Cat5e is only rated to 100 MHz, and used with signaling rates of 125 MS/s in fast and gigabit ethernet. For a 3 meter run it will probably work fine at 200 MHz -- the loss is just too high for long runs like ethernet is expected to work over (typically 100 meters). Cat 6 works for 250 MHz, Cat6a is rated for up to 500 MHz. Cat 5 and 6 are normally unshielded, but also available shielded. Cat 6a is always shielded.