Thursday, March 15, 2018

APN-OI Replacement

                       APN-OI Replacement


Helps MME select the corresponding PGW based upon the APN-OI replacement value received from HSS in Update Location Answer.

PGW is selected using DNS NAPTR query using APN-FQDN.
FQDN consists of APN-NI + APN-OI

Scenario:
Traffic can be diverted to the specific PGW when there are multiple PGWs with same MCC-MNC in the home network or if the UE is roaming in visiting network and to home-route the traffic to its home PGW.

In the normal scenario, PGW-FQDN constructed by MME based upon the APN value(NI) received from UE and MCC/MNC(OI) based upon the IMSI.
FQDN= <APN-NI>.apn.epc.<APN-OI>.3gppnetwork.org

If it is required not to select the default PGW by MME, APN-OI replacement field is required and to be provided by HSS to force MME to select the specific PGW of its choice instead of default PGW.

Case:

1. When UE is roaming and traffic needs to divert to home PGW then home HSS needs to send Visiting-PLMN allowed flag as false and APN-OI replacement value as home MCC-MNC (mncxxx.mccxxx.gprs) along with OI tag if need to route to the specific PGW host.
  tag.mnc<MNC>.mcc<MCC>.gprs
  Pgw1.mncxxx.mccxxx.gprs

Then MME creates APN-FQDN using above information and sends DNS NAPTR query to get the home PGW IP to forward the Create Session Request.

Note: if APN-OI replacement value is set by HSS in UE’s subscription Profile, then this is applicable for all the APN’s UE is subscribed to.  

1 comment:

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