Network Support Encyclopedia 15/novell-nsepro-1992-vol15.iso/download/snagls.txt

Text File | 1991-03-12 | 19KB | 555 lines

                             NetWare SNA Glossary

ACCESS CODE
In Novell LAN-based 3270 and 5250 communications products, a name with up
to 15 characters used to select a
host session or group of host sessions through a specified gateway server.
On the server, a host session, a group
of up to 5 host sessions, or a pool or such sessions or session groups is
defined under the access code.

ACF/NCP
Advanced Communications Function/Network Control Program.
Software resident in an IBM 37x5 communications controller that manages
communication between the host
system attached to the controller and other devices on the network
(usually, but not necessarily an SNA
network).

ACF/TCAM
Advanced Communications Function for the Telecommunications Access Method.
Host communications access
method which provides similar functions to those provided by ACF/VTAM, plus
some data queuing functions
not provided by either ACF/VTAM or ACF/VTAME.

ACF/VTAM
Advanced Communications Function for the Virtual Telecommunications Access
Method.  System program
which runs on an IBM host computers and controls communication between host
application or service programs
and terminals.  The prefix ACF distinguishes contemporary VTAM releases
from earlier ones which provided
much less comprehensive support.

ADAPTER
See LAN adapter.

ADDRESS
An identifier for a physical or logical device on a network.  In SNA
networks, each physical unit, logical unit
and system service control point has an address.  In local area networks,
each node on the network has an
address.

ADVANCED PROGRAM-TO-PROGRAM COMMUNICATION
See APPC

API
Application Programming Interface.
The module of network software that communicates with a user's application.
In networks built on the ISO OSI
model, APIs usually work on the seventh layer.

APPC
Advanced Program-to-Program Communications.
An IBM protocol for developing peer-to-peer communications that allows
programs to communicate with equal
control.  APPC is implemented through LU 6.2.

APPLICATION LAYER
The seventh layer of the ISO OSI model.  This layer passes requests and
responses between the network and
applications.

ASCII
American standard Code for Information Interchange.
A code for representing characters to a processor; each character is
represented by 7 bits with an optional eighth
bit for parity checking.  ASCII is used on microcomputers; EBCDIC is used
on IBM host computers.
AS/400
IBM mainframe computer that can act as a host for a Token-Ring gateway
connection.

BROADCAST
To send a message to all users on a network.

CLUSTER CONTROLLER
Also known as a control unit (IBM model numbers 3174, 3172, 3274).  A
machine that supervises terminals and
other peripherals.  When personal computers are connected to a host
computer through a gateway, the gateway
server functions as a cluster controller.


COAXIAL CABLE
Frequently called coax cable, a cable consisting of one conductor within
another conductor, covered by an outer
insulating shield.  Coaxial cable is sometimes used to connect the gateway
server to the host.

COMMUNICATIONS CONTROLLER
Also known as a front-end processor (IBM model numbers 3725, 3745, 3705,
3720).  In remote environments, a
machine directly attached to a host computer, that processes communication
requests.

CONNECTIONLESS SYSTEM
A network type that treats each packet as an individual system
communication (IPX, for example).  Each packet
contains a destination address, allowing it to be delivered independent of
any other packet.

CONNECTION ORIENTED SYSTEM
A network in which two nodes establish a session before they communicate.
During the session, the two nodes
communicate only with each other.  When the transmission is complete, the
session is ended.

CONTROL UNIT
See cluster controller.

CUT
Control-Unit Terminal.  An IBM 3270 terminal attached to a cluster
controller that processes its keystrokes and
managers its buffers.  A control-unit terminal can support one host
communications session at a tine.

DATA FLOW CONTROL LAYER
The fifth layer of the SNA model.
The data flow control layer manages sessions and provides error recovery.


DATA LINK CONTROL LAYER
The second layer of the SNA model.
The data link control layer constructs frames from a bit stream.

DATA LINK LAYER
The second layer of the ISO OSI model.
The data link layer handles the translation between the electrical signals
transmitted by the physical layer and
the bit patterns required by the higher layers.

DATA LINK TRACE
In the SNA Gateway, a diagnostic test in which the gateway simulates the
host to check for proper LAN
functioning.

DATA STREAM
Data that is flowing between points on a network.  A data stream is usually
a succession of messages.

DFT
Distributed Function Terminal.  A coaxially-connected device that does not
require cluster-controller interaction
to respond to keystrokes.
distributed processing
A data processing type in which more than one processor shares the
execution of an application.  In SNA
networks, distributed processing is implemented through APPC.

DOS
Disk Operating System.
The initial operating system used for System/360 mainframes; also, a loose
term for a personal computer
operating system, short for PC-DOS or MS-DOS.
EBCDIC
Extended Binary Coded Decimal Interchange Code.
EBCDIC is for mainframes what ASCII is for microcomputers to represent
different characters.

EGA
Enhanced Graphics Adapter.
A display adapter for personal computers that provides monochrome or
color monitors with 350-line
resolution and graphics capabilities.



END USER LAYER
The seventh layer of the SNA model.  The end user layer is the interface
between the SNA network and user
applications.

FRAME
A message sent over a network.  A frame usually contains data plus address,
control, and error-check
information.  On a LAN, this structure is frequently called a packet.

FREE TOKEN
A unique sequence of bits transmitted on a token ring network.  Each node
must wait for the token before it
transmits.

FRONT-END PROCESSOR (FEP)
See communications controller.

GATEWAY
A network node that operates as an interface between different network
types.  Also a gateway server.

GATEWAY SERVER
A personal computer that runs NetWare SNA Gateway or NetWare SNA Gateway
ELS software, and has a LAN
adapter, and a host interface adapter that enables data transmission
between gateway workstations and a host
computer.

GATEWAY WORKSTATION
A personal computer in a LAN that is connected to the gateway server and
runs NetWare 3270 LAN Workstation
software.

HALF-DUPLEX
A two-way data transmission mode where data between two points is sent one
direction at a time.

HOST
The controlling computer on a network, similar to a file server on a LAN.
In SNA Gateway environments, the
host is usually a mainframe or minicomputer.

HOST INTERFACE ADAPTER
An add-in board for personal computers that can provide direct or remote
connections to a host computer.

HOST SESSION
A temporary logical connection established between two network addressable
units; for example, a gateway
workstation and a host computer.

IBM 3174
A 3270 series cluster controller, introduced in 1987, that can support
Category A coaxially-connected devices (in
CUT mode or DFT mode, single and multiplexed) and/or Token-Ring devices.


IBM 3270
IBM terminals that include models 3278, 3279, 3178 and the 3287
host-addressable printer.

IBM 3274
A 3270 series cluster controller, that can support Category A
coaxially-connected devices (in CUT mode or DFT
mode, single and multiplexed).

IBM 37XX FRONT END PROCESSOR
A 3270 series IBM front-end processor that includes the 3705, 3720, 3725
and 3745 models.  With its associated
software, ACF/NCP, the 37XX controls the operation of a number of attached
communication lines, which may
be operating in a variety of modes and under a variety of protocols.  The
3705 is no longer manufactured, but is
often   used as a non-specific reference for compatible communications.

IBM TOKEN RING LAN
A local area network access mechanism and topology in which a supervisory
frame or token is passed from
station to station in sequential order.  To gain access to the network,
stations must wait for the token to arrive
before transmitting data.  In a token ring, the next logical station
receiving the token is the next physical station
on the     ring.


INTERNETWORK
An interconnected group of networks.

IPL
Initial Program Load.
A command used to restart a host computer or a host virtual machine.
Similar to reboot on a personal computer.


IPX/SPX
The Internetwork Packet Exchange/Sequenced Packet Exchange protocol.
The Novell communications protocol for transmitting data packets on a LAN
installed with NetWare.

ISO
International Standards Organization.
The group that developed the OSI Reference Model.

KBPS
Kilobits per second.
A unit of measure for high-speed data transmission.

LAN
See local area network.

LAYER
Part of a network architecture that performs services and passes data to
another part.  Many network
architectures are designed with seven layers, with each layer providing
isolated functions.

LEASED LINE
A dedicated or private line leased for exclusive use.

LOCAL AREA NETWORK
Also called a LAN.
Personal computers and peripherals within a small area (such as a building
or part of a building) that are linked
so that they share data and resources.

LOGICAL LINK
The top sublayer of the data link layer.  This sublayer control  passes
data to higher layers; the protocol differs
(LLC)  according to the network.

LOGICAL UNIT
A software component of an SNA network that allows a person or application
to access the network;  also called
an LU.  To the network, each user (whether a person or an application) is
an LU.

LU
See logical unit.

LU6.2
Logical unit type 6.2.
In SNA networks, the logical unit that implements distributed processing
and peer-to-peer communications.

MULTICAST
To send a message to more than one user on a network simultaneously.

MULTIPLEXER
A device that accepts many data lines and combines them into a single,
high-speed, composite data stream.

NAU
Network Addressable Unit.
A location in an SNA network that supports one or more ports for
communication through the network.

NAU SERVICES LAYER
The sixth layer of the SNA model.
The NAU services layer provides presentation services and session services
to user processes.


NCP
See network control program.

NetBIOS
Network Basic Input/Output System.
A network protocol used on many LANs.  The Novell IPX/SPX protocol is a
similar protocol.

NETWORK ADDRESSABLE UNIT
In an SNA network, a logical unit, physical unit or system service control
point.

NETWORK CONTROL PROGRAM (NCP)
Firmware in a communications controller that processes control interrupts
for the host.

NETWORK LAYER
The third layer of the ISO OSI model.
The network layer performs switching and routing, especially important in
large internetworks.

NODE
In a network, a physical point where components connect to each other.
Loosely, a component of the network.
For example, a workstation is a node on a LAN.  Cluster controllers or host
computers are nodes in SNA
networks.  Nodes on a LAN are similar to logical units and physical units
in SNA networks.

OFF-LINE TEST
In the NetWare SNA Gateway, a diagnostic test used to check for problems in
the connection between the
gateway and the host.

OSI MODEL
Open Systems Interconnection Reference Model.  The architecture developed
by the ISO to standardize
networking and data communications.  The OSI model has seven layers: the
physical, data link, network,
transport, session, presentation, and application layers.  The OSI model is
frequently used for microcomputer
networks, and the SNA model, for IBM host computer networks.

PACKET
A unit of information sent over a network.
A packet contains data and control and address information.  Packet is
commonly used with microcomputer
networks, and frame, with mainframe networks; the terms are synonymous.

PATH CONTROL LAYER
The third layer of the SNA model.
The path control layer handles routing and traffic control.  For example,
it might group unrelated packets to
send to the same address.

PATH CONTROL NETWORK
The part of an SNA network that links the network units and handles
physical transmission.  The path control
network is similar to the physical and data link layers of the ISO OSI
model.

PEER PROCESS
In a network model, processes operating on the same levels of different
computers; for example, on layer 7 of
computer A and layer 7 of computer B.
PEER-TO-PEER NETWORK
A network whose nodes can each act with equal authority, without having a
master-slave relationship.

PHYSICAL COMMUNICATION
The actual transmission of data from one computer to another; this occurs
on the physical layer of the OSI or
SNA model.

PHYSICAL LAYER
The hardware connection (for example, cabling) between two computers used
for transmitting data.

PHYSICAL UNIT (PU)
An SNA software component that manages a physical device and represents it
to the network.  Each PU supports
one or more logical units (LUs).  The closest microcomputer term is node,
although it does not distinguish
between physical and logical types.


POOLING
A method of assigning codes that control host session allocation on LAN
workstations.  Host sessions can be
pooled in one of the three following ways:
     1) All workstations use the same access code.

     2) All workstations use a unique access code.

     3) Some workstations use the same access code.

PRESENTATION LAYER
The sixth layer of the ISO OSI model.
It performs layer frequently used routines, such as translating data
between EBCDIC and ASCII.

PRESENTATION TRACE
A diagnostic trace used in the gateway to check the data flow between the
gateway and the workstation.

PRIMARY STATION
In an SNA network, the station that controls the link and determines when
other stations may transmit.
Compare secondary station.

PROTOCOL
A set of rules, including data format and error handling, which governs
communication between computers.

PU
See physical unit.

REBOOT
To restart a microcomputer.
In host systems, this is frequently called an IPL or an IML.

RS-232-C
An Electronics Industries Association (EIA) standard for a common
connection used to attach microcomputers to
peripherals.

SESSION LAYER
The fifth layer of the ISO OSI Model, providing administrative jobs for the
network, such as security.

SDLC
Synchronous Data Link Control.
A protocol used to transfer data in SNA environments.

SECONDARY STATION
In an SDLC configuration, a station that is governed by a primary station.
When using the SNA Gateway, the
workstations are secondary stations.

SESSION
A logical connection between two nodes in a network that allows them to
exchange messages.

SNA
See Systems Network Architecture.

SNA model
The seven-layer model for network operations that is part of the Systems
Network Architecture.  Compare OSI
model.

SPX
Sequenced Packet Exchange.
A protocol that allows two workstations or applications to communicate
across the network.  SPX uses the
Internetwork Packet Exchange (IPX) protocol to deliver the messages.

STATUS WORK
One of the frame types sent from the gateway server to the host in response
to a poll command, indicating the
status of the gateway server.


SWITCHED LINE
Within a network, a line that is switched to establish a continuous pathway
between the sender and the receiver.

SYNCHRONOUS
A data transmission mode that synchronizes entire blocks of data.

SYSTEMS NETWORK ARCHITECTURE
A set of protocols, message formats, and other specifications developed by
IBM that unites several generations of
computers, operating systems, peripheral devices, and telecommunications
systems.  SNA specifies how computer
equipment connects and communicates.

SYSTEM SERVICE CONTROL POINT
An SNA software component that manages the network or a portion of it.

TERMINAL
A device with a keyboard and a monitor that sends and receives information
on a network.  A terminal usually
cannot function as an independent system.
TIC
See token ring interface coupler.

TOKEN FRAME
A structure that contains data on a token ring network.  When a node has
data to transmit, it replaces a free
token with a token frame.

TOKEN RING INTERFACE COUPLER (TIC)
Device on IBM 3725 or 3745, allowing the use of Token Ring topology for
communication with local terminal
emulation devices.  The IBM 3174 cluster controller provides the same
capability by way of its optional
token-ring adapter.  In many cases, the IBM 3174 will communicate with both
the host and the terminal
emulation devices via the Token Ring.

TRANSMISSION CONTROL LAYER
The fourth layer of the SNA network.
This layer creates, manages and ends sessions.

TRANSPORT LAYER
The fourth layer of the ISO OSI model.
This layer handles layer the sequencing and guaranteed delivery of packets.

VIRTUAL COMMUNICATION
Communication between corresponding layers of two computers in a network.
For example, between layer 7 of
one computer and layer 7 of another.  Data is not transmitted directly
between the corresponding layers.

VIRTUAL TELECOMMUNICATION ACCESS METHOD (VTAM)
See ACF/VTAM.

WORKSTATION
A network device that contains a central processing unit, a keyboard and a
monitor.  The closest mainframe
equivalent is a terminal; however, terminals do not contain CPUs.