1、INTERNATIONAL TELECOMMUNICATION UNION)45G134 b) to standardize the procedures for calling subscribers of a PDN from ship earth stations using the packetswitched data transmission service defined in Recommendations X.25 and X.352;c) to standardize the procedures for calling subscribers of a PDN from
2、ship earth stations by accessing packetassembly/disassembly facilities (PAD) as defined in Recommendation X.351.Note 1 - This Recommendation does not cover data calls passed through the international public switchedtelephone network other than those which are accessed through PADs designed in accord
3、ance with RecommendationX.351.Note 2 - Procedures for subscribers of a PDN calling a ship earth station by accessing a PAD are for furtherstudy.1.2 Related CCITT Recommendations are:E.200/F.110 Operational provisions for the maritime mobile service.E.210/F.120 Ship station identification for VHF/UHF
4、 and Maritime Mobile-Satellite Services.E.215 Telephone/ISDN numbering plan for the Mobile-Satellite Service of INMARSAT.E.216 Selection procedure for the INMARSAT mobile-satellite telephone and ISDN services.F.125 Telex numbering plan for the Mobile-Satellite Service of INMARSAT.F.126 Selection pro
5、cedures for the INMARSAT Mobile-Satellite Telex Service.X.1 International user classes of service in public data networks and ISDNs.X.2 International data transmission services and optional user facilities in public data networks.X.96 Call progress signals in public data networks.X.121 International
6、 numbering plan for public data networks.X.180 Administrative arrangements for international closed user groups (CUGs).X.300 General principles and arrangements for interworking between public data networks, and between public data networks and other public networks.X.350 General interworking requir
7、ements to be met for data transmission in the internationalpublic mobile satellite systems.X.351 Special requirements to be met for packet assembly/disassembly facilities (PADS) located ator in association with coast earth stations in the Maritime Satellite Service.X.352 Interworking between packet
8、switched public data networks and the public maritime mobile satellite data transmission system.X.353 Routing principles for interworking public maritime mobile satellite data transmission systems in the public data network.1.3 The following basic considerations were taken into account when formulat
9、ing this Recommendation:a) Each ship is allocated a unique 9-digit INMARSAT mobile number.Note - The first generation maritime mobile satellite (INMARSAT) system also caters for a 7-digitINMARSAT mobile number beginning with digit 1.b) The routing principles to be used for data transmission to and f
10、rom ships are as defined inRecommendation X.353.2 Fascicle II.4 - Rec. F.122c) The procedures to be used on board ships when accessing a subscriber of a PDN should be as similar aspossible to the procedures used on PDNs.d) The Maritime Satellite Service is international in nature and international p
11、rocedures will be adopted toprovide access to this service. For some purposes, a maritime satellite data transmission system can beregarded as analogous to a national network and the ship earth stations as subscribers within that network.e) The procedures used on board the ship when accessing a subs
12、criber of a PDN should be the same in allcoast earth stations.1.4 The following basic access methods are defined for the Maritime Satellite Data Transmission Service:a) access using the packet mode in accordance with draft Recommendation X.352;b) access using packet assembly/disassembly facilities (
13、PADS) in accordance with Recommendation X.351.1.5 Ships may form part of a closed user group (CUG) in accordance with Recommendation X.180. It should benoted that a ship being part of a CUG should be known as such in all coast earth stations.The International Maritime Satellite Organization (INMARSA
14、T) should be charged with the responsibility ofacting as the coordinating Administration (see Recommendation X.180) for ship earth stations wanting to form CUGS.The application from ships to join or cease membership of a CUG should be forwarded through INMARSAT whoshould then inform the coordinating
15、 Administration of the CUG in accordance with Recommendation X.180.For each CUG the same index identifying the CUG by a calling ship earth station (see Recommendation X.300)should be used in all coast earth stations in order to simplify the calling procedures. The index should be coordinatedthrough
16、INMARSAT.1.6 Permanent virtual circuits (PVC) would require a permanent circuit between a ship earth station and the coastearth station. The PVC service should not normally be offered to ship earth stations (see also Recommendations X.2and X.350).2 Procedures for ship originated calls2.1 Access to p
17、acket switched PDNs2.1.1 Calling a subscriber of a PDN2.1.1.1 The coast earth station through which the call is to be set up is selected by procedures defined within theINMARSAT system.2.1.1.2 The ship board subscriber should select a prefix followed by the full international number of the called DT
18、E.Hence, the numbering sequence selected by a ship board subscriber will be as shown in Table l/F.122 or, where anintegrated numbering system exists within a country, as shown in Table 2/F.122.TABLE 1/F.1220 PrefixDNIC Data network identification codeN1. NnNetwork terminal numberFascicle II.4 - Rec.
19、 F.122 3TABLE 2/F.1220 PrefixDCC Data country codeN1. NnNational data numberSee also Recommendations X.121 and X.350.2.1.1.3 The calling DTE address of the ship board DTE should always be inserted and have the following format:TX1, X2. X8Ywhere TX1, X2. X8is the INMARSAT mobile number as defined in
20、Recommendation F.125 and Y is an optionaldigit identifying a specific DTE on board the ship. If the ship is equipped with only one DTE, the digit Y should beomitted. The calling DTE address should not include the prefix and the DNIC allocated to the ocean area in which theship earth station is locat
21、ed at the time of the call.2.1.1.4 Selection of facilities on a call-by-call basis should be in accordance with Recommendations X.25 and X.300.The facilities that may be offered on a call-by-call basis are given in Recommendation X.2. A given facility may not beoffered in all coast earth stations.Us
22、er facilities that have to be agreed for a contractual period are also listed in Recommendation X.2. Theapplication for a given facility should be made with the Administrations operating coast earth stations providing accessto public packet switched data networks. The availability of user facilities
23、 on the various coast earth stations should becoordinated and be disseminated to ships by INMARSAT; however, the decision to implement a given user facilityshould be made by each coast earth station owner.Further study is required to determine which user facilities and/or other user parameters shoul
24、d be offered onall coast earth stations.Note - Separate provisions apply to closed user groups as described in 1.5 above.2.1.2 Use of data transmission prefixes2.1.2.1 Annex A to Recommendation F.126 defines data transmission prefixes for accessing special terminations. Thegeneral called DTE address
25、 format when accessing such a termination will be as shown in Table 3/F.122.TABLE 3/F.122P1 P2Two-digit prefix defined in Annex A to Recommendation F.126A1 . AkOptional digitsOptional digits may be a data country code (DCC), a data network identification code (DNIC) or otheradditional digits.2.1.2.2
26、 The calling DTE address should have the format defined in 2.1.1.3 above.2.1.2.3 Selection of facilities, if required, should be as defined in 2.1.1.4 above.2.1.2.4 The use of some prefixes could be barred to some customers.2.1.2.5 The prefix will be sent on the radio path to the coast earth station
27、 but would not be used outside the satellitesystem. The prefix will be converted at the coast earth station, if required, to the data number associated with theappropriate destination.4 Fascicle II.4 - Rec. F.1222.1.3 Ship-to-ship callsFor ship-to-ship calls the called DTE address should have the co
28、mposition shown in Table 4/F.122.TABLE 4/F.1220 Prefix111S DNIC allocated to the Martitime Satellite ServiceTX1X2. X8INMARSAT mobile numberY Optional digit to designate a particular DTEThe digit S determines the ocean area in which the called ship is located. The values for the digit S are given inR
29、ecommendation X.121. The digit Y identifies a specific DTE on board the ship.2.1.4 Call progress signals and diagnostic codesCall progress signals and diagnostic codes may be received in accordance with 8.2 of RecommendationX.350.2.1.5 CCITT standardized servicesShips should have full access to CCIT
30、T standardized services offered on public data networks such as Teletex,Videotex, and facsimile in accordance with relevant F and S Series Recommendations.2.2 Access to PADs2.2.1 Ships with start-stop mode DTEs may be offered access to packet switched public data networks throughPADs.PADs associated
31、 with coast earth stations are defined in Recommendation X.351. These PADs are defined insuch a way that identical procedures may be used when working towards PADs located at different coast earth stations.Note - Ships may also access a national PAD in a country, but in such cases special procedures
32、 only applicablefor that PAD would be required. Only PADs designed in accordance with Recommendation X.351 are considered inthis Recommendation.2.2.2 Telephone access procedureThe coast earth station at which the PAD is located is selected in accordance with INMARSAT procedures fortelephone calls. T
33、he start-stop mode DTE on board the ship would use telephone procedures in order to access a PAD.When the telephone circuit has been established, i.e. when the dial tone is heard, the following digits have to be dialled:20 PrefixX1 X2Digits indicating required data rateRecommendation X.351 specifies
34、 that the following data rates and types of modem for full duplex operationwill be supported by the PAD:- Recommendation V.21, 300 bit/s;- Recommendation V.22, 1200 bit/s;- Recommendation V.23, 75/1200 bit/s.The specific modes of operation of the modems are given in Recommendation X.351, 1.1.The num
35、ber to be dialled for each of these data rates is given in Table 5/F.122.Fascicle II.4 - Rec. F.122 5TABLE 5/F.122Data rate (bit/s) Dialling sequence300 20021200 200375/1200 2011The PAD may support other data rates on an optional basis. For such data rates the dialling information will beas given in
36、 Table 2/X.351.The dialling sequences 2050 through 2099 are reserved for national use and may be used for access to forexample Videotex data bases via the PAD.2.2.3 Data access proceduresThe call control procedures to be used during set-up and clearing of the data connection and the data transferpro
37、tocol are given in Recommendation X.351.The basic elements of the procedure are:First the DTE accesses the PAD by sending a service request signal consisting of the characters “.” (full stop)and “CR” (carriage return) corresponding to the characters 2/14 0/13 of International Alphabet No. 5 (seeReco
38、mmendation T.50 for a description of International Alphabet No. 5.The PAD will respond by returning a PAD identification signal, the composition of which is left to theAdministration operating the PAD.The DTE shall then send, as soon as possible, a signal, i.e. a string of characters, called the sel
39、ection PADcommand signal. This signal is composed as shown in Annex A. The purpose of this signal is: to provide the PAD with the address of the called DTE; and to provide the PAD with the identity of the calling DTE.When the call has been extended to the called DTE, the character string COM will be
40、 received from the PAD.At this stage the system enters into the data transfer phase.The call set-up procedure outlined above may be operated manually or be programmed into the DTE.During call set-up and during the data transfer phase, the DTE may receive PAD service signals as defined inRecommendati
41、on X.28. These signals may indicate various call failures.Recommendation X.351 also allows other procedures to be used during call set-up. See that Recommendationfor further details.2.2.4 Standard profile and profile selectionIn order to operate a PAD, a number of PAD parameters must be specified. A
42、 general list of PAD parametersis contained in Recommendation X.3.The PAD defined in Recommendation X.351 offers an initial standard profile with PAD parameter values asgiven in Table 3/X.351. This standard profile permits a data transfer protocol based on International Alphabet No. 5.The characters
43、 1/0 (DLE), 1/1 (DC1) and 1/3 (DC3) are used for control purposes and can therefore not bepassed transparently through the PAD. The character 1/0 (DLE) is interpreted by the PAD as an escape from the datatransfer phase. Therefore, this character is used in order to enable commands to be sent to the
44、PAD. For the variouscommands that can be used during the data transfer phase, see Recommendation X.28.The initial standard profile offers the following capabilities: by using the character 1/0 (DLE) commands can be sent to the PAD; the PAD can at any time send service signals to the DTE;6 Fascicle I
45、I.4 - Rec. F.122 the DTE can use characters in order to indicate when a data packet shall be sent from the PAD into the datanetwork; the DTE may use the characters 1/1 (DC1) and 1/3 (DC3) for flow control.The profile does not permit the PAD to provide for any editing functions. Characters which are
46、entered into thePAD are not echoed to the DTE. This has been done because the echoed character will be delayed by approximately0.6 seconds, thus reducing the character rate to less than two characters per second. The echo mode should thereforenot be used. If echo is required, it should be generated
47、locally in the DTE.A transparent profile or any other profile standardized in Recommendation X.28 may be selected as soon as thedata transfer phase is entered by procedures defined in Recommendations X.28 and X.351. The transparent profile willallow octets of data to be passed transparently between
48、the two DTEs. When operating in this mode, the on-boardDTE cannot recall the PAD, nor can the PAD send any service signals to the on-board DTE. Therefore, a data transferprotocol must exist between the two DTEs for proper call control.The various PAD parameters which can be selected by the DTE are g
49、iven in Recommendation X.3. It should benoted that some of these parameters may not be implemented on all PADS.Since DTEs may treat the parity bit included in the data octets differently when International Alphabet No. 5 isused, Recommendation X.351 specifies the means by which this problem can be resolved.2.2.5 Clearing of callsAt the end of the call the user at the on-board DTE should make sure that the satellite telephone circuit isproperly cleared. The PAD may include provisions for clearing the circuit but this may delay the clearing for severalminutes. During this time, t
