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- The drawings contained in this Recommendation have been done in Autocad
- Recommendation T.101
- INTERNATIONAL INTERWORKING FOR VIDEOTEX SERVICES
- (Malaga-Torremolinos, 1984; amended at Melbourne, 1988)
- CONTENTS
- Preamble
- 1 Purpose and scope of the Recommendation
- 2 Interworking between Videotex services - General
- 3 International interworking of Videotex service
- 4 International interworking between gateways
- 5 International interworking between a terminal and a host
- 6 Content architecture class attributes
- 7 Content portion attributes
- 8 Formal definition of Videotex dependent data type
- Note - Annexes B, C and D will not be published in Fascicle VII.5 (T-Series
- Recommendations) but will be issued as a separate publication. Annex A -
- Interworking data syntax (IDS) described in ASN.1 (Recommendation X.208)
- Annex B - Data syntax I1)
- Annex C - Data syntax II1)
- Annex D - Data syntax III1)
- Preamble
- The CCITT,
- considering
- (a) that Videotex services have been implemented in different
- countries/regions using different data syntaxes referred to as data syntax I,
- data syntax II and data syntax III, which have an equal status;
- (b) that the CCIR is studying standards for broadcast Teletext services for
- general reception and has expressed a view that it is desirable that terminal
- equipment compatibility should exist between broadcast Teletext systems for
- general reception and public network-based data base systems;
- (c) that different countries/regions are entitled to use their existing
- systems;
- (d) that interworking between Videotex services in different countries may
- require transcoding and/or conversion;
- (e) that the interworking between Videotex services may be provided by
- using different types of networks such as the public switched telephone network
- (PSTN), packet switched public data network (PSPDN), circuit switched public data
- network (CSPDN), integrated services digital network (ISDN), etc.;
- (f) that Videotex interworking protocols should offer a large degree of
- compatibility with protocols used in other telematic services,
- recommends
- that the following technical provisions be applied for international
- interworking for Videotex services.
- 1 Purpose and scope of the Recommendation
- 1.1 Purpose
- The purpose of this Recommendation is:
- a) to facilitate the interworking of different Videotex services;
- b) to identify parameters needed to communicate with Videotex terminals;
- c) to provide technical recommendations desirable for potential
- interworking of other telematic services with Videotex services.
- 1.2 Scope
- 1.2.1 This Recommendation describes the characteristics of coded information
- that is exchanged between countries participating in the international
- interactive Videotex service.
- 1.2.2 Videotex systems are text communication systems having in addition the
- capability of a given level of pictorial representation and a repertoire of
- display attributes. The text and the pictures obtained are intended to be
- displayed using the current television (TV) raster standards of the different
- countries.
- 1.2.3 Different data syntaxes are offered as a choice for the Administrations to
- implement their national services. Substantial degrees of compatibility exist
- between these options, but some transcoding and/or conversion may be necessary to
- facilitate interworking.
-
- 1) Note - Annexes B, C and D will not be published in Fascicle VII.5 (T-Series
- Recommendations) but will be issued as a separate publication.
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- Fascicle VII.5 - Rec. T.100 PAGE1
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- 1.2.4 For the purpose of the international service, different data syntaxes have
- been identified:
- a) interworking data syntax;
- b) data syntax I;
- c) data syntax II;
- d) data syntax III;
- e) other syntaxes are for further study.
- 2 Interworking between Videotex services - General
- 2.1 It is the possibility of Administrations to decide in which network(s) the
- Videotex service(s) are to be provided.
- 2.2 Serveral possibilities are considered below:
- 2.2.1 Videotex service operated on the PSTN; the communication between a
- Videotex terminal and a Videotex host computer is established over the PSTN.
- 2.2.2 Videotex service operated on the PSTN and a public data network (PDN)
- (generally a PSPDN); the communication between a Videotex terminal connected to
- the PSTN and a Videotex host computer connected to a PDN is established via a
- Videotex access prior or a Videotex service center interfacing between both
- networks.
- 2.2.3 Other possibilities (CSPDN, ISDN, etc.) could also be considered.
- 2.3 International interworking between Videotex services via gateways and
- connected to any network (PSTN, PSPDN, CSPDN, ISDN, etc.) may be possible. Such
- interworking allows a Videotex terminal pertaining to a Videotex service to
- access a Videotex host computer pertaining to another Videotex service.
- International interworking between Videotex terminal in one country and a
- Videotex host in another country may also be possible. All international data
- exchange should comply with the specifications contained in this Recommendation.
- (See Recommendation F.300 for the service description).
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- 3 International interworking of Videotex service
- 3.1 Videotex interworking allows a Videotex terminal in a given country to
- interact in real time with Videotex application located in a different country.
- 3.2 International interworking between Videotex services should use those
- functions that are defined in the data syntaxes implemented by the
- Administrations concerned: data syntaxes I, II and III defined in Annexes.
- 3.3 International interworking configurations
- The various configurations for international interworking are defined in
- Recommendation F.300. The two major classes of interworking are defined below.
- 3.3.1 Gateway to gateway interworking
- This class of interworking involves communication between gateways located
- in each country and where all the data handling processes involved by the
- interworking are performed. The protocols and data syntaxes for this class of
- interworking are specified in S 4.
- 3.3.2 Terminal to host interworking
- This class of interworking involves communication between a terminal and a
- host located in different countries, either directly or through a conversion unit
- situated in the country where the terminal is located. Several cases have been
- identified. The protocols and data syntaxes for the various cases of this class
- of interworking are specified in S 5.
- 4 International interworking between gateways
- The international interworking between gateways allows a Videotex terminal
- located in country A to access the Videotex services located in country B via a
- Videotex service of country A. The configuration for the international
- interworking between gateways is described by Figure 1/T.101:
- Fig. 1/T.101/TO803410-89 = 3 cm
-
- 4.1 International interworking at network level
- 4.1.1 International interworking between Videotex services should preferably
- take place between networks of the same type when these networks are provided by
- both Administrations involved (PSPDN, CSPDN, ISDN and leased lines).
- 4.1.2 The network service definition of open systems interconnection for CCITT
- application is defined in Recommendation X.213.
- 4.1.3 When the interworking takes place between Videotex services operated on
- different types of network, Recommendation X.75 should apply. Interworking with
- ISDN should be in accordance with Recommendation T.90.
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- 4.2 Transport layer
- The transport layer service of open systems interconnection for CCITT
- applications is defined in Recommendation X.214.
- The transport protocol of open systems interconnection for CCITT
- applications is specified in Recommendation X.224.
- Both classes 0 (corresponding to Recommendation T.70) and 2 may be used.
- When class 0 is selected, then the protocol used is fully compatible with
- CCITT Recommendation T.70. When class 2 is selected, explicit flow control is to
- be used.
- 4.3 Session layer
- This session layer service of open systems interconnection for CCITT
- applications is defined in Recommendation X.215. The session protocol of open
- systems interconnection for CCITT applications is specified in Recommendation
- X.225.
- The use of the session protocols by Videotex interworking is defined in
- Recommendation T.523.
- 4.4 Presentation layer
- 4.4.1 Presentation protocol
- The presentation layer service of open systems interconnection for CCITT
- applications is defined in Recommendation X.216. Presentation protocol of open
- systems interconnection for CCITT applications is specified in Recommendation
- X.226.
- The use of the presentation protocols by Videotex interworking is defined
- in Recommendation T.523.
- 4.4.2 Coding of Videotex information
- Coding of the contents of the display-data element
- The Videotex content conforms to one of the several different data
- syntaxes. A data syntax, referred to as interworking data syntax, is described in Annex A. There are three existing data
- syntaxes, based on Recommendation T.50 and referred to as data
- syntax I, data syntax II and data syntax III. They are described in
- Annex B, Annex C and Annex D respectively. All the four annexes
- form an integral part of this Recommendation.
- Different Administrations implementing a Videotex service may
- use one of the three above data syntaxes.
- If two countries implement the same data syntax, then Videotex
- interworking between the two countries can use that same data
- syntax.
- If one country implements one data syntax and another country
- implements a different data syntax, then Videotex interworking
- between the two countries can either:
- i) use the interworking data syntax as the intermediary syntax.
- Transcoding/conversion into and from the interworking data syntax by
- the two countries will be required; or
- ii) use one of the two data syntaxes with transcoding/conversion performed
- either at the originating or at the destination country.
- t
- the designation and invocation of the Scomplete codeT escape sequence may be
- used:
- ESC 2/5 4/3 for data syntax I
- ESC 2/5 4/4 for data syntax II
- ESC 2/5 4/1 for data syntax III
- The Scomplete codeT environment will be terminated either by the sequence:
- ESC 2/5 4/0
- or by the designation and invocation of any other complete code.
- 4.5 Application layer
- The association control service element (ACSE) of open systems
- interconnection for CCITT applications is defined in Recommendation X.217. The
- association control service element (ACSE) protocol of open systems
- interconnection for CCITT applications is specified in Recommendation X.227.
- The application layer for Videotex interworking makes use of the following
- Recommendations:
- V Recommendation T.400: Introduction to document architecture, transfer
- and manipulation
- V Recommendation T.411: Open document architecture (ODA) and interchange
- format; Introduction and general principles
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- PAGE10 Fascicle VII.5 - Rec. T.101
-
- V Recommendation T.412: Open document architecture (ODA) and interchange
- format; Document structures
- V Recommendation T.414: Open document architecture (ODA) and interchange
- format; Document profile
- V Recommendation T.415: Open document architecture (ODA) and and
- interchange format; Document interchange format (ODIF).
- The application layer for Videotex interworking makes use of DTAM
- (document transfer and manipulation) service and protocol described in
- Recommendations T.431, T.432 and T.433.
- The application layer for Videotex interworking makes use of operational
- structures described in Recommendation T.441.
- Recommendation T.564 describes the Videotex interworking application
- profile and the gateway characteristics.
- Recommendation T.504 describes the document application profile for
- Videotex interworking.
- Recommendation T.523 describes the communication application profile for
- Videotex interworking.
- Recommendation T.541 describes the operational application profile for
- Videotex interworking.
- 4.6 Relation with DTAM/ODA
- The relations with the document architecture (Recommendation T.412) and
- the document interchange format (see Recommendation T.415) are expressed through
- the content architecture class attributes, and the content portion attributes are
- described in '' 6 and 7.
- 5 International interworking between a terminal and a host
- 5.1 Access via PSTN or ISDN bearer service
- Fig. T.101/TO803420-89 = 4 cm
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- In this configuration, the terminal uses the international PSTN
- (respectively the ISDN bearer services) to reach the host. On the international
- link, the following protocols should be used:
- layers 1 to 3 via PSTN: the protocols defined by the host;
- layers 1 to 3 via ISDN bearer service2) : Recommendation T.90;
- layers 4 to 7: the protocols (if any) defined by
- the host located in country B;
- data syntax: data syntax defined by the host;
- dialogue/service functions: functions defined by the host.
- 5.2 Access via PSPDN or ISDN bearer service
- Fig. T.101/TO803430-89 = 4 cm
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- In this configuration, the terminal uses the international PSPDN
- (respectively the ISDN bearer services) to reach the host. On the international
- link, the following protocols should be used:
- layers 1 to 3 via PSPDN: Recommendation X.75;
- layers 1 to 3 via ISDN bearer service2): Recommendation T.90;
- layers 4 to 7: the protocols (if any) defined by
- the host located in country B;
- data syntax: data syntax defined by the host;
- dialogue/service functions: functions defined by the host.
- 5.3 Access via PSPDN/PAD
- Fig. T.101/TO803440-89 = 4 cm
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- In this configuration, the terminal is connected to a PAD which gives
- access to the international PSPDN; both terminal and PAD are located in country
- A. The type of connection between the terminal and the PAD is a national matter
- (generally the PSTN or a leased line).
- The host of country B may be accessed through the international PSPDN. The
- type of connection between the host and the national PSPDN is a national matter
- (generally a leased line).
- On the international link, the following protocols should be used:
- layers (1 to 3): Recommendation X.75;
- above layer 3: Recommendation X.29 + Recommendation X.3;
- data syntax: data syntax defined by the host
- located in country B;
- dialogue/service functions: functions defined by the host.
- 5.4 Access via PSPDN through a VIU
- Fig. T.101/TO803450-89 = 4 cm
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- In this configuration, the terminal is connected to a VIU (Videotex
- interface unit) which gives access to the international PSPDN; both the terminal
- and the VIU are located in country A. The type of connection between the terminal
- and the VIU is a national matter (generally the PSTN or a leased line). The VIU
- performs two functions: it supports terminals and converts data syntaxes. It is
- up to the Administration of country A to decide how a VIU is implemented: it may
- be realized as a separate system or integrated with an existing equipment (PAD or
- Videotex access point for example).
- The host country B may be accessed through the international PSPDN. The
- type of connection between the host and the national PSPDN is a national matter
- (generally a leased line).
- On the international link, the following protocols should be used:
- layers (1 to 3): Recommendation X.75;
- above layer 3: Recommendation X.29 + Recommendation X.3.
- Alternatively Recommendation X.200 based protocols
- can be used. For this case, application profiles
- will need to be defined in T.500 Series of
- Recommendation. This is for further study.
- data syntax: the data syntax defined by the host
- located in country B;
- dialogue/service functions: those defined by the host.
- 5.5 Access via PSPDN through a VSU
- Fig. T0803460-89 = 4 cm
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- 2) The protocols to be used in the ISDN Videotex teleservice are for further study.
-
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- PAGE10 Fascicle VII.5 - Rec. T.101
-
- In this configuration, the terminal is connected to a VSU (Videotex
- service unit) which gives access to the international PSPDN; both the terminal
- and the VSU are located in country A. A VSU is a VIU which is also in charge of
- handling application charge and accounting. It is up to Administration of country
- A to decide to set up or not a VSU and to decide how a VSU, if any, is to be
- implemented: it may be realized as a separate system or integrated with an
- existing equipment (PAD, Videotex access point or Videotex service center).
- The host in country B may be reached through the international PSPDN. The
- type of connection between the host and the national PSPDN is a national matter
- (generally a leased line).
- On the international link, the following protocols should be used:
- layers (1 to 3): Recommendation X.75,
- above layer 3: Recommendation X.200 based protocols.
- For this case applications profiles need to be defined in the
- T.500 Series. This is for further study.
- Alternatively Recommendation X.29 plus Recommendation X.3 may
- be used. Extensions (Application rules) to
- Recommendation X.29 are necessary (see S 5.6);
- data syntax: the data syntax defined by the host
- located in country B;
- dialogue/service functions: those defined by the host.
- 5.6 Application rules for X.29 to support administrative functions
- When an international communication is established via a VSU using
- Recommendation X.29, X.29 Videotex commands may be used to allow application
- charges (if any) to be passed from the host to the VSU.
- Videotex commands should be sent in complete packet sequences with the Q
- bit set to one.
- Videotex commands use a T(ype)-L(ength)-V(alue) encoding. Fixed length
- commands do not require any length indicator. When used, length indicator is
- coded on two bytes and defines the total length in bytes of the V field.
- In order to distinguish Videotex commands from PAD commands as currently
- defined by Recommendation X.29, the type value of a Videotex command is defined
- with the most significant bit set to one.
- The following values are proposed to support the exchange of charging of
- international connections:
- - Administration (99H) L2 charging (82H), L2 charging-parameter.
- The charging parameter may take either the value service-operation
- (80H) or the value application-operation (81H); both values may be
- present within the same charging parameter:
- - service-operation (80H) L1 service-parameter
- - application-operation (81H) L1 application parameter.
- The service parameter is time dependent and may correspond either to the
- amount period (80H) or to the duration of the period (81H) or to a combination of
- them:
- - amount (80H) L1 value
- - period (81H) L1 value.
- The application parameter may be frame dependent (80H), time dependent
- (81H) or transaction dependent (82H) or a combination of them:
- - frame (80H) L1 value
- - time (81H) L1 charging-on-time-parameter
- - transaction (82H) L1 value.
- The charging-on-time parameter is organized as the service parameter.
- L1 is an acronym for a length coded on one byte.
- L2 is an acronym for a length indicator coded on two bytes.
- The following depicts the coding mechanism:
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- Administration L2 Charging L2 (Service) (Application)
- (99H) (82H)
- (Service) ::= Service L1 (Amount L1 value) (Period L1 value)
- (80H) (80H) (81H)
- (Application) ::= Application L1 (Frame) (Time) (Transaction)
- (81H)
- (Frame) ::= Frame L1 value
- (80H)
- (Time) ::= Time L1 (Amount L1 value) (Period L1 value)
- (81H) (80H) (81H)
- (Transaction) ::= Transaction L1 value
- (82H)
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- Fascicle VII.5 - Rec. T.100 PAGE1
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- 6 Content architecture class attributes
- 6.1 Content architecture class
- The value of the attribute "content architecture class" of a basic
- component description that conforms to this Recommendation T.101 is a ASN1 object
- identifier with the value.
- { 0 1 8 16 3 }
- 6.2 Content type
- The content architecture class attribute "content type" cannot be used to
- specify the content architecture class defined in this Recommendation.
- 7 Content portion attributes
- 7.1 Type of coding
- Classification Defaultable
- Applicability Videotex content architecture class
- Structure ASN1 object identifier
- Permissible values ASN1 object identifier
- { 0 1 8 16 4 } for "IDS encoding"
- { 0 1 8 16 5 } for "Data syntax I encoding"
- { 0 1 8 16 6 } for "Data syntax II encoding"
- { 0 1 8 16 7 } for "Data syntax III encoding"
- Default value: "IDS encoding"
- Definition: for Videotex interworking, the possible values correspond to
- the data syntaxes described in Annexes A, B, C, D of this
- Recommendation.
- 7.2 Specific coding attributes
- These attributes provide additional information required for
- encoding/decoding the content information, as well as other information intrinsic
- to the content portion and type of coding.
- 7.2.1 Subset
- Classification Defaultable
- Applicability Videotex content architecture class
- Type of coding "IDS encoding"
- Values Integer [0, 1 to 5, 81 to 92]
- Default value 0
- Definition This attribute identifies the subset (rank or profile)
- used within the IDS. Value 0 is used when no subset is
- specified.
- 7.2.2 Rank
- Classification Defaultable
- Applicability Videotex content architecture class
- Type of coding "Data syntax I encoding"
- Values Integer [0, 1 to 5]
- Default value 0
- Definition This attribute identifies the rank used within Data
- syntax I. Value 0 is used when the rank is not specified.
- 7.2.3 Profile
- Classification Defaultable
- Applicability Videotex content architecture class
- Type of encoding "Data Syntax II encoding"
- Values Integer [0, 81 to 92]
- Default value 0
- Definition This attribute identifies the profile used within Data
- Syntex II. Value 0 is used when the profile is not
- specified.
- 8 Formal definition of Videotex dependent data type
- 8.1 Introduction
- This section contains formal definition in ASN.1 notation (defined in
- Recommendation X.208) of the data type corresponding to attributes applicable to
- Videotex.
- This data type is:
- - the data type to represent specific coding attributes.
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- 8.2 Representation of specific coding attributes
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- Videotex-coding-attributes ::= CHOICE {
- subset [0] IMPLICIT subset OPTIONAL
- rank [1] IMPLICIT rank OPTIONAL
- profile [2] IMPLICIT profile OPTIONAL }
- Subset a)
- ::= INTEGER { undefined (0)
- rank 1 (1)
- rank 2 (2)
- rank 3 (3)
- rank 4 (4)
- rank 5 (5)
- profile 1 (81)
- profile 2 (82)
- profile 3 (83)
- profile 4 (84)
- profile X1-1 (85) b)
- profile X1-2 (86)
- profile X1-3 (87)
- profile X1-4 (88)
- profile X2-1 (89)
- profile X2-2 (90)
- profile X2-3 (91)
- profile X2-4 (92) }
- Rank ::= INTEGER { undefined (0)
- rank 1 (1)
- rank 2 (2)
- rank 3 (3)
- rank 4 (4)
- rank 5 (5) }
- Profile ::= INTEGER { undefined (0)
- profile 1 (81)
- profile 2 (82)
- profile 3 (83)
- profile 4 (84)
- profile X1-1 (85)
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- profile X1-2 (86)
- profile X1-3 (87)
- profile X1-4 (88)
- profile X2-1 (89)
- profile X2-2 (90)
- profile X2-3 (91)
- profile X2-4 (92) }
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- a) Use of subset IDS is for further study.
- b) Profil Xi-j: geometric profile Xi together with alphamosaic profile j.
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- 8.3 Summary of ASN.1 object identifiers (see Table 1/T.101)
- TABLE 1/T.101
-
- Videotex document application profile 0 1 8
- 16 0
- DM1 communication application profile 0 1 8
- 16 1
- Videotex operational application profile 0 1 8
- 16 2
- T.101 Content architecture class 0 1 8
- 16 3
- Type of coding
- IDS 0 1 8
- 16 4
- Data syntax I 0 1 8
- 16 5
- Data syntax II 0 1 8
- 16 6
- Data syntax III 0 1 8
- 16 7
- Application context 0 1 8
- 16 8
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