Glossary (S)
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SCCP (SKINNY CLIENT CONTROL PROTOCOL)
A proprietary terminal control protocol, originally developed by Selsius Corporation, now owned and defined by Cisco Systems, Inc. as a messaging set between a skinny client and the Cisco CallManager.
SCTP (STREAM CONTROL TRANSMISSION PROTOCOL)
A Transport layer protocol defined in 2000 by the IETF Signaling Transport (SIGTRAN) working group, equivalent in a sense to TCP or UDP. Provides some similar services as TCP, ensuring reliable, in-sequence transport of messages with congestion control.
SDP (SESSION DESCRIPTION PROTOCOL)
A format for describing streaming media initialization parameters intended for describing multimedia sessions for the purposes of session announcement, session invitation, and other forms of multimedia session initiation.
SDU (SERVICE DATA UNIT)
A set of data that is sent by a user of services of a given layer, and is transmitted to a peer service user semantically unchanged. The SDU is the data that a certain layer will pass to the layer below.
SERIAL INTERFACE
A channel that transfers digital data in a serial fashion, one bit after the other over one wire or fiber. The serial port on a PC is a serial interface that is used to attach modems and scanners. Serial interfaces may have multiple lines, but only one is used
for data.
See also V.35 and X.21
SERVICE PREFIX
The prefix identifies the service and can usually be a numeric code, an alphanumeric string, a name, or phone number.
SERVICES
A service is a function that is supported by a subset of endpoints in a zone. Access a service by dialing a prefix attached to the name or phone number. Services allow you to dynamically add more resources, such as a Gateway, into the system.
SGW (SIGNALING GATEWAY)
A network component solely responsible for translating signaling messages between one medium (usually IP) and another (PSTN). SGW typically handles SS7 protocol conversion to IP telephony messages.
SIF
A resolution equivalent to QVGA — 320*240. This resolution is common in security cameras and countries where NTSC is used.
SIGCOMP
Signaling compression between UE and PCSCF as defined in RFC
3320 and related standards.
SIGTRAN
The name given to an IETF working group that produced specifications for a family of protocols that provide reliable datagram service and user layer adaptations for SS7 and ISDN communications protocols.
SILENCE SUPPRESSION
Silence information within the audio stream can consume LAN bandwidth and burden voice processing. Using compression techniques, Silence Suppression can greatly reduce the wasted bandwidth in a multipoint conference and on congested networks.
SIMPLE (SESSION INITIATION PROTOCOL (SIP) FOR INSTANT MESSAGING AND PRESENCE LEVERAGING EXTENSIONS)
An application of the SIP protocol for server-to-server and
client-to-server interoperability in Instant Messaging. SIMPLE is
a step in bringing standardization to Instant Messaging.
SINGLE SIGN-ON
Ability for end users to move easily among services without having to repeatedly identify themselves with a new password.
SIP (SESSION INITIATION PROTOCOL)
An IP telephony signaling protocol developed by the IETF. SIP is
a text-based protocol that is suitable for integrated voice-data applications. SIP is designed for video, voice and data transmission and uses fewer resources and is considerably less complex than H.323.
SIP-CX (SIP CONFERENCING EXTENSION)
A Microsoft proprietary protocol used to control conferencing systems. This is being replaced by CCCP.
SIP SERVER
A SIP network element that receives SIP messages from other
SIP network elements and forwards the messages or provides SIP
responses.
SKINNY
See SCCP
SLAVE
The side in communications which responds to session commands. The “master” is the other side that initiates and controls the session.
SMARTPHONE
Any electronic handheld device that integrates the functionality of a mobile phone, personal digital assistant (PDA) or other information appliance. A key feature of a smartphone is that additional applications can be installed on the device, developed by the device manufacturer operator or by any other third-party software developer.
SMIL (SYNCHRONIZED MULTIMEDIA INTEGRATION LANGUAGE)
SMIL is a W3C recommendation for describing multimedia presentations using XML. It defines timing markup, layout markup, animations, visual transitions, media embedding and more.
SNMP (SIMPLE NETWORK MANAGEMENT PROTOCOL)
A widely used network monitoring and control protocol.
SOAP (SIMPLE OBJECT ACCESS PROTOCOL)
A protocol for exchanging XML-based messages over a computer network, normally using HTTP. SOAP forms the foundation layer of the Web services stack, providing a basic messaging framework that more abstract layers can build on.
SRTP (SECURE REAL-TIME TRANSPORT PROTOCOL)
Defines a profile of RTP (Real-time Transport Protocol), intended to provide encryption, message authentication and integrity, and replay protection to the RTP data in both unicast and multicast applications.
SQCIF (SUB QUARTER COMMON INTERMEDIATE FORMAT)
A video format usually used to refer to video with dimensions of 88 x 72 pixels.
SS7 (SIGNALING SYSTEM 7)
A signaling protocol that carries telephony signaling information between central office switching systems.
STB (SET-TOP-BOX)
A device used in the TV industry to access the CableTV network.
STREAMING
A method of delivering multimedia content in one direction over
IP networks. The content can be stored or live.
STUN (SIMPLE TRAVERSAL OF UNDERNEATH NATS)
A network protocol allowing clients behind NAT (or multiple NATs) to find out its public address, the type of NAT it is behind and the internet side port associated by the NAT with a particular local port. This information is used to set up communication between two hosts that are both behind NAT routers.
SUB-ADDRESSING
Sub-addressing is a one-stage DID dialing mechanism in which a phone sends two numbers. One number is for routing on the circuit-switched network. The other number is forwarded to the Gateway inside a Q.931 Sub-addressing Information Element for IP address resolution by Gatekeeper/SIP Server.
SUB-CONFERENCE
Audio sub-conferences to which selected participants in an existing conference can be temporarily diverted by the MCU. When the sub-conference is over, the participants return to the main conference.
SUBNET
A subnet is a portion of an IP network defined by a subnet mask. Devices on the same subnet have the same subnet mask.
SUPPLEMENTARY SERVICES
The ITU-T H.450 Recommendation comprises a number of separate Recommendations for implementing Supplementary Services of the H.450.x series.