Defines the Downstream channel index on which the DEPI Session is being set. The set of this object is optional. When this object is not specified the M-CMTS is expected to generate an internal value with its corresponding ifStackTable dependencies at the time or making this entry active. When setting this value to a non-zero value, this object and docsIfMCmtsDepiSessionConfigCableMacIfIndex MUST correspond to a valid Cable and MCmtsDownstream interfaces pair from the ifStackTable. A set to an ifIndex corresponding to an ifType 128 (docsCableDownstream Interface) won't allow to turn the entry active.