Cellular Network Infrastructure » osmo-ePDG - VoWifi Evolved Packet Data Gateway

As we've seen in #6114 it might be interesting to control the eDPG hostname so we can generate a certificate for it (signed by letsencrypt which presumably is trusted by default in unmodified android). It's not critical as EAP-only authentication appeared to be working in the test case there.

It would be good to find some time to test with a couple of different UE whether they actually respect the ePDG related files / configs that can be stored in the USIM/ISIM.

A quick look in TS 31.102 revaled:

• EF.ePDGId
  • contains a TLV-wrapped IPv4, IPv6 or hostname of the ePDG
• EF.ePDGSelection
  • control the Selection of the ePDG proceduer in the UE (3GPP TS 24.302)
  • contais a number of (plmn, epdg_priority, epdg_fqdn_indicator)
    • the epdg_fqdn_indicator state whether the Operator Identifier FQDN, or a location based FQDN format shall be used

• EF.ePDGIdEm
  • same as above, but for emergency calls
• EF.ePDGSelectionEm
  • same as above, but for emergency calls.

So EF.ePDGId is really the most interesting one.