On Mon, 2012-01-16 at 16:19 -0600, Dan Williams wrote: > On Fri, 2012-01-13 at 11:58 +0100, Marcel Holtmann wrote: > > Hi Aleksander, > > > > > >> 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. > > > > Before everybody goes crazy here you might wanna check if Verizon even > > provides the same IP address when falling back to CDMA from LTE. > > It's supposed to work that way according to the eHRPD docs. I tried to > drivetest this Friday but due to my own stupidity I forgot to take the > modem out of LTE+HRPD mode and into AUTO+eHRPD so I couldn't capture the > handoff and then I ran out of battery. My bad, I'll try again. > > But at least the UE is supposed to make this transparent according to > 3GPP2 X.S0057-A. If the ME already has IP address information from the > network, in the VSNCP Configure-Request packet it sets the Attach-Type > configuration option to "handoff" and includes the existing IP > information (10.1.4.2). > > Section 13 (Handoff from E-UTRAN to eHRPD) states: > > "For optimized handoff, when the UE accesses eHRPD via the E-UTRAN radio > and the S101 tunnel, it shall send a VSNCP Configure-Request message > with Attach-Type set to handover to the HSGW for each of it's existing > PDN connections in the EPS system that it intends to maintain in eHRPD." > > Section 13.1.1 step 7 says: > > "The UI exchanges VSNCP messages with the HSGW for each PDN connection > that it currently has attachments to within E-UTRAN and that it wants to > maintain on eHRPD. The UI sets the Attach-Type to "handoff" in the > VSNCP Configure-Request message. Also, the UI includes the IP > address(es) it obtained via LTE in the VSNCP Configure-Request message."
^^ and here by "UI" I mean "UE", yay for me > See also section 13.1.1 where it details what happens for optimized > handoff; non-optimized handoff is supposed to be the same, more or less. > > So let's assume that the IP address is supposed to stay the same. Next, > the standard talks in various places about separate bearers for EPS and > eHRPD, like 13.2.1: "When the UE returns to eHRPD to resume the existing > eHRPD session, the PDN connections are created per the context that the > UI had on E-UTRAN. Likewise, bearers are established to match those > that were available on E-UTRAN." > > Basically, it appears that bearers may change at various times, but the > IP addresses may stay the same across bearer changes in some cases too. > The problem is that we don't really want to expose that to clients much, > because it's not really that useful to know that bearers are dancing > around. You really just want to know if one of your existing bearers > *changed* attributes like IP addressing or QoS/TFT, since the modem and > network appear to do all they can to maintain characteristics between > E-UTRAN and eHRPD. I also still don't know how these changes are > presented via AT, WMC, or QMI, and how much of this the modem does > internally and hides from these interfaces but I'm still trying to > figure out. Unfortunately the end of my LTE coverage is about 30+ > minutes away in all directions... > > Dan > > > _______________________________________________ > networkmanager-list mailing list > [email protected] > http://mail.gnome.org/mailman/listinfo/networkmanager-list _______________________________________________ networkmanager-list mailing list [email protected] http://mail.gnome.org/mailman/listinfo/networkmanager-list
