Q.931

What Does Q.931 Mean?

Q.931 is an Integrated Services Digital Network (ISDN) signal connection control protocol that is an International Telecommunication Union (ITU)-T Recommendation.

Techopedia Explains Q.931

Q.931 and TCP/IP work at different layers and share few features. Q.931 has reliable layers but does not provide retransmission or flow control. Q.931 frame elements are as follows:

Protocol discriminator (PD): Specifies connection signaling protocol.
Call reference value (CR): Addresses concurrent connections.
Message type (MT): Specifies three-message layer type (i.e., call setup, release and feature control) from Q.931 call control message set.
Information elements (IE): Specifies additional message details, that is, name, length and variable content field.

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Margaret Rouse

Technology Expert

Margaret is an award-winning technical writer and teacher known for her ability to explain complex technical subjects to a non-technical business audience. Over the past twenty years, her IT definitions have been published by Que in an encyclopedia of technology terms and cited in articles by the New York Times, Time Magazine, USA Today, ZDNet, PC Magazine, and Discovery Magazine. She joined Techopedia in 2011. Margaret's idea of a fun day is helping IT and business professionals learn to speak each other’s highly specialized languages.

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