Document: draft-ietf-ospf-manet-mdr-03.txt
Reviewer: Spencer Dawkins
Review Date: 2008-12-12
IETF LC End Date: 2008-12-24
IESG Telechat date: (not known)

Summary: This draft is on the right track for publication as Experimental. I have a small number of questions, listed below.

Comments:

2.6.  Hello Protocol

   Differential Hellos are sent every HelloInterval seconds, except when
   full Hellos are sent, which happens once every 2HopRefresh Hellos.

Spencer (clarity): Is 2HopRefresh a counter? As I continue reading, it seems to be treated as a counter, but that wasn't clear to me at this point in the document (I think I caught up in Section 4.1, but that's later than I'd
hoped)

   The default value of 2HopRefresh is 1, i.e., the default is to send
   only full Hellos.  The default value for HelloInterval is 2 seconds.
   Differential Hellos are used to reduce overhead and to allow Hellos
   to be sent more frequently, for faster reaction to topology changes.

3.2.  New Configurable Interface Parameters

   All possible configurations of the new interface parameters are
   functional, except that if AdjConnectivity is 0 (full-topology
   adjacencies), then LSAFullness must be 1, 2, or 4 (see Section 9.3).
   Differential Hellos should be used to reduce the size of Hello
   packets when the average number of neighbors is large.  Differential

Spencer (clarity): does "large" have any relationship with "160" or "200"
nodes mentioned in the next paragraph?

   Hellos are obtained by setting the parameter 2HopRefresh to an
   integer greater than 1, with the recommended value being 3.  Good
   performance in simulated mobile networks with up to 160 nodes has
   been obtained using the default configuration with differential
   Hellos.  Good performance in simulated mobile networks with up to 200
   nodes has been obtained using the same configuration except with
   minimal LSAs (LSAFullness = 0).  Simulation results are presented in
   Appendix E.

   MDRConstraint
      A parameter of the MDR selection algorithm, which affects the
      number of MDRs selected.  The default value of 3 results in nearly
      the minimum number of MDRs.  The optional value 2 results in a
      larger number of MDRs.

Spencer(clarity): are "3" and "2" the only possible values for this parameter? If so, that's fine, but the chosen values made me wonder about other possible values...

12.  IANA Considerations

   This document defines three new LLS TLV types to be allocated by
   IANA: MDR-Hello TLV, MDR-Metric TLV, and MDR-DD TLV.

Spencer (clarity): it would be good to point to the definitions in this section.

D.  Non-Ackable LSAs for Periodic Flooding

   In a highly mobile network, it is possible that a router almost
   always originates a new router-LSA every MinLSInterval seconds.  In
   this case, it should not be necessary to send Acks for such an LSA,
   or to retransmit such an LSA as a unicast, or to describe such an LSA
   in a DD packet.  In this case, the originator of an LSA MAY indicate
   that the router-LSA is "non-ackable" by setting a bit (to be
   specified) in the options field of the LSA.  For example, a router

Spencer: "to be specified"? Is this the L bit described in A.1?

   can originate non-ackable LSAs if it determines (e.g., based on an
   exponential moving average) that a new LSA is originated every
   MinLSInterval seconds at least 90 percent of the time. (Simulations
   can be used to determine the best threshold.)