ITU-T X 351-1988 SPECIAL REQUIREMENTS TO BE MET FOR PACKET ASSEMBLY DISASSEMBLY FACILITIES (PADs) LOCATED AT OR IN ASSOCIATION WITH COAST EARTH STATIONS IN THE PUBLIC MOBILE SATELL.pdf

1、INTERNATIONAL TELECOMMUNICATION UNION)45G134 8 TELECOMMUNICATIONSTANDARDIZATION SECTOROF ITU).4%27/2+).G0G0“%47%.G0G0.%47/2+3-/“),%G0G0$!4!G0G042!.3-)33)/.G0G03934%-330%#)!,G0G02%15)2%-%.43G0G04/G0G0“%G0G0-%4amended at Melbourne, 1988)The CCITT,considering(a) that the PAD is defined in Recommendatio

2、n X.3;(b) that the DTE/DCE interface for a start-stop mode DTE accessing a PAD is defined inRecommendation X.28;(c) that the procedures for the exchange of control information and user data between a PAD and a packetmode DTE are given in Recommendation X.29;(d) that Recommendation X.350 gives the ge

3、neral requirements to be met for data transmission in the maritimesatellite service;(e) that start-stop mode DTEs are in use in the maritime satellite service;(f) that it is desirable that such DTEs are offered access to and from packet switched public data networksvia PADs located at or in associat

4、ion with coast earth stations or maritime satellite data switching exchanges (MSDSEs);(g) that it is desirable to employ the same access procedures, service initiation and exchange of controlinformation and characters in all PADs in the maritime satellite service (maritime PADs).Note 1 - The term ma

5、ritime PAD is used for PADs located at or in association with coast earth station in themaritime satellite service designed in accordance with this Recommendation.Note 2 - This Recommendation does not specify PADs to be used on-board ships.unanimously recommends(1) that PADs in the Maritime Satellit

6、e Service (maritime PADs) should meet the requirements of thisRecommendation in order to ensure full compatibility between PADs associated with different coast earth stations ormobile satellite data switching exchanges (MSDSEs) (see Recommendation X.350 for the definition of MSDSE). Thegeneral speci

7、fications of PADs are given in Recommendations X.3, X.28 and X.29;(2) that the maritime PAD shall accept calls from any ship participating in the Maritime Satellite Service.Optionally, the maritime PAD may also offer the capability of setting up calls to ship board start-stop mode DTEs;(3) that mari

8、time PADs shall offer the initial standard profile given in Table 3/X.351;(4) that maritime PADs will in addition offer other standard profiles defined in Recommendation X.28;(5) that the user on board the ship should be advised to place the data call through the maritime PADwhich is nearest to the

9、called subscriber in order to avoid long terrestrial routes;(6) that the protocol should enable access to and from unattended start-stop mode DTEs on-board ships andensure efficient disconnection of the access information path at the end of a virtual call in order to avoid undue holdingof the satell

10、ite circuit;(7) that network user identification (NUI) facility is required for all calls set up from an on-board DTE inorder to avoid fraudulent calls. The format of the NUI facility request signal is defined in Annex A;(8) that maritime PADs may be located as shown in Annex B.2 Fascicle VIII.6 - R

11、ec. X.3511 Procedures for establishing the access information path for ship originated calls1.1 DTE/DCE interfaceThe access information path should be provided by the use of modems standardized for use in the publicswitched telephone network:i) At the rate of 300 bit/s for full duplex operation in a

12、ccordance with Recommendation V.21. Channel No. 1is to be used in the direction from the ship to the PAD and channel No. 2 in the opposite direction. Tonedisabling is required for disabling of echo suppressors.ii) At the rate of 1200 bit/s for full duplex operation in accordance with Recommendation

13、V.22, alternative B,mode ii) with 10 bits per character (i.e. one start bit, eight information bits and one stop bit) 4.2.1 b) ofRecommendation V.22. The handshake procedure should be in accordance with Figure 4/V.22. The shipboard modem shall transmit in the low channel and receive in the high chan

14、nel. The modem of the PADwill have the opposite channel configuration. Tone disabling is required for disabling of echo suppressors.iii) At the rate of 75/1200 bit/s in accordance with Recommendation V.23. The rate of 75 bit/s should be usedfor the direction from the on-board DTE to the PAD and the

15、rate of 1200 bit/s should be used for the otherdirection. Tone disabling is required for disabling of echo suppressors.Note 1 - The alternative given in ii) above is preferred.Note 2 - Administrations may offer other additional data rates at the maritime PAD.The particular interchange circuits provi

16、ded, and their operation, shall be in accordance withRecommendation V.24 and clamping of circuit 104 should be implemented in accordance with Recommendation V.24, 4.3.1.2 Procedures for setting up the access information path by the DTE1.2.1 Setting up the satellite linkThe satellite link is establis

17、hed by using procedures defined within the INMARSAT system.1.2.2 Dialling proceduresThe dialling procedures for setting up telephone circuits in the INMARSAT system is given inRecommendation E.211.Table 1/X.351 gives the dialling sequences which should be used for accessing the maritime PADs using t

18、hemodems given in 1.1.TABLE 1/X.351Dialling information for accessingthe modems defined in 1.1Data signaling rate(bit/s)Dialling sequence300120075/1200200220032011Fascicle VIII.6 - Rec. X.351 3Table 2/X.351 gives the dialling sequences for other data rates of Recommendation X.3 which can be supporte

19、din the existing INMARSAT system. These data rates may be offered on an optional basis.TABLE 2/X.351Dialling information for additionaldata signaling ratesData signaling rate(bit/s)Dialling sequence5075100110134.51502006001 8002 4004 8009 60056 0002010200520092000200120062008200420072012201320142017

20、The dialling sequences 2050 through 2099 are allocated for national use, e.g. access to PADs for specialservices such as videotex.For access to PADs other than maritime PADs, national access procedures and access numbers should be used.The numbering and dialling procedures will then be as defined fo

21、r calling a terrestrial telephone subscriber (see 2.3.1of Recommendation E.211).1.2.3 Routing and digit conversion at the coast earth stationThe routing of calls from the ship earth station to the maritime PAD is as shown in Annex B.There may be a separate input port to the maritime PAD for each dat

22、a rate, or several data rates may be acceptedon one port. The coast earth station will route the call automatically to the appropriate port of the PAD.If the maritime PAD is remotely connected to the coast earth station via the public switched telephone networkcorresponding to case a) of Annex B, th

23、e coast earth station will convert the digits 20X1X2into the appropriatetelephone access number allocated to the required input port of the PAD.1.2.4 Disabling of echo suppressorsEcho suppressors are normally fitted at both ends of the satellite connection. Even though the echo suppressorsin some ca

24、ses may be disabled by signaling means, it is advisable that the disabling tone is sent by the modems wheneverthe access information path is being established.2 Procedures for establishing the access information path for calls originating in a PDNThis point is for further study.3 Procedures for disc

25、onnecting the access information pathProcedures for disconnecting the access information path, i.e. the maritime satellite telephone circuit, are givenin 1.1.3.2 and 1.1.3.4 of Recommendation X.28.4 Fascicle VIII.6 - Rec. X.351Note 1 - Since a maritime satellite telephone circuit is used for accessi

26、ng the maritime PAD, charging of the callmay take place until the circuit has been cleared forward (see the Q.1100 series of Recommendations for the relevantconditions). For calls set up from the on-board DTE, disconnection by the maritime PAD corresponds to clearback on themaritime satellite teleph

27、one circuit. The clearing procedures related to clearback of telephone circuits in the maritimesatellite service are defined in the Q.1100 series of Recommendations.Note 2 - The maritime PAD may be provided with control mechanisms for disconnecting the access informationpath during fault conditions,

28、 for example when no information has been passed between the DTE and the PAD for agiven period of time.Note 3 - When the maritime PAD detects that a clearing condition of layer 3 exists on the interface to the PDNand after the necessary control signals (e.g. the clear indication PAD service signal)

29、have been passed to or receivedfrom the DTE, the PAD should disconnect the access information path.4 Format of characters used in the exchange of control informationThe start-stop mode DTE shall generate and be capable of receiving characters in accordance with InternationalAlphabet No. 5 as describ

30、ed in Recommendation T.50. The general structure of characters should be in accordance withRecommendation X.4.The following specific conditions should apply. The PAD will transmit and expect to receive 8-bit characters,where the 8th bit (i.e. the last bit preceding the stop element) shall be the par

31、ity bit. The maritime PAD will detect theparity from the service request signal.If the transparent mode is selected during the call (see 5.2 below), the PAD will ignore the parity bit and willpass octets transparently between the two interconnected DTEs.The initial standard profile in Table 3/X.351

32、assumes that the even parity is used. However, the maritime PADwill also support the optional parameter values 1, 2 and 3 of parameter 21 (see Recommendation X.3). If the on-boardstart-stop mode DTE requires the use of a specific value for parameter 21, this value should be selected by a set PADcomm

33、and (or a set and read PAD command) signal (e.g. SET 21:3) sent as soon as the PAD identification PAD servicesignal has been received see 5.2.1 ii).It is for further study whether specific standard profiles for maritime applications should be included inTable 3/X.351 for the purpose of parity treatm

34、ent other than that provided with the initial standard profile.5 Procedures for ship originated calls5.1 General5.1.1 Initial standard profile for maritime PADsThe initial standard profile for maritime satellite applications which will be offered in all maritime PADs isgiven in Table 3/X.351.Paramet

35、ers Nos. 1 through 12 and parameter No. 21 will be implemented in all maritime PADs. The remainingparameters may be offered on a national basis.Fascicle VIII.6 - Rec. X.351 5TABLE 3/X.351PAD parameter settings for the initial standard profile for maritime PADsParameterreferencenumberParameter descri

36、ption Parameter setting for standard maritimesatellite profileParameter value1 PAD recall using a character Set to possible 12 Echo Set to no echo 03 Selection of data forwarding signal Set to all characters in column 0 and 1and character DEL1264 Selection of idle timer delay Set to no time-out 05 A

37、ncillary device control Set to no use of X-ON and X-OFF 06 Control of PAD service signal Set to service signals are sent 17 Selection of operation of PAD onreceipt of break signal from thestart-stop mode DTESet to reset28 Discard output Set to normal data delivery 09 Padding after carriage return Se

38、t to no padding after carriage return 010 Line folding Set to no line folding 011 Binary speed of start-stop mode DTE Set to speed of DTE See Rec. X.312 Flow control of the PAD by thestart-stop mode DTESet to use of X-ON and X-OFF 113 Linefeed insertion after carriage return Set to no linefeed inser

39、tion 014 Linefeed padding Set to no padding after LF 015 Editing Set to no editing 016 Character delete Set to character 7/15 (DEL) 12717 Line delete Set to character 1/8 (CAN) 2418 Line display Set to character 1/2 (DC2) 1819 Editing PAD service signals Set to editing PAD service signals forprintin

40、g terminals120 Echo mask Set to echo all characters 021 Parity treatment Set to no parity detection or generation 022 Page wait Set to page wait disabled 05.1.2 Coding of PAD command signals and PAD service signalsThe coding of PAD command signals and PAD service signals are given in Recommendation

41、X.28.6 Fascicle VIII.6 - Rec. X.3515.2 Procedures5.2.1 Figure 1/X.351 shows the sequence of events for call establishment and call clearing for ship originated calls.The following procedures will be supported in maritime PADs for virtual calls set up by the on-board start-stopmode DTE. These procedu

42、res are based on those given in Recommendation X.28, however, where the procedures givenbelow deviate from those given in Recommendation X.28 or where Recommendation X.28 gives several alternativeprocedures, those given below should prevail.i) The procedure should be initiated by the on-board start-

43、stop mode DTE sending a service request signalconsisting of the characters to the PAD.The PAD will detect the parity and, if required, the data rate used from this signal.ii) The PAD will respond within 10 seconds with the PAD identification PAD service signal with thefollowing format:PAD and/or por

44、t identification The signal is the format effector.Fascicle VIII.6 - Rec. X.351 7On receipt of this signal the start-stop mode DTE shall send either:- the selection PAD command signal, or-a set PAD command (or set and read PAD command) signal for setting of specific PAD parametersfollowed by the sel

45、ection PAD command signal, or-a standard profile selection PAD command signal followed by the selection PAD command signal.The format of the selection PAD command signal is given in Annex A.If the NUI facility request signal contained in the selection PAD command signal is not accepted by thePAD, th

46、e PAD will transmit the clear indication PAD service signal and disconnect the accessinformation path.If the first character of the selection PAD command signal has not been received within 60 seconds or thelast character within 120 seconds, the PAD will transmit the error PAD service signal and dis

47、connect theaccess information path.iii) The PAD will acknowledge the selection PAD command signal within 10 seconds with theacknowledgment PAD service signal composed of the characters .iv) When the virtual call has been extended to the called DTE, the PAD will return the PAD service signalto the st

48、art-stop mode DTE. The interface will now be in the data transfer state where charactersmay be transferred using International Alphabet No. 5 except for the character (whichwould be interpreted by the PAD as an escape from the data transfer state) and the characters and (which are used for flow cont

49、rol, see also Recommendation X.28, 4.1).If the start-stop mode DTE would require data to be transferred transparently through the PAD, the DTEshould either send the standard profile selection PAD command signal or the set PADcommand signal as soon as the PAD service signal has beenreceived.Selection of other PAD parameter values should be done in accordance with the procedures given inRecommendation X.28.Note - When the transparent profile has been selected, the start-stop mode DTE will no longer be capableof escaping from the data transfer state and, since no PAD