1、INTERNATIONAL TELECOMMUNICATION UNION)45G134 ) TELECOMMUNICATIONSTANDARDIZATION SECTOROF ITU).4%2!4%$G0G03%26)#%3G0G0$)4!,G0G0.%47/2+G0 )3$.G93%26)#%G0G0#!0!“),)4)%34%,%3%26)#%3G0G03500/24%$G0G0“9G0G0!.G0G0)3$. 6)$%/4%8)45G134G0G0RecommendationG0G0) (Extract from the “LUEG0“OOK)NOTES1 ITU-T Recommen
2、dation I.241.5 was published in Fascicle III.7 of the Blue Book. This file is an extract fromthe Blue Book. While the presentation and layout of the text might be slightly different from the Blue Book version, thecontents of the file are identical to the Blue Book version and copyright conditions re
3、main unchanged (see below).2 In this Recommendation, the expression “Administration” is used for conciseness to indicate both atelecommunication administration and a recognized operating agency. ITU 1988, 1993All rights reserved. No part of this publication may be reproduced or utilized in any form
4、or by any means, electronic ormechanical, including photocopying and microfilm, without permission in writing from the ITU.Fascicle III.7 - Rec. I.241.5 1Recommendation I.241.5Fascicle III.7 - Rec. I.241.5TELESERVICES SUPPORTED BY AN ISDN: VIDEOTEX(Melbourne, 1988)5 VideotexThe prose description for
5、 the Videotex service in ISDN is for further study and is intended to be based onRecommendation F.300.5.1 DefinitionThe Videotex service in the ISDN is an enhancement of the existing Videotex service with retrieval andmailbox functions for text (alpha) and graphic information.5.2 DescriptionFor furt
6、her study.5.3 ProceduresFor further study.5.4 Network capabilities for chargingThis Recommendation does not cover charging principles. Future Recommendations in the D-Series areexpected to contain that information.It shall be possible to charge the subscriber accurately for the service.5.5 Interwork
7、ing requirementsFor further study.5.6 Interaction with supplementary servicesFor further study.5.7 Attributes and values of attributes of the Videotex servicea) LOW LAYER ATTRIBUTESInformation transfer attributesUser to Videotex centre Videotex centre to Videotexcentre, external computers1. Informat
8、ion transfer mode: circuit (Note 1) circuit/packet2. Information transfer rate: 64 kbit/s further study3. Information transfer capability: unrestricted further study4. Structure: further study further study5. Establishment ofcommunication:demand demand/permanent6. Symmetry: bidirectional symmetric b
9、idirectional symmetric7. Communication configuration: point-to-point demand/permanentpoint-to-point, multipoint2 Fascicle III.7 - Rec. I.241.5Access attributes8. Access channel: B for user information (Note 2)D for signalling9. Access protocol9.1 Signalling access protocol layer 1: Rec. I.430/I.4319
10、2 Signalling access protocol layer 2: Rec. I.440/I.4419.3 Signalling access protocol layer 3: Rec. I.450/I.4519.4 Information access protocol layer 1: Rec. I.430/I.4319.5 Information access protocol layer 2: Rec. X.75 (SLP)9.6 Information access protocol layer 3: ISO 8208b) HIGH LAYER ATTRIBUTES10.
11、 Type of user information: Videotex11. Layer 4 protocol functions 12. Layer 5 protocol functions 13. Layer 6 protocol functions 13.1 Resolution pixels per inch (ppi) For further study13.2 Graphic mode 14. Layer 7 protocol functions c) GENERAL ATTRIBUTES: for further studyNote 1 - The use of packet-m
12、ode is for further study.Note 2 - The use of the D-channel for Videotex information is for further study.5.8 Recommended support of Videotex by an ISDNa) Overall support1: Ab) Variations of non-dominant attributes:1) Information transfer mode circuit user terminal-to-Videotex centre Avideotex centre
13、 to Videotex centre, external computer A packet videotex centre to Videotex centre, external computer A2) Establishment Symmetry Communication Support1of communication configuration_demand permanent bidirectional pt-pt E(Note) symmetricdemand permanent bidirectional multipoint A(Note) symmetric (Not
14、e)Note Between Videotex centres and to external computers.1The definition of E (essential) and A (additional) can be found in Recommendation I.240.Fascicle III.7 - Rec. I.241.5 33) AccessSignalling and OAM(Note 1)User informationSupportChannel and rate Protocols Channel and rate ProtocolsCircuit mod
15、eD(16) I.430, I.440, I.441,I.450, I.451(Note 2)B(64) I.430,X.75 (SLP),ISO 8208AD(64) I.431, I.440, I.441,I.450, I.451(Note 2)B(64) I.431,X.75 (SLP),ISO 8208APacket modeD(16) FS B(64) or D (16) FS FSD(64) FS B(64) FS FSVC in B(64) FS B(64) FS FSNote 1 - Definition of protocols for OAM is for further study.Note 2 - Demand services only. Others are for further study.5.9 Dynamic descriptionThe circuit mode dynamic description appears in Recommendation I.220.
