Many devices require fixed length arrays and will fail if the number of elements in an array is different than specified. This is true for all data, including arguments to method calls.

The current spec defines array lengths as either variable size or maximum size but does not describe an array that is fixed length. This creates interoperability problems because a variable size array with fewer elements than the max will work with some devices but not others.

The spec needs to add metadata that addresses this, so that a client can determine if the arrays supplied to the server are fixed length vs maximum length. This applies to all types and fields in structured types, including arguments to method calls.

A new error code is needed that explicitly informs the client that a fixed length array is required when the writer supplies an array with fewer elements than is required.