1、 - ITU-T RECMN*T.LOb 93 LIB6259L 0593750 265 INTERNATIONAL TELECOMMUNICATION UNION ITU-T TELECOMMUNICATION STAN DARD IZATION SECTOR OF ITU T.106 (03193) TELEMATIC SERVICES TERMINAL EQUIPMENTS AND PROTOCOLS FOR TELEMATIC SERVICES FRAMEWORK OF VIDEOTEX TERMINAL PROTOCOLS ITU-T Recommendation T.106 (Pr
2、eviously “CCITT Recommendation”) _ - ITU-T RECMN*T.LOb 93 4b259L 0593751 LTL m FOREWORD The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of the International Telecom- munication Union. The ITU-T is responsible for studying technical, operating and tariff questions and is
3、suing 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
4、 these topics. ITU-T Recommendation T.106 was prepared by the ITU-T Study Group VIII (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 CCIT ceased to exist as of 28 February
5、1993. In its place, the ITU Telecommunication Standardization Sector (ITU-T) was created as of i 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 Similarly, in this reform process, the CCIR and the IFRB have been replaced by the Radiocommunication Sector.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
6、 in the text to references containing the acronyms “CCIZT, 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 telecommunication administration and a reco
7、gnized operating agency. In this Recommendation, the expression “Administration” is used for conciseness to indicate both a O 1994 Ail 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 microfil
8、m, without permission in writing from the ITU. 4 5 ITU-T RECMN*T-LOb 93 4862593 0593752 038 I CONTENTS Scope Normative references . Overall structure of protocols in various environments . 3.1 Data Syntaxes Applicable to Videotex Terminals 3.2 ISDN circuit mode 3.3 ISDN packet mode 3.4 PSTN packet m
9、ode . Syntax-based Videotex Application layer protocol Existing protocols of SPTN circuit switched mode . Recommendation T.106 (03/93) Page 1 1 2 3 3 3 3 3 3 i ITU-T RECMNUT.106 93 H 4662.591 0593753 T74 R Recommendation T.106 FRAMEWORK OF VIDEOTEX TERMINAL PROTOCOLS (Helsinki, 1993) 1 Scope Videote
10、x is a public access information system which allows for the connection of a variety of terminal equipment to databases of information (servers) or to other terminals over widely available public telecommunications facilities. initially terminals were connected to information servers over the conven
11、tional public switched telephone network (PSTN). This was accomplished using low cost modems: typically at 1200/75 or 1200/1200 bits/s. With the introduction of ISDN and improved modem facilities a number of other optional configurations are becoming viable for the connection of videotex terminals t
12、o server systems. These include higher speed conventional modems at 2400 or 4800 bits/s, much higher speed modems such as 9600 bit/s (see Recommendations V.29 lo and V.32 li) or I4 400 bit/s (see Recommendation V. 17 9) and ISDN connections using packet mode on a B or D channel and circuit switched
13、inode. A number of videotex communications configurations are possible using these new communications facilities. This Recommendation describes the method by which these facilities shall be used in videotex. This Recommendation describes the application layer and lower layer protocols which shall be
14、 used for terminal to videotex systems operating over various types of networks. This includes: - - - - ISDN 64 kilobit/s circuit mode; ISDN 64 kilobit/s packet mode; ISDN D channel packet mode; PSTN packet mode operation using V-Series modems. In addition the existing PSTN based videotex services a
15、re identified, which primarily make use of relatively low speed modems over the PSTN or equivalent networks. This Recommendation also identifies. the data syntaxes used in the various configurations within the various regions of the world, together with the common data syntaxes for audio and photogr
16、aphic information. The relationships between the various Recommendations applicable to videotex are defined. Normative references CCITT Recommendation T. 1 O 1, International intenuorking for videotex services. CCITT Recommendation T. 102, Syntax-Based End-to-end Protocols for the Circuit mode ISDN.
17、 CCIT Recommendation T. 103, Syntax-Based End-to-end Protocols using the Packet Mode ISDN. CCIT Recommendation T. 104, Packet Mode access for Syntax-Based Videotex via PSTN, CCITT Recommendation T. 105, Syntax-based videotex application layer protocol. CCITT Recommendation F.300, Videotex service. I
18、S0 2022, Information Processing - IS0 7-bit and - via a Packet Assembler Disassembler (PAD): - via a Videotex Access Point (VAP); or - via a Videotex Service Center (VSC) which may also act as a videotex host. All of these configurations are currently in use. In all of the identified configurations
19、listed above there exists an access function which is located either in the host or in the VAP or in the VSC. With the development of new types of networks and progress m modem technology it is necessary to define the protocol between the terminal and the access function. For this reason a series of
20、 Recommendations have been developed addressing the protocol aspects between the terminal and the access function of the videotex service. Recommendations have been defined identifying the access protocols for three different types of networks. The relationships between these standards, including th
21、e videotex syntax Recommendation are illustrated in Figure 1. T. 1 O1 Videotex Data syntaxes: Annex B (DS i) Annex C (DS il) AM= D (DS ill) Annex E (Audio) Annex F (Photo) T TOBO850091 Ido 1 FIGURE 1l.106 Relationships between videatex Recommendations 2 Recommendation T.106 (03/93) ITU-T RECMN*T.LOb
22、 73 D 4862591 0593755 847 3.1 The representation of application data elements in syntax based videotex systems is accomplished by the use of a number of defined data syntaxes. Videotex services have been implemented in different countrieshegions making use of different data syntaxes referred as Data
23、 Syntax I, Data Syntax II and Data Syntax III, which have an equal status. These data syntaxes are described in Annexes BiT.101, CiT.101 and D/T.IOl i, respectively. Any of these data syntaxes may be used with the protocols given below (see 3.2 to 3.4). In combination with any of these three base da
24、ta syntaxes, two common enhancements are defined addressing audio and photographic capabilities (see Annexes E. 101 and F/T.lOl i, respectively). The Terminal Facility Identifier (TFI), defining the mechanism for allowing a videotex service to recognize the possibilities of a terminal, is described
25、in clause 9.101 i. The switching mechanism between the data syntaxes is based on IS0 2022 7 and ISOAEC 9281 8 as described in clause 9l.101 i. The ESC 2/5 F mechanism to introduce a complete coding environment may be used to select the base data syntaxes (DS I, DS II, DS III). The ISOAEC 9281 pictur
26、e coding environment switching technique based on ESC 7/0 CMI LI is used to establish the common audio and photo extensions. Data Syntaxes Applicable to Videotex Terminais 3.2 ISDN circuit mode Recommendation T.102 2 describes the lower layers (1-3) applicable to ISDN circuit mode of operation. It d
27、escribes the additional aspects of the End-to-end protocol for ISDN circuit mode, making reference to Recommendation T. 105 5 for the relevant common aspects of the End-to-end protocol. 3.3 ISDN packet mode Recommendation T.103 3 describes the lower layers (1-3) for ISDN packet mode operation on the
28、 B channel and the D channel. It also describes the additional aspects of the End-to-end protocol applicable to ISDN packet mode, making reference to Recommendation T.105 5 for the relevant common aspects of the End-to-end protocol. 3.4 PSTN packet mode Recommendation T.104 4 describes the lower lay
29、ers for packet mode operation on the PSTN. It also describes the additional aspects of the End-to-end, protocols operation, making references to Recommendation T. 105 5 for the relevant common aspects of the End-to-end protocol. 4 Recommendation T. 105 5 describes the application layer protocol comm
30、on to all Syntax based Videotex Recommendations. This Recommendation consists of the description of service. protocol and coding applicable to Syntax-based Videotex. Syntax-based Videotex Application layer protocol 5 A number of different application and lower layer protocols are in use throughout t
31、he world. These services are primarily regionally or nationally defined. In these protocols both 7 and 8-bit channels are used as well as a number of different V-Series modems. Existing protocols of SPTN circuit switched mode These existing base videotex systems are in wide use. In order to introduc
32、e functionalities in a compatible manner, PSTN based systems may be upgraded using higher speed modems without modifying the lower layers already in use. When introducing enhancements to the existing system (e.g. the use of higher speed modems), the lower layer and application layer protocols used are those defined in the existing services. Recommendation T.106 (0393) 3 TTU-T F?ECMN*T-LOb 93 48b12573 0573756 783 Printed in Switzerland Geneva, 1994
