There’s quite a lot of flexibility there.

thanks for the explanation guess, if at all, we get a protocol log of Apple phone, it would be great!

MMS also uses the same notify-with-pointer-to-real content delivery method. The “push” notification is still just a “special” SMS message. Without knowing anything about the internals of AT&T;’s network(*), the difference between implementing visual voicemail as MMS vs. EVMI doesn’t seem that great: Either way, and only if you want voicemail delivery to the device without a voice call, you need a non-voice – probably HTTP – front end to the voicemail store. Doing it with MMS saves you from implementing EVMI in the voicemail/SMSC interface so maybe that’s what they did.

(*) except observing as a user that their – or their international gateway’s – SMSCs have issues with some non-english characters in the GSM alphabet and – as of some time ago – severe bugs with multi-PDU SMS

MMS also uses the same notify-with-pointer-to-real content delivery method. The “push” notification is still just a “special” SMS message. Without knowing anything about the internals of AT&T’s network(*), the difference between implementing visual voicemail as MMS vs. EVMI doesn’t seem that great: Either way, and only if you want voicemail delivery to the device without a voice call, you need a non-voice – probably HTTP – front end to the voicemail store. Doing it with MMS saves you from implementing EVMI in the voicemail/SMSC interface so maybe that’s what they did.

(*) except observing as a user that their – or their international gateway’s – SMSCs have issues with some non-english characters in the GSM alphabet and – as of some time ago – severe bugs with multi-PDU SMS

Thanks for the detailed explanation. Yes, infact the main point which i am still pondering over is, how IPhone retrieves the voicemail message and stores in the phone. Because i am not sure whether AT&T would’ve modified /added any changes in the network side for this feature apart from the octet info mentioned in 3GPP Spec for SMS. So if we assume that there are no network side changes, then can it be possible for the voicemail server to directly send the voicemail messages as MMS to the phone?

thanks

If the Enhanced Voice Mail Information feature is being used, then what’s probably happening is that the EVMI SMS is being used as the “push” notification that there is a voicemail state change. That contains the calling line ID of the voicemail sender (VM_MESSAGE_CALLING_LINE_IDENTITY), so you can match that to the contact database and drive the “visual voicemail” display.

EVMI also contains a VM_MESSAGE_ID field, so one can envision a “web service” (using the term loosely) API to the voicemail servers which takes that ID as a parameter. The iPhone can then invoke that API and retrieve the messages.

Of course the above is all a guess. But if one could examine the SMS PDU received by the iPhone when new voicemail is available, it might shed some light. Unfortunately that requires warranty-voiding surgery, as you have to remove the iPhone SIM and put it in a GSM device that gives you access to the PDUs (most of them do).

Hmm… Come to think of it, maybe, just maybe, the iPhone does too. I’d be surprised, but it’s not impossible. One of these days I should go to the local Apple store and do some Bluetooth poking

The point is that this is hardly earth-shattering stuff, technically.

If the Enhanced Voice Mail Information feature is being used, then what’s probably happening is that the EVMI SMS is being used as the “push” notification that there is a voicemail state change. That contains the calling line ID of the voicemail sender (VM_MESSAGE_CALLING_LINE_IDENTITY), so you can match that to the contact database and drive the “visual voicemail” display.

EVMI also contains a VM_MESSAGE_ID field, so one can envision a “web service” (using the term loosely) API to the voicemail servers which takes that ID as a parameter. The iPhone can then invoke that API and retrieve the messages.

Of course the above is all a guess. But if one could examine the SMS PDU received by the iPhone when new voicemail is available, it might shed some light. Unfortunately that requires warranty-voiding surgery, as you have to remove the iPhone SIM and put it in a GSM device that gives you access to the PDUs (most of them do).

Hmm… Come to think of it, maybe, just maybe, the iPhone does too. I’d be surprised, but it’s not impossible. One of these days I should go to the local Apple store and do some Bluetooth poking

The point is that this is hardly earth-shattering stuff, technically.

As per the spec, only the pdu information are mentioned. There is no specific information as whether the audio (corresponding to voicemail msg) is transferred as part of the SMS and also no octets specified for the same. Is there any other section in the spec which talks about this?

thanks

It would be interesting to inspect a voicemail notification SMS on AT&T;’s network, both for an iPhone account and for a non-iPhone account, to see if they’ve enabled this on all accounts, just iPhone accounts, or if they rolled their own protocol.

I wonder if this is one of the items of intellectual proper-taah that Jobs said would be vigorously defended during the iPhone unveiling.

It would be interesting to inspect a voicemail notification SMS on AT&T’s network, both for an iPhone account and for a non-iPhone account, to see if they’ve enabled this on all accounts, just iPhone accounts, or if they rolled their own protocol.

I wonder if this is one of the items of intellectual proper-taah that Jobs said would be vigorously defended during the iPhone unveiling.