This object specifies which kinds of speed mode can be negotiated.
Each bit corresponds to a kind of speed mode.
If the value of a bit is '1', it means the corresponding speed mode
is negotiable on the port. Otherwise the negotiation for that
kind of speed mode is not supported on this port. If there are
several negotiable speed modes, all bits for them are '1'.
For example, if the speed mode 's10M' and 's1000M' can be negotiable,
the value of this object is 0xA0.