LTE: Activate Dedicated EPS Bearer Context Reject

·        The UE may reject the ACTIVATE DEDICATED EPS BEARER CONTEXT REQUEST from the MME by sending an ACTIVATE DEDICATED EPS BEARER CONTEXT REJECT message.

·        The ACTIVATE DEDICATED EPS BEARER CONTEXT REJECT message shall include the EPS Bearer Identity and an ESM Cause value indicating the reason for rejecting the dedicated EPS bearer context activation request.

·        The ACTIVATE DEDICATED EPS BEARER CONTEXT REJECT message contains an ESM cause that typically indicates one of the following values:

#26: insufficient resources

#31: request rejected, unspecified

#41: semantic error in the TFT operation

#42: syntactical error in the TFT operation

#43: invalid EPS bearer identity

#44: semantic error(s) in packet filter(s)

#45: syntactical error(s) in packet filter(s) or

#95 – 111: protocol errors

·        After receiving the ACTIVATE DEDICATED EPS BEARER CONTEXT REJECT message, the MME shall stop the timer T3485 and abort the dedicated EPS bearer context activation procedure

Reference 3GPP TS 24.301

Example: ACTIVATE DEDICATED EPS BEARER CONTEXT REJECT message

LTE: ESM Information Request Procedure

·        The ESM information request procedure is used by the network to retrieve ESM information, i.e. protocol configuration options, APN, or both from the UE during the attach procedure if the UE has indicated (in the PDN CONNECTIVITY REQUEST) that it has ESM information that needs to be sent security protected.

·        The purpose of this procedure is to provide privacy for the ESM information if ciphering is enabled in the network.

·        The network initiates the ESM information request procedure by sending a ESM INFORMATION REQUEST message to the UE and starts the timer T3489.

·        This message shall be sent only after the security context has been setup, and if the ESM information transfer flag has been set in the PDN CONNECTIVITY REQUEST message.

·        The MME shall set the EPS bearer identity of the ESM INFORMATION REQUEST message to the value "no EPS bearer identity assigned" and include the PTI from the associated PDN CONNECTIVITY REQUEST message.

·        After receiving the ESM INFORMATION REQUEST message, the UE shall send an ESM INFORMATION RESPONSE message to the network.

·        The UE shall include all the protocol configuration options that need to be transferred security protected, and APN if required, to the network in the ESM INFORMATION RESPONSE (see the example below)message.

·        The UE shall set the EPS bearer identity of the ESM INFORMATION RESPONSE message to the value "no EPS bearer identity assigned" and include the PTI from the ESM INFORMATION REQUEST message

Reference 3GPP TS 24.301

Example:   ESM INFORMATION REQUEST message

Example:   ESM INFORMATION RESPONSE message  

LTE: Modify EPS Bearer Context Reject

·        If the MODIFY EPS BEARER CONTEXT REQUEST message cannot be accepted by the UE, then it sends a MODIFY EPS BEARER CONTEXT REJECT message to the MME.

·        This message shall include the EPS bearer identity and an ESM cause value indicating the reason for rejecting the EPS bearer context modification request

·        The MODIFY EPS BEARER CONTEXT REJECT message contains an ESM cause that typically indicates one of the following ESM cause values:

#26: insufficient resources

#41: semantic error in the TFT operation

#42: syntactical error in the TFT operation

#43: invalid EPS bearer identity

#44: semantic error(s) in packet filter(s)

#45: syntactical error(s) in packet filter(s)

#95 – 111: protocol errors

·        Upon receipt of the MODIFY EPS BEARER CONTEXT REJECT message with ESM cause value other than #43 "invalid EPS bearer identity", the MME shall stop the timer T3486 and abort the EPS bearer context modification procedure.

·        If the network receives the MODIFY EPS BEARER CONTEXT REJECT message with ESM cause #43 "invalid EPS bearer identity" the MME locally deactivates the EPS bearer context(s) without peer-to-peer ESM signalling

Reference 3GPP TS 24.301

Example:  MODIFY EPS BEARER CONTEXT REJECT message

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

LTE: Bearer Resource Modification Reject

·        If the network cannot accept the bearer resource modification requested by the UE, then the MME shall send a BEARER RESOURCE MODIFICATION REJECT message to the UE.

·        The BEARER RESOURCE MODIFICATION REJECT message shall contain the Procedure Transaction Identity (PTI) which should match the PTI value received in the BEARER RESOURCE MODIFICATION REQUEST.

·        Also, this message shall contain an ESM cause value which indicates the reason for rejecting the UE requested bearer resource modification.

·        If the bearer resource modification requested is for an established LIPA PDN connection, then the network shall reply with a BEARER RESOURCE MODIFICATION REJECT message with ESM cause #60 "bearer handling not supported".

·        If the ESM cause value is #26 "insufficient resources", the network may include a value for timer T3396 value IE in this message. In such a case, the UE should take different actions depending on the timer value as specified in section 6.5.4.4 in 3GPP TS 24.301.

·        After receiving the BEARER RESOURCE MODIFICATION REJECT message, the UE shall stop the timer T3481 and release the traffic flow aggregate description associated to the PTI value.

·        If the ESM cause included in the reject message is #43 "invalid EPS bearer identity", the UE locally deactivates the EPS bearer context(s) without peer-to-peer ESM signalling.

Reference 3GPP TS 24.301

Example:  BEARER RESOURCE MODIFICATION REJECT message

LTE: Bearer Resource Modification Request

·        The purpose of the UE requested bearer resource modification procedure is for a UE to request a modification or release of bearer resources for a traffic flow aggregate or modification of a traffic flow aggregate by replacing or adding packet filters.

·        When requesting a modification of bearer resources for a traffic flow aggregate or a modification of a traffic flow aggregate, the UE can modify the existing GBR.

·        If the network accepts this procedure, it invokes a dedicated EPS bearer context activation, an EPS bearer context modification, or an EPS bearer context deactivation procedure.

·        If there is a PDN connection for emergency bearer services established, the UE shall not request a modification of bearer resources for this PDN connection.

·        In order to request the modification of bearer resources for one traffic flow aggregate, the UE shall send a BEARER RESOURCE MODIFICATION REQUEST message to the MME

·        The UE shall include the EPS bearer identity of the EPS bearer associated with the traffic flow aggregate in the EPS bearer identity for packet filter IE.

·        To request a change of the GBR without changing the packet filter(s), the UE shall set the TFT operation code in the Traffic flow aggregate IE to "no TFT operation" and include the packet filter identifier(s) to which the change of the GBR applies in the Packet filter identifier parameter in the parameters list.

·        The UE shall indicate the new GBR requested for the EPS bearer context in the Required traffic flow QoS IE.

·        To request a modification of a traffic flow aggregate, the UE shall set the TFT operation code in the Traffic flow aggregate IE to "Replace packet filters in existing TFT" or "Add packet filters to existing TFT".

·        If the TFT operation code is set to "Add packet filters to existing TFT", the UE shall include the existing packet filter identifier(s) to which the newly added packet filter(s) is linked in the parameters list.

·        To request a release of bearer resources, the UE shall set the TFT operation code in the Traffic flow aggregate IE to "Delete packet filters from existing TFT".

·     If the UE includes the Required Traffic Flow QoS IE, the UE shall set the QCI to the current QCI value of the EPS bearer context.

·        If the bearer resource modification requested is accepted by the network, the MME shall send ACTIVATE DEDICATED EPS BEARER CONTEXT REQUEST, MODIFY EPS BEARER CONTEXT REQUEST or DEACTIVATE EPS BEARER CONTEXT REQUEST message with a PTI which matches the value used for the BEARER RESOURCE MODIFICATION REQUEST message.

·        If the bearer resource modification requested cannot be accepted by the network, the MME shall send a BEARER RESOURCE MODIFICATION REJECT message to the UE.

Reference 3GPP TS 24.301

Example:  BEARER RESOURCE MODIFICATION REQUEST message

LTE: Bearer Resource Allocation Reject

·        If the bearer resource allocation request cannot be accepted by the network, then the MME sends a BEARER RESOURCE ALLOCATION REJECT message to the UE.

·        The BEARER RESOURCE ALLOCATION REJECT message shall contain the Procedure Transaction Identity (PTI) which is equal to the PTI value in the BEARER RESOURCE ALLOCATION REQUEST received from the UE

·        This message shall also contain an ESM Cause value indicating the reason for rejecting the UE requested bearer resource allocation.

·        The UE, after receiving the BEARER RESOURCE ALLOCATION REJECT message, shall stop the timer T3480 and release the traffic flow aggregate description associated to the received PTI value

·        If the ESM cause value is #26 "insufficient resources", the network may include a value for timer T3396 value IE in the BEARER RESOURCE ALLOCATION REJECT message. Depending on the timer value, the UE shall take different actions as explained in 6.5.3.4 in 3GPP TS 24.301

Reference 3GPP TS 24.301

Example:  BEARER RESOURCE ALLOCATION REJECT message

LTE: Bearer Resource Allocation Request

·       The purpose of the UE requested bearer resource allocation procedure is (for an UE) to request an allocation of bearer resources for a traffic flow aggregate.

·        The UE requests a specific QoS demand (QCI) and optionally sends a Guaranteed Bit Rate (GBR) requirement for a new traffic flow aggregate.

·        If accepted by the network, this procedure invokes a dedicated EPS bearer context activation procedure or an EPS bearer context modification procedure.

·        If there is a PDN connection for emergency bearer services established, the UE shall not request additional bearer resources for this PDN connection.

·        The UE initiates this procedure by sending a BEARER RESOURCE ALLOCATION REQUEST message to the MME and starts the timer T3480.

·        The UE shall include the IE Linked EPS bearer identity and set it as the EPS bearer identity of the default EPS bearer associated with the requested bearer resource.

·        The UE shall set the TFT operation code in the Traffic flow aggregate IE to "Create new TFT".

·        In the Required traffic flow QoS IE, the UE shall indicate a QCI (QoS Class Identifier) and, if the UE also includes a GBR, the additional GBR required for the traffic flow aggregate.

·        If the bearer resource allocation request is accepted by the network, the MME shall send either an ACTIVATE DEDICATED EPS BEARER CONTEXT REQUEST or MODIFY EPS BEARER CONTEXT REQUEST message with a PTI value received in the BEARER RESOURCE ALLOCATION REQUEST message.

·        If the UE doesn’t receive response to the BEARER RESOURCE ALLOCATION REQUEST message before the expiry of the timer T3480, the UE shall resend this message and reset/restart T3480. This retransmission is repeated four times, i.e. on the fifth expiry of T3480, the UE shall abort the procedure, release the PTI allocated for this activation.

·        The Protocol Configuration Options IE is included in the BEARER RESOURCE ALLOCATION REQUEST message if the UE wishes to transmit (protocol) data (e.g. configuration parameters, error codes or messages/events) to the network.

·        The UE shall include the IE Device Properties in this message if the UE is configured for NAS signalling low priority

Reference 3GPP TS 24.301

Example:  BEARER RESOURCE ALLOCATION REQUEST message

LTE: Deactivate EPS Bearer Context Accept

·       The UE after receiving the DEACTIVATE EPS BEARER CONTEXT REQUEST message, shall delete the EPS bearer context identified by the EPS bearer identity.

·       If the EPS bearer identity indicated in the DEACTIVATE EPS BEARER CONTEXT REQUEST is that of the default bearer to a PDN, the UE shall delete all EPS bearer contexts associated to the PDN.

·       After deactivating the identified EPS bearer context (s), the UE shall respond to the MME with the DEACTIVATE EPS BEARER CONTEXT ACCEPT message.

·        If due to the EPS bearer context deactivation, there is only one PDN connection active and that is for emergency bearer services, then the UE shall consider itself attached for emergency bearer services only

·        In the DEACTIVATE EPS BEARER CONTEXT ACCEPT message, the UE shall include Procedure Transaction Identity (PTI) as received in the DEACTIVATE EPS BEARER CONTEXT REQUEST message

·        Other IEs in the DEACTIVATE EPS BEARER CONTEXT ACCEPT message include, EPS bearer identity and Protocol configuration options

Reference 3GPP TS 24.301

Example:  DEACTIVATE EPS BEARER CONTEXT ACCEPT message

LTE: Deactivate EPS Bearer Context Request

·        The purpose of the EPS bearer context deactivation procedure is to deactivate an EPS bearer context or disconnect from a PDN by deactivating all EPS bearer contexts to that PDN.

·        This procedure is initiated by the network, and it may be triggered by the UE by means of the Bearer Resource Modification or PDN Disconnect procedure.

·        If a NAS signalling connection exists when the MME initiates this procedure, then the MME shall initiate the EPS bearer context deactivation procedure by sending a DEACTIVATE EPS BEARER CONTEXT REQUEST message to the UE and start the timer T3495.

·        If there no NAS signalling connection exists when the MME initiates this procedure, then the ESM entity in the MME shall locally deactivate the EPS bearer context towards the UE without any peer-to-peer ESM signalling between the MME and the UE.

·        The DEACTIVATE EPS BEARER CONTEXT REQUEST message contains an ESM cause typically indicating one of the following:

#8:  operator determined barring

#36: regular deactivation

#38: network failure

#39: reactivation requested or

#112: APN restriction value incompatible with active EPS bearer context

·        If the deactivation is triggered by a UE initiated bearer resource modification or PDN disconnect procedure, the DEACTIVATE EPS BEARER CONTEXT REQUEST message shall contain the PTI value received from the UE in the corresponding message.

·        When the MME wants to deactivate all EPS bearer contexts to a PDN and thus disconnect the UE from the PDN, the MME shall include the EPS Bearer Identity of the default bearer associated to the PDN in the DEACTIVATE EPS BEARER CONTEXT REQUEST message.

·        If the MME doesn’t receive a response for DEACTIVATE EPS BEARER CONTEXT REQUEST before the expiry of the timer T3495, the MME shall resend this message and shall reset and restart T3495. This retransmission is repeated four times, i.e. on the fifth expiry of T3495, the MME shall abort the procedure and deactivate the EPS bearer context locally without any peer-to-peer ESM signalling between the MME and the UE.

·        The IE Protocol Configuration Options is included in the message if the network wishes to transmit (protocol) data (e.g. configuration parameters, error codes or messages/events) to the UE.

Reference 3GPP TS 24.301

Example:  DEACTIVATE EPS BEARER CONTEXT REQUEST message

LTE: PDN Disconnect Request

·        The purpose of the PDN Disconnect procedure is for a UE to request the network to disconnect from one PDN.

·        The UE can initiate this procedure to disconnect from any PDN as long as it is connected to at least one other PDN.

·        Successful completion of this procedure means that, all EPS bearer contexts established towards this PDN, including the default EPS bearer context, are released.

·        In order to disconnect from the last PDN (the one and the only PDN to which the UE has the connection), the UE should not use PDN disconnect procedure. Instead, it shall use detach procedure

·        In order to request PDN disconnection from a PDN, the UE shall send a PDN DISCONNECT REQUEST message to the MME and start the timer T3492.

·        In this message, The UE shall set the value of Linked EPS Bearer Identity IE as the EPS Bearer Identity of default bearer associated with the PDN for which UE is sending the disconnect request.

·        If the network accepts the PDN DISCONNECT REQUEST sent by the UE, then it shall send the DEACTIVATE EPS BEARER CONTEXT REQUEST message including the linked EPS bearer identity of the default bearer associated with the PDN to disconnect from.

·        If the network doesn’t accept the PDN DISCONNECT REQUEST sent by the UE, the MME shall send a PDN DISCONNECT REJECT message to the UE which shall contain the PTI and an ESM cause IE indicating the cause for the rejection

·        Upon receipt of the DEACTIVATE EPS BEARER CONTEXT REQUEST or PDN DISCONNECT REJECT message, the UE shall stop the timer T3492

·        If there is no response received for the PDN DISCONNECT REQUEST before the expiry of the timer T3492, the UE shall resend the PDN DISCONNECT REQUEST and shall reset and restart timer T3492. This retransmission is repeated four times, i.e. on the fifth expiry of timer T3492, the UE shall abort the procedure and deactivate all EPS bearer contexts for this PDN connection locally without peer-to-peer signalling between the UE and the MME

Reference 3GPP TS 24.301

Example:  PDN DISCONNECT REQUEST message

LTE: PDN Connectivity Reject

·        If the PDN CONNECTIVITY REQUEST cannot be accepted by the network, then the MME shall send a PDN CONNECTIVITY REJECT message to the UE.

·        The PDN CONNECTIVITY REJECT message shall contain the Procedure Transaction Identity (PTI) which should match the PTI value in the PDN CONNECTIVITY REQUEST sent by UE

·        Also, this message shall contain an ESM cause value which indicates the reason for rejecting the UE requested PDN connectivity.

·        The ESM cause IE typically indicates one of the following ESM cause values:

  #8:  operator determined barring

#26:  insufficient resources

#27:  missing or unknown APN

#28:  unknown PDN type

#29:  user authentication failed

#30:  request rejected by Serving GW or PDN GW

#31:  request rejected, unspecified

#32:  service option not supported

#33:  requested service option not subscribed

#34:  service option temporarily out of order

#35:  PTI already in use

#38:  network failure

#50:  PDN type IPv4 only allowed

#51:  PDN type IPv6 only allowed

#53:  ESM information not received

#54:  PDN connection does not exist

#55:  multiple PDN connections for a given APN not allowed

#95 – 111:  protocol errors

#112:  APN restriction value incompatible with active EPS bearer context.

·        If the ESM cause value is #26 "insufficient resources" or #27 "missing or unknown APN", the network may include a value for timer T3396 in the PDN CONNECTIVITY REJECT message. In such a case, the UE should take different actions depending on the timer value and reject cause. Refer to section 6.5.1.4 in the 3GPP TS 24.301 for detailed information

 Reference 3GPP TS 24.301

Example:  PDN CONNECTIVITY REJECT message

LTE: PDN Connectivity Request

·       The PDN connectivity procedure is used by the UE to request the setup of a default EPS bearer to a PDN.

·        The UE requests connectivity to a PDN by sending a PDN CONNECTIVITY REQUEST message to the network. If this request is accepted by the network, then it initiates the establishment of a default EPS bearer context activation procedure.

·        This procedure is used either to establish the first default bearer (PDN CONNECTIVITY REQUEST is sent along with initial attach message), or to establish subsequent default bearers to additional PDNs (a stand-alone PDN CONNECTIVITY REQUEST is sent by the UE).

·        If the UE is in EMM-IDLE mode, the Service Request procedure is performed before the PDN Connectivity procedure can be initiated.

·       If there is already a PDN connection for emergency bearer services established, the UE shall not request an additional PDN connection for emergency bearer services. 

·       A UE attached for emergency bearer services shall not request a PDN connection to any other PDN.

·       When the PDN CONNECTIVITY REQUEST message is sent together with an ATTACH REQUEST message, the UE shall not include the APN.

·        When requesting connectivity to an additional PDN, the UE shall include the requested APN (in the stand-alone PDN CONNECTIVITY REQUEST) except for  emergency bearer services

·       The UE may set the ESM information transfer flag in the PDN CONNECTIVITY REQUEST message to indicate that it has ESM information, i.e. protocol configuration options, or APN, or both, that needs to be transferred to the MME after the NAS signalling security has been activated

·        If the  ESM information transfer flag is set in PDN CONNECTIVITY REQUEST message, the MME initiates (after NAS sigalling security is activated) the ESM information request procedure in which the UE can provide the MME with protocol configuration options or APN or both.

·       If the UE wishes to connect to a PDN using default APN, it need not include the APN in the Access Point Name IE in the ESM INFORMATION RESPONSE or PDN CONNECTIVITY REQUEST (stand-alone) message. The only exceptional case is, if the connectivity to a PDN using the default APN requires PAP/CHAP, then the UE should include the APN in the Access point name IE 

·        The UE shall set the Request Type IE to "initial request" when the UE is establishing a new PDN connectivity to a PDN in an attach procedure or in a stand-alone PDN connectivity procedure.

·        The UE shall set the Request Type IE to "emergency" when the UE is requesting a new PDN connectivity for emergency bearer services.

·        The Request Type IE is set to "handover" when the connectivity to a PDN is established upon handover from a non-3GPP access network and the UE was connected to that PDN before the handover to the 3GPP access network

·        The other IEs in the PDN CONNECTIVITY REQUEST message include EPS Bearer Identity, Procedure Transaction Identity, PDN Type, and Device Properties etc…

·       If the UE includes ESM information transfer flag in the PDN CONNECTIVITY REQUEST message, the MME waits for completion of the ESM information request procedure before proceeding with the PDN connectivity procedure. The MME then checks if connectivity with the requested PDN can be established.

·       If requested APN is not included in the PDN CONNECTIVITY REQUEST or the ESM INFORMATION RESPONSE message and the request type is different from "emergency", the MME shall use the default APN as the requested APN. If the request type is "emergency", the MME shall use the APN configured for emergency bearer services

Reference 3GPP TS 24.301

Example1: PDN CONNECTIVITY REQUEST message (sent along with Attach Request)

Example2: Stand-Alone PDN CONNECTIVITY REQUEST message