The module type of the port connector. This object refers
to the hardware implementation of the port. It will be
'embedded' if the hardware equivalent to Gigabit interface
card (GBIC) is part of the line card and is unremovable. It
will be 'glm' if it's a gigabit link module (GLM). It will
be 'gbicSerialId' if the GBIC serial id can be read, else it
will be 'gbicNoSerialId'. It will be 'sfpSerialId', if the
small form factor (SFP) pluggable GBICs serial id can be
read, else it will be 'sfpNoSerialId'.