9 Handling of unknown, unforeseen, and erroneous protocol data

24.3343GPPProximity-services (ProSe) User Equipment (UE) to ProSe function protocol aspectsRelease 17Stage 3TS

9.1 General

The procedures specified in the present document apply to those PC3 or PC5 messages which pass the checks described in this subclause.

This subclause 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.

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 subclause 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.

9.2 Handling of unknown, unforeseen, and erroneous protocol data in messages sent over the PC5 interface

9.2.1 Message too short

When a message is received that is too short to contain a complete message type parameter, that message shall be ignored.

9.2.2 Unknown or unforeseen message type

If the UE receives a PC5_DISCOVERY message with Message Type not defined as in subclause 12.2.2.10, it shall discard the whole PC5_DISCOVERY message.

If the UE receives a PC5_DISCOVERY message with Message Type indicating a discovery model or discovery type that is not supported by the UE, it shall discard the whole PC5_DISCOVERY message.

9.3 Handling of unknown, unforeseen, and erroneous protocol data in messages sent over the PC3 interface

9.3.1 Invalid XML

The protocol data over PC3 interface are encapsulated as XML contents, which may contain one or more PC3 messages. The XML content shall be validated with the XML schema defined in subclause 11.2.3.

When the UE receives an invalid XML content, it shall discard the whole XML content. When the ProSe Function receives an invalid XML content, it shall discard the whole XML document and send an HTTP response message containing a "400 Bad Request" error code to the UE.

9.3.2 Unforeseen message type

If the UE receives a PC3 message with a message type corresponding to a ProSe discovery mechanism that the UE is not authorised to use by the network, the UE shall discard the message. For example, if a UE not authorised for EPC-level ProSe discovery receives messages specified for EPC-level ProSe discovery procedures in subclause 7, the UE shall discard the message.

If the ProSe Function receives a PC3 message whose message type indicates that this is a ProSe discovery mechanism the sending UE is not authorised to support, the ProSe Function shall discard the message.