Re: Telephony API, new version

Hi Hsin-Yi,

On Fri, Mar 29, 2013 at 12:11 PM, Hsin-Yi Tsai <htsai@mozilla.com> wrote:

> The version uses MSISDN as service identifier for cellular telephony.
> However, MSISDN isn't a *mandatory* file on SIM, how would we expect to use
> this as service identifier?
>

Thank you for this question, the concern is totally valid. In certain cases
the MSISDN is not on the SIM card (e.g. prepaid cards that get an MSISDN at
first usage). In such cases there are ways to determine the MSISDN, but
these involve the services (e.g. a USSD session, or WAP request). The SIM
card does have an ID (ICC ID), which can be mapped to the MSISDN and IMSI.

We have discussed this topic, but it needs further discussion since it was
left in a controversial state on the editors meeting between simplicity and
correctness, and was not finished. For instance, if the MSISDN is not
available, the ICC ID could be used and the implementation would map it
later. By the time the SIM card is usable for making or receiving calls, it
has to have the MSISDN. Apps are likely not interested to have the service
exposed through the API before that happens. But such assumptions should be
discussed and perhaps exposed in a note.

However, in other cases multiple SIM cards may actually work with a single
MSISDN, which indeed kills the idea of having service id's covered by
MSISDN. So I am positive about separating the telephony service identifier
from the MSISDN, and have a separate property for fetching the MSISDN (if
available). Since that may involve telephony services, I would even go
further in the design to draft a simple, but extensible TelephonyService
object in a separate spec (I have a proposal for that), but let's do that
on the F2F eventually. We know what needs to be done, the design has been
tested, and also have a proposal on the how, but let's see if we find
consensus about it.

For now, I suggest we remove the constraint, but don't support fetching the
MSISDN through the Telephony API. IMO it should be a functionality exposed
in the (future) separate TelephonyService API.

Best regards,
Zoltan