frame

frame=48 bits or 6 bytes

most significant  byte                                   least significant byte
6th byte   5th byte  4th byte  | 3rd byte   2nd byte   1st byte
1st octet
oui first 3                                    vendor assigned second 3 bytes

the left most bit, however is the least significant bit in the byte, and the rightmost bit in the first byte is the most significant bit... if the leftmost bit of the most significant byte is 0, the address is unicast... if it is 1, it is multicast... this wiki is a must read... http://en.wikipedia.org/wiki/MAC_address

thank the IEEE...