Network Working Group G. Malkin, Editor
Request for Comments: 1983 Xylogics
FYI: 18 August 1996
Obsoletes: 1392
Category: Informational

Internet Users' Glossary

Status of this Memo

This memo provides information for the Internet community. This memo
does not specify an Internet standard of any kind. Distribution of
this memo is unlimited.

Abstract

There are many networking glossaries in existence. This glossary
concentrates on terms which are specific to the Internet. Naturally,
there are entries for some basic terms and acronyms because other
entries refer to them.

Acknowledgements

This document is the work of the User Glossary Working Group of the
User Services Area of the Internet Engineering Task Force. I would
especially like to thank Ryan Moats/InterNIC for his careful review
and many contributions to this document.

Table of Contents

non-letter . . 2 I . . . . . . . 26 R . . . . . . . 46
A . . . . . . . 2 J . . . . . . . 33 S . . . . . . . 49
B . . . . . . . 7 K . . . . . . . 33 T . . . . . . . 52
C . . . . . . . 10 L . . . . . . . 33 U . . . . . . . 55
D . . . . . . . 14 M . . . . . . . 35 V . . . . . . . 57
E . . . . . . . 18 N . . . . . . . 39 W . . . . . . . 57
F . . . . . . . 20 O . . . . . . . 42 X . . . . . . . 59
G . . . . . . . 22 P . . . . . . . 43 Y . . . . . . . 60
H . . . . . . . 23 Q . . . . . . . 46 Z . . . . . . . 60

References . . . . . . . . . . . . . . . . . . . . . . . . . . 61
Security Considerations . . . . . . . . . . . . . . . . . . . . 62
Editor's Address . . . . . . . . . . . . . . . . . . . . . . . 62

Glossary

10Base2
A physical layer communications specification for 10Mbps, baseband
data transmission over a coaxial cable (Thinnet) with a maximum
cable segment length of 200 meters.

10Base5
A physical layer communications specification for 10Mbps, baseband
data transmission over a coaxial cable (Thicknet) with a maximum
cable segment length of 500 meters.

10BaseF
A physical layer communications specification for 10Mbps, baseband
data transmission over a fiber-optic cable.

10BaseT
A physical layer communications specification for 10Mbps, baseband
data transmission over a twisted-pair copper wire.

802.x
The set of IEEE standards for the definition of LAN protocols.
See also: IEEE.

822
See: RFC822

:-)
This odd symbol is one of the ways a person can portray "mood" in
the very flat medium of computers--by using "smiley faces". This
is "metacommunication", and there are literally hundreds of sUCh
symbols, from the obvious to the obscure. This particular example
eXPresses "happiness". Don't see it? Tilt your head to the left
90 degrees. Smiles are also used to denote sarcasm.
[Source: ZEN]

abstract syntax
A description of a data structure that is independent of machine-
oriented structures and encodings.
[Source: RFC1208]

Abstract Syntax Notation One (ASN.1)
The language used by the OSI protocols for describing abstract
syntax. This language is also used to encode SNMP packets. ASN.1
is defined in ISO documents 8824.2 and 8825.2. See also: Basic
Encoding Rules.

Acceptable Use Policy (AUP)
Many transit networks have policies which restrict the use to
which the network may be put. For example, some networks may only
be used for non-commercial purposes. Some AUPs limit the type of
material which can be made available to the public (e.g.,
pornographic material). Enforcement of AUPs varies with the
network. See also: netiquette.

Access Control List (ACL)
Most network security systems operate by allowing selective use of
services. An Access Control List is the usual means by which
access to, and denial of, services is controlled. It is simply a
list of the services available, each with a list of the hosts
permitted to use the service.

ACK
See: Acknowledgment

acknowledgment (ACK)
A type of message sent to indicate that a block of data arrived at
its destination without error. See also: Negative
Acknowledgement.
[Source: NNSC]

ACL
See: Access Control List

AD
See: Administrative Domain

address
There are four types of addresses in common use within the
Internet. They are email address; IP, internet or Internet
address; hardware or MAC address; and URL. See also: email
address, IP address, internet address, MAC address, Uniform
Resource Locator.

address mask
A bit mask used to identify which bits in an IP address correspond
to the network and subnet portions of the address. This mask is
often referred to as the subnet mask because the network portion
of the address (i.e., the network mask) can be determined by the
encoding inherent in an IP address. See also: Classless Inter-
domain Routing.

address resolution
Conversion of a network-layer address (e.g. IP address) into the
corresponding physical address (e.g., MAC address). See also: IP
address, MAC address.

Address Resolution Protocol (ARP)
Used to dynamically discover the low level physical network
hardware address that corresponds to the high level IP address for
a given host. ARP is limited to physical network systems that
support broadcast packets that can be heard by all hosts on the
network. See also: proxy ARP, Reverse Address Resolution
Protocol.

Administrative Domain (AD)
A collection of hosts and routers, and the interconnecting
network(s), managed by a single administrative authority.

Advanced Research Projects Agency (ARPA)
An agency of the U.S. Department of Defense responsible for the
development of new technology for use by the military. ARPA
(formerly known as DARPA, nee ARPA) was responsible for funding
much of the development of the Internet we know today, including
the Berkeley version of Unix and TCP/IP.
[Source: NNSC]

Advanced Research Projects Agency Network (ARPANET)
A pioneering longhaul network funded by ARPA. Now retired, it
served as the basis for early networking research as well as a
central backbone during the development of the Internet. The
ARPANET consisted of individual packet switching computers
interconnected by leased lines. See also: Advanced Research
Projects Agency.
[Source: FYI4]

agent
In the client-server model, the part of the system that performs
information preparation and exchange on behalf of a client or
server application.
[Source: RFC1208]

alias
A name, usually short and easy to remember, that is translated
into another name, usually long and difficult to remember.

American National Standards Institute (ANSI)
This organization is responsible for approving U.S. standards in
many areas, including computers and communications. Standards
approved by this organization are often called ANSI standards

(e.g., ANSI C is the version of the C language approved by ANSI).
ANSI is a member of ISO. See also: International Organization for
Standardization.
[Source: NNSC]

American Standard Code for Information Interchange (ASCII)
A standard character-to-number encoding widely used in the
computer industry. See also: EBCDIC.

anonymous FTP
Anonymous FTP allows a user to retrieve documents, files,
programs, and other archived data from anywhere in the Internet
without having to establish a userid and passWord. By using the
special userid of "anonymous" the network user will bypass local
security checks and will have access to publicly accessible files
on the remote system. See also: archive site, File Transfer
Protocol, World Wide Web.

ANSI
See: American National Standards Institute

API
See: Application Program Interface

Appletalk
A networking protocol developed by Apple Computer for
communication between Apple Computer products and other computers.
This protocol is independent of the network layer on which it is
run. Current implementations exist for Localtalk, a 235Kb/s local
area network; and Ethertalk, a 10Mb/s local area network.
[Source: NNSC]

application
A program that performs a function directly for a user. FTP, mail
and Telnet clients are examples of network applications.

application layer
The top layer of the network protocol stack. The application
layer is concerned with the semantics of work (e.g. formatting
electronic mail messages). How to represent that data and how to
reach the foreign node are issues for lower layers of the network.
[Source: MALAMUD]

Application Program Interface (API)
A set of calling conventions which define how a service is invoked
through a software package.
[Source: RFC1208]

archie
A system to automatically gather, index and serve information on
the Internet. The initial implementation of archie provided an
indexed Directory of filenames from all anonymous FTP archives on
the Internet. Later versions provide other collections of
information. See also: archive site, Gopher, Prospero, Wide Area
Information Servers.

archive site
A machine that provides access to a collection of files across the
Internet. For example, an anonymous FTP archive site provides
access to arcived material via the FTP protocol. WWW servers can
also serve as archive sites. See also: anonymous FTP, archie,
Gopher, Prospero, Wide Area Information Servers, World Wide Web.

ARP
See: Address Resolution Protocol

ARPA
See: Advanced Research Projects Agency

ARPANET
See: Advanced Research Projects Agency Network

AS
See: Autonomous System

ASCII
See: American Standard Code for Information Interchange

ASN.1
See: Abstract Syntax Notation One

assigned numbers
The RFC[STD2] which documents the currently assigned values from
several series of numbers used in network protocol
implementations. This RFCis updated periodically and, in any
case, current information can be oBTained from the Internet
Assigned Numbers Authority (IANA). If you are developing a
protocol or application that will require the use of a link,
socket, port, protocol, etc., please contact the IANA to receive a
number assignment. See also: Internet Assigned Numbers Authority,
STD.
[Source: STD2]

Asynchronous Transfer Mode (ATM)
A standard which defines high-load, high-speed (1.544Mbps through
1.2Gbps), fixed-size packet (cell) switching with dynamic
bandwidth allocation. ATM is also known as "fast packet."

ATM
See: Asynchronous Transfer Mode

AUP
See: Acceptable Use Policy

authentication
The verification of the identity of a person or process.
[Source: MALAMUD]

Autonomous System (AS)
A collection of routers under a single administrative authority
using a common Interior Gateway Protocol for routing packets.

backbone
The top level in a hierarchical network. Stub and transit
networks which connect to the same backbone are guaranteed to be
interconnected. See also: stub network, transit network.

bandwidth
Technically, the difference, in Hertz (Hz), between the highest
and lowest frequencies of a transmission channel. However, as
typically used, the amount of data that can be sent through a
given communications circuit.

bang path
A series of machine names used to direct electronic mail from one
user to another, typically by specifying an explicit UUCP path
through which the mail is to be routed. See also: email address,
mail path, UNIX-to-UNIX CoPy.

baseband
A transmission medium through which digital signals are sent
without complicated frequency shifting. In general, only one
communication channel is available at any given time. Ethernet is
an example of a baseband network. See also: broadband, Ethernet.
[Source: NNSC]

Basic Encoding Rules (BER)
Standard rules for encoding data units described in ASN.1.
Sometimes incorrectly lumped under the term ASN.1, which properly
refers only to the abstract syntax description language, not the
encoding technique. See also: Abstract Syntax Notation One.
[Source: NNSC]

BBS
See: Bulletin Board System

BCNU
Be Seein' You

BCP
The newest subseries of RFCs which are written to describe Best
Current Practices in the Internet. Rather than specifying a
protocol, these documents specify the best ways to use the
protocols and the best ways to configure options to ensure
interoperability between various vendors' products. BCPs carry
the endorsement of the IESG. See also: Request For Comments,
Internet Engineering Steering Group.

BER
See: Basic Encoding Rules

Berkeley Internet Name Daemon (BIND)
Implementation of a DNS server developed and distributed by the
University of California at Berkeley. Many Internet hosts run
BIND, and it is the ancestor of many commercial BIND
implementations. See also: Domain Name System.

Berkeley Software Distribution (BSD)
Implementation of the UNIX operating system and its utilities
developed and distributed by the University of California at
Berkeley. "BSD" is usually preceded by the version number of the
distribution, e.g., "4.3 BSD" is version 4.3 of the Berkeley UNIX
distribution. Many Internet hosts run BSD software, and it is the
ancestor of many commercial UNIX implementations.
[Source: NNSC]

BGP
See: Border Gateway Protocol

big-endian
A format for storage or transmission of binary data in which the
most significant bit (or byte) comes first. The term comes from
"Gulliver's Travels" by Jonathan Swift. The Lilliputians, being
very small, had correspondingly small political problems. The

Big-Endian and Little-Endian parties debated over whether soft-
boiled eggs should be opened at the big end or the little end.
See also: little-endian.
[Source: RFC1208]

binary
11001001

BIND
See: Berkeley Internet Name Daemon

Birds Of a Feather (BOF)
A Birds Of a Feather (flocking together) is an informal discussion
group. It is formed, often ad hoc, to consider a specific issue
and, therefore, has a narrow focus. See also: Working Group.

Bitnet
An academic computer network that provides interactive electronic
mail and file transfer services, using a store-and-forward
protocol, based on IBM Network Job Entry protocols. Bitnet-II
encapsulates the Bitnet protocol within IP packets and depends on
the Internet to route them.

BOF
See: Birds Of a Feather

BOOTP
The Bootstrap Protocol, described in RFC1542, is used for booting
diskless nodes. See also: Dynamic Host Configuration Protocol,
Reverse Address Resolution Protocol.

Border Gateway Protocol (BGP)
The Border Gateway Protocol is an exterior gateway protocol
defined in RFC1771. It's design is based on experience gained
with EGP, as defined in RFC904, and EGP usage in the NSFNET
Backbone, as described in RFCs 1092 and 1093. See also: Exterior
Gateway Protocol.

bounce
The return of a piece of mail because of an error in its delivery.
[Source: ZEN]

bridge
A device which forwards traffic between network segments based on
datalink layer information. These segments would have a common
network layer address. See also: gateway, router.

broadband
A transmission medium capable of supporting a wide range of
frequencies. It can carry multiple signals by dividing the total
capacity of the medium into multiple, independent bandwidth
channels, where each channel operates only on a specific range of
frequencies. See also: baseband.

broadcast
A special type of multicast packet which all nodes on the network
are always willing to receive. See also: multicast, unicast.

broadcast storm
An incorrect packet broadcast onto a network that causes multiple
hosts to respond all at once, typically with equally incorrect
packets which causes the storm to grow exponentially in severity.
See also: Ethernet meltdown.

brouter
A device which bridges some packets (i.e. forwards based on
datalink layer information) and routes other packets (i.e.
forwards based on network layer information). The bridge/route
decision is based on configuration information. See also: bridge,
router.

BSD
See: Berkeley Software Distribution

BTW
By The Way

Bulletin Board System (BBS)
A computer, and associated software, which typically provides
electronic messaging services, archives of files, and any other
services or activities of interest to the bulletin board system's
operator. Although BBS's have traditionally been the domain of
hobbyists, an increasing number of BBS's are connected directly to
the Internet, and many BBS's are currently operated by government,
educational, and research institutions. See also: Electronic
Mail, Internet, Usenet.
[Source: NWNET]

Campus Wide Information System (CWIS)
A CWIS makes information and services publicly available on campus
via kiosks, and makes interactive computing available via kiosks,
interactive computing systems and campus networks. Services
routinely include directory information, calendars, bulletin
boards, databases.

CCIRN
See: Coordinating Committee for Intercontinental Research Networks

CCITT
See: Comite Consultatif International de Telegraphique et
Telephonique

CERT
See: Computer Emergency Response Team

checksum
A computed value which is dependent upon the contents of a packet.
This value is sent along with the packet when it is transmitted.
The receiving system computes a new checksum based upon the
received data and compares this value with the one sent with the
packet. If the two values are the same, the receiver has a high
degree of confidence that the data was received correctly. See
also: Cyclic Redundancy Check.
[Source: NNSC]

CIDR
See: Classless Inter-domain Routing

circuit switching
A communications paradigm in which a dedicated communication path
is established between two hosts, and on which all packets travel.
The telephone system is an example of a circuit switched network.
See also: connection-oriented, connectionless, packet switching.

Classless Inter-domain Routing (CIDR)
A proposal, set forth in RFC1519, to allocate IP addresses so as
to allow the addresses to be aggregated when advertised as routes.
It is based on the elimination of intrinsic IP network addresses;
that is, the determination of the network address based on the
first few bits of the IP address. See also: IP address, network
address, supernet.

client
A computer system or process that requests a service of another
computer system or process. A workstation requesting the contents
of a file from a file server is a client of the file server. See
also: client-server model, server.
[Source: NNSC]

client-server model
A common way to describe the paradigm of many network protocols.
Examples include the name-server/name-resolver relationship in DNS
and the file-server/file-client relationship in NFS. See also:
client, server, Domain Name System, Network File System.

CNI
See: Coalition for Networked Information

Coalition for Networked Information (CNI)
A consortium formed by American Research Libraries, CAUSE, and
EDUCOM (no, they are not acronyms) to promote the creation of, and
access to, information resources in networked environments in
order to enrich scholarship and enhance intellectual productivity.

Comite Consultatif International de Telegraphique et Telephonique (
CCITT)
This organization is now part of the International
Telecommunications Union and is responsible for making technical
recommendations about telephone and data communications systems.
Every four years CCITT holds plenary sessions where they adopt new
standards; the most recent was in 1992. Recently, the ITU
reorganized and CCITT was renamed the ITU-TSS. See also:
International Telecommunications Union - Telecommunications
Standards Sector.

Computer Emergency Response Team (CERT)
The CERT was formed by ARPA in November 1988 in response to the
needs exhibited during the Internet worm incident. The CERT
charter is to work with the Internet community to facilitate its
response to computer security events involving Internet hosts, to
take proactive steps to raise the community's awareness of
computer security issues, and to conduct research targeted at
improving the security of existing systems. CERT products and
services include 24-hour technical assistance for responding to
computer security incidents, product vulnerability assistance,
technical documents, and tutorials. In addition, the team
maintains a number of mailing lists (including one for CERT
Advisories), and provides an anonymous FTP server, at "cert.org",
where security-related documents and tools are archived. The CERT
may be reached by email at "cert@cert.org" and by telephone at
+1-412-268-7090 (24-hour hotline). See also: Advanced Research
Projects Agency, worm.

congestion
Congestion occurs when the offered load exceeds the capacity of a
data communication path.

connection-oriented
The data communication method in which communication proceeds
through three well-defined phases: connection establishment, data
transfer, connection release. TCP is a connection-oriented
protocol. See also: circuit switching, connectionless, packet
switching, Transmission Control Protocol.

connectionless
The data communication method in which communication occurs
between hosts with no previous setup. Packets between two hosts
may take different routes, as each is independent of the other.
UDP is a connectionless protocol. See also: circuit switching,
connection-oriented, packet switching, User Datagram Protocol.

Coordinating Committee for Intercontinental Research Networks (CCIRN)
A committee that includes the United States FNC and its
counterparts in North America and Europe. Co-chaired by the
executive directors of the FNC and the European Association of
Research Networks (RARE), the CCIRN provides a forum for
cooperative planning among the principal North American and
European research networking bodies. See also: Federal Networking
Council, RARE.
[Source: MALAMUD]

core gateway
Historically, one of a set of gateways (routers) operated by the
Internet Network Operations Center at Bolt, Beranek and Newman
(BBN). The core gateway system formed a central part of Internet
routing in that all groups must advertise paths to their networks
from a core gateway.
[Source: MALAMUD]

Corporation for Research and Educational Networking (CREN)
This organization was formed in October 1989, when Bitnet and
CSNET (Computer + Science NETwork) were combined under one
administrative authority. CSNET is no longer operational, but
CREN still runs Bitnet. See also: Bitnet.
[Source: NNSC]

cracker
A cracker is an individual who attempts to access computer systems
without authorization. These individuals are often malicious, as
opposed to hackers, and have many means at their disposal for
breaking into a system. See also: hacker, Computer Emergency
Response Team, Trojan Horse, virus, worm.

CRC
See: cyclic redundancy check

CREN
See: Corporation for Research and Educational Networking

CU-SeeMe
Pronnounced "See you, See me," CU-SeeMe is a publicly available
videoconferencing program developed at Cornell University. It
allows anyone with audio/video capabilites and an Internet
connection to videoconference with anyone else with the same
capabilities. It also allows multiple people to tie into the same
videoconference.

CWIS
See: Campus Wide Information system

Cyberspace
A term coined by William Gibson in his fantasy novel Neuromancer
to describe the "world" of computers, and the society that gathers
around them.
[Source: ZEN]

Cyclic Redundancy Check (CRC)
A number derived from a set of data that will be transmitted. By
recalculating the CRC at the remote end and comparing it to the
value originally transmitted, the receiving node can detect some
types of transmission errors. See also: checksum.
[Source: MALAMUD]

DANTE
A non-profit company founded in July 1993 to help the European
research community enhance their networking facilities. It
focuses on the establishment of a high-speed computer network
infrastructure.

DARPA
Defense Advanced Research Projects Agency
See: Advanced Research Projects Agency

Data Encryption Key (DEK)
Used for the encryption of message text and for the computation of
message integrity checks (signatures). See also: encryption.

Data Encryption Standard (DES)
A popular, standard encryption scheme. See also: encryption,
Pretty Good Privacy, RSA.

datagram
A self-contained, independent entity of data carrying sufficient
information to be routed from the source to the destination

computer without reliance on earlier exchanges between this source
and destination computer and the transporting network. See also:
frame, packet.
[Source: J. Postel]

DCA
See: Defense Information Systems Agency

DCE
Data Circuit-terminating Equipment

DCE
See: Distributed Computing Environment

DDN
See: Defense Data Network

DDN NIC
See: Defense Data Network Network Information Center

DECnet
A proprietary network protocol designed by Digital Equipment
Corporation. The functionality of each Phase of the
implementation, such as Phase IV and Phase V, is different.

default route
A routing table entry which is used to direct packets addressed to
networks not explicitly listed in the routing table.
[Source: MALAMUD]

Defense Data Network (DDN)
A global communications network serving the US Department of
Defense composed of MILNET, other portions of the Internet, and
classified networks which are not part of the Internet. The DDN
is used to connect military installations and is managed by the
Defense Information Systems Agency. See also: Defense Information
Systems Agency.

Defense Data Network Network Information Center (DDN NIC)
Previously called "The NIC", the DDN NIC's primary responsibility
was the assignment of Internet network addresses and Autonomous
System numbers, the administration of the root domain, and
providing information and support services to the Internet for the
DDN. Since the creation of the InterNIC, the DDN NIC performs
these functions only for the DDN. See also: Autonomous System,
network address, Internet Registry, InterNIC, Network Information
Center, Request For Comments.

Defense Information Systems Agency (DISA)
Formerly called the Defense Communications Agency (DCA), this is
the government agency responsible for managing the DDN portion of
the Internet, including the MILNET. Currently, DISA administers
the DDN, and supports the user assistance services of the DDN NIC.
See also: Defense Data Network.

DEK
See: Data Encryption Key

DES
See: Data Encryption Standard

dialup
A temporary, as opposed to dedicated, connection between machines
established over a phone line (analog or ISDN). See also:
Integrated Services Digital Network.

Directory Access Protocol
X.500 protocol used for communication between a Directory User
Agent and a Directory System Agent.
[Source: MALAMUD]

Directory System Agent (DSA)
The software that provides the X.500 Directory Service for a
portion of the directory information base. Generally, each DSA is
responsible for the directory information for a single
organization or organizational unit.
[Source: RFC1208]

Directory User Agent (DUA)
The software that accesses the X.500 Directory Service on behalf
of the directory user. The directory user may be a person or
another software element.
[Source: RFC1208]

DISA
See: Defense Information Systems Agency

Distributed Computing Environment (DCE)
An architecture of standard programming interfaces, conventions,
and server functionalities (e.g., naming, distributed file system,
remote procedure call) for distributing applications transparently
across networks of heterogeneous computers. Promoted and
controlled by the Open Software Foundation (OSF), a consortium led
by Digital, IBM and Hewlett Packard.
[Source: RFC1208]

distributed database
A collection of several different data repositories that looks
like a single database to the user. A prime example in the
Internet is the Domain Name System.

DIX Ethernet
See: Ethernet

DNS
See: Domain Name System

domain
"Domain" is a heavily overused term in the Internet. It can be
used in the Administrative Domain context, or the Domain Name
context. See also: Administrative Domain, Domain Name System.

Domain Name System (DNS)
The DNS is a general purpose distributed, replicated, data query
service. The principal use is the lookup of host IP addresses
based on host names. The style of host names now used in the
Internet is called "domain name", because they are the style of
names used to look up anything in the DNS. Some important domains
are: .COM (commercial), .EDU (educational), .NET (network
operations), .GOV (U.S. government), and .MIL (U.S. military).
Most countries also have a domain. The country domain names are
based on ISO 3166. For example, .US (United States), .UK (United
Kingdom), .AU (Australia). See also: Fully Qualified Domain Name,
Mail Exchange Record.

dot address (dotted decimal notation)
Dot address refers to the common notation for IP addresses of the
form A.B.C.D; where each letter represents, in decimal, one byte
of a four byte IP address. See also: IP address.
[Source: FYI4]

DSA
See: Directory System Agent

DTE
Data Terminal Equipment

DUA
See: Directory User Agent

dynamic adaptive routing
Automatic rerouting of traffic based on a sensing and analysis of
current actual network conditions. NOTE: this does not include
cases of routing decisions taken on predefined information.
[Source: J. Postel]

E1
The basic building block for European multi-megabit data rates,
with a bandwidth of 2.048Mbps. See also: T1.

E3
A European standard for transmitting data at 57.344Mbps. See
also: T3.

EARN
European Academic and Research Network. See: Trans-European
Research and Education Networking Association.

EBCDIC
See: Extended Binary Coded Decimal Interchange Code

Ebone
A pan-European backbone service.

EFF
See: Electronic Frontier Foundation

EGP
See: Exterior Gateway Protocol

Electronic Frontier Foundation (EFF)
A foundation established to address social and legal issues
arising from the impact on society of the increasingly pervasive
use of computers as a means of communication and information
distribution.

Electronic Mail (email)
A system whereby a computer user can exchange messages with other
computer users (or groups of users) via a communications network.
Electronic mail is one of the most popular uses of the Internet.
[Source: NNSC]

email
See: Electronic mail

email address
The domain-based or UUCP address that is used to send electronic
mail to a specified destination. For example an editor's address

is "gmalkin@xylogics.com". See also: bang path, mail path, UNIX-
to-UNIX CoPy.
[Source: ZEN]

encapsulation
The technique used by layered protocols in which a layer adds
header information to the protocol data unit (PDU) from the layer
above. For example, in Internet terminology, a packet would
contain a header from the physical layer, followed by a header
from the datalink layer (e.g. Ethernet), followed by a header
from the network layer (IP), followed by a header from the
transport layer (e.g. TCP), followed by the application protocol
data.
[Source: RFC1208]

encryption
Encryption is the manipulation of a packet's data in order to
prevent any but the intended recipient from reading that data.
There are many types of data encryption, and they are the basis of
network security. See also: Data Encryption Standard.

error checking
The examination of received data for transmission errors. See
also: checksum, Cyclic Redundancy Check.

Ethernet
A 10-Mb/s standard for LANs, initially developed by Xerox, and
later refined by Digital, Intel and Xerox (DIX). All hosts are
connected to a coaxial cable where they contend for network access
using a Carrier Sense Multiple Access with Collision Detection
(CSMA/CD) paradigm. See also: 802.x, Local Area Network, token
ring.

Ethernet meltdown
An event that causes saturation, or near saturation, on an
Ethernet. It usually results from illegal or misrouted packets
and typically lasts only a short time. See also: broadcast storm.
[Source: COMER]

Extended Binary Coded Decimal Interchange Code (EBCDIC)
A standard character-to-number encoding used primarily by IBM
computer systems. See also: ASCII.

Exterior Gateway Protocol (EGP)
A protocol which distributes routing information to the routers
which connect autonomous systems. The term "gateway" is
historical, as "router" is currently the preferred term. There is
also a routing protocol called EGP defined in RFC904. See also:

Autonomous System, Border Gateway Protocol, Interior Gateway
Protocol.

eXternal Data Representation (XDR)
A standard for machine independent data structures developed by
Sun Microsystems and defined in RFCs 1014 and 1832. It is similar
to ASN.1. See also: Abstract Syntax Notation One.
[Source: RFC1208]

FARNET
A non-profit corporation, established in 1987, whose mission is to
advance the use of computer networks to improve research and
education.

FAQ
Frequently Asked Question

FDDI
See: Fiber Distributed Data Interface

Federal Information Exchange (FIX)
One of the connection points between the American governmental
internets and the Internet.
[Source: SURA]

Federal Networking Council (FNC)
The coordinating group of representatives from those federal
agencies involved in the development and use of federal
networking, especially those networks using TCP/IP and the
Internet. Current members include representatives from DOD, DOE,
ARPA, NSF, NASA, and HHS. See also: Advanced Research Projects
Agency, National Science Foundation.

Fiber Distributed Data Interface (FDDI)
A high-speed (100Mb/s) LAN standard. The underlying medium is
fiber optics, and the topology is a dual-attached, counter-
rotating token ring. See also: Local Area Network, token ring.
[Source: RFC1208]

file transfer
The copying of a file from one computer to another over a computer
network. See also: File Transfer Protocol, Kermit, Gopher, World
Wide Web.

File Transfer Protocol (FTP)
A protocol which allows a user on one host to access, and transfer
files to and from, another host over a network. Also, FTP is
usually the name of the program the user invokes to execute the
protocol. See also: anonymous FTP.

finger
A protocol, defined in RFC1288, that allows information about a
system or user on a system to be retrived. Finger also refers to
the commonly used program which retrieves this information.
Information about all logged in users, as well is information
about specific users may be retrieved from local or remote
systems. Some sites consider finger to be a security risk and
have either disabled it, or replaced it with a simple message.

FIX
See: Federal Information Exchange

flame
A strong opinion and/or criticism of something, usually as a frank
inflammatory statement, in an electronic mail message. It is
common to precede a flame with an indication of pending fire (i.e.
FLAME ON!). Flame Wars occur when people start flaming other
people for flaming when they shouldn't have. See also: Electronic
Mail, Usenet.

FLEA
See: Four Letter Extended Acronym

FNC
See: Federal Networking Council

Four Letter Extended Acronym (FLEA)
A recognition of the fact that there are far too many TLAs. See
also: Three Letter Acronym.

FQDN
See: Fully Qualified Domain Name

fragment
A piece of a packet. When a router is forwarding an IP packet to
a network that has a maximum transmission unit smaller than the
packet size, it is forced to break up that packet into multiple
fragments. These fragments will be reassembled by the IP layer at
the destination host. See also: Maximum Transmission Unit.

fragmentation
The IP process in which a packet is broken into smaller pieces to
fit the requirements of a physical network over which the packet
must pass. See also: reassembly.

frame
A frame is a datalink layer "packet" which contains the header and
trailer information required by the physical medium. That is,
network layer packets are encapsulated to become frames. See
also: datagram, encapsulation, packet.

freenet
Community-based bulletin board system with email, information
services, interactive communications, and conferencing. Freenets
are funded and operated by individuals and volunteers -- in one
sense, like public television. They are part of the National
Public Telecomputing Network (NPTN), an organization based in
Cleveland, Ohio, devoted to making computer telecommunication and
networking services as freely available as public libraries.
[Source: LAQUEY]

FTP
See: File Transfer Protocol

Fully Qualified Domain Name (FQDN)
The FQDN is the full name of a system, rather than just its
hostname. For example, "venera" is a hostname and
"venera.isi.edu" is an FQDN. See also: hostname, Domain Name
System.

FYI
For Your Information

FYI
A subseries of RFCs that are not technical standards or
descriptions of protocols. FYIs convey general information about
topics related to TCP/IP or the Internet. See also: Request For
Comments.

gated
Gatedaemon. A program which supports multiple routing protocols
and protocol families. It may be used for routing, and makes an
effective platform for routing protocol research. The software is
freely available by anonymous FTP from "gated.cornell.edu".
Pronounced "gate-dee". See also: Exterior Gateway Protocol, Open
Shortest-Path First, Routing Information Protocol, routed.

gateway
The term "router" is now used in place of the original definition
of "gateway". Currently, a gateway is a communications
device/program which passes data between networks having similar
functions but dissimilar implementations. This should not be
confused with a protocol converter. By this definition, a router
is a layer 3 (network layer) gateway, and a mail gateway is a
layer 7 (application layer) gateway. See also: mail gateway,
router, protocol converter.

Gopher
A distributed information service, developed at the University of
Minnesota, that makes hierarchical collections of information
available across the Internet. Gopher uses a simple protocol,
defined in RFC1436, that allows a single Gopher client to access
information from any accessible Gopher server, providing the user
with a single "Gopher space" of information. Public domain
versions of the client and server are available. See also:
archie, archive site, Prospero, Wide Area Information Servers.

GOSIP
See: Government OSI Profile

Government OSI Profile (GOSIP)
A subset of OSI standards specific to U.S. Government
procurements, designed to maximize interoperability in areas where
plain OSI standards are ambiguous or allow excessive options.

hacker
A person who delights in having an intimate understanding of the
internal workings of a system, computers and computer networks in
particular. The term is often misused in a pejorative context,
where "cracker" would be the correct term. See also: cracker.

header
The portion of a packet, preceding the actual data, containing
source and destination information. It may also error checking and
other fields. A header is also the part of an electronic mail
message which precedes the body of a message and contains, among
other things, the message originator, date and time. See also:
Electronic Mail, packet, error checking.

heterogeneous network
A network running multiple network layer protocols. See also:
DECnet, IP, IPX, XNS, homogeneous network.

hierarchical routing
The complex problem of routing on large networks can be simplified
by reducing the size of the networks. This is accomplished by
breaking a network into a hierarchy of networks, where each level
is responsible for its own routing. The Internet has, basically,
three levels: the backbones, the mid-levels, and the stub
networks. The backbones know how to route between the mid-levels,
the mid-levels know how to route between the sites, and each site
(being an autonomous system) knows how to route internally. See
also: Autonomous System, Exterior Gateway Protocol, Interior
Gateway Protocol, stub network, transit network.

High Performance Computing and Communications (HPCC)
High performance computing encompasses advanced computing,
communications, and information technologies, including scientific
workstations, supercomputer systems, high speed networks, special
purpose and experimental systems, the new generation of large
scale parallel systems, and application and systems software with
all components well integrated and linked over a high speed
network.
[Source: HPCC]

High Performance Parallel Interface (HIPPI)
An emerging ANSI standard which extends the computer bus over
fairly short distances at speeds of 800 and 1600 Mb/s. HIPPI is
often used in a computer room to connect a supercomputer to
routers, frame buffers, mass-storage peripherals, and other
computers. See also: American National Standards Institute
[Source: MALAMUD]

HIPPI
See: High Performance Parallel Interface

Html
See: Hypertext Markup Language

homogeneous network
A network running a single network layer protocol. See also:
DECnet, IP, IPX, XNS, heterogeneous network.

hop
A term used in routing. A path to a destination on a network is a
series of hops, through routers, away from the origin.

host
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.
[Source: NNSC]

host address
See: internet address

hostname
The name given to a machine. See also: Fully Qualified Domain
Name.
[Source: ZEN]

host number
See: host address

HPCC
See: High Performance Computing and Communications

HTTP
See: Hypertext Transfer Protocol

hub
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
network.
[Source: MALAMUD]

hyperlink
A pointer within a hypertext document which points (links) to
another document, which may or may not also be a hypertext
document. See also: hypertext.

hypertext
A document, written in HTML, which contains hyperlinks to other
documents, which may or may not also be hypertext documents.
Hypertext documents are usually retrieved using WWW. See also:
hyperlink, Hypertext Markup Language, World Wide Web.

Hypertext Markup Language (HTML)
The language used to create hypertext documents. It is a subset
of SGML and includes the mechanisms to establish hyperlinks to
other documents. See also: hypertext, hyperlink, Standardized
General Markup Language.

Hypertext Transfer Protocol (HTTP)
The protocol used by WWW to transfer HTML files. A formal
standard is still under development in the IETF. See also:
hyperlink, hypertext, Hypertext Markup Language, World Wide Web.

I-D
See: Internet-Draft

IAB
See: Internet Architecture Board

IANA
See: Internet Assigned Numbers Authority

ICMP
See: Internet Control Message Protocol

IEEE
Institute of Electrical and Electronics Engineers

IEEE 802
See: 802.x

IEN
See: Internet Experiment Note

IEPG
See: Internet Engineering Planning Group

IESG
See: Internet Engineering Steering Group

IETF
See: Internet Engineering Task Force

IINREN
See: Interagency Interim National Research and Education Network

IGP
See: Interior Gateway Protocol

IMHO
In My Humble Opinion

IMR
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.
[Source: RFC1208]

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
gigabit NREN.
[Source: HPCC]

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
Interconnection, router.

Intermediate System-Intermediate System (IS-IS)
The OSI IGP. See also: Open Systems Interconnection, Interior
Gateway Protocol.

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.
[Source: TAN]

International Telecommunications Union (ITU)
An agency of the United Nations which coordinates the various
national telecommunications standards so that people in one
country can communicate with people in another country.

International Telecommunications Union -
Telecommunications Standards Sector (ITU-TSS)
The new name for CCITT since the ITU reorganization. The function
is the same; only the name has been changed

internet
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.

Internet
(note the capital "I") The Internet is the largest internet in the
world. Is a three level hierarchy composed of backbone networks
(e.g. Ultranet), mid-level networks (e.g., NEARnet) and stub
networks. The Internet is a multiprotocol internet. See also:
backbone, mid-level network, stub network, transit network,
Internet Protocol.

internet address
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 IAB has been many things over the years. Originally the
Internet Activities Board, it was responsible for the development
of the protocols which make up the Internet. It later changed its
name and charter to become the group most responsible for the
architecture of the Internet, leaving the protocol details to the
IESG. In June of 1992, it was chartered as a component of the
Internet Society; this is the charter it holds today. The IAB is
responsible for approving nominations to the IESG, architectural
oversight for Internet Standard Protocols, IETF standards process
oversight and appeals, IANA and RFCactivities, and liaison to
peer standards groups (e.g., ISO). See also: Internet Engineering
Task Force, Internet Research Task Force, Internet Engineering
Steering Group, Internet Assigned Numbers Authority, Request for
Comments.

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 "iana@isi.edu". 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.
[Source: FYI4]

Internet-Draft (I-D)
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.

Internet Engineering Planning Group (IEPG)
A group, primarily composed of Internet service operators, whose
goal is to promote a globally coordinated Internet operating
environment. Membership is open to all.

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.
[Source: FYI4]

Internet Experiment Note (IEN)
A series of reports pertinent to the Internet. IENs were
published in parallel to RFCs and were intended to be "working
documents." They have been replaced by Internet-Drafts and are
currently of historic value only. 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
organizations.

internet number
See: internet address

Internet Protocol (IP, IPv4)
The Internet Protocol (version 4), defined in RFC791, is the
network layer for the TCP/IP Protocol Suite. It is a
connectionless, best-effort packet switching protocol. See also:
packet switching, TCP/IP Protocol Suite, Internet Protocol Version
6.

Internet Protocol Version 6 (IPng, IPv6)
IPv6 (version 5 is a stream protocol used for special
applications) is a new version of the Internet Protocol which is
designed to be an evolutionary step from its predecessor, version
4. There are many RFCs defining various portions of the protocol,
its auxiliary protocols, and the transition plan from IPv4. The
core RFCs are 1883 through 1886. The name IPng (IP next
generation) is a nod to STNG (Star Trek Next Generation).

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
servers, each of which accepts connections from client programs,
one per user. See also: talk.
[Source: HACKER]

Internet Research Steering Group (IRSG)
The "governing body" of the IRTF. See also: Internet Research
Task Force.
[Source: MALAMUD]

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.

InterNIC
A five year project, partially supported by the National Science
Foundation, to provide network information services to the
networking community. The InterNIC began operations in April of
1993 and is now a collaborative project of two organizations:
AT&T, which provides Directory and Database Services from South
Plainsfield, NJ; and Network Solutions, Inc., which provides
Registration Services from their headquarters in Herndon, VA.
Services are provided via the Internet, and by telephone, FAX, and
hardcopy.

interoperability
The ability of software and hardware on multiple machines from
multiple vendors to communicate meaningfully.

IP (IPv4)
See: Internet Protocol

IPng (IPv6)
See: Internet Protocol Version 6

IP address
The 32-bit address defined by the Internet Protocol in RFC791.
It is usually represented in dotted decimal notation. See also:
dot address, internet address, Internet Protocol, network address,
subnet address, host address.

IP datagram
See: datagram

IPX
See: Internetwork Packet eXchange

IR
See: Internet Registry

IRC
See: Internet Relay Chat

IRSG
See: Internet Research Steering Group

IRTF
See: Internet Research Task Force

IS
See: Intermediate System

IS-IS
See: Intermediate System-Intermediate System

ISDN
See: Integrated Services Digital Network

ISO
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.

ISOC
See: Internet Society

ISODE
See: ISO Development Environment

ITU
See: International Telecommunications Union -
Telecommunications Standards Sector

ITU-TSS
See: International Telecommunications Union

JKREY
Joyce K. Reynolds

KA9Q
A popular implementation of TCP/IP and associated protocols for
amateur packet radio systems. See also: TCP/IP Protocol Suite.
[Source: RFC1208]

Kerberos
Kerberos is the security system of MIT's Project Athena. It is
based on symmetric key cryptography. See also: encryption.

Kermit
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
[Source: MALAMUD]

Knowbot
A "Knowledge Robot" is a program which seeks out information based
on specified criteria. "Knowbot," as trademarked by CNRI, refers
specifically to the search engine for Knowbot Information
Services. See also: Corporation for National Research
Initiatives, X.500, white pages, whois, netfind.

Knowbot Information Services
An experimental directory service. See also: white pages, whois,
X.500.

LAN
See: Local Area Network

layer
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.

LDAP
See: Lightweight Directory Access Protocol

Lightweight Directory Access Protocol
This protocol provides access for management and browser
applications that provide read/write interactive access to the
X.500 Directory. See also: X.500.

link
A pointer which may be used to retreive the file or data to which
the pointer points.

list server
An automated mailing list distribution system. List servers
handle the administrivia of mailing list maintenance, such as the
adding and deleting of list members.

little-endian
A format for storage or transmission of binary data in which the
least significant byte (bit) comes first. See also: big-endian.
[Source: RFC1208]

LLC
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,
Metropolitan Area Network, Wide Area Network.
[Source: NNSC]

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
Access Control.

Lurking
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.
[Source: LAQUEY]

Lycos
Lycos, Inc. is a new venture formed in late June 1995, to develop
and market the Lycos technology originally developed under the
direction of Dr. Michael ("Fuzzy") Mauldin at Carnegie Mellon
University. The part of Lycos you see when you do a search is the
search engine. "Lycos" comes from Lycosidae, a cosmopolitan
family of relatively large active ground spiders (Wolf Spiders)
that catch their prey by pursuit, rather than in a web.
[Source: Lycos's FAQ]

MAC
See: Media Access Control

MAC address
The hardware address of a device connected to a shared media. See
also: Media Access Control, Ethernet, token ring.
[Source: MALAMUD]

mail bridge
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
gateway.
[Source: NNSC]

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
Mail.
[Source: MALAMUD]

mail exploder
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.
[Source: RFC1208]

mail gateway
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.
[Source: RFC1208]

mail path
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
CoPy.

mail server
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,
FTP.
[Source: NWNET]

mailing list
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
should ALWAYS be sent to the list's "-request" address (e.g.
ietf-request@cnri.reston.va.us for the IETF mailing list) or
majordomo server. See also: Electronic Mail, mail exploder, email
address, moderator, majordomo.

majordomo
A program which handles mailing list maintenance (affectionately
known as administrivia) such as adding and removing addresses from
mailing lists. See also: email address, mailing list.

MAN
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.
[Source: BIG-LAN]

Martian
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.
[Source: RFC1208]

Maximum Transmission Unit (MTU)
The largest frame length which may be sent on a physical medium.
See also: frame, fragment, fragmentation.

mbone
The Multicast Backbone is based on IP multicasting using class-D
addresses. The mbone concept was adopted at the March 1992 IETF
in San Diego, during which it was used to audiocast to 40 people
throughout the world. At the following meeting, in Cambridge, the
name mbone was adopted. Since then the audiocast has become full
two-way audio/video conferencing using two video channels, four
audio channels, and involving hundreds of remote users. See also:
multicast, Internet Engineering Task Force.

MD-2, MD-4, MD-5
See: Message Digest

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.

Message Digest (MD-2, MD-4, MD-5)
Message digests are algorithmic operations, generally performed on
text, which produce a unique signature for that text. MD-2,
described in RFC1319 MD-4, described in RFC1320 and MD-5,
described in RFC1321 all produce a 128-bit signature. They
differ in their operating speed and resistance to crypto-analytic
attack. Generally, one must be traded off for the other.

message switching
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.
[Source: NNSC]

MIB
See: Management Information Base

Microcom Networking Protocol (MNP)
A series of protocols built into most modems which error-check or
compress data being transmitted over a phone line.

mid-level network
Mid-level networks (a.k.a. regionals) make up the second level of
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.

MIME
See: Multipurpose Internet Mail Extensions

MNP
See: Microcom Networking Protocol

moderator
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.

MOSPF
Multicast Open Shortest-Path First. See: Open Shortest-Path First.

MTU
See: Maximum Transmission Unit

MUD
See: Multi-User Dungeon

multicast
A packet with a special destination address which multiple nodes
on the network may be willing to receive. See also: broadcast,
unicast.

multihomed host
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.
[Source: MALAMUD]

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. 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.
[Source: LAQUEY]

MX Record
See: Mail Exchange Record

NAK
See: Negative Acknowledgment

name resolution
The process of mapping a name into its corresponding address. See
also: Domain Name System.
[Source: RFC1208]

namespace
A commonly distributed set of names in which all names are unique.
[Source: MALAMUD]

National Institute of Standards and Technology (NIST)
United States governmental body that provides assistance in
developing standards. Formerly the National Bureau of Standards.
[Source: MALAMUD]

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.
[Source: HPCC]

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, was once an essential part
of academic and research communications. It was a highspeed,
hierarchical "network of networks." At the highest level, it had
a backbone network of nodes, interconnected with T3 (45Mbps)
facilities which spaned the continental United States. Attached
to that were mid-level networks, and attached to the mid-levels
were campus and local networks. See also: backbone network, mid-
level network.

Negative Acknowledgment (NAK)
Response to the receipt of either a corrupted or unnexpected
packet of information. See also: Acknowledgement.

netfind
A research prototype to provide a simple Internet "white pages"
user directory. Developed at the University of Colorado, Boulder,
it tries to locate telephone and email information given a
person's name and a rough description of where the person works.
See also: Knowbot, whois, white pages, X.500.
[Source: Ryan Moats]

netiquette
A pun on "etiquette" referring to proper behavior on a network.
RFC1855 (FYI 28) contains a netiquette guide produced by the User
Services area of the IETF. See also: Acceptable Use Policy,
Internet Engineering Task Force.

Netnews
See: Usenet

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.
See also: Local Area Network, Metropolitan Area Network, Wide Area
Network, internet.

network address
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 RFC1094
(RFC1813 defines Version 3), 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.
[Source: NNSC]

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 RFC977, for the distribution, inquiry,
retrieval, and posting of news articles. See also: Usenet.

network mask
See: address mask

network number
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.
[Source: NNSC]

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. See also: Internet.
[Source: NNSC]

NFS
See: Network File System

NIC
See: Network Information Center

NIC.DDN.MIL
This is the domain name of the DDN NIC. See also: Defense Data
Network, Domain Name System, Network Information Center.

NIS
See: Network Information Services

NIST
See: National Institute of Standards and Technology

NNTP
See: Network News Transfer Protocol

NOC
See: Network Operations Center

Nodal Switching System (NSS)
Main routing nodes in the NSFnet backbone. See also: backbone,
National Science Foundation.
[Source: MALAMUD]

node
An addressable device attached to a computer network. See also:
host, router.

NREN
See: National Research and Education Network

NSF
See: National Science Foundation

NSS
See: Nodal Switching System

NTP
See: Network Time Protocol

OCLC
See: Online Computer Library Catalog

octet
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.
[Source: OCLC]

Open Shortest-Path First (OSPF)
A link state, as opposed to distance vector, routing protocol. It
is an Internet standard IGP defined in RFCs 1583 and 1793. The
multicast version, MOSPF, is defined in RFC1584. 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.

OSI
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
Standardization.
[Source: NNSC]

OSPF
See: Open Shortest-Path First

packet
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
used as a verb: "Ping host X to see if it is up!" See also:
Internet Control Message Protocol.
[Source: RFC1208]

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,
router.
[Source: NNSC]

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-
oriented, connectionless.

PD
Public Domain

PDU
See: Protocol Data Unit

PEM
See: Privacy Enhanced Mail

PGP
See: Pretty Good Privacy

PING
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
routers.

Point-to-Point Protocol (PPP)
The Point-to-Point Protocol, defined in RFC1661, provides a
method for transmitting packets over serial point-to-point links.
There are many other RFCs which define extensions to the basic
protocol. See also: Serial Line IP.
[Source: FYI4]

POP
See: Post Office Protocol and Point Of Presence

port
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.

Post Office Protocol (POP)
A protocol designed to allow single user hosts to read electronic
mail from a server. Version 3, the most recent and most widely
used, is defined in RFC1725. See also: Electronic Mail.

Postal Telegraph and Telephone (PTT)
Outside the USA, PTT refers to a telephone service provider, which
is usually a monopoly, in a particular country.

postmaster
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.
[Source: ZEN]

PPP
See: Point-to-Point Protocol

Pretty Good Privacy (PGP)
A program, developed by Phil Zimmerman, which cryptographically
protects files and electronic mail from being read by others. It
may also be used to digitally sign a document or message, thus
authenticating the creator. See also: encryption, Data Encryption
Standard, RSA.

Privacy Enhanced Mail (PEM)
Internet email which provides confidentiality, authentication and
message integrity using various encryption methods. See also:
Electronic Mail, encryption.

Prospero
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.

protocol
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).
[Source: MALAMUD]

protocol converter
A device/program which translates between different protocols
which serve similar functions (e.g. TCP and TP4).

Protocol Data Unit (PDU)
"PDU" is internationalstandardscomitteespeak for packet. See
also: packet.

protocol stack
A layered set of protocols which work together to provide a set of
network functions. See also: layer, protocol.

proxy ARP
The technique in which one machine, usually a router, answers ARP
requests intended for another machine. By "faking" its identity,
the router accepts responsibility for routing packets to the
"real" destination. Proxy ARP allows a site to use a single IP
address with two physical networks. Subnetting would normally be
a better solution. See also: Address Resolution Protocol
[Source: RFC1208]

PSN
See: Packet Switch Node.

PTT
See: Postal, Telegraph and Telephone

queue
A backup of packets awaiting processing.

RARE
Reseaux Associes pour la Recherche Europeenne. See: Trans-
European Research and Education Networking Association.

RARP
See: Reverse Address Resolution Protocol

RBOC
Regional Bell Operating Company

Read The F*cking Manual (RTFM)
This acronym is often used when someone asks a simple or common
question.

Read The Source Code (RTSC)
This acronym is often used when a software developer asks a
question about undocumented code.

reassembly
The IP process in which a previously fragmented packet is
reassembled before being passed to the transport layer. See also:
fragmentation.

recursive
See: recursive

regional
See: mid-level network

remote login
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.
[Source: RFC1208]

repeater
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 RFCseries 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: BCP,
FYI, STD.

Reseaux IP Europeens (RIPE)
A collaboration between European networks which use the TCP/IP
protocol suite.

Reverse Address Resolution Protocol (RARP)
A protocol, defined in RFC903, 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.

RFC
See: Request For Comments

RFC822
The Internet standard format for electronic mail message headers.
Mail experts often refer to "822 messages." The name comes from
RFC822, which contains the specification. 822 format was
previously known as 733 format. See also: Electronic Mail.
[Source: COMER]

RIP
See: Routing Information Protocol

RIPE
See: Reseaux IP Europeenne

Round-Trip Time (RTT)
A measure of the current delay on a network.
[Source: MALAMUD]

route
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
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,
gated.

router
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.

routing
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.

routing domain
A set of routers exchanging routing information within an
administrative domain. See also: Administrative Domain, router.

Routing Information Protocol (RIP)
A distance vector, as opposed to link state, routing protocol. It
is an Internet standard IGP defined in RFC1058. See also:
Interior Gateway Protocol, Open Shortest-Path First.

RPC
See: Remote Procedure Call

RSA
A public-key cryptographic system which may be used for encryption
and authentication. It was invented in 1977 and named for its
inventors: Ron Rivest, Adi Shamir, and Leonard Adleman. See also:
encryption, Data Encryption Standard, Pretty Good Privacy.

RTFM
See: Read The F*cking Manual

RTSC
See: Read The Source Code

RTT
See: Round-Trip Time

SDH
See: Synchronous Digital Hierarchy

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 RFC1055, but is not an Internet Standard. It is being
replaced by PPP. See also: Point-to-Point Protocol.

server
A provider of resources (e.g. file servers and name servers). See
also: client, Domain Name System, Network File System.

SGML
See: Standardized Generalized Markup Language

SIG
Special Interest Group

signature
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 used to transfer electronic mail between computers. It
is specified in RFC821, with extensions specified in many other
RFCs. It is a server to server protocol, so other protocols are
used to access the messages. See also: Electronic Mail, Post
Office Protocol, RFC822.

Simple Network Management Protocol (SNMP)
The Internet standard protocol developed to manage nodes on an IP
network. The first version is defined in RFC1157 (STD 15).
SNMPv2 (version 2) is defined in too many RFCs to list. It is
currently possible to manage wiring hubs, toasters, jukeboxes,
etc. See also: Management Information Base.

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
A pejorative term referring to the U.S. postal service.

SNMP
See: Simple Network Management Protocol

SONET
See: Synchronous Optical NETwork

Standardized Generalized Markup Language (SGML)
An international standard for the definition of system-
independent, device-independent methods of representing text in
electronic form. See also: Hypertext Markup Language.

STD
A subseries of RFCs that specify Internet standards. The official
list of Internet standards is in STD 1. See also: Request For
Comments.

stream-oriented
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
Protocol.
[Source: MALAMUD]

Structure of Management Information (SMI)
The rules used to define the objects that can be accessed via a
network management protocol. These rules are defined in RFC1155
(STD 17). The acronym is pronounced "Ess Em Eye." See also:
Management Information Base. .br [Source: RFC1208]

stub network
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.

subnet
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.
[Source: FYI4]

subnet address
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.

subnet mask
See: address mask

subnet number
See: subnet address

supernet
An aggregation of IP network addresses advertised as a single
classless network address. For example, given four Class C IP
networks: 192.0.8.0, 192.0.9.0, 192.0.10.0 and 192.0.11.0, each
having the intrinsic network mask of 255.255.255.0; one can
advertise the address 192.0.8.0 with a subnet mask of
255.255.252.0. See also: IP address, network address, network
mask, Classless Inter-domain Routing.

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.
[Source: RFC1208]

Synchronous Digital Hierarchy (SDH)
The European standard for high-speed data communications over
fiber-optic media. The transmission rates range from 155.52Mbps
to 2.5Gbps.

Synchronous Optical NETwork (SONET)
SONET is an international standard for high-speed data
communications over fiber-optic media. The transmission rates
range from 51.84Mbps to 2.5Gbps.

Systems Network Architecture (SNA)
A proprietary networking architecture used by IBM and IBM-
compatible mainframe computers.
[Source: NNSC]

T1
A term for a digital carrier facility used to transmit a DS-1
formatted digital signal at 1.544 megabits per second.

T3
A term for a digital carrier facility used to transmit a DS-3
formatted digital signal at 44.746 megabits per second.
[Source: FYI4]

TAC
See: Terminal Access Controller (TAC)

talk
A protocol which allows two people on remote computers to
communicate in a real-time fashion. See also: Internet Relay
Chat.

TCP
See: Transmission Control Protocol

TCP/IP Protocol Suite
Transmission Control Protocol over Internet Protocol. This is a
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.

TELENET
The original name for what is now SprintNet. It should not be
confused with the Telnet protocol or application program.

Telnet
Telnet is the Internet standard protocol for remote terminal
connection service. It is defined in RFC854 and extended with
options by many other RFCs.

TERENA
See: Trans-European Research and Education Networking Association

Terminal Access Controller (TAC)
A device which was once used to connect terminals to the Internet,
usually using dialup modem connections and the TACACS protocol.
While the device is no longer in use, TACACS+ is a protocol in
current use.

terminal emulator
A program that allows a computer to emulate a terminal. The
workstation thus appears as a terminal to the remote host.
[Source: MALAMUD]

terminal server
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.
[Source: MALAMUD]

TLA
See: Three Letter Acronym

TN3270
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
terminal.
[Source: BIG-LAN]

token ring
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.

topology
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.
[Source: MALAMUD]

traceroute
A program available on many systems which traces the path a packet
takes to a destination. It is mostly used to debug routing
problems between hosts. There is also a traceroute protocol
defined in RFC1393.

Trans-European Research and Education Networking Association (TERENA)
TERENA was formed in October 1994 by the merger of RARE and EARN
to promote and participate in the development of a high quality
international information and telecommunications infrastructure
for the benefit of research and education. See also: Reseaux
Associes pour la Recherche Europeenne, European Academic and
Research Network.
[Source: TERENA Statutes]

transceiver
Transmitter-receiver. The physical device that connects a host
interface to a local area network, such as Ethernet. Ethernet
transceivers contain electronics that apply signals to the cable
and sense collisions.
[Source: RFC1208]

transit network
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 RFC793.
It is connection-oriented and stream-oriented, as opposed to UDP.
See also: connection-oriented, stream-oriented, User Datagram
Protocol.

Trojan Horse
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.

TTFN
Ta-Ta For Now

TTL
See: Time to Live

tunnelling
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
connecting those domains. See also: Administrative Domain.

twisted pair
A type of cable in which pairs of conductors are twisted together
to produce certain electrical properties.

UDP
See: User Datagram Protocol

unicast
An address which only one host will recognize. See also:
broadcast, multicast.

Uniform Resource Locators (URL)
A URL is a compact (most of the time) string representation for a
resource available on the Internet. URLs are primarily used to
retrieve information using WWW. The syntax and semantics for URLs
are defined in RFC1738. See also: World Wide Web.

Universal Time Coordinated (UTC)
This is Greenwich Mean Time.
[Source: MALAMUD]

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
Mail, Usenet.

urban legend
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
Recipe."
[Source: LAQUEY]

URL
See: Uniform Resource Locators

Usenet
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.
[Source: NWNET]

User Datagram Protocol (UDP)
An Internet Standard transport layer protocol defined in RFC768.
It is a connectionless protocol which adds a level of reliability
and multiplexing to IP. See also: connectionless, Transmission
Control Protocol.

UTC
See: Universal Time Coordinated

UUCP
See: UNIX-to-UNIX CoPy

uudecode
A program which reverses the effect of uuencode. See also:
uuencode.

uuencode
A program which reversibly converts a binary file in ASCII. It is
used to send binary files via email, which generally does not
allow (or garbles) the transmission of binary information. The
original binary can be restored with uudecode. The encoding
process generally creates an ASCII file larger than the original
binary, so compressing the binary before running uuencode is
highly recommended.

Veronica
A Gopher utility which effectively searches Gopher servers based
on a user's list of keywords. The name was chosen to be a "mate"
to another utility named "Archie." It later became an acronym for
Very Easy Rodent Oriented Netwide Index to Computer Archives. See
also: archie, Gopher.

virtual circuit
A network service which provides connection-oriented service
without necessarily doing circuit-switching. See also:
connection-oriented.

virus
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.

W3
See: World Wide Web

WAIS
See: Wide Area Information Servers

WAN
See: Wide area network

WebCrawler
A WWW search engine. The aim of the WebCrawler Project is to
provide a high-quality, fast, and free Internet search service.
The WebCrawler may be reached at "http://webcrawler.com/".
[Source: WebCrawler's "WebCrawler Facts"]

WG
See: Working Group

white pages
The Internet supports several databases that contain basic
information about users, such as e-mail 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, netfind, whois,
X.500, InterNIC.

whois
An Internet program which allows users to query a database of
people and other Internet entities, such as domains, networks, and
hosts. The primary database is kept at the InterNIC. The

information stored includes a person's company name, address,
phone number and email address. The latest version of the
protocol, WHOIS++, is defined in RFCs 1834 and 1835. See also:
InterNIC, white pages, Knowbot, netfind, X.500.

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,
Prospero.

Wide Area Network (WAN)
A network, usually constructed with serial lines, which covers a
large geographic area. See also: Local Area Network, Metropolitan
Area Network.

Working Group (WG)
A working group, within the IETF, is a group of people who work
under a charter to achieve a certain goal. That goal may be the
creation of an Informational document, the creation of a protocol
specification, or the resolution of problems in the Internet.
Most working groups have a finite lifetime. That is, once a
working group has achieved its goal, it disbands. There is no
official membership for a working group. Unofficially, a working
group member is somebody who is on that working group's mailing
list; however, anyone may attend a working group meeting. See
also: Internet Engineering Task Force, Birds Of a Feather.

World Wide Web (WWW, 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
available.

worm
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.

WRT
With Respect To

WWW
See: World Wide Web

WYSIWYG
What You See is What You Get

X
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
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.

X.400
The CCITT and ISO standard for electronic mail. It is widely used
in Europe and Canada.

X.500
The CCITT and ISO standard for electronic directory services. See
also: white pages, Knowbot, whois.

XDR
See: eXternal Data Representation

Xerox Network System (XNS)
A protocol suite developed by Xerox Corporation to run on LAN and
WAN networks, where the LANs are typically Ethernet.
Implementations exist for both Xerox's workstations and 4.3BSD,
and 4.3BSD-derived, systems. XNS denotes not only the protocol
stack, but also an architecture of standard programming
interfaces, conventions, and service functions for authentication,
directory, filing, email, and remote procedure call. XNS is also
the name of Xerox's implementation. See also: Ethernet, Berkeley
Software Distribution, Local Area Network, Wide Area Network.
[Source: Jeff Hodges]

XNS
See: Xerox Network System

Yahoo!

Yahoo! is a hierarchical subject-oriented guide for the World Wide
Web and Internet. Yahoo! lists sites and categorizes them into
appropriate subject categories. Yahoo! may be reached at
"http://www.yahoo.com/".
[Source: Yahoo's "What is Yahoo?"]

Yellow Pages (YP)
A historic (i.e., no longer in use) service used by UNIX
administrators to manage databases distributed across a network.

YP
See: Yellow Pages

zone
A logical group of network devices.

References

BIG-LAN "BIG-LAN Frequently Asked Questions Memo", BIG-LAN DIGEST
V4:I8, February 14, 1992.

COMER Comer, Douglas, "Internetworking with TCP/IP: Principles,
Protocols and Architecture", Prentice Hall, Englewood Cliffs,
NJ, 1991.

FYI4 Malkin, G., A. Marine, "FYI on Questions and Answers: Answers
to Commonly asked "New Internet User" Questions", RFC1325
(FYI 4), 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, Carl, "Analyzing Sun Networks", Van Nostrand
Reinhold, New York, NY, 1992.

NNSC "NNSC's Hypercard Tour of the Internet".

LAQUEY LaQuey, Tracy, with Jeanne C. Ryer, "The Internet Companion:
A Beginner's Guide to Global Networking", Addison-Wesley,
Reading, MA, 1992.

NWNET Kochmer, Jonathan, and NorthWestNet, "The Internet Passport:
NorthWestNets Guide to Our World Online", NorthWestNet,
Bellevue, WA, 1992.

RFC1208 Jacobsen, O., D. Lynch, "A Glossary of Networking Terms", RFC
1208, Interop, Inc., March 1991.

STD1 Postel, J., "INTERNET OFFICIAL PROTOCOL STANDARDS", RFC1920
(STD 1), March 1996.

STD2 Reynolds, J., J. Postel, "ASSIGNED NUMBERS", RFC1700 (STD
2), ISI, October 1994.

TAN Tanenbaum, Andrew S., "Computer Networks; 2nd ed.", Prentice
Hall, Englewood Cliffs, NJ, 1989.

ZEN Kehoe, Brendan P., "Zen and the Art of the Internet",
February 1992.

Security Considerations

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, Message Digest (MD-
2, MD-4, MD-5), Pretty Good Privacy (PGP), Privacy Enhanced Mail
(PEM), RSA, Trojan Horse, virus, and worm.

Editor's Address

Gary Scott Malkin
Xylogics/Bay Networks
53 Third Avenue
Burlington, MA 01803

Phone: (617) 238-6237
EMail: gmalkin@Xylogics.COM