Network Working Group G. Malkin
Request for Comments: 1392 Xylogics, Inc.
FYI: 18 T. LaQuey Parker
Internet Users' Glossary
Status of this Memo
This memo provides information for the Internet community. It does
not specify an Internet standard. Distribution of this memo is
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.
This document is the work of the User Glossary Working Group of the
User Services Area of the Internet Engineering Task Force (IETF).
Special thanks go to Jon Postel for his definitive definition of
Table of Contents
non-letter . . 2 I . . . . . . . 23 R . . . . . . . 40
A . . . . . . . 2 J . . . . . . . 29 S . . . . . . . 43
B . . . . . . . 6 K . . . . . . . 29 T . . . . . . . 45
C . . . . . . . 9 L . . . . . . . 29 U . . . . . . . 48
D . . . . . . . 12 M . . . . . . . 30 V . . . . . . . 49
E . . . . . . . 16 N . . . . . . . 33 W . . . . . . . 49
F . . . . . . . 18 O . . . . . . . 36 X . . . . . . . 50
G . . . . . . . 20 P . . . . . . . 37 Y . . . . . . . 51
H . . . . . . . 21 Q . . . . . . . 40 Z . . . . . . . 51
References . . . . . . . . . . . . . . . . . . . . . . . . . . 52
Security Considerations . . . . . . . . . . . . . . . . . . . . 53
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 53
User Glossary Working Group [Page 1]RFC 1392 Internet Glossary January 1993
A variant of Ethernet which allows stations to be attached via
twisted pair cable. See also: Ethernet, twisted pair.
The set of IEEE standards for the definition of LAN protocols.
See also: IEEE.
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.
A description of a data structure that is independent of machine-
oriented structures and encodings.
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
Acceptable Use Policy (AUP)
Many transit networks have policies which restrict the use to
which the network may be put. A well known example is NSFNET's
AUP which does not allow commercial use. Enforcement of AUPs
varies with the network. See also: National Science Foundation.
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.
User Glossary Working Group [Page 2]RFC 1392 Internet Glossary January 1993
A type of message sent to indicate that a block of data arrived at
its destination without error. See also: Negative
See: Access Control List
See: Administrative Domain
There are three types of addresses in common use within the
Internet. They are email address; IP, internet or Internet
address; and hardware or MAC address. See also: email address, IP
address, internet address, MAC address.
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 can be determined by the encoding inherent in an IP
Conversion of an internet address into the corresponding physical
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. It is defined in RFC 826. See also: proxy ARP.
Administrative Domain (AD)
A collection of hosts and routers, and the interconnecting
network(s), managed by a single administrative authority.
Advanced Research Projects Agency Network (ARPANET)
A pioneering longhaul network funded by ARPA (now DARPA). 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: Defense Advanced
Research Projects Agency.
User Glossary Working Group [Page 3]RFC 1392 Internet Glossary January 1993
In the client-server model, the part of the system that performs
information preparation and exchange on behalf of a client or
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
(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
American Standard Code for Information Interchange (ASCII)
A standard character-to-number encoding widely used in the
computer industry. See also: EBCDIC.
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
See: American National Standards Institute
See: Application Program Interface
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.
A program that performs a function directly for a user. FTP, mail
User Glossary Working Group [Page 4]RFC 1392 Internet Glossary January 1993
and Telnet clients are examples of network applications.
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.
Application Program Interface (API)
A set of calling conventions which define how a service is invoked
through a software package.
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
A machine that provides access to a collection of files across the
Internet. An "anonymous FTP archive site", for example, provides
access to this material via the FTP protocol. See also: anonymous
FTP, archie, Gopher, Prospero, Wide Area Information Servers.
See: Address Resolution Protocol
See: Defense Advanced Research Projects Agency
See: Advanced Research Projects Agency Network
See: Autonomous System
See: American Standard Code for Information Interchange
See: Abstract Syntax Notation One
The RFC [STD2] which documents the currently assigned values from
User Glossary Working Group [Page 5]RFC 1392 Internet Glossary January 1993
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,
Asynchronous Transfer Mode (ATM)
A method for the dynamic allocation of bandwidth using a fixed-
size packet (called a cell). ATM is also known as "fast packet".
See: Asynchronous Transfer Mode
See: Acceptable Use Policy
The verification of the identity of a person or process.
Autonomous System (AS)
A collection of routers under a single administrative authority
using a common Interior Gateway Protocol for routing packets.
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.
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.
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.
A transmission medium through which digital signals are sent
without complicated frequency shifting. In general, only one
User Glossary Working Group [Page 6]RFC 1392 Internet Glossary January 1993
communication channel is available at any given time. Ethernet is
an example of a baseband network. See also: broadband, Ethernet.
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.
See: Bulletin Board System
Be Seein' You
See: Basic Encoding Rules
Berkeley Internet Name Domain (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
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.
See: Border Gateway Protocol
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
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.
User Glossary Working Group [Page 7]RFC 1392 Internet Glossary January 1993
See: Berkeley Internet Name Domain
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.
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.
See: Birds Of a Feather
The Bootstrap Protocol, described in RFCs 951 and 1084, is used
for booting diskless nodes. See also: Reverse Address Resolution
Border Gateway Protocol (BGP)
The Border Gateway Protocol is an exterior gateway protocol
defined in RFCs 1267 and 1268. It's design is based on experience
gained with EGP, as defined in STD 18, RFC 904, and EGP usage in
the NSFNET Backbone, as described in RFCs 1092 and 1093. See
also: Exterior Gateway Protocol.
The return of a piece of mail because of an error in its delivery.
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.
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.
User Glossary Working Group [Page 8]RFC 1392 Internet Glossary January 1993
A special type of multicast packet which all nodes on the network
are always willing to receive. See also: multicast.
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.
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,
See: Berkeley Software Distribution
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.
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
See: Coordinating Committee for Intercontinental Research Networks
See: Comite Consultatif International de Telegraphique et
User Glossary Working Group [Page 9]RFC 1392 Internet Glossary January 1993
See: Computer Emergency Response Team
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.
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.
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.
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.
See: Coalition for Networked Information
Coalition for Networked Information (CNI)
A consortium formed by American Research Libraries, CAUSE, and
EDUCOM 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
This organization is part of the United National International
Telecommunications Union (ITU) 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.
User Glossary Working Group [Page 10]RFC 1392 Internet Glossary January 1993
Computer Emergency Response Team (CERT)
The CERT was formed by DARPA 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 "email@example.com" and by telephone at
+1-412-268-7090 (24-hour hotline). See also: Defense Advanced
Research Projects Agency, worm.
Congestion occurs when the offered load exceeds the capacity of a
data communication path.
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.
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
Historically, one of a set of gateways (routers) operated by the
User Glossary Working Group [Page 11]RFC 1392 Internet Glossary January 1993
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.
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.
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.
See: cyclic redundancy check
See: Corporation for Research and Educational Networking
See: Campus Wide Information system
A term coined by William Gibson in his fantasy novel Neuromancer
to describe the "world" of computers, and the society that gathers
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: Defense 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.
User Glossary Working Group [Page 12]RFC 1392 Internet Glossary January 1993
Data Encryption Standard (DES)
A popular, standard encryption scheme. See also: encryption.
A self-contained, independent entity of data carrying sufficient
information to be routed from the source to the destination
computer without reliance on earlier exchanges between this source
and destination computer and the transporting network. See also:
[Source: J. Postel]
See: Defense Information Systems Agency
Data Circuit-terminating Equipment
See: Distributed Computing Environment
See: Defense Data Network
See: Defense Data Network Network Information Center
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.
A routing table entry which is used to direct packets addressed to
networks not explicitly listed in the routing table.
Defense Advanced Research Projects Agency (DARPA)
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 responsible for funding much of the
development of the Internet we know today, including the Berkeley
version of Unix and TCP/IP.
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
User Glossary Working Group [Page 13]RFC 1392 Internet Glossary January 1993
is used to connect military installations and is managed by the
Defense Information Systems Agency. See also: Defense Information
Defense Data Network Network Information Center (DDN NIC)
Often called "The NIC", the DDN NIC's primary responsibility is
the assignment of Internet network addresses and Autonomous System
numbers, the administration of the root domain, and providing
information and support services to the DDN. It is also a primary
repository for RFCs. See also: Autonomous System, network
address, Internet Registry, Network Information Center, Request
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.
See: Data Encryption Key
See: Data Encryption Standard
A temporary, as opposed to dedicated, connection between machines
established over a standard phone line.
Directory Access Protocol
X.500 protocol used for communication between a Directory User
Agent and a Directory System Agent.
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.
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.
User Glossary Working Group [Page 14]RFC 1392 Internet Glossary January 1993
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.
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.
See: Domain Name System
"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. For example, .US (United
States), .UK (United Kingdom), .AU (Australia). It is defined in
STD 13, RFCs 1034 and 1035. See also: Fully Qualified Domain
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.
User Glossary Working Group [Page 15]RFC 1392 Internet Glossary January 1993
A framing specification for T-1 synchronous lines. See also: T1
A framing specification for T-3 synchronous lines. See also: T3
See: Directory System Agent
Data Terminal Equipment
See: Directory User Agent
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]
See: European Academic and Research Network
See: Extended Binary Coded Decimal Interchange Code
A pan-European backbone service.
See: Electronic Frontier Foundation
See: Extended Four Letter Acronym
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
Electronic Mail (email)
A system whereby a computer user can exchange messages with other
computer users (or groups of users) via a communications network.
User Glossary Working Group [Page 16]RFC 1392 Internet Glossary January 1993
Electronic mail is one of the most popular uses of the Internet.
See: Electronic mail
The domain-based or UUCP address that is used to send electronic
mail to a specified destination. For example an editor's address
is "firstname.lastname@example.org". See also: bang path, mail path, UNIX-
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.
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.
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
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.
European Academic and Research Network (EARN)
A network connecting European academic and research institutions
with electronic mail and file transfer services using the Bitnet
protocol. See also: Bitnet
User Glossary Working Group [Page 17]RFC 1392 Internet Glossary January 1993
Extended Binary Coded Decimal Interchange Code (EBCDIC)
A standard character-to-number encoding used primarily by IBM
computer systems. See also: ASCII.
Extended Four Letter Acronym (EFLA)
A recognition of the fact that there are far too many TLAs. See
also: Three Letter Acronym.
[Source: K. Morgan]
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 STD 18, RFC 904.
See also: Autonomous System, Border Gateway Protocol, Interior
eXternal Data Representation (XDR)
A standard for machine independent data structures developed by
Sun Microsystems and defined in RFC 1014. It is similar to ASN.1.
See also: Abstract Syntax Notation One.
A non-profit corporation, established in 1987, whose mission is to
advance the use of computer networks to improve research and
Frequently Asked Question
See: Fiber Distributed Data Interface
Federal Information Exchange (FIX)
One of the connection points between the American governmental
internets and the Internet.
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,
DARPA, NSF, NASA, and HHS. See also: Defense Advanced Research
Projects Agency, National Science Foundation.
User Glossary Working Group [Page 18]RFC 1392 Internet Glossary January 1993
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.
The copying of a file from one computer to another over a computer
network. See also: File Transfer Protocol, Kermit.
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. It is defined in STD 9, RFC 959. See also: anonymous
A program that displays information about a particular user, or
all users, logged on the local system or on a remote system. It
typically shows full name, last login time, idle time, terminal
line, and terminal location (where applicable). It may also
display plan and project files left by the user.
See: Federal Information Exchange
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:
See: Federal Networking Council
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
See: Fully Qualified Domain Name
User Glossary Working Group [Page 19]RFC 1392 Internet Glossary January 1993
A piece of a packet. When a router is forwarding an IP packet to
a network that has a maximum packet size 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.
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.
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.
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.
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
See: For Your Information
A dozen dozen (144).
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".
User Glossary Working Group [Page 20]RFC 1392 Internet Glossary January 1993
Pronounced "gate-dee". See also: Exterior Gateway Protocol, Open
Shortest Path First..., Routing Information Protocol, routed.
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.
A distributed information service that makes available
hierarchical collections of information across the Internet.
Gopher uses a simple protocol 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.
See: Government OSI Profile
Government OSI Profile
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.
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.
The portion of a packet, preceding the actual data, containing
source and destination addresses, and error checking and other
fields. A header is also the part of an electronic mail message
that precedes the body of a message and contains, among other
things, the message originator, date and time. See also:
Electronic Mail, packet.
A network running multiple network layer protocols. See also:
DECnet, IP, IPX, XNS.
User Glossary Working Group [Page 21]RFC 1392 Internet Glossary January 1993
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
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
See: High Performance Parallel Interface
A term used in routing. A path to a destination on a network is a
series of hops, through routers, away from the origin.
A computer that allows users to communicate with other host
computers on a network. Individual users communicate by using
application programs, such as electronic mail, Telnet and FTP.
See: internet address
The name given to a machine. See also: Fully Qualified Domain
User Glossary Working Group [Page 22]RFC 1392 Internet Glossary January 1993
See: host address
See: High Performance Computing and Communications
A device connected to several other devices. In ARCnet, a hub is
used to connect several computers together. In a message handling
service, a hub is used for the transfer of messages across the
See: Internet Architecture Board
See: Internet Assigned Numbers Authority
See: Internet Control Message Protocol
Institute of Electrical and Electronics Engineers
See: Internet Experiment Note
See: Internet Engineering Steering Group
See: Internet Engineering Task Force
See: Interagency Interim National Research and Education Network
See: Interior Gateway Protocol
User Glossary Working Group [Page 23]RFC 1392 Internet Glossary January 1993
In My Humble Opinion
See: Internet Monthly Report
Integrated Services Digital Network (ISDN)
An emerging technology which is beginning to be offered by the
telephone carriers of the world. ISDN combines voice and digital
network services in a single medium, making it possible to offer
customers digital data services as well as voice connections
through a single "wire". The standards that define ISDN are
specified by CCITT. See also: CCITT.
Interagency Interim National Research and Education Network (IINREN)
An evolving operating network system. Near term (1992-1996)
research and development activities will provide for the smooth
evolution of this networking infrastructure into the future
Interior Gateway Protocol (IGP)
A protocol which distributes routing information to the routers
within an autonomous system. The term "gateway" is historical, as
"router" is currently the preferred term. See also: Autonomous
System, Exterior Gateway Protocol, Open Shortest Path First...,
Routing Information Protocol.
Intermediate System (IS)
An OSI system which performs network layer forwarding. It is
analogous to an IP router. See also: Open Systems
Intermediate System-Intermediate System (IS-IS)
The OSI IGP. See also: Open Systems Interconnection, Interior
International Organization for Standardization (ISO)
A voluntary, nontreaty organization founded in 1946 which is
responsible for creating international standards in many areas,
including computers and communications. Its members are the
national standards organizations of the 89 member countries,
including ANSI for the U.S. See also: American National Standards
Institute, Open Systems Interconnection.
User Glossary Working Group [Page 24]RFC 1392 Internet Glossary January 1993
While an internet is a network, the term "internet" is usually
used to refer to a collection of networks interconnected with
routers. See also: network.
(note the capital "I") The Internet is the largest internet in the
world. Is a three level hierarchy composed of backbone networks
(e.g., NSFNET, MILNET), mid-level networks, and stub networks.
The Internet is a multiprotocol internet. See also: backbone,
mid-level network, stub network, transit network, Internet
Protocol, Corporation for Research and Educational Networks,
National Science Foundation.
A IP address that uniquely identifies a node on an internet. An
Internet address (capital "I"), uniquely identifies a node on the
Internet. See also: internet, Internet, IP address.
Internet Architecture Board (IAB)
The technical body that oversees the development of the Internet
suite of protocols. It has two task forces: the IETF and the
IRTF. "IAB" previously stood for Internet Activities Board. See
also: Internet Engineering Task Force, Internet Research Task
Internet Assigned Numbers Authority (IANA)
The central registry for various Internet protocol parameters,
such as port, protocol and enterprise numbers, and options, codes
and types. The currently assigned values are listed in the
"Assigned Numbers" document [STD2]. To request a number
assignment, contact the IANA at "email@example.com". See also:
assigned numbers, STD.
Internet Control Message Protocol (ICMP)
ICMP is an extension to the Internet Protocol. It allows for the
generation of error messages, test packets and informational
messages related to IP. It is defined in STD 5, RFC 792.
Internet-Drafts are working documents of the IETF, its Areas, and
its Working Groups. As the name implies, Internet-Drafts are
draft documents. They are valid for a maximum of six months and
may be updated, replaced, or obsoleted by other documents at any
time. Very often, I-Ds are precursors to RFCs. See also:
Internet Engineering Task Force, Request For Comments.
User Glossary Working Group [Page 25]RFC 1392 Internet Glossary January 1993
Internet Engineering Steering Group (IESG)
The IESG is composed of the IETF Area Directors and the IETF
Chair. It provides the first technical review of Internet
standards and is responsible for day-to-day "management" of the
IETF. See also: Internet Engineering Task Force.
Internet Engineering Task Force (IETF)
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 proposals for protocol standards
which are submitted to the IAB for final approval. The IETF meets
three times a year and extensive minutes are included in the IETF
Proceedings. See also: Internet, Internet Architecture Board.
Internet Experiment Note (IEN)
A series of reports pertinent to the Internet. IENs were
published in parallel to RFCs and are no longer active. See also:
Internet-Draft, Request For Comments.
Internet Monthly Report (IMR)
Published monthly, the purpose of the Internet Monthly Reports is
to communicate to the Internet Research Group the accomplishments,
milestones reached, or problems discovered by the participating
See: internet address
Internet Protocol (IP)
The Internet Protocol, defined in STD 5, RFC 791, is the network
layer for the TCP/IP Protocol Suite. It is a connectionless,
best-effort packet switching protocol. See also: packet
switching, Request For Comments, TCP/IP Protocol Suite.
Internet Registry (IR)
The IANA has the discretionary authority to delegate portions of
its responsibility and, with respect to network address and
Autonomous System identifiers, has lodged this responsibility with
an IR. The IR function is performed by the DDN NIC. See also:
Autonomous System, network address, Defense Data Network...,
Internet Assigned Numbers Authority.
Internet Relay Chat (IRC)
A world-wide "party line" protocol that allows one to converse
with others in real time. IRC is structured as a network of
User Glossary Working Group [Page 26]RFC 1392 Internet Glossary January 1993
servers, each of which accepts connections from client programs,
one per user. See also: talk.
Internet Research Steering Group (IRSG)
The "governing body" of the IRTF. See also: Internet Research
Internet Research Task Force (IRTF)
The IRTF is chartered by the IAB to consider long-term Internet
issues from a theoretical point of view. It has Research Groups,
similar to IETF Working Groups, which are each tasked to discuss
different research topics. Multi-cast audio/video conferencing
and privacy enhanced mail are samples of IRTF output. See also:
Internet Architecture Board, Internet Engineering Task Force,
Privacy Enhanced Mail.
Internet Society (ISOC)
The Internet Society is a non-profit, professional membership
organization which facilitates and supports the technical
evolution of the Internet, stimulates interest in and educates the
scientific and academic communities, industry and the public about
the technology, uses and applications of the Internet, and
promotes the development of new applications for the system. The
Society provides a forum for discussion and collaboration in the
operation and use of the global Internet infrastructure. The
Internet Society publishes a quarterly newsletter, the Internet
Society News, and holds an annual conference, INET. The
development of Internet technical standards takes place under the
auspices of the Internet Society with substantial support from the
Corporation for National Research Initiatives under a cooperative
agreement with the US Federal Government.
[Source: V. Cerf]
Internetwork Packet eXchange (IPX)
Novell's protocol used by Netware. A router with IPX routing can
interconnect LANs so that Novell Netware clients and servers can
communicate. See also: Local Area Network.
The ability of software and hardware on multiple machines from
multiple vendors to communicate meaningfully.
See: Internet Protocol
User Glossary Working Group [Page 27]RFC 1392 Internet Glossary January 1993
The 32-bit address defined by the Internet Protocol in STD 5, RFC
791. It is usually represented in dotted decimal notation. See
also: dot address, internet address, Internet Protocol, network
address, subnet address, host address.
See: Internetwork Packet eXchange
See: Internet Registry
See: Internet Relay Chat
See: Internet Research Steering Group
See: Internet Research Task Force
See: Intermediate System
See: Intermediate System-Intermediate System
See: Integrated Services Digital Network
See: International Organization for Standardization
ISO Development Environment (ISODE)
Software that allows OSI services to use a TCP/IP network.
Pronounced eye-so-dee-eee. See also: Open Systems
Interconnection, TCP/IP Protocol Suite.
See: Internet Society
See: ISO Development Environment
User Glossary Working Group [Page 28]RFC 1392 Internet Glossary January 1993
Joyce K. Reynolds
A popular implementation of TCP/IP and associated protocols for
amateur packet radio systems. See also: TCP/IP Protocol Suite.
Kerberos is the security system of MIT's Project Athena. It is
based on symmetric key cryptography. See also: encryption.
A popular file transfer protocol developed by Columbia University.
Because Kermit runs in most operating environments, it provides an
easy method of file transfer. Kermit is NOT the same as FTP. See
also: File Transfer Protocol
An experimental directory service. See also: white pages, WHOIS,
See: Local Area Network
Communication 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 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 communicate with each other.
TCP/IP has five layers of protocols; OSI has seven. The
advantages of different layers of protocols is that the methods of
passing information from one layer to another are specified
clearly 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. See also: Open Systems Interconnection,
TCP/IP Protocol Suite.
An automated mailing list distribution system originally designed
for the Bitnet/EARN network. See also: Bitnet, European Academic
Research Network, mailing list.
User Glossary Working Group [Page 29]RFC 1392 Internet Glossary January 1993
A format for storage or transmission of binary data in which the
least significant byte (bit) comes first. See also: big-endian.
See: Logical Link Control
Local Area Network (LAN)
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 up to 100Mb/s. See also:
Ethernet, Fiber Distributed Data Interface, token ring, Wide Area
Logical Link Control (LLC)
The upper portion of the datalink layer, as defined in IEEE 802.2.
The LLC sublayer presents a uniform interface to the user of the
datalink service, usually the network layer. Beneath the LLC
sublayer is the MAC sublayer. See also: 802.x, layer, Media
No active participation on the part of a subscriber to an mailing
list or USENET newsgroup. A person who is lurking is just
listening to the discussion. Lurking is encouraged for beginners
who need to get up to speed on the history of the group. See
also: Electronic Mail, mailing list, Usenet.
See: Media Access Control
The hardware address of a device connected to a shared media. See
also: Media Access Control, Ethernet, token ring.
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 gateway that enforces an administrative policy with
regard to what mail it forwards. See also: Electronic Mail, mail
User Glossary Working Group [Page 30]RFC 1392 Internet Glossary January 1993
Mail Exchange Record (MX Record)
A DNS resource record type indicating which host can handle mail
for a particular domain. See also: Domain Name System, Electronic
Part of an electronic mail delivery system which allows a message
to be delivered to a list of addresses. Mail exploders are used
to implement mailing lists. Users send messages to a single
address and the mail exploder takes care of delivery to the
individual mailboxes in the list. See also: Electronic Mail,
email address, mailing list.
A machine that connects two or more electronic mail systems
(including dissimilar mail systems) and transfers messages between
them. Sometimes the mapping and translation can be quite complex,
and it generally 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. See
also: Electronic Mail.
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, email address, UNIX-to-UNIX
A software program that distributes files or information in
response to requests sent via email. Internet examples include
Almanac and netlib. Mail servers have also been used in Bitnet to
provide FTP-like services. See also: Bitnet, Electronic Mail,
A list of email addresses, used by a mail exploder, to forward
messages to groups of people. Generally, a mailing list is used
to discuss certain set of topics, and different mailing lists
discuss different topics. A mailing list may be moderated. This
means that messages sent to the list are actually sent to a
moderator who determines whether or not to send the messages on to
everyone else. Requests to subscribe to, or leave, a mailing list
User Glossary Working Group [Page 31]RFC 1392 Internet Glossary January 1993
should ALWAYS be sent to the list's "-request" address (e.g.,
firstname.lastname@example.org for the IETF mailing list). See
also: Electronic Mail, mail exploder.
See: Metropolitan Area Network
Management Information Base (MIB)
The set of parameters an SNMP management station can query or set
in the SNMP agent of a network device (e.g., router). Standard,
minimal MIBs have been defined, and vendors often have Private
enterprise MIBs. In theory, any SNMP manager can talk to any SNMP
agent with a properly defined MIB. See also: client-server model,
Simple Network Management Protocol.
A humorous term applied to packets that turn up unexpectedly on
the wrong network because of bogus routing entries. Also used as
a name for a packet which has an altogether bogus (non-registered
or ill-formed) internet address.
Maximum Transmission Unit (MTU)
The largest frame length which may be sent on a physical medium.
See also: fragmentation, frame.
Media Access Control (MAC)
The lower portion of the datalink layer. The MAC differs for
various physical media. See also: MAC Address, Ethernet, Logical
Link Control, token ring.
See: packet switching
Metropolitan Area Network (MAN)
A data network intended to serve an area approximating that of a
large city. Such networks are being implemented by innovative
techniques, such as running fiber cables through subway tunnels.
A popular example of a MAN is SMDS. See also: Local Area Network,
Switched Multimegabit Data Service, Wide Area Network.
See: Management Information Base
Mid-level networks (a.k.a. regionals) make up the second level of
User Glossary Working Group [Page 32]RFC 1392 Internet Glossary January 1993
the Internet hierarchy. They are the transit networks which
connect the stub networks to the backbone networks. See also:
backbone, Internet, stub network, transit network.
See: Multipurpose Internet Mail Extensions
A person, or small group of people, who manage moderated mailing
lists and newsgroups. Moderators are responsible for determining
which email submissions are passed on to list. See also:
Electronic Mail, mailing list, Usenet.
See: Maximum Transmission Unit
See: Multi-User Dungeon
A packet with a special destination address which multiple nodes
on the network may be willing to receive. See also: broadcast.
A host which has more than one connection to a network. The host
may send and receive data over any of the links but will not route
traffic for other nodes. See also: host, router.
Multipurpose Internet Mail Extensions (MIME)
An extension to Internet email which provides the ability to
transfer non-textual data, such as graphics, audio and fax. It is
defined in RFC 1341. See also: Electronic Mail
Multi-User Dungeon (MUD)
Adventure, role playing games, or simulations played on the
Internet. Devotees call them "text-based virtual reality
adventures". The games can feature fantasy combat, booby traps
and magic. Players interact in real time and can change the
"world" in the game as they play it. Most MUDs are based on the
Telnet protocol. See also: Telnet.
See: Mail Exchange Record
See: Negative Acknowledgment
User Glossary Working Group [Page 33]RFC 1392 Internet Glossary January 1993
The process of mapping a name into its corresponding address. See
also: Domain Name System.
A commonly distributed set of names in which all names are unique.
National Institute of Standards and Technology (NIST)
United States governmental body that provides assistance in
developing standards. Formerly the National Bureau of Standards.
National Research and Education Network (NREN)
The NREN is the realization of an interconnected gigabit computer
network devoted to Hign Performance Computing and Communications.
See also: HPPC, IINREN.
National Science Foundation (NSF)
A U.S. government agency whose purpose is to promote the
advancement 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 communications. 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 45Mb/s facility which spans the continental United
States. Attached to that are mid-level 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)
Response to receipt of a corrupted packet of information. See
A pun on "etiquette" referring to proper behavior on a network.
A computer network is a data communications system which
interconnects computer systems at various different sites. A
network may be composed of any combination of LANs, MANs or WANs.
User Glossary Working Group [Page 34]RFC 1392 Internet Glossary January 1993
See also: Local Area Network, Metropolitan Area Network, Wide Area
The network portion of an IP address. For a class A network, the
network address is the first byte of the IP address. For a class
B network, the network address is the first two bytes of the IP
address. For a class C network, the network address is the first
three bytes of the IP address. In each case, the remainder is the
host address. In the Internet, assigned network addresses are
globally unique. See also: Internet, IP address, subnet address,
host address, Internet Registry.
Network File System (NFS)
A protocol developed by Sun Microsystems, and defined in RFC 1094,
which allows 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 Internet standard.
Network Information Center (NIC)
A NIC provides information, assistance and services to network
users. See also: Network Operations Center.
Network Information Services (NIS)
A set of services, generally provided by a NIC, to assist users in
using the network. See also: Network Information Center.
Network News Transfer Protocol (NNTP)
A protocol, defined in RFC 977, for the distribution, inquiry,
retrieval, and posting of news articles. See also: Usenet.
See: network address
Network Operations Center (NOC)
A location from which the operation of a network or internet is
monitored. Additionally, this center usually serves as a
clearinghouse for connectivity problems and efforts to resolve
those problems. See also: Network Information Center.
Network Time Protocol (NTP)
A protocol that assures accurate local timekeeping with reference
to radio and atomic clocks located on the Internet. This protocol
is capable of synchronizing distributed clocks within milliseconds
over long time periods. It is defined in STD 12, RFC 1119. See
User Glossary Working Group [Page 35]RFC 1392 Internet Glossary January 1993
See: Network File System
See: Network Information Center
This is the domain name of the DDN NIC. See also: Defense Data
Network..., Domain Name System, Network Information Center.
See: Network Information Services
See: National Institute of Standards and Technology
See: Network News Transfer Protocol
See: Network Operations Center
Nodal Switching System (NSS)
Main routing nodes in the NSFnet backbone. See also: backbone,
National Science Foundation.
An addressable device attached to a computer network. See also:
See: National Research and Education Network
See: National Science Foundation
See: Nodal Switching System
See: Network Time Protocol
See: Online Computer Library Catalog
User Glossary Working Group [Page 36]RFC 1392 Internet Glossary January 1993
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.
Online Computer Library Catalog
OCLC is a nonprofit membership organization offering computer-
based services to libraries, educational organizations, and their
users. The OCLC library information network connects more than
10,000 libraries worldwide. Libraries use the OCLC System for
cataloging, interlibrary loan, collection development,
bibliographic verification, and reference searching.
Open Shortest-Path First Interior Gateway Protocol (OSPF)
A link state, as opposed to distance vector, routing protocol. It
is an Internet standard IGP defined in RFC 1247. See also:
Interior Gateway Protocol, Routing Information Protocol.
Open Systems Interconnection (OSI)
A suite of protocols, designed by ISO committees, to be the
international standard computer network architecture. See also:
International Organization for Standardization.
See: Open Systems Interconnection
OSI Reference Model
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
networks. See also: International Organization for
See: Open Shortest-Path First Interior Gateway Protocol
The unit of data sent across a network. "Packet" a generic term
used to describe unit of data at all levels of the protocol stack,
but it is most correctly used to describe application data units.
See also: datagram, frame.
Packet InterNet Groper (PING)
A program used to test reachability of destinations by sending
them an ICMP echo request and waiting for a reply. The term is
User Glossary Working Group [Page 37]RFC 1392 Internet Glossary January 1993
used as a verb: "Ping host X to see if it is up!" See also:
Internet Control Message Protocol.
Packet Switch Node (PSN)
A dedicated computer whose purpose is to accept, route and forward
packets in a packet switched network. See also: packet switching,
A communications paradigm in which packets (messages) are
individually routed between hosts, with no previously established
communication path. See also: circuit switching, connection-
See: Protocol Data Unit
See: Privacy Enhanced Mail
See: Packet INternet Groper
Point Of Presence (POP)
A site where there exists a collection of telecommunications
equipment, usually digital leased lines and multi-protocol
Point-to-Point Protocol (PPP)
The Point-to-Point Protocol, defined in RFC 1171, provides a
method for transmitting packets over serial point-to-point links.
See also: Serial Line IP.
See: Post Office Protocol and Point Of Presence
A port is a transport layer demultiplexing value. Each
application has a unique port number associated with it. See
also: Transmission Control Protocol, User Datagram Protocol.
User Glossary Working Group [Page 38]RFC 1392 Internet Glossary January 1993
Post Office Protocol (POP)
A protocol designed to allow single user hosts to read mail from a
server. There are three versions: POP, POP2, and POP3. Latter
versions are NOT compatible with earlier versions. See also:
Postal Telegraph and Telephone (PTT)
Outside the USA, PTT refers to a telephone service provider, which
is usually a monopoly, in a particular country.
The person responsible for taking care of electronic mail
problems, answering queries about users, and other related work at
a site. See also: Electronic Mail.
See: Point-to-Point Protocol
Privacy Enhanced Mail (PEM)
Internet email which provides confidentiality, authentication and
message integrity using various encryption methods. See also:
Electronic Mail, encryption.
A distributed filesystem which provides the user with the ability
to create multiple views of a single collection of files
distributed across the Internet. Prospero provides a file naming
system, and file access is provided by existing access methods
(e.g., anonymous FTP and NFS). The Prospero protocol is also used
for communication between clients and servers in the archie
system. See also: anonymous FTP, archie, archive site, Gopher,
Network File System, Wide Area Information Servers.
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 exchanges between allocation programs (e.g., the way in
which two programs transfer a file across the Internet).
A device/program which translates between different protocols
which serve similar functions (e.g., TCP and TP4).
User Glossary Working Group [Page 39]RFC 1392 Internet Glossary January 1993
Protocol Data Unit (PDU)
"PDU" is internationalstandardscomitteespeak for packet. See
A layered set of protocols which work together to provide a set of
network functions. See also: layer, protocol.
The technique in which one machine, usually a router, answers ARP
requests intended for another machine. By "faking" its identity,
the router accepts responsibility for routing packets to the
"real" destination. Proxy ARP allows a site to use a single IP
address with two physical networks. Subnetting would normally be
a better solution. See also: Address Resolution Protocol
See: Packet Switch Node.
See: Postal, Telegraph and Telephone
A backup of packets awaiting processing.
See: Reseaux Associes pour la Recherche Europeenne
See: Reverse Address Resolution Protocol
Regional Bell Operating Company
See: Remote copy program
Read the F*cking Manual (RTFM)
This acronym is often used when someone asks a simple or common
The IP process in which a previously fragmented packet is
reassembled before being passed to the transport layer. See also:
User Glossary Working Group [Page 40]RFC 1392 Internet Glossary January 1993
See: mid-level network
Operating on a remote computer, using a protocol over a computer
network, as though locally attached. See also: Telnet.
Remote Procedure Call (RPC)
An easy and popular paradigm for implementing the client-server
model of distributed computing. In general, 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
variations and subtleties in various implementations, resulting in
a variety of different (incompatible) RPC protocols.
A device which propagates electrical signals from one cable to
another. See also: bridge, gateway, router.
Request For Comments (RFC)
The document series, begun in 1969, which describes the Internet
suite of protocols and related experiments. Not all (in fact very
few) RFCs describe Internet standards, but all Internet standards
are written up as RFCs. The RFC series of documents is 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 standardized protocols that are
promoted by organizations such as CCITT and ANSI. See also: For
Your Information, STD.
Reseaux Associes pour la Recherche Europeenne (RARE)
European association of research networks.
Reseaux IP Europeenne (RIPE)
A collaboration between European networks which use the TCP/IP
Reverse Address Resolution Protocol (RARP)
A protocol, defined in RFC 903, which provides the reverse
function of ARP. RARP maps a hardware (MAC) address to an
internet address. It is used primarily by diskless nodes when
they first initialize to find their internet address. See also:
Address Resolution Protocol, BOOTP, internet address, MAC address.
User Glossary Working Group [Page 41]RFC 1392 Internet Glossary January 1993
See: Request For Comments
The Internet standard format for electronic mail message headers.
Mail experts often refer to "822 messages". The name comes from
"RFC 822", which contains the specification (STD 11, RFC 822).
822 format was previously known as 733 format. See also:
See: Routing Information Protocol
See: Reseaux IP Europeenne
Round-Trip Time (RTT)
A measure of the current delay on a network.
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.
Route Daemon. A program which runs under 4.2BSD/4.3BSD UNIX
systems (and derived operating systems) to propagate routes among
machines on a local area network, using the RIP protocol.
Pronounced "route-dee". See also: Routing Information Protocol,
A device which forwards traffic between networks. The forwarding
decision is based on network layer information and routing tables,
often constructed by routing protocols. See also: bridge,
gateway, Exterior Gateway Protocol, Interior Gateway Protocol.
The process of selecting the correct interface and next hop for a
packet being forwarded. See also: hop, router, Exterior Gateway
Protocol, Interior Gateway Protocol.
A set of routers exchanging routing information within an
administrative domain. See also: Administrative Domain, router.
User Glossary Working Group [Page 42]RFC 1392 Internet Glossary January 1993
Routing Information Protocol (RIP)
A distance vector, as opposed to link state, routing protocol. It
is an Internet standard IGP defined in STD 34, RFC 1058 (updated
by RFC 1388). See also: Interior Gateway Protocol, Open Shortest
See: Remote Procedure Call
See: Read the F*cking Manual
See: Round-Trip Time
Serial Line IP (SLIP)
A protocol used to run IP over serial lines, such as telephone
circuits or RS-232 cables, interconnecting two systems. SLIP is
defined in RFC 1055. See also: Point-to-Point Protocol.
A provider of resources (e.g., file servers and name servers).
See also: client, Domain Name System, Network File System.
Special Interest Group
The three or four line message at the bottom of a piece of email
or a Usenet article which identifies the sender. Large signatures
(over five lines) are generally frowned upon. See also:
Electronic Mail, Usenet.
Simple Mail Transfer Protocol (SMTP)
A protocol, defined in STD 10, RFC 821, used to transfer
electronic mail between computers. It is a server to server
protocol, so other protocols are used to access the messages. See
also: Electronic Mail, Post Office Protocol, RFC 822.
Simple Network Management Protocol (SNMP)
The Internet standard protocol, defined in STD 15, RFC 1157,
developed to manage nodes on an IP network. It is currently
possible to manage wiring hubs, toasters, jukeboxes, etc. See
also: Management Information Base.
See: Serial Line IP
User Glossary Working Group [Page 43]RFC 1392 Internet Glossary January 1993
See: Switched Multimegabit Data Service
See: Structure of Management Information
See: Simple Mail Transfer Protocol
See: Systems Network Architecture
A pejorative term referring to the U.S. postal service.
See: Simple Network Management Protocol
A subseries of RFCs that specify Internet standards. The official
list of Internet standards is in STD 1. See also: For Your
Information, Request For Comments.
A type of transport service that allows its client to send data in
a continuous stream. The transport service will guarantee that
all data will be delivered to the other end in the same order as
sent and without duplicates. See also: Transmission Control
Structure of Management Information (SMI)
The rules used to define the objects that can be accessed via a
network management protocol. This protocol is defined in STD 16,
RFC 1155. See also: Management Information Base.
A stub network only carries packets to and from local hosts. Even
if it has paths to more than one other network, it does not carry
traffic for other networks. See also: backbone, transit network.
A portion of a network, which may be a physically independent
network segment, which shares a network address with other
portions of the network and is distinguished by a subnet number.
A subnet is to a network what a network is to an internet. See
also: internet, network.
User Glossary Working Group [Page 44]RFC 1392 Internet Glossary January 1993
The subnet portion of an IP address. In a subnetted network, the
host portion of an IP address is split into a subnet portion and a
host portion using an address (subnet) mask. See also: address
mask, IP address, network address, host address.
See: address mask
See: subnet address
Switched Multimegabit Data Service (SMDS)
An emerging high-speed datagram-based public data network service
developed by Bellcore and expected to be widely used by telephone
companies as the basis for their data networks. See also:
Metropolitan Area Network.
Systems Network Architecture (SNA)
A proprietary networking architecture used by IBM and IBM-
compatible mainframe computers.
An AT&T term for a digital carrier facility used to transmit a
DS-1 formatted digital signal at 1.544 megabits per second.
A term for a digital carrier facility used to transmit a DS-3
formatted digital signal at 44.746 megabits per second.
See: Terminal Access Controller (TAC)
A protocol which allows two people on remote computers to
communicate in a real-time fashion. See also: Internet Relay
See: Transmission Control Protocol
TCP/IP Protocol Suite
Transmission Control Protocol over Internet Protocol. This is a
User Glossary Working Group [Page 45]RFC 1392 Internet Glossary January 1993
common shorthand which refers to the suite of transport and
application protocols which runs over IP. See also: IP, ICMP,
TCP, UDP, FTP, Telnet, SMTP, SNMP.
A public packet switched network using the CCITT X.25 protocols.
It should not be confused with Telnet.
Telnet is the Internet standard protocol for remote terminal
connection service. It is defined in STD 8, RFC 854 and extended
with options by many other RFCs.
Terminal Access Controller (TAC)
A device which connects terminals to the Internet, usually using
dialup modem connections and the TACACS protocol.
A program that allows a computer to emulate a terminal. The
workstation thus appears as a terminal to the remote host.
A device which connects many terminals to a LAN through one
network connection. A terminal server can also connect many
network users to its asynchronous ports for dial-out capabilities
and printer access. See also: Local Area Network.
Three Letter Acronym (TLA)
A tribute to the use of acronyms in the computer field. See also:
Extended Four Letter Acronym.
Time to Live (TTL)
A field in the IP header which indicates how long this packet
should be allowed to survive before being discarded. It is
primarily used as a hop count. See also: Internet Protocol.
See: Three Letter Acronym
A variant of the Telnet program that allows one to attach to IBM
mainframes and use the mainframe as if you had a 3270 or similar
User Glossary Working Group [Page 46]RFC 1392 Internet Glossary January 1993
A token ring is a type of LAN with nodes wired into a ring. Each
node constantly passes a control message (token) on to the next;
whichever node has the token can send a message. Often, "Token
Ring" is used to refer to the IEEE 802.5 token ring standard,
which is the most common type of token ring. See also: 802.x,
Local Area Network.
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.
Transmitter-receiver. The physical device that connects a host
interface to a local area network, such as Ethernet. Ethernet
transceivers contain electronics that apply signals to the cable
and sense collisions.
A transit network passes traffic between networks in addition to
carrying traffic for its own hosts. It must have paths to at
least two other networks. See also: backbone, stub network.
Transmission Control Protocol (TCP)
An Internet Standard transport layer protocol defined in STD 7,
RFC 793. It is connection-oriented and stream-oriented, as
opposed to UDP. See also: connection-oriented, stream-oriented,
User Datagram Protocol.
A computer program which carries within itself a means to allow
the creator of the program access to the system using it. See
also: virus, worm. See RFC 1135.
Ta-Ta For Now
See: Time to Live
Tunnelling refers to encapsulation of protocol A within protocol
B, such that A treats B as though it were a datalink layer.
Tunnelling is used to get data between administrative domains
which use a protocol that is not supported by the internet
User Glossary Working Group [Page 47]RFC 1392 Internet Glossary January 1993
connecting those domains. See also: Administrative Domain.
A type of cable in which pairs of conductors are twisted together
to produce certain electrical properties.
See: User Datagram Protocol
Universal Time Coordinated (UTC)
This is Greenwich Mean Time.
UNIX-to-UNIX CoPy (UUCP)
This was initially a program run under the UNIX operating system
that allowed 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 which uses the UUCP
protocol to pass news and electronic mail. See also: Electronic
A story, which may have started with a grain of truth, that has
been embroidered and retold until it has passed into the realm of
myth. It is an interesting phenonmenon that these stories get
spread so far, so fast and so often. Urban legends never die,
they just end up on the Internet! Some legends that periodically
make their rounds include "The Infamous Modem Tax," "Craig
Shergold/Brain Tumor/Get Well Cards," and "The $250 Cookie
A collection of thousands of topically named newsgroups, the
computers which run the protocols, and the people who read and
submit Usenet news. Not all Internet hosts subscribe to Usenet
and not all Usenet hosts are on the Internet. See also: Network
News Transfer Protocol, UNIX-to-UNIX CoPy.
User Datagram Protocol (UDP)
An Internet Standard transport layer protocol defined in STD 6,
RFC 768. It is a connectionless protocol which adds a level of
reliability and multiplexing to IP. See also: connectionless,
Transmission Control Protocol.
See: Universal Time Coordinated
User Glossary Working Group [Page 48]RFC 1392 Internet Glossary January 1993
See: UNIX-to-UNIX CoPy
A network service which provides connection-oriented service
regardless of the underlying network structure. See also:
A program which replicates itself on computer systems by
incorporating itself into other programs which are shared among
computer systems. See also: Trojan Horse, worm.
See: World Wide Web
See: Wide Area Information Servers
See: Wide area network
The Internet supports several databases that contain basic
information about users, such as email addresses, telephone
numbers, and postal addresses. These databases can be searched to
get information about particular individuals. Because they serve
a function akin to the telephone book, these databases are often
referred to as "white pages. See also: Knowbot, WHOIS, X.500.
An Internet program which allows users to query a database 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.
See also: Defense Data Network Network ..., white pages, Knowbot,
Wide Area Information Servers (WAIS)
A distributed information service which offers simple natural
language input, indexed searching for fast retrieval, and a
"relevance feedback" mechanism which allows the results of initial
searches to influence future searches. Public domain
implementations are available. See also: archie, Gopher,
User Glossary Working Group [Page 49]RFC 1392 Internet Glossary January 1993
Wide Area Network (WAN)
A network, usually constructed with serial lines, which covers a
large geographic area. See also: Local Area Network, Metropolitan
World Wide Web (WWW or W3)
A hypertext-based, distributed information system created by
researchers at CERN in Switzerland. Users may create, edit or
browse hypertext documents. The clients and servers are freely
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 Communications (March 1982). The Internet
worm of November 1988 is perhaps the most famous; it successfully
propagated itself on over 6,000 systems across the Internet. See
also: Trojan Horse, virus.
With Respect To
See: World Wide Web
What You See is What You Get
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.
A data communications interface specification developed 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.
The CCITT and ISO standard for electronic mail. It is widely used
in Europe and Canada.
User Glossary Working Group [Page 50]RFC 1392 Internet Glossary January 1993
The CCITT and ISO standard for electronic directory services. See
also: white pages, Knowbot, WHOIS.
See: eXternal Data Representation
Xerox Network System (XNS)
A network developed by Xerox corporation. Implementations exist
for both 4.3BSD derived systems, as well as the Xerox Star
See: Xerox Network System
Yellow Pages (YP)
A service used by UNIX administrators to manage databases
distributed across a network.
See: Yellow Pages
A logical group of network devices (AppleTalk).
User Glossary Working Group [Page 51]RFC 1392 Internet Glossary January 1993
BIG-LAN "BIG-LAN Frequently Asked Questions Memo", BIG-LAN DIGEST
V4:I8, February 14, 1992.
COMER Comer, D., "Internetworking with TCP/IP: Principles,
Protocols and Architecture", Prentice Hall, Englewood Cliffs,
FYI4 Malkin, G., and A. Marine, "FYI on Questions and Answers:
Answers to Commonly asked "New Internet User" Questions", FYI
4, RFC 1325, Xylogics, SRI, May 1992.
HACKER "THIS IS THE JARGON FILE", Version 2.9.8, January 1992.
HPCC "Grand Challenges 1993: High Performance Computing and
Communications", Committee on Physical, Mathmatical and
Engineering Sciences of the Federal Coordinating Council for
Science, Engineering and Technology.
MALAMUD Malamud, C., "Analyzing Sun Networks", Van Nostrand Reinhold,
New York, NY, 1992.
NNSC "NNSC's Hypercard Tour of the Internet".
LAQUEY LaQuey, T. (with J. Ryer), "The Internet Companion: A
Beginner's Guide to Global Networking", Addison-Wesley,
Reading, MA, 1992.
NWNET Kochmer, J., and NorthWestNet, "The Internet Passport:
NorthWestNets Guide to Our World Online", NorthWestNet,
Bellevue, WA, 1992.
RFC1208 Jacobsen, O., and D. Lynch, "A Glossary of Networking Terms",
RFC 1208, Interop, Inc., March 1991.
STD1 Postel, J., "IAB Official Protocol Standards", STD 1, RFC
1360, Internet Architecture Board, September 1992.
STD2 Reynolds, J., and J. Postel, "Assigned Numbers", STD 2, RFC
1340, USC/Information Sciences Institute, July 1992.
TAN Tanenbaum, A., "Computer Networks; 2nd ed.", Prentice Hall,
Englewood Cliffs, NJ, 1989.
ZEN Kehoe, B., "Zen and the Art of the Internet", February 1992.
User Glossary Working Group [Page 52]RFC 1392 Internet Glossary January 1993
While security is not explicitly discussed in this document, some of
the glossary's entries are security related. See the entries for
Access Control List (ACL), authentication, Computer Emergency
Response Team (CERT), cracker, Data Encryption Key (DEK), Data
Encryption Standard (DES), encryption, Kerberos, Privacy Enhanced
Mail (PEM), Trojan Horse, virus, and worm.
Gary Scott Malkin
53 Third Avenue
Burlington, MA 01803
Phone: (617) 272-8140
Tracy LaQuey Parker
University of Texas at Austin
Austin, TX 78712
Phone: (512) 471-2444
User Glossary Working Group [Page 53]