Re: Bearers in mixed CDMA+LTE modems

[Aleksander Morgado <aleksander lanedo com>]

>>>>>> I believe we need a MMBearerType enum in the 0.6 API, so that we can
>>>>>> tell in CreateBearer() whether we want a 3GPP or CDMA (well, or POTS)
>>>>>> bearer. This property would be redundant for 3GPP-only, CDMA-only or
>>>>>> POTS-only modems, but would be mandatory if we have a mixed
>>>>>> 3GPP(LTE)+CDMA bearer. This value would also be shown as a property in
>>>>>> the Bearer interface, so that we can know the type of the bearer behind
>>>>>> a given DBus path. Another possibility to avoid the new enum would be to
>>>>>> assume that if "apn" is given when creating the bearer, we want a 3GPP
>>>>>> bearer, while if no "apn" is given we really want a CDMA bearer. But not
>>>>>> sure I like to rely just on this "apn"-based logic. What do others think?
>>>>>
>>>>> The problem with that approach is handoffs.  If you create a 3GPP/LTE
>>>>> bearer and then leave LTE coverage where the device hands off to EVDO,
>>>>> now your 3GPP bearer is a CDMA bearer.  In this scenario there's no
>>>>> interruption of packet data service and you don't even know anything
>>>>> happened except that the access technology changed from LTE to EVDO.
>>>>
>>>> Well, that is already some indication that we can use. If we had a 3GPP
>>>> bearer connected, and suddenly the access technology changed to EV-DO,
>>>> then we could internally mark the CDMA bearer as connected and mark the
>>>> 3GPP one as disconnected. If done in that order, we wouldn't be issuing
>>>> any state change notification. This, assuming that for mixed technology
>>>> modems we have different technology-specific bearers. The only drawback
>>>> of having technology-specific bearers is that for the user not using the
>>>> Simple interface, it would mean needing to create two bearers with two
>>>> CreateBearer() calls. But I don't think that that is a big deal; if the
>>>> user of a mixed CDMA+LTE modem just creates a 3GPP bearer and gets it
>>>> connected, and then we detect the connection handed off to CDMA, we can
>>>> request the disconnection of the bearer and that's it. If the user
>>>> didn't create a CDMA bearer, we would need to assume she didn't want a
>>>> CDMA connection. If using the Simple interface, all that would be
>>>> automatic, different bearers would be created automatically.
>>>
>>> there is no guarantee that the IP connection details stay the same.
>>
>> There is no IP connection detail stored in the ModemManager bearers, so
>> that wouldn't be a big deal for us I guess. Maybe I'm missing something.
> 
> Except for Static mode :)
> 

Indeed, yes. Which reminds me I need to allow subclasses of the bearers
to report the static IP addresses.

-- 
Aleksander