This INTEGER selects how an STM-64 (10 Gb/s SDH) client port's client packets are mapped into the ODUk payload - options include GMP, GFP-F, several bit-synchronous mapping (BMP) variants, preamble mapping, or AMP - defaulting to not-applicable until a specific mapping is provisioned. An administrator sets this to match the mapping scheme required by the client signal type and the far-end equipment, since a mismatched mapping mode prevents the client signal from being correctly recovered at the far end. For example, provisioning STM-64 with the GFP-F mapping mode suits a packet-oriented client signal, whereas a fixed-rate signal would instead use one of the bit-synchronous mapping (BMP) options.