/h2>\n
\n\n
- EAD<\/strong><\/dt>\n
- see EAD (Encoded Archival Description)<\/a><\/dd>\n