7 Handling of unknown, unforeseen, and erroneous protocol data

24.3013GPPNon-Access-Stratum (NAS) protocol for Evolved Packet System (EPS)Release 18Stage 3TS

Tools: ARFCN - Frequency Conversion for 5G NR/LTE/UMTS/GSM

7.1 General

The procedures specified in the present document apply to those messages which pass the checks described in this clause.

This clause also specifies procedures for the handling of unknown, unforeseen, and erroneous protocol data by the receiving entity. These procedures are called "error handling procedures", but in addition to providing recovery mechanisms for error situations they define a compatibility mechanism for future extensions of the protocols.

Clauses 7.1 to 7.8 shall be applied in order of precedence.

Most error handling procedures are mandatory for the UE.

Detailed error handling procedures in the network are implementation dependent and may vary from PLMN to PLMN. However, when extensions of this protocol are developed, networks will be assumed to have the error handling that is indicated in this clause as mandatory ("shall") and that is indicated as strongly recommended ("should").

Also, the error handling of the network is only considered as mandatory or strongly recommended when certain thresholds for errors are not reached during a dedicated connection.

For definition of semantical and syntactical errors see 3GPP TS 24.007 [12], clause 11.4.2.

7.2 Message too short

When a message is received that is too short to contain a complete message type information element, that message shall be ignored, cf. 3GPP TS 24.007 [12].

7.3 Unknown or unforeseen procedure transaction identity or EPS bearer identity

7.3.1 Procedure transaction identity

The following network procedures shall apply for handling an unknown, erroneous, or unforeseen PTI received in an ESM message:

a) If the network receives a PDN CONNECTIVITY REQUEST message with an unassigned or reserved PTI value, the network shall respond with a PDN CONNECTIVITY REJECT message including ESM cause #81 "invalid PTI value".

b) If the network receives a PDN DISCONNECT REQUEST message with an unassigned or reserved PTI value, the network shall respond with a PDN DISCONNECT REJECT message including ESM cause #81 "invalid PTI value".

c) If the network receives a BEARER RESOURCE ALLOCATION REQUEST message with an unassigned or reserved PTI value, the network shall respond with a BEARER RESOURCE ALLOCATION REJECT message including ESM cause #81 "invalid PTI value".

d) If the network receives a BEARER RESOURCE MODIFICATION REQUEST message with an unassigned or reserved PTI value, the network shall respond with a BEARER RESOURCE MODIFICATION REJECT message including ESM cause #81 "invalid PTI value".

e) If the network receives an ESM INFORMATION RESPONSE message which includes an unassigned or reserved PTI value, the network shall ignore the message. If the PTI is an assigned value that does not match the PTI in use for any ongoing transaction related procedure, the network shall respond with an ESM STATUS message including ESM cause #81 "invalid PTI value".

f) If the network receives an ESM message other than those listed in items a through e above with a reserved PTI value, the network shall ignore the message.

The following UE procedures shall apply for handling an unknown, erroneous, or unforeseen PTI received in an ESM message:

a) If the UE receives a PDN CONNECTIVITY REJECT message in which the PTI value is an unassigned or reserved value, or an assigned value that does not match any PTI in use, the UE shall ignore the message.

b) If the UE receives a PDN DISCONNECT REJECT message in which the PTI value is an unassigned or reserved value, or an assigned value that does not match any PTI in use, the UE shall ignore the message.

c) If the UE receives a BEARER RESOURCE ALLOCATION REJECT message in which the PTI value is an unassigned or reserved value, or an assigned value that does not match any PTI in use, the UE shall ignore the message.

d) If the UE receives a BEARER RESOURCE MODIFICATION REJECT message in which the PTI value is an unassigned or reserved value, or an assigned value that does not match any PTI in use, the UE shall ignore the message.

e) If the UE receives an ESM INFORMATION REQUEST message in which the PTI value is an unassigned or reserved value, the UE shall ignore the message. If the PTI is an assigned value that does not match a PTI in use for a pending UE requested PDN connectivity procedure for which the ESM information transfer flag was set in the PDN CONNECTIVITY REQUEST message, the UE shall respond with an ESM STATUS message including ESM cause #47 "PTI mismatch".

f) If the UE receives a NOTIFICATION message in which the PTI value is an unassigned value, the UE shall proceed as specified in clause 7.3.2. If the PTI is a reserved value, the UE shall respond with an ESM STATUS message including ESM cause #81 "invalid PTI value". If the PTI is an assigned value that does not match any PTI in use, the UE shall respond with an ESM STATUS message including ESM cause #47 "PTI mismatch".

g) If the UE receives an ACTIVATE DEFAULT EPS BEARER CONTEXT REQUEST message in which the PTI value is an assigned value that does not match any PTI in use, if the UE detects that this request is a network retransmission of an already accepted request (see clause 6.5.1.3) the UE shall respond with an ACTIVATE DEFAULT EPS BEARER CONTEXT ACCEPT message. Otherwise, the UE shall respond with an ACTIVATE DEFAULT EPS BEARER CONTEXT REJECT message including ESM cause #47 "PTI mismatch".

h) If the UE receives an ACTIVATE DEFAULT EPS BEARER CONTEXT REQUEST message which contains a reserved or unassigned PTI value, the UE shall respond with an ACTIVATE DEFAULT EPS BEARER CONTEXT REJECT message including ESM cause #81 "invalid PTI value".

i) If the UE receives an ACTIVATE DEDICATED EPS BEARER CONTEXT REQUEST message in which the PTI value is an assigned value that does not match any PTI in use, if the UE detects that this request is a network retransmission of an already accepted request (see clauses 6.5.3.3 and 6.5.4.3) the UE shall respond with an ACTIVATE DEDICATED EPS BEARER CONTEXT ACCEPT message. Otherwise, the UE shall respond with an ACTIVATE DEDICATED EPS BEARER CONTEXT REJECT message including ESM cause #47 "PTI mismatch".

j) If the UE receives an ACTIVATE DEDICATED EPS BEARER CONTEXT REQUEST message which contains a reserved PTI value, the UE shall respond with an ACTIVATE DEDICATED EPS BEARER CONTEXT REJECT message including ESM cause #81 "invalid PTI value".

k) If the UE receives a MODIFY EPS BEARER CONTEXT REQUEST message in which the PTI value is an assigned value that does not match any PTI in use, if the UE detects that this request is a network retransmission of an already accepted request (see clauses 6.5.3.3 and 6.5.4.3) the UE shall respond with a MODIFY EPS BEARER CONTEXT ACCEPT message. Otherwise, the UE shall respond with a MODIFY EPS BEARER CONTEXT REJECT message including ESM cause #47 "PTI mismatch".

l) If the UE receives a MODIFY EPS BEARER CONTEXT REQUEST message which contains a reserved PTI value, the UE shall respond with a MODIFY EPS BEARER CONTEXT REJECT message including ESM cause #81 "invalid PTI value".

m) If the UE receives a DEACTIVATE EPS BEARER CONTEXT REQUEST message in which the PTI value is a reserved value or an assigned value that does not match any PTI in use, the UE shall ignore the message.

n) If the UE receives an ESM message other than those listed in items a through m with a reserved PTI value or an assigned value that does not match any PTI in use, the UE shall ignore the message.

7.3.2 EPS bearer identity

The following network procedures shall apply for handling an unknown, erroneous, or unforeseen EPS bearer identity received in the header of an ESM message (specified as the header of a standard L3 message, see 3GPP TS 24.007 [12]):

a) If the network receives a PDN CONNECTIVITY REQUEST message which includes an assigned or reserved EPS bearer identity value, the network shall respond with a PDN CONNECTIVITY REJECT message including ESM cause #43 "invalid EPS bearer identity".

b) If the network receives a PDN DISCONNECT REQUEST message which includes an assigned or reserved EPS bearer identity value, the network shall respond with a PDN DISCONNECT REJECT message including ESM cause #43 "invalid EPS bearer identity".

c) If the network receives a BEARER RESOURCE ALLOCATION REQUEST message which includes an assigned or reserved EPS bearer identity value, the network shall respond with a BEARER RESOURCE ALLOCATION REJECT message including ESM cause #43 "invalid EPS bearer identity".

d) If the network receives a BEARER RESOURCE MODIFICATION REQUEST message which includes an assigned or reserved EPS bearer identity value, the network shall respond with a BEARER RESOURCE MODIFICATION REJECT message including ESM cause #43 "invalid EPS bearer identity".

e) If the network receives an ESM INFORMATION RESPONSE message which includes an assigned or reserved EPS bearer identity value, the network shall ignore the message.

f) If the network receives an ESM DATA TRANSPORT message which includes a reserved EPS bearer identity value or an assigned value that does not match an existing EPS bearer context, the network shall respond with an ESM STATUS message including ESM cause #43 "invalid EPS bearer identity".

g) If the network receives an ESM message other than those listed in items a through e above in which the message includes a reserved EPS bearer identity value or an assigned value that does not match an existing EPS bearer context, the network shall ignore the message.

The following UE procedures shall apply for handling an unknown, erroneous, or unforeseen EPS bearer identity received in the header of an ESM message:

a) If the UE receives a PDN CONNECTIVITY REJECT message which includes an assigned or reserved EPS bearer identity value, the UE shall ignore the message.

b) If the UE receives a PDN DISCONNECT REJECT message which includes an assigned or reserved EPS bearer identity value, the UE shall ignore the message.

c) If the UE receives a BEARER RESOURCE ALLOCATION REJECT message which includes an assigned or reserved EPS bearer identity value, the UE shall ignore the message.

d) If the UE receives a BEARER RESOURCE MODIFICATION REJECT message which includes an assigned or reserved EPS bearer identity value, the UE shall ignore the message.

e) If the UE receives an ESM INFORMATION REQUEST message which includes an assigned or reserved EPS bearer identity value, the UE shall respond with an ESM STATUS message including ESM cause #43 "invalid EPS bearer identity".

f) If the UE receives a NOTIFICATION message which includes a reserved EPS bearer identity value, an assigned EPS bearer identity value that does not match an existing EPS bearer context, or the combination of an unassigned PTI value and an unassigned EPS bearer identity value, the UE shall respond with an ESM STATUS message including ESM cause #43 "invalid EPS bearer identity".

g) If the UE receives an ACTIVATE DEFAULT EPS BEARER CONTEXT REQUEST message which includes an unassigned or reserved EPS bearer identity value, the UE shall respond with an ACTIVATE DEFAULT EPS BEARER CONTEXT REJECT message including ESM cause #43 "invalid EPS bearer identity".

h) If the UE receives an ACTIVATE DEDICATED EPS BEARER CONTEXT REQUEST message which includes an unassigned or reserved EPS bearer identity value, the UE shall respond with an ACTIVATE DEDICATED EPS BEARER CONTEXT REJECT message including ESM cause #43 "invalid EPS bearer identity".

i) If the UE receives a MODIFY EPS BEARER CONTEXT REQUEST message which includes an unassigned or reserved EPS bearer identity value or an assigned EPS bearer identity value that does not match an existing EPS bearer context, the UE shall respond with a MODIFY EPS BEARER CONTEXT REJECT message including ESM cause #43 "invalid EPS bearer identity".

j) If the UE receives a DEACTIVATE EPS BEARER CONTEXT REQUEST message which includes an unassigned or reserved EPS bearer identity value or an assigned EPS bearer identity value that does not match an existing EPS bearer context, the UE shall respond with a DEACTIVATE EPS BEARER CONTEXT ACCEPT message with the EPS bearer identity set to the received EPS bearer identity.

k) If the UE receives an ESM DATA TRANSPORT message which includes a reserved EPS bearer identity value or an assigned value that does not match an existing EPS bearer context, the UE shall respond with an ESM STATUS message including ESM cause #43 "invalid EPS bearer identity".

l) If the UE receives an ESM message other than those listed in items a through j in which the message includes an unassigned or reserved EPS bearer identity value or a value that does not match an EPS bearer context of an established PDN connection, the UE shall ignore the message.

7.4 Unknown or unforeseen message type

If UE receives an EMM message or ESM message with message type not defined for the protocol discriminator (PD) or not implemented by the receiver, it shall return a status message (EMM STATUS or ESM STATUS depending on the PD) with cause #97 "message type non-existent or not implemented".

If the network receives an EMM or ESM message with message type not defined for the PD or not implemented by the receiver in a protocol state where reception of an unsolicited message with the given PD from the UE is not foreseen in the protocol, the network actions are implementation dependent. Otherwise, if the network receives a message with message type not defined for the PD or not implemented by the receiver, it shall ignore the message except that it should return a status message (EMM STATUS or ESM STATUS depending on the PD) with cause #97 "message type non-existent or not implemented".

NOTE: A message type not defined for the PD in the given direction is regarded by the receiver as a message type not defined for the PD, see 3GPP TS 24.007 [12].

If the UE receives a message not compatible with the protocol state, the UE shall return a status message (EMM STATUS or ESM STATUS depending on the PD) with cause #98 "message type not compatible with protocol state".

If the network receives a message not compatible with the protocol state, the network actions are implementation dependent.

7.5 Non-semantical mandatory information element errors

7.5.1 Common procedures

When on receipt of a message,

– an "imperative message part" error; or

– a "missing mandatory IE" error

is diagnosed or when a message containing:

– a syntactically incorrect mandatory IE;

– an IE unknown in the message, but encoded as "comprehension required" (see 3GPP TS 24.007 [12]); or

– an out of sequence IE encoded as "comprehension required" (see 3GPP TS 24.007 [12]) is received,

the UE shall proceed as follows:

If the message is not one of the messages listed in clause 7.5.3, item a, b, c, or d, the UE shall return a status message (EMM STATUS or ESM STATUS depending on the PD) with cause #96 "invalid mandatory information"; and

the network shall proceed as follows:

If the message is not one of the messages listed in clause 7.5.3, item e, f, g or h, the network shall either:

– try to treat the message (the exact further actions are implementation dependent); or

– ignore the message except that it should return a status message (EMM STATUS or ESM STATUS depending on the PD) with cause #96 "invalid mandatory information".

7.5.2 EPS mobility management

No exceptional cases are described for mobility management messages.

No semantical or syntactical diagnosis other than presence and length shall be performed on the ESM message container information element in the ATTACH REQUEST, ATTACH ACCEPT, ATTACH COMPLETE and CONTROL PLANE SERVICE REQUEST messages.

7.5.3 EPS session management

The following UE procedures shall apply for handling an error encountered with a mandatory information element in an ESM message:

a) If the message is an ACTIVATE DEFAULT EPS BEARER CONTEXT REQUEST, an ACTIVATE DEFAULT EPS BEARER CONTEXT REJECT message with ESM cause #96 "invalid mandatory information", shall be returned.

b) If the message is an ACTIVATE DEDICATED EPS BEARER CONTEXT REQUEST, an ACTIVATE DEDICATED EPS BEARER CONTEXT REJECT message with ESM cause #96 "invalid mandatory information", shall be returned.

c) If the message is a MODIFY EPS BEARER CONTEXT REQUEST, a MODIFY EPS BEARER CONTEXT REJECT message with ESM cause #96 "invalid mandatory information", shall be returned.

d) If the message is a DEACTIVATE EPS BEARER CONTEXT REQUEST, a DEACTIVATE EPS BEARER CONTEXT ACCEPT message shall be returned. All resources associated with that EPS bearer shall be released.

The following network procedures shall apply for handling an error encountered with a mandatory information element in an ESM message:

e) If the message is a PDN CONNECTIVITY REQUEST, a PDN CONNECTIVITY REJECT message with ESM cause #96 "invalid mandatory information", shall be returned.

f) If the message is a PDN DISCONNECT REQUEST, a PDN DISCONNECT REJECT message with ESM cause #96 "invalid mandatory information", shall be returned.

g) If the message is a BEARER RESOURCE ALLOCATION REQUEST, a BEARER RESOURCE ALLOCATION REJECT message with ESM cause #96 "invalid mandatory information", shall be returned.

h) If the message is a BEARER RESOURCE MODIFICATION REQUEST, a BEARER RESOURCE MODIFICATION REJECT message with ESM cause #96 "invalid mandatory information", shall be returned.

7.6 Unknown and unforeseen IEs in the non-imperative message part

7.6.1 IEIs unknown in the message

The UE shall ignore all IEs unknown in a message which are not encoded as "comprehension required" (see 3GPP TS 24.007 [12]).

The network shall take the same approach.

7.6.2 Out of sequence IEs

The UE shall ignore all out of sequence IEs in a message which are not encoded as "comprehension required" (see 3GPP TS 24.007 [12]).

The network should take the same approach.

7.6.3 Repeated IEs

If an information element with format T, TV, TLV, or TLV-E is repeated in a message in which repetition of the information element is not specified in clause 8 of the present document, the UE shall handle only the contents of the information element appearing first and shall ignore all subsequent repetitions of the information element. When repetition of information elements is specified, the UE shall handle only the contents of specified repeated information elements. If the limit on repetition of information elements is exceeded, the UE shall handle the contents of information elements appearing first up to the limit of repetitions and shall ignore all subsequent repetitions of the information element.

The network should follow the same procedures.

7.7 Non-imperative message part errors

This category includes:

– syntactically incorrect optional IEs; and

– conditional IE errors.

7.7.1 Syntactically incorrect optional IEs

The UE shall treat all optional IEs that are syntactically incorrect in a message as not present in the message.

The network shall take the same approach.

7.7.2 Conditional IE errors

When upon receipt of a EMM or ESM message the UE diagnoses a "missing conditional IE" error or an "unexpected conditional IE" error, or when it receives a EMM or ESM message containing at least one syntactically incorrect conditional IE, the UE shall ignore the message and shall return a status message (EMM STATUS or ESM STATUS depending on the PD) with cause #100 "conditional IE error".

When the network receives a message and diagnoses a "missing conditional IE" error or an "unexpected conditional IE" error or when it receives a message containing at least one syntactically incorrect conditional IE, the network shall either:

– try to treat the message (the exact further actions are implementation dependent); or

– ignore the message except that it should return a status message (EMM STATUS or ESM STATUS depending on the PD) with cause #100 "conditional IE error".

7.8 Messages with semantically incorrect contents

When a message with semantically incorrect contents is received, the UE shall perform the foreseen reactions of the procedural part of the present document (i.e. of clauses 4, 5 and 6). If however no such reactions are specified, the UE shall ignore the message except that it shall return a status message (EMM STATUS or ESM STATUS depending on the PD) with cause #95 "semantically incorrect message".

The network should follow the same procedure except that a status message is not normally transmitted.