10BaseT Source: big-lan A variant of IEEE 802.3 which allows stations to be at- tached via twisted-pair cable. 802.x Source: big-lan The set of IEEE standards for the definition of LAN protocols. A story goes that a long time ago, IEEE and ANSI decided that IEEE would get the slow protocols and ANSI would get the fast ones, thus IEEE defined the 802 protocols and ANSI defined FDDI. Presumably IEEE saw limited application for FDDI at the time. 822 See "RFC 822" :-) Source: zen This odd symbol is one of the ways a person can portray "mood" in the very flat medium of computers--by using "smiles". This is `metacommunication', and there are literally hundreds of them, from the obvious to the ob- scure. This particular example expresses "happiness". Don't see it? Tilt your head to the left 90 degrees. Smiles are also used to denote sarcasm. Abstract Syntax Notation One (ASN.1) Source: UG The language used by the OSI protocols for describing abstract syntax. This language is also used to encode SNMP packets. See also: Basic Encoding Rules. abstract syntax Source: rfc1208 A description of a data structure that is independent of machine-oriented structures and encodings. Access Control List (ACL) Source: malamud A security feature that allows security on objects to be specified as a list of permitted actions for partic- August 2, 1992 - 2 - ular lists of users. Used by NFS...(fix def) ACK See "Acknowledgment" acknowledgment (ACK) Source: nnsc A type of message sent to indicate that a block of data arrived at its destination without error. See also: NAK. ACL See "Access Control List" AD See "Administrative Domain" address mask Source: rfc1208 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. Address Resolution Protocol (ARP) Source: Used to dynamically discover the lowlevel physical net- work hardware address that corresponds to the high lev- el IP address for a given host. ARP is limited to phy- sical network systems that support broadcast packets that can be heard by all hosts on the network. See also "proxy ARP." address resolution Source: Conversion of an Internet address to the corresponding physical address. address space Source: malamud A collection of addresses that form a unified collec- tion such as an internetwork. August 2, 1992 - 3 - address Source: fyi4 There are two separate uses of this term in internet networking: "electronic mail address" and "internet ad- dress". An electronic mail address is the string of characters that you must give an electronic mail pro- gram to direct a message to a particular person. See "Internet address" for its definition. Administrative Domain (AD) Source: malamud A group of hosts, routers, and networks operated and managed by a single organization. Routing within an administrative domain is based on a consistent techni- cal plan. An administrative domain is viewed from the outside, for purposes of routing, as a cohesive entity, of which the internal structure is unimportant. Infor- mation passed by other administrative domains is trust- ed less than information from one's own administrative domain. [RFC 1136] Advanced Research Projects Agency Network (ARPANET) Source: fyi4 A pioneering long haul network funded by ARPA. 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. agent Source: rfc1208 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 Network Manage- ment Station or Directory User Agent alias Source: malamud A name that is translated into another name. A DNS soft link is an example of an alias. American National Standards Institute (ANSI) Source: nnsc August 2, 1992 - 4 - This organization is responsible for approving U.S. standards in many areas, including computers and com- munications. Standards approved by this organization are often called ANSI standards (e.g., ANSI C is the version of the C language approved by ANSI). ANSI is a member of the International Standards Organization (ISO). American Standard Code for Information Interchange (ASCII) Source: malamud A standard character set that assigns an octal sequence to each letter, number, and selected control charac- ters. The other major encoding standard is EBCDIC. Anonymous FTP Source: 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 publically accessible files on the remote system. ANSI See "American National Standards Institute" API See "Application Program Interface" Appletalk Source: nnsc A networking protocol developed by Apple Computer for communication between Apple Computer products and other computers. This protocol is independent of what net- work it is layered on. Current implementations exist on Localtalk (a 235-kilobit/second local area network (LAN)), and Ethertalk (a 10-megabit/second local area network). application layer Source: malamud The top layer of the network protocol stack. The ap- plication layer is concerned with the semantics of work. For example, getting a certain record from a file by key value on a foreign node is an application August 2, 1992 - 5 - layer concern. How to represent that data and how to reach the foreign node are issues for lower layers of the network. Application Program Interface (API) Source: rfc1208 A set of calling conventions defining how a service is invoked through a software package. application Source: malamud A program that performs functions for a user. Order entry system or word processors are both examples of applications. archie Source: zen A service which provides lookups for packages in a da- tabase of the offerings of countless of anonymous FTP sites. archive site Source: Definition: 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 Inter- change" ASN.1 See "Abstract Syntax Notation One" assigned numbers Source: malamud August 2, 1992 - 6 - Those numbers officially assigned as part of the Inter- net standards. Asynchronous Transfer Mode (ATM) Source: malamud Method for dynamic allocation of bandwidth on a cell basis. Also known as fast packet. ATM See "Asynchronous Transfer Mode" authentication Source: malamud The function of verifying the identity of a person or process. Autonomous System (AS) Source: nnsc A collection of networks controlled by one administra- tive authority. The gateways within this system are expected to trust one another and to share and update routing information (see route) among themselves by any mutually agreeable protocol. A core gateway must also be designated to share routing information with other autonomous systems via EGP. backbone Source: rfc1208 The primary connectivity mechanism of a hierarchical distributed system. All systems which have connectivi- ty to an intermediate system on the backbone are as- sured 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. bandwidth Source: orig Technically, the difference, in Hertz (Hz), between the highest and lowest frequencies of a transmission chan- nel. However, as typically used, the amount of data that can be sent through a given communications cir- cuit. August 2, 1992 - 7 - bang path Source: orig A series of machine names used to direct electronic mail from one user to another, typically by specifying an explicit UUCP path for the mail to be routed through. baseband Source: nnsc A transmission medium through which digital signals are sent without complicated frequency shifting. In gen- eral, only 1 communication channel is provided at a time on a baseband system. Ethernet is a baseband net- work. Basic Encoding Rules (BER) Source: nnsc 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 syn- tax description language, not the encoding technique. BBS See "Bulletin Board System" BER See "Basic Encoding Rules" Berkeley Source Distribution (BSD) Source: nnsc This acronym is used to describe the versions of the UNIX operating system and its utilities developed and distributed by the University of California at Berke- ley. "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 has been the ancestor of many commercial UNIX implementations. BGP See "Border Gateway Protocol" big-endian Source: rfc1208 August 2, 1992 - 8 - 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. Birds Of a Feather (BOF) Source: orig A Birds Of a Feather (flocking together) is an informal discussion group. In the IETF, a BOF is an meet once, unchartered working group. BOFs are often used to determine if there is sufficient interest to form a working group. BOF See "Birds Of a Feather" BOOTP Source: malamud Bootstrap Protocol. Protocol described in RFC 951 used for booting diskless nodes. Border Gateway Protocol (BGP) Source: rfc1105 The Border Gateway Protocol (BGB) is an inter- autonomous system routing protocol. It is built on ex- perience gained with EGP as defined in RFC 904 [1] and EGP usage in the NSFNET Backbone as described in RFC 1092 [2] and RFC 1093 [3]. bounce Source: zen The return of a piece of mail because of an error in its delivery. bridge Source: big-lan A network "relay" which reads, buffers, and sends data to relay it from one data link to another, but makes the two data links appear as one to levels higher than the data link layer. broadband Source: orig August 2, 1992 - 9 - Transmission equipment and/or media capable of support- ing a wide range of frequencies. Can carry multiple signals at the same time by dividing the total capacity of the media into multiple (independent) bandwidth channels, where each channel operates only on a specfic range of frequencies and therefore does not interfere with other channels. broadcast storm Source: An incorrect packet broadcast on a network that causes most hosts to respond all at once, typically with wrong answers that start the process over again.hacker broadcast Source: rfc1208 A packet delivery system where a copy of a given packet is sent simultaneously to all hosts attached to the network. brouter Source: malamud Bridge/router. A device that forwards messages between networks at both network and data link levels. BSD See "Berkeley Software Distribution" BTW "By The Way" Bulletin Board System (BBS) Source: hacker An electronic bulletin board system; that is, a message database where people can log in and leave broadcast messages for others grouped (typically) into topic groups. Thousands of local BBS systems are in opera- tion throughout the U.S., typically run by amateurs for fun out of their homes on MS-DOS boxes with a single modem line each. Fans of USENET and Internet or the big commercial timesharing bboards such as CompuServe and GEnie tend to consider local BBSes the low-rent district of the hacker culture, but they serve a valu- able function by knitting together lots of hackers and users in the personal-micro world who would otherwise be unable to exchange code at all. August 2, 1992 - 10 - Campus Wide Information system (CWIS) Source: orig ??? CCIRN See "Coordinating Committee for Intercontinental Research Networks" CCITT See "Comite Consultatif International de Telegraphique et Telephonique" checksum Source: nnsc A computed symbol whose value is dependent upon the en- tire contents of a message or packet. This value is usually sent along with the message 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. circuit switching Source: orig ??? client Source: nnsc A computer system or process that requests a service of another computer system or process. A workstation re- questing the contents of a file from a file server is a client of the file server. The session layer is a client of the transport layer. client-server model Source: rfc1208 A common way to describe network 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. CNI August 2, 1992 - 11 - See "Coalition for Networked Information" Coalition for Networked Information (CNI) Source: orig ??? Comite Consultatif International de Telegraphique et Telephonique (CCITT) Source: nnsc This organization is part of the United National Inter- national Telecommunications Union (ITU) and is respon- sible for making technical recommendations about tele- phone and data communications systems. X.25 is an ex- ample of a CCITT recommendation. Every four years CCITT holds plenary sessions where they adopt new stan- dards; a session is planned for 1992. congestion Source: malamud Too much traffic for a given circuit. connection-oriented Source: rfc1208 The model of interconnection in which communication proceeds through three well-defined phases: connection establishment, data transfer, connection release. Ex- amples: X.25, Internet TCP and OSI TP4, ordinary tele- phone calls. connectionless Source: rfc1208 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. Consortium for Research and Education Network (CREN) Source: comer The name of the organization that resulted when BITNET and CSNET merged. August 2, 1992 - 12 - Coordinating Committee for Intercontinental Research Net- works (CCIRN) Source: malamud 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 pro- vides a forum for cooperative planning among the prin- cipal North American and European research networking bodies. core gateway Source: malamud 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. Corporation for Research and Educational Networking (CREN) Source: nnsc This organization was formed in October 1989, when BIT- NET and CSNET were combined under one administrative authority. cracker Source: orig ??? CRC See "cyclic redundancy check" CREN See "The Corporation for Research and Educational Net- working" CWIS See "Campus Wide Information system" Cyberspace Source: zen A term coined by William Gibson in his fantasy novel Neuromancer to describe the "world" of computers, and the society that gathers around them. August 2, 1992 - 13 - Cyclic Redundancy Check (CRC) Source: malamud 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 transmit- ted, the receiving node can detect some types of transmission errors. DARPA See "Defense Advanced Research Projects Agency" Data Encryption Key (DEK) Source: malamud Used for encryption of message text and (with certain choices among a set of alternative algorithms) for com- putation of message integrity check (MIC) quantities. DEKs are generated individually for each transmitted message; no predistribution of DEKs is needed to sup- port privacy-enhanced message transmission. [RFC 1113] Data Encryption Standard (DES) Source: malamud One type of encryption scheme. <> datagram Source: fyi4 A self-contained, independent entity of data carrying sufficient information to be routed from the source to the destination data terminal equipment without reli- ance on earlier exchanges between this source and des tination data terminal equipment and the transporting network. DCE "Data Circuit-terminating Equipment" DCE See "Distributed Computing Environment" DDN NIC See "Defense Data Network Network Information Center" DDN See "Defense Data Network" August 2, 1992 - 14 - DECnet Source: sura A proprietary network protocol designed by Digital Equipment Corporation. Functionality of each Phase of the implementation <> default route Source: malamud A routing table entry which is used to direct any data addressed to any network numbers not explicitly listed in the routing table. Defense Advanced Research Projects Agency (DARPA) Source: nnsc An agency of the U.S. Department of Defense responsible for the development of new technology for use by the military. DARPA (formerly known as ARPA) was responsi- ble for funding much of the development of the Internet we know today <>. The New York Times business section called DARPA "America's answer to Japan's MITI." Defense Data Network (DDN) Source: nnsc A worldwide operational communications network serving the US Department of Defense composed of << >> MILNET and other portions of the Internet. The DDN is used to connect military installations. It is run by the De- fense Communications Agency (DCA). Defense Data Network Network Information Center (DDN NIC) Source: orig The DDN NIC's primary responsibility is the assignment of Internet addresses and Administrative Domain numbers. It is also a primary repository for RFCs. See also: Internet address, Administrative Domain, Re- quest For Comments. Defense Information Systems Agency (DISA) Source: fyi4 Formerly called DCA, this is the government agency August 2, 1992 - 15 - responsible for installing the Defense Data Network (DDN) portion of the Internet, including the MILNET lines and nodes. Currently, DISA administers the DDN, and supports the user assistance services of the DDN NIC. DES See "Data Encryption Standard" dialup Source: sura A <> connection between machines <> Directory Access Protocol Source: malamud X.500 protocol used for communication between a Direc- tory User Agent and a Directory System Agent. Directory System Agent (DSA) Source: rfc1208 The software that provides the X.500 Directory Service for a portion of the directory information base. Gen- erally, each DSA is responsible for the directory in- formation for a single organization or organizational unit. Directory User Agent (DUA) Source: rfc1208 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. DISA See "Defense Information Systems Agency" Distributed Computing Environment (DCE) Source: rfc1208 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 August 2, 1992 - 16 - the Open Software Foundation (OSF), a consortium led by HP, DEC, and IBM. See ONC <> distributed database Source: malamud Looks to the user like a single database but is in fact a collection of several different data repositories. DNS See "Domain Name System" Domain Name System (DNS) Source: UG The Domain Name System is a mechanism used in the In- ternet for translating names of host computers into ad- dresses. The DNS also allows host computers not directly on the Internet to have registered names in the same style. Some important domains are: .COM (com- mercial), .EDU (educational), .NET (network opera- tions), .GOV (U.S. government), .MIL (U.S. military), and .US, .UK, etc (national) domain Source: rfc1208 <> Syn- tactically, an Internet domain name consists of a se- quence of names (labels) separated by periods (dots), e.g., "tundra.mpk.ca.us." dot address (dotted decimal notation) Source: fyi4 Dot address refers to the common notation for Internet addresses of the form A.B.C.D; where each letter represents, in decimal, one byte of the four byte IP address. DS1 Source: <> DS3 Source: August 2, 1992 - 17 - <> DSA See "Directory System Agent" DTE "Data Terminal Equipment" DUA See "Directory User Agent" Dynamic Adaptive Routing Source: fyi4 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. EBCDIC See "Extended Binary Coded Decimal Interchange Code" Ebone Source: A pan-European backbone service. EFF See "Electronic Frontier Foundation" EFLA See "Extended Four Letter Acronym" EGP See "Exterior Gateway Protocol" Electronic Frontier Foundation (EFF) Source: A foundation established to address social and legal issues arising from the impact on society of the in- creasingly pervasive use of computers as a means of communication and information distribution. Electronic Mail (email) Source: nnsc 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 August 2, 1992 - 18 - most popular uses of the Internet. email address Source: zen The UUCP or domain-based address that is used to send electronic mail to a specified destination. For exam- ple the author's address is brendan@cs.widener.edu. email See "Electronic mail" encapsulation Source: rfc1208 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 packet 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. Ethernet meltdown Source: comer An event that causes saturation or near saturation on an Ethernet. It usually results from illegal or mis- routed packets and typically lasts only a short time. Ethernet Source: nnsc <<& malamud>> A 10-megabit/second standard for local area networks (LANs), initially developed by Xerox, and later refined by Xerox, DEC and Intel. All hosts are connected to a coaxial cable where they contend for network access ac- cording to the CSMA/CD protocol. <> Extended Binary Coded Decimal Interchange Code (EBCDIC) Source: malamud A character code scheme used in IBM environments.See also ASCII. August 2, 1992 - 19 - Extended Four Letter Acronym (EFLA) Source: Keith Morgan A recognition of the fact that there are far too many TLAs. See also: Three Letter Acronym. Exterior Gateway Protocol (EGP) Source: malamud A protocol <> distributes routing information to the routers and gateways which interconnect networks. There is also a routing protocol called EGP defined in RFC <<904>> eXternal Data Representation (XDR) Source: rfc1208 A standard for machineindependent data structures developed by Sun Microsystems. Similar to ASN.1. FAQ "Frequently Asked Question" FARNET See "Federation of American Research NETworks" FDDI See "Fiber Distributed Data Interface" Federal Information Exchange (FIX) Source: sura One of the connection points between the American govermental internets and the Internet. Federal Networking Council (FNC) Source: comer 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 connected Internet. The FNS coordi- nates research and engineering. Current members in- clude representatives from DOD, DOE, DARPA, NSF, NASA, and HHS. Fiber Distributed Data Interface (FDDI) Source: rfc1208 August 2, 1992 - 20 - An emerging high-speed (100Mb/sec) 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 "ca- ble." File Transfer Protocol (FTP) Source: nnsc A protocol permitting a user on one Internet host to access and transfer files to another host over a net- work such as the Internet. FTP is usually the name not only of the protocol, but also of the program the user invokes to execute the protocol (e.g., "ftp host.bbn.com"). This protocol is layered on top of TCP, which is layered on top of IP. FTP is available on several operating systems. You can use the ftp com- mand to copy computer files that contain a variety of information, such as software, documentation, or maps. finger Source: hacker A program that displays a particular user or all users logged on the system or a remote system. Typically shows full name, last login time, idle time, terminal line, and terminal location (where applicable). It may also display a plan file left by the user. FIX See "Federal Information Exchange" flame Source: rfc1208 To express strong opinion and/or criticism of some- thing, usually as a frank inflammatory statement in an electronic mail message. FNC See "Federal Networking Council" For Your Information (FYI) Source: comer A subset of RFCs that are not technical standards or descriptions of protocols. FYIs convey general infor- maton about topics related to TCP/IP or the connected Internet. See also: Request For Comments, STD. August 2, 1992 - 21 - FQDN See "Fully Qualified Domain Name" fragment Source: nnsc A piece of a packet. When a gateway is forwarding a maximum size IP packet to a network that has a smaller maximum packet size, it is forced to break up that packet into multiple fragments for transport on the new network. These fragments will be reassembled by the IP layer at the destination host. fragmentation Source: rfc1208 The process in which an IP datagram is broken into smaller pieces to fit the requirements of a given phy- sical network. The reverse process is termed reassem- bly. frame Source: malamud A series of bytes of data encapsulated with a header. The data link layer sends frames of data back and forth. Frame is often used interchangeably with pack- et, although technically a packet refers to data from the network layer of the protocol stack. A packet is thus usually contained inside a frame. FTP See "File Transfer Protocol" Fully Qualified Domain Name (FQDN) Source: zen The FQDN is the full site name of a system, rather than just its hostname. For example, the system lisa at Widener University has a FQDN of lisa.cs.widener.edu. FYI See "For Your Information" gated Source: orig ??? August 2, 1992 - 22 - gateway Source: nnsc There are two somewhat conflicting definitions of gate- way, both used in networking. The first is a computer used to connect together one or more networks. This computer is seen as a host by the networks to which it is connected, but is capable of forwarding packets from one network to another. Gateways are also responsible for providing and receiving routing information to oth- er gateways in the Internet so that they will know the best routes for sending packets between networks. One may think of a gateway as a packet switch with whole computer networks as its communication links. Some gateways are capable of routing packets from several different protocol suites so that a single gateway can handle TCP/IP and DECnet protocols, for instance. The second meaning of gateway is the system that translates an entire stack of protocols, e.g., translates TCP/IP- style mail to ISO-style mail. Gopher Source: ??? The Internet Gopher is a distributed document delivery service. It allows a neophyte user to access various types of data residing on multiple hosts in a seamless fashion. This is accomplished by presenting the user a hierarchical arrangement of documents and by using a client-server communications model. In addition to browsing through hierarchies of documents, gopher users can submit queries to gopher search servers. The search servers typically have full-text indexes for a set of gopher documents; the responce to a query is a list of documents that matched the search criteria. GOSIP See "Government OSI Profile" Government OSI Profile Source: big-lan A subset of OSI standards specific to US Government procurements, designed to maximize interoperability in areas where plain OSI standards are ambiguous or allow options. Theoretically, required of all US Government networking procurements since mid-1990. hacker Source: orig August 2, 1992 - 23 - ??? header Source: zen The portion of a packet, preceding the actual data, containing source and destination addresses and error- checking fields. Also, can be used to describe the part of a message or news article that precedes the body of the message or article. heterogeneous network Source: malamud A network consisting of different network protocols or kinds of computers. A network combining SNA and DNA protocols using an SNA gateway to connect the two is a heterogeneous network. hierarchical routing Source: malamud Routing based on domains. Interdomain routers are responsible only for getting data to the right domain. There, an intradomain router takes responsibility for routing within the domain. High Performance Parallel Interface (HIPPI) Source: malamud An emerging ANSI standard which extends the computer bus over fairly short distances at speeds of 800 and 1600 Mbps. HIPPI is often used in a computer room to connect a supercomputer to routers, frame buffers, mass-storage peripherals, and other computers. HIPPI See "High Performance Parallel Interface" hop Source: malamud A term used in routing. A hop is one data link. A path to the final destination on a net is a series of hops away from the origin. Each hop has a cost associ- ated with it, allowing the calculation of the least cost path. host address August 2, 1992 - 24 - Source: fyi4 The part of an internet address that designates which node on the (sub)network is being addressed. host Source: nnsc A computer that allows users to communicate with other host computers on a network. Individual users communi- cate by using application programs, such as electronic mail, TELNET and FTP. hostname Source: zen The name given to a machine. See also: Fully Qualified Domain Name. hub Source: malamud A device connected to several other devices. In ARCnet, a hub is used to connect several computers to- gether. In a message handling service, a hub is used for the transfer of messages across the network. IAB See "Internet Architecture Board" IANA See "Internet Assigned Numbers Authority" ICMP See "Internet Control Message Protocol" IEEE 802 See "802.x" IEN See "Internet Engineering Notes" IESG See "Internet Engineering Steering Group" IETF See "Internet Engineering Task Force" IGP See "Interior Gateway Protocol." August 2, 1992 - 25 - IMHO "In My Humble Opinion" IMR See "Internet Monthly Report" Integrated Services Digital Network (ISDN) Source: rfc1208 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 ser- vices as well as voice connections through a single "wire." The standards that define ISDN are specified by CCITT. Interior Gateway Protocol (IGP) Source: malamud The generic term applied to any protocol used to pro- pagate network reachability and routing information within an autonomous system. Although there is no In- ternet standard IGP, RIP is among the most popular. Intermediate System (IS) Source: malamud An OSI system that performs routing and relaying func- tions in order to provide paths between end systems. Intermediate systems have no functionality above the network layer (although a practical realization of an OSI router will have some amount of end system func- tionality for network management functions, among other things). Basically equivalent to an Internet Router. [RFC 1136] Intermediate System-Intermediate System (IS-IS) Source: malamud An OSI routing protocol for Intermediate System to In- termediate System communication. International Organization for Standardization (ISO) Source: orig ??? internet address August 2, 1992 - 26 - Source: nnsc A thirty-two-bit number that uniquely identifies an In- ternet host. This address is typically represented in eight-bit numbers (octets) separated by dots, e.g., 128.89.1.132. An Internet address consists of a net- work number and a host number, and may be a class A, B, or C address. A class A network address is formatted as N.H.H.H., providing seven bits of network number and twenty-four bits of host number (e.g., 26.0.0.117 indi- cates host 117 on net 26). A Class B network address is formatted as N.N.H.H., providing fourteen bits of network number and sixteen bits of host number (e.g., 128.89.1.132). A Class C network address is formatted as N.N.N.H., providing twenty-two bits of network number and eight bits of host address (e.g., 192.1.14.28 indicates host 28 on network number 192.1.14). Internet Architecture Board (IAB) Source: rfc1208 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. Previously, "IAB" stood for Internet Activities Board. Internet Assigned Numbers Authority (IANA) Source: orig ??? Internet Control Message Protocol (ICMP) Source: fyi4 ICMP is an extension to the Internet Protocol. It al- lows for the generation of error messages, test packets and informational messages related to IP. internet draft Source: ??? A preliminary version of an RFC. Internet Engineering Notes (IEN) Source: ??? August 2, 1992 - 27 - A series of reports pertinent to the Internet. IENs were published in parallel to RFCs and are no longer active. Internet Engineering Steering Group (IESG) Source: malamud The governing body of the Internet Engineering Task Force. Internet Engineering Task Force (IETF) Source: fyi4 The IETF is a large open community of network designers, operators, vendors, and researchers whose purpose is to coordinate the operation, management and evolution of the Internet, and to resolve short-range and mid-range protocol and architectural issues. It is a major source of proposed protocol standards which are submitted to the Internet Activities Board for final approval. The IETF meets three times a year and exten- sive minutes of the plenary proceedings are issued. Internet Monthly Report (IMR) Source: ??? Published monthly, the purpose of the Internet Monthly Reports is to communicate to the Internet Research Group the accomplishments, milestones reached, or prob- lems discovered by the participating organizations. Internet number See "Internet address" Internet Protocol (IP) Source: comer The Internet standard protocol that defines the Inter- net datagram as the unit of information passes across the Internet and provides the basis for the Internet connectionless, best-effort packet delivery service. It is derived from the datagram protocol defined in RFC 791. Internet Relay Chat (IRC) Source: hacker A world-wide "party line" network that allows one to converse with others in real time. IRC is structured August 2, 1992 - 28 - as a network of servers, each of which accepts connec- tions from client programs, one per user. The IRC com- munity and the USENET and MUD communities overlap to some extent, including both hackers and regular folks who have discovered the wonders of computer networks. Some USENET jargon has been adopted on IRC, as have some conventions such as emoticons. There is also a vigorous native jargon, represented in this lexicon by entries marked `[IRC]'. Internet Research Task Force (IRTF) Source: malamud The IRTF, one of the task forces of the IAB, is a com- munity of network researchers, generally with an Inter- net focus. The work of the IRTF is governed by its In- ternet Research Steering Group (IRSG). The group responsible for research and development of the Inter- net protocol suite. Internet Research Task Force Steering Group (IRSG) Source: malamud The governing body of the Internet Research Task Force. Internet Society (ISOC) Source: ??? A nonprofit organization that fosters the voluntary in- terconnection of computer networks into a global research and development communications and information infrastructure. internet Source: malamud A collection of networks connected together with gate- ways and routers. An internet is a collection of com- puter networks based on the same network protocols. An internet functions as though the entire collection was one large, virtual network. Internet Source: rfc1208 (note the capital "I") The largest internet in the world consisting of large national backbone nets (such as MILNET, NSFNET, and CREN) and a myriad of regional and local campus networks all over the world. The In- August 2, 1992 - 29 - ternet uses the Internet Protocol suite. To be on the Internet you must have IP connectivity, i.e., be able to reach other systems on remote networks with regular IP packets (e.g. Telnet or "ping" packets). Networks with only email connectivity are not classified as be- ing on the Internet. Internetwork Packet eXchange (IPX) Source: ??? Novell's protocol used by Netware. Utilizes part of XNS. A router with "IPX routing" purports to intercon- nect LANs so that Novell Netware clients & servers can talk through the router. interoperability Source: orig The ability of software and hardware on multiple machines from multiple vendors to communicate meaning- fully. IP address Source: orig The 32-bit address assigned to hosts that want to par- ticipate in the Internet using TCP/IP. IP datagram See "datagram" IP See "Internet Protocol" IPX See "Internetwork Packet eXchange" IRC See "Internet Relay Chat" IRSG See "Internet Research Task Force Steering Group" IRTF See "Internet Research Task Force" IS See "Intermediate System" IS-IS See "Intermediate System-Intermediate System" August 2, 1992 - 30 - ISDN See "Integrated Services Digital Network" ISO Development Environment (ISODE) Source: orig Software that allows OSI services to use a TCP-based network. Pronounced eye-so-dee-eee. ISO See "International Standards Organization" ISOC See "Internet Society" ISODE See "ISO Development Environment" KA9Q Source: rfc1208 A popular implementation of TCP/IP and associated pro- tocols for amateur packet radio systems. Kerberos Source: malamud A component of MIT's Project Athena. Kerberos is the security system, based on symetric key cryptography. Contrast with the RSA public key cryptography tech- niques. Kermit Source: malamud A popular file transfer protocol developed by Columbia University. Because Kermit runs in most operating en- vironments, it provides an easy method of file transfer. LAN See "Local Area Network" layer Source: orig Comunication networks for computers may be organized as a set of more or less independent protocols, each in a different layer (also called level). The lowest layer August 2, 1992 - 31 - governs direct host-to-host communication between the hardware at different hosts; the highest consists of user applications. Each layer builds on the layer beneath it. For each layer, programs at different hosts use protocols appropriate to the layer to commun- icate with each other. TCP/IP has five layers of pro- tocols, and OSI has seven. The advantages of different layers of protocols is that the methods of passing in- formation from one layer to another is specified clear- ly as part of the protocol suite, and changes within a protocol layer are prevented from affecting the other layers. This greatly simplifies the task of designing and maintaining communication programs. Listserv Source: orig An automated mailing list distribution system original- ly designed for the Bitnet/EARN network. See also: mail exploder. little-endian Source: rfc1208 A format for storage or transmission of binary data in which the least significant byte (bit) comes first. See also: big-endian. LLC See "Logical Link Control" Local Area Network (LAN) Source: nnsc A data network intended to serve an area of only a few square kilometers or less. Because the network is known to cover only a small area, optimizations can be made in the network signal protocols that permit data rates in the 10 Mbps to 100Mbps range today. Wide-area communication is accomplished by connecting LANs to- gether via metropolitan area networks (MANs) or wide- area networks (WANs). Both Ethernet and FDDI are local area networks. Logical Link Control (LLC) Source: malamud The upper portion of the data link layer, defined in the IEEE 802.2 standard. The logical link control layer presents a uniform interface to the user of the August 2, 1992 - 32 - data link service, usually a network layer. Underneath the LLC sublayer of the data link layer is a media ac- cess control sublayer. The MAC sublayer is responsible for taking a packet of data from the LLC and submitting it to the particular data link being used (such as Eth- ernet or token ring). MAC address Source: malamud The hardware address of a device connected to a shared media (e.g. Ethernet). MAC See "Media Access Control" Mail Bridge Source: nnsc A mail gateway that forwards electronic mail between two or more networks while ensuring that the messages it forwards meet certain administrative criteria. A mail bridge is simply a specialized form of mail gate- way that enforces an administrative policy with regard to what mail it forwards. Mail Exchange Record (MX Record) Source: malamud A DNS resource record type indicating which host can handle mail for a particular domain. mail exploder Source: rfc1208 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 Source: rfc1208 A machine that connects two or more electronic mail systems (especially dissimilar mail systems on two dif- ferent networks) and transfers messages between them. Sometimes the mapping and translation can be quite com- August 2, 1992 - 33 - plex, 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. mail path Source: orig A series of machine names used to direct electronic mail from one user to another. This system of email addressing has been used primarily in UUCP networks which are trying to eliminate its use altogether. See also: bang path. mail relay Source: ??? mailing list Source: zen A possibly moderated discussion group, distributed via email from a central computer maintaining the list of people involved in the discussion. See also: Electron- ic Mail, listserv. MAN See "Metropolitan Area Network" Management Information Base (MIB) Source: big-lan The set of parameters an SNMP management station can query or set in an SNMP agent (e.g. router). Standard, minimal MIBs have been defined (MIB I, MIB II), and vendors often have custom entries. In theory, any SNMP manager can talk to any SNMP agent with a properly de- fined MIB. Martian Source: rfc1208 Humorous term applied to packets that turn up unexpect- edly on the wrong network because of bogus routing en- tries. Also used as a name for a packet which has an altogether bogus (non-registered or ill-formed) Inter- net address. August 2, 1992 - 34 - Maximum Transmission Unit (MTU) Source: rfc1208 The largest possible unit of data that can be sent on a given physical medium. Example: The MTU of Ethernet is 1500 bytes. See also: fragmentation. Media Access Control (MAC) Source: malamud The bottom half of the ISO data link layer. See also Logical Link Control. Metropolitan Area Network (MAN) Source: nnsc A data network intended to serve an area approximating that of a large city. Such networks are being imple- mented by innovative techniques such as running fiber cables through subway tunnels. A popular example of a MAN is SMDS. See also: Swithed Multimegabit Data Ser- vice. MIB See "Management Information Base" MIME See "Multipurpose Internet Mail Extensions" MTU See "Maximum Transmission Unit" multicast Source: rfc1208 A special form of broadcast where copies of the packet are delivered to only a subset of all possible destina- tions. See broadcast. multihomed host Source: malamud An host which has more than one connection to the net- work. The host may send and receive data over any of the links but will not route traffic for other nodes. Multipurpose Internet Mail Extensions (MIME) Source: orig August 2, 1992 - 35 - An extension to Internet email which provides the abil- ity to transfer non-textual data, such as graphics, au- dio and fax. See also: Electronic Mail MX Record See "Mail Exchange Record" NAK See "Negative Acknowledgment" name resolution Source: rfc1208 The process of mapping a name into the corresponding address. See also: Domain Name System. namespace Source: malamud A commonly distributed set of names in which all names are unique. National Institute of Standards and Technology (NIST) Source: malamud United States governmental body that provides assis- tance for standards-making. Formerly the National Bureau of Standards. National Research and Education Network (NREN) Source: comer The planned successor to the connected Internet that will provide high-speed access to scientific and educa- tional institutions. National Science Foundation (NSF) Source: orig A government agency whose purpose is to promote the ad- vancement of science. NSF funds science researchers, scientific projects, and infrastructure to improve the quality of scientific research. The NSFNET, funded by NSF, is an essential part of academic and research com- munications. It is a highspeed "network of networks" which is hierarchical in nature. At the highest level, it is a backbone network currently comprising 16 nodes connected to a 45Mbps facility which spans the con- tinental United States. Attached to that are mid-level August 2, 1992 - 36 - networks and attached to the mid-levels are campus and local networks. NSFNET also has connections out of the U.S. to Canada, Mexico, Europe, and the Pacific Rim. The NSFNET is part of the Internet. Negative Acknowledgment (NAK) Source: UG Response to receipt of a corrupted packet of informa- tion. See also acknowledgement. netiquette Source: zen A pun on "etiquette"; proper behaviour on The Net. Netnews See "USENET" Network Address Source: nnsc A number or group of numbers that uniquely specifies a host on a network. For example 128.89.1.178 is the network address for nnsc.nsf.net. Also informally, an electronic mail address. For example, nnsc@nnsc.nsf.net is the network address for the NSF Network Service Center (NNSC). Network File System (NFS) Source: nnsc This acronym describes a protocol developed by Sun Mi- crosystems to allow a computer system to access files over a network as if they were on its local disks. This protocol has been incorporated in products by more than two hundred companies, and is now a de facto In- ternet standard. Network Information Center (NIC) Source: rfc1208 Originally there was only one, located at SRI Interna- tional and tasked to serve the ARPANET (and later DDN) community. Today, there are many NICs, operated by lo- cal, regional, and national networks all over the world. Such centers provide user assistance, document service, training, and much more. August 2, 1992 - 37 - Network Information Services (NIS) Source: orig A set of services, generally provided by a NIC, to as- sist users in using the network. See also: Network In- formation Center. network meltdown Source: hacker A state of complete network overload; the network equivalent of thrashing. This may be induced by a Chernobyl packet. See also: broadcast storm. Network News Transfer Protocol (NNTP) Source: Definition: network number Source: fyi4 The part of an internet address which designates the network to which the addressed node belongs. Network Operations Center (NOC) Source: nnsc A location from which the operation of a network or in- ternet is monitored. This center also usually serves as a clearinghouse for problems and efforts to resolve those problems. Network Time Protocol (NTP) Source: nnsc A protocol built on top of TCP (see TCP/IP) that as- sures accurate local time-keeping with reference to ra- dio and atomic clocks located on the INternet. This protocol is capable of synchronizing distributed clocks within milliseconds over long time periods. Network Source: nnsc A computer network is a group of computers that can communicate electronically. Networks can be composed August 2, 1992 - 38 - of computers in a single building (Local Area Networks or LANs), or computers thousands of miles apart (Wide Area Networks or WANs). The Internet is a worldwide collection of computer networks that can intercommuni- cate. The system manager and computer center staff at your site can provide information about your local net- work. NFS See "Network File System" NIC.DDN.MIL Source: Definition: NIS See "Network Information Services" NIST See "National Institute of Standards and Technology" NNTP See "Network News Transfer Protocl" NOC See "Network Operations Center" Nodal Switching System (NSS) Source: malamud Main routing nodes in the NSFnet backbone. Node Source: csu A computer that is attached to a netowrk; also called a host. NREN See "National Research and Education Network" NSF See "National Science Foundation" NSS See "Nodal Switching System" NTP See "Network Time Protocol" August 2, 1992 - 39 - OCLC See "Online Computer Library Catalog" octet Source: orig An octet is 8 bits; this term is used in networking (rather than byte) because some systems have bytes that are not 8 bits long. Open Shortest-Path First Interior Gateway Protocol (OSPF) Source: fyi4 A proposed replacement for RIP. It addresses some problems of RIP and is based upon principles that have been well-tested in non-internet protocols. Originally acronymed as OSPFIGP. Open Systems Interconnection (OSI) Source: fyi4 A set of protocols designed to be an international standard method for connecting unlike computers and networks. Europe has done most of the work developing OSI and will probably use it as soon as possible. OSI Reference Model Source: nnsc A seven-layer structure designed to describe computer network architectures and the way that data passes through them. This model was developed by the ISO in 1978 to clearly define the interfaces in multivendor networks, and to provide users of those networks with conceptual guidelines in the construction of such net- works. OSI See "Open Systems Interconnection" OSPF See "Open Shortest-Path First Interior Gateway Proto- col" Packet Internet Groper (PING) Source: rfc1208 A program used to test reachability of destinations by sending them an ICMP echo request and waiting for a re- August 2, 1992 - 40 - ply. The term is used as a verb: "Ping host X to see if it is up!" Packet Switch Node (PSN) Source: nnsc A dedicated computer whose purpose is to accept, route forward packets in a packet switched network. packet switching Source: malamud A network that has packaged data into packets. A com- puter can handle many more virtual connections with packets than it can with dedicated connections (known as circuit switching). Packet switching forms the basis for X.25, as well as most network-layer proto- cols. packet Source: fyi4 The unit of data sent across a packet switching net- work. The term is used loosely. While some Internet literature uses it to refer specifically to data sent across a physical network, other literature views the Internet as a packet switching network and describes IP datagrams as packets. PD See "Public Domain" PDU See "Protocol Data Unit" PEM See "Privacy Enhanced Mail" PING See "Packet Internet Groper" Point Of Presence (POP) Source: A site where there exists a collection of telecommuni- cations equipment, usually digital leased lines and multi-protocol routers. Point-to-Point Protocol (PPP) Source: fyi4 August 2, 1992 - 41 - The Point-to-Point Protocol (PPP) provides a method for transmitting datagrams over serial point-to-point links. polling Source: zen Connecting to another system to check for things like mail or news. POP See "Post Office Protocol" and "Point Of Presence" port Source: rfc1208 The abstraction used by Internet transport protocols to distinguish among multiple simultaneous connections to a single destination host. See selector. Post Office Protocol (POP) Source: big-lan A TCP/IP-based protocol designed to allow client- stations (e.g. micros) to read mail from a server. There are three versions under the name "POP": POP, POP2, and POP3. Latter versions are NOT compatible with earlier versions. Postal, Telegraph and Telephone (PTT) Source: orig Outside the USA, PTT refers to a telephone service pro- vider that is usually a monopoly, in a particular coun- try. postmaster Source: zen The person responsible for taking care of mail prob- lems, answering queries about users, and other related work at a site. PPP See "Point-to-Point Protocol" Privacy Enhanced Mail (PEM) Source: orig August 2, 1992 - 42 - Internet email which provides confidentiality, authen- tication and message integrity using various encryption methods. See also: Electronic Mail. Protocol Data Unit (PDU) Source: malamud A layer communicates with its peer by sending packets. Each packet has a header that contains information that the peer will work with, such as addresses or ack- nowledgment requests. It also contains data, the pro- tocol data unit, that is passed up to the client of the layer. protocol stack Source: malamud A set of functions, one at each layer of the protocol stack, that work together to form a set of network ser- vices. Each layer of the protocol stack uses the ser- vices of the module beneath it and builds on that ser- vice. protocol Source: malamud A formal description of message formats and the rules two computers must follow to exchange those messages. Protocols can describe low-level details of machine- to-machine interfaces (e.g., the order in which bits and bytes are sent across a wire) or high-level ex- changes between allocation programs (e.g., the way in which two programs transfer a file across the Inter- net). proxy ARP Source: rfc1208 The technique in which one machine, usually a router, answers ARP requests intended for another machine. By "faking" its identity, the router accepts responsibili- ty 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 See "Packet Switch Node." PTT August 2, 1992 - 43 - See "Postal, Telegraph and Telephone" Public Domain (PD) Source: malamud Intellectual property available to people without pay- ing a fee. Most computer software developed at univer- sities is in the public domain. RARE See "Reseaux Associes pour la Recherche Europeenne" RARP See "Reverse Address Resolution Protocol" RBOC "Regional Bell Operating Company" RCP See "Remote copy program" Read the F*cking Manual (RTFM) Source: orig This acronym is often used when someone asks a simple or common question. reassembly Source: ??? Remote Procedure Call (RPC) Source: rfc1208 An easy and popular paradigm for implementing the client-server model of distributed computing. In gen- eral, a request is sent to a remote system to execute a designated procedure, using arguments supplied, and the result returned to the caller. There are many varia- tions and subtleties in various implementations, resulting in a variety of different (incompatible) RPC protocols. repeater Source: rfc1208 A device which propagates electrical signals from one cable to another without making routing decisions or August 2, 1992 - 44 - providing packet filtering. In OSI terminology, a re- peater is a Physical Layer intermediate system. See also bridge and router. On an Ethernet, repeaters are used to connect two or more segments of cable together. The repeater retimes and reamplifies the signal re- ceived on one segment before resending it on all other segments. Request For Comments (RFC) Source: hacker 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 stan- dards, but all Internet standards are written up as RFCs. The RFC series of documents are unusual in that the proposed protocols are forwarded by the Internet research and development community, acting on their own behalf, as opposed to the formally reviewed and stand- ardized protocols that are promoted by organizations such as CCITT and ANSI. See also: For Your Informa- tion, STD. Reseaux Associes pour la Recherche Europeenne (RARE) Source: rfc1208 European association of research networks. Reseaux IP Europeenne (RIPE) Source: orig A collaboration between networks in Europe which use the TCP/IP protocol suite. Reverse Address Resolution Protocol (RARP) Source: malamud A TCP/IP protocol which provides the reverse function of ARP. RARP maps a physical (hardware) address to an Internet address. Often used by diskless nodes when they first initialize to find their Internet address. RFC 822 Source: comer The TCP/IP standard format for electronic mail message headers. Mail experts often refer to "822 messages." The name comes from RFC 822 that contains the specifi- cation. 822 format was previously known as 733 format. August 2, 1992 - 45 - RFC See "Request For Comments" RIP See "Routing Information Protocol" RIPE See "Reseaux IP Europeenne" Round-Trip Time (RTT) Source: malamud A measure of the current delay on a network. route Source: orig The path that network traffic takes from its source to its destination. Also, a possible path from a given host to another host or destination. routed Source: orig Route Daemon. A program that runs under 4.2BSD/4.3BSD UNIX systems (and derived operating systems) to pro- pagate routes among machines on a local area network, using the RIP protocol. Pronounced "route-d". router Source: nnsc A device that attempts to choose the best network route for a packet from a group of routes available. This is a generic term and applies to such diverse devices as bridges, LAN routers and WAN gateways. Bridges are a primitive form of router that chooses whether or not it will pass packets from one physical network to another. Routers may do fragmentation and reassembly of packets, as necessary. A router is often a special-purpose dedicated computer, to ensure reliability. Routers operate at OSI Level 3, the Network Layer. routing domain Source: malamud A set of hosts and routers which operate according to the same routing procedures and which is wholly con- tained within a single administrative domain. August 2, 1992 - 46 - Routing Information Protocol (RIP) Source: nnsc An Interior Gateway Protocol provided in the Berkeley UNIX (see BSD) operating system, that permits a group of hosts located on a local network to share routing information. This function is typically provided by the program routed. RIP is used on many LANs and on some of the NSFnet regional networks. routing Source: orig The process of selecting the correct path (circuit) for a transmission over a network. RPC See "Remote Procedure Call" RTFM See "Read the F*cking Manual" RTT See "Round-Trip Time" Serial Line IP (SLIP) Source: rfc1208 A defacto protocol used to run IP over serial lines such as telephone circuits or RS-232 cables intercon- necting two systems. SLIP is now being replaced by PPP. See also Point-to-Point Protocol. SLIP is not an Internet standard but is defined in RFC 1055. server Source: sura A provider of resources. In a networking context, one often speaks of fileservers (which provide files to client machines), nameservers (which provide address to name lookups, and vice-versa) and other miscellaneous servers. SIG "Special Interest Group" signature Source: zen August 2, 1992 - 47 - The small, usually four-line message at the bottom of a piece of email or a Usenet article. In Unix, it's ad- ded by creating a file named `.signature' in the user's home directory. Large signatures are a no-no. Simple Mail Transfer Protocol (SMTP) Source: big-lan The protocol in the TCP/IP family used to transfer electronic mail between computers. SMTP mail follows RFC-822 closely. SMTP specifies how two mail systems interact and the format of control messages they ex- change to transfer mail. It is not oriented towards a client/server system so other protocols (see "POP") are often used in that context. However, servers will gen- erally use SMTP if they need to transfer a message to another server. Simple Network Management Protocol (SNMP) Source: Originally developed to manage IP based network equip- ment like routers and bridges, now extended to wiring hubs, workstations, toasters, jukeboxes, etc. SNMP for IPX and AppleTalk is under development. This protocol is defined in RFC 1157. SLIP See "Serial Line IP" SMDS See "Switched Multimegabit Data Service" SMI See "Structure of Management Information" SMTP See "Simple Mail Transfer Protocol" SNA See "Systems Network Architecture" snail mail Source: malamud The traditional postal service. SNMP See "Simple Network Management Protocol" STD August 2, 1992 - 48 - Source: orig A subset of RFCs that specify Internet standards. See also: For Your Information, Request For Comments. stream-oriented Source: malamud A type of transport service that allows its client to send data in a continuous stream. The transport ser- vice will guarantee that all data will be delivered to the other end in the same order as sent and without du- plicates. Also known as a reliable transport service. Structure of Management Information (SMI) Source: rfc1208 The rules used to define the objects that can be ac- cessed via a network management protocol. This proto- col is defined in RFC 1155. See also: Management In- formation Base. stub network Source: ??? subnet address Source: cs-gloss An extension of the Internet addressing system that al- lows a site to subdivide a single Internet address to cover multiple physical net works. This is done by di- viding up the host address part of an IP address into a local network number and host address number. subnet mask Source: rfc1208 See address mask. subnet number Source: fyi4 A part of the internet address which designates a sub- net. It is ignored for the purposes internet routing, but is used for intranet routing. August 2, 1992 - 49 - subnet Source: malamud A term used to denote any networking technology that makes all nodes connected to it appear to be one hop away. In other words, the user of the subnet can com- municate directly to all other nodes on the subnet. A subnet could be X.25, Ethernet, a token ring, ISDN, or a point-to-point link. A collection of subnets, to- gether with a routing or network layer, combine to form a network. switch See "packet switch" Switched Multimegabit Data Service (SMDS) Source: rfc1208 An emerging high-speed datagram-based public data net- work service developed by Bellcore and expected to be widely used by telephone companies as the basis for their data networks. Systems Network Architecture (SNA) Source: nnsc A proprietary networking architecture used by IBM and IBM-compatible mainframe computers. Because of its widespread use, SNA is a defacto standard. While it can use packet switched networks for transport, SNA is largely a circuit-switched rather than a packet- switching technology. T1 Source: orig An AT&T term for a digital carrier facility used to transmit a DS-1 formatted digital signal at 1.544 mega- bits per second. T3 Source: fyi4 A term for a digital carrier facility used to transmit a DS-3 formatted digital signal at 44.746 megabits per second. TAC See "Terminal Access Controller" August 2, 1992 - 50 - TCP See "Transmission Control Protocol" TCP/IP Protocol Suite Source: malamud Transmission Control Protocol over Internet Protocol. This is a common shorthand which refers to the suite of application and transport protocols which run over IP. These include FTP, Telnet, SMTP, and UDP (a transport layer protocol). TELENET Source: orig A public packet switched network using the CCITT X.25 protocols. It should not be confused with Telnet. Telnet Source: nnsc Telnet is a program that allows a computer user at one site to work on a computer at another site. It is the Internet standard protocol for remote terminal connec- tion service. TELNET requires Internet access, that is you must be on a TCP/IP network that gateways to the Internet. Unlike FTP and electronic mail, Telnet actu- ally exposes you to the commands and programs of the remote host. Terminal Access Controller Source: orig A program and piece of hardware that connects terminals to the Internet, usually using dialup modem connections and the TACACS protocol terminal emulator Source: malamud A program that allows a computer to emulate a terminal. The workstation thus appears as a terminal to the host. terminal server Source: csu A small, specialized, networked computer that connects many terminals to a LAN through one network connection. August 2, 1992 - 51 - Any user on the network can then TELNET to various net- work hosts. A terminal server can also connect many network users to its asynchronous ports. Three Letter Acronym (TLA) Source: UG A tribute to the use of acronyms in the computer field. See also: Extended Four Letter Acronym. Time to Live (TTL) Source: malamud Field in the Internet Protocol header which indicates how long this packet should be allowed to survive be- fore being discarded. TLA See "Three Letter Acronym" TN3270 Source: big-lan A variant of the TELNET program that allows one to at- tach to IBM mainframes and use the mainframe as if you had a 3270 or similar terminal. Token Ring Source: big-lan People often mean 802.5 when they say "Token Ring". In the more general sense of the word, a type of LAN that has stations wired in a ring, where each station con- stantly passes a special message (a "token") on to the next. Whoever has the token can send a message. topology Source: malamud A network topology shows the computers and the links between them. A network layer must stay abreast of the current network topology to be able to route packets to their final destination. transceiver Source: rfc1208 Transmitter-receiver. The physical device that con- August 2, 1992 - 52 - nects a host interface to a local area network, such as Ethernet. Ethernet transceivers contain electronics that apply signals to the cable and sense collisions. transit network Source: UG A transit network passes traffic between networks in addition to carrying traffic for its own hosts. It must have multiple connections to the Internet. See also: stub network. Transmission Control Protocol Source: fyi4 A transport layer protocol for the Internet. It is a connection oriented, stream protocol defined by RFC 793. Transmission Control Protocol/Internet Protocol Source: fyi4 This is a common shorthand which refers to the suite of application and transport protocols which run over IP. These include FTP, TELNET, SMTP, and UDP (a transport layer protocol). Trojan Horse Source: orig A computer program which carries within itself a means to allow the creator of the program access to the sys- tem using it. See also: virus, worm. TTL See "Time to Live" tunnelling Source: big-lan An important concept in the design of many kinds of networks: taking some protocol-family's ability to move packets from user to user, or to open virtual-circuits between users, and use this as if it were a data-link protocol to run another protocol family's upper layers (or even the same protocol family's upper layers). Ex- amples: running TCP/IP over Appletalk instead of some- thing like Ethernet; running Appletalk over DECnet in- stead of something like Localtalk or Ethernet. August 2, 1992 - 53 - twisted Pair Source: big-lan The type of wire used by the phone company to wire telephones -- at least over distances like between your house and the central office. It has two conductors, which are twisted. The twists are important: they give it electrical characteristics which allow some kinds of communications otherwise not possible. Ordinary tele- phone cables are not shielded (see "Shielded twisted Pair"). UDP See "User Datagram Protocol" Universal Time Coordinated (UTC) Source: malamud This is Greenwich Mean Time. UNIX-to-UNIX CoPy (UUCP) Source: nnsc This was initially a program run under the UNIX operat- ing system (see BSD) that permitted one UNIX system to send files to another UNIX system via dial-up phone lines. Today, the term is more commonly used to describe the large international network made up of these machines using the UUCP protocol to pass netnews and electronic mail. Usenet Source: malamud Network of Unix users. This is a somewhat informal network of loosely coupled nodes that agree to exchange information in the form of electronic mail and a bul- letin board. User Datagram Protocol (UDP) Source: fyi4 A transport layer protocol for the Internet. It is a datagram protocol which adds a level of reliability and multiplexing to IP datagrams. It is defined in RFC 768. UTC See "Universal Time Coordinated" August 2, 1992 - 54 - UUCP See "UNIX-to-UNIX CoPy" virtual circuit Source: UG A network service that allows two processes to communi- cate as if they were directly connected, regardless of the structure of the underlying subnet. virus Source: orig ??? See also: Trojan Horse, worm. W3 See "World Wide Web" WAIS See "Wide Area Information Servers" WAN See "Wide area network" WG "Working Group" White Pages Source: ??? whois Source: fyi4 An Internet program which allows users to query a data- base of people and other Internet entities, such as domains, networks, and hosts, kept at the DDN NIC. The information for people shows a person's company name, address, phone number and email address. Wide Area Information Servers (WAIS) Source: orig Allows users to search and access different types of information from a single interface. The WAIS protocol is an extension of the National Information Standards Organization Z39.50 information retrieval protocol. August 2, 1992 - 55 - Wide Area Network (WAN) Source: UG A network, usually constructed with serial lines, which covers large geographic areas. World Wide Web (WWW) Source: www A project based on the philosophy that much academic information should be freely available to anyone. The WWW project merges the techniques of information re- trieval and hypertext to make an easy but powerful glo- bal information system. worm Source: orig A computer program which replicates itself and is self-propagating. Worms, as opposed to viruses, are meant to spawn in network environments. Network worms were first defined by Shoch & Hupp of Xerox in ACM Com- munications (March 1982). The Internet worm of No- vember 1988 is perhaps the most famous; it successfully propagated itself on over 6,000 systems across the In- ternet. See also: Trojan Horse, virus. WRT "With Respect To" WWW See "World Wide Web" WYSIWYG "What You See is What You Get" X Source: orig X is the name for TCP/IP based network-oriented window systems. Network window systems allow a program to use a display on a different computer. The most widely- implemented window system is X11 - a component of MIT's Project Athena. X.25 Source: UG A data communications interface specification developed August 2, 1992 - 56 - to describe how data passes into and out of public data communications networks. The CCITT and ISO approved protocol suite defines protocol layers 1 through 3. X.400 Source: UG The CCITT and ISO standard for electronic mail. It is widely used in Europe and Canada. X.500 Source: UG The CCITT and ISO standard for electronic directory services. XDR See "eXternal Data Representation" Xerox Network System (XNS) Source: orig A network developed by Xerox corporation. Implementa- tions exist for both 4.3BSD derived systems, as well as the Xerox Star computers. XNS See "Xerox Network System" yellow pages Source: ??? August 2, 1992