Glossary Section "S" ( Definitions )
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.
SCADA – Supervisory, Control And Data Acquisition
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
SDN Software Defined Networking
SDSL Symemetrical Digital Subscriber Line
SDWAN Software Defined networking applied to the WAN
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.
SFP Small Form-factor Pluggable
SGML Standardized Generalized Markup Language. An international standard for the definition of system-independent, device-independent methods of representing text in electronic form.
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.
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.
SLA Service Level Agreement
SMDS Switched Multimegabit Data Service
SMT Station Management. The part of FDDI that manages stations on a ring.
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.
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.
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.
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.
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.
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.
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.
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.