Network Working Group G. Malkin, Editor Request for Comments: 1983 Xylogics FYI: 18 August 1996 Obsoletes: 1392 Category: Informational Internet Users' Glossary Status of this Memo This memo provides information for the Internet community. This memo does not specify an Internet standard of any kind. Distribution of this memo is unlimited. Abstract There are many networking glossaries in existence. This glossary concentrates on terms which are specific to the Internet. Naturally, there are entries for some basic terms and acronyms because other entries refer to them. Acknowledgements This document is the work of the User Glossary Working Group of the User Services Area of the Internet Engineering Task Force. I would especially like to thank Ryan Moats/InterNIC for his careful review and many contributions to this document. Table of Contents non-letter . . 2 I . . . . . . . 26 R . . . . . . . 46 A . . . . . . . 2 J . . . . . . . 33 S . . . . . . . 49 B . . . . . . . 7 K . . . . . . . 33 T . . . . . . . 52 C . . . . . . . 10 L . . . . . . . 33 U . . . . . . . 55 D . . . . . . . 14 M . . . . . . . 35 V . . . . . . . 57 E . . . . . . . 18 N . . . . . . . 39 W . . . . . . . 57 F . . . . . . . 20 O . . . . . . . 42 X . . . . . . . 59 G . . . . . . . 22 P . . . . . . . 43 Y . . . . . . . 60 H . . . . . . . 23 Q . . . . . . . 46 Z . . . . . . . 60 References . . . . . . . . . . . . . . . . . . . . . . . . . . 61 Security Considerations . . . . . . . . . . . . . . . . . . . . 62 Editor's Address . . . . . . . . . . . . . . . . . . . . . . . 62 Malkin Informational [Page 1] RFC 1983 Glossary August 1996 Glossary 10Base2 A physical layer communications specification for 10Mbps, baseband data transmission over a coaxial cable (Thinnet) with a maximum cable segment length of 200 meters. 10Base5 A physical layer communications specification for 10Mbps, baseband data transmission over a coaxial cable (Thicknet) with a maximum cable segment length of 500 meters. 10BaseF A physical layer communications specification for 10Mbps, baseband data transmission over a fiber-optic cable. 10BaseT A physical layer communications specification for 10Mbps, baseband data transmission over a twisted-pair copper wire. 802.x The set of IEEE standards for the definition of LAN protocols. See also: IEEE. 822 See: RFC 822 :-) This odd symbol is one of the ways a person can portray "mood" in the very flat medium of computers--by using "smiley faces". This is "metacommunication", and there are literally hundreds of such symbols, from the obvious to the obscure. This particular example expresses "happiness". Don't see it? Tilt your head to the left 90 degrees. Smiles are also used to denote sarcasm. [Source: ZEN] abstract syntax A description of a data structure that is independent of machine- oriented structures and encodings. [Source: RFC1208] Abstract Syntax Notation One (ASN.1) The language used by the OSI protocols for describing abstract syntax. This language is also used to encode SNMP packets. ASN.1 is defined in ISO documents 8824.2 and 8825.2. See also: Basic Encoding Rules. Malkin Informational [Page 2] RFC 1983 Glossary August 1996 Acceptable Use Policy (AUP) Many transit networks have policies which restrict the use to which the network may be put. For example, some networks may only be used for non-commercial purposes. Some AUPs limit the type of material which can be made available to the public (e.g., pornographic material). Enforcement of AUPs varies with the network. See also: netiquette. Access Control List (ACL) Most network security systems operate by allowing selective use of services. An Access Control List is the usual means by which access to, and denial of, services is controlled. It is simply a list of the services available, each with a list of the hosts permitted to use the service. ACK See: Acknowledgment acknowledgment (ACK) A type of message sent to indicate that a block of data arrived at its destination without error. See also: Negative Acknowledgement. [Source: NNSC] ACL See: Access Control List AD See: Administrative Domain address There are four types of addresses in common use within the Internet. They are email address; IP, internet or Internet address; hardware or MAC address; and URL. See also: email address, IP address, internet address, MAC address, Uniform Resource Locator. address mask A bit mask used to identify which bits in an IP address correspond to the network and subnet portions of the address. This mask is often referred to as the subnet mask because the network portion of the address (i.e., the network mask) can be determined by the encoding inherent in an IP address. See also: Classless Inter- domain Routing. Malkin Informational [Page 3] RFC 1983 Glossary August 1996 address resolution Conversion of a network-layer address (e.g. IP address) into the corresponding physical address (e.g., MAC address). See also: IP address, MAC address. Address Resolution Protocol (ARP) Used to dynamically discover the low level physical network hardware address that corresponds to the high level IP address for a given host. ARP is limited to physical network systems that support broadcast packets that can be heard by all hosts on the network. See also: proxy ARP, Reverse Address Resolution Protocol. Administrative Domain (AD) A collection of hosts and routers, and the interconnecting network(s), managed by a single administrative authority. Advanced Research Projects Agency (ARPA) An agency of the U.S. Department of Defense responsible for the development of new technology for use by the military. ARPA (formerly known as DARPA, nee ARPA) was responsible for funding much of the development of the Internet we know today, including the Berkeley version of Unix and TCP/IP. [Source: NNSC] Advanced Research Projects Agency Network (ARPANET) A pioneering longhaul network funded by ARPA. Now retired, it served as the basis for early networking research as well as a central backbone during the development of the Internet. The ARPANET consisted of individual packet switching computers interconnected by leased lines. See also: Advanced Research Projects Agency. [Source: FYI4] 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. [Source: RFC1208] alias A name, usually short and easy to remember, that is translated into another name, usually long and difficult to remember. American National Standards Institute (ANSI) This organization is responsible for approving U.S. standards in many areas, including computers and communications. Standards approved by this organization are often called ANSI standards Malkin Informational [Page 4] RFC 1983 Glossary August 1996 (e.g., ANSI C is the version of the C language approved by ANSI). ANSI is a member of ISO. See also: International Organization for Standardization. [Source: NNSC] American Standard Code for Information Interchange (ASCII) A standard character-to-number encoding widely used in the computer industry. See also: EBCDIC. anonymous FTP Anonymous FTP allows a user to retrieve documents, files, programs, and other archived data from anywhere in the Internet without having to establish a userid and password. By using the special userid of "anonymous" the network user will bypass local security checks and will have access to publicly accessible files on the remote system. See also: archive site, File Transfer Protocol, World Wide Web. ANSI See: American National Standards Institute API See: Application Program Interface Appletalk A networking protocol developed by Apple Computer for communication between Apple Computer products and other computers. This protocol is independent of the network layer on which it is run. Current implementations exist for Localtalk, a 235Kb/s local area network; and Ethertalk, a 10Mb/s local area network. [Source: NNSC] application A program that performs a function directly for a user. FTP, mail and Telnet clients are examples of network applications. application layer The top layer of the network protocol stack. The application layer is concerned with the semantics of work (e.g. formatting electronic mail messages). How to represent that data and how to reach the foreign node are issues for lower layers of the network. [Source: MALAMUD] Application Program Interface (API) A set of calling conventions which define how a service is invoked through a software package. [Source: RFC1208] Malkin Informational [Page 5] RFC 1983 Glossary August 1996 archie A system to automatically gather, index and serve information on the Internet. The initial implementation of archie provided an indexed directory of filenames from all anonymous FTP archives on the Internet. Later versions provide other collections of information. See also: archive site, Gopher, Prospero, Wide Area Information Servers. archive site A machine that provides access to a collection of files across the Internet. For example, an anonymous FTP archive site provides access to arcived material via the FTP protocol. WWW servers can also serve as archive sites. See also: anonymous FTP, archie, Gopher, Prospero, Wide Area Information Servers, World Wide Web. ARP See: Address Resolution Protocol ARPA See: Advanced Research Projects Agency ARPANET See: Advanced Research Projects Agency Network AS See: Autonomous System ASCII See: American Standard Code for Information Interchange ASN.1 See: Abstract Syntax Notation One assigned numbers The RFC [STD2] which documents the currently assigned values from several series of numbers used in network protocol implementations. This RFC is updated periodically and, in any case, current information can be obtained from the Internet Assigned Numbers Authority (IANA). If you are developing a protocol or application that will require the use of a link, socket, port, protocol, etc., please contact the IANA to receive a number assignment. See also: Internet Assigned Numbers Authority, STD. [Source: STD2] Malkin Informational [Page 6] RFC 1983 Glossary August 1996 Asynchronous Transfer Mode (ATM) A standard which defines high-load, high-speed (1.544Mbps through 1.2Gbps), fixed-size packet (cell) switching with dynamic bandwidth allocation. ATM is also known as "fast packet." ATM See: Asynchronous Transfer Mode AUP See: Acceptable Use Policy authentication The verification of the identity of a person or process. [Source: MALAMUD] Autonomous System (AS) A collection of routers under a single administrative authority using a common Interior Gateway Protocol for routing packets. backbone The top level in a hierarchical network. Stub and transit networks which connect to the same backbone are guaranteed to be interconnected. See also: stub network, transit network. bandwidth Technically, the difference, in Hertz (Hz), between the highest and lowest frequencies of a transmission channel. However, as typically used, the amount of data that can be sent through a given communications circuit. bang path A series of machine names used to direct electronic mail from one user to another, typically by specifying an explicit UUCP path through which the mail is to be routed. See also: email address, mail path, UNIX-to-UNIX CoPy. baseband A transmission medium through which digital signals are sent without complicated frequency shifting. In general, only one communication channel is available at any given time. Ethernet is an example of a baseband network. See also: broadband, Ethernet. [Source: NNSC] Malkin Informational [Page 7] RFC 1983 Glossary August 1996 Basic Encoding Rules (BER) 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. See also: Abstract Syntax Notation One. [Source: NNSC] BBS See: Bulletin Board System BCNU Be Seein' You BCP The newest subseries of RFCs which are written to describe Best Current Practices in the Internet. Rather than specifying a protocol, these documents specify the best ways to use the protocols and the best ways to configure options to ensure interoperability between various vendors' products. BCPs carry the endorsement of the IESG. See also: Request For Comments, Internet Engineering Steering Group. BER See: Basic Encoding Rules Berkeley Internet Name Daemon (BIND) Implementation of a DNS server developed and distributed by the University of California at Berkeley. Many Internet hosts run BIND, and it is the ancestor of many commercial BIND implementations. See also: Domain Name System. Berkeley Software Distribution (BSD) Implementation of the UNIX operating system and its utilities developed and distributed by the University of California at Berkeley. "BSD" is usually preceded by the version number of the distribution, e.g., "4.3 BSD" is version 4.3 of the Berkeley UNIX distribution. Many Internet hosts run BSD software, and it is the ancestor of many commercial UNIX implementations. [Source: NNSC] BGP See: Border Gateway Protocol big-endian A format for storage or transmission of binary data in which the most significant bit (or byte) comes first. The term comes from "Gulliver's Travels" by Jonathan Swift. The Lilliputians, being very small, had correspondingly small political problems. The Malkin Informational [Page 8] RFC 1983 Glossary August 1996 Big-Endian and Little-Endian parties debated over whether soft- boiled eggs should be opened at the big end or the little end. See also: little-endian. [Source: RFC1208] binary 11001001 BIND See: Berkeley Internet Name Daemon Birds Of a Feather (BOF) A Birds Of a Feather (flocking together) is an informal discussion group. It is formed, often ad hoc, to consider a specific issue and, therefore, has a narrow focus. See also: Working Group. Bitnet An academic computer network that provides interactive electronic mail and file transfer services, using a store-and-forward protocol, based on IBM Network Job Entry protocols. Bitnet-II encapsulates the Bitnet protocol within IP packets and depends on the Internet to route them. BOF See: Birds Of a Feather BOOTP The Bootstrap Protocol, described in RFC 1542, is used for booting diskless nodes. See also: Dynamic Host Configuration Protocol, Reverse Address Resolution Protocol. Border Gateway Protocol (BGP) The Border Gateway Protocol is an exterior gateway protocol defined in RFC 1771. It's design is based on experience gained with EGP, as defined in RFC 904, and EGP usage in the NSFNET Backbone, as described in RFCs 1092 and 1093. See also: Exterior Gateway Protocol. bounce The return of a piece of mail because of an error in its delivery. [Source: ZEN] bridge A device which forwards traffic between network segments based on datalink layer information. These segments would have a common network layer address. See also: gateway, router. Malkin Informational [Page 9] RFC 1983 Glossary August 1996 broadband A transmission medium capable of supporting a wide range of frequencies. It can carry multiple signals by dividing the total capacity of the medium into multiple, independent bandwidth channels, where each channel operates only on a specific range of frequencies. See also: baseband. broadcast A special type of multicast packet which all nodes on the network are always willing to receive. See also: multicast, unicast. broadcast storm An incorrect packet broadcast onto a network that causes multiple hosts to respond all at once, typically with equally incorrect packets which causes the storm to grow exponentially in severity. See also: Ethernet meltdown. brouter A device which bridges some packets (i.e. forwards based on datalink layer information) and routes other packets (i.e. forwards based on network layer information). The bridge/route decision is based on configuration information. See also: bridge, router. BSD See: Berkeley Software Distribution BTW By The Way Bulletin Board System (BBS) A computer, and associated software, which typically provides electronic messaging services, archives of files, and any other services or activities of interest to the bulletin board system's operator. Although BBS's have traditionally been the domain of hobbyists, an increasing number of BBS's are connected directly to the Internet, and many BBS's are currently operated by government, educational, and research institutions. See also: Electronic Mail, Internet, Usenet. [Source: NWNET] Campus Wide Information System (CWIS) A CWIS makes information and services publicly available on campus via kiosks, and makes interactive computing available via kiosks, interactive computing systems and campus networks. Services routinely include directory information, calendars, bulletin boards, databases. Malkin Informational [Page 10] RFC 1983 Glossary August 1996 CCIRN See: Coordinating Committee for Intercontinental Research Networks CCITT See: Comite Consultatif International de Telegraphique et Telephonique CERT See: Computer Emergency Response Team checksum A computed value which is dependent upon the contents of a packet. This value is sent along with the packet when it is transmitted. The receiving system computes a new checksum based upon the received data and compares this value with the one sent with the packet. If the two values are the same, the receiver has a high degree of confidence that the data was received correctly. See also: Cyclic Redundancy Check. [Source: NNSC] CIDR See: Classless Inter-domain Routing circuit switching A communications paradigm in which a dedicated communication path is established between two hosts, and on which all packets travel. The telephone system is an example of a circuit switched network. See also: connection-oriented, connectionless, packet switching. Classless Inter-domain Routing (CIDR) A proposal, set forth in RFC 1519, to allocate IP addresses so as to allow the addresses to be aggregated when advertised as routes. It is based on the elimination of intrinsic IP network addresses; that is, the determination of the network address based on the first few bits of the IP address. See also: IP address, network address, supernet. client A computer system or process that requests a service of another computer system or process. A workstation requesting the contents of a file from a file server is a client of the file server. See also: client-server model, server. [Source: NNSC] Malkin Informational [Page 11] RFC 1983 Glossary August 1996 client-server model A common way to describe the paradigm of many network protocols. Examples include the name-server/name-resolver relationship in DNS and the file-server/file-client relationship in NFS. See also: client, server, Domain Name System, Network File System. CNI See: Coalition for Networked Information Coalition for Networked Information (CNI) A consortium formed by American Research Libraries, CAUSE, and EDUCOM (no, they are not acronyms) to promote the creation of, and access to, information resources in networked environments in order to enrich scholarship and enhance intellectual productivity. Comite Consultatif International de Telegraphique et Telephonique ( CCITT) This organization is now part of the International Telecommunications Union and is responsible for making technical recommendations about telephone and data communications systems. Every four years CCITT holds plenary sessions where they adopt new standards; the most recent was in 1992. Recently, the ITU reorganized and CCITT was renamed the ITU-TSS. See also: International Telecommunications Union - Telecommunications Standards Sector. Computer Emergency Response Team (CERT) The CERT was formed by ARPA in November 1988 in response to the needs exhibited during the Internet worm incident. The CERT charter is to work with the Internet community to facilitate its response to computer security events involving Internet hosts, to take proactive steps to raise the community's awareness of computer security issues, and to conduct research targeted at improving the security of existing systems. CERT products and services include 24-hour technical assistance for responding to computer security incidents, product vulnerability assistance, technical documents, and tutorials. In addition, the team maintains a number of mailing lists (including one for CERT Advisories), and provides an anonymous FTP server, at "cert.org", where security-related documents and tools are archived. The CERT may be reached by email at "cert@cert.org" and by telephone at +1-412-268-7090 (24-hour hotline). See also: Advanced Research Projects Agency, worm. congestion Congestion occurs when the offered load exceeds the capacity of a data communication path. Malkin Informational [Page 12] RFC 1983 Glossary August 1996 connection-oriented The data communication method in which communication proceeds through three well-defined phases: connection establishment, data transfer, connection release. TCP is a connection-oriented protocol. See also: circuit switching, connectionless, packet switching, Transmission Control Protocol. connectionless The data communication method in which communication occurs between hosts with no previous setup. Packets between two hosts may take different routes, as each is independent of the other. UDP is a connectionless protocol. See also: circuit switching, connection-oriented, packet switching, User Datagram Protocol. Coordinating Committee for Intercontinental Research Networks (CCIRN) A committee that includes the United States FNC and its counterparts in North America and Europe. Co-chaired by the executive directors of the FNC and the European Association of Research Networks (RARE), the CCIRN provides a forum for cooperative planning among the principal North American and European research networking bodies. See also: Federal Networking Council, RARE. [Source: MALAMUD] core gateway Historically, one of a set of gateways (routers) operated by the Internet Network Operations Center at Bolt, Beranek and Newman (BBN). The core gateway system formed a central part of Internet routing in that all groups must advertise paths to their networks from a core gateway. [Source: MALAMUD] Corporation for Research and Educational Networking (CREN) This organization was formed in October 1989, when Bitnet and CSNET (Computer + Science NETwork) were combined under one administrative authority. CSNET is no longer operational, but CREN still runs Bitnet. See also: Bitnet. [Source: NNSC] cracker A cracker is an individual who attempts to access computer systems without authorization. These individuals are often malicious, as opposed to hackers, and have many means at their disposal for breaking into a system. See also: hacker, Computer Emergency Response Team, Trojan Horse, virus, worm. CRC See: cyclic redundancy check Malkin Informational [Page 13] RFC 1983 Glossary August 1996 CREN See: Corporation for Research and Educational Networking CU-SeeMe Pronnounced "See you, See me," CU-SeeMe is a publicly available videoconferencing program developed at Cornell University. It allows anyone with audio/video capabilites and an Internet connection to videoconference with anyone else with the same capabilities. It also allows multiple people to tie into the same videoconference. CWIS See: Campus Wide Information system Cyberspace A term coined by William Gibson in his fantasy novel Neuromancer to describe the "world" of computers, and the society that gathers around them. [Source: ZEN] Cyclic Redundancy Check (CRC) A number derived from a set of data that will be transmitted. By recalculating the CRC at the remote end and comparing it to the value originally transmitted, the receiving node can detect some types of transmission errors. See also: checksum. [Source: MALAMUD] DANTE A non-profit company founded in July 1993 to help the European research community enhance their networking facilities. It focuses on the establishment of a high-speed computer network infrastructure. DARPA Defense Advanced Research Projects Agency See: Advanced Research Projects Agency Data Encryption Key (DEK) Used for the encryption of message text and for the computation of message integrity checks (signatures). See also: encryption. Data Encryption Standard (DES) A popular, standard encryption scheme. See also: encryption, Pretty Good Privacy, RSA. datagram A self-contained, independent entity of data carrying sufficient information to be routed from the source to the destination Malkin Informational [Page 14] RFC 1983 Glossary August 1996 computer without reliance on earlier exchanges between this source and destination computer and the transporting network. See also: frame, packet. [Source: J. Postel] DCA See: Defense Information Systems Agency DCE Data Circuit-terminating Equipment DCE See: Distributed Computing Environment DDN See: Defense Data Network DDN NIC See: Defense Data Network Network Information Center DECnet A proprietary network protocol designed by Digital Equipment Corporation. The functionality of each Phase of the implementation, such as Phase IV and Phase V, is different. default route A routing table entry which is used to direct packets addressed to networks not explicitly listed in the routing table. [Source: MALAMUD] Defense Data Network (DDN) A global communications network serving the US Department of Defense composed of MILNET, other portions of the Internet, and classified networks which are not part of the Internet. The DDN is used to connect military installations and is managed by the Defense Information Systems Agency. See also: Defense Information Systems Agency. Defense Data Network Network Information Center (DDN NIC) Previously called "The NIC", the DDN NIC's primary responsibility was the assignment of Internet network addresses and Autonomous System numbers, the administration of the root domain, and providing information and support services to the Internet for the DDN. Since the creation of the InterNIC, the DDN NIC performs these functions only for the DDN. See also: Autonomous System, network address, Internet Registry, InterNIC, Network Information Center, Request For Comments. Malkin Informational [Page 15] RFC 1983 Glossary August 1996 Defense Information Systems Agency (DISA) Formerly called the Defense Communications Agency (DCA), this is the government agency responsible for managing the DDN portion of the Internet, including the MILNET. Currently, DISA administers the DDN, and supports the user assistance services of the DDN NIC. See also: Defense Data Network. DEK See: Data Encryption Key DES See: Data Encryption Standard dialup A temporary, as opposed to dedicated, connection between machines established over a phone line (analog or ISDN). See also: Integrated Services Digital Network. Directory Access Protocol X.500 protocol used for communication between a Directory User Agent and a Directory System Agent. [Source: MALAMUD] Directory System Agent (DSA) 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. [Source: RFC1208] Directory User Agent (DUA) 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. [Source: RFC1208] DISA See: Defense Information Systems Agency Distributed Computing Environment (DCE) 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 Digital, IBM and Hewlett Packard. [Source: RFC1208] Malkin Informational [Page 16] RFC 1983 Glossary August 1996 distributed database A collection of several different data repositories that looks like a single database to the user. A prime example in the Internet is the Domain Name System. DIX Ethernet See: Ethernet DNS See: Domain Name System domain "Domain" is a heavily overused term in the Internet. It can be used in the Administrative Domain context, or the Domain Name context. See also: Administrative Domain, Domain Name System. Domain Name System (DNS) The DNS is a general purpose distributed, replicated, data query service. The principal use is the lookup of host IP addresses based on host names. The style of host names now used in the Internet is called "domain name", because they are the style of names used to look up anything in the DNS. Some important domains are: .COM (commercial), .EDU (educational), .NET (network operations), .GOV (U.S. government), and .MIL (U.S. military). Most countries also have a domain. The country domain names are based on ISO 3166. For example, .US (United States), .UK (United Kingdom), .AU (Australia). See also: Fully Qualified Domain Name, Mail Exchange Record. dot address (dotted decimal notation) Dot address refers to the common notation for IP addresses of the form A.B.C.D; where each letter represents, in decimal, one byte of a four byte IP address. See also: IP address. [Source: FYI4] DSA See: Directory System Agent DTE Data Terminal Equipment DUA See: Directory User Agent Malkin Informational [Page 17] RFC 1983 Glossary August 1996 dynamic adaptive routing Automatic rerouting of traffic based on a sensing and analysis of current actual network conditions. NOTE: this does not include cases of routing decisions taken on predefined information. [Source: J. Postel] E1 The basic building block for European multi-megabit data rates, with a bandwidth of 2.048Mbps. See also: T1. E3 A European standard for transmitting data at 57.344Mbps. See also: T3. EARN European Academic and Research Network. See: Trans-European Research and Education Networking Association. EBCDIC See: Extended Binary Coded Decimal Interchange Code Ebone A pan-European backbone service. EFF See: Electronic Frontier Foundation EGP See: Exterior Gateway Protocol Electronic Frontier Foundation (EFF) A foundation established to address social and legal issues arising from the impact on society of the increasingly pervasive use of computers as a means of communication and information distribution. Electronic Mail (email) A system whereby a computer user can exchange messages with other computer users (or groups of users) via a communications network. Electronic mail is one of the most popular uses of the Internet. [Source: NNSC] email See: Electronic mail email address The domain-based or UUCP address that is used to send electronic mail to a specified destination. For example an editor's address Malkin Informational [Page 18] RFC 1983 Glossary August 1996 is "gmalkin@xylogics.com". See also: bang path, mail path, UNIX- to-UNIX CoPy. [Source: ZEN] encapsulation The technique used by layered protocols in which a layer adds header information to the protocol data unit (PDU) from the layer above. For example, in Internet terminology, a packet would contain a header from the physical layer, followed by a header from the datalink layer (e.g. Ethernet), followed by a header from the network layer (IP), followed by a header from the transport layer (e.g. TCP), followed by the application protocol data. [Source: RFC1208] encryption Encryption is the manipulation of a packet's data in order to prevent any but the intended recipient from reading that data. There are many types of data encryption, and they are the basis of network security. See also: Data Encryption Standard. error checking The examination of received data for transmission errors. See also: checksum, Cyclic Redundancy Check. Ethernet A 10-Mb/s standard for LANs, initially developed by Xerox, and later refined by Digital, Intel and Xerox (DIX). All hosts are connected to a coaxial cable where they contend for network access using a Carrier Sense Multiple Access with Collision Detection (CSMA/CD) paradigm. See also: 802.x, Local Area Network, token ring. Ethernet meltdown An event that causes saturation, or near saturation, on an Ethernet. It usually results from illegal or misrouted packets and typically lasts only a short time. See also: broadcast storm. [Source: COMER] Extended Binary Coded Decimal Interchange Code (EBCDIC) A standard character-to-number encoding used primarily by IBM computer systems. See also: ASCII. Exterior Gateway Protocol (EGP) A protocol which distributes routing information to the routers which connect autonomous systems. The term "gateway" is historical, as "router" is currently the preferred term. There is also a routing protocol called EGP defined in RFC 904. See also: Malkin Informational [Page 19] RFC 1983 Glossary August 1996 Autonomous System, Border Gateway Protocol, Interior Gateway Protocol. eXternal Data Representation (XDR) A standard for machine independent data structures developed by Sun Microsystems and defined in RFCs 1014 and 1832. It is similar to ASN.1. See also: Abstract Syntax Notation One. [Source: RFC1208] FARNET A non-profit corporation, established in 1987, whose mission is to advance the use of computer networks to improve research and education. FAQ Frequently Asked Question FDDI See: Fiber Distributed Data Interface Federal Information Exchange (FIX) One of the connection points between the American governmental internets and the Internet. [Source: SURA] Federal Networking Council (FNC) The coordinating group of representatives from those federal agencies involved in the development and use of federal networking, especially those networks using TCP/IP and the Internet. Current members include representatives from DOD, DOE, ARPA, NSF, NASA, and HHS. See also: Advanced Research Projects Agency, National Science Foundation. Fiber Distributed Data Interface (FDDI) A high-speed (100Mb/s) LAN standard. The underlying medium is fiber optics, and the topology is a dual-attached, counter- rotating token ring. See also: Local Area Network, token ring. [Source: RFC1208] file transfer The copying of a file from one computer to another over a computer network. See also: File Transfer Protocol, Kermit, Gopher, World Wide Web. Malkin Informational [Page 20] RFC 1983 Glossary August 1996 File Transfer Protocol (FTP) A protocol which allows a user on one host to access, and transfer files to and from, another host over a network. Also, FTP is usually the name of the program the user invokes to execute the protocol. See also: anonymous FTP. finger A protocol, defined in RFC 1288, that allows information about a system or user on a system to be retrived. Finger also refers to the commonly used program which retrieves this information. Information about all logged in users, as well is information about specific users may be retrieved from local or remote systems. Some sites consider finger to be a security risk and have either disabled it, or replaced it with a simple message. FIX See: Federal Information Exchange flame A strong opinion and/or criticism of something, usually as a frank inflammatory statement, in an electronic mail message. It is common to precede a flame with an indication of pending fire (i.e. FLAME ON!). Flame Wars occur when people start flaming other people for flaming when they shouldn't have. See also: Electronic Mail, Usenet. FLEA See: Four Letter Extended Acronym FNC See: Federal Networking Council Four Letter Extended Acronym (FLEA) A recognition of the fact that there are far too many TLAs. See also: Three Letter Acronym. FQDN See: Fully Qualified Domain Name fragment A piece of a packet. When a router is forwarding an IP packet to a network that has a maximum transmission unit smaller than the packet size, it is forced to break up that packet into multiple fragments. These fragments will be reassembled by the IP layer at the destination host. See also: Maximum Transmission Unit. Malkin Informational [Page 21] RFC 1983 Glossary August 1996 fragmentation The IP process in which a packet is broken into smaller pieces to fit the requirements of a physical network over which the packet must pass. See also: reassembly. frame A frame is a datalink layer "packet" which contains the header and trailer information required by the physical medium. That is, network layer packets are encapsulated to become frames. See also: datagram, encapsulation, packet. freenet Community-based bulletin board system with email, information services, interactive communications, and conferencing. Freenets are funded and operated by individuals and volunteers -- in one sense, like public television. They are part of the National Public Telecomputing Network (NPTN), an organization based in Cleveland, Ohio, devoted to making computer telecommunication and networking services as freely available as public libraries. [Source: LAQUEY] FTP See: File Transfer Protocol Fully Qualified Domain Name (FQDN) The FQDN is the full name of a system, rather than just its hostname. For example, "venera" is a hostname and "venera.isi.edu" is an FQDN. See also: hostname, Domain Name System. FYI For Your Information FYI A subseries of RFCs that are not technical standards or descriptions of protocols. FYIs convey general information about topics related to TCP/IP or the Internet. See also: Request For Comments. gated Gatedaemon. A program which supports multiple routing protocols and protocol families. It may be used for routing, and makes an effective platform for routing protocol research. The software is freely available by anonymous FTP from "gated.cornell.edu". Pronounced "gate-dee". See also: Exterior Gateway Protocol, Open Shortest-Path First, Routing Information Protocol, routed. Malkin Informational [Page 22] RFC 1983 Glossary August 1996 gateway The term "router" is now used in place of the original definition of "gateway". Currently, a gateway is a communications device/program which passes data between networks having similar functions but dissimilar implementations. This should not be confused with a protocol converter. By this definition, a router is a layer 3 (network layer) gateway, and a mail gateway is a layer 7 (application layer) gateway. See also: mail gateway, router, protocol converter. Gopher A distributed information service, developed at the University of Minnesota, that makes hierarchical collections of information available across the Internet. Gopher uses a simple protocol, defined in RFC 1436, that allows a single Gopher client to access information from any accessible Gopher server, providing the user with a single "Gopher space" of information. Public domain versions of the client and server are available. See also: archie, archive site, Prospero, Wide Area Information Servers. GOSIP See: Government OSI Profile Government OSI Profile (GOSIP) A subset of OSI standards specific to U.S. Government procurements, designed to maximize interoperability in areas where plain OSI standards are ambiguous or allow excessive options. hacker A person who delights in having an intimate understanding of the internal workings of a system, computers and computer networks in particular. The term is often misused in a pejorative context, where "cracker" would be the correct term. See also: cracker. header The portion of a packet, preceding the actual data, containing source and destination information. It may also error checking and other fields. A header is also the part of an electronic mail message which precedes the body of a message and contains, among other things, the message originator, date and time. See also: Electronic Mail, packet, error checking. heterogeneous network A network running multiple network layer protocols. See also: DECnet, IP, IPX, XNS, homogeneous network. Malkin Informational [Page 23] RFC 1983 Glossary August 1996 hierarchical routing The complex problem of routing on large networks can be simplified by reducing the size of the networks. This is accomplished by breaking a network into a hierarchy of networks, where each level is responsible for its own routing. The Internet has, basically, three levels: the backbones, the mid-levels, and the stub networks. The backbones know how to route between the mid-levels, the mid-levels know how to route between the sites, and each site (being an autonomous system) knows how to route internally. See also: Autonomous System, Exterior Gateway Protocol, Interior Gateway Protocol, stub network, transit network. High Performance Computing and Communications (HPCC) High performance computing encompasses advanced computing, communications, and information technologies, including scientific workstations, supercomputer systems, high speed networks, special purpose and experimental systems, the new generation of large scale parallel systems, and application and systems software with all components well integrated and linked over a high speed network. [Source: HPCC] High Performance Parallel Interface (HIPPI) An emerging ANSI standard which extends the computer bus over fairly short distances at speeds of 800 and 1600 Mb/s. HIPPI is often used in a computer room to connect a supercomputer to routers, frame buffers, mass-storage peripherals, and other computers. See also: American National Standards Institute [Source: MALAMUD] HIPPI See: High Performance Parallel Interface HTML See: Hypertext Markup Language homogeneous network A network running a single network layer protocol. See also: DECnet, IP, IPX, XNS, heterogeneous network. hop