Extended the text in Section 4.3.1 to explain the different significance of the
RAO and NSLPID values in a Q-mode message. (4.3.4 itself is not changed.)
Revised text in 4.3.1:

   Several different RAO values may be used by the NSIS protocol suite.
   GIST itself does not allocate any RAO values (for either IPv4 or
   IPv6); an assignment is made for each NSLP using MRMs that use the
   RAO in the Q-mode encapsulation.  The assignment rationale is
   discussed in [15].  The RAO value assigned for an NSLPID may be
   different for IPv4 and IPv6.  Note the different significance between
   the RAO and the NSLPID values: the meaning of a message (which
   signalling application it refers to, whether it should be processed
   at a node) is determined only from the NSLPID; the role of the RAO
   value is simply to allow nodes to pre-filter which IP datagrams are
   analysed to see if they might be Q-mode GIST messages.