Situation: In section 10.8.3.5, the standard says that a message with a higher protocol version and an unknown attribute type should be discarded. The parser should proceed to the next message in the MRPDU. However, the FirstValue length is not encoded in the PDU itself as indicated in section 10.8.1.2. The length of FirstValue is provided by the application itself based on the attribute type (ie MMRP knows that MAC addresses are 6 bytes long). In this case, if the application does not recognize the attribute type because it was introduced in a new version of the application, it has no basis to know the length of the FirstValue. Without the length of FirstValue, the parser has no reliable way to skip past this message and proceed with parsing the next message as required by section 10.8.3.5. Should the parser just discard the message with the unknown attribute type and all subsequent messages even though it contradicts 10.8.3.5?
This is an error in the PDU specification. There should be a length field in the structure. The definition of Message should be: Message ::= AttributeType, AttributeLength, AttributeList and the definition of AttributeLength should be: AttributeLength BYTE ::= <<Defined by the specific MRP application>> 802.1 has raised a PAR for a corrigendum to correct the error. This response was approved by 802.1 at its July 2007 plenary meeting.
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