On Wed, 2012-01-11 at 17:29 +0100, Aleksander Morgado wrote: > Hey, > > 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. So I think (as you suggest below) that by default MM should make a best guess based on the current registration of the device and the mode preference. If you're registered on the LTE network and your mode pref is 4G_PREFERRED then of course we'd start an EPS bearer. If your mode pref is 3G_4G and you're registered with CDMA then we'd try to start a CDMA bearer. There are some carrier-specific issues with this however; an ATD#777 CDMA PPP bearer cannot hand off to LTE on Verizon devices, but handoff is supposed to be transparent when you use QMI instead of PPP. What you're asking about is what bearer to create if the device is registered with (or can register with) two 3G networks that use different access technology. For example, in Canada, Bell Mobility and Telus run both EVDO and HSPA networks. If you're a user, do you care which one you connect to with your Gobi card? Maybe you do. So the bearer type property should certainly be a *suggestion*, not mandatory. At least for now I don't think most people will use it, but it doesn't hurt anything to add it. But the next question is if you request a 3GPP bearer and the device later hands off to CDMA, do you terminate the connection? I would say no, since the device is making the decision to hand off based on your subscriber data (ie, SIM and/or ESN/MEID) and that's supposed to be automatic. > On a side note, during the Simple interface's Connect(), for the case of > mixed 3GPP+CDMA modems, we would create both a 3GPP and a CDMA bearer, > and then connect one or the other based on allowed/preferred modes > preferences and based on our registration status in each network. Seems > like a good start for the generic case. Yeah, though handoffs complicate that, since the bearer might not stay a 3GPP bearer or a CDMA bearer. This probably complicates the code a bunch and I didn't think of this problem until you asked the question. So maybe bearer objects need to be "soft" classes too, like modems, that can change some details of their implementation on-the-fly? The only post-initialization bearer stuff that might be 3GPP specific is the secondary PDP/EPS context and the QoS stuff, but here maybe we can just return errors if the bearer doesn't support it. Besides the initial hint, I don't know if we want to expose whether the bearer is CDMA or 3GPP to clients at all. The access technology of the modem indicates the network type, so the bearer probably doesn't need to do it too. Dan _______________________________________________ networkmanager-list mailing list networkmanager-list@gnome.org http://mail.gnome.org/mailman/listinfo/networkmanager-list