This object identifies the type of interface. The value of this attribute will affect the behavior of the OTM with respect to presence/absence of OTM Overhead Signal (OOS) processing and TCM activation. For an IrDI interface, there is no OOS processing and TCM activation is limited to n levels as specified by a TCM level threshold. This object contains two fields that are separated by whitespace. The possible values are: field 1: one of the 4-character ASCII strings 'IrDI' or 'IaDI' field 2: free-form text consisting of printable UTF-8 encoded characters Note that field 2 is optional. If it is not present then there is no requirement for trailing whitespace after field 1. The default values are as follows: field 1: 'IaDI' field 2: an empty string.