The specific packet string representing the destination address, source address, type/length field and a window of 64 bytes of packet data beginning at DataOffset to be used for filtering decisions. Each ASCII character of the string represents a nibble of packet data, therefore the packet string should be (14+64) * 2 = 156 characters long. A value of 'x' in the packet string is used to indicate a 'Don't care' and no filtering is to be performed on that nibble. The string may be be of size 0 to 78 bytes. If a size less than 78 bytes is used, the string will still begin at the destination address.