S-HTTP S-MIME SAA
sampling rate SANE
SANET SAP SAPONET-P
SAR SAS SASI
SCSI satellite communications SDK
SDLC SDLC Transport SDLLC
secondary station security management
segment selector Serial Port
Serial Transmission Server service point
session Session Layer SGML
SGMP Shareware Sharing Device
shell prompt Shielding shielded cable
shortest-path routing Short Haul Modem SIG
signal-to-noise ratio Signaling signature
SIMD SIMM simplex transmission
single-mode fiber SIP SIPP
sliding window flow control SLIP SLiRP
slow switching SMB SMDS
SMI smiley faces SMP
SMPTE SMT SMTP
SNA SNADS snail mail
SNAP SNI SNMP
SNPA socket SOM
SONET source address source-route bridging
source-route translational source-route transparent Space
SPAG SPAM span
spanning tree spanning-tree algorithm speed matching
split horizon updates spooler SQE
SQL SRAM SRT
SR/TLB SSCP SSCP-PU session
SSI SSL SS/SD
standard standard input
standard output standby monitor StarLAN
star topology start-stop transmission static route
statistical multiplexer STD
STM or STDM Stop bit
store and forward STP stream-oriented
STS-1 stub network
subarea node subchannel Subnet
Subnet Address subnet mask subnet number
subnetwork Sub-rate Multiplexing subvector
summarize SUNET SuperJANET
SURAnet SURFnet SVC
SWITCH switch processor
synchronization Synchronous transmission syntax
HTTP). Is an extension of HTTP, providing independently applicable
security services for transaction confidentiality, authenticity/integrity
and non-repudiability of origin. The protocol emphasizes maximum flexibility
in choice of key management mechanisms, security policies and cryptographic
algorithms bysupporting option negotiation between parties for each transaction.
draft, defining S-HTTP version 1.0, was distributed by the CommerceNet
Consortium in June 1994, is known as ``draft 24''. This document is draft
35; it provides additional clarifying material, and specifies additional
facilities relative to draft 24.
Internet Mail Extensions). Is a specification for
secure electronic mail.Was designed to add security to e-mail messages
format. The security services offered are authentication (using digital
signatures) and privacy (using encryption). For more information about
it surf on S-MIME Home Page
SAA (Systems Application
Architecture). Standards for IBM computers defining communications between
an application and the operating system and user.
sampling rate The rate
at which samples of a particular waveform's amplitude are taken
SANE (Standard Apple Numeric
SANET is the Slovakian Academic network.
SAP (Service Access
Point). The point at which the services of an OSI layer are made available
to the next higher layer. The SAP is named according to the layer providing
the services: e.g., Transport services are provided at a Transport SAP
(TSAP) at the top of the Transport Layer.
SAPONET-P South African
Public packet-switching data network.
SAR (Segmentation And
Reassambly). The process by which data frames are segmented into ATM
celles at the transmitter and reassambled into their original format at
Station). Also known as a Class B station, an SAS is a device attached
to FDDI media through a single PMD
connection. Typically, the PMD connects to a Class A concentrator.
SASI (Shugart Associates
SCSI (Small Computer System
satellite communications Use
of geostationary orbiting satellites to relay data between multiple earth-based
stations. Satellite communications offer high bandwidth, cost which is
not related to distance between earth stations, relatively long propagation
delays, and broadcast capability.
SDK (Software Development
SDLC (Synchronous Data
Link. Control). IBM bit-synchronous link-layer protocol that has spawned
numerous similar protocols, including HDLC
SDLC Transport Cisco
router feature where disparate environments may be integrated into a single,
high-speed, enterprise-wide network .
Cisco routers can pass native SDLC
traffic through point-to-point serial links and multiplex other protocol
traffic over the same links, Cisco routers can also encapsulated SDLC frames
inside IP datagrams for transport over arbitrary (non-SDLC) networks.
SDLLC A feature where
translation between SDLC and IEEE
802.2 type 2 is performed.
SDSL (Single line
Digital Subscriber Line). HDSL
over a single telephone line. This name has been adopted by a single manufacturer,
not a standards group, and may not stick. It important to distinguish,
however, as SDSL operates over POTS
and would be suitable for symmetric services to premises of individual
customers. [Source: ADSL Forum]
SDSU (SMDS Data Service
Unit). A DSU for access to SMDS
via high-speed serial interfaces (HSSI)
and other serial interfaces.
secondary station In
bit-synchronous link-layer protocols such as HDLC,
a station that responds to commands from a primary station. See also primary
security management One
of five categories of network management defined by ISO
for management of OSI networks. Security
management subsystems are responsible for controlling access to netywork
resources. See also accounting management,
configuration management, fault
management, and performance management.
segment Term used in
the TCP specification to describe a single
transport-layer unit of information.
selector The identifier
used by an OSI entity to distinguish
among multiple SAPs at which it
provides services to the layer above. See port.
Serial Port Communications
path through which data is transferred bitwise. Only one wire each is available
for transmitted and receive data.
Serial Transmission The
most common mode of transmission, where the character bits are sent sequentially
one at the time instead of a parallel.
Server A provider of resources
(e.g., file servers and name servers). See also: client,
Domain Name System, Network
File System. [Source: RFC1392]
service point An interface
betweeen non-SNA devices and NetView
that sends alerts from equipment unknown to the SNA
session A related set
of communications transactions between two or more network devices. In
SNA, a logical connection enabling two
NAUs to comunicate.
Session Layer Layer
5 of the OSI reference model. Coordinates
session activity between aplications, including application-level error
control, dialog control, and remote procedure calls.
SGI (Silicon Graphics,
Inc.). Manufacturer of workstations and software for graphics and
image processing. More about SGI
SGML (Standard Generalized
Markup Language). A programming language for typesetting machines that
uses tags to define the format of pages and supports the interchange of
embedded comments, mathematical expressions, and data-retrieval information.
SGMP (Simple Gateway
Monitoring Protocol). A network management protocol that was considered
for Internet standardization and later envolved into SNMP documented in
The predecessor to SNMP. See SNMP.
Shareware A distribution
method for software. The author lets the user try out the fully functional
software for a certain amount of time at no charge. If the customer wants
to keep and use the product after the period he must pay the requested
fees. This method depends heavily on the honesty of the user.
Sharing Device A device
that enables sharing of a single resource (modem, mux or computer port)
among several devices (terminals, controllers or modems). Used only in
shell In UNIX a utility
program that enables the user to interact with the UNIX operating system.
Commands entered by the user are passed by the shell to the operating system
which carries them out. The results are then passed back by the shell and
displayed on the user's display.
There are several
shells available. The user may select which one they wish to use.
shell prompt In UNIX a character
at the start of the command line which indicates that the shell is ready
to receive your commands. The character is usually a '%' (percent sign)
or a $ (dollar sign). It may be different on your system.
Shielding The protective
enclosure surrounding a transmission medium, designed to minimize electromagnetic
shielded cable Cable
that has a layer of shielded insulation to reduce EMI.
shortest-path routing Routing
that minimizes distance or path cost through application of some algorithm.
Short Haul Modem A
data set designed for use in communicating data up to distances of 25 miles
across private metallic circuits. Such devices permit speed of 192 kbps
or greater, and generally do not modulate the digital input signal. Also
called a line driver or limited
distance modem (LDM).
SIG (Special Interest
signal-to-noise ratio When
used in reference to Usenet activity,
`signal-to-noise ratio' describes the relation between amount of actual
information in a discussion, compared to their quantity. More often than
not, there's substantial activity in a newsgroup, but a very small number
of those articles actually contain anything useful. [Source: ZEN
Signaling The process
of sending a transmission signal over a physical medium for purposes of
signature The three
or four line message at the bottom of a piece of email or a Usenet article
which identifies the sender. Large signatures (over five lines) are generally
frowned upon. See also: Electronic Mail,
Usenet. [Source: RFC1392]
SIMD (Single Instruction,
SIMM (Single In-line Memory
Module). A small plug-in circuit board providing additional RAM
for a computer.
simplex transmission Data
transmission in only one direction.
single-mode fiber Fiber
with a relatively narrow diameter through which only one mode will propagate.
Such fiber is higher bandwidth than multimode fiber, but requires a light
source a narrow spectral width (for example, a LASER).
SIP (Società Idroelettrica
Piemontese). Original name of the Italian Telephone Company. See: Telecom
Also: (Single In-line Package)
SIPP (Single In-line Pin
sliding window flow control Method
of flow control in which a receiver gives transmitter permission to transmit
data until a window is full. When the window is full, the transmitter must
stop transmitting until the receiver advertises a larger window. TCP,
other transport protocols and several link-layer protocols use this method
of flow control.
SLIP (Serial Line IP)
A protocol used to run IP over serial lines, such as telephone circuits
or RS-232 cables, interconnecting
two systems. SLIP is defined in RFC
1055. See also: Point-to-Point Protocol.
SLiRP SLiRP is a free TCP/IP
program emulator over the CSLIP/SLIP/PPP link-level protocols which allows
a normal user with a shell account on a UNIX system to act like a real
(C)SLIP/PPP account. This means you can use programs like Netscape, Mosaic,
ftp etc. from your home machine with only a shell account. It is an excellent
freeware alternative to TIA. Check out
the SLiRP Home Page
for more information about SLiRP. To configure SLiRP on your Macintosh
slotted ring LAN
architecture based on a ring topology in which the ring is divided into
slots that circulate continuouslyots can be either empty or full, and transmissions
must start at the beginning of a slot.
slow switching Packet
processing performed by a CSC processor while operating at process level.
SMB (Server Message
Block). A file-system protocol used in LAN
Manager and similar NOSs to
package data and exchange information with other systems.
SMDS (Switched Multimegabit
Data Service). An emerging high-speed datagram-based public data network
service developed by Bellcore and expected to be widely used by telephone
companies as the basis for their data networks. See also: Metropolitan
Area Network. [Source: RFC1208]
SMI (Structure of Management
Information) The rules used to define the objects that can be accessed
via a network management protocol. This protocol is defined in STD
1155. See also: Management Information
Base. [Source: RFC1208]
SMP (Symmetric MultiProcessing).
SMPTE (Society of Motion
Picture & Television Engineers).
SMT (Station Management).
FDDI X3T9.5 specification that defines
how ring stations are managed.
SMTP (Simple Mail Transfer
Protocol). A protocol, defined in STD
821, used to transfer electronic mail between computers. It is a server
to server protocol, so other protocols are used to access the messages.
See also: Electronic Mail, Post
Office Protocol, RFC
822. [Source: RFC1392]
SNA (Systems Network Architecture).
A proprietary networking architecture used by IBM and IBM-compatible mainframe
computers. [Source: NNSC]
SNADS (SNA Distribution
Services). Along with Document Interchange Architecture (DIA) and Distributed
Data Management (DDM), one of three SNA transaction services architectures.
SNADS provides asynchronous distribution of information between end users.
snail mail A pejorative
term referring to the normal postal service.
SNAP (SubNetwork Access
Protocol). Internet protocol that operates between a network entity in
the subnetwork entity in the end system and specifies a standard method
of encapsulating IP datagrams and
ARP messages on IEEE
networks. The SNAP entity in the end system makes use of the services
of the subnetwork and performs three key functions: data transfer, connection
management and quality of service selection.
SNI (SNA Network Interconnection).
IBM gateway connecting multiple SNA networks.
SNI also stands for (Subscriver Network Interface) for SMDS-based
networks. It is the interface for SMDS-based networks. It is the interface
between customer promises equipment (CPE)
and an SMDS switch.
SNMP (Simple Network
Management Protocol). The Internet standard protocol, defined in STD
1157, developed to manage nodes on an IP network. It is currently possible
to manage wiring hubs, toasters, jukeboxes, etc. See also: Management
Information Base. [Source: RFC1392]
SNPA (SubNetwork Point
of Attachment). This is a data link address (such as an Ethernet
address, X.25 address, or Frame
Relay DLCI address). SNPA addresses
are used to configure a CLNS route for
socket Software structure
operating as a communications and point within a network device.
SOM (System Object Model).
An object-oriented programming tool for OS/2.
Optical NETwork). High-speed (up to 2.5 Gbps) synchronous network approved
as an international standard in 1988.
The RBOCs are likely to make SONET
popular as a transmission system underlying SMDS.
source address Address
of a sending network device.
source-route bridging Method
of bridging originated by IBM where the entire route to a destination is
predetermined, in real time, prior to the sending of data to the destination.
Contrast this with transparent bridging, wherein bridging occurs on a hop-by-hop
basis. Source-route bridging (sometimes abbreviated to SRB) is most popular
in Token Ring networks.
source-route translational Sometimes
referred to as SR/TLB, a method of bridging where source-route stations
can communicate with transparent bridge stations with the help of an intermediate
bridge that translates between the two bridge protocols.
source-route transparent bridging
Bridging scheme proposed by IBM that attempts to merge tp two
most prevalent bridging strategies (transparent and source-route bridging).
SRT, as it is sometimes referred to, employs both technologiess in one
device to satisfy the needs of all end nodes. No translation between the
bridging protocols is done, as compared to source-route translational bridging
Space In telecommunications,
the absence of a Signal Equivalent to a binary "0". A space is the opposite
of a mark ("1").
SPAG (Standards Promotion
and Application Group). A group of European OSI manufacturers which chooses
option subsets and publishes these in a "Guide to the Use of Standards"
SPAM (Stupid Persons'
AdvertiseMent). Unsolicited advertisments sent to a user
or newsgroup. The common response is to reply with a "no thanks" letter.
" If I wanted your products I could search on the Web and find them. No
more spam thanks, I am full.
SPAN (Space Physics
Analysis Network). A data comparison network serving NASA projects and
facilities, with extensions to Japan, Canada, and many European countries.
span Full duplex digital
transmission line between two digital facilities.
spanning tree A loop-free
subset of a network's topology.
spanning-tree algorithm An
algorithm, the original version of which was invented by Digital Equipment
Corporation, used to prevent bridging loops by creating a spanning tree.
The algorithm is now documented in the IEEE 802.1 specification, although
the Digital algorithm and the IEEE 802.1d algorithm are not the same, nor
are they compatible.
speed matching A feature
that provides sufficient buffering capability in a destination device to
allow a high-speed source to transmit data at its maximum rate, even if
the destination device is a lower-speed device.
split horizon updates A
routing technique in which information about routes is prevented from existing
router interfaces through which that information was received. Split horizon
updates are useful in preventing routing loops.
spooler An application
that manages requests or jobs submitted to it for execution. Spoolers process
the submitted requests in an orderly fashion from a queue. A print spooler
is perhaps the most common example of a spooler.
SQE (Signal Quality
Error). A transmission sent by a transceiver back to the controller to
let the controller known whether the collision circuity is functional.
Also called heartbeat.
See source-route bridging.
SQL (Structured Query
Language). The international standard language for defining and accessing
SRAM (Static RAM).
SRT See source-route
transparent bridging .
SR/TLB See source-route
SSCP (System Services
Control Point). Focal point within an SNA network for managing network
configuration, coordinating network operator and problem determination
requests, and providing directory sevices and other session services and
other session services for network end users.
SSCP-PU session Session
used by SNA to allow an SSCP to manage a node's resources through the PU.SSCPs
can send requests to, and receive replies from, individual nodes in order
to control the network configuration.
SSI (Small-Scale Integration).
SSL (Secure Sockets
Layer). A security protocol that provides communications privacy
over the Internet. The protocol allows client/server applications to communicate
in a way that is designed to prevent eavesdropping, tampering, or message
forgery. The latest version of the SSL protocol has been submitted to the
IETF and is available as an Internet
SS/SD (Single-Sided, Single-Density).
standard A commonly
used or officially specified set of rules or procedures. See also de facto
standard and the jure standard.
standard input In UNIX the
source of information for a command. This is assumed to be the keyboard
unless input is redirected
from a file or another command.
standard output In UNIX the
destination for information from a command. This is assumed to be the terminal
display unless ouput is redirected
to a file or another command.
standby monitor Device
in standby mode on a Token Ring network in case an active monitor becomes
inactive. See also active monitor and ring monitor.
StarLAN Another name
for IEEE 802.3 1Base5. A 1-Mbps
promulgated by AT&T.
Start bit In asynchronous
transfers, a new character is introduced by the start bit.
star topology LAN topology
in which end points on a network are connected to a common central switch
by point-to-point links.
start-stop transmission See
static route A route
that is manually entered into the routing table. Static routes take precedence
over routes chosen by all dynamic routing protocols.
statistical multiplexer Multiplexing
equipment that dynamically allocates trunk capacity only to active input
channels, allowing more devices to be connected than with a traditional
multiplexer. Also referred to as a statistical time division multiplexer
or a stat mux.
STD A subseries of RFCs that
specify Internet standards. The official list of Internet standards is
1. See also: For Your Information,
Request For Comments. [Source: RFC1392]
STM or STDM (Statistical
Multiplexer). A device connecting multiple channels to a single line by
dynamically allocating timeslots to the channels based on their activity.
Stop bit In asynchronous
transfer, very character is terminated by one or two stop bits wich show
where a character ends..
store and forward Message-switching
technique where messages are temporarily stored at intermediate points
between the source and destination until such time as network resources
(such as an unused link) are available for message forwarding.
STP (Shielded Twisted
Pairs). General term for cabling systems that are designed specifically
for data transmission and where the cables are shielded.
stream-oriented A type
of transport service that allows its client to send data in a continuous
stream. The transport service will guarantee that all data will be delivered
to the other end in the same order as sent and without duplicates. See
also: Transmission Control Protocol. [Source: MALAMUD]
basic transmission rate of 51.84 Mbps. [Source: ADSL
stub network A stub
network only carries packets to and from local hosts. Even if it has paths
to more than one other network, it does not carry traffic for other networks.
See also: backbone, transit
network. [Source: RFC1392]
STUN Serial Tunneling.
Cisco acronym for a router feature allowing two SDLC
- or HDLC-compliant devices to connect
to one another through an arbitrary multiprotocol topology (using Cisco
routers) rather than through a direct serial link. STUN provides configuration
flexibility for the network administrator.
subarea Portion of
a SNA network that consists of a subarea
node and any attached links and peripheral nodes.
subarea node An SNA
communication controller or host that handles complete network addresses.
subchannel In broadband
terminology, a frequency-based subdivision cretaing a separate communications
Subnet A portion of a
network, which may be a physically independent network segment, which shares
a network address with other portions of the network and is distinguished
by a subnet number. A subnet is to a network what a network is to an internet.
See also: internet, network.
Subnet Address The
subnet portion of an IP address. In a subnetted network, the host portion
of an IP address is split into a subnet portion and a host portion using
an address (subnet) mask. See also: address
mask, IP address, network
address, host address.
subnet mask A 32-bit
addresss mask used in IP to specify a particular subnet. See also : address
subnet number See:
subnetwork A collection
of OSI end systems and intermediate systems under the control of a single
administrative domain and utilizing a single network access protocol. Examples:
private X.25 networks, collection of bridged LANs.
Sub-rate Multiplexing In
the U.S., refers generally to time division multiplexing at data rates
less than 64 kbps. subvector
A data segment of a vector in an SNA message.A subvector consists
of a length field, a key that describes the subvector type, and subvector
summarize To encapsulate
a number of responses into one coherent, usable message. Often done on
controlled mailing lists or active newsgroups, to help reduce bandwidth.
[Source: ZEN ]
The Swedish University Network.
SuperJANET is the latest phase in the developement of JANET,
the UK educational and research network run by UKERNA.
It uses SMDS and ATM
to provide multi-service network facilities for many new applications including
supernet An aggregation
of IP network addresses advertised as a single classless network address.
For example, given four Class C IP networks: 220.127.116.11, 18.104.22.168, 22.214.171.124
and 126.96.36.199, each having the intrinsic network mask of 255.255.255.0;
one can advertise the address 188.8.131.52 with a subnet mask of 255.255.252.0.
See also: IP address, network
address, network mask, Classless
Inter-domain Routing. [Source: RFC1983]
Universities Research Association Network). Network connecting hosts in
12 southeastern states.
Dutch ISP for research and
education and other non-profit communities.
SVC (Switched Virtual
Circuit). A virtual circuit that can be dynamically established on demand.
Contrasted with PVC.
SVGA (Super Video Graphic
Commercial internet service provider in Sweden. Daughter company
of Tele2, one of the PNO in Sweden.
The Swiss Academic and Research network.
switch processor In
Cisco's hardware architecture, a bit-slice processor board that acts as
the administrator for all ciscoBus activities. Also called the CiscoBus
common timing between sender and receiver.
Synchronous transmission Transmission
in which data bits are sent at a fixed rate, with the transmitter and receiver
synchronized. Sinchronized transmission eliminates the need for start and
syntax Rules governing
the way in which characters and words must be put together to form a command
that can be recognised and acted upon by the Unix operating system.
system administrator A
person or persons with responsibility for managing the system(s) you are