LTE : What is the difference between UE-AMBR and APN-AMBR ?

Question

Consider UE has connected with multiple PDN connection each contains an different APN information, when we modify APN-AMBR value for both APNs at the same time in HSS and initiated HSS Initiated Subscribed QOS modification procedure, HSS sends Insert Subscriber data to MME with modified APN-AMBR information of both APN to MME, But MME forwards only first modified APN-AMBR information to S-GW in Modify Bearer Command message.
Please can anyone explain why MME does not forward second APN-AMBR information to S-GW ???. Whether the scenario is right either we can modify multiple APN-AMBR informations of single UE at the same time

Answer 1

Both the terms UE-AMBR and APN-AMBR are self-explanatory . Once the UE gets authenticated by MME, it triggers Update Location Procedure to inform the HSS about the current serving MME for the UE. As part of this procedure execution, HSS responds back to the MME by using the Update Location Answer message.

Update Location Answer message carries information about AMBR. AMBR AVP presents at the top level tells about UE-AMBR while AMBR AVP which presents within the APN-Configuration-Profile AVP informs about the AMBR associated with the APN.

UE may have connection with multiple APNs and UE-ABMR is the aggregated DL and UL data rates across all non-GBR bearers associated with same or different APNs.