Let's talk about APNs again


    I could use a little clarity from the technical community here, if possible.

    APNs are a common source of confusion, as we can witness through any number

    of threads on phone forums around the internet.


    My phone, a generic BYOD Android, has a "default" APN which I could see once

    I popped the T-Mo SIM into it -- the standard setup via "fast.t-mobile.com",

    and the MMS server at mms.msg.eng.t-mobile.com/mms/wapenc like almost

    every searchable resource advises us to set.


    Then shortly after establishing service and getting on the cell network,

    a "configuration message" arrived via SMS, containing a somewhat different

    APN which I had the option to "install" from the special display screen

    it shows up on.  It's in separate parts specified by "Application", with

    one specifically for MMS and another for "default", and between those

    it specifies almost the same settings except that it has PAP for

    "authentication type" instead of nothing.  Which isn't needed, it turns

    out, as leaving that field blank seems to work fine for internet access

    and MMS pickup anyway.


    So what's the difference, really, and why would an APN from the SIM be in

    mild conflict with something sent to me over T-Mo's network?  What is the

    "configuration message" even for, really?  I kept it around for reference,

    but I've already got a very customized APN set up that's different from

    either of these.  [Proxy config actually works right, for which I am

    very grateful because it's part of living Google-free on Android.]

      All replies

      • hobbit

        Re: Let's talk about APNs again



        I thought device users would be all over this topic.  APNs seem to trip up

        customer connectivity pretty often...

        • tmo_chris

          Re: Let's talk about APNs again

          The OTA message comes with a bunch of stuff. Its main use is for updating the SIM card to let it know what its phone number is. As for the APN updates, do you recall what it wanted to change it to?

            • hobbit

              Re: Let's talk about APNs again

              As noted, not a lot of difference except that it was split into separate parts, and specified authentication

              type PAP instead of none.  One part was specifically for MMS, with "APN type" set to "mms", and the other

              was the typical pointer to fast.t-mobile.com for "default,mms".


              Between this confusion and the fact that my messaging app has some kind of failure-return bug where

              MMS download is concerned, it took a *long* time to straighten all this out on my particular phone.

              It's all working nicely at this point, I was just curious about the minor discrepancies and how "loose"

              certain parts of an APN config can  be and still work.