Recommendation X.352

    INTERWORKING BETWEEN PACKET SWITCHED PUBLIC DATA NETWORKS
 AND PUBLIC MARITIME MOBILE SATELLITE DATA TRANSMISSION SYSTEMS


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2.     References

I.112       Vocabulary of terms for ISDNs,

I.210       Principles of telecommunication services supported by an ISDN,

I.230-SeriesBearer Services supported by an ISDN,












I.240-SeriesTeleservices supported by an ISDN,

I.250-SeriesDefinitions and description of Supplementary Services,

I.340       ISDN connection types,

I.411       ISDN user-network interfaces - Reference configuration,

I.420       Basic user-network interface,

I.421       Primary rate user-network interface,

I.500/I.510 Definitions and general principles for ISDN interworking,

Q.700-SeriesSpecifications of Signalling System No. 7,

X.1         International user classes of service in public data
            networks (PDNs) and ISDNs,

X.2         International data transmission services and optional user
            facilities in PDNs,

X.10        Categories of access for data terminal equipment to public data 
transmission services,

X.20         



2.2    A public maritime mobile earth station calling another
       mobile earth station

       If the two public maritime mobile earth stations are in the same ocean area 
or are in different ocean areas covered by the same MSDSE, the MSDSE sets up the 
call directly to the called public maritime mobile earth station so that only one 
MSDSE will be involved in the call.





       If the two public maritime mobile earth stations are in different  ocean
areas which are not both covered by the same MSDSE, the calling MSDSE will route 
the call in accordance with  2.1 above.






defined within the public maritime mobile-satellite systems. Such abbreviated codes 
require conversion to the full international data number before the call can be 
forwarded from the MSDSE to a PDN.




3.     Routing of land originated calls to public maritime mobile






       earth stations






       Further, the first digit of the following Network Terminal Number in the 
public maritime mobile-satellite system is the "T" digit defined in Recommendation 
E.215/F.125 which is used for discrimination between different public  maritime
mobile-satellite systems.               

       A calling user can only indicate which ocean area  and  public  maritime
mobile-satellite systems (such as INMARSAT Standard A, B and C), type is addressed, 
and cannot select a specified MSDSE. Therefore each originating and/or  transit
network has normally to route data calls within one of the public maritime mobile 
system DNICs to a pre-determined MSDSE which serves the ocean area and system type 
as indicated by the DNIC and T digital according to bilateral agreement between the 
administration of origin and the administration operating the MSDSE. Thus, analysis 
of five digits of the called number is required for routing purposes.


another data number (but to the same public maritime mobile earth station), which 
only differs in ocean area, when a mobile earth station is absent from the ocean 
area indicated by the original data number. The re-routing of a call between the 
two ocean areas covered by the MSDSE should be carried out only once.

       The condition for re-routing is that the public  maritime  mobile  earth
station is included in the list of mobile earth stations and is not barred from 
incoming access.




existing X-Series Recommendations and to the public  maritime  mobile-satellite
system specifications and is therefore left for further study.


Recommendation E.215/F.125 should be barred. Such addresses are public maritime 
mobile earth station numbers with a T digit 0. The call should preferably be barred 
in the network of origin. However, the MSDSE must in any case be capable of barring 
such calls. (See also Recommendation X.350).


       The link between the coast earth station and a public maritime mobile earth 
station is always a satellite link.


       Hence, for a call destined to a public maritime mobile earth station, all 
transit exchanges should recognize from the destination DNIC of 111S that the final 
link is a satellite link and perform routing so that the maximum permitted transit 
delay from the calling user to the called user is not exceeded.