LTE: What would be the possible causes for attach reject ?

Question

If yes, then what are all possible scenarios in the network which causes to do so ?

Answer 1

1. If the MME is not configured to support Emergency Attach the MME shall reject any Attach Request that indicates Attach Type "Emergency".

2. The MME may send the ME Identity Check Request (ME Identity, IMSI) to the EIR. The EIR shall respond with ME Identity Check Ack (Result). Dependent upon the Result, the MME decides whether to continue with this Attach procedure or to reject the UE.

3. If due to regional subscription restrictions or access restrictions (e.g. CSG restrictions) the UE is not allowed to attach in the TA or due to subscription checking fails for other reasons, the new MME rejects the Attach Request with an appropriate cause.

4. If all checks are successful then the new MME constructs a context for the UE. If the APN provided by the UE is not allowed by subscription, or the Update Location is rejected by the HSS, the new MME rejects the Attach Request from the UE with an appropriate cause.

5. The Maximum APN Restriction denotes the most stringent restriction as required by any already active bearer context. If there are no already active bearer contexts, this value is set to the least restrictive type . If the PGW receives the Maximum APN Restriction, then the PGW shall check if the Maximum APN Restriction value does not conflict with the APN Restriction value associated with this bearer context request. If there is no conflict the request shall be allowed, otherwise the request shall be rejected with sending an appropriate error cause to the UE.