H.460.20 consented at the last Study Group 16 meeting solves the problem of how
to provide location information in calls generated to/from H.323 systems. The
Recommendation allows these systems – such as VoIP or videoconferencing – to
convey information that could be a URL, an e-Mail, a postal code, or a mobile
telephone number. This is much more than can be achieved with a traditional
public switched telephone network (PSTN) call.
Currently calls generated or terminated in H.323 systems do not carry -
end-to-end – details of where that call is coming from. This information is
needed by the public switched telephone network (PSTN) for emergency services,
more accurate billing and for routing the call. Additionally it is useful, for
instance, in applications such as telemarketing where calls can be routed
according to their origin.
Technically H.460.20 gives H.323 the ability to convey the location number
present in ISUP – the system that determines the set-up, co-ordination and
taking down of calls. Without this ability location information is lost at the
interworking edge between the IP network and the PSTN. An additional benefit is
that it simplifies interworking with the session initiation protocol (SIP).