INTERNATIONAL TELECOMMUNICATION UNION

ITU-T Q.931

TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU

DIGITAL SUBSCRIBER SIGNALLING SYSTEM No. 1

NETWORK LAYER

DIGITAL SUBSCRIBER SIGNALLING SYSTEM No. 1 (DSS 1) - ISDN
USER-NETWORK INTERFACE LAYER 3

SPECIFICATION FOR BASIC CALL CONTROL

ITU-T Recommendation Q.931
(Previously "CCITT Recommendation")

FOREWORD

The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of the International Telecommunication Union. The ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis.
The World Telecommunication Standardization Conference (WTSC), which meets every four years, established the topics for study by the ITU-T Study Groups which, in their turn, produce Recommendations on these topics.
ITU-T Recommendation Q.931 was revised by the ITU-T Study Group XI (1988-1993) and was approved by the WTSC (Helsinki, March 1-12, 1993).
NOTES
 
1. As a consequence of a reform process within the International Telecommunication Union (ITU), the CCITT ceased to exist as of 28 February 1993. In its place, the ITU Telecommunication Standardization Sector (ITU-T) was created as of 1 March 1993. Similarly, in this reform process, the CCIR and the IFRB have been replaced by the Radiocommunication Sector.
In order not to delay publication of this Recommendation, no change has been made in the text to references containing the acronyms "CCITT, CCIR or IFRB" or their associated entities such as Plenary Assembly, Secretariat, etc. Future editions of this Recommendation will contain the proper terminology related to the new ITU structure.
2. In this Recommendation, the expression "Administration" is used for conciseness to indicate both a telecommunication administration and a recognized operating agency.
 
ITU 1994
 
All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the ITU.



ITU-T Q.931

TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU
(05/98)


Amendment 1: Extensions for the support of digital multiplexing equipment

(Summary This amendment contains the modifications to ITU-T Rec. Q.931 (05/98) in order to accommodate the needs of DME signalling and to correct an editorial error in the coding of the Bearer capability information element. Appendix III is added to provide typical DME control procedures. NOTE – This amendment takes into account Erratum 1 to Q.931 (05/1998) which corrects the editorial error for the coding of octet 5d (bit 1) of the V.32 Bearer capability information element in Table 4-6/Q.931. )

Erratum 1 (02/2003)