next hop
Click on the red underlined text to get to the source
... source route, with the outermost element
being stripped off and used to decide the next hop. The innermost,
empty "tunnel" element ...
... session, and the stripped (inner) element is sent to start the next
hop. In this case, the peer is considered a "proxy" (meaning that
the next paragraph is applicable).
...
...
550 Requested action not taken
(E.g., next hop could be contacted, but
malformed greeting or no TUNNEL profile advertised.)
...