LTE: Modify EPS Bearer Context Request

·        The purpose of the EPS bearer context modification procedure is to modify an EPS bearer context with a specific QoS and TFT.

·        This procedure is initiated by the network, but it may also be initiated as part of the UE requested bearer resource allocation/modification procedure.

·        The network may also initiate the EPS bearer context modification procedure to update the APN-AMBR of the UE, for instance after an inter-system handover

·        The MME initiates the EPS bearer context modification procedure by sending a MODIFY EPS BEARER CONTEXT REQUEST message to the UE and starts the timer T3486

·        The MME shall include an EPS bearer identity that identifies the EPS bearer context to be modified in the MODIFY EPS BEARER CONTEXT REQUEST message

·        If this procedure was initiated by a UE requested bearer resource allocation/modification procedure, then the MODIFY EPS BEARER CONTEXT REQUEST shall contain the PTI value received by the MME in the corresponding request message.

·        The IEs in this message include, EPS bearer identity, PTI, New EPS QoS, TFT, New QoS, Negotiated LLC SAPI, Radio priority, Packet flow ID, APN-AMBR, and Protocol configuration options etc…

·        After receiving the MODIFY EPS BEARER CONTEXT REQUEST message, the UE shall stop timer T3396 if it is running for the APN associated with the PDN connection, check the received TFT before taking it into use and then send a MODIFY EPS BEARER CONTEXT ACCEPT message to the MME

Reference 3GPP TS 24.301

Example:  Modify EPS Bearer Context Request message