public void Extract(byte[] arr)
{
pcp = (byte)BitHelper.ExtractBits(arr, offset * 8, 3);
cfi = BitHelper.ExtractBit(arr, offset * 8 + 3);
vid = BitHelper.ExtractBits(arr, offset * 8 + 4, 12);
ethertype = BitHelper.Extract16(arr, offset + 2);
}