-If the field is set to a particular node destination, it will
-be routed (rather than broadcast) to that node. However, any
-intervening nodes are free to duplicate the message and send
-it down more than one, likely looking, interface - depending on any
-network policies that may pertain.
-
-=item B<ToUser>
-
-This field is optional. It is a string of up to 12 characters
-in the set [-A-Z0-9_] in any order. Higher layers may restrict
-this further.
-
-Conventionally this field is used to indicate the user to whom
-this message is directed. In an ideal world the L</To> field
-will be set, by the originating node, to the identifier of the node
-on which this user resides.
-
-If the L</To> field is not set then this message will be
-broadcast. However, should a node become apparent (on route)
-then nodes are free to fill in the L</To> field and proceed
-with a more directed approach.
-
-If it becomes apparent (on route) that there may be more than
-one possible L</To> destination for a L</ToUser> then a node
-may duplicate the message (keeping the same L</TimeSeq>) and
-route it onwards. Because of the L</DeDuplication> inherent in
-the system, it is indeterminate as to which destination will
-receive the message. It is possible for all or just some
-destinations to receive the message. The tuple (L</Origin>,
-L</TimeSeq>) will determine uniqueness.
-
-This field can, in the case where L</To>
-is set to the name of a node, be set to a L</Channel>. If this
-is the case then this will cause this message to be sent to
-a L</Channel> on the L</To> node only.