Various services require the ability to return a collection of track identifiers. This is achieved using an IdArray.
An IdArray represents an array of big endian 32-bit unsigned integers. For example,
0x00 0x00 0x00 0x02 0x00 0x00 0x01 0x03 0x00 0x00 0x00 0x13
represents 3 tracks with the id's 2, 259, and 19 in that order.
Since UPnP has no native collection types, an IdArray has binary type in UPnP services.