1、CEPT T/TE*Ob-O4*E W 2326434 0009952 O W -v I O TJTE06-04E Page 1 Recommendation T/TE 06-04 (Edinburgh 1988) VIDEOTEX PRESENTATION LAYER DATA SYNTAX PROCESSABLE DATA This document describes the basic kernel of a Videotex Processable Data protocol to enable telesoftware downloading and data transfer t
2、o auxiliary devices (i.e. printers) to Videotex Terminals . Extensions will be made to this basic kernel in order to provide file transfer on a symmetrical basis . The protocol is a subset of a more general Videotex Processable Data protocol under development in CEPT TE-1 . Additionally, Appendix 1
3、gives a presently used Processable Data protocol which is not an integral part of this Recommendation . O . 1 . 1.1. 1.1.1. 1.1.2. 1.1.3. 1.1.4. 1.1.5. 1.2. 1.2.1. 1.2.2. 1.2.3. 2 . 2.1. 2.2. 2.2.1. 2.2.2. 2.2.3. 2.2.4. 2.2.5. 2.2.6. 2.2.7. 2.2.8. 2.3. 2.3.1. 2.3.2. 2.3.3. 2.4. 2.5. 2.5.1. 2.5.2. 2.
4、6. 2.6.1. 2.6.2. 2.6.3. Contents GENERAL INTRODUCTION . SERVICE DEFINITION Primitive description Association establisherit Association release . Association abort Mass transfer . Error recovery . Application description . Header Teleso f t ware application . Printer device application Definitions .
5、T-Associate T-Release . T-Write T- Transfer-reject T-Read-restart . T- Response-positive . T-Response-negative . Exceptions and timers Application response tinier Abnormal termination of the mass transfer . Errors outside a muss transfer phase Use of DDU layer . Coding of TDUs Strttcture of TDUs . C
6、oding of TDUs File coding . File structure coding File header coding . Coding of data intended for a standardized printer T-PROTOCOL SPECIFICATION Description and use of TDU . T-Abort 3 3 3 4 5 5 6 8 8 8 10 10 11 11 11 11 12 12 13 13 13 13 14 14 14 14 14 15 15 15 16 17 17 18 21 Edition of September
7、15. 1989 - L / i I CEPT T/TE*Ob-O4*E 2326434 0009953 2 W TITE 06-04 E Page 2 3 . 3.1. 3.2. 3.2.1. 3.2.2. 3.2.3. 3.3. 3.3.1. 3.3.2. 3.3.3. 3.3.4. 3.3.5. 3.4. 3.4.1. 3.4.2. 3.4.3. 3.4.4. 3.4.5. 3.4.6. 3.4.7. 3.5. 3.5.1. 3.5.2. 3.5.3. D-PROTOCOL SPECIFICATION . Definitions General overview of the proto
8、col Structure of DDUs Error detection and recovery Repertoire and use of dialogue data units . Flags D-Set-mode . D-Data . D-Response-positive D-Response-negative . UseofBCS . Use of$ags . D.U.Abr6 Error detection and recovery mechanism Use of sequence numbering . Use of timers Actions in the event
9、of DDU errors Actions in the event of DDU exceptions Actions in the event of timer expiration Coding . Translation modes DDUmodes . Coding of DDUs . . . . . ANNEX A: Examples of processable data application APPENDIX 1 : Alternative processable data protocol . 23 . 23 . 23 . 23 . 23 . 23 . 24 . 24 .
10、25 . 25 . 26 . 26 . 26 . 26 . 26 . 27 . 27 . 27 . 27 . 27 . 27 . 27 . 29 . 29 Edition of October 31. 1989 . / c . TITE 06-04 E Page 3 data application TDU _ _ _ _ _ _ _ _ _ _ T-Protocol TDU Layer handling DDU Layer handling - - - _ _ _ _ _ _ _ D-Protocol DDU US-handling - _ - _ _ _ _ _ _ O. GENERAL
11、INTRODUCTION The Videotex processable data facility specified in this document is a subset of a more general Videotex processable data protocol under development in CEPT TE-1. This subset, called basic kernel, is primarilly intended to enable telesoftware downloading (from a host to a terminal) when
12、 transmission to the terminal may be limited to the storage of pre-dened character sequences accessible only by conventional Videotex commands. Extensions will be made to this basic kernel in order to privide file transfer on a symmetrical basis (i.e. file transfer in both directions under the contr
13、ol of either the host or the terminal). The facility provides particularly for the downloading of les of data; these files may contain computer software, but other file types are not precluded. This subset also provides for data to be reliably transferred to devices associated with a Videotex termin
14、al under control of the received data, In addition to transparent transfer, specific standardized provisions are made for passing data to an associated printer, but the protocol is not limited to this device, and other devices may be standardized later. Section 1. of this document describes the func
15、tions which are offered to an application using the processable data facility. These functions are described in terms of service elements. In order to allow for the transfer of les in already existing Videotex systems as well as allowing more advanced facilities for future systems, the transfer is d
16、escribed as consisting of two layers. Processable data, including telesoftware files, data for printing, file parameters and control data related to the downloading procedure are transmitted by means of Telesoftware Data Units (TDUs). These TDUs are exchanged between cooperating entities according t
17、o the T-protocol. This protocol as well as the specific rules for telesoftware and printer device applications are specified in section 2. of this document. In addition Dialogue Data Units (DDUs) are used for adaptation to the different Videotex systems. Optional 8-bit transparency capabilities and
18、optional error detection and recovery facilities are provided. Handling of these DDUs are described in section 3. of this document. The DDU-layer uses US-handling in conformance with the definitions of T/TE 06-01 as a delimiter for telesoftware applications to support the Processable Data protocols.
19、 Figure below describes the theoretical model for handling processable data. HOST TERMINAL Processable data application TDU handling DDU handling US-handling 1. SERVICE DEFINITION 1.0. Introduction This section defines in an abstract way the externally visible service provided by the TDU Layer in te
20、rms Of: a) the primitive actions and events of the service, b) the parameter data associated with each primitive action and event, c) the relationship between, and the valid sequence of, these actions and events. This section also describes the processable data applications. Edition of September 15,
21、 1989 CEPT T/TE*Ob-Oi*E 88 S32b4LY 0009955 b m TITE 06-04 E Page 4 The conventions used to describe this service are based on CCITT Recommendation X.210 (OS1 layer service definition conventions). This section also makes use of the following terms as they are defined in Recommendation X.210: a) serv
22、ice user b) service provider c) primitive d) request e) indication f) response g) conformation The following definitions also apply: Basic kernel: This term corresponds to the service which is described in this document. Extensions will be made to this kernel to take into account the requirements of
23、 enhanced applications (e.g. symmetrical services). Processable data application: The entity which makes use of the service defined in section 1.1. In the basic kernel two applications are defined: telesoftware and printer device. Attribute: A data element, having a defined meaning, together with a
24、statement of the set of possible values it may take. File: A collection of informations having a common set of attributes. File attribute: The name and other identifiable properties of a file. The attributes refer to the file as a whole, or to its internal structure. 1.1. Primitives description 1.1.
25、1. Association establishment 1.1.1.1. Function T-ASSOCIATE is used by a service user to associate with a specified processable data application (identified by the “application name” parameter). Note. In the basic kernel, a T-ASSOCIATE request may only be initiated by the host. T-ASSOCIATE is an opti
26、onally confirmed service, the parameter “explicit confirmation” indicates whether or not an explicit confirmation is requested. 1.1.1.2. Parameters Parameter Application name Service class Explicit confirmation Timeouts User data Result T-ASSOCIATE T-ASSOCIATE reauest I indication Mandatory Mandator
27、y Mandatory Optional Optional Mandatory (=) Mandatory (=) Mandatory (=) Optional (=) Optional (=) I T-ASSoCIATE confirmation T-ASSICIATE response Optional Optional (=) Mandatory Mandatory (=): The value of the parameter is identical to the value of the corresponding parameter in the preceding reques
28、t or response prinlitive. Application name : The parameter “application name” announces the use of a specified processable data application. This parameter is a variable length string. The following standardized names are defined : !A: Any application (including telesoftware and printer). !T: Teleso
29、ftware (see 1.2.2.). !P: Printer device (see 1.2.3.). Service class: This parameter is used to indicate which service class is used. It may take the following values: a) “basic kernel” b) “symmetrical” (not used in the basic kernel). Explicit confirrnation: This parameter is used to indicate whether
30、 or not explicit confirmation is requested. / . Edition of September 15, 1989 f -I_ 1.1.1.3. 1.1.2. 1.1.2.1. 1.1.2.2. 1.1.2.3. 1.1.3. 1 A.3.1. T-ASSOCIATE request - TITE 06-04 E Page 5 T-ASSOCIATE indicion - Parameter User data Result T-ASSOCIATE confirmation d T-RELEASE T-RELEASE T-RELEASE T-RELEAS
31、E request indication response confirmation Optional Optional (=) Optional Optional (=) Mandatory Mandatory T-ASSOCIATE response I- If explicit confknation is not requested and if the application specified in a T-ASSOCIATE is not available in the terminal, or in the case of any user error, then the t
32、erminal should transmit a reject code for the T-ASSOCIATE response, using the T-ABORT service (see section 1.1.3.). Association release Function The T-RELEASE service is used to request the orderly termination of the processable data application. Note. In the basic kernel a T-RELEASE request may onl
33、y be initiated by the host. Parameters Association release operation T-RELEASE request - T-RELEASE confirmation T-RELEASE indication - T-RELEASE response Association abort Function A T-ABORT request can be sent at any time after having received a T-ASSOCIATE indication. It is recommended that the T-
34、ABORT service is not used to reject a T-ASSOCIATE for which explicit conkma- tion was requested. Note. In the basic kernel a T-ABORT request may only be initiated by the terminal. CEPT T/TE*Ob-O4*E 8 W 2326434 0009957 T W TITE 06-04 E Page 6 1.1.3.2. Parameters I I T-ABoRT reauest Parameter I No par
35、ameter is associated with this primitive. 1.1.3.3. Association abort operation T-ABORT request - 1.1.4. 1.1.4.1 T-ABORT indication I- Mass transfer This service provides for confirmed and reliable transfer of data to virtual memory space in the terminal. The virtual memory is regarded as a sequence
36、of bytes or as a sequence of records. The relation of this virtual memory to files, foreground memory, of other devices in the actual terminal is defined in each case by the file attributes included in the file header. T-WRITE service The T-WRITE primitives carry data forming a part of the mass tran
37、sfer from the service initiator to the receiver. The data associated with each of these primitives are intended to immediately follow that of the previous T-WRITE in the virtual memory space. Note. In the basic kernel a T-WRITE request may only be initiated by the host. T-WRITE is an optionally conf
38、irmed service. Parameters T-WRITE T- W RITE T-WRITE T- WRITE request indication response confirmation Parameter Explicit confirmation Mandatory Mandatory (=) First block Mandatory Mandatory (=) Data field Mandatory Mandatory (=) Result Mandatory Mandatory (=) (=): The value of the parameter is ident
39、ical to the value of the corresponding parameter in the preceding request or response primitive. Explicit confrmation: This parameter is used to indicate whether or not explicit confirmation is requested. First block: This parameter is used to indicate whether or not the data contained in the data f
40、ield parameter consist in the beginning of the file. Dntafeld: It is used to convey data from the file, it is a variable length string of up to 1024 bytes. Result: This parameter indicates, if the explicit confirmation has been requested, that the service has been accepted or rejected. The result pa
41、rameter set to “reject” has the effect of restarting the transmission from the T-WRITE following the last conrmed T-WRITE (or from the first T-WRITE of the file if no T-WRITE was previously conrmed). The T-WRITE-END service is a confirmed service, so the corresponding response code should be sent by
42、 the receiver before any other protocol exchange. Note. In the basic kernel a T-WRITE-END request may only be initiated by the host. Parameters 1.1.4.2. T-WRITE-END service T-WRITE-END T-WRITE-END T-WRITE-END T-WRITE-END request indication response confirmation Parameter First block Mandatory Mandat
43、ory (=) Data field Optional Optional (=) Result Mandatory Mandatory (=) (=): The value of the parameter is identical to the value of the corresponding parameter in the preceding request or response primitive. Edition of September 15, 198%- TITE 06-04 E Page 7 e T-WRITE request - T-WRITE request T-U-
44、EXCEPTION-REPORT indication 1 First block: This parameter is used to indicate whether or not the data contained in the data field parameter consist in the beginning of the file. DataJiekd: It is used to convey data from the le, it is a variable length string of up to 1024 bytes. Result: This paramet
45、er indicates whether or not the file transfer has correctly been completed. 1.1.4.3. Operation of the mass transfer procedure It is the purpose and the responsibility of the mass transfer phase to ensure the correct transfer of the identified mass data. A mass transfer phase is initiated by T-WRITE
46、request and indication primitives with the first block of data containing the file header or a part of it, and during a mass transfer phase, the reception of a valid T-WRITE indication should cause the data to be added or oveiwritten at the appropriate place in the defined memory space. The data fie
47、lds acompanying T-WRITE or T-WRITE-END are assembled into a file according to the parameters specified in the le header, and a T-WRITE-END response and confirmation should only be transmitted when the terminal has successfully received and stored (as required) the transferred le. Positive conrmation
48、 of T-WRITE-END indicates that the terminal accepts the responsibility of the le, negative conrmation indicates that the terminal does not accept the responsibility of the file. In the printer device application, the data fields are stored or passed to the printer device. The data must be transferre
49、d sequentially and contiguously. The T-WRITE-END response and confirmation should be issued only when the terminal has successfully received and forwarded the transferred data or has reliably stored them for later transfer. The mass transfer phase is terminated by T-WRITE-END response and confirmation primitives. T-ABORT and T-U-EXCEPTION-REPORT services also terminate a mass transfer phase. In case of any user error, the terminal should issue the appropriate code defined in the paragraph 1.1.5, using the T-U-EXCEPTION-RE
