22.0793GPPService definitionStage 1Support of Optimal Routeing (SOR)TS
Administrative PLMN: The complete set of all functional entities normally regarded as a single PLMN.
Basic OR : Routeing of a call by the direct route when no forwarding occurs.
Direct route: A call uses the direct route if it is routed from the serving network of the original calling party to the serving network of the ultimate called party without any intermediate PLMN.
HPLMN route: A call uses the HPLMN route if the destination is deduced from the MSISDN of the called party. This forces the call to be routed via the HPLMN of the called party.
HPLMN leg: The HPLMN leg is that part of the HPLMN route from the IPLMN to the HPLMN of the called party.
IPLMN: An IPLMN is a PLMN which interrogates the HPLMN of a called party in order to determine the whereabouts of that party.
Early Call Forwarding : Early Call Forwarding is Call Forwarding performed from the IPLMN before the call has been extended to the VPLMN of the forwarding subscriber (i.e. Call Forwarding Unconditional and Conditional Call Forwarding on Not Reachable known at the IPLMN before extension of the call)
Functional PLMN: For the purposes of this description the Administrative PLMN is divided into functional PLMNs that represent different aspects of the Optimal Routeing functionality.
Late Call Forwarding: Late Call Forwarding is Call Forwarding performed after the call has been extended to the VPLMN of the forwarding subscriber (i.e. Conditional Call Forwarding on Busy, Conditional Call Forwarding on No Reply and Conditional Call Forwarding on Not Reachable detected in the VPLMN of the forwarding subscriber). Late Call Forwarding may be invoked in the IPLMN or in the VPLMN of the forwarding subscriber.
Special mobile network number: For the purposes of this description special mobile network numbers are numbers belonging logically to a PLMN but not to a mobile subscriber. Examples are the customer service number or value added service numbers.
Abbreviations are given in TR 21.905 .