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(SIP for Instant Messaging and Presence Leveraging Extensions) Enhancements that add instant messaging and presence to the SIP protocol. Developed by the SIMPLE working group of the IETF, SIMPLE adds buddy list subscriptions and notifications and instant messaging commands.

SIMPLE has two modes. Session mode, which is the more efficient mode, sets up the call and provides a raft of features including conferencing. Page mode uses no call setup and is more like a short messaging service for delivering one-shot messages and announcements.

The IETF's Instant Messaging and Presence Protocol (IMPP) working group, from which the SIMPLE group was split off, focuses on helping people build gateways to SIMPLE from other IM systems. In 2001, AOL said it would support SIMPLE, but subsequently abandoned its plans. See SIP.


(1) See system in package, single in-line package and System Integrity Protection.

(2) (Software Isolated Process) See singularity.

(3) (SMDS Interface Protocol) See SMDS.

(4) (Software Integration Platform) A common format and interface for geographic data in the petroleum industry.

(5) (Session Initiation Protocol) An IP telephony signaling protocol that is widely used to start and terminate voice calls over the Internet (see VoIP). Supporting two-way and multi-party calls, SIP can be used for any real-time media transmission over an IP network, including video calling and conferencing. It is also used for instant messaging (see SIMPLE) and multiplayer gaming.

SIP is a text-based application protocol that supports integrated voice and data such as click-to-chat on a website. Less complex and more efficient than the ITU's telephony protocol (see H.323), SIP addresses are like email; for example:

SIP Alphabet Soup
Based on HTTP and MIME, SIP relies on the session description protocol (SDP) for session description and the Real Time Transport Protocol (RTP) for transport. Windows XP was the first version of Windows to natively support SIP for PC-based phones, and all modern PBXs handle SIP trunks. See HTTP, MIME, RIP, SDP, SIP provider, SIP ALG and SIP proxy.

Personal Use Only

Before/After Your Search Term
SIM lockSimple File Sharing
SIM Not ProvisionedSimple Mail Interface
SimbionSimple Mail Transfer Protocol
SimCitySimple Network Management Protocol
SIMDSimple Object Access Protocol
SIMM convertersimplified English
SIMOSimplified Technical English
SIMOXSimply Interactive PC

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