Updated the text on MA-Hold-Time setting as follows (added the closing sentence):

   o  whether the peer still wants the MA in place.  During MA setup,
      each node indicates its own MA-Hold-Time as part of the Stack-
      Configuration-Data.  A node MUST NOT tear down the MA if it has
      received traffic from its peer over that period.  A peer which has
      generated no traffic but still wants the MA retained may use a
      special null message (MA-Hello) to indicate the fact.  A default
      value for MA-Hold-Time of 30 seconds is RECOMMENDED.  Nodes MAY
      use shorter times to achieve more rapid peer failure detection,
      but need to take into account the load on the network created by
      the MA-Hello messages.  Nodes MAY use longer times, but need to
      take into account the cost of retaining idle MAs for extended
      periods.  Nodes MAY take signalling application behaviour (e.g.
      NSLP refresh times) into account in choosing an appropriate value.

The MA-Hold-Time setting could usefully take into account aspects of NSLP
behaviour; for example, if the NSLP refresh time is 31 seconds, an MA-Hold-Time
of 29 seconds would be suboptimal.

Note that this is only an advisory issue; there could be several NSLPs using an
MA, and NSLP behaviour is only one criterion to take into account. Note also
that we haven't extended the GIST API explicitly to cover this sort of policy
configuration between layers.