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Network Working Group                                        O. JacobsenRequest for Comments: 1208                                      D. Lynch                                                           Interop, Inc.                                                              March 1991A Glossary of Networking TermsStatus of this Memo   This RFC is a glossary adapted from "The INTEROP Pocket Glossary of   Networking Terms" distributed at Interop '90.  This memo provides   information for the Internet community.  It does not specify an   Internet standard.  Distribution of this memo is unlimited.Introduction   This glossary is adapted from "The INTEROP Pocket Glossary of   Networking Terms" produced to help you understand the many terms--and   in particular the myriad of acronyms--that can be encountered at the   INTEROP Tutorials, Conference, and Exhibition.   To keep this document reasonably small we have deliberately omitted   common computer and communications terms such as disk, modem, byte,   and VLSI.  In addition, the definitions have been kept brief.  We   recommend that you consult the glossaries found in the major computer   networking textbooks for more comprehensive definitions.   We also realize that producing this glossary is akin to shooting at a   moving target.  The computer and communications industries are moving   very rapidly, and terms and acronyms are born every day.  You are   invited to submit words which you think should be included in future   editions.Glossary   abstract syntax: A description of a data structure that is   independent of machine-oriented structures and encodings.   ACSE: 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.   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.Jacobsen & Lynch                                                [Page 1]

RFC 1208                INTEROP Pocket Glossary               March 1991   address resolution: A means for mapping Network Layer addresses onto   media-specific addresses.  See ARP.   ADMD: Administration Management Domain.  An X.400 Message Handling   System public service carrier.  Examples: MCImail and ATTmail in the   U.S., British Telecom Gold400mail in the U.K.  The ADMDs in all   countries worldwide together provide the X.400 backbone.  See PRMD.   agent: In the client-server model, the part of the system that   performs information preparation and exchange on behalf of a client   or server application.  See NMS, DUA, MTA.   ANSI: American National Standards Institute.  The U.S.   standardization body. ANSI is a member of the International   Organization for Standardization (ISO)   AOW: Asia and Oceania Workshop.  One of the three regional OSI   Implementors Workshops, equivalent to OIW and EWOS.   API: Application Program Interface.  A set of calling conventions   defining how a service is invoked through a software package.   Application Layer: The top-most layer in the OSI Reference Model   providing such communication services as electronic mail and file   transfer.   ARP: Address Resolution Protocol.  The Internet protocol used to   dynamically map Internet addresses to physical (hardware) addresses   on local area networks. Limited to networks that support hardware   broadcast.   ARPA: Advanced Research Projects Agency.  Now called DARPA, the U.S.   government agency that funded the ARPANET.   ARPANET: A packet switched network developed in the early 1970s.  The   "grandfather" of today's Internet.  ARPANET was decommissioned in   June 1990.   ASN.1: Abstract Syntax Notation One.  The OSI language for describing   abstract syntax.  See BER.   attribute: The form of information items provided by the X.500   Directory Service.  The directory information base consists of   entries, each containing one or more attributes. Each attribute   consists of a type identifier together with one or more values.  Each   directory Read operation can retrieve some or all attributes from a   designated entry.Jacobsen & Lynch                                                [Page 2]

RFC 1208                INTEROP Pocket Glossary               March 1991   Autonomous System: Internet (TCP/IP) terminology for a collection of   gateways (routers) that fall under one administrative entity and   cooperate using a common Interior Gateway Protocol (IGP).  See   subnetwork.   backbone: The primary connectivity mechanism of a hierarchical   distributed system.  All systems which have connectivity to an   intermediate system on the backbone are assured of connectivity to   each other.  This does not prevent systems from setting up private   arrangements with each other to bypass the backbone for reasons of   cost, performance, or security.   Bart Simpson (R): Internet and OSI cult hero.   baseband: Characteristic of any network technology that uses a single   carrier frequency and requires all stations attached to the network   to participate in every transmission.  See broadband.   BER: Basic Encoding Rules.  Standard rules for encoding data units   described in ASN.1.  Sometimes incorrectly lumped under the term   ASN.1, which properly refers only to the abstract syntax description   language, not the encoding technique.   big-endian: A format for storage or transmission of binary data in   which the most significant bit (or byte) comes first.  The reverse   convention is called little-endian.   BITNET: Because It's Time NETwork.  An academic computer network   based originally on IBM mainframe systems interconnected via leased   9600 bps lines.  BITNET has recently merged with CSNET, The   Computer+Science Network (another academic computer network) to form   CREN: The Corporation for Research and Educational Networking.  See   CSNET.   BOC: Bell Operating Company.  More commonly referred to as RBOC for   Regional Bell Operating Company.  The local telephone company in each   of the seven U.S. regions.   bridge: A device that connects two or more physical networks and   forwards packets between them.  Bridges can usually be made to filter   packets, that is, to forward only certain traffic.  Related devices   are: repeaters which simply forward electrical signals from one cable   to another, and full-fledged routers which make routing decisions   based on several criteria.  In OSI terminology, a bridge is a Data   Link Layer intermediate system.  See repeater and router.   broadband: Characteristic of any network that multiplexes multiple,   independent network carriers onto a single cable.  This is usuallyJacobsen & Lynch                                                [Page 3]

RFC 1208                INTEROP Pocket Glossary               March 1991   done using frequency division multiplexing.  Broadband technology   allows several networks to coexist on one single cable; traffic from   one network does not interfere with traffic from another since the   "conversations" happen on different frequencies in the "ether,"   rather like the commercial radio system.   broadcast: A packet delivery system where a copy of a given packet is   given to all hosts attached to the network.  Example: Ethernet.   BSD: Berkeley Software Distribution.  Term used when describing   different versions of the Berkeley UNIX software, as in "4.3BSD   UNIX."   catenet: A network in which hosts are connected to networks with   varying characteristics, and the networks are interconnected by   gateways (routers).  The Internet is an example of a catenet.  See   IONL.   CCITT: International Consultative Committee for Telegraphy and   Telephony.  A unit of the International Telecommunications Union   (ITU) of the United Nations.  An organization with representatives   from the PTTs of the world.  CCITT produces technical standards,   known as "Recommendations," for all internationally controlled   aspects of analog and digital communications.  See X Recommendations.   CCR: Commitment, Concurrency, and Recovery.  An OSI application   service element used to create atomic operations across distributed   systems.  Used primarily to implement two-phase commit for   transactions and nonstop operations.   client-server model: A common way to describenetwork services and the   model user processes (programs) of those services.  Examples include   the name-server/name-resolver paradigm of the DNS and file-   server/file-client relationships such as NFS and diskless hosts.   CLNP: Connectionless Network Protocol.  The OSI protocol for   providing the OSI Connectionless Network Service (datagram service).   CLNP is the OSI equivalent to Internet IP, and is sometimes called   ISO IP.   CLTP: Connectionless Transport Protocol.  Provides for end-to-end   Transport data addressing (via Transport selector) and error control   (via checksum), but cannot guarantee delivery or provide flow   control.  The OSI equivalent of UDP.   CMIP: Common Management Information Protocol.  The OSI network   management protocol.Jacobsen & Lynch                                                [Page 4]

RFC 1208                INTEROP Pocket Glossary               March 1991   CMOT: CMIP Over TCP.  An effort to use the OSI network management   protocol to manage TCP/IP networks.   connectionless: The model of interconnection in which communication   takes place without first establishing a connection.  Sometimes   (imprecisely) called datagram.  Examples: LANs, Internet IP and OSI   CLNP, UDP, ordinary postcards.   connection-oriented: The model of interconnection in which   communication proceeds through three well-defined phases: connection   establishment, data transfer, connection release.  Examples: X.25,   Internet TCP and OSI TP4, ordinary telephone calls.   core gateway: Historically, one of a set of gateways (routers)   operated by the Internet Network Operations Center at BBN.  The core   gateway system forms a central part of Internet routing in that all   groups must advertise paths to their networks from a core gateway,   using the Exterior Gateway Protocol (EGP).  See EGP, backbone.   COS: Corporation for Open Systems.  A vendor and user group for   conformance testing, certification, and promotion of OSI products.   COSINE: Cooperation for Open Systems Interconnection Networking in   Europe.  A program sponsored by the European Commission, aimed at   using OSI to tie together European research networks.   CREN: See BITNET and CSNET.   CSMA/CD: Carrier Sense Multiple Access with Collision Detection.  The   access method used by local area networking technologies such as   Ethernet.   CSNET: Computer+Science Network.  A large computer network, mostly in   the U.S. but with international connections.  CSNET sites include   universities, research labs, and some commercial companies.  Now   merged with BITNET to form CREN.  See BITNET.   DARPA: Defense Advanced Research Projects Agency.  The U.S.   government agency that funded the ARPANET.   Data Link Layer: The OSI layer that is responsible for data transfer   across a single physical connection, or series of bridged   connections, between two Network entities.   DCA: Defense Communications Agency.  The government agency   responsible for the Defense Data Network (DDN).Jacobsen & Lynch                                                [Page 5]

RFC 1208                INTEROP Pocket Glossary               March 1991   DCE: Distributed Computing Environment.  An architecture of standard   programming interfaces, conventions, and server functionalities   (e.g., naming, distributed file system, remote procedure call) for   distributing applications transparently across networks of   heterogeneous computers.  Promoted and controlled by the Open   Software Foundation (OSF), a consortium led by HP, DEC, and IBM.  See   ONC.   DDN: Defense Data Network.  Comprises the MILNET and several other   DoD networks.   DECnet: Digital Equipment Corporation's proprietary network   architecture.   DNS: Domain Name System.  The distributed name/address mechanism used   in the Internet.   domain: In the Internet, a part of a naming hierarchy.   Syntactically, an Internet domain name consists of a sequence of   names (labels) separated by periods (dots), e.g., "tundra.mpk.ca.us."   In OSI, "domain" is generally used as an administrative partition of   a complex distributed system, as in MHS Private Management Domain   (PRMD), and Directory Management Domain (DMD).   dotted decimal notation: The syntactic representation for a 32-bit   integer that consists of four 8-bit numbers written in base 10 with   periods (dots) separating them.  Used to represent IP addresses in   the Internet as in: 192.67.67.20.   DSA: Directory System Agent.  The software that provides the X.500   Directory Service for a portion of the directory information base.   Generally, each DSA is responsible for the directory information for   a single organization or organizational unit.   DUA: Directory User Agent.  The software that accesses the X.500   Directory Service on behalf of the directory user.  The directory   user may be a person or another software element.   EARN: European Academic Research Network.  A network using BITNET   technology connecting universities and research labs in Europe.   EGP: Exterior Gateway Protocol.  A reachability routing protocol used   by gateways in a two-level internet.  EGP is used in the Internet   core system.  See core gateway.   encapsulation: The technique used by layered protocols in which a   layer adds header information to the protocol data unit (PDU) from   the layer above.  As an example, in Internet terminology, a packetJacobsen & Lynch                                                [Page 6]

RFC 1208                INTEROP Pocket Glossary               March 1991   would contain a header from the physical layer, followed by a header   from the network layer (IP), followed by a header from the transport   layer (TCP), followed by the application protocol data.   end system: An OSI system which contains application processes   capable of communicating through all seven layers of OSI protocols.   Equivalent to Internet host.   entity: OSI terminology for a layer protocol machine.  An entity   within a layer performs the functions of the layer within a single   computer system, accessing the layer entity below and providing   services to the layer entity above at local service access points.   ES-IS: End system to Intermediate system protocol.  The OSI protocol   by which end systems announce themselves to intermediate systems.   EUnet: European UNIX Network.   EUUG: European UNIX Users Group.   EWOS: European Workshop for Open Systems.  The OSI Implementors   Workshop for Europe.  See OIW.   FARNET: Federation of American Research NETworks.   FDDI: Fiber Distributed Data Interface.  An emerging high-speed   networking standard.  The underlying medium is fiber optics, and the   topology is a dual-attached, counter-rotating Token Ring.  FDDI   networks can often be spotted by the orange fiber "cable."   FIPS: Federal Information Processing Standard.   flame: To express strong opinion and/or criticism of something,   usually as a frank inflammatory statement in an electronic message.   FNC: Federal Networking Council.  The body responsible for   coordinating networking needs among U.S. Federal agencies.   fragmentation: The process in which an IP datagram is broken into   smaller pieces to fit the requirements of a given physical network.   The reverse process is termed reassembly.  See MTU.   FRICC: Federal Research Internet Coordinating Committee.  Now   replaced by the FNC.   FTAM: File Transfer, Access, and Management.  The OSI remote file   service and protocol.Jacobsen & Lynch                                                [Page 7]

RFC 1208                INTEROP Pocket Glossary               March 1991   FTP: File Transfer Protocol.  The Internet protocol (and program)   used to transfer files between hosts.  See FTAM.   gateway: The original Internet term for what is now called router or   more precisely, IP router.  In modern usage, the terms "gateway" and   "application gateway" refer to systems which do translation from some   native format to another.  Examples include X.400 to/fromRFC 822   electronic mail gateways.  See router.   GOSIP: Government OSI Profile.  A U.S. Government procurement   specification for OSI protocols.   IAB: Internet Activities Board.  The technical body that oversees the   development of the Internet suite of protocols (commonly referred to   as "TCP/IP").  It has two task forces (the IRTF and the IETF) each   charged with investigating a particular area.   ICMP: Internet Control Message Protocol.  The protocol used to handle   errors and control messages at the IP layer.  ICMP is actually part   of the IP protocol.   IESG: Internet Engineering Steering Group.  The executive committee   of the IETF.   IETF: Internet Engineering Task Force.  One of the task forces of the   IAB.  The IETF is responsible for solving short-term engineering   needs of the Internet.  It has over 40 Working Groups.   IGP: Interior Gateway Protocol.  The protocol used to exchange   routing information between collaborating routers in the Internet.   RIP and OSPF are examples of IGPs.   IGRP: Internet Gateway Routing Protocol.  A proprietary IGP used by   cisco System's routers.   INTAP: Interoperability Technology Association for Information   Processing.  The technical organization which has the official   charter to develop Japanese OSI profiles and conformance tests.   intermediate system: An OSI system which is not an end system, but   which serves instead to relay communications between end systems.   See repeater, bridge, and router.   internet: A collection of networks interconnected by a set of routers   which allow them to function as a single, large virtual network.   Internet: (note the capital "I") The largest internet in the world   consisting of large national backbone nets (such as MILNET, NSFNET,Jacobsen & Lynch                                                [Page 8]

RFC 1208                INTEROP Pocket Glossary               March 1991   and CREN) and a myriad of regional and local campus networks all over   the world.  The Internet uses the Internet protocol suite.  To be on   the Internet you must have IP connectivity, i.e., be able to Telnet   to--or ping--other systems.  Networks with only e-mail connectivity   are not actually classified as being on the Internet.   Internet address: A 32-bit address assigned to hosts using TCP/IP.   See dotted decimal notation.   IONL: Internal Organization of the Network Layer.  The OSI standard   for the detailed architecture of the Network Layer.  Basically, it   partitions the Network layer into subnetworks interconnected by   convergence protocols (equivalent to internetworking protocols),   creating what Internet calls a catenet or internet.   IP: Internet Protocol.  The network layer protocol for the Internet   protocol suite.   IP datagram: The fundamental unit of information passed across the   Internet. Contains source and destination addresses along with data   and a number of fields which define such things as the length of the   datagram, the header checksum, and flags to say whether the datagram   can be (or has been) fragmented.   IRTF: Internet Research Task Force.  One of the task forces of the   IAB.  The group responsible for research and development of the   Internet protocol suite.   ISDN: Integrated Services Digital Network.  An emerging technology   which is beginning to be offered by the telephone carriers of the   world.  ISDN combines voice and digital network services in a single   medium making it possible to offer customers digital data services as   well as voice connections through a single "wire."  The standards   that define ISDN are specified by CCITT.   IS-IS: Intermediate system to Intermediate system protocol.  The OSI   protocol by which intermediate systems exchange routing information.   ISO: International Organization for Standardization.  You knew that,   right? Best known for the 7-layer OSI Reference Model.  See OSI.   ISODE: ISO Development Environment.  A popular implementation of the   upper layers of OSI.  Pronounced eye-so-dee-eee.   JANET: Joint Academic Network.  A university network in the U.K.   JUNET: Japan UNIX Network.Jacobsen & Lynch                                                [Page 9]

RFC 1208                INTEROP Pocket Glossary               March 1991   KA9Q: A popular implementation of TCP/IP and associated protocols for   amateur packet radio systems.   Kermit: A popular file transfer and terminal emulation program.   little-endian: A format for storage or transmission of binary data in   which the least significant byte (bit) comes first.  See big-endian.   mail exploder: Part of an electronic mail delivery system which   allows a message to be delivered to a list of addressees.  Mail   exploders are used to implement mailing lists.  Users send messages   to a single address (e.g., hacks@somehost.edu) and the mail exploder   takes care of delivery to the individual mailboxes in the list.   mail gateway: A machine that connects two or more electronic mail   systems (especially dissimilar mail systems on two different   networks) and transfers messages between them.  Sometimes the mapping   and translation can be quite complex, and generally it requires a   store-and-forward scheme whereby the message is received from one   system completely before it is transmitted to the next system after   suitable translations.   Martian: Humorous term applied to packets that turn up unexpectedly   on the wrong network because of bogus routing entries.  Also used as   a name for a packet which has an altogether bogus (non-registered or   ill-formed) Internet address.   MHS: Message Handling System.  The system of message user agents,   message transfer agents, message stores, and access units which   together provide OSI electronic mail.  MHS is specified in the CCITT   X.400 series of Recommendations.   MIB: Management Information Base.  A collection of objects that can   be accessed via a network management protocol.  See SMI.   MILNET: MILitary NETwork.  Originally part of the ARPANET, MILNET was   partitioned in 1984 to make it possible for military installations to   have reliable network service, while the ARPANET continued to be used   for research.  See DDN.   MTA: Message Transfer Agent.  An OSI application process used to   store and forward messages in the X.400 Message Handling System.   Equivalent to Internet mail agent.   MTU: Maximum Transmission Unit.  The largest possible unit of data   that can be sent on a given physical medium.  Example: The MTU of   Ethernet is 1500 bytes.  See fragmentation.Jacobsen & Lynch                                               [Page 10]

RFC 1208                INTEROP Pocket Glossary               March 1991   multicast: A special form of broadcast where copies of the packet are   delivered to only a subset of all possible destinations.  See   broadcast.   multi-homed host: A computer connected to more than one physical data   link.  The data links may or may not be attached to the same network.   name resolution: The process of mapping a name into the corresponding   address.  See DNS.   NetBIOS: Network Basic Input Output System.  The standard interface   to networks on IBM PC and compatible systems.   Network Address: See Internet address or OSI Network Address.   Network Layer: The OSI layer that is responsible for routing,   switching, and subnetwork access across the entire OSI environment.   NFS(R): Network File System.  A distributed file system developed by   Sun Microsystems which allows a set of computers to cooperatively   access each other's files in a transparent manner.   NIC: Network Information Center.  Originally there was only one,   located at SRI International and tasked to serve the ARPANET (and   later DDN) community.  Today, there are many NICs, operated by local,   regional, and national networks all over the world.  Such centers   provide user assistance, document service, training, and much more.   NIST: National Institute of Standards and Technology.  (Formerly   NBS).  See OIW.   NMS: Network Management Station.  The system responsible for managing   a (portion of a) network.  The NMS talks to network management   agents, which reside in the managed nodes, via a network management   protocol.  See agent.   NOC: Network Operations Center.  Any center tasked with the   operational aspects of a production network.  These tasks include   monitoring and control, trouble-shooting, user assistance, and so on.   NSAP: Network Service Access Point.  The point at which the OSI   Network Service is made available to a Transport entity.  The NSAPs   are identified by OSI Network Addresses.   NSF: National Science Foundation.  Sponsors of the NSFNET.   NSFNET: National Science Foundation NETwork.  A collection of local,   regional, and mid-level networks in the U.S. tied together by a   high-speed backbone.  NSFNET provides scientists access to a numberJacobsen & Lynch                                               [Page 11]

RFC 1208                INTEROP Pocket Glossary               March 1991   of supercomputers across the country.   OIW: Workshop for Implementors of OSI.  Frequently called NIST OIW or   the NIST Workshop, this is the North American regional forum at which   OSI implementation agreements are decided.  It is equivalent to EWOS   in Europe and AOW in the Pacific.   ONC(tm): Open Network Computing.  A distributed applications   architecture promoted and controlled by a consortium led by Sun   Microsystems.   OSI: Open Systems Interconnection.  An international standardization   program to facilitate communications among computers from different   manufacturers.  See ISO.   OSI Network Address: The address, consisting of up to 20 octets, used   to locate an OSI Transport entity.  The address is formatted into an   Initial Domain Part which is standardized for each of several   addressing domains, and a Domain Specific Part which is the   responsibility of the addressing authority for that domain.   OSI Presentation Address: The address used to locate an OSI   Application entity.  It consists of an OSI Network Address and up to   three selectors, one each for use by the Transport, Session, and   Presentation entities.   OSPF: Open Shortest Path First.  A "Proposed Standard" IGP for the   Internet.  See IGP.   PCI: Protocol Control Information.  The protocol information added by   an OSI entity to the service data unit passed down from the layer   above, all together forming a Protocol Data Unit (PDU).   PDU: Protocol Data Unit.  This is OSI terminology for "packet."  A   PDU is a data object exchanged by protocol machines (entities) within   a given layer.  PDUs consist of both Protocol Control Information   (PCI) and user data.   Physical Layer: The OSI layer that provides the means to activate and   use physical connections for bit transmission.  In plain terms, the   Physical Layer provides the procedures for transferring a single bit   across a Physical Media.   Physical Media: Any means in the physical world for transferring   signals between OSI systems.  Considered to be outside the OSI Model,   and therefore sometimes referred to as "Layer 0."  The physical   connector to the media can be considered as defining the bottom   interface of the Physical Layer, i.e., the bottom of the OSIJacobsen & Lynch                                               [Page 12]

RFC 1208                INTEROP Pocket Glossary               March 1991   Reference Model.   ping: Packet internet groper.  A program used to test reachability of   destinations by sending them an ICMP echo request and waiting for a   reply.  The term is used as a verb: "Ping host X to see if it is up!"   port: The abstraction used by Internet transport protocols to   distinguish among multiple simultaneous connections to a single   destination host.  See selector.   POSI: Promoting Conference for OSI.  The OSI "800-pound gorilla" in   Japan.  Consists of executives from the six major Japanese computer   manufacturers and Nippon Telephone and Telegraph.  They set policies   and commit resources to promote OSI.   PPP: Point-to-Point Protocol.  The successor to SLIP, PPP provides   router-to-router and host-to-network connections over both   synchronous and asynchronous circuits.  See SLIP.   Presentation Address: See OSI Presentation Address.   Presentation Layer: The OSI layer that determines how Application   information is represented (i.e., encoded) while in transit between   two end systems.   PRMD: Private Management Domain.  An X.400 Message Handling System   private organization mail system.  Example: NASAmail.  See ADMD.   protocol: A formal description of messages to be exchanged and rules   to be followed for two or more systems to exchange information.   proxy: The mechanism whereby one system "fronts for" another system   in responding to protocol requests.  Proxy systems are used in   network management to avoid having to implement full protocol stacks   in simple devices, such as modems.   proxy ARP: The technique in which one machine, usually a router,   answers ARP requests intended for another machine.  By "faking" its   identity, the router accepts responsibility for routing packets to   the "real" destination.  Proxy ARP allows a site to use a single IP   address with two physical networks.  Subnetting would normally be a   better solution.   PSN: Packet Switch Node.  The modern term used for nodes in the   ARPANET and MILNET.  These used to be called IMPs (Interface Message   Processors).  PSNs are currently implemented with BBN C30 or C300   minicomputers.Jacobsen & Lynch                                               [Page 13]

RFC 1208                INTEROP Pocket Glossary               March 1991   RARE: Reseaux Associes pour la Recherche Europeenne.  European   association of research networks.   RARP: Reverse Address Resolution Protocol.  The Internet protocol a   diskless host uses to find its Internet address at startup.  RARP   maps a physical (hardware) address to an Internet address.  See ARP.   RBOC: Regional Bell Operating Company.  See BOC.   repeater: A device which propagates electrical signals from one cable   to another without making routing decisions or providing packet   filtering.  In OSI terminology, a repeater is a Physical Layer   intermediate system.  See bridge and router.   RFC: Request For Comments.  The document series, begun in 1969, which   describes the Internet suite of protocols and related experiments.   Not all (in fact very few) RFCs describe Internet standards, but all   Internet standards are written up as RFCs.   RFS: Remote File System.  A distributed file system, similar to NFS,   developed by AT&T and distributed with their UNIX System V operating   system.  See NFS.   RIP: Routing Information Protocol.  An Interior Gateway Protocol   (IGP) supplied with Berkeley UNIX.   RIPE: Reseaux IP Europeenne.  European continental TCP/IP network   operated by EUnet.  See EUnet.   rlogin: A service offered by Berkeley UNIX which allows users of one   machine to log into other UNIX systems (for which they are   authorized) and interact as if their terminals were connected   directly.  Similar to Telnet.   ROSE: Remote Operations Service Element.  A lightweight RPC protocol,   used in OSI Message Handling, Directory, and Network Management   application protocols.   router: A system responsible for making decisions about which of   several paths network (or Internet) traffic will follow.  To do this   it uses a routing protocol to gain information about the network, and   algorithms to choose the best route based on several criteria known   as "routing metrics."  In OSI terminology, a router is a Network   Layer intermediate system.  See gateway, bridge and repeater.   RPC: Remote Procedure Call.  An easy and popular paradigm for   implementing the client-server model of distributed computing.  A   request is sent to a remote system to execute a designated procedure,Jacobsen & Lynch                                               [Page 14]

RFC 1208                INTEROP Pocket Glossary               March 1991   using arguments supplied, and the result returned to the caller.   There are many variations and subtleties, resulting in a variety of   different RPC protocols.   RTSE: Reliable Transfer Service Element.  A lightweight OSI   application service used above X.25 networks to handshake application   PDUs across the Session Service and TP0.  Not needed with TP4, and   not recommended for use in the U.S. except when talking to X.400   ADMDs.   SAP: Service Access Point.  The point at which the services of an OSI   layer are made available to the next higher layer.  The SAP is named   according to the layer providing the services: e.g., Transport   services are provided at a Transport SAP (TSAP) at the top of the   Transport Layer.   selector: The identifier used by an OSI entity to distinguish among   multiple SAPs at which it provides services to the layer above.  See   port.   Session Layer: The OSI layer that provides means for dialogue control   between end systems.   SGMP: Simple Gateway Management Protocol.  The predecessor to SNMP.   See SNMP.   SLIP: Serial Line IP.  An Internet protocol used to run IP over   serial lines such as telephone circuits or RS-232 cables   interconnecting two systems.  SLIP is now being replaced by PPP.  See   PPP.   SMDS: Switched Multimegabit Data Service.  An emerging high-speed   networking technology to be offered by the telephone companies in the   U.S.   SMI: Structure of Management Information.  The rules used to define   the objects that can be accessed via a network management protocol.   See MIB.   SMTP: Simple Mail Transfer Protocol.  The Internet electronic mail   protocol.  Defined inRFC 821, with associated message format   descriptions inRFC 822.   SNA: Systems Network Architecture.  IBM's proprietary network   architecture.   SNMP: Simple Network Management Protocol.  The network management   protocol of choice for TCP/IP-based internets.Jacobsen & Lynch                                               [Page 15]

RFC 1208                INTEROP Pocket Glossary               March 1991   SPAG: Standards Promotion and Application Group.  A group of European   OSI manufacturers which chooses option subsets and publishes these in   a "Guide to the Use of Standards" (GUS).   SQL: Structured Query Language.  The international standard language   for defining and accessing relational databases.   subnet mask: See address mask.   subnetwork: A collection of OSI end systems and intermediate systems   under the control of a single administrative domain and utilizing a   single network access protocol.  Examples: private X.25 networks,   collection of bridged LANs.   TCP: Transmission Control Protocol.  The major transport protocol in   the Internet suite of protocols providing reliable, connection-   oriented, full-duplex streams.  Uses IP for delivery.  See TP4.   Telnet: The virtual terminal protocol in the Internet suite of   protocols.  Allows users of one host to log into a remote host and   interact as normal terminal users of that host.   three-way-handshake: The process whereby two protocol entities   synchronize during connection establishment.   TP0: OSI Transport Protocol Class 0 (Simple Class).  This is the   simplest OSI Transport Protocol, useful only on top of an X.25   network (or other network that does not lose or damage data).   TP4: OSI Transport Protocol Class 4 (Error Detection and Recovery   Class).  This is the most powerful OSI Transport Protocol, useful on   top of any type of network.  TP4 is the OSI equivalent to TCP.   transceiver: Transmitter-receiver.  The physical device that connects   a host interface to a local area network, such as Ethernet.  Ethernet   transceivers contain electronics that apply signals to the cable and   sense collisions.   Transport Layer: The OSI layer that is responsible for reliable end-   to-end data transfer between end systems.   UA: User Agent.  An OSI application process that represents a human   user or organization in the X.400 Message Handling System.  Creates,   submits, and takes delivery of messages on the user's behalf.   UDP: User Datagram Protocol.  A transport protocol in the Internet   suite of protocols.  UDP, like TCP, uses IP for delivery; however,   unlike TCP, UDP provides for exchange of datagrams withoutJacobsen & Lynch                                               [Page 16]

RFC 1208                INTEROP Pocket Glossary               March 1991   acknowledgements or guaranteed delivery.  See CLTP.   UUCP: UNIX to UNIX Copy Program.  A protocol used for communication   between consenting UNIX systems.   XDR: eXternal Data Representation.  A standard for machine-   independent data structures developed by Sun Microsystems.  Similar   to ASN.1.   X/Open: A group of computer manufacturers that promotes the   development of portable applications based on UNIX.  They publish a   document called the X/Open Portability Guide.   X Recommendations: The CCITT documents that describe data   communication network standards.  Well-known ones include: X.25   Packet Switching standard, X.400 Message Handling System, and X.500   Directory Services.   The X Window System (TM): A popular window system developed by MIT   and implemented on a number of workstations.For More Information   As indicated in the introduction, this is only a partial list of   words from the world of interoperability.  Yes, you're right, we   didn't list "interoperability" because the jury is still out on   exactly what it means, and we invite you to suggest a definition.   To learn more about these topics, consult the books, standards   documents, bibliographies, periodicals, mailing lists, etc. listed in   "Information Sources" in the December 1989 issue of ConneXions--The   Interoperability Report.Security Considerations   Security issues are not discussed in this memo.Jacobsen & Lynch                                               [Page 17]

RFC 1208                INTEROP Pocket Glossary               March 1991Authors' Addresses   Ole J. Jacobsen   Interop, Inc.   480 San Antonio Road   Suite 100   Mountain View, CA 94040   Phone: (415) 941-3399   EMail: OLE@CSLI.STANFORD.EDU   Daniel C. Lynch   Interop, Inc.   480 San Antonio Road   Interop, Inc.   480 San Antonio Road   Suite 100   Mountain View, CA 94040   Phone: (415) 941-3399   EMail: Lynch@ISI.EDUJacobsen & Lynch                                               [Page 18]