36.5.3.6.1 ‘1’ in the Header

After the read, the header may contain one or more ‘1’s. If the ‘1’s match the ‘1’s to write in the header, the packet can be written.

If the ‘1’s do not all match the ‘1’s to write in the header, the packet cannot be written. It is mandatory to create (and then invalidate if necessary) a packet with a compatible header.