How it Works
The NAS messages compliance with invalid protocol data handling feature works as follows:
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SMF ignores a NAS message that is too short to contain a complete message type information element (IE).
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SMF ignores a NAS message that is longer than the maximum limit as defined in the 3GPP specification.
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SMF ignores the IEs that are unknown in a NAS message.
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SMF ignores the IEs with incorrect sequence in a NAS message.
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If an information element with the T, TV, TLV, or TLV-E format repeats in a message with the unspecified repetition of the IE, then the SMF handles only the contents of the information element that appears first. In addition, SMF ignores the subsequent repetitions of the information element.
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SMF considers any optional IE with incorrect syntax in a message as an unavailable message.
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The network ignores any of the following messages and returns a status message with cause #100 "conditional IE error":
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When SMF receives a NAS message with a missing conditional IE error
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When SMF receives an unexpected conditional IE error
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When SMF receives a message with at least one syntactically incorrect conditional IE
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