Listed below is a glossary of networking terms, taken from a variety of sources, including the "Internet User's Glossary"(IETF, RFC1392, 1/93), "Glossary of Networking Terms"(IETF, RFC1208, 3/91), and the "Interop '96 Pocket Glossary of Networking Terms (3/96).
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
10Base-T: A variant of Ethernet (IEEE 802.3) which allows stations to be
attached via twisted pair ("telephone") cable. See Ethernet, twisted
pair, 802.x.
802.x: The set of IEEE standards for the definition of LAN protocols.
A
abstract syntax: A description of a data structure that is
independent of machine-oriented structures and encodings. See transfer
syntax.
ACSE: Association Control Service Element. The method used in OSI
for establishing a call between two applications. Checks the
identities and contexts of the application entities, and could apply
an authentication security check.
ACK: Acknowledgement. A type of message sent to indicate that a block
of data arrived at its destination without error. A negative acknowledgement
is called a "NAK."
address mask: A bit mask used to select bits from an Internet address
for subnet addressing. The mask is 32 bits long and selects the
network portion of the Internet address and one or more bits of the
local portion. Sometimes called subnet mask.
address resolution: A means for mapping Network Layer addresses onto
media-specific addresses. See ARP.
ADMD: Administration Management Domain. An X.400 Message Handling
System public carrier. Examples: MCImail and ATTmail in the
U.S., British Telecom Gold400mail in the U.K. The ADMDs in all
countries worldwide together provide the X.400 backbone. See PRMD.
ADDMD: Administrative Directory Management Domain. A Directory (X.500)
management domain run by a PIT authority.
Administrative Domain (AD): A group of hosts, routers, and networks
operated and managed by a single organization.
AET: Application Entity Title. The authoritative name of an OSI
application entity, usually a Distinguished Name from the Directory. See DN.
AFP: AppleTalk Filing Protocol. Protocol that allows distributed file
sharing across an AppleTalk network.
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. In SNMP, the word agent refers to the managed
system. See NMS, DUA, MTA.
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, FTP.
ANSI: American National Standards Institute. The U.S.
standardization body. ANSI is a member of the International
Organization for Standardization (ISO)
AOW: Asia and Oceania Workshop. One of the three regional OSI
Implementors Workshops, equivalent to OIW and EWOS.
API: Application Program Interface. A set of calling conventions
defining how a service is invoked through a software package.
APPC: Advanced Program-to-Program Communications. Part of IBM's Systems
Network Architecture (SNA).
Appletalk: A networking protocol developed by Apple Computer for
communication between Apple Computer products and other computers. This
protocol is independent of what network it is layered on. Current
implementations exist for LocalTalk (235Kbps) and EtherTalk(10Mbps).
Application Layer: The top-most layer in the OSI Reference Model
providing such communication services as electronic mail and file
transfer.
archive site: A machine that provides access to a collection of files
across the Internet. An "anonymous FTP archive site", for example, provides
access to this material via the FTP protocol. See also: anonymous
FTP, archie, Gopher, Prospero, WAIS.
ARNS: "A Remote Network Server," software which encapsulates AppleTalk
packets inside IP packets, so that the AppleTalk data can be sent over
IP networks.
ARP: Address Resolution Protocol. The Internet protocol used to
dynamically map Internet addresses to physical (hardware) addresses
on local area networks. Limited to networks that support hardware
broadcast.
Archie: A system which provides lists of anonymous FTP archives. Archie
is one of the many "neat new applications" on the Internet. See Gopher,
Prospero, WAIS, and World-Wide Web (WWW).
ARP: Address Resolution Protocol. The Internet protocol used to
dynamically map Internet addresses to physical (hardware) addresses on
local area networks. Limited to networks that support hardware broadcast.
See RARP.
ARPA: Advanced Research Projects Agency. Now called DARPA, the U.S.
government agency that funded the ARPANET.
ARPANET: A packet switched network developed in the early 1970s. The
"grandfather" of today's Internet. ARPANET was decommissioned in
June 1990.
ASCII: American Standard Code for Information Interchange. A standard
character-to-number encoding widely used in the computer industry.
See also: EBCDIC.
ASN.1: Abstract Syntax Notation One. The OSI language for describing
abstract syntax. See BER.
ATM: Asynchronous Transfer Mode. The SONET standard for a packet switching
technique which uses packets (cells) of fixed length. Also referred to as
BISDN and Cell Relay.
attribute: The form of information items provided by the X.500
Directory Service. The directory information base consists of
entries, each containing one or more attributes. Each attribute
consists of a type identifier together with one or more values. Each
directory Read operation can retrieve some or all attributes from a
designated entry.
Autonomous System: Internet (TCP/IP) terminology for a collection of
gateways (routers) that fall under one administrative entity and
cooperate using a common Interior Gateway Protocol (IGP). See
subnetwork.
B
backbone: The primary connectivity mechanism of a hierarchical
distributed system. All systems which have connectivity to an
intermediate system on the backbone are assured of connectivity to
each other. This does not prevent systems from setting up private
arrangements with each other to bypass the backbone for reasons of
cost, performance, or security. See core gateway.
baseband: Characteristic of any network technology that uses a single
carrier frequency and requires all stations attached to the network
to participate in every transmission. See broadband.
BER: Basic Encoding Rules. Standard rules for encoding data units
described in ASN.1. Sometimes incorrectly lumped under the term
ASN.1, which properly refers only to the abstract syntax description
language, not the encoding technique.
big-endian: A format for storage or transmission of binary data in
which the most significant bit (or byte) comes first. The reverse
convention is called little-endian.
BIND: Berkeley Internet Name Domain. Implementation of a DNS server
originally developed and distributed by UC Berkeley. Many Internet
hosts run BIND, and it is the ancestor of many commerical BIND
implementations.
BISDN: Broadband Integrated Services Digital Networks. See ATM.
BITNET: Because It's Time NETwork. An academic computer network
based originally on IBM mainframe systems interconnected via leased
9600 bps lines. BITNET has recently merged with CSNET, The
Computer+Science Network (another academic computer network) to form
CREN: The Corporation for Research and Educational Networking. See
CSNET.
BOC: Bell Operating Company. More commonly referred to as RBOC for
Regional Bell Operating Company. The local telephone company in each
of the seven U.S. regions.
BOOTP: Boot Protocol. Allows an internet node to discover certain
startup information such as its IP address.
bridge: A device that connects two or more physical networks and
forwards packets between them. Bridges can usually be made to filter
packets, that is, to forward only certain traffic. Related devices
are: repeaters which simply forward electrical signals from one cable
to another, and full-fledged routers which make routing decisions
based on several criteria. In OSI terminology, a bridge is the Data
Link Layer. See repeater, router, and intermediate system.
broadband: Characteristic of any network that multiplexes multiple,
independent network carriers onto a single cable. This is usually
done using frequency division multiplexing. Broadband technology
allows several networks to coexist on one single cable; traffic from
one network does not interfere with traffic from another since the
"conversations" happen on different frequencies in the "ether,"
rather like the commercial radio system. See baseband.
broadcast: A packet delivery system where a copy of a given packet is given
to all hosts attached to the network. Example: Ethernet. See multicast.
broadcast storm: A condition that can occur on broadcast type networks
such as Ethernet. This can happen for a number of reasons ranging from
hardware malfunction to configuration errors and bandwidth saturation.
brouter: Concatenation of "bridge" and "router." Used to refer to devices
which perform both bridging and routing functions.
browser: Term used to describe the client program for the World-Wide Web.
Popular browers include Mosaic and Netscape. Sometimes called 'navigator.'
BSD: Berkeley Software Distribution. Term used when describing
different versions of the Berkeley UNIX software, as in "4.3BSD
UNIX."
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.
C
caching: A form of replication in which information learned during a
previous transaction is used to process later transactions.
catenet: A network in which hosts are connected to networks with
varying characteristics, and the networks are interconnected by
gateways (routers). The Internet is an example of a catenet. See
IONL.
CATNIP: Common Architecture for Next Generation Internet Protocol. One
of the 3 IPng candidates. See IPng.
CCITT: International Consultative Committee for Telegraphy and
Telephony. A unit of the International Telecommunications Union
(ITU) of the United Nations. An organization with representatives
from the PTTs of the world. CCITT produces technical standards,
known as "Recommendations," for all internationally controlled
aspects of analog and digital communications. See X Recommendations, OSI.
CCR: Commitment, Concurrency, and Recovery. An OSI application
service element used to create atomic operations across distributed
systems. Used primarily to implement two-phase commit for
transactions and nonstop operations.
Cell Relay: See ATM.
CERN: European Laboratory for Particle Physics. Birthplace of the
World-Wide Web.
CERT: Computer Emergency Response Team. The CERT is chartered to work
with the Internet community to facilitate its reponse to computer
security events involving Internet hosts and raise security awareness.
Charlie-Foxtrot: (colloquial usage) seriously beyond all hope. Very
badly broken.
CIDR: Classless Inter-Domain Routing. A method for using the existing
32-bit Internet Address Space more efficiently.
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.
CIX: Commercial Internet Exchange. A connection point between the
commercial Internet service providers. Pronounced "kicks." See FIX and GIX.
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.
client-server model: A common way to describe network services and the
model user processes (programs) of those services. Examples include
the nameserver/nameresolver paradigm of the DNS and fileserver/
file-client relationships such as NFS and diskless hosts.
CLNP: Connectionless Network Protocol. The OSI protocol for
providing the OSI Connectionless Network Service (datagram service).
CLNP is the OSI equivalent to Internet IP, and is sometimes called
ISO IP.
CLTP: Connectionless Transport Protocol. Provides for end-to-end
Transport data addressing (via Transport selector) and error control
(via checksum), but cannot guarantee delivery or provide flow
control. The OSI equivalent of UDP.
CMIP: Common Management Information Protocol. The OSI network
management protocol.
CMOT: CMIP Over TCP. An effort to use the OSI network management
protocol to manage TCP/IP networks. CMOT is historical, not implemented.
connectionless: The model of interconnection in which communication
takes place without first establishing a connection. Sometimes
(imprecisely) called datagram. Examples: Internet IP and OSI
CLNP, UDP, ordinary postcards.
connection-oriented: The model of interconnection in which
communication proceeds through three well-defined phases: connection
establishment, data transfer, connection release. Examples: X.25,
Internet TCP and OSI TP4, ordinary telephone calls.
CONS: Connection Oriented Network Service.
core gateway: Historically, one of a set of gateways (routers)
operated by the Internet Network Operations Center at BBN. The core
gateway system forms a central part of Internet routing in that all
groups must advertise paths to their networks from a core gateway,
using the Exterior Gateway Protocol (EGP). See EGP, backbone.
COS: Corporation for Open Systems. A vendor and user group for
conformance testing, certification, and promotion of OSI products.
COSINE: Cooperation for Open Systems Interconnection Networking in
Europe. A program sponsored by the European Commission, aimed at
using OSI to tie together European research networks.
CREN: See BITNET and CSNET.
CSMA/CD: Carrier Sense Multiple Access with Collision Detection. The
access method used by local area networking technologies such as
Ethernet.
CSNET: Computer+Science Network. A large computer network, mostly in
the U.S. but with international connections. CSNET sites include
universities, research labs, and some commercial companies. Now
merged with BITNET to form CREN. See BITNET.
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. Often used to refer to the Internet or the World-Wide Web.
D
DARPA: Defense Advanced Research Projects Agency. The U.S.
government agency that funded the ARPANET.
DAP: Directory Access Protocol. The protocol used between a Directory
User Agent (DUA) and a Directory System Agent (DSA) in an X.500 directory
system.
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 frame, packet.
Data Link Layer: The OSI layer that is responsible for data transfer
across a single physical connection, or series of bridged
connections, between two Network entities.
DCA: Defense Communications Agency. The government agency
responsible for the Defense Data Network (DDN).
DCE: Distributed Computing Environment. An architecture of standard
programming interfaces, conventions, and server functionalities
(e.g., naming, distributed file system, remote procedure call) for
distributing applications transparently across networks of
heterogeneous computers. Promoted and controlled by the Open
Software Foundation (OSF), a vendor consortium. See ONC.
DDN: Defense Data Network. Comprises the MILNET and several other
DoD networks.
DECnet: Digital Equipment Corporation's proprietary network
architecture.
default route: A routing table entry which is used to direct packets
addressed to networks not explicitly listed in the routing table.
DES: Data Encryption Standard. A popular, standard encryption scheme. See PGP.
DISA: Defense Information Systems Agency. The new name for DCA. See DCA.
DIT: Directory Information Tree. The global tree of entries corresponding
to information objects in the OSI X.500 Directory.
DN: Distinguished Name. The global, authoritative name of an entry in the
OSI Directory (X.500).
DNS: Domain Name System. The distributed name/address mechanism used
in the Internet.
domain: In the Internet, a part of a naming hierarchy.
Syntactically, an Internet domain name consists of a sequence of
names (labels) separated by periods (dots), e.g., "tundra.mpk.ca.us."
In OSI, "domain" is generally used as an administrative partition of
a complex distributed system, as in MHS Private Management Domain
(PRMD), and Directory Management Domain (DMD).
dotted decimal notation: The syntactic representation for a 32-bit
integer that consists of four 8-bit numbers written in base 10 with
periods (dots) separating them. Used to represent IP addresses in
the Internet as in: 192.67.67.20. Also called "dotted quad notation."
DSA: Directory System Agent. The software that provides the X.500
Directory Service for a portion of the directory information base.
Generally, each DSA is responsible for the directory information for
a single organization or organizational unit.
DUA: Directory User Agent. The software that accesses the X.500
Directory Service on behalf of the directory user. The directory
user may be a person or another software element.
E
EARN: European Academic Research Network. A network using BITNET
technology connecting universities and research labs in Europe.
EBONE: European Backbone. A pan-European network backbone service.
ECMA: European Computer Manufacturers Association. A group of computer
vendors that have performed substantive prestandardization work for OSI.
EGP: Exterior Gateway Protocol. A reachability routing protocol used
by gateways in a two-level internet. EGP is used in the Internet
core system. See core gateway.
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 the 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.
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".
encapsulation: The technique used by layered protocols in which a
layer adds header information to the protocol data unit (PDU) from
the layer above. As an example, in Internet terminology, a packet
would contain a header from the physical layer, followed by a header
from the network layer (IP), followed by a header from the transport
layer (TCP), followed by the application protocol data.
encryption: 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.
end system: An OSI system which contains application processes
capable of communicating through all seven layers of OSI protocols.
Equivalent to Internet host.
entity: OSI terminology for a layer protocol machine. An entity
within a layer performs the functions of the layer within a single
computer system, accessing the layer entity below and providing
services to the layer entity above at local service access points.
ES-IS: End system to Intermediate system protocol. The OSI protocol
used for router detection and address resolution.
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.
EUnet: European UNIX Network.(Original name). Now a major European
Internet Service provider.
EUUG: European UNIX Users Group. Now called EurOpen.
EWOS: European Workshop for Open Systems. The OSI Implementors
Workshop for Europe. See OIW.
F
FARNET: Federation of American Research NETworks.
FDDI: Fiber Distributed Data Interface. An emerging high-speed
networking standard. The underlying medium is fiber optics, and the
topology is a dual-attached, counter-rotating Token Ring. FDDI
networks can often be spotted by the orange fiber "cable." The FDDI
protocol has also been adapted to run over traditional copper wires.
finger: a program that displays information about a particular user, or
all users, logged on the local system or on a remote system. It
typically shows full name, last login time, idle time, terminal
line, and terminal location (where applicable). It may also
display plan and project files left by the user.
FIPS: Federal Information Processing Standard.
FIX: Federal Internet Exchange. A connection point between the North
American governmental internets and the Internet. The FIXs are named after
their geographic region, as in "FIX West" (Mountain View, California) and
"FIX East" (College Park, Maryland). See CIX and GIX.
flame: To express strong opinion and/or criticism of something,
usually as a frank inflammatory statement in an electronic message.
FNC: Federal Networking Council. The body responsible for
coordinating networking needs among U.S. Federal agencies.
fragmentation: The IP process in which a packet is broken into
smaller pieces to fit the requirements of a given physical network.
The reverse process is termed reassembly. See MTU.
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: IP datagram, encapsulation, packet.
Frame Relay: A recently developed switching interface which operates in
packet mode. Generally regarded as the future replacement for X.25.
FRICC: Federal Research Internet Coordinating Committee. Now
replaced by the FNC.
FTAM: File Transfer, Access, and Management. The OSI remote file
service and protocol.
FTP: File Transfer Protocol. The Internet protocol (and program)
used to transfer files between hosts. See FTAM.
G
gateway: The original Internet term for what is now called router or
more precisely, IP router. In modern usage, the terms "gateway" and
"application gateway" refer to systems which do translation from some
native format to another. Examples include X.400 to/from RFC 822
electronic mail gateways. See router.
GateD: Gateway Daemon. A popular routing software package which supports
multiple routing protocols. Developed and maintained by the GateDaemon
Consortium at Cornell University.
GIX: Global Internet eXchange. A common routing exchange point which
allows pairs of networks to implement agreed-upon routing policies.
The GIX is intended to allow maximum connectivity to the Internet for
networks all over the world. See CIX and FIX.
GOSIP: Government OSI Profile. A U.S. Government procurement
specification for OSI protocols. There is talk about having TCP/IP be
part of GOSIP too.
Gopher: The Internet Gopher is a distributed document delivery system. It
allows a neophyte user to access various types of data residing on
multiple hosts in a seamless fashion. See archie, Prospero, WAIS and
World-Wide Web.
H
header: The portion of a packet, preceding the actual data, containing
source and destination addresses and error-checking fields. The word can
also be used to describe the part of an electronic mail message (or USENET
news article) that precedes the body, although one usually talks about
headers (plural) in theat case.
hop: A term used in routing. A hop is one data link. A path from source
to destination in a network is a series of hops. Often used to measure
the number of routers that a packet must traverse. "BARRnet is seven hops
away from our LAN."
host: The term used in the Internet community to describe any device
attached to the network which provides application level service (i.e.,
a machine that you can log in to and do useful work). A router is not
a host.
HTML (Hyper Text Markup Language): The language used in the World-Wide
Web to create web pages with links to other documents, rich text
enhancements (bold, italic, etc.) and so on. The 'source' file for what
you see on a web page is written in HTML.
HTTP (Hyper Text Transport Protocol): The protocol for moving hypertext
files across the Internet. Requires a HTTP client program on one end,
and an HTTP server program on the other end. HTTP is the most
important protocol used in the World Wide Web (WWW). See URL.
hypertext: Generally, any text that contains "links" to other documents -
words or phrases in the document that can be chosen by a reader and
which cause another document to be retrieved and displayed. See HTML.
I
IAB: Internet Architecture Board. Formerly called the Internet Activities
Board. The technical body that oversees the development of the
Internet suite of protocols (commonly referred to as "TCP/IP"). It has
two task forces (the IRTF and the IETF) each charged with investigating
a particular area.
IANA: Internet Assigned Numbers Authority. The entity responsible for
assigning numbers in the Internet Suite of Protocols.
ICMP: Internet Control Message Protocol. The protocol used to handle
errors and control messages at the IP layer. ICMP is actually part
of the IP protocol.
IEEE: Institute of Electrical and Electronics Engineers
IESG: Internet Engineering Steering Group. The executive committee
of the IETF.
IETF: Internet Engineering Task Force. One of the task forces of the
IAB. The IETF is responsible for solving short-term engineering
needs of the Internet. It has over 60 Working Groups.
IFIP: International Federation for Information Procession. A research
organization that performs substantive pre-standardization work for OSI.
IFIP is noted for having formalized the original Message Handling System
(MHS) model.
IGP: Interior Gateway Protocol. The protocol used to exchange
routing information between collaborating routers in the Internet.
RIP and OSPF are examples of IGPs.
IGRP: Internet Gateway Routing Protocol. A proprietary IGP used by
Cisco System's routers.
INTAP: Interoperability Technology Association for Information
Processing. The technical organization which has the official
charter to develop Japanese OSI profiles and conformance tests.
intermediate system: An OSI system which is not an end system, but
which serves instead to relay communications between end systems.
See repeater, bridge, and router.
internet: A collection of networks interconnected by a set of routers
which allow them to function as a single, large virtual network.
Internet: (note the capital "I") The largest internet in the world
consisting of large national backbone nets (such as MILNET, NSFNET,
and CREN) and a myriad of regional and local campus networks all over
the world. The Internet uses the Internet protocol suite. To be on
the Internet you must have IP connectivity, i.e., be able to Telnet
to--or ping--other systems. Networks with only e-mail connectivity
are not actually classified as being on the Internet.
Internet address: A 32-bit address assigned to hosts using TCP/IP.
See dotted decimal notation.
cisco System's routers.
Internet Society (ISOC): A non-profit organization that fosters the
voluntary interconnection of computer networks into a global communications
and information infrastructure. The ISOC is the umbrella organization
for the IAB, IETF, and IRTF.
interoperability: The ability of software and hardware on multiple machines
from multiple vendors to communicate meaningfully.
IONL: Internal Organization of the Network Layer. The OSI standard
for the detailed architecture of the Network Layer. Basically, it
partitions the Network layer into subnetworks interconnected by
convergence protocols (equivalent to internetworking protocols),
creating what Internet calls a catenet or internet.
IP: Internet Protocol. The network layer protocol for the Internet
protocol suite.
IP datagram: The fundamental unit of information passed across the
Internet. Contains source and destination addresses along with data
and a number of fields which define such things as the length of the
datagram, the header checksum, and flags to say whether the datagram
can be (or has been) fragmented.
IPng: IP Next Generation. Collective term used to describe the efforts
of the Internet Engineering Task force to define a new version of the
Internet Protocol (IP) which can handle larger IP addresses to cope with
the explosive growth of the Internet. Also known as IPv6. See IPv6.
IPv6: IP Version Six. Also known as IPng.
IPX: Internetwork Packet Exchange. The Novell NetWare protocol that
provides datagram delivery of messages. A router with IPX routing can
interconnect LANs so that Novell Netware clients and servers can
communicate. See also: Local Area Network.
IRTF: Internet Research Task Force. One of the task forces of the
IAB. The group responsible for research and development of the
Internet protocol suite.
ISDN: Integrated Services Digital Network. An emerging technology
which is beginning to be offered by the telephone carriers of the
world. ISDN combines voice and digital network services in a single
medium making it possible to offer customers digital data services as
well as voice connections through a single "wire." The standards
that define ISDN are specified by CCITT.
IS-IS: Intermediate system to Intermediate system protocol. The OSI
protocol by which intermediate systems exchange routing information.
ISO: International Organization for Standardization. You knew that,
right? Best known for the 7-layer OSI Reference Model. See OSI.
ISODE: ISO Development Environment. A popular implementation of the
upper layers of OSI. Pronounced eye-so-dee-eee.
ISP: Internet Service Provider. Any of a number of companies that sell
Internet access to individuals or organizations at speeds ranging from
300bps to OC-3.
J
JANET: Joint Academic Network. A university network in the U.K. In recent
years, renamed to "Super-JANET."
JUNET: Japan UNIX Network.
K
KA9Q: A popular implementation of TCP/IP and associated protocols for
amateur packet radio systems.
Kerberos: The security system of MIT's Project Athena. It is
based on symmetric key cryptography. See also: encryption.
Kermit: A popular file transfer and terminal emulation program.
Knowbot: An experimental directory service. See also: white pages, WHOIS,
X.500.
L
LATA: Local Access and Transport Area. A telephone company term that
defines a geographical area. (Normally, but not always, corresponds to
an area code.)
listserv: An automated mailing list distribution system originally
designed for the Bitnet/EARN network. Listserv allows users to add or
delete themselves from mailing lists without (other) human intervention.
little-endian: A format for storage or transmission of binary data in
which the least significant byte (bit) comes first. See big-endian.
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, FDDI, token ring.
LocalTalk: A local area network (LAN) protocol developed by Apple Computer.
This network is designed to run over twisted pair wire and has a data
rate of 235Kbps. All Macintosh computers contain a LocalTalk interface.
See AppleTalk.
M
mail exploder: Part of an electronic mail delivery system which
allows a message to be delivered to a list of addressees. Mail
exploders are used to implement mailing lists. Users send messages
to a single address (e.g., hacks@somehost.edu) and the mail exploder
takes care of delivery to the individual mailboxes in the list.
mail gateway: A machine that connects two or more electronic mail
systems (especially dissimilar mail systems on two different
networks) and transfers messages between them. Sometimes the mapping
and translation can be quite complex, and generally it requires a
store-and-forward scheme whereby the message is received from one
system completely before it is transmitted to the next system after
suitable translations.
Martian: Humorous term applied to packets that turn up unexpectedly
on the wrong network because of bogus routing entries. Also used as
a name for a packet which has an altogether bogus (non-registered or
ill-formed) Internet address.
MAP: Manufacturing Automation Protocol. A protocol stack developed by
General Motors following the OSI model that guarantees access to each
host within a certain maximum time. At the upper layers, it includes
many of the OSI standards. At the lower layers, it is based on Token
Bus (IEEE 802.4). See TOP.
MBONE: Multicast Backbone. A collection of Internet routers that support
IP multicasting. The MBONE is used as a "broadcast (actually multicast)
channel" on which various public and private audio and video programs are
sent. Examples include audio/video transmissions from the IETF meetings.
At a recent IETF meeting there were as many participants "listening in"
on the MBONE as there were people present at the meeting itself.
MHS: Message Handling System. The system of message user agents,
message transfer agents, message stores, and access units which
together provide OSI electronic mail. MHS is specified in the CCITT
X.400 series of Recommendations.
MIB: Management Information Base. A collection of objects that can
be accessed via a network management protocol. See SMI.
MILNET: MILitary NETwork. Originally part of the ARPANET, MILNET was
partitioned in 1984 to make it possible for military installations to
have reliable network service, while the ARPANET continued to be used
for research. See DDN.
MIME: Multi-purpose Internet Mail Extensions. The standard for multimedia
mail contents in the Internet suite of protocols.
modem: (MOdulator, DEModulator): a device that you connect to your
computer and to a phone line, that allows the computer to talk to
other computers through the phone system. Basically, modems do for
computers what a telephone does for humans.
MTA: Message Transfer Agent. An OSI application process used to
store and forward messages in the X.400 Message Handling System.
Equivalent to Internet mail agent.
MTU: Maximum Transmission Unit. The largest possible unit of data
that can be sent on a given physical medium. Example: The MTU of
Ethernet is 1500 bytes. See fragmentation.
multicast: A special form of broadcast where copies of the packet are
delivered to only a subset of all possible destinations. See
broadcast, MBONE.
multi-homed host: A computer connected to more than one physical data
link. The data links may or may not be attached to the same network.
N
NAK: Negative Acknowledgement. See ACK.
NADF: North American Directory Forum. A collection of organizations
which offer, or plan to offer, public Directory Services in North America,
based on the CCITT X.500 Recommendations.
name resolution: The process of mapping a name into the corresponding
address. See DNS.
NetBIOS: Network Basic Input Output System. The standard interface
to networks on IBM PC and compatible systems.
network: Any time you connected 2 or more computers together so that
they can share resources you have a computer network. Connect 2
or more networks together and you have an internet.
Network Address: See Internet address or OSI Network Address.
network byte order: The Internet-standard ordering of the bytes
corresponding to numberic values.
Network Layer: The OSI layer that is responsible for routing,
switching, and subnetwork access across the entire OSI environment.
Network File System (NFS)(r): A distributed file system developed by
Sun Microsystems which allows a set of computers to cooperatively
access each other's files in a transparent manner. See RFS.
Network Time Protocol (NTP): A protocol built on top of TCP that assures
accurate local time-keeping 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.
NIC: Network Information Center. Originally there was only one,
located at SRI International and tasked to serve the ARPANET (and
later DDN) community. Today, there are many NICs, operated by local,
regional, and national networks all over the world. Such centers
provide user assistance, document service, training, and much more.
NIST: National Institute of Standards and Technology. (Formerly
NBS). See OIW.
NMS: Network Management Station. The system responsible for managing
a (portion of a) network. The NMS talks to network management
agents, which reside in the managed nodes, via a network management
protocol. See agent.
NOC: Network Operations Center. Any center tasked with the
operational aspects of a production network. These tasks include
monitoring and control, trouble-shooting, user assistance, and so on.
node: Any single computer connected to a network.
NREN: National Research and Educational Network. This network is still on
the "drawing board." It is expected to become a state of the art high-
speed network for research and education in the U.S. In recent years the
NREN has become synonymous with the National Information Infrastructure,
often referred to as the Information Superhighway.
NSAP: Network Service Access Point. The point at which the OSI
Network Service is made available to a Transport entity. The NSAPs
are identified by OSI Network Addresses.
NSF: National Science Foundation. Sponsors of the NSFNET.
NSFNET: National Science Foundation NETwork. A collection of local,
regional, and mid-level networks in the U.S. tied together by a
high-speed backbone. NSFNET provides scientists access to a number
of supercomputers across the country.
O
octet: An octet is eight (8) bits. In networking the term "octet" is often
used (rather than "byte") since some machine architectures employ bytes
which are not 8 bits long.
OIW: Workshop for Implementors of OSI. Frequently called NIST OIW or
the NIST Workshop, this is the North American regional forum at which
OSI implementation agreements are decided. It is equivalent to EWOS
in Europe and AOW in the Pacific.
ONC(tm): Open Network Computing. A distributed applications
architecture promoted and controlled by a consortium led by Sun
Microsystems. See DCE.
OSI: Open Systems Interconnection. An international standardization
program to facilitate communications among computers from different
manufacturers. See ISO and CCITT.
OSI Network Address: The address, consisting of up to 20 octets, used
to locate an OSI Transport entity. The address is formatted into an
Initial Domain Part which is standardized for each of several
addressing domains, and a Domain Specific Part which is the
responsibility of the addressing authority for that domain.
OSI Presentation Address: The address used to locate an OSI
Application entity. It consists of an OSI Network Address and up to
three selectors, one each for use by the Transport, Session, and
Presentation entities.
OSF: Open Software Foundation. The group responsible for the Distributed
Computing Environment (DCE) and the Distributed Management Environment
(DME). See DCE.
OSPF: Open Shortest Path First. A "Proposed Standard" IGP for the
Internet. See IGP.
P
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: IP datagram, frame.
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.
PCI: Protocol Control Information. The protocol information added by
an OSI entity to the service data unit passed down from the layer
above, all together forming a Protocol Data Unit (PDU).
PDU: Protocol Data Unit. This is OSI terminology for "packet." A
PDU is a data object exchanged by protocol machines (entities) within
a given layer. PDUs consist of both Protocol Control Information
(PCI) and user data.
PGP: Pretty Good Privacy. PGP provides confidentiality and authentication
services for electronic mail and file storage applications. Distributed
for free on the Internet. See DES.
Physical Layer: The OSI layer that provides the means to activate and
use physical connections for bit transmission. In plain terms, the
Physical Layer provides the procedures for transferring a single bit
across a Physical Media.
Physical Media: Any means in the physical world for transferring
signals between OSI systems. Considered to be outside the OSI Model,
and therefore sometimes referred to as "Layer 0." The physical
connector to the media can be considered as defining the bottom
interface of the Physical Layer, i.e., the bottom of the OSI
Reference Model.
ping: Packet internet groper. A program used to test reachability of
destinations by sending them an ICMP echo request and waiting for a
reply. The term is used as a verb: "Ping host X to see if it is up!"
Point Of Presence (POP): A site where there exists a collection of
telecommunications equipment, usually digital leased lines and multi-protocol
routers.
port: The identifier (16-bit unsigned integer) used by Internet transport
protocols to distinguish among multiple simultaneous connections
to a single destination host. See selector.
POSI: Promoting Conference for OSI. Consists of executives from the six
major Japanese computer manufacturers and Nippon Telephone and Telegraph.
They set policies and commit resources to promote OSI.
Post Office Protocol (POP): A protocol designed to allow single user
hosts to read mail from a server. There are three versions: POP, POP2,
and POP3. Latter versions are NOT compatible with earlier versions.
See also: Electronic Mail.
PPP: Point-to-Point Protocol. The successor to SLIP, PPP provides
router-to-router and host-to-network connections over both
synchronous and asynchronous circuits. See SLIP.
Presentation Address: See OSI Presentation Address.
Presentation Layer: The OSI layer that determines how Application
information is represented (i.e., encoded) while in transit between
two end systems.
PRMD: Private Management Domain. An X.400 Message Handling System
private organization mail system. Example: NASAmail. See ADMD.
Prospero: A distributed directory service and file system that allows
users to construct customized views of available resources while taking
advantage of the structure imposed by others. See Gopher, WAIS, and
World-Wide Web.
protocol: A formal description of messages to be exchanged and rules
to be followed for two or more systems to exchange information.
protocol converter: A device/program which translates between different
protocols which serve similar functions (e.g., TCP and TP4).
proxy: The mechanism whereby one system "fronts for" another system
in responding to protocol requests. Proxy systems are used in
network management to avoid having to implement full protocol stacks
in simple devices, such as modems.
proxy ARP: The technique in which one machine, usually a router,
answers ARP requests intended for another machine. By "faking" its
identity, the router accepts responsibility for routing packets to
the "real" destination. Proxy ARP allows a site to use a single IP
address with two physical networks. Subnetting would normally be a
better solution.
PSN: Packet Switch Node. The modern term used for nodes in the
ARPANET and MILNET. These used to be called IMPs (Interface Message
Processors). PSNs are currently implemented with BBN C30 or C300
minicomputers.
Q
queue: A backup of packets awaiting processing.
QUIPU: A pioneering software package developed to study the OSI Directory
and provide extensive pilot capabilities.
R
RARE: Reseaux Associes pour la Recherche Europeenne. European
association of research networks.
RARP: Reverse Address Resolution Protocol. The Internet protocol a
diskless host uses to find its Internet address at startup. RARP
maps a physical (hardware) address to an Internet address. See ARP.
RBOC: Regional Bell Operating Company. See BOC.
reassembly: The process by which an IP datagram is "put back together" at
the receiving host after having been fragmented in transit. See
fragmentation and MTV.
repeater: A device which propagates electrical signals from one cable
to another without making routing decisions or providing packet
filtering. In OSI terminology, a repeater is a Physical Layer
intermediate system. See bridge, intermediate system, gateway, router.
replication: The process of keeping a copy of data, either through
shadowing or caching. See caching, shadowing.
RFC: Request For Comments. The document series, begun in 1969, which
describes the Internet suite of protocols and related experiments.
Not all (in fact very few) RFCs describe Internet standards, but all
Internet standards are written up as RFCs. This glossary is based
on RFC1209.
RFS: Remote File System. A distributed file system, similar to NFS,
developed by AT&T and distributed with their UNIX System V operating
system. See NFS.
RIP: Routing Information Protocol. An Interior Gateway Protocol
(IGP) supplied with Berkeley UNIX.
RIPE: Reseaux IP Europeens, a group formed to coordinate and promote
TCP/IP-based networks in Europe. RIPE holds periodic conferences to
coordinate technical issues (similar to the IETF) as well as running
a Network Control Center (NCC) to handle operational issues such as the
administration of the European domain name and routing tables.
rlogin: A service offered by Berkeley UNIX which allows users of one
machine to log into other UNIX systems (for which they are
authorized) and interact as if their terminals were connected
directly. Similar to Telnet.
ROSE: Remote Operations Service Element. An OSI RPC mechanism
used in OSI Message Handling, Directory, and Network Management
application protocols.
routed: Route Daemon. A program that runs under 4.2 or 4.3BSD UNIX
systems (and derived operating systems) to propagate routes among machines
on a local area network. Pronounced "route-dee."
router: A system responsible for making decisions about which of
several paths network (or Internet) traffic will follow. To do this
it uses a routing protocol to gain information about the network, and
algorithms to choose the best route based on several criteria known
as "routing metrics." In OSI terminology, a router is a Network
Layer intermediate system. Historically, routers were called "gateways"
in Internet terminology. See gateway, bridge and repeater.
routing: The process of selecting the correct interface and next hop for a
packet being forwarded. See also: hop, router, EGP, IGP.
RPC: Remote Procedure Call. An easy and popular paradigm for
implementing the client-server model of distributed computing. A
request is sent to a remote system to execute a designated procedure,
using arguments supplied, and the result returned to the caller.
There are many variations and subtleties, resulting in a variety of
different RPC protocols.
RTFM: Read The Fantastic Manual. This acronym is often used when
someone asks a simple or common question. The work "Fantastic" is
usually replaced with one much more vulgar.
RTSE: Reliable Transfer Service Element. The OSI application service
element responsible for transfer of bulk-mode objects.
S
SAP: Service Access Point. The point at which the services of an OSI
layer are made available to the next higher layer. The SAP is named
according to the layer providing the services: e.g., Transport
services are provided at a Transport SAP (TSAP) at the top of the
Transport Layer.
selector: The identifier used by an OSI entity to distinguish among
multiple SAPs at which it provides services to the layer above. See
port.
server: A provider of resources (e.g., file servers and name servers).
See also: client, DNS, Network File System.
Session Layer: The OSI layer that provides means for dialogue control
between end systems.
SGMP: Simple Gateway Management Protocol. The predecessor to SNMP.
See SNMP.
Shadowing: A form of replication in which well-defined units of
information are copies to several DSAs.
SIPP: Simple Internet Protocol Plus. One of the 3 IPng candidates.
See IPng.
SLIP: Serial Line IP. An Internet protocol used to run IP over
serial lines such as telephone circuits or RS-232 cables
interconnecting two systems. SLIP is now being replaced by PPP. See
PPP.
SMDS: Switched Multimegabit Data Service. An emerging high-speed
networking technology to be offered by the telephone companies in the
U.S.
SMI: Structure of Management Information. The rules used to define
the objects that can be accessed via a network management protocol.
See MIB.
SMT: Station Management. The part of FDDI that manages stations on a ring.
SMTP: Simple Mail Transfer Protocol. The Internet electronic mail
protocol. It is a server to server protocol, so other protocols are
used to access the messages.
SNA: Systems Network Architecture. IBM's proprietary network
architecture.
SNMP: Simple Network Management Protocol. The network management
protocol of choice for TCP/IP-based internets.
SNMPv2: SNMP version 2. The "second generation" SNMP.
socket: A pairing of an IP address and a port number. See port.
SPAG: Standards Promotion and Application Group. A group of European
OSI manufacturers which chooses option subsets and publishes these in
a "Guide to the Use of Standards" (GUS).
Spam: Term used to describe unsolicited email or newsgroup posts, often
in the form of commercial announcements. The act of sending a spam is
called, naturally 'spamming.'
SQL: Structured Query Language. The international standard language
for defining and accessing relational databases.
subnet mask: See address mask.
subnetwork: A collection of OSI end systems and intermediate systems
under the control of a single administrative domain and utilizing a
single network access protocol. Examples: private X.25 networks,
collection of bridged LANs. See Autonomous System.
Super-JANET: The latest phase in the development of JANET, the UK
educational and research network run by UKERNA. It uses SMDS and ATM to
provide multi-service network facilities for many new applications
including Multimedia Conferencing. See JANET.
T
TCP: Transmission Control Protocol. The major transport protocol in
the Internet suite of protocols providing reliable, connection-
oriented, full-duplex streams. Uses IP for delivery. See TP4.
terminal emulator: A program that allows a computer to emulate a terminal.
The workstation thus appears as a terminal to the remote host.
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.
Telnet: The virtual terminal protocol in the Internet suite of
protocols. Allows users of one host to log into a remote host and
interact as normal terminal users of that host. See VT.
three-way-handshake: The process whereby two protocol entities
synchronize during connection establishment.
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.
token ring: 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.
TOP: Technial Office Protocols. A protocol stack for office automation
developed by Boeing following the OSI model. The protocol suite is very
similar to MAP, except that at the lower layers it uses IEEE 802.3 rather
than IEEE 802.4. See MAP.
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.
TP0: OSI Transport Protocol Class 0 (Simple Class). This is the
simplest OSI Transport Protocol, useful only on top of an X.25
network (or other network that does not lose or damage data).
TP4: OSI Transport Protocol Class 4 (Error Detection and Recovery
Class). This is the most powerful OSI Transport Protocol, useful on
top of any type of network. TP4 is the OSI equivalent to TCP.
transceiver: Transmitter-receiver. The physical device that connects
a host interface to a local area network, such as Ethernet. Ethernet
transceivers contain electronics that apply signals to the cable and
sense collisions.
transfer syntax: A description on an instance of a data type that is
expressed as a string of bits. See abstract syntax.
Transport Layer: The OSI layer that is responsible for reliable end-
to-end data transfer between end systems.
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.
TUBA: The OSI layer that is responsible for reliable end-to-end data
transfer between end systems.
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: type of cable in which pairs of conductors are twisted
together to produce certain electrical properties.
U
UA: User Agent. An OSI application process that represents a human
user or organization in the X.400 Message Handling System. Creates,
submits, and takes delivery of messages on the user's behalf.
UDP: User Datagram Protocol. A transport protocol in the Internet
suite of protocols. UDP, like TCP, uses IP for delivery; however,
unlike TCP, UDP provides for exchange of datagrams without
acknowledgements or guaranteed delivery. See CLTP.
UNIX: A computer operating system (the basic software running on a
computer, underneath things like word processors and spreadsheets). UNIX
is designed to be used by many people at the same time (it is "multi-user")
and has TCP/IP built-in. It is the most common operating system for
servers on the Internet.
URL (Uniform Resource Locator) -- The standard way to give the address
of any resource on the Internet that is part of the World Wide Web (WWW).
An example is http://www.berkeley.edu/. The most common way to use a URL
is to enter into a WWW browser program, such as Netscape. A URL describes
the location of a particular piece of information (document) including
the protocol (http in this example) used to retrieve that information.
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.
UUCP: UNIX to UNIX Copy Program. A protocol used for communication
between consenting UNIX systems. 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.
V
Veronica: Very Easy Rodent Oriented Net-wide Index to Computerized Archives):
Developed at the University of Nevada, Veronica is a constantly updated
database of the names of almost every menu item on thousands of gopher
servers. The Veronica database can be searched from most major gopher menus.
virus: A program which replicates itself on computer systems by
incorporating itself into other programs which are shared among
computer systems.
VT: Virtual Terminal. The OSI Virtual Terminal Service. Similar to Telnet.
W
WAIS: Wide Area Information Servers. WAIS allows users to search and
access different types of information from a single interface. The WAIS
protocol is an extension of the ANSI Z39.50 information retrieval protocol.
See Gopher, Prospero, and World-Wide Web.
white pages: The Internet supports several databases that contain basic
information about users, such as email addresses, telephone
numbers, and postal addresses. These databases can be searched to
get information about particular individuals. Because they serve
a function akin to the telephone book, these databases are often
referred to as "white pages. See also: Knowbot, WHOIS, X.500.
WHOIS: An Internet program which allows users to query a database of
people and other Internet entities, such as domains, networks, and
hosts, kept at the DDN NIC. The information for people shows a
person's company name, address, phone number and email address.
See also: DDN, white pages, Knowbot, X.500.
World-Wide Web (WWW): An easy but powerful global information system, based
on a combination of information retrieval and hypertext techniques.
See Gopher, Prospero, and WAIS.
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.
X
X: 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.500: The CCITT and ISO standard for electronic directory services. See
also: white pages, Knowbot, WHOIS.
XDR: eXternal Data Representation. A standard for machine-
independent data structures developed by Sun Microsystems. Similar
to BER.
X/Open: A group of computer manufacturers that promotes the
development of portable applications based on UNIX. They publish a
document called the X/Open Portability Guide.
X Recommendations: The CCITT documents that describe data
communication network standards. Well-known ones include: X.25
Packet Switching standard, X.400 Message Handling System, and X.500
Directory Services.
X Window System (TM): A popular window system developed by MIT
and implemented on a number of workstations.
Y
Yellow Pages (YP): A service used by UNIX administrators to manage databases
distributed across a network.
Z
zone: A logical group of network devices (AppleTalk).
Updated 04/10/96 by Siegrid Rickenbach.
Send comments to dcnswww@ack.berkeley.edu