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Glossary Section "S" ( Definitions )

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0-9 A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

SAA Systems Application Architecture ( Cisco )  or Service Assured Access ( RAD )

SAN Storage Area Networking

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.

SAP service advertising protocol An IPX protocol through which network resources such as servers become known to clients

SCADA Supervisory, Control And Data Acquisition

SCP Service Control Point computers that contain customer
and network information in databases.

SDH Synchronous Digital Hierarchy is an international standard for synchronous data transmission over fiber optic cables at a data rate of 155.52 Mbps, STM-1. The North American equivalent of SDH is SONET

SDLC Syncronous Data Link Control, a full or half-duplex bit oriented protocol. This is the most commonly used synchronous protocol 

SDN Software Defined Networking

SDSL Symemetrical Digital Subscriber Line

SDWAN Software Defined networking applied to the WAN

selector The identifier (octet string) used by an OSI entity to distinguish among multiple SAPs at which it provides services to the layer above.

search engine A program used as a tool  on the Internet to locate the information needed. Today, using the search engines  to locate multiple pages on a subject is frequently referred to as "surfing".

serving area Region surrounding a broadcasting station where signal strength is at or above a stated minimum. The geographic area handled by a telephone central office facility. Generally equivalent to a LATA.

Session Layer The OSI layer that provides means for dialogue control between end systems.

SET Secure Electronic Transactions. The SET specification has been developed to allow for secure credit card and off-line debit card (check card) transactions over the World-Wide Web.

SFP Small Form-factor Pluggable

SDH Synchronous Digital Hierarchy. The European standard for high-speed data communications over fiber-optic media. The transmission rates range from 155.52Mbps to 2.5Gbps. See SONET, OC-n.

SGML Standardized Generalized Markup Language. An international standard for the definition of system-independent, device-independent methods of representing text in electronic form.

SGMP Simple Gateway Management Protocol. The predecessor to SNMP.

Shadowing A form of replication in which well-defined units of information are copies to several DSAs.

SIP Session Initiation Protocol is a protocol developed by the IETF MMUSIC Working Group. It is a proposed standard for initiating, modifying, and terminating an multimedia sessions, instant messaging, video, VOIP and other services.

SIMM A Single In-line Memory Module is a memory chip with a 32-bit path. For higher data concentrations see DIMM

Single Mode Fiber An optical fibre which allows only one ray of light to propagate through it. Single Mode Fiber is thinner, more expensive, has higher capacity and can be used for longer distances compared to Multi Mode Fiber. Single Mode Fiber requires laser transmitters.

SIP Session Initiation Protocol is a signaling protocol used to create, manage and terminate sessions in an IP based network.

SLA Service Level Agreement

SLIP Serial Line IP. An Internet protocol used to run IP over serial lines such as telephone circuits or RS-232 cables interconnecting two systems. SLIP has now been replaced by PPP. See PPP.

SMDS Switched Multimegabit Data Service

SMI Structure of Management Information. The rules used to define the objects that can be accessed via a network management protocol.

SMT Station Management. The part of FDDI that manages stations on a ring.

SMIP Simple Mail Transfer Protocol. The Internet electronic mail protocol. Defined in RFC 821, with associated message format descriptions in RFC 822.

SNA Systems Network Architecture. IBM's proprietary network architecture.

SNMP Simple Network Management Protocol is a set of protocols for managing complex networks.  SNMP works by sending messages, called protocol data units (PDUs), to different parts of a network. SNMP-compliant devices, called agents, store data about themselves in Management Information Bases (MIBs) and return this data to the SNMP requesters. 

SNMPv2 SNMP version 2. The "second generation" SNMP.

SNMPv3 SNMP version 3. The "third generation" SNMP. Uses the best of two competing security models to form a single protocol standard.

socket A paring of an IP address and a port number. Also can be used to define a female gender connector.

SOHO Small Office, Home Office. A term used to describe networking solutions and access technologies for offices that aren't directly connected to large corporate networks.

SONET Synchronous Optical NETwork. SONET is an international standard for high-speed data communications over fiber-optic media. The transmission rates range from 51.84Mbps to 2.5Gbps.

SPAG Standards Promotion and Application Group which publishes the European "Guide to the Use of Standards" (GUS).

spam Term used to describe unsolicited e-mail or newsgroup posts, often in the form of commercial announcements. The act of sending a spam is called, naturally "spamming." It has become such a problem on the Internet that the IETF has formed a working group to design technical solutions for preventing spamming.

spanning tree A loop-free subset of the topology of a network.

SPCS Stored Program Controlled Switch. A digital switch that supports call control, routing, and supplementary services provision under software control. All ISDN switches are SPCSs.

SPID Service Profile Identifier

spoofing Spoofing reduces the required bandwidth by having devices, such as bridges or routers, answer for the remote devices. This causes the remote LAN to appear as if it is still connected to the LAN device even though it is not. The spoofing saves the WAN bandwidth, because no packet is ever sent out on the WAN.

SQL Structured Query Language. The international standard language for defining and accessing relational databases.

squelch Suppressing audio output noise which interferes with the desired signal audio. Generally done by excluding signals were the strengths are significantly lower than the primary signal.

SSL Secure Socket Layer. An encryption technology for the Web used to provide secure transactions such as the transmission of credit card numbers for electronic commerce

SSM Synchronization Status Messaging

SSP Service Switching Point local voice switches (usually class 5 switches).

ST is a common type of connector used on both multi-mode and single-mode fiber optic cable. The outer connecting collar is not threaded. It has two small slots for the locking lugs. The outer collar is turned approximately 1/3 turn to lock. 

STBC Space Time Block Coding is a technique for spreading a transmission signal over multiple antennas to improve reception.

STD A sub-series of RFCs that specify Internet standards. The official list of Internet standards is in STD1

STP  Signal Transfer Point packet switches that provide
access to SS7 network. Relay messages between SSPs.

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.

STS1 See OC-1

STS3 See OC-3

STS12 See OC-12

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.

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.

subnet address The subnet portion of an IP address. In a sub-netted network, the host portion of an IP address is split into a subnet portion and a host portion using an address (subnet) mask.

subnetwork A collection of OSI end systems and intermediate systems under the control of a single administrative domain and utilizing a single network access protocol. Examples: private X.25 networks, collection of bridged LANs.

Super-JANET The latest phase in the development of JANET, the UK educational and research network run by UKERNA. It uses SMDS and ATM to provide multi-service network facilities for many new applications including Multimedia Conferencing. See JANET.

supernet An aggregation of IP network addresses advertised as a single classless network address.

switch (as a networking term) A device that filters and forwards packets between LAN segments. Switches operate at the data link layer (layer 2) of the OSI Reference Model. The use of switches within a LAN reduce data collisions and improve performance. Both hubs and switches are used to connect LAN segments, typically within a building or group of buildings. The switch will help to avoid data collisions and improve performance particularly in larger LANs. Neither Switches or Hubs modify the data.

synchronous (1) The condition occurring when two events happen in a specific time relationship with each other, both under control of a master clock; (2) A method of data transmission requiring the transmission of timing pulses to keep the sender and receiver synchronized in their communication used to send blocks of information. Synchronous data transmission is used in high speed data circuits because there is less overhead than asynchronous transmission of characters which contain two extra bits per character to effect timing.

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