============================================================ Question 3/IX - Quality, reliability and availability of telegraph transmission (Amalgamation of Questions 3/IX and 5/IX, 1985-1988) (Concerns Study Groups I, II, IV, VII, XVII and XVIII) What- 9. It is Further development of the technical aspects of international store and forward services, for example: a) signalling and message transfer procedures to be adopted for transit working between Administration provided systems; b)-- c)--- ============================================================ Question 10/IX - TDM systems for telegraphy employing a new technique of multiplexing (Continuation of Question - ANNEX (to Question 11/IX) Terms to be defined in Recommendations concerning multiplexing R.101 channel interleaving back-to-back muldexes channel numbering scheme traffic bit receive clock dead time R.102 clamp transmit clock telegraph supply battery R.105 virtual channel R.111 framing shortest isolated element theoretical maximum modulation rate subrate padding depadding transition coding lockout R.112 Spurious element System clock R.115 Maintenance loop echo-to-echo loop both-way loop one-way loop Question 12/IX - -- Note - ANNEX (to Question 12/IX) TABLE Comments to the specific points raised in Part B of CCITT Question 12/IX (statistical muldexes) + + Items of Question Remarks + - + 1. Format of the signal - Asynchronous primarily 50 to 300 bauds with to be transmitted a possible extension up to 9600 bauds (circuits/electrical interface in accordance with V.24/V.28); - BSC (Binary Synchronous Communication) i.e. 1200/2400 bauds (EBCDIC, USASCII); - Synchronous with speeds up to maximum 50% of aggregate channel speed (non-statistical multiplexing function). + - + 2. Type of signalling Channel protocol and signalling should be used on the channels, handled transparently. V.24 interface control and channel protocol circuits to be provided as appropriate. Further functions may be considered: - automatic baud rate detection, - echoplex, - flyback buffering, - line contention aspects to be studied, etc. - telex signalling also to be studied, - polled traffic also to be studied. + + + + Items of Question Remarks + - + 3. Methods of traffic - Buffer memory should provide dynamic control to avoid allocation of channels; information overflow - memory size should be dimensioned at least to buffer data retransmission; - overflow controlled by: CTS (Clear-to-send) - ... out-of-band Xon-Xoff (DC1-DC3)... in band + - + 4. Structure of the Type X.25 level 2 frame structure with speeds signal to be trans- of 2400, 4800 and 9600 bit/s, or higher. mitted on the aggre- gate channel (Circuits/electrical interfaces in accordance with V.24/V.28). + - + 5. Methods of error Aggregate: Error protection by ARQ method correction using a cyclic redundancy check (CRC) 16-bit character to each frame. Derived channels: Parity and character framing check. + - + 6. Delay on the derived A delay figure cannot be properly defined channel without considering traffic density, aggregate/derived channel speed ratio and system configuration. This item certainly will need further study. + - + 7. Relation between the The ratio between the total derived channel number of channels input signalling rate and the output that can be derived, aggregate signalling rate should be in the the modulation rate order of 2 to 3. on the aggregate channel and the Detailed studies of traffic concentration statistical charac- characteristics are required. teristics of the traffic + - + 8. Maintenance aspects, - Two loops are considered appropriate for e.g. loops each derived channel signal and for the aggregate signal, for both local and remote controlled looping functions should be possible. - A set of alarms/visual indicators should be provided, e.g. derived channel "active", state memory overflow (traffic rate), aggregate signal synchronized, aggregate signal error rate threshold exceeded, etc. + + + + Items of Question Remarks + - + 9. The possible High speed redundancy port (stand-by arrange- requirement for the ment) may be useful in the event of failure muldex to recon- on one section of high speed link. The switch- figure dynamically over function should be automatically per- in the event of formed without losing data. Any additional communication fail- reconfiguration of the channel allocation on ure on one section the aggregate will need further study. of a link + - + 10. Consideration Data compression by means of recoding must whether recoding of be avoided. Its efficiency depends much upon the input data the used algorithm, which is difficult to offers significant specify. data compression, when this muldex is used with an unknown data source + + (Question 13/IX does not exist for 1989-1992 period.) ============================================================ Question 14/IX - Code and speed dependent TDM systems (Continuation of Question 14/IX, 1985-1988; revised wording) Further --- List of functions ============================================================ Question 15/IX - -- ============================================================ Question 17/IX - What technical --- ============================================================ Question 21/IX - --- ============================================================ Question 22/IX - ============================================================ Question 23/IX - Expanded coding techniques for text transmission over the international telex networks ============================================================ Question 24/IX - Transmission aspects of data communication networks (New Question) 1. Study arising from the implementation of CCITT Recommendations X.40 through X.58. This study point comprises all aspects of the above Recommendations. Specific points to be studied are: -comparison of Recommendations X.52 and V.14 potentially leading to the adoption of V.14 as the single or the preferred async to sync conversion technique; -comparison of Recommendations X.57 and X.30 potentially leading to the adoption of X.30 techniques as the single or the preferred rate adaptation technique. 2. Study of other transmission aspects of data communication networks. ============================================================ Question 25/IX - Numbering plan for telex networks (New Question) Considering (a) that the International Numbering Plan for telex networks is standardized in Recommendation F.69 and is implemented on a large number of telex networks; (b) that numbering solutions to various ISDN-telex networks, ISDN-PDN- telex network and PDN-telex network interworking issues will be required; what revisions or enhancements to the existing numbering and numbering plan interworking Recommendations should be made, and what new Recommendations should be developed? Note - This Question should be studied in close cooperation with Study Groups II and VII.