- 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. [Source:
RFC1208]
- Scottish and Northern
Ireland JANET User Group (SNIJUG)
- The Scottish and
Northern Ireland JANET User Group (SNIJUG) presents
the views of the users on JANET and UKERNA services to
the JISC Committee on Networking through the JANET
National User Group. See also: JANET National User
Group.
- SDH
- See: Synchronous Digital
Hierarchy
- selector
- The identifier used by
an OSI entity to distinguish among multiple SAPs at
which it provides services to the layer above. See
port. [Source: RFC1208]
- Serial Line IP (SLIP)
- A protocol used to run
IP over serial lines, such as telephone circuits or
RS-232 cables, interconnecting two systems. SLIP is
defined in RFC
1055. See also: Point-to-Point Protocol. [Source:
RFC1392]
- SERJUG
- See: South East JANET
Regional User Group
- server
- A provider of resources
(e.g., file servers and name servers). See also:
client, Domain Name System, Network File System.
[Source: RFC1392]
- Service Level
Agreement
- A contractual agreement
between a service provider and a service user about
the level of performance of the service, and indeed
the provider. An example is the SLA between JISC and
UKERNA for the JANET service.
- Session Layer
- The OSI layer that
provides means for dialogue control between end
systems. [Source: RFC1208]
- SGMP
- Simple Gateway
Management Protocol. The predecessor to SNMP. See SNMP.
[Source: RFC1208]
- SGML
- See: Standardized
Generalized Markup Language
- SIG
- Special Interest Group
[Source: RFC1392]
- 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.
- 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]
- Simple Mail Transfer
Protocol (SMTP)
- A protocol, defined in RFC
821, used to transfer electronic mail between
computers, with extensions specified in many other
RFCs. It is a server to server protocol, so other
protocols are used to access the messages. See also:
Electronic Mail, Post Office Protocol, RFC 822.
[Source: RFC1392]
- Simple Network
Management Protocol (SNMP)
- The Internet standard
protocol developed to manage nodes on an IP network.
The first version is defined in RFC
1157 (STD 15). SNMPv2 (version 2) is defined in
too many RFCs to list. It is currently possible to
manage wiring hubs, toasters, jukeboxes, etc. See
also: Management Information Base. [Source: RFC1392]
- Simple Object Access
Protocol (SOAP)
- A lightweight messaging
framework designed for exchange of structured
information in a distributed, decentralised
environment, of which the provision of services over
the World Wide Web is an example. SOAP is issued by
the World Wide Web Consortium (W3C) XML Protocol
Working Group.
- SLA
- See: Service Level
Agreement
- SLIP
- See: Serial Line IP
- SMDS
- See: Switched
Multimegabit Data Service
- SMI
- See: Structure of
Management Information
- SMTP
- See: Simple Mail
Transfer Protocol
- SNA
- See: Systems Network
Architecture
- snail mail
- A pejorative term
referring to the U.S. postal service.
- SNIJUG
- See: Scottish and
Northern Ireland JANET User Group
- SNMP
- See: Simple Network
Management Protocol
- SOA
- See: Start of Authority
Record
- SOA
- See: Start of Authority
Record
- SONET
- See: Synchronous Optical
NETwork
- South East JANET
Regional User Group (SERJUG)
- The South East JANET
Regional User Group (SERJUG) presents the views of the
users on JANET and UKERNA services to the JISC
Committee on Networking through the JANET National
User Group. See also: JANET National User Group.
- South West JANET
Regional User Group (SWJRUG)
- The South West JANET
Regional User Group (SWJRUG) presents the views of the
users on JANET and UKERNA services to the JISC
Committee on Networking through the JANET National
User Group. See also: JANET National User Group.
- SPAG (1)
- Standards Promotion and
Application Group. A group of European OSI
manufacturers which chooses option subsets and
publishes these in a "Guide to the Use of
Standards" (GUS). [Source: RFC1208]
- SPAG (2)
- Service Performance
Advisory group, formerly MSC, a subgroup of JISC,
responsible for development and trend analysis of
JANET.
- spam
- send an email message or
news message to large numbers of email distribution
lists or Usenet newsgroups, to the annoyance of most
recipients, and contrary to Netiquette.
- Spread Spectrum
- Transmission of a signal
using a carrier whose frequency spectrum varies over a
wide range in a pseudo random manner. Detection and
interception are difficult as transmissions appear
similar to background noise. Reception is done by
cross correlation of the wide band signal with a
replica of the spectrum of the sender, synchronised
between sender and receiver.
The two main methods
are Frequency Hopping (FH or FHSS) and Direct Sequence
(DS or DSSS). In FH the output frequencies hop around
the desired range according to a pseudo random
sequence of numbers fed into the frequency synthesiser.
In DS a narrow band signal is spread into a wideband
signal using a pseudo random chipping code sequence (a
rather higher data rate bit sequence) which determines
the spreading ratio. This is also known as Phase Shift
Keying or phase modulation. For 802.11b Wireless Local
Area Networks the modulation scheme is known as
Complementary Code Keying (CCK) and for 802.11a it is
known as Orthogonal Frequency Division Multiplexing (OFDM).
The signal is despread at the receiver with the same
code sequence, using the redundant information in the
code sequence to aid error correction in case of
interference. See also: 802.11, Wireless Local Area
Network.
- SQL
- Structured Query
Language. The international standard language for
defining and accessing relational databases. [Source:
RFC1208]
- Squid
- A Web proxy cache
package.
- SSH
- Secure Shell, a package
for eliciting secure (i.e. encrypted) interactive
connections across a public network such as the
Internet.
- SSL
- Secure Socket Layer
protocol, a method for eliciting secure (i.e.
encrypted) connections (e.g. to web services) across a
public network such as the Internet. Now extended as
Transport Layer Security (TLS).
- STAN
- JANET Spam-relay Tester
And Notification system, for checking electronic mail
servers for weaknesses which might promote spam.
- Standardized
Generalized Markup Language (SGML)
- An international
standard for the definition of system- independent,
device-independent methods of representing text in
electronic form. Different applications can be
developed using Document Type Definitions (DTDs) e.g.
HTML. See also: Hypertext Markup Language. [Source:
RFC1983]
- Start of Authority
Record (SOA Record)
- A DNS resource record
type indicating which host is authorative for a
particular domain. See also: Domain Name System.
- STD
- A subseries of RFCs that
specify Internet standards. The official list of
Internet standards is in STD 1. See also: For Your
Information, Request For Comments. [Source: RFC1392]
- stream-oriented
- A type of transport
service that allows its client to send data in a
continuous stream. The transport service will
guarantee that all data will be delivered to the other
end in the same order as sent and without duplicates.
See also: Transmission Control Protocol. [Source:
MALAMUD]
- Structure of
Management Information (SMI)
- The rules used to define
the objects that can be accessed via a network
management protocol. This protocol is defined in STD
16, RFC
1155. See also: Management Information Base.
[Source: RFC1208]
- stub network
- A stub network only
carries packets to and from local hosts. Even if it
has paths to more than one other network, it does not
carry traffic for other networks. See also: backbone,
transit network. [Source: RFC1392]
- subnet
- A portion of a network,
which may be a physically independent network segment,
which shares a network address with other portions of
the network and is distinguished by a subnet number. A
subnet is to a network what a network is to an
internet. See also: internet, network. [Source: FYI4]
- subnet address
- The subnet portion of an
IP address. In a subnetted network, the host portion
of an IP address is split into a subnet portion and a
host portion using an address (subnet) mask. See also:
address mask, IP address, network address, host
address. [Source: RFC1392]
- subnet mask
- See: address mask
- subnet number
- See: subnet address
- 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. [Source:
RFC1208]
- SUfi
- Scottish University for
industry.
- 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.
- SuperJANET
- SuperJANET 4 is a very
high performance backbone network based on optical
fibre technology, offering up to 2.5 Gigabits/sec
transmission rates in April 2001. This new network is
needed to support advanced applications requiring a
mixture of voice, data, image and video
communications. The network is designed to use the
most up-to-date communications technology -
synchronous digital hierarchy (SDH) access - within
the backbone between Core Points of Presence (C-PoPs)
and to Backbone Access Routers (BARs) at the boundary
of each regional MAN. A testbed network using DWDM is
also in use.
- SWERN
- South West England
Regional Network.
- Switched Multimegabit
Data Service (SMDS)
- An emerging high-speed
datagram-based public data network service developed
by Bellcore and expected to be widely used by
telephone companies as the basis for their data
networks. See also: Metropolitan Area Network.
[Source: RFC1208]
- SWJRUG
- See: South West JANET
Regional User Group
- synchronous
- Data communications in
which transmissions are sent at a fixed rate, with the
sending and receiving devices synchronized.
- Synchronous Digital
Hierarchy (SDH)
- The European standard
for high-speed data communications over fiber-optic
media. The transmission rates range from 155.52Mbps to
2.5Gbps. [Source: RFC1983]
- Synchronous Optical
NETwork (SONET)
- SONET is an
international standard for high-speed data
communications over fiber-optic media. The
transmission rates range from 51.84Mbps to 2.5Gbps.
[Source: RFC1983]
- Systems Network
Architecture (SNA)
- A proprietary networking
architecture used by IBM and IBM- compatible mainframe
computers. [Source: NNSC]
Return
to TOP
|
