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Glossary - NetworkTop
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Numeric
| 10BASE2 |
Ethernet running on thin coax network cable at 10 Mbps. |
| 10BASE5 |
Ethernet running on thick wire network cable at 10 Mbps. |
| 10BASE-T |
Ethernet running on unshielded twisted pair (UTP) cable
at 10 Mbps. Point-to-point network media, with one end of cable typically
going to repeater/hub and other to network device. |
| 100BASE-TX |
Ethernet running on unshielded twisted pair (UTP) cable
at 100 Mbps. Point-to-point network media, with one end of cable typically
going to repeater/hub and other to network device. |
A
| AAL (ATM Adaptation Layer) |
A collection of standard Asynchronous Transfer Mode (ATM)
protocols that adapt user traffic to the cell format. AAL is subdivided
into the convergence sub-layer (CS), and the Segmentation And Reassembly
(SAR) sub-layer. There are several types of AALs -- AAL0, AAL1, AAL2,
AAL3/4 and AAL5 -- to support the various AAL service classes. |
| AAL0 (AAL Type 0) |
Null protocol. No cell adaptation occurs. |
| AAL1 (AAL Type 1) |
Used for transporting time-dependent Constant Bit Rate
(CBR) traffic, such as audio and video, and emulating Time Division
Multiplexer (TDM)-based circuits, such as digital signal level 1 (DS1)
and E1. Timing information must be exchanged between the source and
the destination. AAL1 supports QoS Class A (defined under QoS in this
glossary). |
| AAL2 (AAL Type 2) |
Used for supporting time-dependent slow or Variable Bit
Rate Real Time (VBR-RT) connection-oriented traffic (e.g., packetized
and compressed audio and video). Timing information must be exchanged
between the source and the destination. AAL2 supports QoS Class B
(defined under QoS in this glossary). |
| AAL 3/4 (AAL Type 3 and 4) |
Used for supporting both connectionless and connection-oriented
Variable Bit Rate Non-Real Time (VBR-NRT) traffic. AAL3 supports quality
of service (QoS) class C while AAL4 supports QoS class D. AAL3 and
AAL4 are combined into one type. AAL3/4 also performs re-sequencing
and cell identification operations. AAL3/4 services are suitable for
supporting interworking with frame relay, SMDS and X.25. |
| AAL5 (AAL Type 5) |
Used for supporting connection-oriented variable bit
rate VBR-NRT data traffic and signaling messages. AAL5 supports quality
of service (QoS) Class X. AAL5 services are suitable for supporting
interworking with most data networking protocols, such as frame relay,
SMDS, Ethernet and Internet Protocol (IP). AAL5 is more popular and
easier to implement than AAL3/4. |
| ABR (Available Bit Rate) |
One of five Asynchronous Transfer Mode (ATM) service
categories. In this service type, the network attempts to pass the
maximum number of cells but does not guarantee cell delivery. ABR
supports Variable Bit Rate (VBR) data traffic with flow control, a
minimum guaranteed data transmission rate, and specified performance
parameters. In exchange for regulating user traffic flow, the network
offers minimal cell loss of accepted traffic. Traffic parameters are
Peak Cell Rate (PCR) and Maximum Cell Rate (MCR). Quality of Service
(QoS) parameters are Cell Loss Ratio (CLR) and Cell Error Rate (CER). |
| Access Network |
Portion of public switched network that connects access
nodes to individual subscribers. Predominantly passive twisted pair
copper wiring. |
| Access Nodes |
Points on edge of the Access Network that concentrate
individual access lines into smaller number of feeder lines. May also
perform various forms of protocol conversion. Examples are Digital
Loop Carrier systems concentrating individual voice lines to T1 lines,
cellular antenna sites, PBXs, and Optical Network Units (ONUs). |
| ACK |
Acknowledgement. |
| Address Prefix |
String of 0 or more bits up to maximum of 152 bits that
is lead portion of one or more ATM addresses. |
| Address Resolution |
Procedure by which client associates LAN destination
with ATM address of another client or the BUS. |
| Administrative Domain |
Collection of managed entities grouped for administrative
reasons. |
| ADPCM (Adaptive Differential Pulse Code Modulation) |
(1) Reduced bit rate variant of PCM audio encoding. (See
also PCM.) This algorithm encodes difference between actual audio
sample amplitude and predicted amplitude and adapts resolution based
on recent differential values. (2) Coding scheme standardized by CCITT
(See CCITT) that allows analog voice to be carried on 32 kbps digital
channel instead of standard 64 kbps PCM channel. |
| ADSI (Analog Display Services Interface) |
Protocol that simplifies use of advanced features by
displaying text messages, generated by a remote computer or central
office switch, on a user's telephone display or television set. |
| ADSL (Asymmetric Digital Subscriber Line) |
Modems attached to twisted pair copper wiring that transmit
from 1.5 to 9 Mbps downstream (to subscriber) and from 16 to 800 kbps
upstream, depending on line distance. |
| AIN (Advanced Intelligent Network) |
Bellcore's switching concept that centralizes significant
amount of intelligence rather than constantly placing more information
in central office switch. |
| AMI (Alternate Mark Inversion) |
Line coding format used on T1 facilities that transmits
ones by alternate positive and negative pulses. |
| AMPS |
Advanced Mobile Phone Service (US), the name applied
to the original analog cellular system. Still the predominant cellular
transmission scheme. |
| ANSI (American National Standards Institute) |
U.S. body and standards-setting organization, not arm
of the government. Accredits various other standards setting committees. |
| API (Application Programming Interface) |
A set of calling conventions that define how a service
is invoked through a software package. |
| AppleTalk |
Communications protocol developed by Apple Computer to
allow networking between Macintoshes. All Macintosh computers have
LocalTalk port, running AppleTalk over 230K bps serial line. Also
runs over Ethernet (EtherTalk) and Token Ring (TokenTalk) network
media. |
| Application Layer |
The top layer of the network protocol stack. The application
layer is concerned with the semantics of work, such as formatting
electronic mail messages. (The lower layers of the network address
how to represent that data and how to reach the foreign node.) |
| Application-Level Firewall |
Firewall system providing service by processes that maintain
complete TCP connection state and sequencing. Often re-addresses traffic
so outgoing traffic appears to have originated from firewall, rather
than internal host. |
| APPN (Advanced Peer to Peer Network) |
IBM network architecture for building dynamic routing
across arbitrary network topologies. Intended as an eventual replacement
for SNA, IBM's static routed, hierarchical network architecture. |
| ARP (Address Resolution Protocol) |
Used to dynamically discover the low-level physical network
hardware address that corresponds to the high-level Internet Protocol
(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. ARP is defined in Request for Comments (RFC) 826. |
| ASCII (American Standard Code for Information Interchange) |
A seven-level code (128 possible characters) used for
data transfer. |
| ASP (Abstract Service Primitive) |
Implementation-independent description of interaction
between service-user and service-provider at particular service boundary,
as defined by Open Systems Interconnection (OSI). |
| Asynchronous Time Division Multiplexing |
Multiplexing technique in which transmission capability
is organized in unassigned time slots that are assined to cells upon
request of each application's instantaneous real need. |
| Asynchronous Transmission |
A transmission method that sends units of data one character
at a time. Characters are preceded by start bits and followed by stop
bits, which provide synchronization at the receive terminal. |
| ATM (Asynchronous Transfer Mode) |
A standard implementation of cell relay, a packet switching
technique using packets of a fixed length, called cells. It is asynchronous
because the recurrence of cells containing information from an individual
user is not periodic. |
| ATM Address |
Defined in UNI Specification as 3 formats, each having
20 bytes in length, including country, area and end-system identifiers. |
| ATM-ARP (ATM Address Resolution Protocol) |
An address resolution protocol for mapping Asynchronous
Transfer Mode (ATM) and Internet Protocol (IP) addresses. (Each host
is assigned a unique IP address.) ATM-ARP can be used for discovering
local area network (LAN) hosts attached to an ATM network or in classical
IP over ATM. |
| ATM Layer Link |
Section of an ATM Layer connection between two adjacent
active ATM Layer entities (ATM-entities). |
| ATM Link |
Virtual path link (VPL) or virtual channel link (VCL). |
| ATM Peer-to-Peer Connection |
Virtual channel connection (VCC) or virtual path connection
(VPC). |
| ATM Traffic Descriptor |
Generic list of traffic parameters that can be used to
capture the intrinsic traffic characteristics of requested ATM connection. |
| ATM User-User Connection |
Association established by ATM Layer to support communication
between two or more ATM service users (i.e., between two or more next
higher entities or between two or more ATM-entities). Communications
over an ATM Layer connection may be either bidirectional or unidirectional.
Same Virtual Channel Identifier (VCI) issued for both directions of
connection at interface. |
| ATM25 |
ATM Forum-defined 25.6Mbit/s cell-based user interface
based on IBM token ring network. |
| ATU-C and ATU-R (ADSL Transmission Unit, Central or Remote) |
Device at end of ADSL line that stands between line and
first item of equipment in subscriber premises or telephone switch.
May be integrated within access node. |
| AUI (Attachment Unit Interface) |
15-pin shielded, twisted pair Ethernet cable used (optionally)
to connect between network devices and MAU. |
| Authentication |
Process of determining identity of user attempting to
access system. |
| Authentication token |
Portable device used for authenticating user. Operates
by challenge/response, time-based code sequences or other techniques.
May include paper-based lists of one-time passwords. |
| Authorization |
Process of determining what types of activities are permitted.
Usually, authorization in context of authentication. |
| Autobaud |
Automatic determination and matching of transmission
speed. |
| Auto-Negotiate |
Clause 28 of the IEEE 802.3u standard specifies MAC sublayer
for identification of speed and duplex mode of connection being supported
by device. Support optional for individual vendors. |
| Auto-sense |
Auto-Negotiation in Clause 28 of IEEE 802.3u standard.
Ability of 10/100 Ethernet device to interpret speed or duplex mode
of attached device and adjust to that rate. |
| AWG (American Wire Gauge) |
System that specifies wire size. Gauge varies inversely
with wire diameter size. |
B
| Backbone |
Main cable in network. |
| Bandwidth on Demand |
Feature that allows remote access device to initiate
second connection to particular site. Used to increase amount of data
transferred to that site to increase desired threshold. Network manager
configuring remote access server will specify number of bits or percentage
of connection bandwidth threshold to trigger the secondary connection.
Multilink PPP is emerging standard to allow this feature to be interoperable.
Currently, the only way to ensure correct operation is to use devices
on both end from same vendor. |
| Baseband LAN |
Local Area Network that uses single carrier frequency
over single channel. Ethernet, Token Ring and Arcnet LANs use baseband
transmission. |
| Bastion host |
System hardened to resist attack. Installed on network
to potentially come under attack. Often component of firewalls or
may be outside Web server or public access system. Generally runs
some form of general purpose operating system (e.g., UNIX, VMS, WNT,
etc.) rather than ROM-based or firmware operating system. |
| Baud |
Unit of signal frequency in signals per second. Not synonymous
with bits per second as signals can represent more than one bit. Baud
equals bits per second only when signal represents single bit. |
| BBC (Broadband Bearer Capability) |
Bearer class field that is part of initial address message. |
| BCD (Binary Coded Decimal) |
Form of coding of each octet within cell, where each
bit has one of two allowable states, 1 or 0. |
| BECN (Backward Explicit Congestion Notification) |
An indicator bit in the frame relay header to notify
the source of traffic that the virtual circuit is passing through
a congested switch. It is set on any traffic flowing from the destination
back to the source that passes through the congested switch. |
| BER (Bit Error Rate) |
(1) Measure of transmission quality generally shown as
negative exponent, (e.g., 10-7 or 1 in 107 bits in error
or 1 in 10,000,000 bits in error). (2) Measure of transmission accuracy
as ratio of bits received in error to bits sent (e.g., 10-9 or 1 error
in 1,000,000,000 bits) is common in voice and data transmission systems. |
| Best Effort |
A Quality of Service (QoS) class in which no specific
traffic parameters and no absolute guarantees are provided. Best effort
includes Undefined Bit Rate (UBR) and Available Bit Rate (ABR). |
| BETRS (Basic Exchange Telecommunications Radio Service) |
Simplest form is "fixed cellular." Form of wireless local
exchange service where handoff is not required. |
| BGP (Border Gateway Protocol) |
An exterior gateway protocol defined in Request for Comments
(RFC) 1267 and 1268. |
| Big-Endian |
A format for storage or transmission of binary data in
which the most significant bit (or byte) comes first. |
| Binaries |
Binary, machine-readable forms of programs that are compiled
or assembled, as opposed to source language forms of programs. |
| Binary |
Characteristic of having only two states, such as current
on and current off. Binary number system uses only ones and zeros. |
| BIP (Bit Interleaved Parity) |
Method used at PHY layer to monitor error performance
of link. Check bit or word is sent in link overhead covering previous
block or frame. Bit errors in payload will be detected and may be
reported as maintenance information. |
| B-ISDN (Broadband Integrated Digital Network) |
Digital network with ATM switching operating at data
rates in excess of 1.5 Mbps. ATM enables transport and switching of
voice, data, image, and video over same infrastructure. |
| BISUP (Broadband ISDN User's Part) |
SS7 protocol that defines signaling messages to control
connections and services. |
| Bit (binary digit) |
Smallest unit of data processing information. Assumes
value of 1 or 0. |
| BNC |
Standardized connector used with Thinnet and coaxial
cable. |
| BOC (Bell Operating Company) |
Any of 22 regulated telephone companies organized into
seven Regional Bell holding companies. See RBOC and RHC. |
| BOOTP (Bootstrap Protocol) |
Used for booting diskless nodes. Described in Request
for Comments (RFC) 951 and 1084. |
| Border Node |
Logical node in a specified peer group, with at least
one link that crosses peer group boundary. |
| Bps (bits per second) |
Units of transmission speed. |
| BRI (Basic Rate Interface) |
ISDN scheme identified as 2B1D that permits two “bearer?channels,
each operating at 64 kbps, and one “data? channel, operating at 16
kbps, to be carried over single twisted pair. |
| Bridge |
A device interconnecting Local Area Networks (LANs) at
the Open Systems Interconnection (OSI) data link layer, and filtering
and forwarding frames according to Media Access Control (MAC) addresses. |
| Broadband |
Wide-band technology capable of supporting voice, video
and data, possibly using multiple channels. |
| Broadband Access |
Access capable of supporting one or more broadband services. |
| Broadband Network |
Network that uses multiple carrier frequencies to transmit
multiplexed signals on single cable. Several networks may coexist
on single cable without interfering with one another. |
| Broadcast |
Data transmission to all addresses or functions. |
| Brouter |
Device that routes specific protocols, such as TCP/IP
and IPX, and bridges other protocols, thereby combining functions
of both routers and bridges. |
| Bus |
LAN topology in which all nodes are connected to single
cable, considered equal, and receive all transmissions on the medium. |
| BUS (Broadcast and Unknown Server) |
Server that handles data sent by LE Client to broadcast
MAC address (FFFFFFFFFFFF), all multicast traffic, and initial unicast
frames sent by LAN Emulation Client. |
| BW (bandwidth) |
Numerical measurement of throughput of system or network. |
| Byte |
Data unit of eight bits. |
C
| CAC (Carrier Access Code) |
Five to seven-digit number that identifies which interexchange
carrier call uses. Subscribers dial these digits with each long distance
call or pre-subscribe to particular carrier and let digital switch
software add CAC. |
| CAC (Connection Admission Control) |
Set of actions taken by network during call setup phase
(or during call re-negotiation) to determine whether connection request
should be accepted or rejected (or whether request for re-allocation
can be accommodated). |
| Call |
Association between two or more users or between user
and network entity that is established by use of network capabilities.
Association may have zero or more connections. |
| CAT-5 (Category 5 UTP) |
Unshielded twisted pair (UTP) standard cabling, commonly
used with fast Ethernet and asynchronous transfer mode (ATM) interfaces
for higher-speed cell transmission (more than 50 Mbps). |
| CBR (Constant Bit Rate) |
One of the five Asynchronous Transfer Mode (ATM) classes
of service. CBR supports the transmission of a continuous bit-stream
of information, such as voice and video traffic, which require a constant
amount of bandwidth allocated to a connection during the transmission. |
| CC (Continuity Cell) |
A cell used periodically to check whether a connection
is idle or has failed. Continuity checking is one of the Operation
Administration And Maintenance (OAM) function types for fault management. |
| CCITT (Comit?Consultatif Internationale de Telegraphique
et Telephonique) |
International group operating under auspices of International
Telecommunications Union (ITU) and charged with establishing telecommunications
standards. Name recently changed to ITU-TSS (International Telecommunications
Union-Telecommunications Standards Sector). |
| CCR (Current Cell Rate) |
The currently acceptable transmission rate for an end-system
as defined by RM cells within Available Bit Rate (ABR). The field
in the RM cell indicates the current complying cell rate (i.e., ACR)
a user can transmit over a Virtual Channel (VC) connection. |
| CDMA (Code Division Multiple Access) |
Digital transmission scheme claimed to be more efficient
than other systems and to offer up to 20 times more call handling
capacity than analog cellular systems. |
| CDPD |
Cellular Digital Packet Data |
| CD-ROM (Compact Disk-Read Only Memory) |
Used by computer to store large amounts of data. |
| CDV (Cell Delay Variation) |
A Quality of Service (QoS) parameter that measures the
difference between the transfer delay of a single cell transfer delay
and the expected transfer delay. This parameter is important for time-sensitive
virtual circuits such as Constant Bit Rate (CBR) and Variable Bit
Rate Real Time (VBR-RT). |
| CDVT (Cell Delay Variation Tolerance) |
Used in Constant Bit Rate (CBR) traffic, it specifies
the acceptable tolerance of the CDV (jitter). |
| Cell |
The 53-byte basic information unit within an Asynchronous
Transfer Mode (ATM) network. The user traffic is segmented into cells
at the source and reassembled at the destination. An ATM cell consists
of a 5-byte ATM header and a 48-byte ATM payload, which contains the
user data. |
| CER (Cell Error Rate) |
A Quality of Service (QoS) parameter that measures the
number of transmitted cells that are erroneous over a specific period
of time (i.e., those that contain errors when they arrive at the destination). |
| CES (Circuit Emulation Service) |
An Asynchronous Transfer Mode (ATM) service in which
Constant Bit Rate (CBR) virtual circuits use AAL1 to emulate an end-to-end
physical circuit by providing a time division multiplexer (TDM)-like
virtual circuit between local access circuits. |
| Challenge/response |
Authentication technique where server sends unpredictable
challenge to user, who computes response using some form of authentication
token. |
| Channel |
Data path between two nodes. |
| Channelized T1/E1 |
T1 or E1 service that is divided into individual 64 Kbps
channels, as opposed to unchannelized service, which uses the entire
bandwidth of the T1 (1.544 Mbps) or E1 (2.048 Mbps). Channelized T1
or E1 lines can consist of switched lines with either in-band signaling
or leased lines. |
| CHAP (Challenge Handshake Authentication Protocol) |
Authentication scheme for PPP where password is required
to begin connection and during the connection. Failure to provide
correct password during login or challenge mode results in disconnect. |
| 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 to the value 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. |
| CIR (Committed Information Rate) |
A term used in frame relay that defines the information
rate the network is committed to providing the user. |
| CLEC |
Competitive LEC |
| CLID (Caller ID) |
Service that permits subscribers to see telephone number
and/or name of calling party. Frequently, “call blocking?is offered,
allowing calling parties to block display of their telephone numbers. |
| CLP (Cell Loss Priority) |
A 1-bit field in the Asynchronous Transfer Mode (ATM)
cell header specifying whether a cell is more or less likely to be
discarded by an ATM network experiencing congestion. |
| CLR (Cell Loss Ratio) |
A Quality of Service (QoS) parameter that gives the ratio
of the lost cells to the total number of transmitted cells. |
| CMIP (Common Management Interface Protocol) |
ITU-TSS standard for message formats and procedures used
to exchange management information to operate, administer, maintain,
and provision a network. |
| CO (Central Office) |
A telephone company office that connects to all local
loops in a given area and where circuit switching of customer lines
occurs. |
| Coaxial Cable |
Electrical cable with solid wire conductor at its center,
surrounded by insulating materials and an outer metal screen conductor
with an axis of curvature coinciding with inner conductor. Examples
are standard Ethernet cable and Thinwire Ethernet cable. |
| COD (Connection Oriented Data) |
Data requiring sequential delivery of its component PDUs
to assure correct functioning of its supported application (e.g.,
voice or video). |
| CODEC (Coder/Decoder) |
Electronic circuit converts analog voice signals into
digital signals for transmission and switching, and digital signal
to analog voice signals so they can be used by telephone. |
| Collision |
Result of two network nodes transmitting on same channel
at same time. Transmitted data is not usable. |
| Collision Detect |
Signal indicating one or more stations are contending
with local station's transmission. Signal is sent by the Physical
layer to the Data Link layer on Ethernet/IEEE 802.3 node. |
| Communication Server |
Dedicated, standalone system that manages communications
activities for other computers. |
| Concentrator |
A wiring hub in a star-topology network. Sometimes refers
to a device containing multiple modules of network equipment. |
| Configuration |
Phase in which LE Client discovers LE Service. |
| Connection |
(1) ATM connection consists of concatenation of ATM Layer
links to provide end-to-end information transfer capability to access
points. (2) In switched virtual connection environments, LAN Emulation
Management entities set up connections between each other using UNI
signaling. |
| Connection-Oriented |
The data communication method in which communication
proceeds through three well-defined phases: connection establishment,
data transfer, and connection release. Transmission Control Protocol
(TCP) is a connection-oriented 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. User
Datagram Protocol (UDP) is a connectionless protocol. |
| Console |
Terminal used to configure network devices at boot (start-up)
time. |
| Core Network |
Combination of switching offices and transmission plant
connecting switching offices together. Linked by several competing
Interexchange networks in U.S. local exchange. Now extends to national
boundaries in rest of world. |
| CPE (Customer Premise Equipment) |
Telecommunications equipment provided for and/or installed
by a service provider at a home or enterprise. |
| CRC (Cyclic Redundancy Check) |
A data transmission error-detection scheme. A polynomial
algorithm is performed on the data, and the resultant checksum is
appended at the end of the frame. The receiving equipment performs
a similar algorithm. |
| Crosstalk |
Noise passed between communications cables or device
elements. |
| CRS (Cell Relay Service) |
A bearer service offered by an asynchronous transfer
mode (ATM) network to the end users delivers Asynchronous Transfer
Mode (ATM) cells directly over the network. |
| Cryptographic Checksum |
One-way function applied to file to produce unique “fingerprint?of
file for later reference. Primary means of detecting file system tampering
on UNIX. |
| CS (Convergence Sublayer) |
(1) General procedures and functions that convert between
ATM and non-ATM formats, describing functions of upper half of AAL
layer. (2) Used to describe conversion functions between non-ATM protocols,
such as frame relay or SMDS and ATM protocols above AAL layer. |
| CSA (Canadian Standards Association) |
One of several bodies that develops telecommunications
standards. |
| CSMA/CD (Carrier Sense Multiple Access with Collision
Detection) |
A protocol in which stations listen to the bus and only
transmit when the bus is free. If a collision occurs, the packet is
retransmitted after a random time-out. Ethernet uses CSMA/CD. |
| CSPDN |
Circuit Switched Public Data Network |
| CSTA |
Computer Supported Telephony Application (ECMA) |
| CSU (Channel Service Unit) |
Equipment installed on customer premises to terminate
a DDS or T1 circuit. CSUs provide network protection and diagnostic
capabilities. |
| CTD (Cell Transfer Delay) |
A quality of service (QoS) parameter that measures the
average time for a cell to be transferred from its source to its destination
over a virtual channel (VC) connection. CTD is the sum of any coding,
decoding, segmentation, reassembly, propagation, processing, and queuing
delays. |
| CTI |
Computer Telephony Integration |
| CTIA |
Cellular Telecommunications Industry Association |
| Cut-through |
Technique for examining incoming packets where Ethernet
switch looks only at first few bytes of packet before forwarding or
filtering it. Faster than looking at whole packet but allows some
bad packets to be forwarded. |
D
| DA (Destination Address) |
Information sent in forward direction indicating address
of called station or customer. |
| DA (Destination MAC Address) |
Six-octet value that uniquely identifies endpoint sent
in IEEE LAN frame headers to indicate frame destination. |
| DACS (Digital Access and Cross Connect System) |
A time-slot switch that allows T1 or E1 lines to be remapped
electronically at the DS-0 (64 Kbps) level. Also called DCS or DXS. |
| Data Connections |
Data VCCs connect LECs to each other and to Broadcast
and Unknown Server. Carry Ethernet/IEEE 802.3 or IEEE 802.5 data frames
as well as flush messages. |
| Data-driven attack |
Attack is encoded in innocuous-seeming data that is executed
by user or other software to implement attack. Concern it may get
through firewall in data form and launch attack against system behind
firewall. AKA denial of service attack. |
| Data Encryption |
Transformation of data into unreadable, meaningless data
through a cryptographic transformation using key. Decryption turns
unintelligible data into meaningful data using a key. |
| Datagram |
A packet or string of bytes carrying and routing data
and sufficient information from source to destination. |
| Data Link Layer |
Layer 2 of the Open System Interconnection (OSI) model.
Layer 2 is concerned with transmitting units of information or frames,
and associated error-checking. It establishes, maintains, and releases
data-link connections between elements in a network. |
| dB (Decibel) |
Logarithmic unit describing ratio of two powers. |
| dBm (Decibel Referenced to a Milliwatt) |
Ratio of two power levels, in which the second is one
milliwatt. |
| DCC (Data Country Code) |
Specifies country in which address is registered. Codes
are given in ISO 3166. Field length is two octets. Digits are encoded
in Binary Coded Decimal (BCD) syntax. Codes left justified and padded
on right with hexadecimal value "F" to fill two octets. |
| DCE (Data Communication Equipment) |
Generic definition of computing equipment that attaches
to network via DTE. |
| DDS (Digital Data Service) |
56 or 64 kbps digital private line channel. |
| DECnetTM |
Digital Equipment Corporation (DEC) proprietary network
architecture running on point-to-point, X.25 and Ethernet networks. |
| DEK (Data Encryption Key) |
Used for encrypting message text and computing message
integrity checks (signatures). |
| DES (Data Encryption Standard) |
A popular, standard encryption scheme. |
| Dial on Demand |
Automatic detection, based on network manager’s pre-defined
parameters, of need to initiate dial-up connection to a remote network. |
| Dialback |
Security feature that ensures people do not log into
modems to which they should not have access. When connection is requested,
system checks user name for validity, then “dials back?number associated
with that user name. |
| Digital Certificate |
Package of information, digitally signed by trusted authority
(usually referred to as a CA or Notary), that binds a public key to
owner. Usually consists of identifier field, public key field, serial
number (of certificate), activation and expiration date, and signature
field. X.509 defines a standard format. |
| Dijkstra's Algorithm |
Algorithm sometimes used to calculate routes given link
and nodal state topology database. |
| Distributed Processing |
System in which each computer or node in network performs
its own processing and manages some of its data while network facilitates
communications between nodes. |
| DLC (Digital Loop Carrier) |
Digital transmission system designed for subscriber loop
plant. Multiplexes many circuits onto very few wires or onto single
fiber pair. |
| DLCI (Data Link Connection Identifier) |
A unique number assigned to a Permanent Virtual Connection
(PVC) endpoint in a Frame Relay network. |
| DLPI (Data Link Provider Interface) |
UNIX International Specification, Revision 2.0.0, OSI
Work Group, August 1991. |
| DMS (Digital Multiplex Systems) |
(1) System that combines number of digital circuits.
(2) Prefix for Northern Telecom family of digital central office switches
(DMS-10, DMS-100/200, DMS-250, DMS-300, and DMS-500.) |
| DNS spoofing |
Assuming DNS name of another system by corrupting name
service cache of victim system or compromising domain name server
for valid domain. |
| Domain |
See Administrative Domain. |
| Domain Name |
Text name appended to host name to form unique host name
across Internets. |
| Download |
Transfer of a file or information from one network node
to another. Generally refers to transferring a file from big node,
such as server, to a small node, such as terminal or printer. |
| DPN (Data Packet Network) |
(1) Network in which “bundles?of information are transmitted,
one after another. Differs from circuit network, in which entire circuit
is dedicated to particular user. (2) Prefix for Northern Telecom’s
DPN data networking switches. |
| DS0 (Digital Subscriber Level Zero) |
A 64 Kbps unit of transmission bandwidth. A worldwide
standard speed for digitizing one voice conversation, and more recently,
for data transmission. Twenty-four DS0s (24x64 Kbps) equal one Digital
Signal Level 1 (DS1). |
| DS1 (Digital Signal Level 1) |
Framing specification used in transmitting digital signals
at 1.544 Mbps on a T1 facility or 2.048 Mbps on an E1 facility. |
| DS2 Channel |
For a T1 line, a 6.312 Mbps channel that consists of
four Digital Signal Level 1 (DS1) channels. For an E1 line, an 8.45
Mbps channel that consists of four DS1 channels. |
| DS3 Channel |
A 44.736 Mbps line consisting of seven DS2 channels.
Also called a T3 line. |
| DS3 PLCP (Physical Layer Convergence Protocol) |
Alternate method used by older T carrier equipment to
locate ATM cell boundaries. Recently been moved to informative appendix
of the ATM DS3 specification and replaced by HEC method. |
| DSL (Digital Subscriber Line) |
A modem technology for transmitting information at high
speeds on existing copper telephone lines to homes and businesses.
DSL requires runs of usually less than 20,000 feet to a central telephone
office. Types of DSL include Asymmetric DSL (ADSL), Symmetric DSL
(SDSL), and High Bit Rate DSL (HDSL). |
| DSLAM (Digital Subscriber Line Access Multiplexer) |
Device that takes number of ADSL subscriber lines and
concentrates these to single ATM line. |
| DSS1 (Digital Subscriber Signaling System #1) |
N-ISDN UNI Signaling. |
| DSS2 (Digital Subscriber Signaling System #2) |
B-ISDN UNI Signaling. |
| DSU (Data Service Unit) |
(1) Equipment used to attach users' computing equipment
to a public network. (2) Device located on the customer’s premises
that converts a digital data signal to a digital transmission signal. |
| DSU (Digital Service Unit) |
A user device interfacing to a digital circuit, such
as DDS or T1 when com-bined with a Channel Service Unit (CSU). The
DSU converts the user’s data stream to bipolar format for transmission. |
| DTE (Data Terminal Equipment) |
(1) Generic definition of external networking interface
equipment, such as modem. (2) Name applied to a piece of terminal
equipment. |
| Dual homed gateway |
System with two or more network interfaces, each of which
is connected to different networks. With firewall, acts to block or
filter some or all traffic trying to pass between networks. |
| DWS (Dialable Wideband Service) |
Alternative name for Multirate ISDN, providing dialed
data connectivity at desired bandwidth on per call basis (from 128
kbps through 1.536 Mbps in 64 kbps increments). |
E
| E.164 |
Public network addressing standard with maximum of 15
digits. ATM uses E.164 addressing for public network addressing. |
| E1 |
The 2.048 Mbps digital carrier system common in Europe. |
| E3 |
The European standard for high-speed digital transmission
operating at 34 Mbps. |
| ECMA |
Previously European Computer Manufacturers Association |
| ECSA (Exchange Carrier Standard Association) |
Standards body sponsored by exchange carriers and accredited
by American National Standards Institute (ANSI). Recently changed
to Alliance for Telecommunications Industry Solutions (ATIS). |
| ECTF |
Enterprise Computer Telephony Forum |
| EGP (Exterior Gateway Protocol) |
A protocol that distributes routing information to the
routers connecting autonomous systems. Today, the term “router?is commonly
used in place of the term “gateway.? There is also a routing protocol
called EGP, defined in STD 18, Request for Comments (RFC) 904. |
| EIA |
Electronics Industry Association |
| ELA (Emulated LAN) |
The Asynchronous Transfer Mode (ATM) segment of a virtual
local area network (VLAN) based on the ATM forum Local Area Network
Emulation (LANE) standard. A VLAN consists of an ELAN segment and
traditional LAN segment. |
| EMI (Electromagnetic Interference) |
Electromagnetic waves emitted by some electrical devices
that distort or overwhelm other communications signals. |
| Encapsulation |
Encapsulating data is a technique used by layered protocols
in which a low level protocol accepts a message from a higher-level
protocol, then places it in the data portion of the lower-level frame.
The logistics of encapsulation require that packets traveling over
a physical network contain a sequence of headers. |
| Encrypting router |
See tunneling router and virtual private network. |
| Enterprise Network |
An information infrastructure that often combines private
and public facilities to cover all of the locations operated by a
single company or corporate enterprise with a single communications
fabric. |
| ESF (Extended Superframe Format) |
A T1 framing format that uses the framing bit to provide
mainte-nance and diagnostic functions. |
| Ethernet |
Most popular LAN technology in use today, with configuration
rules defined by IEEE standard 802.3. 10 Mbps, CSMA/CD baseband network
that runs over thin coax, thick coax, twisted pair or fiber optic
cable. |
| EtherTalk |
Apple Computer's protocol for Ethernet transmissions. |
| ETSI (European Telecommunications Standards Institute) |
Primary telecommunications standards organization. |
F
| FCC |
Federal Communications Commission |
| FCS (Frame Check Sequence) |
Any mathematical formula that derives numeric value based
on bit pattern of transmitted block of information and uses that value
at receiving end to determine existence of any transmission errors. |
| FDDI (Fiber Distributed Data Interface) |
An American National Standards Institute (ANSI) standard
for fiber-optic links with data rates up to 100 Mbps. |
| FEC (Forward Error Correction) |
Technique for detection and correction of errors in digital
data stream. Frequently used in data transmission systems. Redundant
bits are transmitted along with payload. Location and value of these
bits in message allows receiving station to detect and correct errors. |
| FECN (Forward Explicit Congestion Notification) |
A bit set by a frame relay network to notify an interface
(DTE) that congestion avoidance procedures should be initiated by
the receiving device. |
| Fiber Optics |
A transmission medium consisting of thin glass filaments.
Light beams travel through the fiber-optic line, carrying large amounts
of data over long distances. |
| File Server |
Computer that stores data for network users and provides
network access to that data. |
| Filtering |
Process where an Ethernet switch or bridge reads contents
of packet, finds that packet does not need to be forwarded, and drops
it. Filtering rate is rate at which device can receive packets and
drop them without any loss of incoming packets or delay in processing. |
| Firewall |
System or combination of systems that enforces boundary
between two or more networks, controlling access from one to the other. |
| Firmware |
Alterable programs in semipermanent storage, such as
some type of read-only or flash reprogrammable memory. |
| Flash ROM |
See ROM. |
| Flow Control |
A congestion control mechanism in which an Asynchronous
Transfer Mode (ATM) system implements flow control. |
| FOTS (Fiber Optic Transmission System) |
Generic term applied to any fiber optic transmission
system. |
| Fractional T1 |
A service provided by carriers in which a full T1 link
is leased to the customer, but the service charge is calculated based
only on the number of timeslots used. |
| FRAD (Frame Relay Access Device) |
A device responsible for framing data with header and
trailer infor-mation (control information) before presenting the frame
to the frame relay switch. |
| Fragment |
A piece of a packet. When a router is forwarding an Internet
Protocol (IP) packet to a network that has a maximum packet size smaller
than the forwarded 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. |
| Frame |
A data link layer “packet?that contains the header and
trailer information required by the physical medium. Network layer
packets are encapsulated to become frames. The terms packet, datagram,
segment, and message are also used to describe logical information
groupings. |
| Frame Relay |
A network interface providing high-speed frame or packet
transmission with minimum delay and an efficient use of bandwidth. |
| Frame Relay Frame |
A variable-length unit of data in frame relay format
that is transmitted as pure data through a frame relay network. |
| Framing |
At the physical and data link layers of the Open System
Interconnection (OSI) model, bits are fit into units called frames.
Frames contain source and destination information, flags to designate
the start and end of the frame, plus information about the integrity
of the frame. All other information, such as network protocols and
the actual payload of data, is encapsulated in a packet, which is
encapsulated in the frame. |
| FRS (Frame-Relay Service) |
Connection oriented service capable of carrying up to
4096 bytes per frame. |
| FTP (File Transfer Protocol) |
A protocol that allows a user on one host to access and
transfer files to and from another host over a network. FTP is usually
the name of the program the user invokes to execute the protocol.
The Internet Protocol (IP) version is defined in STD 9, Request for
Comments (RFC) 959. |
| FTTC (Fiber to the Curb) |
Fiber placed in long distance network, feeder plant,
and distribution plant. Fiber then proceeds to curb, with copper going
from curb to home. |
| FTTH (Fibre to the Home) |
Network where optical fibre runs from telephone switch
to subscriber's location or home. |
| FTTK (Fiber to the Kerb) |
See Fiber to the Curb. |
| Full Duplex |
A circuit or device permitting transmission in two directions
at the same time. |
| FUNI (Frame User Network Interface) |
A frame-based interface which supports signaling and
Quality of Service (QoS) to an Asynchronous Transfer Mode (ATM). To
inter-operate with a frame relay end system, the ATM switch should
support FRF.8, which is the frame relay/ATM service Internetworking
specification. |
G
| G.703 |
ITU-T Recommendation, “Physical/Electrical Characteristics
of Hierarchical Digital Interfaces.?/font> |
| G.704 |
ITU-T Recommendation, “Synchronous Frame Structures Used
at Primary and Secondary Hierarchy Levels.?/font> |
| G.723 |
Voice compression algorithm used in H.324 . |
| G.804 |
ITU-T Recommendation, “ATM Cell Mapping into Plesiochronous
Digital Hierarchy (PDH).?/font> |
| G.SHDSL |
One of the versions of DSL (Please see DSL). |
| GARP |
Generic Address Resolution Protocol |
| Gateway |
Today, the term “router?is used in place of the original
term “gateway,?a communications device/program that passes data between
networks with similar functions but dissimilar implementations. A
router or gateway should not be confused with a protocol converter,
in which a router is a Layer 3 (network layer) gateway, and a mail
gateway is a Layer 7 (application layer) gateway. |
| Gbps (Giga Bits per Second) |
Giga is the prefix representing 109, or one
billion. For example, 8 gbps is 8 billion data bits per second. |
| GFC (Generic Flow Control) |
A 4-bit field within the Asynchronous Transfer Mode (ATM)
cell header that may be used to identify whether or not an ATM system
implements congestion control. |
| GMRP |
Generic Multicast Resolution Protocol |
| GSM (Global System for Mobile Communications) |
Comprehensive network specification that includes transmission
scheme, network architecture, and network services. Current standard
in Europe and many countries in Asia and proposed standard for personal
communication services in North America. |
| GVRP |
Generic VLAN Resolution Protocol |
H
| H.223/H.245 |
Multiplexing and control protocol for H.324. |
| H.263 |
Video compression algorithm used in H.324. |
| H.323 |
A set of International Telecommunication Union (ITU)
standards that define a framework for the transmission of real-time
voice communications through Internet protocol (IP)-based packet-switched
networks. The H.323 standards define a gateway and a gatekeeper for
customers who need their existing IP networks to support voice communications. |
| H.324 |
New communications standard for sharing video, voice,
and data over single analog telephone line. |
| H0 Channel |
384 kbps channel that consists of six contiguous DS0s
(64 kbps) of T1 line. |
| H10 Channel |
North American 1472 kbps channel from T1 or primary rate
carrier. Equivalent to 23 64 kbps channels. |
| H11 Channel |
North American primary rate used as single 1536 kbps
channel. Uses 24 contiguous DS0s or entire T1 line, except for 8 kbps
framing pattern. |
| H12 |
European primary rate used as single 1920 kbps channel
(30 64 kbps channels or entire E1 line, except for 64 kbps framing
and maintenance channel. |
| Half Duplex |
A circuit or device capable of transmitting in two directions,
but not at the same time. |
| Hardware Address |
See Network Address. |
| H-Channel |
ISDN bearer services with pre-defined speeds and starting
and stopping locations on PRI that are contiguously transported from
one PRI site through networks to another PRI site. |
| HDLC (High-level Data Link Control) |
A synchronous, bit-oriented link layer protocol for data
transmission. Frame relay is an example of an HDLC-based packet protocol. |
| HDSL (High Bit-Rate Digital Subscriber Line) |
A high-performance twisted pair transmission technology,
best known as an enhanced transport mechanism for T1 or E1 service.
It is designed for the local loop between a customer’s premises and
an area exchange central office. |
| Header |
The portion of a packet that precedes the actual data
and contains source and destination addresses, error checking, and
other fields. |
| Heartbeat |
Ethernet-defined SQE signal quality test function. |
| HEC (Header Error Control) |
Using fifth octet in ATM cell header, ATM equipment may
check for error and correct contents of header. Check character is
calculated using CRC algorithm allowing single bit error in header
to be corrected or multiple errors to be detected. |
| Hello Packet |
Type of PNNI Routing packet exchanged between neighboring
logical nodes. |
| Heterogeneous network |
A network running multiple network layer protocols. |
| 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 Table |
List of TCP/IP hosts on network along with their IP addresses. |
I
| I.356 |
ITU-T Specifications for Traffic Measurement. |
| I.361 |
B-ISDN ATM Layer Specification. |
| I.362 |
B-ISDN ATM Layer (AAL) Functional Description. |
| I.363 |
B-ISDN ATM Layer (AAL) Specification. |
| I.432 |
ITU-T Recommendation for B-ISDN User-network Interface. |
| IASG (Internetwork Address Sub-Group) |
Range of internetwork layer addresses summarized in internetwork
layer routing protocol. |
| ICMP (Internet Control Message Protocol) |
An extension to the Internet Protocol (IP). ICMP enables
the generation of error messages, test packets and informational messages
related to Internet protocol. It is defined in STD 5, Request for
Comments (RFC) 792. |
| IEC (Inter-exchange Carrier) |
Long distance telephone company. See IXC. |
| IEEE (Institute of Electrical and Electronic Engineers) |
An international professional society issuing its own
standards. The IEEE is a member of the American National Standards
Institute (ANSI) and International Standards Organization (ISOs). |
| IEEE 802.3 |
Local Area Network protocol suite with 10 Mbps or 100
Mbps throughput. Uses Carrier Sense Multiple Access bus with Collision
Detection CSMA/CD media-access method and physical and data link layer
specifications of local area network. Includes 10BASE2, 10BASE5, 10BASE-FL,
and 10BASE-T Ethernet implementations. Allows users to share network
cable, but only one station can use the cable at a time. Variety of
physical medium-dependent protocols are supported. |
| IEEE 802.5 |
Local Area Network protocol suite commonly known as Token
Ring. Standard originated by IBM for token-passing ring network that
can be configured in star topology. Supports versions 4 Mbps and 16
Mbps. |
| IETF (Internet Engineering Task Force) |
A group that was initially responsible for developing
specifications required for the interoperable implementation of Internet
Protocol (IP). |
| IGP (Interior Gateway Protocol) |
A protocol that distributes routing information to the
routers within an autonomous system. (Today the term “router? is used
in place of “gateway.?/font> |
| IISP (Interim Inter-switch Signaling Protocol) |
A protocol that uses user network interface (UNI)-based
signaling (i.e., UNI 3.0/3.1) and pre-fix routing for switch-to-switch
communication. IISP is formally known as Private Network-Network Interface
(PNNI) Phase 0. |
| ILMI (Interim Local Management Interface) |
A Simple Network Management Protocol (SNMP)-based network
management interface between an end-system and an asynchronous transfer
mode (ATM) switch for status and configuration reporting and registering/deregistering
ATM addresses. |
| IMA (Inverse Multiplexing over ATM) |
A method to pass Asynchronous Transfer Mode (ATM) traffic
over multiple E1/T1 links while maintaining the ATM quality of service
and optimizing bandwidth usage. |
| Insider Attack |
Attack originating from inside protected network. |
| Instance ID |
Subset of an object's attributes that serve to uniquely
identify MIB instance. |
| Internet |
Series of interconnected local, regional, national, and
international networks, linked using TCP/IP. Links many government,
university, and research sites. Provides e-mail, remote login, and
file transfer services. |
| Internet Address |
Also known as an Internet Protocol (IP) address. This
is a 32-bit hardware-independent address assigned to hosts using the
transmission control protocol/Internet protocol (TCP/IP) suite. |
| Internet Datagram |
Unit of data exchanged between pair of internet modules
that includes internet header. |
| Internet Protocol Suite |
Official name of TCP/IP, as used in Internet standards
documents. See TCP/IP. |
| Internetwork |
Process of connecting two networks together. Result is
referred to as an internet. |
| Internetworking |
General term used to describe the industry composed of
products and technologies used to link networks together. |
| Intranet |
Closed network of computers that uses similar technology
to the Internet, such as Web servers and browsers, to make information
available to controlled group of users. May have connection to Internet
or may exist on Internet, achieving controlled access through passwords
or other means. |
| Intrusion detection |
Detection of break-ins or break-in attempts, manually
or via software expert systems that operate on logs or other information
available on network. |
| IOP (Interoperability) |
Ability of equipment from different manufacturers (or
different implementations) to operate together. |
| IP (Internet Protocol) |
The network layer protocol of the transmission control
protocol/Internet protocol (TCP/IP) suite. Defined in STD 5, Request
for Comments (RFC) 791. It is a connectionless, best-effort packet
switching protocol. |
| IP Address |
See Network Address. |
| IPCP |
IP Control Protocol. |
| I-PNNI (Integrated Private Network-Network Interface) |
PNNI-compatible protocol used to exchange information
between routers that augment or replace protocols such as Open Shortest-Path
First (OSPF) and Internetwork Packet Exchange (IPX). This enables
the integration of existing router-based connectionless networks and
Asynchronous Transfer Mode (ATM) networks. |
| IP splicing /hijacking |
Attack where active, established, session is intercepted
and co-opted by attacker. May occur after authentication has been
made, permitting attacker to assume role of authorized user. Primary
protections rely on encryption at session or network layer. |
| IP spoofing |
Attack where system attempts to illicitly impersonate
another system by using the IP network address. |
| IP Telephony |
The transmission of voice over an Internet Protocol (IP)
network. Also called Voiceover IP (VoIP), IP telephony enables users
to make telephone calls over the Internet, intranets, or private Local
Area Networks (LANs) and Wide Area Networks (WANs) that use the Transmission
Control Protocol/Internet Protocol (TCP/IP). |
| IPX (Internetwork Packet Exchange) |
Netware network layer (Layer 3) protocol for transferring
data from servers to workstations. |
| ISDL |
Uses ISDN transmission technology to deliver data at
128kbps into IDSL modem bank connected to router. |
| ISDN (Integrated Services Digital Network) |
A carrier-provided service that enables a variety of
switched digital data and voice transmission to be accommodated simultaneously. |
| ISO (International Standards Organization) |
An international organization involved in writing communi-cations
standards. |
| ISO Layered Model |
References that specify how dissimilar computing devices,
such as Network Interface Cards (NICs), bridges and routers, exchange
data over a network. Model has seven layers. |
| ISP (Internet Service Provider) |
Organization offering and providing Internet services
to public, with own computer servers to provide services offered. |
| ITU (International Telecommunication Union) |
A European-based, international advisory committee recommending
worldwide standards for transmission. |
| ITU H.222 |
ITU-T Study Group 15 standard that addresses multiplexing
of multimedia data on ATM network. |
| ITU Q.2100 |
B-ISDN Signaling ATM Adaptation Layer Overview. |
| ITU Q.2110 |
B-ISDN Adaptation Layer, Service Specific Connection
Oriented Protocol. |
| ITU Q.2130 |
B-ISDN Adaptation Layer, Service Specific Connection
Oriented Function for Support of Signaling at UNI. |
| ITU Q.2931 |
Signaling standard for ATM to support Switched Virtual
Connections. Based on signaling standard for ISDN. |
| ITU Q.931 |
Signaling standard for ISDN to support SVCs. Basis for
signaling standard developed for Frame Relay and ATM. |
| ITU Q.933 |
Signaling standard for Frame Relay to support SVCs. Based
on the signaling standard for ISDN. |
| ITU-T (International Telecommunications Union Telecommunications) |
International body of member countries that defines recommendations
and standards relating to the international telecommunications industry.
Defined and published fundamental standards for ATM. (Previously CCITT.) |
J
| Jitter |
The deviation of a transmission signal in time or phase.
It can introduce errors and loss of synchro-nization in high-speed
synchronous communications. |
K
| kbps (kilobits per second) |
Represents 103 or 1000. For example, 64 kbps
is 64,000 data bits per second. |
| Kermit |
Popular file transfer and terminal emulation program. |
L
| LAN (Local Area Network) |
A data transmission facility connecting a number of communicating
devices (computers, terminals and printers) within a single room,
building, campus or other limited geographical area. |
| LANE (LAN Emulation) |
An Asynchronous Transfer Mode (ATM) forum standard that
provides support for native Local Area Network (LAN) protocols across
an ATM network by emulating the media access control (MAC) protocol.
LANE defines a single Virtual Local Area Network (VLAN) consisting
of traditional LAN segments and an Emulated Local Area Network (ELAN)
segment across the ATM network. Routers will connect multiple VLANs. |
| Leaky Bucket |
A flow control algorithm in which cells are monitored
to check whether they comply with the established connection parameters.
Non-conforming cells are either tagged or dropped from the network.
The analogy is taken from a bucket with a hole in its bottom that
allows the fluid to flow out at a certain rate. |
| Line Speed |
Maximum rate, expressed in bps, at which data can reliably
be transmitted over line using given hardware. |
| Little-Endian |
A format for storage or transmission of binary data in
which the least significant byte (bit) comes first. |
| LLC (Logical Link Control) |
The upper portion of the data link layer, as defined
in Institute of Electrical and Electronic Engineers (IEEE) 802.2.
The LLC sub-layer presents a uniform interface to the user of the
data link service, which is usually the network layer. Beneath the
LLC sub-layer is the media access control (MAC) sub-layer. |
| LMI (Local Management Interface) |
A frame relay network management mechanism that uses
Data Link Connection Identifiers (DLCIs) 0 and 1023 to pass management
messages over the User-To-Network Interface (UNI). |
| Load Balancing |
A technique that distributes network traffic along parallel
paths to maximize the available network bandwidth while providing
redundancy. |
| LocalTalk |
Apple Computer's proprietary 230 Kbps baseband network
protocol. Uses CSMA/CD access method over unshielded twisted pair
wire. |
| LSB (Least Significant Bit) |
Lowest order bit in binary representation of numerical
value. |
| LSSGR (LATA Switching System Generic Requirements) |
Multi-volume set of Bellcore technical references dealing
with basic switching requirements used by switch manufacturers, procurement
staffs, planners, and switch technicians. |
| LTE (SONET Lite Terminating Equipment) |
ATM equipment terminating communications facility using
SONET Lite Transmission Convergence (TC) layer. Usually reserved for
end user or LAN equipment. Does not implement some maintenance functions
used in long haul networks, such as termination of path, line, and
section overhead. |
M
| MAC (Media Access Control) |
A protocol that defines the way workstations gain access
to transmission media. MAC is most widely used in reference to Local
Area Networks (LANs). For Institute of Electrical and Electronic Engineers
(IEEE) LANs, the MAC layer is the lower sub-layer of the data link
layer protocol. |
| MAN (Metropolitan Area Network) |
A network that provides regional connectivity within
a metropolitan area (such as city). MANs are categorized between Local
Area Networks (LANs) and Wide Area Networks (WANs). |
| MAU (Medium Attachment Unit) |
Device used to convert signals from one Ethernet medium
to another. |
| Mbps (Megabits per second or millions of bits per second) |
Measure of digital transmission speed used in computer
and telephone networks. |
| MBS (Maximum Burst Size) |
A traffic parameter that specifies the maximum number
of Asynchronous Transfer Mode (ATM) cells in a burst that can be transmitted
at the Peak Cell Rate (PCR). |
| MCR (Maximum Cell Rate) |
An Available Bit Rate (ABR) traffic parameter (in cells
per second) that gives the slowest rate at which the network controls
the flow of the source on an ABR Virtual Channel (VC) connection. |
| MIB (Management Information Base) |
A collection of objects that can be accessed via a network
management protocol, such as Simple Network Management Protocol (SNMP).
The objects represent values that can be read or changed. |
| MIB Attribute |
Single piece of configuration, management, or statistical
information that pertains to specific part of PNNI protocol operation. |
| MIB Instance |
Incarnation of MIB object that applies to specific part,
piece, or aspect of PNNI protocol's operation. |
| MII (Media Independent Interface) |
New standard developed for Fast Ethernet in IEEE 802.3u
specification. Fast Ethernet equivalent to AUI in 10 Mbps Ethernet,
allowing different types of Fast Ethernet media to be connected to
Fast Ethernet device via common interface. |
| MMF (Multimode Fiberoptic Cable) |
Fiberoptic cable in which signal or light propagates
in multiple modes or paths. Since these paths may have varying lengths,
transmitted pulse of light may be received at different times and
smeared so pulses may interfere with surrounding pulses. May cause
signal to be difficult or impossible to receive, sometimes limiting
distance over which MMF link can operate. |
| Modem |
Modulator-demodulator device for changing transmission
signals from digital to analog for transmission over phone lines.
Used in pairs, one at each end of line. |
| MPOA (Multi-Protocol Over ATM) |
Internet Engineering Task Force (IETF)-defined specifications
and procedures that enable network layer protocols to operate directly
on top of an Asynchronous Transfer Mode (ATM) and provide end-to-end
internetworking between hosts in an ATM and non-ATM environment. |
| MPOA Client |
Edge Device Functional Group (EDFG) or Host Behavior
Functional Group (HBFG). device that implements client side of one
or more of MPOA protocols, (i.e., SCP client and/or RDP client). |
| MPOA Server |
Any one of ICFG or RSFG. |
| MPOA Service Area |
Collection of server functions and their clients. Collection
of physical devices consisting of MPOA server plus its set of clients. |
| MPOA Target |
Set of protocol address and path attributes (e.g., internetwork
layer QoS, other information derivable from received packet) describing
intended destination, which MPOA devices may use as lookup keys. |
| MSB (Most Significant Bit) |
Highest order bit in binary representation of numerical
value. |
| MTBF (Mean Time Between Failures) |
Average period of time equipment or component remains
working before failure. |
| MTP (Message Transfer Part) |
Level 1 through 3 protocols of SS7 protocol stack. MTP
3 (Level 3) used to support BISUP. |
| Multiplexer |
Device that allows several users to share single circuit.
Funnels different data streams into single stream. At other end of
communications link, another multiplexer reverses process by splitting
data stream back into original streams. |
| Multiport Repeater |
Repeater, either standalone or connected to standard
Ethernet cable, for interconnecting up to eight Thinwire Ethernet
segments. |
N
| Name Server |
Software that runs on network hosts charged with translating
(or resolving) text-style names into numeric IP addresses. |
| Native Address |
Address that matches one of given node's summary addresses. |
| NB-PCS |
Narrow Band PCS. |
| NCP (Network Control Program) |
Program that runs on VMS machines to configure local
network hardware and remote network devices. |
| NCP |
Network Control Protocol. |
| NDIS (Network Driver Interface Specification) |
See 3COM/Microsoft, LAN Manager: Network Driver Interface
Specification, October 8, 1990. |
| NE (Network Element) |
System that supports at least Network Element Functions
and may also support Operation System Functions/Mediation Functions.
May be realized as either stand alone device or geographically distributed
system. Cannot be further decomposed into managed elements in context
of given management function. |
| NetBIOS/NetBEUI |
Microsoft's networking protocols for its LAN Manager
and Windows NT products. |
| NetWare |
Novell-developed Network Operating System (NOS). Provides
file and printer sharing among networks of Personal Computers (PCs).
Each network must have at least one file server, and access to other
resources is dependent on connecting to and logging into file server.
File server controls user logins and access to other network clients,
such as user PCs, print servers, modem/fax servers, and disk/file
servers. |
| Network |
Interconnected system of computers that can communicate
with each other and share files, data, and resources. |
| Network Address |
Every node on network has one or more associated addresses,
including at least one fixed hardware address, such as “ae-34-2c-1d-69-f1?assigned
by device's manufacturer. Most nodes also have protocol specific addresses
assigned by network manager. |
| Network Layer |
A layer in the Open System Interconnection (OSI) reference
model. The network layer provides address resolution and routing protocols.
Address resolution enables the network layer to determine a unique
network address for a node. Routing protocols allow data to flow between
networks and reach their proper destination. Examples of network layer
protocols include Internet Protocol (IP) and Address Resolution Protocol
(ARP). |
| Network Management |
Administrative services for managing a network, including
configuring and tuning, maintaining network operation, monitoring
network performance, and diagnosing network problems. |
| Network-Level Firewall |
Firewall in which traffic is examined at network protocol
packet level. |
| NFS (Network File System) |
The recognized standard protocol for accessing files
over a network as if they were on local disks. Defined in Request
for Comments (RFC) 1094. |
| NIC (Network Interface Card) |
Adapter card inserted into computer that contains necessary
software and electronics to enable station to communicate over network. |
| NII (National Information Infrastructure) |
"Seamless web of communications networks, computers,
databases, and consumer electronics that puts vast amounts of information
at users' fingertips." Al Gore |
| N-ISDN (Narrowband Integrated Services Digital Network) |
Services include basic rate interface (2B+D or BRI) and
primary rate interface (30B+D, Europe and 23B+D, North America or
PRI). Supports narrowband speeds at/or below 1.5 Mbps. Same as ISDN. |
| NNI (Network Node Interface or Network-to-Network Interface) |
International Telecommunication Union (ITU) standard
interface between nodes within the same network. The Asynchronous
Transfer Mode (ATM) forum distinguishes between two standards; one
for private networks called Private Network-Network Interface (PNNI),
and one for public networks known as Public NNI. |
| NOS (Network Operating System) |
Software for network that runs in file server and controls
access to files and other resources from multiple users. Provides
security and administrative tools. Novell's NetWare, Banyan's VINES,
and IBM's LAN Server are NOS examples. |
| NRZ |
Non-Return to Zero bit encoding. |
| NRZI |
Non-Return to Zero Inverted bit encoding. |
| nx64K |
Circuit bandwidth or speed provided by aggregation of
nx64 kbps channels (where n= integer > 1). 64K or DS0 channel is
basic rate provided by T Carrier systems. |
O
| OAM (Operation Administration and Maintenance) |
A management framework defined by the International Telecommunication
Union (ITU). OAM cells are special-purpose Asynchronous Transfer Mode
(ATM) cells exchanged between two ATM entities for network fault and
performance management, analysis and fault isolation. |
| OC (Optical Carrier) |
A hierarchy of optical signals used to classify speeds
or capacities of fiber lines, especially as related to the Synchronous
Optical Network (SONET) standard. The basic speed is OC-1 (~52 Mbps). |
| Octet |
Term for eight (8) bits that is sometimes used interchangeably
with byte. |
| ODI (Open Data Link Interface) |
A standard interface specification developed by Novell
to enable PC adapter cards to run multiple protocol stacks. |
| OSI (Open Systems Interconnection) |
A seven-layer model of network communications developed
by the International Standards Organization (ISO). |
| OSPF (Open Shortest-Path First) |
A link-state routing protocol defined in Request for
Comments (RFC) 1247. OSPF supports packet authentication and up to
255 hops. |
P
| Packet |
An ordered group of data and control signals transmitted
through a network as a subset of a larger message. |
| PAD (Packet Assembler and Disassembler) |
Device performing the interface between X.25 data network
and asynchronous device such as personal computer. Assembles user
data into packets with identifying information used to control routing. |
| PAP (Password Authentication Protocol) |
Authentication scheme for PPP links. Password can be
specified for both devices on remote link. Failure to authenticate
results in dropped connection prior to start of data transmission. |
| Parity Bit |
An additional non-information bit added to a group of
bits to ensure that the total number of bits in the character is even
or odd. |
| PBX (Private Branch Exchange) |
A private telephone exchange. |
| PC (Protocol Control) |
Mechanism that given application protocol may employ
to determine or control performance and health of application. For
example, protocol liveness may require protocol control information
be sent at some minimum rate. Some applications may become intolerable
to users if they are unable to send at minimum rate. |
| PCI (Protocol Control Information) |
High-speed PC data bus. |
| PCR (Peak Cell Rate) |
An Asynchronous Transfer Mode (ATM) traffic parameter
(in cells per second) that characterizes the source and gives the
maximum rate at which cells can be transmitted. It is calculated as
the reciprocal of the minimum inter-cell interval (the time between
two cells) over a given Virtual Channel (VC) connection. |
| PDU (Protocol Data Unit) |
Message of a given protocol comprising payload and protocol-specific
control information, typically contained in header. Passes over protocol
interfaces that exist between layers of protocols (per OSI model). |
| PHY (Physical layer) |
Layer 1 of the Open System Interconnection (OSI) model.
Layer 1 is concerned with electrical, mechanical and handshaking procedures
over the interface connecting a device to the transmission medium.
In Asynchronous Transfer Mode (ATM), Layer 1 is the bottom layer of
the ATM protocol reference model and is subdivided into two sub-layers:
Transmission Convergence (TC) and Physical Medium (PM). It provides
ATM cell transmission over the physical interfaces that interconnect
the ATM devices. |
| Physical Address |
Address identifying a single node. |
| Physical Layer |
See PHY. |
| Physical Layer (PHY) Connection |
Association established by PHY between two or more ATM
entities. Consists of concatenation of PHY links to provide end-to-end
transfer capability to PHY SAPs. |
| PLCP (Physical Layer Convergence Protocol) |
Defined by the IEEE 802.6 and used for DS3 transmission
of ATM. ATM cells are encapsulated in 125microsecond frame defined
by PLCP, which is defined inside DS3 M-frame. |
| PLL (Phase Lock Loop) |
Mechanism that transfers timing information within data
stream and receiver derives signal element timing by locking its local
clock source to received timing information. |
| PM (Physical Medium) |
Actual physical interfaces, including STS-1, STS-3c,
STS-12c, STM-1, STM-4, DS1, E1, DS2, E3, DS3, E4, FDDI-based, Fiber
Channel-based, and STP. Range in speeds from 1.544 through 622.08
Mbps. |
| PMD (Physical Media Dependent) |
Sublayer that defines parameters at lowest level, such
as speed of bits on media. |
| PNNI (Private Network-Network Interface) |
The inter-switch interface within a private Asynchronous
Transfer Mode (ATM) domain. The PNNI trunking protocol provides hierarchical
ATM-layer routing and Quality of Service (QoS) support. |
| PNNI Protocol Entity |
Body of software in switching system that executes PNNI
protocol and provides routing service. |
| PNNI Routing Control Channel |
VCCs used for exchange of PNNI routing protocol messages. |
| PNNI Routing Domain |
Group of topologically contiguous systems running one
instance of PNNI routing. |
| PNNI Routing Hierarchy |
Hierarchy of peer groups used for PNNI routing. |
| PNNI Topology State Element |
Collection of PNNI information flooded among all logical
nodes within peer group. |
| PNNI Topology State Packet |
Type of PNNI Routing packet used for flooding PTSEs among
logical nodes within peer group. |
| POP (Point Of Presence) |
A site where a collection of telecommunications equipment
(usually digital leased lines and multi-protocol routers) exists. |
| POTS (Plain Old Telephone Service) |
Only name recognized around world for basic analog telephone
service. Takes lowest 4kHz of bandwidth on twisted pair wiring. Any
service sharing line with POTS must use frequencies above POTS or
convert POTS to digital and interleave with other data signals. |
| PPP (Point-to-Point Protocol) |
Provides a standard means of encapsulating data packets
sent over a single-channel Wide Area Network (WAN) link. PPP is the
standard WAN encapsulation protocol for the interoperability of bridges
and routers over synchronous or asynchronous circuits. |
| Presentation Layer |
The Open System Interconnection (OSI) layer that determines
how application information is represented or encoded while in transit
between two end systems. |
| PRI (Primary Rate Interface) |
An ISDN interface providing 23 “B?channels, each operating
at 64 kbps, and single “D?channel also operating at 64 kbps to customer’s
premises. |
| Protocol |
A formal set of conventions governing the formatting
and relative timing of message exchange between two communicating
systems. |
| Protocol Control Information |
Information exchanged between corresponding entities,
using lower layer connection, to coordinate their joint operation. |
| Proxy |
Software agent that acts on behalf of user. Generally
accepts connection from user, makes decision whether or not user or
client IP address is permitted to use proxy, may perform additional
authentication, and completes connection on behalf of user to remote
destination. |
| Proxy ARP |
The technique in which one machine, usually a router,
answers Address Resolution Protocol (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 Internet Protocol (IP) address with two physical networks. |
| PSTN (Public Switched Telephone Network) |
The telecommunications network commonly accessed by standard
telephones, key systems, Private Branch Exchange (PBX) trunks and
data equipment. |
| PTI (Payload Type Identifier) |
A 3-bit field within the Asynchronous Transfer Mode (ATM)
cell header indicating: the ATM Adaptation Layer (AAL) used; whether
a congestion has been experienced (EFCI); and whether or not the cell
contains Operation Administration And Maintenance (OAM) information.
When an AAL5 frame passes through Segmentation And Reassembly (SAR),
the PTI within the last cell identifies the end of this AAL5 frame. |
| PVC (Permanent Virtual Connection) |
A permanent, virtual connection established by the network
management between an origin and a destination. |
| PVP (Permanent Virtual Path) |
A set of Permanent Virtual Channels (PVCs) that exist
between two cross points. |
Q
| QoS (Quality of Service) |
A group of service classes that define the performance
of a given circuit. For an Asynchronous Transfer Mode (ATM), there
are a number of different QoS parameters. |
| QoS Class 0 |
Refers to the best-effort service Undefined Bit Rate
(UBR). |
| QoS Class 1 |
Specifies the parameters for circuit emulation and the
transport of Constant Bit Rate (CBR) uncompressed video. ATM adaptation
layer type 1 (AAL1) supports this kind of delay-sensitive connection-oriented
service. |
| QoS Class 2 |
Specifies the parameters for the transport of Variable
Bit Rate (VBR) audio and video. ATM adaptation layer type 2 (AAL2)
supports this kind of delay-sensitive connection-oriented service. |
| QoS Class 3 |
Specifies the parameters for connection oriented data
transfer. ATM adaptation layer type 3 and 4 (AAL3/4) and AAL5 support
this delay-tolerant class that is intended to provide interoperability
with SMDS and Internet Protocol (IP). |
| QoS Class 4 |
Specifies the parameters for connectionless data transfer.
ATM adaptation layer type 3 and 4 (AAL3/4) or AAL5 can be used to
support this delay-tolerant class that is also intended to provide
inter-operability with SMDS and Internet Protocol (IP). |
| QoS Class X |
Refers to the connection-oriented transport service in
which the traffic type (Constant Bit Rate or Variable Bit Rate and
timing requirements (delay sensitive or non-sensitive) are defined
by the user. QoS Class X is known as an unrestricted service class
that is supported by ATM adaptation layer type 5 (AAL5). |
R
| RADSL (Rate Adaptive ADSL) |
Version of ADSL where modems test line at start up and
adapt their operating speed to maximum line can handle. |
| RAM (Random Access Memory) |
Computer’s direct access memory that can be accessed very
quickly and overwritten with new information. Loses its content when
power is turned off. |
| RD (Routing Domain) |
Group of topologically contiguous systems running one
instance of routing. |
| Remote Access |
Access to network resources not located on same physical
Ethernet (entire site network topology). |
| Remote Control |
Form of remote access where device dialing in assumes
control of another network node. All remote keystrokes translated
into keystrokes on network node. Used primarily with IPX protocol. |
| Remote Node |
Form of remote access where device dialing in acts as
peer on target network. Used with IP and IPX protocols. |
| Repeater |
A device that automatically amplifies, restores, or reshapes
signals before retransmission to compensate for distortion and/or
attenuation. |
| RFC (Request for Comments) |
Documents written by the research and development community
to describe Internet protocols and standards submitted to the Internet
Engineering Task Force (IETF) for review. All Internet standards are
written as RFCs. |
| RIP2 (Routing Information Protocol) |
Used to discover agents and the routes that Internet
Protocol (IP) packets must traverse. This is done automatically using
periodic broadcasts. RIP2 also supports IP subnets. |
| RISC (Reduced Instruction Set Computing) |
Computer processing technology in which microprocessor
understands few simple instructions, providing fast, predictable instruction
flow. |
| Rlogin |
Application that provides terminal interface between
UNIX hosts using TCP/IP network protocol. Unlike Telnet, assumes remote
host is (or behaves like) UNIX machine. |
| RM-Remote Monitoring RMON (Remote Monitoring) |
A management information base that enables a network
monitoring device to be configured and read from remote locations. |
| ROM (Read-only Memory) |
Memory device that retains its information even when
power is off. ROM version of network device does not need to download
as contains entire executable code, so never needs to reload it. Frequently
provided as "flash ROM", which can be reprogrammed by downloading
if user chooses. |
| Route Server |
Physical device that runs one or more network layer routing
protocols and uses route query protocol to provide network layer routing
forwarding descriptions to clients. |
| Router |
An interconnection device that connects individual Local
Area Networks (LANs). Unlike bridges, which logically connect at Open
System Interconnection (OSI) Layer 2, routers provide logical paths
at OSI Layer 3. Like bridges, remote sites can be connected using
routers over dedicated or switched lines to create Wide Area Networks
(WANs). |
| Routing Computation |
Process of applying mathematical algorithm to topology
database to compute routes. Many types may be used. For example, Djikstra
algorithm. |
| Routing Constraint |
Generic term that refers to topology constraint or path
constraint. |
| Routing Protocol |
General term indicating protocol run between routers
and/or route servers to exchange information used to allow computation
of routes. Result is one or more forwarding descriptions. |
| RSVP (Resource reSerVation Protocol) |
A protocol developed for supporting different quality
of service (QoS) classes for Internet Protocol (IP) applications. |
S
| S/Key |
Freely available authentication system, developed at
Bellcore (based on paper by Leslie Lamport of DEC) that avoids many
types of password attacks. |
| S/WAN |
Emerging standard for secure firewall-to-firewall communication. |
| SA (Source Address) |
Address from which the message or data originated. |
| SAAL (Signaling ATM Adaption Layer) |
Resides between the ATM layer and the Q.2931 function
and provides reliable transport of Q.2931 messages between Q.2931
entities (e.g., ATM switch and host) over ATM layer and two sublayers:
common part and service-specific part. |
| SAP (Service Access Point) |
Remote SAP used when application initiates an outgoing
call to remote ATM device to specify ATM address of remote device
and provide further addressing that identifies target software entity
within remote device. Local SAP used when application prepares to
respond to incoming calls from remote ATM devices to specify ATM address
of device housing application and provide further addressing that
identifies the application within local device. Several groups of
SAPs are specified as valid for Native ATM Services. |
| SAP |
Service Advertisement Protocol |
| SAR (Segmentation and Reassembly) |
Segments the information frames into cells at the source
and reassembles these cells back into information frames at the destination.
These activities occur at the lower part of the ATM Adaptation Layer
(AAL). Each AAL type has its own SAR format. |
| SCAI (Switch-to-Computer Applications Interface) |
Protocol that allows subscriber’s computer to interact
with digital switch, making it possible to coordinate information
in database with incoming and outgoing phone calls to allow, for example,
company representative to receive customer call and simultaneously
receive customer's file for viewing on desktop workstation. |
| SCCP (Signaling Connection and Control Part) |
SS7 protocol that provides additional functions to Message
Transfer Part (MTP). Typically supports Transaction Capabilities Application
Part (TCAP). |
| SCR (Sustainable Cell Rate) |
A traffic parameter that characterizes a bursty source
and specifies the max-imum average rate at which cells can be sent
over a given Virtual Channel (VC) connection. It can be defined as
the ratio of the Maximum Burst Size (MBS) to the minimum burst inter-arrival
time. |
| Screened Host |
Host on a network behind screening router. Degree of
access to screened host depends on screening rules in router. |
| Screened Subnet |
Subnet behind screening router. Degree of access to subnet
depends on screening rules in router. |
| Screening Router |
Router configured to permit or deny traffic based on
set of permission rules installed by administrator. |
| SDH (Synchronous Data Hierarchy) |
The European standard for using optical media as the
physical transport for high-speed, long-haul networks. |
| SDH (Synchronous Digital Hierarchy) |
ITU-TSS International standard, similar to SONET, for
transmitting information over optical fiber. |
| SDSL (Symmetric Digital Subscriber Line) |
HDSL plus POTS over single telephone line. Name has not
been adopted by standards group, but is being discussed by ETSI. Operates
over POTS and would be suitable for symmetric services to premises
of individual customers. |
| SE (Switching Element) |
Device or network node that performs ATM switching functions
based on VPI or VPI/VCI pair. |
| Secure virtual private network (secure VPN) |
Secure private network using unsecured public networks
as carriers. Users may use their network as though it were perfectly
secure, isolated LAN, even though it is connected to unsecured public
networks. |
| Segment |
Single ATM link or group of interconnected ATM links
of ATM connection. |
| Server |
Computer that provides resources to be shared on network,
such as files (file server) or terminals (terminal server). |
| Session stealing |
See IP splicing. |
| Shared Ethernet |
Ethernet configuration in which number of segments are
bound together in single collision domain. Hubs produce this type
of configuration where only one node can transmit at a time. |
| SLIP (Serial Link Internet Protocol) |
An Internet protocol for host dial-up connection. SLIP
frames are encapsulated Internet protocol (IP) datagrams in which
SLIP adds just a few bytes of control data. |
| SMDS (Switched Multimegabit Data Service) |
Public, wide-area packet-switched data service developed
by Bellcore that provides DS-1 to DS-3 switched access. |
| SMTP (Simple Mail Transfer Protocol) |
A protocol, defined in STD 10, Request for Comments (RFC)
821, used to transfer electronic mail between computers. It is a server-to-server
protocol, so other protocols are used to access the messages. |
| SNMP (Simple Network Management Protocol) |
The network management protocol of the Transmission Control
Protocol/Internet Protocol (TCP/IP) suite. |
| SONET (Synchronous Optical Network) |
A standard for using optical media as the physical transport
for high-speed, long-haul networks. SONET basic speeds start at 51.84
Mbps and go up to 2.5 Gbps. |
| Source MAC Address |
Six-octet value uniquely identifying end point sent in
IEEE LAN frame header to indicate source of frame. |
| SS7 (Signaling System 7) |
A signaling method separate from the voice or data channel
that lets intelligent network elements exchange information among
themselves. |
| Store and Forward |
Technique for examining incoming packets on Ethernet
switch or bridge where whole packet is read before forwarding or filtering.
Slightly slower process than cut-through, but ensures that all bad
or misaligned packets are eliminated from network by switching device. |
| STP (Shielded Twisted Pairs) |
General term for shielded cabling systems that are designed
specifically for data transmission. Also means Spanning Tree Protocol,
a routing protocol that eliminates routing loops in a network. |
| STS-1 (Synchronous Transport Signal 1) |
SONET standard for transmission over OC-1 optical fiber
at 51.84 Mbps. |
| STS-n (Synchronous Transport Signal “n? |
SONET standards for transmission over OC-n optical fiber
by multiplexing “n?(integer) STS-1 frames (e.g., STS-3 at 155.52 Mbps,
STS-12 at 622.08 Mbps, and STS-48 at 2.488 Gbps). |
| STS-nc (Synchronous Transport Signal “n? concatenated) |
SONET standards for transmission over OC-n optical fiber
by multiplexing “n?(integer) STS-1 frames (e.g., STS-3 at 155.52 Mbps,
STS-12 at 622.08 Mbps, and STS-48 at 2.488 Gbps but treating information
fields as single concatenated payload). |
| 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. It is distinguished by a subnet number. |
| SVC (Switched Virtual Circuit) |
A logical connection between two points that is established
dynamically and exists during transmission only. In Asynchronous Transfer
Mode (ATM) networks, the Switched Virtual Circuit (SVC) connection
is established via signaling. End systems transmit their User Network
Interface (UNI) 3.1 or 4.0 signaling request via the Q.2931 signaling
protocol. |
| Switch |
Multiport Ethernet device designed to increase network
performance by allowing only essential traffic on attached individual
Ethernet segments. Packets are filtered or forwarded based upon their
source and destination addresses. |
| Synchronous Transmission |
Transmission in which data bits are sent at a fixed rate,
with the transmitter and receiver synchronized. |
T
| T1 |
A digital transmission link with a capacity of 1.544
Mbps used in North America. Typically channeled into 24 digital subscriber
level zeros (DS0s), each capable of carrying a single voice conversation
or data stream. T1 uses two pairs of twisted pair wires. |
| T1E1 |
ANSI standards sub-committee dealing with Network Interfaces. |
| T1M1 |
ANSI standards sub-committee dealing with Inter-Network
Operations, Administration and Maintenance. |
| T1Q1 |
ANSI standards sub-committee dealing with performance. |
| T1S1 |
ANSI standards sub-committee dealing with services, architecture,
and signaling. |
| T1X1 |
ANSI standards sub-committee dealing with digital hierarchy
and synchronization. |
| T3 |
A digital transmission link with a capacity of 45 Mbps,
or 28 T1 lines. |
| TCP (Transmission Control Protocol) |
An Internet standard transport layer protocol defined
in STD 7, Request for Comments (RFC) 793. It is connection-oriented
and stream-oriented, as opposed to User Datagram Protocol (UDP). |
| TCP (Test Coordination Procedure) |
Set of rules to coordinate test process between lower
tester and upper tester. Enables lower tester to control operation
of upper tester. May, or may not, be specified in abstract test suite. |
| TCP/IP (Transmission Control Protocol/Internet Protocol) |
Also known as the Internet protocol suite. This suite
of protocols is used on the Internet, often for heterogeneous internetworking. |
| TDM (Time Division Multiplexer) |
A device that divides the time available on its composite
link among its channels, usually interleaving bits (Bit TDM) or characters
(Character TDM) of data from each terminal. |
| TE (Terminal Equipment) |
Endpoint of ATM connection(s) and termination of various
protocols within connection(s). |
| Telnet |
The virtual terminal protocol in the Internet suite of
protocols. It lets users on one host use the Internet to access and
work as terminal users of a remote host. |
| TFTP (Trivial File Transfer Protocol) |
A simplified version of the file transfer protocol that
transfers files but does not provide password protection or user directory
capability. |
| Thickwire |
Half-inch diameter coax cable. |
| Thinwire |
Thin coaxial cable similar to that used for television/video
hookups. |
| Throughput |
Rate of data transmitted between two points in given
amount of time (e.g., 10 Mbps). |
| TIA |
Telecommunication Industry Association |
| Token Ring |
Developed by IBM, this 4 or 16 Mbps network uses ring
topology and token-passing access method. |
| TP-MIC (Twisted-Pair Media Interface Connector) |
Connector jack at end user or network equipment that
receives twisted pair plug. |
| Traffic Policing |
Mechanism whereby any traffic that violates the traffic
contract agreed to at connection setup is detected and discarded. |
| Traffic Shaping |
A method of smoothing bursty traffic in order to present
a more uniform traffic rate to the network. |
| Transmission Control Protocol |
Protocol that provides reliable transmission of packets
over IP. |
| TTL (Time to Live) |
A field in the Internet Protocol (IP) header that indicates
how long this packet should be allowed to survive before being discarded.
It is primarily used as a hop count. |
| Tunneling |
Refers to the encapsulation of protocol A within protocol
B, such that A treats B as though it were a data link layer. |
| Tunneling Router |
Router or system capable of routing traffic by encrypting
it and encapsulating it for transmission across untrusted network,
for eventual de-encapsulation and decryption. |
| Twisted-Pair Cable |
Inexpensive, multiple-conductor cable comprised of one
or more pairs of 18 to 24-gauge copper strands twisted to improve
protection against electromagnetic and radio frequency interference.
May be either shielded or unshielded. Because of narrow bandwidth,
used in low-speed communications, as telephone cable only. |
U
| UBR (Undefined Bit Rate) |
An economical class of Quality of Service (QoS) on a
moment-to-moment basis, without guaranteeing service levels. |
| UDP (User Datagram Protocol) |
A connectionless transport protocol without any guarantee
of packet sequence or delivery. UDP functions directly on top of Internet
Protocol (IP). |
| UNI (User Network Interface) |
The interface, defined as a set of protocols and traffic
characteristics, between the CPE and the Asynchronous Transfer Mode
(ATM) network. |
| UNI 4.0 |
This UNI specification refers to signaling issues in
Available Bit Rate (ABR), Virtual Path (VP) and Quality of Service
(QoS) negotiations. |
| Uplink |
Connectivity from border node to upnode. |
| Upnode |
Border node’s outside neighbor in common peer group. Must
be neighboring peer of one of border node’s ancestors. |
| UT (Upper Tester) |
Representation in ISO/IEC 9646 of means of providing,
during test execution, control and observation of upper service boundary
of IUT, as defined by chosen Abstract Test Method. |
| UTOPIA (Universal Test and Operation Physical Interface
for ATM) |
An interface to provide connectivity at the Physical
Layer (PHY) level among Asynchronous Transfer Mode (ATM) entities. |
| UTP (Unshielded Twisted Pair) |
General term for all cabling systems that are not shielded
and are used for transmission of data. |
V
| V.34 Modem |
International standard for 28.8 kbps modem connections. |
| V.80 |
International standard for “video phone ready?V.34 modems
that defines how video phone software runs on V.80 modems. |
| V.90 |
International standard for 56 kbps modem connections. |
| VADSL (Very high speed ADSL) |
Same as VDSL or subset of VDSL, if VDSL includes symmetric
mode transmission. |
| VBR (Variable Bit Rate) |
Traffic containing bursts but centered around an average
bandwidth. |
| VBR-NRT (Variable Bit Rate Non Real Time) |
One of the VBR service types for transmitting traffic
where timing information is not critical. Since this service type
is delay-tolerant, it is well suited for bursty traffic such as data
communications. |
| VBR-RT (Variable Bit Rate Real Time) |
One of the two VBR service types for transmitting traffic
that depends on timing and control information. It is suitable for
carrying delay-sensitive traffic such as packeted video and audio. |
| VC (Virtual Channel) |
A connection established between end users, in which
packets are forwarded along the same path and bandwidth is not permanently
allocated until it is used. |
| VCI (Virtual Channel Identifier) |
A 16-bit value in the asynchronous transfer mode (ATM)
cell header that provides a unique identifier for the Virtual Channel
(VC) within a Virtual Path (VP) that carries that particular cell. |
| VDSL (Very high data rate Digital Subscriber Line) |
Modem for twisted-pair access operating at data rates
from 12.9 to 52.8 Mbps, with corresponding maximum reach ranging from
4500 to 1000 feet of 24-gauge twisted pair. |
| Virtual Circuit |
A network service that provides connection-oriented service
regardless of the underlying network structure. |
| Virus |
Self-replicating code segment. Viruses may or may not
contain payloads, attack programs, or trapdoors. |
| VLAN (Virtual Local Area Network) |
A network architecture that allows geographically distributed
users to communicate as if they were on a single physical Local Area
Network (LAN) by sharing a single broadcast and multicast domain.
Asynchronous Transfer Mode (ATM) forum LAN emulation supports virtual
Local Area Networks (VLANs). |
| VP (Virtual Path) |
A term to describe a set of Virtual Channels (VCs) between
cross points, grouped together. |
| VPI (Virtual Path Identifier) |
An 8-bit value in the cell header that identifies the
VP and accordingly the virtual channel to which the cell belongs. |
| VPN (Virtual Private Network) |
Public network service in which a customer is provided
a network that appears as though it were a private network. The advantage
of VPNs over the dedicated private networks is that the VPNs allow
a dynamic use of the network resources and offer very reliable, high-speed
and less expensive communications. |
W
| WAN (Wide Area Network) |
A network that typically spans nationwide distances and
usually utilizes public telephone networks. |
| Workgroup Switching |
Configuration in which number of users are connected
to Ethernet network via switch that allows each user to get greater
throughput than would be available through hub. |
X-Y-Z
| X.25 Gateway Access Protocol |
Allows node not directly connected to public data network
to access facilities of that network through intermediary gateway
node. Protocol standard governing packet-switched networks. |
Source: Intel (by022003)
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