LTE NAS ESM Cause Values
LTE NAS ESM cause values tell you why a PDN setup branch, bearer operation, or session-management request was rejected, changed, or pushed into another path. In a trace, the easiest way to read them is to find the message carrying the cause and map the code to what it really means: APN or PDN mismatch, bearer-state conflict, QoS or TFT problem, or a wider protocol error.
This page lists the main LTE NAS ESM cause values from 3GPP TS 24.301 and groups them in a practical way: PDN setup issues, bearer-handling failures, QoS and packet-filter problems, and protocol errors. Use it as the main lookup page for ESM cause links from LTE NAS message pages.
Quick facts
| Technology | LTE / EPS |
|---|---|
| Protocol scope | EPS NAS ESM cause values used in PDN connectivity, bearer activation, bearer modification, disconnect, and session-management error handling |
| Main spec | 3GPP TS 24.301 |
| Main clause | Annex A and IE definition 9.9.4.4 |
| Main use | PDN connectivity reject, bearer activation reject, bearer modification reject, PDN disconnect reject, and deactivation handling |
Overview
ESM cause values belong to the EPS session-management side of LTE NAS. You will see them most often in PDN Connectivity, bearer activation, bearer modification, and PDN Disconnect Reject handling.
The easiest way to read them is to start with the code, check whether it came from the network or the UE, and then see what it changes next. Some causes explain why the APN or PDN type was refused, some explain why a bearer update failed, and some tell you the message itself was not valid in the current ESM state.
Quick lookup
| Code | ESM cause | Typical meaning | Direction |
|---|---|---|---|
| #8 | Operator determined barring | The requested session-management branch is barred by operator policy. | Network -> UE |
| #26 | Insufficient resources | The network cannot provide the requested PDN or bearer resources at the moment. | Network -> UE |
| #27 | Missing or unknown APN | The requested APN is missing, unknown, or not resolvable in the current network context. | Network -> UE |
| #28 | Unknown PDN type | The requested PDN type is not supported or not valid for the current PDN setup branch. | Network -> UE |
| #29 | User authentication failed | PDN-side user authentication did not succeed, so the session-management branch cannot continue. | Network -> UE |
| #30 | Request rejected by serving GW or PDN GW | The requested PDN branch was refused by gateway-side policy or state. | Network -> UE |
| #31 | Request rejected, unspecified | The network rejected the session-management request but did not provide a more specific ESM cause. | Network -> UE |
| #32 | Service option not supported | The requested service option is not supported in the current session-management context. | Network -> UE |
| #33 | Requested service option not subscribed | The subscriber is not authorized for the requested session-management option. | Network -> UE |
| #34 | Service option temporarily out of order | The requested service option exists, but it is temporarily unavailable. | Network -> UE |
| #35 | PTI already in use | The procedure transaction identity used by the UE collides with a live ESM transaction. | Network -> UE |
| #47 | Last PDN disconnection not allowed | The network will not allow the UE to disconnect the final PDN connection in the current context. | Network -> UE |
| #49 | PDN type IPv4 only allowed | The requested PDN type was broader than what the network allows, and only IPv4 is allowed. | Network -> UE |
| #50 | PDN type IPv6 only allowed | The requested PDN type was broader than what the network allows, and only IPv6 is allowed. | Network -> UE |
| #51 | Single address bearers only allowed | The network will not allow the requested multi-address bearer behavior. | Network -> UE |
| #52 | ESM information not received | The network needed the protected ESM information exchange, but the expected detail was not received. | Network -> UE |
| #53 | PDN connection does not exist | The referenced PDN connection is not present in the network context. | Network -> UE |
| #54 | Multiple PDN connections for a given APN not allowed | The requested new PDN connection is not allowed because one for that APN already exists. | Network -> UE |
| #36 | Regular deactivation | The bearer is being deactivated in a normal, non-error branch. | Network -> UE |
| #38 | Network failure | The network cannot keep the session-management branch active because of internal failure. | Network -> UE |
| #39 | Reactivation requested | The network wants the UE to reactivate or refresh the bearer context rather than continue with the current state. | Network -> UE |
| #43 | Invalid EPS bearer identity | The bearer identity used in the message is not valid in the current session-management state. | UE <-> Network |
| #46 | PTI mismatch | The procedure transaction identity does not match the live ESM transaction context. | UE <-> Network |
| #55 | Request rejected due to collision with network initiated request | The UE-originated request collided with a network-initiated session-management branch. | Network -> UE |
| #57 | Bearer handling not supported | The requested bearer operation is not supported in the current network context. | Network -> UE |
| #58 | PDN type Ethernet only allowed | The branch only allows Ethernet PDN type rather than the type the UE requested. | Network -> UE |
| #59 | PDN type Ethernet and IPv4 only allowed | The allowed PDN type combination is narrower than the UE requested. | Network -> UE |
| #60 | Unsupported QCI value | The requested QoS uses a QCI that the network will not support for the branch. | Network -> UE |
| #112 | APN restriction value incompatible with active EPS bearer context | The requested session-management change conflicts with APN restriction already active in the UE context. | Network -> UE |
| #37 | EPS QoS not accepted | The network does not accept the requested EPS QoS for the current session-management branch. | Network -> UE |
| #41 | Semantic error in the TFT operation | The requested TFT operation is meaningful in form but wrong in content or logic. | UE <-> Network |
| #42 | Syntactical error in the TFT operation | The TFT structure is malformed or encoded incorrectly. | UE <-> Network |
| #44 | Semantic errors in packet filter(s) | The packet filters are understandable but wrong for the requested bearer behavior. | UE <-> Network |
| #45 | Syntactical errors in packet filter(s) | The packet filters are malformed or encoded incorrectly. | UE <-> Network |
| #81 | Invalid PTI value | The PTI value itself is not valid for the message. | UE <-> Network |
| #95 | Semantically incorrect message | The received ESM message is semantically incorrect. | UE <-> Network |
| #96 | Invalid mandatory information | Mandatory information is missing or invalid in the ESM message. | UE <-> Network |
| #97 | Message type non-existent or not implemented | The ESM message type does not exist or is not implemented. | UE <-> Network |
| #98 | Message type not compatible with protocol state | The message type is not valid in the current ESM protocol state. | UE <-> Network |
| #99 | Information element non-existent or not implemented | An ESM IE is unknown or not implemented. | UE <-> Network |
| #100 | Conditional IE error | A conditionally included ESM IE is wrong or inconsistent. | UE <-> Network |
| #101 | Message not compatible with protocol state | The ESM message itself is not valid in the current protocol state. | UE <-> Network |
| #111 | Protocol error, unspecified | A protocol error occurred but no more specific ESM cause value applies. | UE <-> Network |
PDN setup and subscription
These causes are most useful when the PDN setup branch fails because of APN, PDN type, authentication, or subscription-related issues.
Operator determined barring
The requested session-management branch is barred by operator policy.
Direction: Network -> UE
Typical message pages: Pdn Connectivity Request
Insufficient resources
The network cannot provide the requested PDN or bearer resources at the moment.
Direction: Network -> UE
Typical message pages: Pdn Connectivity Request , Activate Default Eps Bearer Context Request
Missing or unknown APN
The requested APN is missing, unknown, or not resolvable in the current network context.
Direction: Network -> UE
Typical message pages: Pdn Connectivity Request , Esm Information Response
Unknown PDN type
The requested PDN type is not supported or not valid for the current PDN setup branch.
Direction: Network -> UE
Typical message pages: Pdn Connectivity Request
User authentication failed
PDN-side user authentication did not succeed, so the session-management branch cannot continue.
Direction: Network -> UE
Typical message pages: Pdn Connectivity Request , Esm Information Response
Request rejected by serving GW or PDN GW
The requested PDN branch was refused by gateway-side policy or state.
Direction: Network -> UE
Typical message pages: Pdn Connectivity Request
Request rejected, unspecified
The network rejected the session-management request but did not provide a more specific ESM cause.
Direction: Network -> UE
Typical message pages: Pdn Disconnect Reject , Pdn Connectivity Request
Service option not supported
The requested service option is not supported in the current session-management context.
Direction: Network -> UE
Typical message pages: Pdn Connectivity Request , Bearer Resource Allocation Request
Requested service option not subscribed
The subscriber is not authorized for the requested session-management option.
Direction: Network -> UE
Typical message pages: Pdn Connectivity Request , Bearer Resource Allocation Request
Service option temporarily out of order
The requested service option exists, but it is temporarily unavailable.
Direction: Network -> UE
Typical message pages: Pdn Connectivity Request
PTI already in use
The procedure transaction identity used by the UE collides with a live ESM transaction.
Direction: Network -> UE
Typical message pages: Pdn Connectivity Request , Pdn Disconnect Request
Last PDN disconnection not allowed
The network will not allow the UE to disconnect the final PDN connection in the current context.
Direction: Network -> UE
Typical message pages: Pdn Disconnect Reject
PDN type IPv4 only allowed
The requested PDN type was broader than what the network allows, and only IPv4 is allowed.
Direction: Network -> UE
Typical message pages: Pdn Connectivity Request
PDN type IPv6 only allowed
The requested PDN type was broader than what the network allows, and only IPv6 is allowed.
Direction: Network -> UE
Typical message pages: Pdn Connectivity Request
Single address bearers only allowed
The network will not allow the requested multi-address bearer behavior.
Direction: Network -> UE
Typical message pages: Pdn Connectivity Request
ESM information not received
The network needed the protected ESM information exchange, but the expected detail was not received.
Direction: Network -> UE
Typical message pages: Esm Information Request , Esm Information Response
PDN connection does not exist
The referenced PDN connection is not present in the network context.
Direction: Network -> UE
Typical message pages: Pdn Disconnect Reject , Bearer Resource Modification Request
Multiple PDN connections for a given APN not allowed
The requested new PDN connection is not allowed because one for that APN already exists.
Direction: Network -> UE
Typical message pages: Pdn Connectivity Request
Bearer handling
These causes appear when live bearer activation, modification, or release handling collides with state, policy, or network limitations.
Regular deactivation
The bearer is being deactivated in a normal, non-error branch.
Direction: Network -> UE
Typical message pages: Deactivate Eps Bearer Context Request
Network failure
The network cannot keep the session-management branch active because of internal failure.
Direction: Network -> UE
Typical message pages: Deactivate Eps Bearer Context Request , Pdn Disconnect Reject
Reactivation requested
The network wants the UE to reactivate or refresh the bearer context rather than continue with the current state.
Direction: Network -> UE
Typical message pages: Deactivate Eps Bearer Context Request
Invalid EPS bearer identity
The bearer identity used in the message is not valid in the current session-management state.
Direction: UE <-> Network
Typical message pages: Pdn Disconnect Request , Modify Eps Bearer Context Request
PTI mismatch
The procedure transaction identity does not match the live ESM transaction context.
Direction: UE <-> Network
Typical message pages: Pdn Disconnect Request , Modify Eps Bearer Context Request
Request rejected due to collision with network initiated request
The UE-originated request collided with a network-initiated session-management branch.
Direction: Network -> UE
Typical message pages: Bearer Resource Modification Request , Pdn Disconnect Reject
Bearer handling not supported
The requested bearer operation is not supported in the current network context.
Direction: Network -> UE
Typical message pages: Bearer Resource Allocation Request , Bearer Resource Modification Request
PDN type Ethernet only allowed
The branch only allows Ethernet PDN type rather than the type the UE requested.
Direction: Network -> UE
Typical message pages: Pdn Connectivity Request
PDN type Ethernet and IPv4 only allowed
The allowed PDN type combination is narrower than the UE requested.
Direction: Network -> UE
Typical message pages: Pdn Connectivity Request
Unsupported QCI value
The requested QoS uses a QCI that the network will not support for the branch.
Direction: Network -> UE
Typical message pages: Bearer Resource Allocation Request , Modify Eps Bearer Context Request
APN restriction value incompatible with active EPS bearer context
The requested session-management change conflicts with APN restriction already active in the UE context.
Direction: Network -> UE
Typical message pages: Pdn Connectivity Request , Activate Default Eps Bearer Context Request
QoS and packet filters
These causes explain why requested QoS or traffic-filter handling was rejected or could not be interpreted cleanly.
EPS QoS not accepted
The network does not accept the requested EPS QoS for the current session-management branch.
Direction: Network -> UE
Typical message pages: Bearer Resource Allocation Request , Bearer Resource Modification Request
Semantic error in the TFT operation
The requested TFT operation is meaningful in form but wrong in content or logic.
Direction: UE <-> Network
Typical message pages: Modify Eps Bearer Context Request
Syntactical error in the TFT operation
The TFT structure is malformed or encoded incorrectly.
Direction: UE <-> Network
Typical message pages: Modify Eps Bearer Context Request
Semantic errors in packet filter(s)
The packet filters are understandable but wrong for the requested bearer behavior.
Direction: UE <-> Network
Typical message pages: Modify Eps Bearer Context Request
Syntactical errors in packet filter(s)
The packet filters are malformed or encoded incorrectly.
Direction: UE <-> Network
Typical message pages: Modify Eps Bearer Context Request
Protocol errors
These causes are the session-management equivalents of malformed message or invalid state handling.
Invalid PTI value
The PTI value itself is not valid for the message.
Direction: UE <-> Network
Typical message pages: Pdn Connectivity Request , Pdn Disconnect Request
Semantically incorrect message
The received ESM message is semantically incorrect.
Direction: UE <-> Network
Invalid mandatory information
Mandatory information is missing or invalid in the ESM message.
Direction: UE <-> Network
Message type non-existent or not implemented
The ESM message type does not exist or is not implemented.
Direction: UE <-> Network
Message type not compatible with protocol state
The message type is not valid in the current ESM protocol state.
Direction: UE <-> Network
Information element non-existent or not implemented
An ESM IE is unknown or not implemented.
Direction: UE <-> Network
Conditional IE error
A conditionally included ESM IE is wrong or inconsistent.
Direction: UE <-> Network
Message not compatible with protocol state
The ESM message itself is not valid in the current protocol state.
Direction: UE <-> Network
Protocol error, unspecified
A protocol error occurred but no more specific ESM cause value applies.
Direction: UE <-> Network
Where to use this page
This page is most useful when a message page says ESM cause but the real question is what the code means for PDN setup or bearer behavior. Use it together with the carrying message, the timer page, and the next ESM branch.
- Use PDN Connectivity Request with this page when APN, PDN type, or subscription handling stops the session branch.
- Use Activate Default EPS Bearer Context Request or Modify EPS Bearer Context Request with this page when bearer activation or live bearer updates fail or behave differently than expected.
- Use PDN Disconnect Reject with this page when the UE asked to release one PDN but the PDN stayed active.
- Use LTE NAS Timers when the same branch is also under T3482, T3485, T3489, or T3492 supervision.
References
- 3GPP TS 24.301, Release 18, Annex A: Cause values for EPS session management
- 3GPP TS 24.301, clause 9.9.4.4: ESM cause IE
- 3GPP TS 24.008, Annex H: referenced protocol error cause definitions used by the higher numbered ESM causes