.rs .\" Troff code generated by TPS Convert from ITU Original Files .\" Not Copyright ( c) 1991 .\" .\" Assumes tbl, eqn, MS macros, and lots of luck. .TA 1c 2c 3c 4c 5c 6c 7c 8c .ds CH .ds CF .EQ delim @@ .EN .nr LL 40.5P .nr ll 40.5P .nr HM 3P .nr FM 6P .nr PO 4P .nr PD 9p .po 4P .rs \v | 5i' .ce 1000 ANNEX\ B .ce 0 .ce 1000 (to Recommendation T.70) .sp 9p .RT .ce 0 .LP B.1 \fIState tables\fR .EF '% Fascicle\ VII.5\ \(em\ Rec.\ T.70'' .OF '''Fascicle\ VII.5\ \(em\ Rec.\ T.70 %' .sp 1P .RT .PP The state tables: .RT .LP B\(hy1/T.70:\ Transport connection establishment, calling side .LP B\(hy2/T.70:\ Transport connection establishment, called side .LP B\(hy3/T.70:\ Data phase (symmetrical protocol) .LP present the transitions of the transport protocol in a table form in contrast to the diagram form to be seen in Annex\ A. While the diagrams are useful to overview the protocol mechanism the appropriate tables give clear information of which event is possible in which state and which actions are to be performed. Moreover each of the events and conditions is combined with a shortening in brackets (e.g.:\ E\ 5) which is a pointer to the 2nd\ part of this annex, so that the reader of these tables can easily come to know which meaning a certain event, action or condition has. .PP An impossible event related to a certain state can be recognized by an empty field in the crossing\(hypoint of the state and the event. .sp 1P .LP B.2 \fILists of events, actions and conditions\fR .sp 9p .RT .PP The lists of events (Table\ B\(hy4/T.70), actions (Table\ B\(hy5/T.70) and conditions (Table\ B\(hy6/T.70) intend to care for detailed explanations and clarification related to the protocol components (events, actions and conditions) found in the diagrams and tables. .PP All the components in the tables are accompanied by a list number (e.g.\ E\ 1, A\ 10, C\ 3,\ etc.) which can be interpreted as a pointer to the corresponding additional information in the lists. The letters\ E, A, C\ of the list numbers stand for Event, Action, Condition. .PP The following abbreviations are used: .RT .LP EM End Mark .LP LI Length Indicator of the transport block (octet 1) .LP loc. local .LP NC Network Connection .LP NS Network Service .LP NSDU Network Service Data Unit .LP PLI Parameter Length Indicator .LP TC Transport Connection .LP TP Transport Protocol .LP TPDU Transport Protocol Data Unit .LP TS Transport Service .LP TSDU Transport Service Data Unit .LP AND, OR and NOT (used mainly in\ E\ 5) shall be considered as the known Boolean operators. .LP .rs .sp 8P .ad r Blanc .ad b .RT .LP .bp .ce \fBH.T. [T3.70]\fR .ps 9 .vs 11 .nr VS 11 .nr PS 9 .TS center box; cw(342p) . TABLE\ B\(hy1/T.70 .T& cw(342p) . { \fBState table for calling side\fR } .TE .TS center box ; lw(51p) | lw(68p) sw(74p) sw(68p) | lw(68p) , ^ | l | l | l | l. { State Event Idle Waiting 0.1 0.2 0.3 1.1 } _ .TE .nr PS 9 .RT .ad r \fBTABLEAU B\(hy1/T.70 [T3.70] \ \ (\*`a l'italienne), p.\fR .sp 1P .RT .ad b .RT .LP .bp .ce \fBH.T. [T4.70]\fR .ps 9 .vs 11 .nr VS 11 .nr PS 9 .TS center box; cw(342p) . TABLE\ B\(hy2/T.70 .T& cw(342p) . { \fBState table for called side\fR } .TE .TS center box ; lw(51p) | lw(68p) sw(74p) sw(68p) | lw(68p) , ^ | l | l | l | l. { State Event Idle Waiting 0.1 0.2 0.3 1.1 } _ .TE .nr PS 9 .RT .ad r \fBTABLEAU B\(hy2/T.70 [T4.70] \ \ (\*`a l'italienne), p.\fR .sp 1P .RT .ad b .RT .LP .bp .ce \fBH.T. [1T5.70]\fR .ce TABLE\ B\(hy3/T.70 .ce \fBData phase (symmetrical protocol)\fR .ps 9 .vs 11 .nr VS 11 .nr PS 9 .TS center box; lw(54p) | lw(72p) , ^ | l. State Event Data phase 2.1 _ .TE .nr PS 9 .RT .ad r \fBTABLEAU B\(hy3/T.70 [1T5.70], p.\fR .sp 1P .RT .ad b .RT .LP .sp 5 .bp .ce \fBH.T. [1T6.70]\fR .ce TABLE\ B\(hy4/T.70 .ce \fBList of events\fR .ps 9 .vs 11 .nr VS 11 .nr PS 9 .TS center box; cw(18p) | cw(54p) | cw(18p) | cw(138p) . No. Name Type Description _ .T& cw(18p) | lw(54p) | cw(18p) | lw(138p) . E 1 R\(hyTCR TP { Layer 4 receives via the NS N\(hyDATA indication a TPDU including the transport block TCR. } .T& cw(18p) | lw(54p) | cw(18p) | lw(138p) . E 2 R\(hyTCC TP { Layer 4 receives via the NS N\(hyDATA indication a TPDU including the transport block TCC. } .T& cw(18p) | lw(54p) | cw(18p) | lw(138p) . E 3 R\(hyTCA TP { Layer 4 receives via the NS N\(hyDATA indication a TPDU including the transport block TCA. } .T& cw(18p) | lw(54p) | cw(18p) | lw(138p) . E 4 R\(hyTBR TP { Layer 4 receives via the NS N\(hyDATA indication a TPDU including the transport block TBR. } .T& cw(18p) | lw(54p) | cw(18p) | lw(138p) . E 5 R\(hyinvalid TPDU TP { Layer 4 receives via the NS N\(hyDATA indication a TPDU whose validity check fails due to following reasons: \(em\ syntactical errors \(em\ procedure errors } .T& lw(138p) . { 1.\ \fIInvalid TPDUs due to syntactical errors\fR } .T& lw(138p) . { 1.1 TCR: 1.1.1 The value of octet 1 (LI): 1.1.1.1 \(!= the number of the TCR block octets minus 1 OR 1.1.1.2 is greater than 127 OR 1.1.1.3 is smaller than 6 OR 1.1.2 see 1.6 } .T& lw(138p) . { 1.2 TCA: 1.2.1 The value of octet 1 (LI): 1.2.1.1 \(!= the number of the TCA block octets minus 1 OR 1.2.1.2 is greater than 127 OR 1.2.1.3 is smaller than 6 OR 1.2.2 see 1.6 OR 1.2.3 The value of octet 3 (4 resp.) \(!= octet 5 (6 resp.) of the appropriate TCR block OR 1.2.4 The value of octet 7 \(!= 0 OR 1.2.5 The parameter \*QTransport Data Block Size\*U is present: 1.2.5.1 AND its value \(!= 07 (hexadecimal), in response to a TCR block without the transport data block size parameter OR 1.2.5.2 AND its value does not respond to the rules according to \(sc\ 5.2.3.2 of Recommendation\ T.70 OR 1.2.5.3 AND its value is different from the values (hexadecimal): 07, 08, 09, 0A, 0B OR 1.2.5.4 AND the PLI > 1 OR 1.2.6 LI \(!= 6 + 2N + @ pile { fIN\fR above sum above \fIi\fR~=1 } @ PLI where N is the number of parameters } .T& lw(138p) . { 1.3 TCC: 1.3.1 The value of the LI (octet 1): 1.3.1.1 \(!= the number of the TCC block octets minus 1 OR 1.3.1.2 is greater than 127 OR 1.3.1.3 is smaller than 6 OR 1.3.2 see 1.6 OR 1.3.3 The value of octet 3 (4 resp.) \(!= octet 5 (6 resp.) of the appropriate TCR block OR 1.3.4 LI \(!= 6 + 2N + @ pile { fIN\fR above sum above \fIi\fR~=1 } @ PLI where N is the number of parameters } .T& lw(138p) . { 1.4 TBR: (also see \(sc 5.4.1, Note 1) 1.4.1 The value of the LI: 1.4.1.1 \(!= the number of the TBR block octets minus 1 OR 1.4.1.2 is greater than 127 OR 1.4.1.3 is smaller than 7 OR 1.4.2 see 1.6 OR } .T& lw(18p) | lw(54p) | lw(18p) | lw(138p) . \fI(continued)\fR .TE .nr PS 9 .RT .ad r \fBTABLEAU B\(hy4/T.70 [1T6.70], p.\fR .sp 1P .RT .ad b .RT .LP .bp .ce \fBH.T. [2T6.70]\fR .ce TABLE\ B\(hy4/T.70\ \fI(cont.)\fR .ps 9 .vs 11 .nr VS 11 .nr PS 9 .TS center box; cw(18p) | cw(54p) | cw(18p) | cw(138p) . No. Name Type Description _ .T& cw(18p) | lw(54p) | cw(18p) | lw(138p) . E 5 { R\(hyinvalid TPDU \fI(cont.)\fR } TP { 1.4.3 The value of octet 3 (4 resp.) \(!= octet 5 (6 resp.) of the appropriate TC establishment block (TCR resp. TCA) received from the peer entity OR } .T& lw(138p) . { 1.4.4 The value of LI minus 6 \(!= value of the PLI OR 1.4.5 The Rejected block parameter is not present } .T& lw(138p) . { 1.5 TDT: 1.5.1 The value of the LI \(!= 2 OR 1.5.2 The TSDU end mark is 0 AND the information field is empty OR 1.5.3 The TDT block size is larger than negotiated in the establishment phase } .T& lw(138p) . { 1.6 No identified block: The value of the TPDU octet 2 is not equal to one of the following values (hexadecimal): EX, DO, 80, 70, FO. X may be in the range of 0 \(= X \(= F. } .T& lw(138p) . { 2.\ \fIInvalid TPDUs due to procedure errors\fR } .T& lw(138p) . { Failure cases: 2.1 After S\(hyTCR: 2.1.1 NOT R\(hyTCA OR 2.1.2 NOT R\(hyTCC OR 2.1.3 NOT R\(hyTBR OR 2.2 After S\(hyTCA: 2.2.1 NOT R\(hyTDT OR 2.2.2 NOT R\(hyTBR OR 2.3 After S\(hyTDT: 2.3.1 Not R\(hyTDT OR 2.3.2 Not R\(hyTBR OR 2.4 After S\(hyTCC: NOT R\(hyTCR OR 2.5 After S\(hyTBR: NOT R\(hyTDT (in state 2.1) OR 2.6 After R\(hyTDT (EM = 1): R\(hyempty TDT (EM = 1) OR 2.7 After R\(hyempty (EM = 1): R\(hyempty TDT (EM = 1) OR 2.8 After N\(hyCONNECT response: NOT R\(hyTCR } .T& cw(18p) | lw(54p) | cw(18p) | lw(138p) . E 6 T\(hyCONNECT request TS { Layer 5 requests a TC from layer 4. } .T& cw(18p) | lw(54p) | cw(18p) | lw(138p) . E 7 N\(hyCONNECT confirm NS { Affirmative answer to N\(hyCONNECT request (A 10); a NC is existing now. } .T& cw(18p) | lw(54p) | cw(18p) | lw(138p) . E 8 N\(hyDISCONNECT indication NS { Report from layer 3 to layer 4 that the NC is not existing (any more). } .T& cw(18p) | lw(54p) | cw(18p) | lw(138p) . E 9 N\(hyRESET indication NS { Indication to layer 4 that an error has occurred in layer 1, 2 or 3, possibly with data loss. The NC is kept existing. } .T& cw(18p) | lw(54p) | cw(18p) | lw(138p) . E 10 T\(hyDISCONNECT request TS { Layer 5 requests a TC clearing from layer 4. } .T& cw(18p) | lw(54p) | cw(18p) | lw(138p) . E 11 TIMEOUT loc. { The timer presently surveying a state reached its limit. Following value ranges are defined: } .T& cw(42p) | lw(84p) . Values _ .T& cw(42p) | cw(42p) | cw(42p) . States Calling side Called side _ .T& cw(42p) | cw(42p) | cw(42p) . 0.2 not applicable 45 s \(+- 30 s _ .T& cw(42p) | cw(42p) | cw(42p) . 0.3 6 s \(+- 4 s 6 s \(+- 4 s _ .T& cw(42p) | cw(42p) | cw(42p) . 1.1 45 s \(+- 30 s not applicable _ .TE .nr PS 9 .RT .ad r \fBTABLEAU B\(hy4/T.70 [2T6.70] (suite), p.\fR .sp 1P .RT .ad b .RT .LP .bp .ce \fBH.T. [3T6.70]\fR .ce TABLE\ B\(hy4/T.70\ \fI(end)\fR .ps 9 .vs 11 .nr VS 11 .nr PS 9 .TS center box; cw(18p) | cw(54p) | cw(18p) | cw(138p) . No. Name Type Description _ .T& cw(18p) | lw(54p) | cw(18p) | lw(138p) . E 12 N\(hyCONNECT indication NS { Indication to layer 4 by the layer 3 that an NC is being established; the answer to this is N\(hyCONNECT response (A 22) or N\(hyDISCONNECT request (A 4). } .T& cw(18p) | lw(54p) | cw(18p) | lw(138p) . E 13 T\(hyCONNECT response TS { Affirmative answer by the layer 5 to T\(hyCONNECT indication (A 15). } .T& cw(18p) | lw(54p) | cw(18p) | lw(138p) . E 14 R\(hyTDT TP { Layer 4 receives via the NS N\(hyDATA indication, an NSDU including the transport block TDT. } .T& cw(18p) | lw(54p) | cw(18p) | lw(138p) . E 15 T\(hyDATA request TS { Layer 5 requests the transmission of data. Whether this is a complete TSDU or not, is a local matter, and not subject of this definition. } .T& cw(18p) | lw(54p) | cw(18p) | lw(138p) . E 16 TSDU part(s) outstanding loc. { Layer 4 is ready to send the next TDT block. } _ .TE .nr PS 9 .RT .ad r \fBTABLEAU B\(hy4/T.70 [3T6.70] (fin), p.\fR .sp 1P .RT .ad b .RT .LP .bp .ce \fBH.T. [T7.70]\fR .ce TABLE\ B\(hy5/T.70 .ce \fBList of actions\fR .ps 9 .vs 11 .nr VS 11 .nr PS 9 .TS center box; cw(18p) | cw(60p) | cw(18p) | cw(132p) . No. Name Type Description _ .T& cw(18p) | lw(60p) | cw(18p) | lw(132p) . A 1 STOP Timer T1.1 loc. { Timer T1.1 surveying the state 1.1 is stopped. } .T& cw(18p) | lw(60p) | cw(18p) | lw(132p) . A 2 START Timer T0.3 loc. { Timer T0.3 surveying the state 0.3 is started after having been reset. } .T& cw(18p) | lw(60p) | cw(18p) | lw(132p) . A 3 S\(hyTBR TP { Via the NS N\(hyDATA request a NSDU including the transport block TBR is sent to the peer entity. } .T& cw(18p) | lw(60p) | cw(18p) | lw(132p) . A 4 N\(hyDISCONNECT request NS { Layer 4 requests the layer 3 to release the offered or existing NC. } .T& cw(18p) | lw(60p) | cw(18p) | lw(132p) . A 5 T\(hyDISCONNECT indication TS { Layer 5 is informed by the layer 4 that the TC being established or existing is cleared. } .T& cw(18p) | lw(60p) | cw(18p) | lw(132p) . A 6 RESTART T1.1 loc. { Timer T1.1 surveying the state 1.1 is reset and started again. Moreover, it is necessary either to limit the number of T1.1\(hyrestarts or to limit the sum of all the times of T1.1; otherwise, an infinite loop S\(hyTCR \(em R\(hyTCC \(em S\(hyTCR \(em etc., would be allowed. } .T& cw(18p) | lw(60p) | cw(18p) | lw(132p) . A 7 S\(hyTCR TP { Via the NS N\(hyDATA request a NSDU including the transport block TCR is sent to the peer entity. } .T& cw(18p) | lw(60p) | cw(18p) | lw(132p) . A 8 T\(hyCONNECT confirm TS { Affirmative answer to the event T\(hyCONNECT request (E\ 6) indicating that the data phase of the TC has been entered. } .T& cw(18p) | lw(60p) | cw(18p) | lw(132p) . A 9 START T0.2 loc. { Timer T0.2 surveying the state 0.2 is started after having been reset. } .T& cw(18p) | lw(60p) | cw(18p) | lw(132p) . A 10 N\(hyCONNECT request NS { Layer 4 requests the layer 3 for an NC to be established. } .T& cw(18p) | lw(60p) | cw(18p) | lw(132p) . A 11 STOP T0.2 loc. { Timer T0.2 surveying the state 0.2 is stopped. } .T& cw(18p) | lw(60p) | cw(18p) | lw(132p) . A 12 START T1.1 loc. { Timer T1.1 surveying the state 1.1 is started after having been reset. } .T& cw(18p) | lw(60p) | cw(18p) | lw(132p) . A 13 STOP T0.3 loc. { Timer T0.3 surveying the state 0.3 is stopped. } .T& cw(18p) | lw(60p) | cw(18p) | lw(132p) . A 14 DISCARD any R\(hyTPDU TS { Any data received by N\(hyDATA indication are discared. The transmission of further data is stopped. } .T& cw(18p) | lw(60p) | cw(18p) | lw(132p) . A 15 T\(hyCONNECT indication TS { Layer 4 indicates a request for a TC\(hyestablishment to the layer 5. } .T& cw(18p) | lw(60p) | cw(18p) | lw(132p) . A 16 RESTART T0.2 loc. { Timer T0.2 surveying the state 0.2 is reset and started again. } .T& cw(18p) | lw(60p) | cw(18p) | lw(132p) . A 17 S\(hyTCC TP { Via the NS N\(hyDATA request, an NSDU including the transport block TCC is sent to the peer entity. } .T& cw(18p) | lw(60p) | cw(18p) | lw(132p) . A 18 T\(hyDATA indication TS { Layer 4 indicates the receipt of a complete TSDU to the layer 5. How and when the contents are transferred is a local matter, and therefore, not shown here. } .T& cw(18p) | lw(60p) | cw(18p) | lw(132p) . A 19 T\(hyEXCEPTION indication TS { Layer 5 is informed of an error which occurred between the layer 1 and layer 4, possibly with data loss; the TC is kept existing. Due to this error it is possible that the following TSDU transferred to the layer 5 contains errors or deficiencies. } .T& cw(18p) | lw(60p) | cw(18p) | lw(132p) . A 20 S\(hyTDT (EM=0) TP { A TPDU with TSDU end mark set to 0 is sent to the peer entity and further parts of the TSDU will follow (i.e., segmenting occurs). } .T& cw(18p) | lw(60p) | cw(18p) | lw(132p) . A 21 S\(hyTDT (EM=1) TP { See A 20, but the TSDU end mark is set to 1 (i.e., this TPDU contains a complete TSDU or the last part of a TSDU). } .T& cw(18p) | lw(60p) | cw(18p) | lw(132p) . A 22 N\(hyCONNECT response NS { Affirmative answer to N\(hyCONNECT indication (E 12). } .T& cw(18p) | lw(60p) | cw(18p) | lw(132p) . A 23 S\(hyTBR TP { The called side sends a TBR block to the calling side in order to point to a received failured TPDU. In this case the destination reference can be set to 0. } .T& cw(18p) | lw(60p) | cw(18p) | lw(132p) . A 24 S\(hyTCA TP { Via the NS N\(hyDATA request an NSDU including the transport block TCA is sent to the peer entity. } _ .TE .nr PS 9 .RT .ad r \fBTABLEAU B\(hy5/T.70 [T7.70], p.\fR .sp 1P .RT .ad b .RT .LP .bp .ce \fBH.T. [T8.70]\fR .ce TABLE\ B\(hy6/T.70 .ce \fBList of conditions\fR .ps 9 .vs 11 .nr VS 11 .nr PS 9 .TS center box; cw(18p) | cw(60p) | cw(150p) . No. Name Description _ .T& cw(18p) | lw(60p) | lw(150p) . C 1 Retry { The TC establishment is tried once more. } .T& cw(18p) | lw(60p) | lw(150p) . C 2 No retry NOT C 1 .T& cw(18p) | lw(60p) | lw(150p) . C 3 TC acceptable { The TC offered by the peer entity is accepted by the layer 4 due to local circumstances. } .T& cw(18p) | lw(60p) | lw(150p) . C 4 TC not acceptable NOT C 3 .T& cw(18p) | lw(60p) | lw(150p) . C 5 NC acceptable { The NC offered by the layer 3 is accepted by the layer 4 due to local circumstances. } .T& cw(18p) | lw(60p) | lw(150p) . C 6 NC not acceptable NOT C 5 .T& cw(18p) | lw(60p) | lw(150p) . C 7 EM = 0 { TSDU end mark of the TDT block is 0 } .T& cw(18p) | lw(60p) | lw(150p) . C 8 EM = 1 { TSDU end mark of the TDT block is 1 } .T& cw(18p) | lw(60p) | lw(150p) . C 9 Recovery { The terminal provides the TS T\(hyEXCEPTION indication } .T& cw(18p) | lw(60p) | lw(150p) . C 10 No recovery NOT C 9 .T& cw(18p) | lw(60p) | lw(150p) . C 11 Segmentation { The TSDU received from layer 5 is longer than the negotiated TDT block size and has, therefore, to be segmented and consequently, to be reassembled on the receiver side. } .T& cw(18p) | lw(60p) | lw(150p) . C 12 No segmentation NOT C 11 _ .TE .nr PS 9 .RT .ad r \fBTABLEAU B\(hy6/T.70 [T8.70], p.\fR .sp 1P .RT .ad b .RT .LP .bp .ce 1000 ANNEX\ C .ce 0 .ce 1000 (to Recommendation T.70) .sp 9p .RT .ce 0 .ce 1000 \fBRecommendations for implementation of Recommendation X.21\fR .sp 1P .RT .ce 0 .LP C.1 \fIGeneral\fR .sp 1P .RT .PP This Annex deals with recommended actions to be taken by a telematic DTE in relation to the receipt of call progress (CP) signals from the network and in relation to the handling of optional user facilities. The adherence to these recommendations is not mandatory in order to conform to Recommendation\ T.70 but may be of importance for the performance of the DTE. .PP Telematic terminals are in general assumed to make automatic repeated call attempts and sequential automatic calls to a number of addresses for which the following actions apply. .RT .sp 1P .LP C.2 \fIReceipt of call progress signals 01 or 04\fR .sp 9p .RT .PP When one of the CPS 01 or 04 is received the DTE should use the timer T3B and wait up to 60s for the completion of the call. .RT .sp 1P .LP C.3 \fIReceipt of call progress signal 03\fR .sp 9p .RT .PP The DTE should use either timer T3A or T3B in this case, depending on the time the DTE is prepared to wait for the completion of the call. Observe that the queuing time is charged as communication time in some networks. .RT .sp 1P .LP C.4 \fIReceipt of call progress signals of the group 2 to 8\fR .sp 9p .RT .PP See Table C\(hy1/T.70. .RT .ce \fBH.T. [T9.70]\fR .ce TABLE\ C\(hy1/T.70 .ps 9 .vs 11 .nr VS 11 .nr PS 9 .TS center box; cw(60p) | cw(54p) | cw(60p) | cw(54p) . Code group/Code Delay for reattempts (s) Number of reattempts { Delay between series of reattempts (s) } _ .T& cw(60p) | cw(54p) | cw(60p) | cw(54p) . 2, 6 \(>=" 5 \(= 7 \ \(>=" 60 _ .T& cw(60p) | cw(54p) | cw(60p) | cw(54p) . 41, 42, 43, 48 5, 8 \(>=" 5 \(= 1 { Reattempts are not recommended } _ .T& cw(60p) | cw(54p) | cw(60p) | cw(54p) . 44, 45, 46, 47, 49 7 \(>=" 5 \(= 1 \(>=" 600 _ .TE .nr PS 9 .RT .ad r \fBTableau C\(hy1/T.70 [T9.70], p.\fR .sp 1P .RT .ad b .RT .PP .sp 2 \fINote\fR \ \(em\ Some networks charge for call attempts, when the call is unsuccessful due to the condition of the called DTE. Examples of such situations are the receipt of the call progress signals 21 (busy) and 45 (controlled not ready). .bp .ce 1000 ANNEX\ D .ce 0 .ce 1000 (to Recommendation T.70) .sp 9p .RT .ce 0 .ce 1000 \fBService definitions and state transition diagrams\fR .sp 1P .RT .ce 0 .ce 1000 \fBfor the HDLC procedure\fR .ce 0 .ce 1000 \fBand the network layer defined for CSPDN\fR .ce 0 .LP D.1 \fIService definitions\fR .sp 1P .RT .sp 2P .LP D.1.1 \fIPhysical service used by HDLC\fR .sp 1P .RT .LP .rs .sp 13P .ad r \fBFigure D\(hy1/T.70, p.\fR .sp 1P .RT .ad b .RT .sp 2P .LP D.1.2 \fIData link service (HDLC)\fR .sp 1P .RT .sp 1P .LP D.1.2.1\ \ \fIData link connection establishment\fR .sp 9p .RT .LP .rs .sp 19P .ad r \fBFigures D\(hy2/T.70 et D\(hy3, p.\fR .sp 1P .RT .ad b .RT .LP .bp .sp 1P .LP D.1.2.2\ \ \fIData link transfer phase\fR .sp 9p .RT .LP .rs .sp 16P .ad r \fBFigure D\(hy4/T.70, p.\fR .sp 1P .RT .ad b .RT .sp 1P .LP D.1.2.3\ \ \fIData link release\fR .sp 9p .RT .LP .rs .sp 23P .ad r \fBFigures D\(hy5/T.70, et D\(hy6 p.\fR .sp 1P .RT .ad b .RT .LP .bp .sp 1P .LP D.1.2.4\ \ \fIData link resetting\fR .sp 9p .RT .LP .rs .sp 47P .ad r \fBFigures D\(hy7/T.70 \*`a D\(hy10, p.\fR .sp 1P .RT .ad b .RT .LP .bp .sp 2P .LP D.2 \fIState transition diagrams HDLC\fR .sp 1P .RT .sp 1P .LP D.2.1 \fIThe relation between the diagrams\fR .sp 9p .RT .PP The following diagrams describe the HDLC procedure as one functional unit. The first page comprises the whole protocol and the following page gives the details to specific states. .RT .sp 1P .LP D.2.2 \fIAbbreviations\fR .sp 9p .RT .LP ABM Asynchronous balanced mode .LP ADM Asynchronous disconnected mode .LP R:xxx Receive xxx (command or response) .LP R:Cxxx Receive a command .LP R:Rxxx Receive a response .LP S:xxx Send xxx .LP F Final bit .LP P Poll bit .LP XXX Not this condition .LP RC Redrive counter .LP RCB Redrive counter busy .LP IC I\(hyFrame counter .LP V\du\\du\u Variable for sequence updating .LP .rs .sp 32P .ad r Blanc .ad b .RT .LP .bp .LP .rs .sp 47P .ad r \fBFigure D\(hy11/T.70, p.\fR .sp 1P .RT .ad b .RT .LP .bp .LP .rs .sp 47P .ad r \fBFigure D\(hy12/T.70, p.\fR .sp 1P .RT .ad b .RT .LP .bp .LP .rs .sp 47P .ad r \fBFigure D\(hy13/T.70, p.\fR .sp 1P .RT .ad b .RT .LP .bp .LP .rs .sp 47P .ad r \fBFigure D\(hy14/T.70, p.\fR .sp 1P .RT .ad b .RT .LP .bp .LP .rs .sp 47P .ad r \fBFigure D\(hy15/T.70, p.\fR .sp 1P .RT .ad b .RT .LP .bp .LP .rs .sp 47P .ad r \fBFigure D\(hy16/T.70, p.\fR .sp 1P .RT .ad b .RT .LP .bp .sp 2P .LP D.3 \fISummary of frame definitions\fR .sp 1P .RT .sp 1P .LP D.3.1 \fIInvalid frame\fR .sp 9p .RT .LP \(em frames not properly bounded by flags; .LP \(em frames containing addresses other than A or B; .LP \(em frames with frame check sequence (FCS) error; .LP \(em frames containing less than 32 bits between blags. .sp 2P .LP D.3.2 \fIValid frames\fR .sp 1P .RT .sp 1P .LP D.3.2.1\ \ \fINot expected frames\fR .sp 9p .RT .PP NEF, not expected frames (for the receiver) which lead to a frame reject condition (excluding frames with a FRMR control field): .RT .LP .sp 1 \(em a command or response control field that is undefined or not implemented; Type W \(em a frame with an information field which is not permitted or supervisory or unnumbered frame with incorrect length; Type X \(em an I\(hyframe with an information field which exceeds the maximum established length; Type Y \(em a frame with an invalid N (R). Type Z .sp 1P .LP D.3.2.2\ \ \fIExpected frames\fR .sp 9p .RT .LP \(em frames which must lead to a reaction (in accordance to the Recommendation) by the receiving station; .LP \(em frames which must be ignored only in determined states by the receiving station. .sp 2P .LP D.4 \fIX.21 service, controlled by the network layer\fR .sp 1P .RT .sp 1P .LP D.4.1 \fIX.21 connection establishment\fR .sp 9p .RT .LP .rs .sp 15P .ad r \fBFigure D\(hy17/T.70 et D\(hy18, p.\fR .sp 1P .RT .ad b .RT .LP .bp .sp 1P .LP D.4.2 \fIX.21 connection release\fR .sp 9p .RT .LP .rs .sp 47P .ad r \fBFigures D\(hy19/T.70 et D\(hy20, p.\fR .sp 1P .RT .ad b .RT .LP .bp .LP .rs .sp 47P .ad r \fBFigure D\(hy21/T.70, p.\fR .sp 1P .RT .ad b .RT .LP .bp .LP .rs .sp 47P .ad r \fBFigure D\(hy22/T.70, p.31\fR .sp 1P .RT .ad b .RT .LP .bp .ce \fBH.T. [T10.70]\fR .ce TABLE\ D\(hy1/T.70 .ce \fBApplication rules regarding the network protocol data unit (NPDU)\fR .ps 9 .vs 11 .nr VS 11 .nr PS 9 .TS center box; cw(96p) | cw(12p) sw(18p) sw(12p) sw(18p) sw(12p) sw(18p) sw(12p) sw(18p) sw(12p) , ^ | c | c | c | c | c | c | c | c | c. Conditions\ \ \(da Combination of conditions a b c d e f g h i _ .T& cw(18p) | lw(78p) | cw(12p) | cw(18p) | cw(12p) | cw(18p) | cw(12p) | cw(18p) | cw(12p) | cw(18p) | cw(12p) . C1 Transmit/receive T T T T T R R R R _ .T& cw(18p) | lw(78p) | cw(12p) | cw(18p) | cw(12p) | cw(18p) | cw(12p) | cw(18p) | cw(12p) | cw(18p) | cw(12p) . C2 NPDU length (octet) > 2 > 2 > 2 > 2 < 3 > 2 > 2 > 2 < 3 _ .T& cw(18p) | lw(78p) | cw(12p) | cw(18p) | cw(12p) | cw(18p) | cw(12p) | cw(18p) | cw(12p) | cw(18p) | cw(12p) . C3 1st octet 01/<> 01 01 01 <> * 01 01 <> * _ .T& cw(18p) | lw(78p) | cw(12p) | cw(18p) | cw(12p) | cw(18p) | cw(12p) | cw(18p) | cw(12p) | cw(18p) | cw(12p) . C4 2nd octet bits 1 to 7 0 0 <> * * * * * * _ .T& cw(18p) | lw(78p) | cw(12p) | cw(18p) | cw(12p) | cw(18p) | cw(12p) | cw(18p) | cw(12p) | cw(18p) | cw(12p) . C5 2nd octet bit 8 (M\(hybit) 0 1 * * * 0 1 * * _ .TE .nr PS 9 .RT .ad r \fBTableau D\(hy1/T.70 [T10.70], p.32\fR .sp 1P .RT .ad b .RT .LP .bp .sp 2P .LP \fBRecommendation\ T.71\fR .RT .sp 2P .ce 1000 \fBLINK\ ACCESS\ PROTOCOL\ BALANCED\ (LAPB)\fR .EF '% Fascicle\ VII.5\ \(em\ Rec.\ T.71'' .OF '''Fascicle\ VII.5\ \(em\ Rec.\ T.71 %' .ce 0 .sp 1P .ce 1000 \fBEXTENDED\ FOR\ HALF\(hyDUPLEX\ PHYSICAL\ LEVEL\ FACILITY\fR .ce 0 .sp 1P .ce 1000 \fI(Malaga\(hyTorremolinos, 1984; amended at Melbourne, 1988)\fR .sp 9p .RT .ce 0 .sp 1P .LP The\ CCITT, .sp 1P .RT .sp 1P .LP \fIconsidering\fR .sp 9p .RT .PP (a) that the Teletex service will be introduced in different types of networks, i.e.\ circuit switched public data networks (CSPDN), packet switched public data networks (PSPDN) and public switched telephone networks\ (PSTN); .PP (b) that depending on the service provided by the physical level, the link level procedures may have to cater for a half\(hyduplex transmission facility; .PP (c) that some Administrations are considering the provision of a Teletex service with a half\(hyduplex transmission facility on the\ PSTN; .PP (d) that modems according to Recommendation V.26 | fIbis\fR are suitable for half\(hyduplex transmission at 2400\ bit/s on\ PSNTs, .sp 1P .LP \fIunanimously declares\fR .sp 9p .RT .PP that this Recommendation defines the link level procedure using LAPB extended for half\(hyduplex physical level service. .LP \fB1\fR \fBIntroduction\fR .sp 1P .RT .sp 2P .LP 1.1 \fIGeneral\fR .sp 1P .RT .PP 1.1.1 Figure 1/T.71 shows the half\(hyduplex transmission module (HDTM) for extending the use of LAPB for operation of Teletex terminals connected to the PSTN where use of half\(hyduplex 2400\ bit/s modems is planned. This is referred to in Recommendation\ T.70 as\ LAPX. .sp 9p .RT .LP .rs .sp 20P .ad r \fBFigure 1/T.71 p.\fR .sp 1P .RT .ad b .RT .LP .bp .PP 1.1.2 Before the HDTM begins operation the physical circuit must be established by the appropriate PSTN call control procedures. The operation of the HDTM is such that the calling DTE will initially have the right to transmit. For the link addressing conventions refer to Recommendation\ T.70. .sp 9p .RT .sp 2P .LP 1.2 \fIArchitecture\fR .sp 1P .RT .sp 1P .LP 1.2.1 \fILevel relationships\fR .sp 9p .RT .PP It is an objective to avoid modification of the definition of LAPB in order to adapt it for half\(hyduplex operation. However, there is a functional requirement that the HDTM inhibit LAPB from sending frames during certain phases of the half\(hyduplex procedure. The means of accomplishing this functional requirement is not defined. .PP The logical relationships between LAPB, the HDTM and the physical level are as shown in Figure\ 2/T.71. .RT .LP .rs .sp 21P .ad r \fBFigure 2/T.71 p.\fR .sp 1P .RT .ad b .RT .sp 1P .LP 1.2.2 \fIControl (C) and status (S) functions\fR .sp 9p .RT .PP The following logical functions are defined to describe the interactions between LAPB and the HDTM: .RT .LP Control .LP \(em Revert to the HDTM idle state since LAPB has entered the disconnected phase (equivalent to ADM of HDLC). .LP Status .LP \(em LAPB is enabled to send frames. .LP Status .LP \(em LAPB is inhibited from sending frames. .sp 2P .LP \fB2\fR \fBState diagram and descriptions\fR .sp 1P .RT .sp 1P .LP 2.1 \fIState diagram\fR .sp 9p .RT .PP The state diagram shown in Figure 3/T.71 describes the procedure for controlling the right to transmit. The number in each ellipse is the state reference number. .bp .RT .LP .rs .sp 36P .ad r \fBFigure 3/T.71 p.\fR .sp 1P .RT .ad b .RT .sp 2P .LP 2.2 \fIState definitions\fR .sp 1P .RT .sp 1P .LP 2.2.1 \fIIdle state (state 0)\fR .sp 9p .RT .PP The DTE is in an inactive state. This is the initial state prior to call establishment and the final state after call termination. .RT .sp 1P .LP 2.2.2 \fIHalf\(hyduplex sending state (state 1)\fR .sp 9p .RT .PP The DTE is in a half\(hyduplex sending state, so that all signals generated by LAPB are passed to the physical level. .RT .sp 1P .LP 2.2.3 \fIWait for receiving state (state 2)\fR .sp 9p .RT .PP The DTE is awaiting indication that the remote DTE has entered the half\(hyduplex sending state. No signals generated by LAPB are passed to the physical level. .bp .RT .sp 1P .LP 2.2.4 \fIHalf\(hyduplex receiving state (state 3)\fR .sp 9p .RT .PP The DTE is in a half\(hyduplex receiving state, so that no signals generated by LAPB are passed to the physical level. The remote DTE is considered to be in the half\(hyduplex sending state. .RT .sp 1P .LP 2.2.5 \fIWait for sending state (state 4)\fR .sp 9p .RT .PP The DTE is awaiting indication of the availability of the physical level for transmission of frames to the remote\ DTE. All signals generated by LAPB are passed to the physical level, but LAPB is inhibited from sending frames. .RT .sp 1P .LP 2.3 \fITable of transitions between states\fR .sp 9p .RT .PP Table 1/T.71 shows the events that cause transitions from one state to another, along with any resulting actions. This shows a generalized description of the operation of the\ HDTM. .RT .sp 1P .LP 2.4 \fIState definitions expressed in terms applicable to a modem\fR \fIinterface\fR .sp 9p .RT .PP The following definitions apply to the use of the HDTM with the V.26 | fIbis\fR modem interface, as an example. .RT .sp 1P .LP 2.4.1 \fIIdle state (state 0)\fR .sp 9p .RT .PP Circuit 107 is OFF. .RT .sp 1P .LP 2.4.2 \fIHalf\(hyduplex sending state (state 1)\fR .sp 9p .RT .PP Circuit 105, circuit 106 and circuit 107 are ON. LAPB is connected to circuit\ 103 and enabled to send frames. .RT .sp 1P .LP 2.4.3 \fIWait for receiving state (state 2)\fR .sp 9p .RT .PP Circuit 107 is ON, circuit 105 is OFF. LAPB is inhibited from sending frames and disconnected from circuit\ 103, which is held in the binary\ 1 condition. Timer\ T is running. .RT .sp 1P .LP 2.4.4 \fIHalf\(hyduplex receiving state (state 3)\fR .sp 9p .RT .PP Circuit 107 is ON, circuit 105 is OFF. LAPB is inhibited from sending frames and disconnected from circuit\ 103, which is held in the binary\ 1 condition. .RT .sp 1P .LP 2.4.5 \fIWait for sending state (state 4)\fR .sp 9p .RT .PP Circuit 105 and circuit 107 are ON, and circuit 106 is OFF. LAPB is connected to circuit\ 103 but is inhibited from sending frames. .RT .sp 1P .LP 2.5 \fITable of transitions between states expressed in terms\fR \fIapplicable to a modem interface\fR .sp 9p .RT .PP Table 2/T.71 shows, in terms of the V.26 | fIbis\fR modem interface, the events that cause a state transition and the resulting action(s). .RT .sp 1P .LP 2.6 \fITimer T\fR .sp 9p .RT .PP This timer is used to recover from an apparent failure of the remote DTE to take the right to transmit. To avoid a contention condition during this recovery process, different values of timer\ T are to be used by the called and calling\ DTE. A calling\ DTE uses the value\ \fIT\fR\d\fIa\fR\u, and a called\ DTE uses the value\ \fIT\fR\d\fIb\fR\u. .PP The values of \fIT\fR\d\fIa\fR\uand \fIT\fR\d\fIb\fR\uare system parameters and must be studied further in relationship to interworking requirements and other system parameters in Recommendation\ T.70. .bp .RT .ce \fBH.T. [T1.71]\fR .ce TABLE\ 1/T.71 .ce \fBDescription of state transitions\fR .ps 9 .vs 11 .nr VS 11 .nr PS 9 .TS center box; cw(24p) | cw(90p) | cw(90p) | cw(24p) . Present state Event Action New state _ .T& cw(24p) | lw(90p) | lw(90p) | cw(24p) . 0 { Calling DTE: Data circuit established (e.g. data set ready, ready for data) } > 4 _ .T& cw(24p) | lw(90p) | lw(90p) | cw(24p) . 0 { Called DTE: Data circuit established (e.g. data set ready, ready for data) } Start timer T 2 _ .T& cw(24p) | lw(90p) | lw(90p) | cw(24p) . 4 { Indication of availability of the physical level for transmission } { Send indication to the remote DTE that the half\(hyduplex sending state has been entered Status (see Note 1) } 1 _ .T& cw(24p) | lw(90p) | lw(90p) | cw(24p) . 1 Conclusion of transmission { Send request that remote DTE enter the half\(hyduplex sending state (see Note 4) Start timer T Status (see Note 2) } 2 _ .T& cw(24p) | lw(90p) | lw(90p) | cw(24p) . 2 { Reception of indication that the remote DTE has entered the half\(hyduplex sending state } Stop timer T 3 _ .T& cw(24p) | lw(90p) | lw(90p) | cw(24p) . 2 Expiry of timer T > 4 _ .T& cw(24p) | lw(90p) | lw(90p) | cw(24p) . 3 { Reception of notification that the remote DTE is requesting a change in the direction of transmission } > 4 _ .T& cw(24p) | lw(90p) | lw(90p) | cw(24p) . 1 { LAPB has entered a disconnected phase (i.e. Conrol , see Note 3) } > 0 _ .T& cw(24p) | lw(90p) | lw(90p) | cw(24p) . 3 { LAPB has entered a disconnected phase (i.e. Conrol , see Note 3) } > 0 _ .T& cw(24p) | lw(90p) | lw(90p) | cw(24p) . Any { Physical level has no circuit to a remote DTE } > 0 .TE .LP \fINote 1\fR \ \(em\ Status indicates to LAPB that the sending of frames is enabled. .LP \fINote 2\fR \ \(em\ Status indicates to LAPB that the sending of frames is inhibited. .LP \fINote 3\fR \ \(em\ Control indicates that LPAB has entered the disconnected phase (equivalent to ADM of HDLC). .LP \fINote 4\fR \ \(em\ HDTM uses the idle data link channel state indication (at least 15 contiguous 1's) for requesting that the remote DTE enter the half\(hyduplex sending state. .nr PS 9 .RT .ad r \fBTableau 1/T.71 [T1.71] + Notes, p.36\fR .sp 1P .RT .ad b .RT .LP .bp .ce \fBH.T. [T2.71]\fR .ce TABLE\ 2/T.71 .ce \fBDescription of state transitions in terms of the V.26\fR .ce | fIbis\fR .ce \fBmodem interface\fR .ps 9 .vs 11 .nr VS 11 .nr PS 9 .TS center box; cw(24p) | cw(90p) | cw(90p) | cw(24p) . Present state Event Action New state _ .T& cw(24p) | lw(90p) | lw(90p) | cw(24p) . 0 Calling DTE: Circuit 107 ON { Turn circuit 105 0N Connect LAPB to circuit 103 } 4 _ .T& cw(24p) | lw(90p) | lw(90p) | cw(24p) . 0 Called DTE: Circuit 107 ON Start timer T 2 _ .T& cw(24p) | lw(90p) | lw(90p) | cw(24p) . 4 Circuit 106 ON { Enable sending of LAPB frames (see Note 1) } 1 _ .T& cw(24p) | lw(90p) | lw(90p) | cw(24p) . 1 { Transmission concluded (see Note 2) } { Inhibit sending of LAPB frames Disconnect LAPB from circuit 103 Hold circuit 103 in the binary 1 condition Turn circuit 105 OFF (see Note 3) Start timer T } 2 _ .T& cw(24p) | lw(90p) | lw(90p) | cw(24p) . 2 Reception of a flag Stop timer T 3 _ .T& cw(24p) | lw(90p) | lw(90p) | cw(24p) . 2 Expiry of timer T { Turn circuit 105 ON Release circuit 103 from binary 1 condition Connect LAPB to circuit 103 } 4 _ .T& cw(24p) | lw(90p) | lw(90p) | cw(24p) . 3 { Reception of 15 contiguous 1 bits (see Notes 4 and 5) } { Turn circuit 105 ON Release circuit 103 from binary 1 condition Connect LAPB to circuit 103 } 4 _ .T& cw(24p) | lw(90p) | lw(90p) | cw(24p) . 1 { LAPB has entered a disconnected phase } Turn circuit 105 0FF 0 _ .T& cw(24p) | lw(90p) | lw(90p) | cw(24p) . 3 { LAPB has entered a disconnected phase } > 0 _ .T& cw(24p) | lw(90p) | lw(90p) | cw(24p) . Any Circuit 107 OFF Turn circuit 105 OFF 0 .TE .LP \fINote 1\fR \ \(em\ It is necessary to ensure that at least one full flag is transmitted after circuit 106 comes ON. This flag may be the opening flag of the first frame. .LP \fINote 2\fR \ \(em\ The HDTM may determine that a transmission by the LAPB module has been concluded by either of the following: .LP \(em\ counting a sequence of contiguous flags on circuit 103 while in state 1, \(em\ a time\(hyout, T, \(em\ a signal from another source, e.g., from a higher level. .LP However, if no frame is transmitted while in state 1, not less than five contiguous flags shall be sent in state 1 before entry into state\ 2. .LP \fINote 3\fR \ \(em\ It is recommended that circuit 105 not be turned OFF until 15 bit times after the binary 1 condition is established on circuit\ 103. This will assure transmission of an idle sequence to the remote DTE. .LP \fINote 4\fR \ \(em\ It is recognized that whether or not an idle sequence is sent by the remote DTE, the DTE will detect an idle sequence after circuit 109 goes OFF, since according to Recommendation V.26 | fIbis\fR , this will hold circuit 104 in the binary 1 condition. .LP \fINote 5\fR \ \(em\ It is understood that circuit 109 will go OFF. Entry into state 4 may be made dependent on this OFF condition, as an implementation option. .nr PS 9 .RT .ad r \fBTableau 2/T.71 [T2.71] + Notes, p.37\fR .sp 1P .RT .ad b .RT .LP .bp .ce 1000 ANNEX\ A .ce 0 .ce 1000 (to Recommendation T.71) .sp 9p .RT .ce 0 .ce 1000 \fBAdditional rules making for greater efficiency\fR \fBin \fR \fBhalf\(hyduplex transmission\fR .sp 1P .RT .ce 0 .LP A.1 \fIGeneral considerations\fR \v'2p' .sp 1P .RT .LP \(em Greater efficiency is obtained in recovery situations. .LP \(em The application of these rules is optional. .LP \(em The application of these rules does not imply any incompatibility or entail any amendment of\ DTEs (or\ DCEs) which observe the procedures described in Recommendation\ T.71. .sp 1P .LP A.2 \fIRules of operation\fR \v'2p' .sp 9p .RT .LP 1) Before the DTE (or DCE) gives the turn back , it ensures that it has acknowledged all the frames received and accepted before it received the turn. .LP 2) If the DTE (or DCE) receives or takes the turn, it will always first retransmit all the I\(hyframes which have not been acknowledged. .LP 3) The DTE (or DCE) must replace the last RR frame in each turn, if any, by an REJ\ frame carrying the appropriate\ N(R). .LP .rs .sp 34P .sp 2P .LP \fBMONTAGE: RECOMMANDATION T.90 SUR LE RESTE DE CETTE PAGE\fR .sp 1P .RT .LP .bp