1、INTERNATIONAL TELECOMMUNICATION UNION)45G134 8 TELECOMMUNICATIONSTANDARDIZATION SECTOROF ITU).4%27/2+).G0G0“%47%.G0G0.%47/2+3-/“),%G0G0$!4!G0G042!.3-)33)/.G0G03934%-32/54).G002).#)0,%3G0 amended at Melbourne, 1988)The CCITT,considering(a) that a Public Maritime Mobile Satellite Service is now being
2、operated by the International MaritimeSatellite Organization (INMARSAT);(b) that the mobile subscribers may have access to the service through a number of coast earth stations locatedin different countries;(c) that interworking between the mobile satellite data transmission systems and the public da
3、ta networks isrequired;(d) that Recommendation X.110 specifies routing principles for international data services,Recommendation X.121 specifies the international numbering plan for public data networks andRecommendation E.215/F.215 provides for internationally unique mobile earth station identifica
4、tion;(e) that new mobile systems for maritime and aeronautical applications are being defined,unanimously recommendsthat the following routing principles should apply for setting up calls between subscribers of the public datanetworks and users of international public maritime mobile satellite data
5、transmission systems.1 General1.1 DefinitionsFigure 1/X.353 shows the composition of systems in the Public Maritime Mobile Satellite Service. Fordefinition of the various elements see Recommendation X.350.The mobile satellite data switching exchange (MSDSE) is defined in 1.7 of Recommendation X.350.
6、1.2 Role of the MSDSEA MSDSE will at the same time act as an international gateway and as an interface to the mobile earth stations.Within an ocean area a public maritime mobile earth station may set up or receive data calls from any MSDSE in thatregion. Each ocean area may contain a number of MSDSE
7、s.One MSDSE may have access to more than one satellite, and thus may serve more than one ocean area.One MSDSE may serve one or more public maritime mobile systems.The MSDSE may be connected to more than one international data switching exchange (IDSE) in a PDN. TheMSDSE may also be connected to IDSE
8、s in different PDNs.This Recommendation assumes that a PDN does not connect to more than one MSDSE serving the same oceanarea and Public Maritime Mobile Satellite System (such as INMARSAT Standard A, B and C).2 Fascicle VIII.6 - Rec. X.3532 Routing of mobile earth station originated calls2.1 A publi
9、c maritime mobile earth station calling a land network subscriberThe mobile earth station selects one MSDSE in the ocean area by signalling procedures defined within themobile satellite service. The mobile user should be advised to place the call through an MSDSE which is near to thecalled subscribe
10、r in order to avoid long terrestrial routes.The public maritime mobile earth station subscriber provides the international data number of the calledsubscriber to the MSDSE which will forward the call through its associated IDSE (or through the most appropriate IDSEif the MSDSE is connected to more t
11、han one IDSE).2.2 A public maritime mobile earth station calling another mobile earth stationIf the two public maritime mobile earth stations are in the same ocean area or are in different ocean areascovered by the same MSDSE, the MSDSE sets up the call directly to the called public maritime mobile
12、earth station sothat only one MSDSE will be involved in the call.Note - If the MSDSE does not have full switching capability, the call will first be routed to its associated IDSEand then back again to the MSDSE.If the two public maritime mobile earth stations are in different ocean areas which are n
13、ot both covered by thesame MSDSE, the calling MSDSE will route the call in accordance with 2.1 above.2.3 Routing of special service requestsCertain services (e.g., access to data bases for navigational warnings, weather forecasts, etc.) may be accessedby use of special short number codes defined wit
14、hin the public maritime mobile satellite systems. Such abbreviated codesrequire conversion to the full international data number before the call can be forwarded from the MSDSE to a PDN.Fascicle VIII.6 - Rec. X.353 32.4 Information provided to mobile earth stationsAdministrations operating MSDSEs sh
15、ould prepare and maintain information for mobile earth stations withregard to the administrations routing capabilities towards various destinations.3 Routing of land originated calls to public maritime mobile earth stations3.1 Routing principlesAccording to Recommendation X.121, one DNIC is allocate
16、d for each ocean area. The structure of these DNICsis 111S where S specifies the ocean area. The values assigned are found in Recommendation X.121.Further, the first digit of the following Network Terminal Number in the public maritime mobile-satellite systemis the “T“ digit defined in Recommendatio
17、n E.215/F.125 which is used for discrimination between different publicmaritime mobile satellite systems.A calling user can only indicate which ocean area and public maritime mobile satellite systems (such asINMARSAT Standard A, B and C) type is addressed, and cannot select a specified MSDSE. Theref
18、ore each originatingand/or transit network has normally to route data calls within one of the public maritime mobile system DNICs topredetermined MSDSE which serves the ocean area and system type as indicated by the DNIC and T digit according tobilateral agreement between the administration of origi
19、n and the administration operating the MSDSE. Thus, analysis offive digits of the called number is required for routing purposes.Similar agreements need to be made with administrations operating transit networks which will be involved inestablishing the connection.Situations may arise when two admin
20、istrations are using the same transit network for routing their calls to twodifferent MSDSEs within the same ocean area, i.e., two MSDSEs with the same DNIC and T digit. This will be solvedby routing the call according to the DNIC of the administration of origin.3.2 Routing on facility field informa
21、tionIf the MSDSE (or the associated transit network) does not provide for a given facility, the administration maychoose to set up calls requesting such a facility via another MSDSE or transit network than that normally used by theadministration rather than barring the call.3.3 Re-routing of calls a
22、t the MSDSEMSDSEs that have access to two satellites may have the capability of re-routing calls between the coverageareas of the two satellites. The re-routing of calls by the MSDSE enables a land user to have calls re-routed to anotherdata number (but to the same public maritime mobile earth stati
23、on), which only differs in ocean area, when a mobileearth station is absent from the ocean area indicated by the original data number. The re-routing of a call between the twoocean areas covered by the MSDSE should be carried out only once.The condition for re-routing is that the public maritime mob
24、ile earth station is included in the list of earthstations and is not barred from incoming access.The DNIC to be returned as part of the called line identification, or whether a called line identification should bereturned in such cases, is for further study.General re-routing of calls based on the
25、information contained in a mobile satellite location register is desirable.This may require changes to existing X-Series Recommendations and to the public maritime mobile satellite systemspecifications and is therefore left for further study.Note - See also 3.1.4 Group callsIn general, calls with a
26、group address (as defined in Recommendation E.215/F.125) should be barred. Suchaddresses are public maritime mobile earth station numbers with a T digit 0. The call should preferably be barred in thenetwork of origin. However, the MSDSE must in any case be capable of barring such calls. (See alsoRec
27、ommendation X.350.)4 Fascicle VIII.6 - Rec. X.3535 Use of satellite linksThe link between the coast earth station and a public maritime mobile earth station is always a satellite link.To provide acceptable Quality of Service, a limited number of satellite links should be permitted on a dataconnectio
28、n. (See Annex B to Recommendation X.110.)Hence, for a call destined to a public maritime mobile earth station, all transit exchanges should recognize fromthe destination DNIC of 111S that the final link is a satellite link and perform routing so that the maximum permittedtransit delay from the calling user to the called user is not exceeded.Note - The mechanism for a transit network to determine the transit delay already experienced in setting-up acall is for further study.
